TW201622217A - Resin composition for secondary battery negative electrode, production method of carbon material for secondary battery negative electrode, carbon material for secondary battery negative electrode, modified phenolic group-containing resin for secondary ba - Google Patents

Abstract

The present invention provides a resin composition for a secondary battery negative electrode including a phenolic hydroxyl group-containing resin whose hydroxyl equivalent is a predetermined value or less. In one embodiment of the present invention, the resin composition for a secondary battery negative electrode includes a phenolic hydroxyl group-containing resin whose hydroxyl equivalent is 300 g/eq or less, and a phosphoric acid ester or a phosphoric acid derivative whose boiling point temperature or thermal decomposition temperature exceeds a self-condensation temperature of said phenolic hydroxyl group-containing resin.

Description

Resin composition for secondary battery negative electrode, method for producing carbon material for secondary battery negative electrode, carbon material for secondary battery negative electrode, resin containing modified phenolic hydroxyl group for secondary battery negative electrode, active material for secondary battery negative electrode Secondary battery negative electrode and secondary battery

The present invention relates to a resin composition for a secondary battery negative electrode, a method for producing a carbon material for a secondary battery negative electrode, a carbon material for a secondary battery negative electrode, and a resin containing a modified phenolic hydroxyl group for a secondary battery negative electrode, An active material for a battery negative electrode, a secondary battery negative electrode, and a secondary battery.

This application is based on the special request 2014-176596, which was filed in Japan on August 29, 2014, and the special offer of 2014-176597, which was filed in Japan on August 29, 2014, and the application in Japan on August 29, 2014. I am willing to apply for the purpose of the 2015- 176 598, the special offer of 2015-039364, which was filed in Japan on February 27, 2015, and the 2015-039365, which was filed in Japan on February 27, 2015. Special offer 2015-039366, which was filed in Japan on February 27, 2015, and the special offer 2015-100463, which was filed in Japan on May 15, 2015, and the special offer of 2015 in Japan on May 15, 2015. Priority is claimed on Japanese Patent Application No. 2015-100465, the entire disclosure of which is hereby incorporated by reference.

In recent years, the use of secondary batteries has been studied in various technical fields such as small-sized electrical products such as mobile phones and even large-scale mechanical products such as automobiles. As the secondary battery, various types such as a nonaqueous electrolyte secondary battery using an organic electrolyte or the like as an electrolyte or a solid battery using a solid electrolyte as an electrolyte are being studied. In any of the secondary batteries, the chemical species (for example, lithium ions) which are the charge carriers of the secondary battery are repeatedly charged in the electrode active material layer of the positive electrode and the electrode active material layer of the negative electrode. And discharge.

In the secondary battery, the electrode active material layer provided in the negative electrode contains a carbon material as an electrode active material. The electrode active material layer occludes a chemical species between the layers of the carbon material having a layer structure, and releases the occluded chemical species or active material from the layer, thereby achieving charging and discharging of the secondary battery.

As the above carbon material, petroleum was originally used as a starting material. For example, Patent Document 1 discloses a negative electrode for a lithium secondary battery including a negative electrode active material (hereinafter also referred to as a conventional technique 1) including graphite and amorphous carbon containing phosphorus, oxygen, and unavoidable impurities. Specifically, the prior art 1 describes a case where a negative electrode active material component is formed by adding a phosphorus-containing compound to a raw petroleum coke by heating at 500 to 1500 ° C to form an amorphous carbon. And add graphite to mix it. As described in Patent Document 1, the In the conventional technique of amorphous carbon, the active material for a negative electrode obtained by mixing graphite is high in charge and discharge effects.

As described in Patent Document 1, the reason why phosphorus is contained in the negative electrode active material component is to increase the storage amount of lithium ions. Patent Document 1 presumes that by adding a phosphorus which is easily negatively charged to the negative electrode active material component, a large number of donor sites are formed in the coke, and these become the adsorption sites of lithium ions. Specific examples of phosphorus in the same literature include phosphorus pentoxide, phosphoric acid, and phosphate.

On the other hand, there have been a number of studies on carbon materials which are different from the above-mentioned conventional technique 1 and which use materials other than petroleum as a starting material. For example, Patent Document 2 discloses a negative electrode for a battery obtained by carbonizing an organic material and containing a carbonaceous material having a specific amount of phosphorus (hereinafter also referred to as a conventional technique 2). In the same document, a phenol resin is exemplified as an organic material which is a starting material in the prior art 2.

Specifically, in the second embodiment of the same document, a phosphoric acid aqueous solution or the like is added to the novolak-type phenol resin powder and calcined to form a carbonaceous material containing phosphorus, thereby producing a conventional technique 2 .

Similarly to Patent Document 1, Patent Document 2 also discloses that the prior art 2 contains phosphorus, which is very effective in increasing the doping amount of the carbonaceous material with respect to lithium. Further, Patent Document 3 will be described below.

[Previous Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. Hei 10-241690

[Patent Document 2] Japanese Patent Laid-Open No. 3-137010

[Patent Document 3] Japanese Patent Laid-Open No. Hei 10-223226

The phenol resin is a synthetic material that can be used as a starting material for a carbon material in a negative electrode, and can be used as a starting material for a carbon material in a negative electrode.

In the phenol resin, the inventors of the present invention have studied the use of a phenol resin which is simplified in molecular structure represented by a novolac type phenol resin and which is easily synthesized, as a starting material for forming a carbon material for a negative electrode of a secondary battery.

According to the study by the inventors of the present invention, it has been found that there is room for improvement in the charge capacity and charge and discharge efficiency of a carbon material produced by using a phenol resin having a simplified molecular structure and a small hydroxyl equivalent. The above-mentioned problem is not only a problem of a phenol resin, but also a problem common to a resin containing a phenolic hydroxyl group including a m-cresol resin or a naphthol resin.

The present invention has been made in view of the above problems. In other words, the present invention provides a secondary battery containing the phenolic hydroxyl group-containing resin, in which a phenolic hydroxyl group-containing resin having a hydroxyl equivalent of a specific value or less can be advantageously used as a starting material for a carbon material for a secondary battery negative electrode. A resin composition for a negative electrode (hereinafter also referred to simply as a resin composition).

Moreover, the present invention provides a method for producing a carbon material for a secondary battery negative electrode using the above resin composition (hereinafter also referred to simply as a method for producing a carbon material).

Moreover, the present invention provides a carbon material for a secondary battery negative electrode (hereinafter also simply referred to as a carbon material) produced by using the above resin composition.

Moreover, the present invention provides a secondary battery negative electrode active material produced by using the secondary battery negative electrode carbon material, a secondary battery negative electrode comprising the secondary battery negative electrode active material, and a secondary battery negative electrode Secondary battery.

Moreover, the inventors of the present invention have conducted intensive studies in order to utilize a phenol resin as a starting material of a carbon material for a secondary battery negative electrode. As a result, it has been found that the novolac type phenol resin used in the prior art 2 is easy to synthesize although its molecular structure is simplified, but it is difficult to exhibit sufficient battery performance by using the carbon material produced as a starting material. More specifically, it is known that the charge and discharge efficiency of the negative electrode including the electrode active material layer containing the carbonaceous material of the carbonaceous varnish type phenol resin as a starting material and formed by a conventional method is not sufficient.

The present invention has been made in view of the above problems. That is, an object of the present invention is to provide a resin containing a modified phenolic hydroxyl group which is useful for improving the charge and discharge efficiency of a secondary battery negative electrode.

More specifically, the present invention has been made in view of the above problems, and provides a resin containing a modified phenolic hydroxyl group for a secondary battery negative electrode of a secondary battery negative electrode carbon material capable of improving charge and discharge efficiency.

Moreover, the present invention provides a carbon material for a secondary battery negative electrode produced using the above-described resin containing a modified phenolic hydroxyl group.

Moreover, the present invention provides a secondary battery negative electrode active material containing the carbon material, a secondary battery negative electrode including a secondary battery negative electrode active material layer containing the negative electrode active material, and a secondary battery including the negative electrode.

In addition, as a result of the research conducted by the inventors of the present invention, it has been confirmed that the carbon material contained in the active material for the secondary battery negative electrode contains phosphorus, and the lithium ion occlusion of the carbon material is confirmed. The tendency to increase the amount. The increase in the amount of lithium ion absorption causes the capacitance of the negative electrode It is better in terms of enlargement.

However, in order to surely improve the battery performance of the secondary battery of the secondary battery, it is not sufficient to increase the storage amount of lithium ions, and it is necessary to increase the storage amount of lithium ions and increase the release of the absorbed lithium ions. The amount released.

As far as the release of lithium ions is concerned, the prior art 2 has room for improvement.

In addition, in the same manner, it is described in Patent Document 1 that the use of graphite in combination with the prior art 1 produces an active material for a negative electrode, whereby the irreversible capacity of the active material for a negative electrode can be reduced. In other words, as described in Patent Document 1, an active material for a negative electrode is formed by containing graphite having an irreversible capacity of lithium ions lower than that of amorphous carbon, and can be used to lower the negative electrode of the secondary battery. The role of irreversible capacity.

However, the active material for a negative electrode in which the irreversible capacity of lithium ions is reduced by mixing graphite with the conventional technique 1 does not at all improve the irreversible capacity of the lithium ion of the prior art 1 itself. In order to improve the release amount of lithium ions, it is not preferable because graphite is contained in the active material for a negative electrode as an essential condition, and the degree of freedom in designing the active material for a negative electrode is limited. Therefore, there is still room for improvement in the prior art 1 from the viewpoint of the release of lithium in the prior art 1 (i.e., the decrease in the irreversible capacity of lithium ions).

The present invention has been made in view of the above problems. In other words, the present invention provides a carbon material for a secondary battery negative electrode in which both the storage amount and the release amount of a chemical species such as lithium ions are improved.

Moreover, the present invention provides a secondary battery negative electrode active material produced by using the secondary battery negative electrode carbon material, a secondary battery negative electrode comprising the secondary battery negative electrode active material, and a secondary battery negative electrode Secondary battery.

The resin composition for a negative electrode of a secondary battery according to an aspect of the present invention contains a phenolic hydroxyl group-containing resin having a hydroxyl group equivalent of 300 g/eq or less, and a self-condensation of a resin having a boiling point temperature or a thermal decomposition temperature exceeding the above phenolic hydroxyl group-containing resin. Temperature phosphate or phosphoric acid derivative.

Further, a method for producing a carbon material for a secondary battery negative electrode according to an aspect of the present invention is a method for producing a carbon material for a secondary battery negative electrode using a resin composition for a secondary battery negative electrode of the present invention, characterized in that: In the baking step, the resin composition for the secondary battery negative electrode is fired to form a carbon material precursor at a firing temperature of not higher than 1000 ° C at the time of firing, and the second baking step is performed at the time of firing. The firing condition of the temperature at which the maximum temperature is 1000 ° C or higher is performed by firing the carbon material precursor generated in the first baking step to produce a carbon material.

Further, the carbon material for a secondary battery negative electrode according to an aspect of the present invention is a carbon material for a secondary battery negative electrode produced by using the resin composition for a secondary battery negative electrode of the present invention, which is characterized in that it is contained in accordance with the number basis. The surface area per unit volume obtained by the particle size distribution is a carbon particle in a range of 10000 cm ^-1 or more and 16,000 cm ^-1 or less.

Moreover, the active material for a secondary battery negative electrode of the present invention (hereinafter also simply referred to as an active material for a negative electrode) is characterized by containing the carbon material for a secondary battery negative electrode of the present invention.

Further, the secondary battery negative electrode of the present invention (hereinafter also referred to simply as a negative electrode) is characterized in that it comprises a secondary battery negative electrode active material layer containing the secondary battery negative electrode active material of the present invention, and a secondary battery negative electrode laminated thereon. A current collector for the negative electrode of the active material layer is used.

Further, the secondary battery of the present invention is characterized by comprising the secondary battery negative electrode of the present invention, an electrolyte, and a secondary battery positive electrode.

Further, the resin containing a modified phenolic hydroxyl group for a negative electrode of a secondary battery according to an aspect of the present invention is characterized in that the hydroxyl equivalent is 115 g/eq or more.

Further, a carbon material for a secondary battery negative electrode according to an aspect of the present invention is characterized in that it is produced by using a modified phenolic hydroxyl group-containing resin for a secondary battery negative electrode of the present invention.

Further, a carbon material for a secondary battery negative electrode according to an aspect of the present invention (hereinafter also referred to simply as a carbon material) is characterized in that phosphorus is contained in a range of 0.3% by mass or more and 1.5% by mass or less with carbon as a main component. And the adsorption amount of carbon dioxide is less than 10 ml/g per unit weight.

According to the resin composition of the present invention, a phenolic hydroxyl group-containing resin having a hydroxyl equivalent of a specific value or less is used as a starting material for a carbon material for a secondary battery negative electrode, and a charging capacity and a charge and discharge efficiency are improved as compared with the prior art. The negative pole.

Moreover, according to the method for producing a carbon material of the present invention, a phenolic hydroxyl group-containing resin having a hydroxyl equivalent of a specific value or less can be used as a starting material to produce a carbon material having improved battery characteristics.

Further, the carbon material of the present invention can provide a negative electrode which is a negative electrode having improved charging capacity and charge and discharge efficiency as compared with the prior art, and which is suppressed even in a low temperature environment.

In the active material for a negative electrode of the present invention, the charge capacity and charge and discharge efficiency of the negative electrode including the same are improved as compared with the prior art. Further, by containing the carbon material of the present invention, the active material for a negative electrode of the present invention provides a negative electrode which is suppressed even if the electric resistance is increased even in a low temperature environment.

Therefore, the negative electrode of the present invention and the secondary battery including the same are excellent in charge capacity and charge and discharge efficiency in a normal temperature environment. Further, from the viewpoint of using the above carbon material, the negative electrode of the present invention and the secondary battery including the same can exhibit high battery performance even in a low temperature environment.

The modified phenolic hydroxyl group-containing resin of the present invention contributes to improving the charge and discharge efficiency of the secondary battery negative electrode. That is, a phenol resin which is simplified with a molecular structure such as a novolac type phenol resin In the case of using the modified phenolic hydroxyl group-containing resin of the present invention as a starting material, the charge and discharge efficiency of the negative electrode having the carbon material thus produced can be improved as compared with the case of the starting material.

Moreover, the carbon material of the present invention and the negative electrode active material containing the carbon material contribute to improvement in charge and discharge efficiency of the secondary battery negative electrode.

Therefore, the negative electrode of the present invention is excellent in charge and discharge efficiency, and the secondary battery of the present invention including the negative electrode exhibits excellent battery performance.

The carbon material of one aspect of the present invention has a specific amount of phosphorus, and the adsorption amount of carbon dioxide is below a specific range, and the amount and amount of absorption of chemical species such as lithium ions are improved.

Moreover, the active material for a negative electrode containing the carbon material of the present invention can improve the charging capacity and the charge and discharge efficiency of the negative electrode including the negative electrode.

Therefore, the negative electrode of the present invention is excellent in charge capacity and charge and discharge efficiency, and the secondary battery of the present invention including the negative electrode exhibits excellent battery performance.

10‧‧‧negative

12‧‧‧Negative active material layer

14‧‧‧Negative current collector

20‧‧‧ positive

22‧‧‧ positive active material layer

24‧‧‧ positive current collector

30‧‧‧Parts

40‧‧‧ electrolyte

100‧‧‧Lithium ion secondary battery

1 is a schematic view showing an example of a lithium ion secondary battery containing a carbon material produced by using the resin composition of the present invention, and is a schematic view of a lithium ion secondary battery as an example of the secondary battery of the present invention. A schematic diagram showing an example of a lithium ion secondary battery including a negative electrode produced by using the carbon material of the present invention.

First, the first aspect of the present invention will be described.

In the phenolic hydroxyl group-containing resin, a phenolic hydroxyl group-containing resin represented by a novolac type phenol resin or a naphthol resin, which is represented by a phenolic hydroxy group-containing resin, is preferably used as a carbon material for forming a negative electrode for a secondary battery. Starting material. The resin having a phenolic hydroxyl group having a simple molecular structure means a resin having a phenolic hydroxyl group having a small hydroxyl group as a whole, and specifically, a hydroxyl group equivalent of 300 g/eq or less.

When a carbon material for a secondary battery negative electrode (hereinafter also referred to simply as a carbon material) is produced using a phenolic hydroxyl group-containing resin having a hydroxyl group equivalent of less than a specific value as described above, it has been difficult to obtain sufficient battery characteristics. The inventors of the present invention presume that the reason is as follows. That is, the inventors of the present invention presume that at least a part of the hydroxyl groups of the phenolic hydroxyl group-containing resin are dehydrated and condensed in the molecule and/or in the molecule in the firing step for carbonizing the phenolic hydroxyl group-containing resin. And cross-linking. It is considered that this crosslinking causes the growth of the crystal structure of the carbon material in the firing step to be hindered, and it is difficult to form crystallites of a preferred carbon containing a graphene-like structure. As a result, it is estimated that the sorption and release ability of the chemical species such as lithium ions of the carbon material is insufficient, and it is difficult to exhibit excellent charging capacity and charge and discharge efficiency. The term "microcrystalline" as used herein refers to the largest aggregate of single crystals.

On the other hand, the phenolic hydroxyl group-containing resin contained in the resin composition of the present invention has a hydroxyl equivalent of 300 g/eq or less and contains a phosphoric acid having a boiling temperature or a thermal decomposition temperature exceeding the self-condensation temperature of the phenolic hydroxyl group-containing resin. An ester or a phosphoric acid derivative (hereinafter also referred to as a phosphate ester or the like). Thereby, a carbon material excellent in charge capacity and charge and discharge efficiency can be provided.

By the fact that the resin composition of the present invention contains a phosphate having a boiling temperature or a thermal decomposition temperature exceeding the self-condensation temperature of a resin having a phenolic hydroxyl group, the reason why the battery characteristics of the carbon material produced by using the resin composition are improved is still unclear. However, it is speculated that the reason is as follows. In other words, the inventors of the present invention presume that when the resin composition of the present invention is fired for carbonization, The phenolic hydroxyl group resin starts from the point of time of condensation (that is, the hydroxyl group of the phenolic hydroxyl group-containing resin undergoes dehydration condensation and undergoes a crosslinking reaction in the molecule and/or between molecules), and there is no boiling in the reaction system. Or decomposed phosphate esters and the like. Therefore, the hydroxyl group of the phenolic hydroxyl group-containing resin is hydrogen-bonded or the like by a phosphate ester or the like, thereby shielding the hydroxyl group, thereby reducing the reactivity of the hydroxyl group, suppressing crosslinking caused by dehydration condensation, and thereby avoiding hindrance of carbon. The growth of the crystal structure. In the present invention, the term "self-condensation" means that the phenolic hydroxyl group of the resin having a phenolic hydroxyl group is subjected to dehydration condensation in the molecule and/or between molecules unless otherwise specified.

The inventors of the present invention used a carbon material produced by using a resin composition sample 1 containing a novolac type phenol resin and a phosphorus source (specifically, a phosphate such as triphenyl phosphate) under X-ray diffraction. The crystal structure was measured, and as a result, it was confirmed that the existence of the graphene structure was remarkably exhibited in the vicinity of the diffraction angle of 25° (2 θ/deg CuK α). On the other hand, the resin composition sample 2 prepared in the same manner as the above-mentioned resin composition sample 1 except for the absence of the phosphorus source was subjected to X-ray diffraction in the same manner, and as a result, no observation was observed in the vicinity of the diffraction angle of 25°. The graphene structure of the resin composition sample 1 is remarkably present.

For example, the low molecular weight phosphorus compound described in Patent Document 1 or 2 usually has a boiling temperature and a thermal decomposition temperature lower than the self-condensation temperature of the phenol resin. Therefore, in the case where the resin composition containing a phenol resin and a phosphorus compound having a low molecular weight is baked for carbonization, the molecular structure of the phosphorus compound is decomposed at the time of self-condensation of the phenol resin, or at least a part thereof has disappeared. Therefore, in the resin composition containing a phenol resin and a phosphorus compound having a low molecular weight, the effect of crosslinking caused by dehydration condensation of the phenol resin hydroxyl group at the time of firing is not sufficiently suppressed.

Further, in the present specification, the term "graphene-like structure" means a structure having at least partially a structure having the same carbon hexagonal lattice structure as that exhibited in graphene or A sheet structure of a similar structure, or a laminate structure in which the sheet structure is laminated. Further, in the present specification, the electrode active material means a material which can occlude and release a chemical species which become a charge carrier. Examples of the above chemical species include an alkali metal ion secondary battery, and examples thereof include lithium ions and sodium ions.

<Resin composition for secondary battery negative electrode>

Hereinafter, the form of the resin composition for carrying out the present invention will be described in detail.

The resin composition for a secondary battery negative electrode according to the present embodiment contains a phenolic hydroxyl group-containing resin having a hydroxyl group equivalent of 300 g/eq or less, and a phosphoric acid having a boiling temperature or a pyrolysis temperature exceeding a self-condensation temperature of the phenolic hydroxyl group-containing resin. Ester or phosphoric acid derivative.

The charge capacity and charge and discharge efficiency of the carbon material produced by using the resin composition of the present embodiment are improved, and the battery characteristics are excellent. By improving the charge capacity and the charge and discharge efficiency, the battery characteristics of the carbon material produced by using the resin composition of the present embodiment can be substantially improved.

According to the above configuration, at least one of the phenomenon of boiling of the phosphate ester or the phenomenon of thermal decomposition can be suppressed before the self-condensation of the phenolic hydroxyl group-containing resin. In the present embodiment, it is more preferred to use a phosphate or a phosphoric acid derivative having a boiling temperature and a thermal decomposition temperature exceeding the self-condensation temperature of a resin having a phenolic hydroxyl group.

In the present embodiment, the phenolic hydroxyl group-containing resin means a resin having a phenolic hydroxyl group in the molecule. The phenolic hydroxyl group-containing resin in the present embodiment comprises a resin synthesized by using a phenol such as a novolac type phenol resin or a resol-type phenolic resin as a starting material; using a m-cresol resin, a phenol-based resin other than a phenol such as a xylenol resin or a naphthol resin; a phenolic hydroxyl group in a molecule obtained by synthesizing a monomer other than a phenol and an aldehyde such as formaldehyde in the presence of an acid or a basic catalyst Resin; or a modifier containing the above resin A resin containing a modified phenolic hydroxyl group.

For example, the above phenolic hydroxyl group-containing compound can be synthesized by reacting a phenol with any reactive compound.

In the present specification, the novolac type phenol resin means a phenol resin synthesized by reacting the above phenols with formaldehyde under an acid catalyst. Further, in the present specification, the resol type phenol resin means a phenol resin synthesized by reacting the above phenol with formaldehyde under a base catalyst.

The catalyst may be used as needed in the synthesis of the phenolic hydroxyl group-containing resin.

The term "phenol" as used herein means an organic compound having a hydroxyl group in an aromatic compound, and contains not only a so-called phenol but also an organic compound having a cresol equal to a functional group other than a hydroxyl group on the benzene ring. The above-mentioned reaction compound contains not only formaldehyde but also a modifier compound which can synthesize a resin containing a modified phenolic hydroxyl group.

Specific examples of the phenols include, but are not limited to, phenol; o-cresol, m-cresol, p-cresol, xylenol, or an alkyl group such as p-tert-butylphenol. Phenols; aromatic substituted phenols such as p-phenylphenol; diphenols such as catechol or resorcin; naphthols such as α-naphthol or β-naphthol.

In the present embodiment, the hydroxyl equivalent means the molecular weight of the phenolic hydroxyl group-containing resin with respect to one hydroxyl group. The measurement of the hydroxyl equivalent can be carried out in accordance with the method specified in JIS K 0070 (1992) and the titration method.

In general, the smaller the hydroxyl group equivalent (for example, the hydroxyl equivalent is 200 g/eq or less, and further 150 g/eq or less, particularly 120 g/eq or less), the more preferable from the viewpoint of easiness of production and production cost, and it is expected to be two. The use of materials for the negative electrode of the secondary battery. Since the resin composition of the present invention contains such a phenolic hydroxyl group-containing resin having a small hydroxyl equivalent, it can be used substantially A starting material for providing a carbon material exhibiting excellent battery characteristics.

The phosphate ester or the like used in the present embodiment exhibits a boiling point temperature or a thermal decomposition temperature higher than the self-condensation temperature of the phenolic hydroxyl group-containing resin having a hydroxyl group equivalent of 300 g/eq or less.

Here, the self-condensation temperature of the phenolic hydroxyl group-containing resin means that when a resin containing a phenolic hydroxyl group is heated, any part of a plurality of hydroxyl groups contained in the phenolic hydroxyl group-containing resin is intramolecular and/or intermolecular. The temperature of the dehydration condensation refers to the temperature at which the phenolic hydroxyl group-containing resin is subjected to differential scanning calorimetry and exhibits an endothermic reaction at around 300 °C. For example, the self-condensation temperature of a dehydration condensation reaction including a hydroxyl group of a phenolic hydroxyl group-containing resin having a hydroxyl equivalent of a specific range or less represented by a novolac type phenol resin is about 300 ° C (for example, a range of 300 ° C or more and 350 ° C or less). ).

The phosphate ester in the present embodiment has a structure in which one or all of three hydrogens in phosphoric acid are partially or entirely substituted with an organic group, and the boiling point temperature or thermal decomposition temperature exceeds the self-condensation temperature of the phenolic hydroxyl group-containing resin contained in the resin composition. Organic phosphorus compound.

Examples of the phosphate esters include the compounds described below. However, the following examples are not intended to limit the invention.

Specific examples of the phosphate ester include triphenyl phosphate (for example, manufactured by Daiha Chemical Industry Co., Ltd., flame retardant, non-halogen phosphate, trade name: TPP), and cresyl diphenyl phosphate (for example, large). Manufactured by Ba Chemical Industry Co., Ltd., flame retardant, non-halogen phosphate, trade name: CDP), cresol bis(2,6-dimethylphenyl) ester (for example, manufactured by Daiba Chemical Industry Co., Ltd., flame retardant) A non-halogen phosphate ester, trade name: PX-110), a flame retardant manufactured by Daisaku Chemical Co., Ltd., a commercially available halogen-free phosphate ester, "product name: DAIGUARD-1000". The phosphate esters exemplified above are all phosphate triesters.

In addition, the phosphate ester may be a condensed phosphate ester, and, for example, a flame retardant "trade name: PX-200" manufactured by Daiba Chemical Industry Co., Ltd., which is a commercially available aromatic condensed phosphate ester, may be used.

The above cresyl diphenyl phosphate has a structure represented by the following chemical formula (2) and has a molecular weight of 340.

The above cresol bis(2,6-dimethylphenyl) phosphate has a structure represented by the following chemical formula (3), and has a molecular weight of 396.

The flame retardant "trade name: PX-200" manufactured by the Daiba Chemical Industry Co., Ltd. has a structure represented by the following chemical formula (1), and has a molecular weight of 816.

[(CH ₃ ) ₂ C ₆ H ₃ O] ₂ P(O)OC ₆ H ₄ OP(O)[OC ₆ H ₃ (CH ₃ ) ₂ ] ₂ (1)

In the present embodiment, the boiling point temperature (°C) of the phosphate ester or the like can be measured by a known method. In short, based on a phosphate ester or the like known as a boiling point temperature, a boiling point temperature of a phosphate having a molecular weight greater than that is estimated to be higher than the known boiling point temperature. For example, when the boiling temperature of triphenyl phosphate (molecular weight 326) is 399 ° C, it is presumed that the molecular weight is larger than the phosphate ester or the like which is a compound having a boiling temperature exceeding 399 ° C. Specifically, the above-mentioned chemical formulas of cresyl diphenyl phosphate, cresyl bis(2,6-dimethylphenyl) phosphate, and PX-200 have molecular weights greater than that of triphenyl phosphate, and the boiling points of the substances are presumed. The temperature exceeds 399 °C.

Further, in the present embodiment, the thermal decomposition temperature (°C) of the phosphate ester or the like can be measured at a temperature elevation rate of 10 ° C /min in an air atmosphere using a differential thermal thermal resynchronization measuring device, and the temperature is determined by a tangent method. / Weight change curve Find the temperature at which the weight begins to change. As the differential thermal resynchronization measuring device, for example, EI/DTA220 manufactured by Seiko Instruments Inc. can be used, but it is not limited thereto.

The phosphate ester of this embodiment is, for example, a phosphate triester.

Here, the triester phosphate means a structure in which three hydrogens of phosphoric acid are substituted with an organic group, and even a large molecular structure is represented in the phosphate. Therefore, it is considered that the steric hindrance between the hydroxyl groups of the resin having a phenolic hydroxyl group is easily formed, and the crosslinking between the hydroxyl groups can be favorably prevented.

In particular, as the phosphate triester, a triphenyl phosphate or a triphenyl phosphate derivative is preferably selected.

The reason is that the phenyl group contained in the phosphoric acid is introduced into a part of the carbon skeleton of the carbon material formed by using the phenolic hydroxyl group-containing resin as a starting material, and it is expected to contribute to the growth of the crystal structure of the carbon material. beneficial.

The triphenyl phosphate derivative refers to a compound in which any one or all of the three phenyl groups of triphenyl phosphate have a substituent.

For example, as the triphenyl phosphate derivative of the present embodiment, a compound represented by the following chemical formula (1) can be suitably used.

[(CH ₃ ) ₂ C ₆ H ₃ O] ₂ P(O)OC ₆ H ₄ OP(O)[OC ₆ H ₃ (CH ₃ ) ₂ ] ₂ (1)

The phosphoric acid derivative in the present embodiment includes a compound constituting any atom of phosphoric acid substituted with an arbitrary substituent, or a polyphosphoric acid which is a condensation reaction product of phosphoric acid. The polyphosphoric acid has a boiling point temperature of 550 ° C, which is a preferred phosphoric acid derivative in the present embodiment.

The amount of the phosphate ester or the like in the resin composition of the present embodiment is not particularly limited. For example, it is preferably 3 parts by mass or more and 15 parts by mass or less based on 100 parts by mass of the phenolic hydroxyl group-containing resin. The range contains a phosphate or a phosphoric acid derivative.

In the resin composition of the present embodiment, by blending the amount of the phosphate ester or the like to 3 parts by mass or more, the crosslinking of the hydroxyl group of the resin containing the phenolic hydroxyl group can be remarkably exhibited, and the use of the resin can be remarkably improved. The battery characteristics of the carbon material produced by the resin composition. From the above viewpoints, the blending amount of the phosphate ester or the like is more preferably 5 parts by mass or more, still more preferably 8 parts by mass or more.

In addition, by setting the phosphate ester or the like to 15 parts by mass or less, it is possible to ensure that the blending amount of the phenolic hydroxyl group-containing resin in the resin composition is sufficient for the formation of the carbon material.

The phosphate or phosphoric acid derivative used in the resin composition of the present embodiment is preferably one which has a self-condensation temperature at which the melting point of the resin having a phenolic hydroxyl group is not reached.

In the step of firing the resin composition to form a carbon material, the hydroxy group-containing resin hydroxy group can be dehydrated and condensed to start the crosslinking of the phosphate ester before the crosslinking starts, and the resin composition can be improved. The dispersibility of phosphates and the like. By dispersing the phosphate compound or the like in the resin composition, the phosphate ester or the like having a significantly lower content of the phenolic hydroxyl group-containing resin can be efficiently used to inhibit crosslinking of the hydroxyl group in the phenolic hydroxyl group-containing resin. The role.

In other words, it is possible to avoid the case where a phosphate or the like before melting is locally present in the resin composition at a temperature at which crosslinking is caused by dehydration condensation of a hydroxyl group of a phenolic hydroxyl group-containing resin.

For example, when the hydroxyl group of the novolac type phenol resin starts dehydration condensation at about 300 ° C, the melting point of the phosphate ester or the like is preferably less than 300 ° C. For example, from the above viewpoints, triphenyl phosphate having a melting point of 48.5 ° C or higher, an aromatic condensed ester of the above chemical formula (1) having a melting point of 92 ° C or higher, polyphosphoric acid having a melting point of about 200 ° C, or the like is preferably used.

In particular, in the resin composition of the present embodiment, it is preferred that the melting point of the phosphate ester or the phosphoric acid derivative and the melting point of the phenolic hydroxyl group-containing resin are both higher than normal temperature and 250 ° C or lower.

When the melting point of the phosphate ester or the like and the phenolic hydroxyl group-containing resin exceeds the normal temperature, the resin composition can be prepared by dry blending, and thus the handleability is easy.

In addition, when the melting point of the phosphate ester or the like and the phenolic hydroxyl group-containing resin are both 250 ° C or lower, the following effects can be exhibited. In other words, the phosphate ester or the like can be melted and mixed with the phenolic hydroxyl group-containing resin at a temperature sufficiently lower than the dehydration condensation of the hydroxyl group of the phenolic hydroxyl group-containing resin such as the novolac type phenol resin. Thereby, crosslinking due to dehydration condensation of the hydroxyl group of the phenolic hydroxyl group-containing resin can be favorably suppressed.

In the present embodiment, the melting point of the phosphate ester or the like and the melting point of the phenolic hydroxyl group-containing resin means the temperature of the peak top of the endothermic peak analyzed by the differential scanning calorimetry (hereinafter also referred to as DSC).

In the resin composition of the present embodiment, the phosphate ester or the like and the phenolic hydroxyl group-containing resin are preferably selected so that the melting start temperature of the phosphate or the phosphoric acid derivative does not reach the melting end temperature of the phenolic hydroxyl group-containing resin.

Thereby, the melting of the phosphate ester or the like can be started before the melting of the phenolic hydroxyl group-containing resin is completely completed, and the compatibility of the phenolic hydroxyl group-containing resin with the phosphate ester or the like can be improved. From this point of view, it is more preferable to select a phosphate ester having a melting initiation temperature lower than the melting point of the phenolic hydroxyl group-containing resin, and to prepare a resin composition using the phosphate esters.

In the present embodiment, the melting start temperature means the temperature at which the endothermic peak measured by DSC starts. Further, in the present embodiment, the melting end temperature means the temperature at which the endothermic peak measured by DSC ends.

As a specific example, the melting temperature range of the novolac type phenol resin is 70 °C to 100 °C. On the other hand, as the phosphate ester or the like in the present embodiment, a phosphate ester having a melting point onset temperature of less than 100 ° C is preferably selected. As such a phosphate ester, for example, triphenyl phosphate (trade name: TPP, melting point: 48.5 ° C or more) manufactured by Daisei Chemical Industry Co., Ltd., which is a commercial product, or Dabiao Chemical Industry Co., Ltd. The aromatic condensed phosphate ester (trade name: PX-200, melting point: 92 ° C or higher) is not limited thereto.

The resin composition of the present embodiment may further contain any additives as needed.

For example, the resin composition of the present embodiment may further contain a curing agent. The reason for this is that the hardener promotes thermal hardening of the phenolic hydroxyl group-containing resin.

The curing agent is not particularly limited, and may be appropriately determined in accordance with the combination of the phenolic hydroxyl group-containing resin to be used. For example, when the phenolic hydroxyl group-containing resin contained in the resin composition is a novolac type phenol resin, hexamethylenetetramine, a resol type phenol resin, or a polyacetal can be suitably used. In the case where the phenolic hydroxyl group-containing resin contained in the resin composition is a resol type phenol resin, hexamethylenetetramine or the like can be used.

The blending amount of the curing agent in the resin composition is not particularly limited, and is, for example, 0.1 parts by mass or more and 50 parts by mass or less based on 100 parts by mass of the phenolic hydroxyl group-containing resin.

In particular, when the novolak type phenol resin is used as the resin containing a phenolic hydroxyl group in the resin composition of the present embodiment, a curing agent may be further contained.

The novolac type phenol resin contained in the resin composition may be cured in the step of firing and carbonizing the resin composition without using a curing agent, but may not significantly inhibit the baking of the resin composition. The range in which the crystal structure of the produced carbon material grows contains a hardener.

Examples of the additives other than the curing agent include organic acids, inorganic acids, and A nitrogen-containing compound, an oxygen-containing compound, an aromatic compound, a non-ferrous metal element, or the like. These additives may be used singly or in combination of two or more kinds depending on the kind or properties of the resin to be used.

The phenolic hydroxyl group-containing resin, phosphate ester, and the like contained in the resin composition of the present embodiment and, if necessary, additives have been described. The method for preparing the resin composition of the present embodiment containing these materials is not particularly limited, and can be carried out by an appropriate method. For example, a method of (1) melting and mixing, (2) dissolving in a solvent and mixing, and (3) pulverizing and mixing may be carried out by a resin containing a phenolic hydroxyl group, a phosphate ester, or the like, and an additive to be appropriately added. Prepared by waiting.

In particular, when a resin having a phenolic hydroxyl group having a melting point exceeding a normal temperature and a phosphate ester or the like is used, the method of the above (3) (i.e., dry doping) can be used. The workability of the resin composition prepared by dry blending is easy and preferable. In particular, in the case where the melting point of the phosphate ester or the like and the phenolic hydroxyl group-containing resin exceeds the normal temperature and is 250 ° C or less, the resin composition prepared by dry blending may be burned without separately providing a step of melt-mixing. In the process of the steps, the two are well melted and mixed.

The apparatus for preparing the resin composition is not particularly limited. For example, in the case of performing melt mixing, a kneading device such as a kneading roll or a uniaxial or biaxial kneader can be used. In the case of performing melt mixing, a mixing device such as a Henschel mixer or a disperser can be used. In the case of pulverizing and mixing, for example, a device such as a hammer mill or a jet mill can be used.

The resin composition thus obtained may be obtained by physically mixing only a plurality of components, or may be converted into mechanical energy by mixing (stirring, kneading, etc.) in the preparation of the resin composition. Thermal energy makes a part of it chemically reacted. Specifically, a mechanochemical reaction caused by mechanical energy or a chemical reaction caused by thermal energy can also be performed.

<carbon material>

Next, the carbon material of the present invention will be described. The carbon material of the present invention described below is a carbon material produced by using the resin composition of the present invention, and the surface area per unit volume obtained by the particle size distribution on the basis of the number is 10000 cm ^-1 or more. Carbon particles in the range of 16,000 cm ^-1 or less. In the case where "cm ^-1 " is described in the present specification, the term "cm ² /cm ³ " is used unless otherwise specified. Further, in the following description, a carbon material containing preferred carbon particles may be simply referred to as a carbon material.

Further, the carbon material described below does not limit the resin composition of the present invention. The resin composition of the present invention can be suitably used for the production of a carbon material other than the carbon material of the present invention.

The lower limit of the surface area per unit volume described above may further be 12,000 cm ^-1 or more. Further, the upper limit of the surface area per unit volume may be 15500 cm ^-1 or less or 14,000 cm ^-1 or less.

Since the carbon material of the present invention is produced by using the resin composition of the present invention, the charging capacity and the charge and discharge efficiency are improved as compared with the prior art. In addition, since the carbon material of the present invention contains carbon particles having a surface area per unit volume in the above range, it has an effect of suppressing an increase in electric resistance during charge and discharge of the secondary battery in a low-temperature environment (hereinafter also referred to as a resistance suppression effect). . The reason why the electric resistance suppression effect is exhibited in the carbon material of the above aspect is not clear. However, the carbonaceous material of this aspect is moderately small in size, and is formed in such a manner that the surface area per unit volume becomes sufficiently large. Therefore, it is estimated that the lithium ion absorbing and releasing efficiency of the carbon material of this aspect is high, and even when the action of lithium ions becomes slow in a low temperature environment, the occlusion release can be smoothly performed. In other words, it is presumed that the carbon material of the aspect significantly increases the surface area of the particles as the occlusion release region of the lithium ion compared to the previous carbon material, thereby offsetting the decrease in the mobility of lithium ions in a low temperature environment. And suppressing resistance Increased.

Specifically, the carbon material has a surface area per unit volume of 10000 cm ^-1 or more, and the total area of the surface of the particles as the lithium ion storage release region is sufficiently large. As a result, the carbon material of the present invention is superior in occlusion and release ability of lithium ions as compared with the conventional carbon material, and exhibits a resistance suppression effect even in a low temperature environment.

Further, by setting the carbon material to a surface area per unit volume of 16,000 cm ^-1 or less, particles of extremely minute carbon materials can be eliminated. When the carbon material contains extremely small carbon material particles, the self-discharge amount tends to increase at a high temperature, and when the material containing the carbon material is slurried and applied to the current collector, the slurry is applied. The viscosity of the material rises remarkably and the coating property tends to decrease. From this point of view, the upper limit of the surface area per unit volume of the carbon material is preferably 16,000 cm ^-1 .

In the carbon material of the present invention, the electrical resistance in a low temperature environment can be judged based on the value of the direct current resistance (DC-IR) measured under a specific low temperature environment (for example, an environment of -20 ° C). When the DC resistance value is relatively large, the resistance is relatively high.

In the carbon material of the present invention, the particle size distribution under the reference number means the particle size distribution of the number basis determined by the laser diffraction/scattering method. The particle size distribution can be measured by a laser diffraction/scattering particle size distribution measuring apparatus. For example, it can be measured by LA-920 manufactured by Horiba, Ltd., and the like. The particle diameter herein means the diameter of the particles.

In the present invention, the surface area per unit volume obtained by the particle size distribution based on the number-based basis may be a particle diameter based on the number measured by an arbitrary laser diffraction/scattering particle size distribution measuring apparatus. The data obtained by the distribution is calculated by the following formula (1).

Surface area per unit volume (cm ^-1 ) = total surface area (cm ² ) / total volume (cm ³ ) (1)

Here, the "total surface area" is the sum of values obtained by converting the particles of the respective particle diameters in the particle size distribution into a true spherical shape multiplied by the frequency (%) of the particles of the respective particle diameters.

Further, the "total volume" is the sum of values obtained by multiplying the particles of the respective particle diameters in the particle size distribution into a true spherical shape by the frequency (%) of the particles of the respective particle diameters.

Moreover, the "frequency" is a ratio of particles of respective particle diameters to the total number of particles to be measured.

A method of obtaining a carbon material containing carbon particles having a surface area per unit volume of a preferred range specified in the present invention is not particularly limited, and as an example, a pulverization treatment is appropriately performed in the process of producing a carbon material. The details of the pulverization process will be described below.

The carbon material of the present invention preferably has a mean square radius (hereinafter also referred to as a mean square radius) obtained from the particle size distribution described above in a range of 1 μm ² or more and 4 μm ² or less.

In other words, the above-described mean square radius is 1 μm ² or more, and the particle diameter from the carbon particles contained in the carbon material is remarkably small, thereby preventing deterioration of self-discharge in a high-temperature environment, and maintaining the current collector well. Coating properties. Further, by the above-described mean square radius of 4 μm ² or less, it is easy to select carbon particles having a surface area per unit volume contained in the above preferred range.

From the viewpoint of a good solution of the present invention contemplated the problem, the mean square radius of the upper limit is more preferably ² to 3 m or less, and further preferably set to 2 m ² or less.

In the preferred aspect of the present invention, the mean square radius obtained from the particle size distribution can be obtained from the particle size distribution on the basis of the number. Specifically, the data obtained by the particle size distribution based on the number of measurements measured by an arbitrary laser diffraction/scattering particle size distribution measuring apparatus can be used and calculated by the following formula (2).

Mean square radius (μm ² ) = sum of squares of the radius of each particle (μm ² ) (2)

Here, the "sum of the square of the radius of each particle (μm ² )" is obtained by multiplying the squared value of each particle diameter in the particle diameter distribution as a radius, and multiplying the value obtained by squared by the particles of each particle diameter. The sum of the values obtained by the frequency (%).

One of preferred aspects of the carbon material of the present invention is that the carbon particles contained in the carbon material have a true specific gravity of 1.5 g/cm ³ or more and 1.7 g/cm ³ or less.

By selecting carbon particles having a true specific gravity of 1.5 g/cm ³ or more, the value of the charge and discharge capacity can be stabilized. Moreover, by selecting carbon particles having a true specific gravity of 1.7 g/cm ³ or less, it is possible to improve the life characteristics of the secondary battery using the carbon material of the present invention.

The above true specific gravity can be obtained by using a true specific gravity measuring method of butanol.

The method of adjusting the carbon particles contained in the carbon material of the present invention to have a true specific gravity in the above preferred range is not particularly limited. For example, the true specific gravity can be adjusted according to the selection of the carbon material or the heating condition of the carbon material. .

Hereinafter, the aspect in which the carbon particles in the carbon material of the present invention contain hard carbon will be described. For example, the carbon particles in the present invention preferably contain 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 95% by mass or more of the hard carbon described below.

That is, as one of the preferred aspects of the carbon material of the present invention, the carbon particles contained in the carbon material may contain (002) surface obtained by X-ray diffraction using CuK α ray as a radiation source. The average surface spacing d002 is hard carbon of 0.340 nm or more.

The hard carbon (non-graphitizable carbon) is a carbon material obtained by firing a polymer in which a graphite crystal structure is difficult to grow, and is an amorphous substance. In other words, the hard carbon is a carbon material having no graphene structure or carbon having only a graphene structure locally, and has the above-described specific average surface interval d002. When the average surface spacing d002 of the hard carbon is 0.340 nm or more, particularly 0.360 nm or more, it becomes less likely to cause shrinkage between layers due to absorption of lithium ions. The expansion is suppressed, so that the decrease in charge and discharge cycle property can be suppressed. The upper limit of the average surface interval d002 is not particularly limited, and may be, for example, 0.390 nm or less. When the average surface interval d002 is 0.390 nm or less, particularly 0.380 nm or less, the lithium ion occlusion release can be smoothly performed, and the decrease in charge and discharge efficiency can be suppressed.

Further, it is preferable that the hard carbon has a size Lc of crystallites in the c-axis direction (the (002) plane orthogonal direction) of 0.8 nm or more and 5 nm or less.

By setting Lc to 0.8 nm or more, particularly 0.9 nm or more, it is possible to form a space between carbon layers capable of occluding and releasing lithium ions, thereby obtaining a sufficient charge and discharge capacity, and is set to be 5 nm or less, especially 1.5. In the range of nm or less, it is possible to suppress the disintegration of the carbon laminate structure caused by the release of lithium ions or the reductive decomposition of the electrolyte, and to suppress the decrease in charge and discharge efficiency and charge and discharge cycle property.

Lc was calculated as follows.

The half value width and the diffraction angle of the 002 surface peak in the spectrum obtained by the X-ray diffraction measurement were determined using the following Scherrer formula.

Lc=0.94 λ/(βcos θ) (Scherrer formula)

Lc: the size of the crystallite

λ: characteristic of X-ray K α 1 from the cathode output

β: half value width of the peak (radian)

θ: the angle of reflection of the spectrum

The X-ray diffraction spectrum of hard carbon can be measured by an X-ray diffraction apparatus "XRD-7000" manufactured by Shimadzu Corporation. The method for measuring the above average surface interval of hard carbon is as follows.

The average surface spacing d can be calculated by the following Bragg formula according to the spectrum obtained by X-ray diffraction measurement of hard carbon.

λ=2dhklsin θ (Bragg formula) (dhkl=d002)

λ: characteristic of X-ray K α 1 from the cathode output

θ: the angle of reflection of the spectrum

The carbon particles as hard carbon have a property of releasing lithium ions on the entire surface thereof. Therefore, the carbon material of the carbon particles containing the hard carbon having a surface area per unit volume in the above range exhibits an effect of excellent lithium storage and release ability due to an increase in surface area. In other words, the carbon material of the present invention containing carbon particles as hard carbon sufficiently exhibits the action of the constitution of the present invention and exerts an excellent effect.

Further, in general, carbon particles as hard carbon have a problem that the diffusibility (mobility) of lithium ions in the particles is lower than that of carbon particles as graphite. On the other hand, the carbon particles as hard carbon contained in the carbon material of the present invention have a surface area per unit volume in the above preferred range, and the carbon particles are sufficiently atomized, so that the above-described diffusibility defects can be compensated for. From this point of view, in the present invention, the carbon particles as the hard carbon satisfy the above-mentioned preferable range by the surface area per unit volume, and the occluded release ability of lithium ions is remarkably improved.

The carbon particles in the present invention may contain 90% by mass or more of hard carbon from the viewpoint of the effect obtained by the hard carbon contained in the carbon particles as described above.

However, the carbon material of the present invention does not exclude the state containing graphite. Here, an allotrope of graphite-based carbon is a hexagonal crystal or hexagonal plate-like crystal which forms a layered lattice formed of a layer formed by a six-carbon ring. The above graphite has a so-called graphene structure. The above graphite contains natural graphite and artificial graphite.

Graphite has an ideal property of less change in voltage from the initial stage of discharge to the end of discharge, and can maintain a stable high voltage up to the end of discharge. The carbon particles contained in the carbon material of the present invention may be partially or entirely composed of graphite.

The carbon particles in the carbon material of the present invention may contain hard carbon and graphite from the viewpoint of utilizing the advantages of hard carbon and graphite and providing a well-balanced carbon material.

The aspect of the present invention containing both carbon and graphite as carbon particles is observed under the microscope, and the particles including the hard carbon particles and the graphite particles are separately observed, and the two are fused or bonded to each other in appearance. A situation in which the whole is observed.

The content ratio of hard carbon to graphite in the carbon material of the present invention is not particularly limited. However, from the viewpoint of containing a large amount of hard carbon per unit volume in a specific range to exert the above-described resistance suppression effect, the following ratio range is preferable. That is, in the carbon material of the present invention containing the hard carbon and graphite, the quality of both of the carbon materials is preferably hard carbon: graphite = 51% by mass: 49% by mass to 95% by mass: 5% by mass range.

The carbon material of the present invention described above may be substantially composed only of carbon particles, and may contain any other material. For example, the carbon material of the present invention contains 90% by mass or more of the carbon particles, and preferably contains 95% by mass or more.

In addition, the carbon material for a secondary battery negative electrode which is obtained by using the resin composition for a secondary battery negative electrode of the present invention is not only evaluated for the above-described low-temperature characteristics, but also excellent in a high-temperature environment. nature. In other words, the secondary battery including the negative electrode containing the carbon material for a secondary battery negative electrode of the present invention can exhibit an excellent discharge capacity of 85% or more in the evaluation of high-temperature storage characteristics. In addition, the secondary battery including the negative electrode containing the carbon material for a secondary battery negative electrode of the present invention can exhibit an excellent maintenance of 85% or more in the evaluation of high-temperature life characteristics. Different discharge capacity.

In other words, the carbon material for a secondary battery negative electrode used in the carbon material-based secondary battery negative electrode for a secondary battery negative electrode of the present invention preferably has a high-temperature storage characteristic of 85% or more as shown in the following evaluation of high-temperature storage characteristics. .

In the evaluation of the high-temperature storage characteristics in the present invention, a lithium ion secondary battery including a secondary battery negative electrode including a carbon material for a secondary battery negative electrode, a positive electrode, an electrolytic solution containing a dissolved electrolyte, and a separator is used.

Here, the secondary battery negative electrode including the carbon material for a secondary battery negative electrode means a secondary battery negative electrode containing a carbon material for a secondary battery negative electrode in the negative electrode active material. In addition, the positive electrode containing lithium cobalt oxide (LiCoO 2 ) means a secondary battery positive electrode containing lithium cobalt oxide in the positive electrode active material. This positive electrode was produced by using a single-layer sheet of aluminum foil (manufactured by Pionics Co., Ltd., trade name; Pioxcel C-100) to form a disk having a diameter of 12 mm as a current collector.

The above positive electrode is preferably a positive electrode containing lithium cobalt oxide (LiCoO ₂ ).

Specifically, the electrolyte solution is preferably prepared by dissolving lithium hexafluorophosphate in a mixture of ethyl carbonate and diethyl carbonate (volume ratio of 3:7) at a concentration of 1 mol/liter. .

The separator is preferably a porous film made of polypropylene.

The details of the high temperature storage characteristics in the present invention are as follows. In other words, the lithium ion secondary battery is subjected to an aging treatment for performing a specific charge and discharge cycle for five cycles, and the discharge capacity at the time of discharge in the fifth cycle of the charge and discharge cycle is measured to obtain a discharge capacity I. . Using the lithium ion secondary battery after the above aging treatment, the current density was set to 25 mA/g for constant current charging, and from the time point when the potential reached 4.2 V, the constant voltage was further maintained at 4.2 V, and the current density was reached. 2.5mA/g up, ready to charge state (State The lithium ion secondary battery adjusted to 100% by the SOC was stored in a dryer adjusted to a temperature of 60 ° C for one week in a lithium ion secondary battery having a state of charge of 100%. After the storage, the lithium ion secondary battery was used for charging and discharging at a current value of 0.2 C, and as a single cycle, a total of three cycles of charge and discharge were performed, and the discharge at the third cycle of discharge was measured. The capacity was set to the discharge capacity II, and the high-temperature storage characteristics were calculated according to the following formula (4).

High-temperature storage characteristics (%) = [discharge capacity II (mAh / g) / discharge capacity I (mAh / g)] × 100 (4)

Further, in the present invention, the specific charge and discharge cycle is performed by using the lithium ion secondary battery described above, and the measurement temperature is 25 ° C, and the current density at the time of charging is 25 mA / g, and the constant current is charged, and the self-potential reaches 4.2 V. At the time point, constant voltage charging was performed while maintaining 4.2 V, and charging was performed until the current density reached 2.5 mA/g. Then, the current density at the time of discharge was set to 25 mA/g, constant current discharge was performed, and discharge was performed until the potential reached 2.5 V. Take this as a loop. Further, charging and discharging were carried out under the same conditions, and charging and discharging for a total of five cycles were carried out. The discharge capacity (discharge capacity I) at the time of discharge in the fifth cycle of the above aging treatment was measured.

According to the evaluation of the high-temperature storage characteristics described above, the high-temperature storage characteristics of the carbon material for secondary battery negative electrodes for evaluation can be evaluated by unifying the conditions other than the carbon materials for the secondary battery negative electrode.

In the carbon material for a secondary battery negative electrode used for the secondary battery negative electrode for a secondary battery negative electrode of the present invention, it is preferable that the high-temperature life characteristic exhibited by the following high-temperature life characteristic evaluation is 85% or more.

The evaluation of the high-temperature life characteristics in the present invention is used in conjunction with the above-described evaluation of high-temperature storage characteristics. The lithium secondary battery is implemented in the same secondary battery.

The details of the high temperature life characteristics in the present invention are as follows. That is, an aging treatment for performing a specific charge and discharge cycle for 5 cycles is performed using the above-described lithium ion secondary battery. Then, the lithium ion secondary battery after the aging treatment described above was charged to 4.2 V at a constant current of 1 C in a temperature environment of 55 ° C, and then charged at a constant voltage of 4.2 V until the current value was attenuated to 0.02 C. The temperature was maintained at 55 ° C for 30 minutes, and then discharged to 2.5 V at a constant current of 1 C, and the discharge capacity was measured to be the discharge capacity III, and thereafter, the temperature was maintained at 55 ° C for 30 minutes. The charge and discharge cycle is used as one cycle. Then, the charge and discharge cycle was further carried out for 99 cycles, and a total of 100 cycles of charge and discharge cycles were performed, and the discharge capacity at the time of the discharge of the 100th cycle was measured to be the discharge capacity IV, according to the following formula (5). ) Calculate the high temperature life characteristics.

High-temperature life characteristics (%) = [discharge capacity IV (mAh / g) / discharge capacity III (mAh / g)] × 100 (5)

Further, since the specific charge and discharge cycle in the evaluation of the high-temperature life characteristics is the same as the specific charge-discharge cycle in the above-described evaluation of the high-temperature storage characteristics, it will not be described in detail here.

According to the evaluation of the high-temperature life characteristics described above, it is possible to evaluate the high-temperature life characteristics of the carbon material for secondary battery negative electrodes for evaluation by unifying the conditions other than the carbon material for the secondary battery negative electrode.

As described above, when the secondary battery using the carbon material for a negative electrode of the present invention is stored for a long period of time in a high-temperature environment of about 60 ° C, the discharge capacity before storage can be maintained at a high ratio.

Further, the secondary battery using the carbon material for a negative electrode of the present invention has a high temperature of about 55 ° C or so. When the environment is reused, the discharge capacity before repeated use in a high temperature environment can be maintained at a higher ratio.

Therefore, the carbon material for secondary batteries of the present invention can provide a secondary battery that can withstand storage or use in a high temperature environment.

<Method for Producing Carbon Material for Secondary Battery Negative Electrode>

Next, the aspect of the method for producing the carbon material for a secondary battery negative electrode of the present invention will be described in detail. The method for producing a carbon material according to the present invention is a method for producing a carbon material for a secondary battery negative electrode using the resin composition of the present invention described above.

The method for producing a carbon material according to the embodiment includes a first baking step and a second baking step.

The first firing step is a step of firing a resin composition for a secondary battery negative electrode to form a carbon material precursor at a firing temperature of less than 1000 ° C at the time of firing.

The second baking step is a step of firing a carbon material precursor generated in the first firing step by firing conditions at a temperature at which the highest temperature at the time of firing is 1000 ° C or higher, thereby producing a carbon material.

The first firing step and the second firing step may be carried out continuously or separately.

As an example of the aspect in which the first step and the second step are separately performed, for example, the carbon material precursor obtained by the first firing step may be pulverized between the first firing step and the second firing step. The comminution step. From the viewpoint of making the thermal history of the carbon material precursor in the second firing step uniform, it is preferred to carry out the above pulverization step. The particle diameter of the pulverized material of the carbon material precursor obtained in the pulverization step is not particularly limited, and is 1 μm or more and 20 μm or less, and more preferably 5 μm or more and 15 μm or less. When the particle diameter of the pulverized material is equal to or greater than the lower limit of the numerical value range, the pulverized material is rational, and the phosphorus contained in the phosphate ester or the like is remarkably retained in the final place. In the formation of carbon materials. Further, by making the particle diameter of the pulverized material equal to or less than the upper limit of the numerical value range, the heat history of the carbon material in the second baking step can be satisfactorily achieved.

The particle diameter of the above pulverized material means the particle diameter (D50, average particle diameter) at which 50% of the cumulative distribution of the volume basis is accumulated.

Further, by adjusting the pulverization conditions in the pulverization step, a carbon material containing carbon particles having a surface area per unit volume or a square radius of a preferred range can be produced.

The pulverization method in the above pulverization step is not particularly limited, and for example, any pulverization apparatus can be used. Examples of the pulverizing device include the following devices, but are not limited thereto: a pulverizing device such as a ball mill device, a vibrating ball mill device, a rod mill device, or a bead mill device; or a cyclone device or a jet mill device; Airflow pulverizing device such as dry airflow pulverizing device. In the pulverization treatment, the devices may be used one or two or more, or may be used by pulverizing a plurality of devices. Further, in the pulverization treatment, in addition to the devices, it is also possible to appropriately classify using a sieve or the like, or to use a pulverizing device having a classification function.

The carbon material production method of the present embodiment includes a melting stage and a carbon material precursor formation stage in the first baking step.

The melting stage is a method of melting a phenolic hydroxyl group-containing resin and a phosphate or a phosphoric acid derivative contained in the resin composition for a secondary battery negative electrode.

The carbon material precursor formation stage forms a crystallite of a preferred carbon containing a degreased and/or graphene-like structure.

In the carbon production method of the present embodiment, it is preferred that the phenolic hydroxyl group-containing resin melted by the melting step is heated to form a carbon material before boiling or decomposing the phosphorus compound or the phosphoric acid derivative melted by the melting step. Precursor.

In the first baking step, in order to realize the melting stage and the carbon material precursor formation stage, for example, the melting point of the phenolic hydroxyl group-containing resin and the phosphate ester contained in the resin composition exceeds the normal temperature and is 250 ° C. The following resin compositions are preferred. Thereby, the phenolic hydroxyl group-containing resin and the phosphate ester or the like can be melted (melting stage) before the self-condensation of the resin containing the phenolic hydroxyl group in the baking step of the carbonized resin composition.

Further, at a high temperature (for example, 300 ° C or higher and 800 ° C or lower), a resin composition containing a phenolic hydroxyl group-containing resin and a phosphate ester having a melting stage is calcined, and a resin containing a phenolic hydroxyl group is formed to contain degreasing. And a graphene-like structure of the preferred carbon crystallites to form a carbon precursor. In the method for producing a carbon material according to the present embodiment, since the phosphate ester before boiling or thermal decomposition is present in the carbon material precursor formation stage, the hydroxyl group of the phenolic hydroxyl group-containing resin is inhibited from being crosslinked by dehydration condensation. . Therefore, it is considered that the crystal structure of the generated carbon material precursor is formed into crystallites having excellent occlusion and release ability of chemical species such as lithium ions, or in the middle of formation.

In the method for producing a carbon material according to the present embodiment, the melting stage and the carbon material precursor formation stage may be independent of the first baking step, and the carbon material precursor is formed after the melting stage is completely completed, or Any one of the aspects in which the second half of the melting phase overlaps with the first half of the carbon precursor formation.

In the first firing step, the melting stage and the carbon precursor precursor formation stage can be determined by measuring the volume reduction or expansion of the phenolic hydroxyl group-containing resin, phosphate, or the like. In other words, the stage in which the phenolic hydroxyl group-containing resin and the phosphate ester are thermally melted in the first baking step and the volume tends to decrease is referred to as a melting stage. Further, the stage in which the volume of the phenolic hydroxyl group-containing resin which is reduced by melting in the first baking step exhibits expansion is referred to as a carbonaceous material precursor formation stage.

The gas atmosphere in the first baking step and the second firing step described above is not particularly limited, and can be carried out, for example, in an inert gas atmosphere. Examples of the inert gas include nitrogen gas, argon gas, helium gas, and the like. Among these gases, nitrogen is particularly preferred.

The gas atmospheres of the first baking step and the second firing step may be the same or different.

The conditions such as the temperature increase rate, the firing temperature, and the firing time in the first firing step and the second firing step can be appropriately adjusted in order to optimize the characteristics of the negative electrode of the carbon material to be used for the intended use.

According to the above carbon material production method, a carbon material for a secondary battery negative electrode can be obtained. The carbon material produced by the carbon material production method of the present embodiment has improved charge and discharge capacity and charge and discharge efficiency, and is excellent in battery characteristics.

The carbon material produced by the present embodiment can be used as a negative electrode active material used for a secondary battery negative electrode.

Further, the method for producing a carbon material for a secondary battery negative electrode of the present invention described above is an example of a method for producing a carbon material using the resin composition of the present invention, and does not exclude the use of the resin of the present invention by other production methods. The composition of the carbon material.

In the following, a negative electrode active material containing a carbon material obtained by using the resin composition of the present invention, a secondary battery negative electrode including a negative electrode active material layer containing the negative electrode active material, and a secondary battery including the negative electrode of the secondary battery are used. Description.

<Negative active material>

Hereinafter, the negative electrode active material of the present invention containing the carbon material produced by using the resin composition of the present invention will be described.

The negative electrode active material is capable of occluding and releasing a base in a secondary battery such as an alkali metal ion battery. A substance of a chemical species such as a metal ion such as lithium ion or sodium ion. The negative electrode active material described in the present specification means a material containing a carbon material produced by using the resin composition of the present invention.

The negative electrode active material may be composed substantially only of a carbon material, and may further contain a material different from the carbon material. As such a material, for example, a material which is generally known as a negative electrode material such as ruthenium, ruthenium oxide or a graphite material can be mentioned.

Among them, the negative electrode active material preferably contains a graphite material in addition to the above carbon material. Thereby, the charge and discharge capacity of the secondary battery such as an alkali metal ion battery can be improved. The carbon material produced by using the resin composition of the present invention not only improves the charge and discharge capacity, but also improves the charge and discharge efficiency, so that the increase in the charge capacity caused by the addition of the graphite material can be reflected in the improvement of the charge and discharge efficiency. ideal.

The particle diameter (average particle diameter) at 50% accumulation in the cumulative distribution of the volume basis of the graphite material to be used is preferably 2 μm or more and 50 μm or less, more preferably 5 μm or more and 30 μm or less.

<Secondary battery negative electrode and secondary battery>

Hereinafter, a secondary battery negative electrode of the present invention containing the above negative electrode active material and a secondary battery of the present invention including the secondary battery negative electrode will be described.

The secondary battery negative electrode of the present invention is characterized in that it has an active material layer for a secondary battery negative electrode containing the active material of the present invention, and a negative electrode current collector in which an active material layer for a secondary battery negative electrode is laminated.

Further, the secondary battery of the present invention is characterized by comprising the secondary battery negative electrode of the present invention, an electrolyte, and a secondary battery positive electrode.

The negative electrode for a secondary battery of the present invention (hereinafter also referred to simply as a negative electrode) is the above-mentioned The manufacturer of the negative electrode active material. Thereby, a negative electrode excellent in charge capacity and charge and discharge efficiency can be provided.

Moreover, the secondary battery of the present invention is manufactured using the negative electrode described in the present specification. Thereby, a secondary battery excellent in charge capacity and charge and discharge efficiency can be provided.

Moreover, the negative electrode of the present invention using the carbon material of the present invention and the secondary battery including the same can suppress the increase in electric resistance in a low-temperature environment, and can exhibit excellent battery performance. Therefore, the negative electrode of the present invention and the secondary battery provided therewith can be developed in various applications.

The secondary battery includes, for example, an alkali metal secondary battery such as a lithium ion secondary battery or a sodium ion secondary battery, but is not limited thereto. Further, the secondary battery includes various forms of a non-aqueous electrolyte secondary battery and a solid secondary battery using different electrolytes. In the following description, a lithium ion secondary battery will be described as an example of a secondary battery.

Hereinafter, an example of a lithium ion secondary battery including the negative electrode of the present invention containing the carbon material produced by using the resin composition of the present invention will be described with reference to Fig. 1 . Fig. 1 is a schematic view showing an example of a lithium ion secondary battery 100 which is one embodiment of the present invention containing a carbon material produced by using the resin composition of the present invention. The negative electrode 10 is the negative electrode of the present invention.

As shown in FIG. 1, the lithium ion secondary battery 100 includes a negative electrode 10, a positive electrode 20, a separator 30, and an electrolytic solution 40.

As shown in FIG. 1, the negative electrode 10 includes a negative electrode active material layer 12 and a negative electrode current collector 14.

The negative electrode active material layer 12 contains a carbon material obtained by using the above-described resin composition of the present invention.

The negative electrode current collector 14 is not particularly limited, and a commonly known negative electrode current collector can be used. For example, a copper foil or a nickel foil can be used.

The negative electrode 10 can be produced, for example, in the following manner.

A generally known organic polymer binder (for example, a fluorine-based polymer such as polyvinylidene fluoride or polytetrafluoroethylene; styrene-butadiene rubber or butyl rubber) is added to 100 parts by mass of the above-mentioned negative electrode active material. a rubber-like polymer such as butadiene rubber; or the like: 1 part by mass or more and 30 parts by mass or less, and an appropriate amount of solvent for viscosity adjustment (N-methyl-2-pyrrolidone, dimethylformamide, alcohol , water, etc.) or water is kneaded to prepare a negative electrode slurry.

Further, a conductive material may be further added to the above negative electrode active material as needed. As the conductive material, for example, any one or a combination of acetylene black, ketjen black, and fumed carbon fiber can be used. The amount of the conductive material to be added is not particularly limited. For example, it is preferably 2% by mass or more and 10% by mass or less, and more preferably 3% by mass or more and 7% by mass or less, based on 100% by mass of the negative electrode active material. It is also possible to use it outside these ranges. However, if the amount of the conductive agent is too large, the mass of the negative electrode active material present in the electrode is reduced to the extent required, and the volume capacity of the negative electrode is lowered.

The negative electrode active material layer 12 can be obtained by molding the obtained slurry into a sheet shape, a pellet shape or the like by compression molding, roll forming, or the like. Then, the anode 10 is obtained by laminating the anode active material layer 12 obtained in the above manner and the anode current collector 14.

Further, the negative electrode 10 can be produced by applying the obtained negative electrode slurry to the negative electrode current collector 14 and drying it.

The electrolyte 40 is filled between the positive electrode 20 and the negative electrode 10, and is a layer in which lithium ions are moved by charge and discharge.

The electrolytic solution 40 is not particularly limited, and a generally known electrolytic solution can be used. For example, a nonaqueous electrolytic solution in which a lithium salt serving as an electrolyte is dissolved in a nonaqueous solvent can be used.

As the nonaqueous solvent, for example, propylene carbonate or ethyl carbonate can be used. a cyclic ester such as γ-butyrolactone; a chain ester such as dimethyl carbonate, diethyl carbonate or ethyl methyl carbonate; a chain ether such as dimethoxyethane; or a mixture of such substances Wait.

The electrolyte is not particularly limited, and a generally known electrolyte can be used. For example, a lithium metal salt such as LiClO ₄ or LiPF ₆ can be used. Further, the above salts may be mixed with polyethylene oxide, polyacrylonitrile or the like to form a solid electrolyte.

The separator 30 is not particularly limited, and generally known separators can be used. For example, a porous film made of polyethylene or polypropylene or the like, a nonwoven fabric or the like can be used.

As shown in FIG. 1 , the positive electrode 20 includes a positive electrode active material layer 22 and a positive electrode current collector 24 .

The positive electrode active material layer 22 is not particularly limited, and can be formed by a generally known positive electrode active material. The positive electrode active material is not particularly limited, and for example, lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), lithium manganese oxide (LiMn ₂ O ₄ ), lithium nickel cobalt manganese oxide (LiNi) can be used. _a composite oxide such as _x Co _y Mn _z O ₂ , x+y+z=1); a conductive polymer such as polyaniline or polypyrrole;

The positive electrode active material contains an organic polymer binder and a conductive material in the same manner as the above-described negative electrode active material. The blending amount of the organic polymer binder and the conductive material in the positive electrode active material is not particularly limited, and may be the same as the negative electrode active material, or may be blended in an amount different from the negative electrode active material.

The positive electrode current collector 24 is not particularly limited, and a generally known positive electrode current collector can be used. For example, an aluminum foil, a stainless steel foil, a titanium foil, a nickel foil, a copper foil, or the like can be used.

Further, the positive electrode 20 in the present embodiment can be produced by a generally known method for producing a positive electrode.

In the above, the lithium ion secondary battery 100 has been described as an example. However, the above description does not exclude the case where the carbon material produced by using the resin composition of the present invention is used for a secondary battery other than a lithium ion secondary battery. The carbon material produced by using the resin composition of the present invention can also be used as a secondary battery using a base ion other than lithium ions such as sodium ions as a chemical species. In this case, each of the alkali ion secondary batteries may be configured using the same members as those of the above-described lithium ion secondary battery 100, and may be formed using different members. For example, in the negative electrode current collector in the sodium ion secondary battery, in addition to the negative electrode current collector exemplified above, an aluminum foil may be selected.

Although the embodiments of the present invention have been described above, these are examples of the present invention, and various configurations other than the above may be employed. For example, in FIG. 1, the anode active material layer 12 is formed on one surface of one side of the anode current collector 14, and the cathode active material layer 22 is formed on one surface of one side of the cathode current collector 24. example. As a variation, the anode active material layer 12 may be formed on both surfaces of the anode current collector 14, and the cathode active material layer 22 may be formed on both surfaces of the cathode current collector 24, and the spacer separator 30 and the electrolyte 40 may be opposed to each other. To form a secondary battery.

Further, the present invention is not limited to the embodiments described above, and modifications, improvements, etc. within the scope of the object of the invention are also included in the present invention.

The secondary battery can be formed by appropriately arranging the negative electrode 10, the positive electrode 20, the separator 30, and the electrolytic solution 40 in a casing suitable for the secondary battery. The type of the secondary battery is not specific, and examples thereof include a cylindrical type, a coin type, a square type, and a film type.

Next, a second aspect of the present invention will be described. The description of the same aspects as the first aspect will be substantially omitted, and the description will be focused on the aspects different from the first aspect.

The inventors of the present invention have proposed to use a phenol resin as a starting material for a carbon material for a negative electrode of a secondary battery. The carbon material for a secondary battery negative electrode having improved charge and discharge efficiency, and an electrode active material for a secondary battery negative electrode using the same, a secondary battery negative electrode, and a secondary battery were examined.

According to the above studies, the charge and discharge efficiency of the phenol resin having a large amount of phenol and a small hydroxyl group in the main chain like a novolac type phenol resin is insufficient. The inventors of the present invention presumed that the reason is as follows. Further, the novolac type phenol resin had a hydroxyl equivalent of 105 g/eq.

In other words, it is presumed that at least a part of the hydroxyl groups of the phenol resin are dehydrated and condensed in the molecule or in the molecule to be crosslinked in the firing step of firing the phenol resin having a small hydroxyl group equivalent to form a carbon material. It is considered that this crosslinking causes a problem in the carbon material that the growth of the crystal structure at the time of formation is hindered, and it is difficult to form a crystallite of a preferred carbon containing a graphene-like structure (hereinafter sometimes referred to simply as "the problem of crosslinking of a hydroxyl group" ). As a result, it is estimated that the carbon material-based chemical species such as lithium ions have insufficient storage and release ability, and it is difficult to exhibit excellent charge and discharge efficiency. The term "microcrystalline" as used herein refers to the largest aggregate of single crystals.

Therefore, the inventors of the present invention have completed the present invention based on the following technical idea by intensive research: the problem of crosslinking of a hydroxyl group is improved by using a phenol resin which is modified in such a manner that a hydroxyl group equivalent is in a specific range or more. As a result, the charge and discharge efficiency can be improved.

In the following, the resin containing a modified phenolic hydroxyl group for a negative electrode of a secondary battery (hereinafter also referred to simply as a resin containing a modified phenolic hydroxyl group), and a carbon material for a secondary battery negative electrode (hereinafter also referred to simply as a carbon material), A secondary battery negative electrode active material (hereinafter also referred to simply as a negative electrode active material), a secondary battery negative electrode (hereinafter also simply referred to as a negative electrode), and a secondary battery will be described.

<Resin phenolic hydroxyl group-containing resin for secondary battery negative electrode>

Hereinafter, the form of the resin composition for carrying out the present invention will be described in detail.

The resin containing a modified phenolic hydroxyl group for a negative electrode of a secondary battery of the present embodiment is characterized by a hydroxyl group The base equivalent is 115 g/eq or more.

Charging and discharging efficiency of a carbon material produced by using the modified phenolic hydroxyl group-containing resin as a starting material compared with a conventional carbon material obtained by using a resin having a hydroxyl equivalent weight of less than 115 g/eq as a novolac type phenol resin Improved. In other words, the resin containing a modified phenolic hydroxyl group in the present embodiment is useful as a starting material for producing a carbon material having excellent battery characteristics.

As described above, the hydroxyl group equivalent of the modified phenolic hydroxyl group-containing resin of the present embodiment is 115 g/eq or more, more preferably 130 g/eq or more, still more preferably 150 g/eq or more. It is considered that if the resin having a modified phenolic hydroxyl group having a hydroxyl equivalent of the above specific value or more is used, the problem of crosslinking of the hydroxyl group is remarkably improved. In addition, the upper limit of the hydroxyl group is not particularly limited, and the hydroxyl equivalent is, for example, preferably 5,000 g/eq or less, more preferably 3,000 g/eq or less, and still more preferably 1000 g. /eq below.

In the present embodiment, the resin containing a modified phenolic hydroxyl group is a resin having a structure in which an arbitrary portion is changed with respect to a phenol resin synthesized using only phenol as a starting material of a resin, and having a phenolic hydroxyl group in the molecule. .

For example, examples of the resin containing a modified phenolic hydroxyl group include a resin obtained by reacting phenol with a compound which is a modifier, such as a xylene-modified phenol resin.

Further, as another example of the resin containing a modified phenolic hydroxyl group, a resin synthesized using a phenol other than phenol such as a m-cresol resin, a xylenol resin or a naphthol resin can be mentioned.

In addition, as another example of the resin containing a modified phenolic hydroxyl group, a resin obtained by reacting a phenol other than phenol with a compound as a modifier can be exemplified.

A catalyst can be suitably used in the synthesis reaction of the above resin.

The term "phenol" as used herein means an organic compound having a hydroxyl group in an aromatic compound. Things. In the present embodiment, the phenol includes an organic compound in which a phenol and a cresol are equal to a functional group other than a hydroxyl group on the benzene ring. Specific examples of the phenols include, but are not limited to, phenol; o-cresol, m-cresol, p-cresol, xylenol, or an alkyl group such as p-tert-butylphenol. Phenols; aromatic substituted phenols such as p-phenylphenol; diphenols such as catechol or resorcin; naphthols such as α-naphthol or β-naphthol.

The compound as a modifier is described below.

The catalyst used in the case of producing a resin containing a modified phenolic hydroxyl group can be exemplified as described below. When the catalyst is roughly classified, there are two types of acid catalysts and alkali catalysts.

Specific examples of the acid catalyst include, but are not limited to, inorganic acid catalysts such as hydrochloric acid, sulfuric acid, phosphoric acid, and phosphorous acid; and metal catalysts such as Lewis acid catalyst: diethyl sulfate and oxalic acid. Or an organic acid catalyst such as p-toluenesulfonic acid; zinc acetate or the like.

Further, examples of the base catalyst include, but are not limited to, an alkaline catalyst such as sodium hydroxide, lithium hydroxide or potassium hydroxide; and an alkaline earth metal catalyst such as calcium, magnesium or barium; Amine-based catalyst such as ammonia; zinc acetate.

When a resin containing a modified phenolic hydroxyl group is produced, one type of catalyst may be used alone or two or more types of catalyst may be used in combination.

Further, in the case of producing a phenol resin, the reaction promoter may be further used as needed.

The resin containing a modified phenolic hydroxyl group in the present embodiment is, for example, a compound having a structure represented by the following formula (4). In the formula (4), P represents a structure containing a phenolic hydroxyl group, and A and B represent any atom or group of atoms constituting a main chain of a resin containing a modified phenolic hydroxyl group, and X represents an arbitrary aryl group, and n is An integer greater than one.

The upper limit of n in the general formula (4) is not particularly limited, and the negative electrode for the secondary battery is modified. From the viewpoint of practicality of the phenolic hydroxy resin, n is preferably an integer of 1000 or less.

The resin containing a modified phenolic hydroxyl group in the present embodiment may be a resin having a structure represented by the following formula (4) in one part of the repeating unit, or may be substantially continuous as a repeating unit of the following formula (4). Resin.

Specifically, as long as the P in the general formula (4) is a structure containing a phenolic hydroxyl group, a generally known aryl group such as a benzene nucleus, a naphthalene nucleus or a fluorenyl nucleus is exemplified, but the aryl group is not limited thereto.

Specifically, X in the general formula (4) is exemplified by a commonly known aryl group such as a benzene nucleus, a naphthalene nucleus or a fluorene nucleus, but is not limited thereto.

Since the resin containing a modified phenolic hydroxyl group represented by the formula (4) has a plurality of aromatic rings and has a hydroxyl group equivalent of a specific value or more, it is preferable as a starting material for forming a carbon material for a secondary battery.

The resin containing a modified phenolic hydroxyl group of the present embodiment may be a compound represented by the following formula (5), in particular, in the above formula (4).

(wherein, in the formula (5), X ₁ to X ₄ each independently represent a substituent or a hydrogen atom of the benzene nucleus)

That is, the formula (5) is specifically such that X in the formula (4) is a benzene nucleus having X ₁ to X ₄ .

Since the resin containing a modified phenolic hydroxyl group represented by the formula (5) has a plurality of benzene skeletons and has a hydroxyl group equivalent of a specific value or more, it is preferable as a starting material for forming a carbon material for a secondary battery.

The resin containing a modified phenolic hydroxyl group represented by the formula (5) has a structure containing a phenolic hydroxyl group (P in the formula (5)) and a structure containing the phenolic hydroxyl group in a repeating unit of the resin. The benzene nucleus (hereinafter also referred to as benzene nucleus) has a hydroxyl equivalent of 115 g/eq or more. Further, the so-called benzene nucleus contained in the formula (4) means an aromatic carbon six-membered ring.

Since the resin containing a modified phenolic hydroxyl group represented by the formula (4) has a structure containing a phenolic hydroxyl group and a benzene nucleus, it has two or more benzene skeletons in a repeating unit of a resin containing a modified phenolic hydroxyl group. Therefore, in the step of carbonizing the resin containing the modified phenolic hydroxyl group in the present embodiment, it is easy to form crystallites containing carbon which is preferably a graphene-like structure, and it is used as a starting material for a carbon material for a secondary battery negative electrode. Substance is preferred.

The modified phenolic hydroxyl group-containing resin of the present embodiment may have a specific structure represented by the formula (5) in a part of the repeating unit of the resin.

The benzene nucleus contained in the above repeating unit different from the structure containing a phenolic hydroxyl group has X ₁ to X ₄ , which are each independently hydrogen or an arbitrary substituent. Further, any two substituents of X ₁ to X ₄ (particularly any two substituents adjacent to the substitution position) may be bonded to each other to form a cyclic structure.

Any one of X ₁ to X ₄ in the formula (5) may be a hydrogen atom, or any of them may be a hydrogen atom, and the others may be any substituent. Further, X ₁ to X ₄ may all be the same substituent, and any two or more substituents may be the same substituent, and the other substituents may be different.

X ₁ to X ₄ in the formula (5) are not particularly limited, and examples thereof include a substituent such as a methyl group, a vinyl group, or an alkyl group such as an allyl group; an amine group; a vinyl group; a phenyl group, and the like. Aryl; hydroxyl. When the resin containing the modified phenolic hydroxyl group is fired to form a carbon material by repeating the resin containing the modified phenolic hydroxyl group in the repeating unit containing the modified phenolic hydroxyl group, the substituents are temporarily bonded to each other or a substituent. By virtue of the steric hindrance, it is expected to inhibit crosslinking caused by dehydration condensation of a hydroxyl group in a structure containing a phenolic hydroxyl group.

A preferred example of the resin containing a modified phenolic hydroxyl group in the present embodiment is any one of X ₁ to X ₄ in the formula (5), which is a methyl group.

The reason for this is that when the resin containing a modified phenolic hydroxyl group is carbonized by firing, any one of X ₁ to X ₄ as a methyl group reacts with other substituents containing carbon to contribute to the formation of carbon six. Member ring skeleton. Thereby, the resin containing a modified phenolic hydroxyl group can produce a carbon material having a structure containing a phenolic hydroxyl group in the general formula (5) and a carbon six-membered ring which is juxtaposed with a benzene nucleus and contains a carbon derived from a methyl group.

X ₁ and X ₂ in the above formula (5) can be, for example, represented by the following formula (6), and X ₁ and X ₂ are in a meta position by interposing one carbon atom of the benzene nucleus. Further, in the general formula (6), both X ₃ and X ₄ are hydrogen, and the illustration is omitted.

The resin containing a modified phenolic hydroxyl group in which both X ₁ and X ₂ in the formula (5) are a methyl group is one of preferable examples of the resin containing a modified phenolic hydroxyl group in the present embodiment. In this case, X ₃ and X _{4 are,} for example, hydrogen, but are not limited thereto.

That is, as an example of the resin containing a modified phenolic hydroxyl group in the preferred embodiment, X ₁ and X ₂ in the formula (5) are all methyl groups, and two methyl groups are one by one. A molecular structure in which a carbon atom is in a meta position (refer to the general formula (6)).

When the methyl group containing the modified phenolic hydroxyl group is carbonized by the methyl group, the cyclohexane having the carbon contained in the methyl group is formed adjacent to the benzene ring, and it is expected to form a preferable one. Graphene structure.

Preferred examples of the resin containing a modified phenolic hydroxyl group represented by the formula (6) in the present embodiment include the following.

For example, a resin containing a modified phenolic hydroxyl group in which A and B are methylene groups, and X ₁ and X ₂ are methyl groups is preferable as the resin containing a modified phenolic hydroxyl group in the present embodiment.

Further, A is a methylene group, and B is an atomic group having at least a methylene group bonded to a benzene nucleus represented by the formula (6) and another benzene nucleus bonded to the methylene group, X ₁ and X ₂ It is preferable that at least one of the methyl group-containing phenolic hydroxyl group-containing resins is a resin containing a modified phenolic hydroxyl group in the present embodiment.

Further, A is a methylene group (first methylene group), and B is a methylene group (second methylene group) having at least a bond with a benzene group represented by the formula (6) and with the methylene group ( a second methylene group-bonded to the other benzene nucleus and having an atomic group of a methyl group (first methyl group) replacing the hydrogen of the other benzene nucleus contained in B, and at least one of X ₁ and X ₂ is The resin containing a modified phenolic hydroxyl group of a methyl group (second methyl group) is preferable as the resin containing a modified phenolic hydroxyl group in the present embodiment. More specifically, for example, the methyl group (first methyl group) of the other benzene nucleus contained in the above B is the first position of the bonding position of the methylene group (second methylene group) contained in B. Substituting hydrogen in the sixth position clockwise.

Next, A and B in the general formula (4) will be described. A and B in the formula (4) are bonded to X (aryl) in the formula (4) to form any atom or group of atoms of the main chain of the resin containing the modified phenolic hydroxyl group. A and B may be the same atom or the same atomic group, may be different atoms or different atomic groups, or may be either an atom or the other is an atomic group.

Examples of the atom include oxygen, and the like, but are not limited thereto. Further, examples of the atomic group include an alkyl chain such as a methylene group (-CH ₂ -). However, the present invention is not limited thereto, and may further contain a complicated molecular structure.

For example, the molecular structure of A or B in the general formula (4) may contain a structure containing a phenolic hydroxyl group different from P represented by the general formula (4) or different from the benzene nucleus represented by the general formula (4). Benzene nucleus. As described above, when the resin containing the modified phenolic hydroxyl group is carbonized by baking the A or B-containing benzene skeleton, it is expected to form a graphene structure which is more excellent.

Examples of preferred specific structures of the formula (4) include the chemical formula (7) to the chemical formula (10) shown below. However, the specific examples do not limit the general formula (4). n in the chemical formula (7) to the chemical formula (10) is an integer of 1 or more, and the upper limit is not particularly limited, and from the viewpoint of practicality, n is preferably 1,000 or less.

In order to produce a resin containing a modified phenolic hydroxyl group represented by the formula (4), for example, a phenol may be reacted with a modifier represented by the following formula (11). A catalyst can be suitably used for this reaction. However, the formula (11) does not limit the modifier used to form the modified phenolic hydroxyl group-containing resin of the present embodiment.

(In the formula (11), C represents an atom or a group of atoms containing A in the formula (4), and D represents an atom or a group of atoms containing B in the formula (4), and X ₁ and X ₂ are each independently Ground indicates a substituent or hydrogen atom of the benzene nucleus)

The modifier represented by the formula (11) has an atom or a group of atoms (i.e., C and D in the formula (11)), and the atom or group of atoms contains a benzene nucleus and a phenol which reacts with the benzene nucleus. Bonded atoms or groups of atoms (ie, A and B in the formula (4)). Therefore, the modified phenolic hydroxyl group-containing resin obtained by reacting the modifier represented by the formula (11) with a phenol is in a repeating unit. It contains two or more benzene skeletons, and has a hydroxyl equivalent of 115 g/eq or more.

One of the specific compounds of the resin containing a modified phenolic hydroxyl group represented by the formula (4) is a phenol aralkyl resin.

The phenol aralkyl resin means a resin produced by reacting the above phenol with an aralkyl compound as a modifier.

Here, the aralkyl group means that one hydrogen atom of the alkyl group is substituted with an aryl group such as a phenyl group. The above-mentioned aralkyl compound means a compound having the above aralkyl group.

Among them, a compound in which one hydrogen atom of an organic compound is substituted with a phenyl group constituting an aralkyl group is preferred, and the alkyl group constituting the aralkyl group is interposed with the above-mentioned organic compound. Alkyl compound. More preferably, it is preferably an aralkyl compound having the same molecular structure as the above-mentioned organic compound in which the above-mentioned alkyl group of the phenyl group is located in the para position. Specific examples of the particularly preferable aralkyl compound include p-xylylene glycol dimethyl ether or p-divinyl benzene.

The phenol aralkyl resin produced by the reaction of the above preferred aralkyl compound with a phenol is preferable as the resin containing a modified phenolic hydroxyl group in the present embodiment.

The resin containing a modified phenolic hydroxyl group obtained by reacting the above-mentioned preferred aralkyl compound with a phenol is a linear one having two or more benzene skeletons and having a hydroxyl group equivalent of 115 g/eq or more in a repeating unit of the resin. The resin is easy to handle, and is carbonized by firing to provide a carbon material excellent in battery characteristics.

The preferred phenol aralkyl resin as the resin containing a modified phenolic hydroxyl group in the present embodiment is, for example, a modified phenolic property obtained by reacting a phenol with terephthalic acid dimethyl ether under an acidic catalyst. Hydroxyl resin. Examples of the acidic catalyst include diethyl sulfate, but are not limited thereto.

Further, as a different aspect, a preferred phenol aralkyl resin as a resin containing a modified phenolic hydroxyl group in the present embodiment is obtained by reacting a phenol with divinylbenzene under an acidic catalyst. A resin that modifies a phenolic hydroxyl group. Examples of the acidic catalyst include p-toluenesulfonic acid, but are not limited thereto.

One of the specific compounds different from the modified phenolic hydroxyl group-containing resin represented by the formula (4) is a xylene-modified phenol resin obtained by reacting a phenol with a xylene or xylene-modified compound. .

The xylene-modified phenol resin is a resin which contains two or more benzene skeletons and a hydroxyl group equivalent of 115 g/eq or more in a repeating unit of the resin, and carbonizes by firing to provide a carbon material excellent in battery characteristics.

The xylene may be any of o-xylene, m-xylene, or p-xylene. Further, the xylene-modifying compound may be any one of an o-xylene modified compound, a metaxylene modified compound, or a p-xylene modified compound. The xylene-modified compound is not particularly limited, and examples thereof include a compound in which a plurality of xylenes are crosslinked by a methyl group and/or an ether bond to form a linear chain. The commercially available product is exemplified by a xylene-modified compound (trade name: NIKANOL (registered trademark)) manufactured by Fudow Co., Ltd., but is not limited thereto.

According to a conventionally known method for synthesizing a phenol resin, a resin containing a modified phenolic hydroxyl group can also be synthesized by synthesizing a monomer other than a phenol with an aldehyde such as formaldehyde in the presence of an acid or a basic catalyst.

In the following, the details of the resin composition for a secondary battery negative electrode, the carbon material for a negative electrode, the negative electrode active material, the secondary battery negative electrode, and the secondary battery will be described in detail.

<Resin composition for secondary battery negative electrode>

The modified phenolic hydroxyl group-containing resin of the present invention may be formed into a secondary battery negative electrode resin composition by firing alone, but may be combined with any additives to form a secondary battery negative electrode resin composition. (hereinafter also referred to as resin composition).

For example, a resin composition containing the modified phenolic hydroxyl group-containing resin of the present invention and a curing agent can be prepared and used as a material for a carbon material for a secondary battery negative electrode. This is because the heat curing of the resin containing the modified phenolic hydroxyl group is promoted when carbonization is performed by firing.

The blending amount of the curing agent in the resin composition is not particularly limited, and is, for example, 0.1 parts by mass or more and 50 parts by mass or less based on 100 parts by mass of the resin containing a modified phenolic hydroxyl group.

The method for preparing the resin composition is not particularly limited and can be carried out by an appropriate method. For example, it can be prepared by subjecting a resin containing a modified phenolic hydroxyl group to a method of (1) melt-mixing, (2) a method of dissolving in a solvent and mixing, (3) a method of pulverizing and mixing, and the like. .

<Carbon material for secondary battery negative electrode>

Next, the carbon material for a secondary battery of the present invention will be described.

The carbon material of the present invention is a carbon material produced by using the above-described modified phenolic hydroxyl group-containing resin of the present invention.

The carbon material of the present invention is improved in charge and discharge efficiency and excellent in battery characteristics as compared with a carbon material produced by using a resin having a hydroxyl equivalent of less than 115 g/eq as a novolac type phenol resin.

In particular, the charge and discharge efficiency of the carbon material obtained by firing the resin containing the modified phenolic hydroxyl group represented by the formula (4) and carbonizing it is favorably improved. The reason is considered to be that two or more of the repeating units of the resin containing a modified phenolic hydroxyl group used as a starting material are contained. The benzene skeleton, so that the carbon material produced has a crystallite of a preferred carbon containing a graphene-like structure.

In a preferred embodiment of the present invention, the carbon material contains: a surface area per unit volume (hereinafter also referred to as a surface area per unit volume) obtained from a particle size distribution on a number basis basis of 10000 cm ^-1 or more and 16,000 cm ^- Carbon particles in the range of ¹ or less.

The lower limit of the surface area per unit volume described above may further be 12,000 cm ^-1 or more. Further, the upper limit of the surface area per unit volume may be 15500 cm ^-1 or less or 14,000 cm ^-1 or less.

The carbon material of the present invention can be used as a carbon material of a material for an active material for a negative electrode. The carbon material containing carbon particles having a surface area of the above-mentioned range per unit volume has an effect of suppressing an increase in electric resistance when charging and discharging a secondary battery in a low-temperature environment (hereinafter also referred to as a resistance suppression effect).

The method for producing the carbon material of the present invention is not particularly limited, and can be suitably produced, for example, by the following production method.

That is, the carbon material of the present invention can be produced by a production method having a first baking step and a second firing step.

The first baking step is a resin composition containing a modified phenolic hydroxyl group or a resin containing a modified phenolic hydroxyl group at a maximum temperature of less than 1000 ° C at the time of firing (hereinafter sometimes referred to as a resin composition) A step of firing a resin containing a modified phenolic hydroxyl group to form a carbonaceous material precursor.

The second baking step is a step of firing a carbon material precursor generated in the first firing step by firing conditions at a temperature at which the highest temperature at the time of firing is 1000 ° C or higher, thereby producing a carbon material.

The carbon material of the present invention can be obtained by the above production method, but this production method is an example of a method for producing a carbon material. The carbon material produced by using the modified phenolic hydroxyl group-containing resin of the present invention can also be produced by other production methods different from the above production methods.

Hereinafter, it is obtained by using a resin containing a modified phenolic hydroxyl group of the present invention or the like. The negative electrode active material of the present invention containing the carbon material, the negative electrode of the present invention containing the negative electrode active material of the present invention, and the secondary battery of the present invention including the negative electrode will be described.

<Secondary battery negative active material>

Next, the secondary battery negative electrode active material of the present invention will be described.

The negative electrode active material of the present invention contains the above-described carbon material of the present invention. As described above, since the carbon material of the present invention achieves an improvement in charge and discharge efficiency, the charge and discharge efficiency of the negative electrode active material of the present invention containing the carbon material is also improved.

<Secondary battery negative electrode and secondary battery>

Next, the secondary battery negative electrode and secondary battery of the present invention will be described.

The negative electrode of the present invention has a negative electrode active material layer containing the above-described negative electrode active material of the present invention, and a negative electrode current collector in which the negative electrode active material layer is laminated.

The secondary battery of the present invention comprises the negative electrode, the electrolyte, and the positive electrode for a secondary battery of the present invention.

The negative electrode of the present invention comprises a negative electrode active material layer containing a negative electrode active material having improved charge and discharge efficiency, and exhibits excellent battery characteristics. Therefore, the secondary battery of the present invention having the negative electrode of the present invention is excellent in battery characteristics and can be expected to be used in various fields.

Hereinafter, the negative electrode of the present invention and the secondary battery of the present invention including the negative electrode will be described. Fig. 1 is a schematic view showing an example of a lithium ion secondary battery containing a carbon material produced by using the modified phenolic hydroxyl group-containing resin of the present invention.

Fig. 1 is a schematic view showing a lithium ion secondary battery 100 as an example of a secondary battery of the present invention.

As shown in FIG. 1, the lithium ion secondary battery 100 includes a negative electrode 10, a positive electrode 20, and a separator 30. And electrolyte 40.

As shown in FIG. 1, the negative electrode 10 includes a negative electrode active material layer 12 and a negative electrode current collector 14.

The negative electrode active material layer 12 contains the carbon material of the present invention produced by using the above-described modified phenolic hydroxyl group-containing resin of the present invention as a starting material.

The negative electrode current collector 14 is not particularly limited, and a commonly known negative electrode current collector can be used. For example, a copper foil, a nickel foil, or the like can be used.

Although the lithium ion secondary battery 100 of the present embodiment has been described as an example, it is not excluded that the carbon material produced by using the modified phenolic hydroxyl group-containing resin of the present invention is used for a lithium ion secondary battery. The case of the secondary battery. The carbon material produced by using the modified phenolic hydroxyl group-containing resin of the present invention can be used, for example, as a secondary battery using a base ion other than lithium ions such as sodium ions as a chemical species.

Next, a third aspect of the invention will be described. The descriptions of the first and second aspects are substantially omitted, and the description will be made focusing on the differences from the first and second aspects.

The present inventors have studied in order to improve the absorption and release of chemical species in carbon materials, and have found that the above problems can be solved if it is a carbon material containing a specific range of phosphorus and achieving a carbon dioxide adsorption amount that does not reach a specific value. Thus, the present invention has been completed.

That is, although the conventional carbon material suggests that the lithium ion storage amount is improved by containing phosphorus as described above, it has not been studied to sufficiently release the absorbed lithium ions.

In the study for solving the above problems, the inventors of the present invention focused on the carbon dioxide adsorption amount of the carbon material. It is known that carbon materials having a large amount of adsorption of carbon dioxide are excellent in lithium ion absorption. example A carbonaceous material for a secondary battery electrode having a carbon dioxide adsorption amount of 10 ml/g or more is disclosed in Japanese Laid-Open Patent Publication No. H10-223226 (Patent Document 3), and the carbon dioxide adsorption amount is 10 ml/ The amount of lithium ions doped with the carbonaceous material for the secondary battery electrode below g is small and is not preferable.

However, according to the study by the inventors of the present invention, it is understood that the carbon material having a carbon dioxide adsorption amount of 10 ml/g or more has a strong tendency to be irreversible although the lithium ion storage amount is increased. The reason for this is not clear, and it is presumed that the lithium ions absorbed by the collected lithium ions are aggregated inside the carbon material having a large amount of carbon dioxide adsorbed, and thus it is difficult to be released.

Therefore, the inventors of the present invention conducted intensive studies, and as a result, in a carbon material containing a specific range of phosphorus, carbon dioxide adsorption which is generally considered to be unsatisfactory from the viewpoint of lithium ion absorption is shown to be less than 10 ml/g. Amount of carbon material. Surprisingly, although the amount of carbon dioxide adsorbed by the carbon material is less than 10 ml/g, the absorption of chemical species such as lithium ions is improved. Further, the release of lithium ions absorbed in the carbon material of the present invention is also improved, and the charge and discharge efficiency is also excellent. That is, the combination of the phosphorus in the desired range in the carbon material of the present invention and the carbon dioxide adsorption amount which does not reach a specific value interact to improve the absorption and release of the chemical species.

<Carbon material for secondary battery negative electrode>

Hereinafter, the form of the carbon material for carrying out the present invention will be described in detail. In the description of the present embodiment, lithium ions are appropriately exemplified as the chemical species. However, this is an example, and the aspect in which the carbon materials of the present embodiment are occluded to release other chemical species is not excluded.

The carbon material for a secondary battery negative electrode of the present embodiment contains phosphorus as a main component, and contains phosphorus in a range of 0.3% by mass or more and 1.5% by mass or less, and the amount of adsorption of carbon dioxide is less than 10 ml/g per unit weight.

In the carbon material of the present embodiment having such a configuration, the absorption and release of chemical species such as lithium ions are improved. In other words, in the carbon material of the present embodiment, the amount of the chemical species such as lithium ions is improved, and the chemical species that are absorbed are sufficiently released, so that the charge and discharge efficiency is high. Therefore, as a material for constituting the negative electrode of the secondary battery, it is preferable to improve the battery characteristics of the secondary battery negative electrode using the same.

The carbon material of the present embodiment contains carbon as a main component. The main component herein is not specified by a strict numerical value, but it is preferably at least 80% or more, more preferably 90% or more, and particularly preferably 95% or more of the carbon atom in at least 100% of the composition of the carbon material. Further, the carbon material of the present embodiment contains at least carbon as a main component and phosphorus in a specific range, but does not exclude atoms other than the carbon material.

(phosphorus content)

The phosphorus contained in the carbon material of the present embodiment is contained in a range of 0.3% by mass or more and 1.5% by mass or less based on the carbon material. When the content of phosphorus contained in the carbon material is 0.3% by mass or more, the amount of lithium ions absorbed is remarkably improved. In addition, when the content of phosphorus contained in the carbon material is 1.5% by mass or less, the amount of lithium ions absorbed can be improved, and the composition ratio of carbon which is a main component of the carbon material can be maintained high. In the present invention, the content of phosphorus can be appropriately adjusted by, for example, adjusting the amount of addition of a phosphate compound such as a phosphate ester for producing a carbon material.

In the present embodiment, the phosphorus content can be measured, for example, using a high frequency inductively coupled plasma (ICP) luminescence analyzer.

(the amount of carbon dioxide adsorbed)

The carbon dioxide adsorption amount in the carbon material of the present embodiment is less than 10 ml/g per unit weight, more preferably 5 ml/g or less. The release of lithium ions by the amount of carbon dioxide adsorbed in the above numerical range Excellent. The reason for this is not clear. It is presumed that the amount of adsorption of carbon dioxide is within this numerical range, and the accumulation of lithium ions absorbed can be prevented, and smooth release can be achieved. Further, it is considered that the amount of adsorption of carbon dioxide shown in the present embodiment is not preferable for the storage of lithium ions, but the presence of phosphorus contained in the carbon material is even under the numerical range of the amount of adsorption of carbon dioxide. It will also improve the absorption of lithium ions.

The lower limit of the amount of adsorption of carbon dioxide in the carbon material of the present embodiment is not particularly limited, and is preferably, for example, 0.05 ml/g or more per unit weight, and more preferably 0.1 ml/g or more. The reason for this is that if the amount of adsorption of carbon dioxide is at least the above lower limit value, it is difficult to hinder the absorption of lithium ions, and interaction with the phosphorus-containing effect can achieve good absorption of lithium ions.

In the present embodiment, the carbon dioxide adsorption amount can be measured by vacuum drying the carbon material at 200 ° C for 2 hours or more using a vacuum dryer to obtain a measurement sample, and measuring it using a known carbon dioxide adsorption amount measuring device. As the carbon dioxide measuring device, for example, a gas adsorption measuring device (BELSORP-max) manufactured by NIPPON BEL Co., Ltd. can be cited.

In order to prevent the amount of carbon dioxide adsorbed by the carbon material from reaching a specific value, for example, it is preferably selected from a phosphate compound such as a phosphate used to form a carbon material, a choice of a curing agent or a curing catalyst, or a firing temperature. The above conditions are adjusted.

(phosphorus or phosphorus compounds contained in carbon materials)

The carbon material of the present embodiment contains reduced phosphorus (hereinafter also referred to as reduced phosphorus) or a compound containing phosphorus detected by X-ray photoelectron spectroscopy (hereinafter also referred to as XPS). Here, the reduced phosphorus and the compound containing phosphorus which can be detected by XPS are referred to as target compounds.

From the viewpoint of improving the battery performance of the carbon material, the carbon material of the present embodiment is preferably 100% of the composition of the target compound, and the triphenylphosphine oxide ((C ₆ H ₅ ) ₃ P ( The total composition ratio of =O)), triphenylphosphine ((C ₆ H ₅ ) ₃ P), and reduced phosphorus is 50% or more, and the composition ratio of the reduced phosphorus is 13% or less.

The carbon material in the present embodiment can be remarkably present in a composition ratio of reducing phosphorus on the surface of 13% or less and more than 0%.

According to the study by the inventors of the present invention, it is known that a large amount of a direct bond (PC bond) of phosphorus to a carbon constituting a benzene nucleus is detected by a target compound contained in a carbon material, and phosphorus and a carbon-separating oxygen constituting a benzene nucleus are detected. The bond between the bonds (POC key) and the reduction of phosphorus on the surface of the carbon material are not excessive, so that the battery performance of the carbon material tends to be high. The reason why the battery performance of the carbon material of the present embodiment can be improved by this configuration is not clear, and it is presumed that these compositions have a better influence on the realization of a more desirable graphene structure in the carbon material. Further, the term "graphene-like structure" as used herein means a structure having at least partially a structure having a structure similar to or similar to the carbon hexagonal lattice structure exhibited in graphene, or a laminate There is a laminated structure of the sheet structure.

The target compound may differ depending on the kind of the starting material used to form the carbon material, the production conditions, and the like. For example, the carbon material recommended in the present embodiment is a carbon material produced by firing a resin composition containing a phenol resin and triphenyl phosphate ((C ₆ H ₅ O) ₃ P(-O)). In the carbon material, the target compound detected by XPS contains the following materials.

[Target Compound 1] (C ₆ H ₅ O) ₃ P(=O)

[Target Compound 2] (C ₆ H ₅ O) ₂ P(=O)(OH)

[Target Compound 3] (C ₆ H ₅ ) ₂ P(=O)(OH)

[Target Compound 4] (C ₆ H ₅ ) ₃ P(=O)

[Target Compound 5] (C ₆ H ₅ ) ₃ P

[Target Compound 6] Reduction of Phosphorus

The carbon material of the present embodiment is preferably a total composition of the target compounds 1 to 6, and the total composition of the target compounds 4 to 6 is 50% or more.

(composition ratio of oxygen to carbon)

The carbon material of the present embodiment preferably has a composition ratio O/C of oxygen to carbon detected by X-ray photoelectron spectroscopy (XPS) greater than a composition ratio O/C of oxygen to carbon detected by composition analysis.

That is, the O-converted oxygen content and the C-converted carbon content in the surface of the carbon material were measured by XPS, and the composition ratio O/C was determined. Further, the compositional analysis was carried out to measure the total O-converted oxygen content and the C-converted carbon content in the carbon material, and the composition ratio O/C was determined. As described above, it is preferable that the composition ratio O/C of oxygen to carbon detected by XPS is larger than the composition ratio O/C of oxygen to carbon detected by compositional analysis.

It is presumed that the above-mentioned composition ratio of oxygen to carbon O/C is such that the carbon in the main body (internal) has a higher ratio of carbon present to form a more desirable graphene structure.

(The composition ratio of phosphorus on the surface of the carbon material and the main body)

The carbon material of the present embodiment is preferably such that the composition ratio P (XPS) of phosphorus detected by X-ray photoelectron spectroscopy (XPS) is larger than the composition ratio P (COMP) of phosphorus detected by composition analysis.

That is, the P-converted phosphorus content in the surface of the carbon material was measured by XPS. Further, the total P content in the carbon material was measured by composition analysis. These composition ratios are then compared, and preferably P(XPS) > P(COMP).

As described above, the battery performance of the carbon material can be improved by making the surface phosphorus ratio of the carbon material more than the inside. The reason for this is not clear, and it is presumed that the effect of promoting the absorption of lithium ions in the carbon material can be suitably exhibited.

The carbon material of the present embodiment is preferably P(XPS)>P(COMP), and P (COMP) exceeds 0. The reason for this is that, although the composition ratio is inferior to the surface, phosphorus is remarkably contained inside the carbon material, and lithium ions can be smoothly absorbed to the inside of the carbon material.

In addition, a known X-ray photoelectron spectroscopy apparatus can be used for the detection by XPS in the present embodiment. Specifically, for example, an X-ray photoelectron spectroscopy analyzer ESCA-3400 manufactured by Shimadzu Corporation can be used, but Limited to this.

The composition analysis in the present invention means the analysis of the elements contained in the entire carbon material. The specific analysis method of the above composition analysis is not particularly limited, and can be carried out by appropriately selecting a known method.

For example, carbon, hydrogen, and nitrogen contained in the carbon material can be quantified by oxygen cycle combustion and gas chromatography detection. Specifically, the carbon material to be a sample is completely burned at about 850 ° C to generate CO ₂ gas and H ₂ O gas, and carbon and hydrogen contained in the gases are quantified by gas chromatography. The nitrogen is reduced after completion of the above complete combustion, and is also quantified by gas chromatography in the form of nitrogen (N ₂ ).

Further, the oxygen contained in the carbon material can be quantified by a heat melting or non-dispersive infrared absorption method. Specifically, the carbon material to be a sample is heated in a helium atmosphere at about 2500 ° C to generate CO gas and CO ₂ gas, and the oxygen contained in the gas is quantified by a non-dispersive infrared absorption method.

Further, the phosphorus contained in the carbon material can be quantified by ashing, acid melting, and high-frequency inductively coupled plasma luminescence spectrometry. Specifically, the carbon material to be a sample is ashed, and then dissolved in hydrochloric acid, and the phosphorus contained in the molten material is quantified by high-frequency inductively coupled plasma luminescence spectrometry.

As a preferred aspect of the present invention, the carbon material contains: a surface area per unit volume (hereinafter also referred to as a surface area per unit volume) obtained by a particle size distribution on a number basis basis of 10000 cm ^-1 or more and 16,000 cm ^- Carbon particles in the range of ¹ or less.

The lower limit of the surface area per unit volume described above may further be 12,000 cm ^-1 or more. Further, the upper limit of the surface area per unit volume may be 15500 cm ^-1 or less or 14,000 cm ^-1 or less.

The carbon material of the present invention can be used as a carbon material of a material for an active material for a negative electrode. The carbon material containing carbon particles having a surface area of the above-described range per unit volume has an effect of suppressing an increase in electric resistance when charging and discharging a secondary battery in a low-temperature environment (hereinafter also referred to as a resistance suppression effect). The reason why the electric resistance suppression effect is exhibited in the carbon material of the above aspect is not clear. However, the carbon material of this aspect is moderately small in size, and is formed in such a manner that the surface area per unit volume becomes sufficiently large. Therefore, it is estimated that the lithium ion absorbing and releasing efficiency of the carbon material of this aspect is high, and even when the action of lithium ions becomes slow in a low temperature environment, the occlusion release can be smoothly performed. In other words, it is presumed that the carbon material of this aspect significantly increases the surface area of the particles as the occlusion release region of lithium ions by the carbon material compared to the previous carbon material, thereby offsetting the decrease in the mobility of lithium ions in a low temperature environment. Suppress the increase in resistance.

<Manufacture of Carbon Material for Secondary Battery Negative Electrode>

Hereinafter, an example of a method for producing a carbon material according to the present embodiment will be described. The carbon material of the present embodiment can be suitably produced according to the production method described below (hereinafter also referred to as the production method). However, the present production method described below does not limit the method for producing the carbon material of the present invention.

(Preparation of resin composition for secondary battery negative electrode)

First, a resin composition for producing a carbon material is prepared.

The resin composition used in the production method contains an organic compound and a phosphoric acid compound.

Organic compounds:

The organic compound is not particularly limited, and for example, a resin containing a phenolic hydroxyl group and a petroleum-based material such as hydrazine or petroleum pitch can be used.

The phenolic hydroxyl-containing resin is a synthetic material that can cope with the diversified secondary batteries used in the technical field of use, and expands the freedom of design of the negative electrode. From this point of view, the phenolic hydroxyl group-containing resin is preferred as the starting material of the carbon material in the negative electrode.

In the present embodiment, the phenolic hydroxyl group-containing resin means a resin having a phenolic hydroxyl group in the molecule. The phenolic hydroxyl group-containing resin in the present embodiment includes a resin synthesized by using a phenol as a starting material such as a novolac type phenol resin or a resol type phenol resin; m-cresol resin, xylenol resin, and naphthol resin; a resin which is synthesized by using a phenol other than phenol; a resin having a phenolic hydroxyl group in a molecule obtained by synthesizing a monomer other than a phenol and an aldehyde such as formaldehyde in the presence of an acid or a basic catalyst; or the above resin A resin containing a modified phenolic hydroxyl group containing a modifier.

For example, the above phenolic hydroxyl group-containing compound can be synthesized by reacting a phenol with any reactive compound.

Among them, the molecular structure of a phenolic hydroxyl group-containing resin having a hydroxyl equivalent of 300 g/eq or less represented by a novolac type phenol resin is simplified and easily synthesized, and is one of preferable examples of a starting material of a carbon material.

Since the phenolic hydroxyl group-containing resin having a small hydroxyl equivalent has a large amount of hydroxyl groups in the molecule, in the calcination step for carbonizing the carbon material, the hydroxyl group is dehydrated and condensed in the molecule and/or in the molecule to crosslink. The growth of the ideal graphene structure in the resulting carbon material is hindered. On the other hand, in the resin composition which is a material of the carbon material, the specific phosphate ester described below is contained, and the dehydration condensation of the above-mentioned hydroxyl group can be suppressed, and the occluded release amount of lithium ions is high. Carbon material.

Examples of the phenolic hydroxyl group-containing resin having a hydroxyl group equivalent of 300 g/eq or less include a novolac type phenol resin, a resol type phenol resin, or a combination of a phenol and a phenol. The resin of the phenolic hydroxyl group is modified, but is not limited thereto.

The hydroxyl equivalent here means the molecular weight of the phenolic hydroxyl group-containing resin with respect to one hydroxyl group. The measurement of the hydroxyl equivalent can be carried out in accordance with the method specified in JIS K 0070 (1992) and the titration method.

In the present specification, the term "novolak type phenol" means a phenol resin synthesized by reacting the above phenols with formaldehyde under an acid catalyst. In the present specification, the term "resin novolac type phenol" means a phenol resin synthesized by reacting the above phenols with formaldehyde under a base catalyst.

In general, the smaller the hydroxyl group equivalent (for example, the hydroxyl group equivalent of 200 g/eq or less, further 150 g/eq or less, especially 120 g/eq or less), the more preferable from the viewpoint of easiness of production and production cost, and it is expected to be two. The use of materials for the negative electrode of the secondary battery. The resin composition of the present invention contains such a phenolic hydroxyl group-containing resin having a small hydroxyl group equivalent, and can be substantially used as a starting material for providing a carbon material exhibiting excellent battery characteristics.

In the production method, the phenolic hydroxyl group-containing resin includes a resin synthesized by reacting a phenol with a reaction compound. The catalyst may be used as needed in the synthesis of the phenolic hydroxyl group-containing resin. The term "phenol" as used herein means an organic compound having a hydroxyl group in an aromatic compound, and contains not only a so-called phenol but also an organic compound having a cresol equal to a functional group other than a hydroxyl group on the benzene ring. The above-mentioned reaction compound contains not only formaldehyde but also a modifier compound which can synthesize a resin containing a modified phenolic hydroxyl group.

Specific examples of the phenols include, but are not limited to, phenol; o-cresol, m-cresol, p-cresol, xylenol, or an alkyl group such as p-tert-butylphenol. Phenols; aromatic substituted phenols such as p-phenylphenol; diphenols such as catechol or resorcin; Naphthol such as α-naphthol or β-naphthol.

Phosphoric acid compound:

A phosphoric acid compound is contained in the resin composition used in the production method in order to contain phosphorus in the produced carbon material.

The phosphoric acid compound used in the production method is not particularly limited, and for example, a phosphoric acid compound having a relatively small molecular weight such as phosphoric acid or phosphorus pentoxide or a specific phosphoric acid compound described below can be used. It is preferable to use a phosphate ester as a phosphoric acid compound from the viewpoint of providing a carbon material having a total composition ratio of triphenylphosphine oxide, triphenylphosphine, and phosphorus atom contained in the target compound of 50% or more. In order to use a phosphate having one or more phenyl groups.

In addition, a resin having a phenolic hydroxyl group having a hydroxyl equivalent of 300 g/eq or less is used as a starting material, and a crosslinking temperature or thermal decomposition is contained in the resin composition from the viewpoint of inhibiting crosslinking caused by dehydration condensation of a hydroxyl group. A phosphate or phosphoric acid derivative having a temperature exceeding the self-condensation temperature of the phenolic hydroxyl group-containing resin is preferred. The reason for this is that, in the case where the resin composition is baked by carbonization, the phenolic hydroxyl group-containing resin starts to condense at a point of time (that is, the hydroxyl group of the phenolic hydroxyl group-containing resin) In the stage of dehydration condensation to cause a crosslinking reaction, a phosphate which is not boiled or decomposed may be present in the reaction system. In this way, by hydrogen bonding or the like with a hydroxyl group of a phenolic hydroxyl group-containing resin by a phosphate ester or the like, the reactivity of the hydroxyl group is lowered, and crosslinking due to dehydration condensation is suppressed, so that it is expected to avoid hindering carbon. The growth of the crystal structure.

In the present specification, the self-condensation means that the phenolic hydroxyl group contained in the phenolic hydroxyl group-containing resin is subjected to dehydration condensation in the molecule and/or between molecules unless otherwise specified.

The blending amount of the phosphate ester or the like contained in the resin composition used in the production method is not particularly limited. For example, it is preferably 100 parts by mass based on 100 parts by mass of the phenolic hydroxyl group-containing resin. A phosphate or a phosphoric acid derivative is contained in a range of not less than 15 parts by mass. Thereby, the produced carbon material can contain phosphorus in a range of 0.3% by mass or more and 1.5% by mass or less.

The phosphate or phosphoric acid derivative contained in the resin composition used in the production method is preferably one selected from the self-condensation temperature of a resin having a melting point of less than a phenolic hydroxyl group.

In the step of firing the resin composition to form a carbon material, the hydroxy group-containing resin hydroxy group can be dehydrated and condensed to start the crosslinking of the phosphate ester before the crosslinking starts, and the resin composition can be improved. The dispersibility of phosphates and the like. By dispersing the phosphate compound or the like in the resin composition well, it is possible to efficiently crosslink the hydroxyl group in the phenolic hydroxyl group-containing resin with respect to the phosphate resin having a significantly lower content of the phenolic hydroxyl group-containing resin. inhibition. Further, a carbon material having a high composition ratio of a direct bond (P-C bond) of carbon to phosphorus described above can be produced.

For example, when the hydroxyl group of the novolac type phenol resin starts dehydration condensation at about 300 ° C, it is preferred that the melting point of the phosphate or the like does not reach 300 ° C. For example, from the above viewpoints, triphenyl phosphate having a melting point of 48.5 ° C or higher, an aromatic condensed ester of the above chemical formula (1) having a melting point of 92 ° C or higher, polyphosphoric acid having a melting point of about 200 ° C, or the like is preferably used.

In the present production method, the melting point of the phosphate ester or the like and the melting point of the phenolic hydroxyl group-containing resin means the temperature of the peak top of the endothermic peak analyzed by the differential scanning calorimetry (hereinafter also referred to as DSC).

additive:

The resin composition used in the present production method may further contain any additives as needed. For example, the resin composition used in the production method may further contain a curing agent. The reason for this is that the hardener promotes thermal hardening of the phenolic hydroxyl group-containing resin.

The curing agent is not particularly limited, and is appropriately selected according to the combination with the phenolic hydroxyl group-containing resin to be used. Just decide. For example, when the phenolic hydroxyl group-containing resin contained in the resin composition is a novolac type phenol resin, hexamethylenetetramine, a resol type phenol resin, or a polyacetal can be suitably used. In the case where the phenolic hydroxyl group-containing resin contained in the resin composition is a resol type phenol resin, hexamethylenetetramine or the like can be used.

The blending amount of the curing agent in the resin composition is not particularly limited, and is, for example, 0.1 parts by mass or more and 50 parts by mass or less based on 100 parts by mass of the phenolic hydroxyl group-containing resin. The novolac type phenol resin contained in the resin composition may be cured in the step of firing and carbonizing the resin composition without using a curing agent, but may not significantly inhibit the baking of the resin composition. The growth range of the crystal structure of the produced carbon material contains a hardener. For example, the content of the curing agent is not particularly limited, and the curing agent may be contained in an amount of 0.1 part by mass or more and 5 parts by mass or less based on 100 parts by mass of the novolac type phenol resin.

Examples of the additive other than the curing agent include an organic acid, an inorganic acid, a nitrogen-containing compound, an oxygen-containing compound, an aromatic compound, and a non-ferrous metal atom. These additives may be used singly or in combination of two or more kinds depending on the kind or properties of the resin to be used.

(baking of resin composition)

Next, the present manufacturing method in which the resin composition prepared as described above is fired to produce a carbon material will be described below. Specifically, a resin containing a phenolic hydroxyl group having a hydroxyl equivalent of 300 g/eq or less, and a resin containing a phosphate or a phosphoric acid derivative having a boiling temperature or a pyrolysis temperature exceeding a self-condensation temperature of the phenolic hydroxyl group-containing resin An example in which the carbon material of the present embodiment is produced as a composition will be described.

The production method has, for example, a first baking step and a second firing step.

The first firing step is performed on the secondary temperature when the maximum temperature at the time of firing is less than 1000 ° C The step of firing the resin composition of the cell negative electrode to form a carbon material precursor.

The second baking step is a step of firing a carbon material precursor generated in the first firing step by firing conditions at a temperature at which the highest temperature at the time of firing is 1000 ° C or higher, thereby producing a carbon material.

The first firing step and the second firing step may be carried out continuously or separately.

As an example of the aspect in which the first step and the second step are separately performed, for example, the carbon material precursor obtained by the first firing step may be pulverized between the first firing step and the second firing step. The comminution step. From the viewpoint of making the thermal history of the carbon material precursor in the second firing step uniform, it is preferred to carry out the above pulverization step. The particle diameter of the pulverized material of the carbon material precursor obtained in the pulverization step is not particularly limited, and is 1 μm or more and 20 μm or less, and more preferably 5 μm or more and 15 μm or less. When the particle diameter of the pulverized material is equal to or greater than the lower limit of the numerical value range, the workability of the pulverized material is good, and the phosphorus contained in the phosphate ester or the like can be remarkably left in the finally formed carbon material. Further, by the particle diameter of the pulverized material being equal to or less than the upper limit of the above digital range, the heat history of the carbon material in the second baking step can be satisfactorily achieved.

The particle diameter of the above pulverized material means the particle diameter (D50, average particle diameter) at which 50% of the cumulative distribution of the volume basis is accumulated.

Further, by adjusting the pulverization conditions in the pulverization step, a carbon material containing carbon particles having a surface area per unit volume or a square radius of a preferred range can be produced.

The pulverization method in the above pulverization step is not particularly limited, and for example, any pulverization apparatus can be used. Examples of the pulverizing device include the following devices, but are not limited thereto: a pulverizing device such as a ball mill device, a vibrating ball mill device, a rod mill device, or a bead mill device; or a cyclone device or a jet mill device; Airflow pulverizing device such as dry airflow pulverizing device. In the pulverization process, the devices may be used one or two or more, or may be pulverized by one device. use. Further, in the pulverization treatment, in addition to the devices, it is also possible to appropriately classify using a sieve or the like, or to use a pulverizing device having a classification function.

The manufacturing method includes a melting stage and a carbon material precursor formation stage in the first firing step.

The melting stage is a method of melting a phenolic hydroxyl group-containing resin and a phosphate or a phosphoric acid derivative contained in the resin composition for a secondary battery negative electrode.

The carbon material precursor formation stage forms a crystallite of a preferred carbon containing a degreased and/or graphene-like structure.

In the carbon production method of the present embodiment, it is preferred that the phenolic hydroxyl group-containing resin melted by the melting step is heated to form a carbon material before boiling or decomposing the phosphorus compound or the phosphoric acid derivative melted by the melting step. Precursor.

In the first baking step, in order to realize the melting stage and the carbon material precursor formation stage, for example, the melting point of the phenolic hydroxyl group-containing resin and the phosphate ester contained in the resin composition exceeds the normal temperature and is 250 ° C. The following resin compositions are preferred. Thereby, the phenolic hydroxyl group-containing resin and the phosphate ester or the like can be melted (melting stage) before the self-condensation of the resin containing the phenolic hydroxyl group in the baking step of the carbonized resin composition.

Further, at a high temperature (for example, 300 ° C or higher and 800 ° C or lower), a resin composition containing a phenolic hydroxyl group-containing resin and a phosphate ester having a melting stage is calcined, and a resin containing a phenolic hydroxyl group is formed to contain degreasing. And a graphene-like structure of the preferred carbon crystallites to form a carbon precursor. In the present production method, since there is a phosphate or the like before boiling or thermal decomposition in the carbon material precursor formation stage, the hydroxyl group of the phenolic hydroxyl group-containing resin is inhibited from being crosslinked by dehydration condensation. Therefore, it is considered that the crystal structure of the generated carbon material precursor is It is formed into a crystallite having excellent sorption and release ability of a chemical species such as lithium ion or in the middle of formation.

In the manufacturing method, the melting stage and the carbon material precursor formation stage may be independent of the first firing step, and the carbon material precursor formation stage is started after the melting stage is completely finished, or the second half of the melting stage. Any of the aspects in which the segment overlaps with the first half of the carbon precursor formation phase.

In the first firing step, the melting stage and the carbon precursor precursor formation stage can be determined by measuring the volume reduction or expansion of the phenolic hydroxyl group-containing resin, phosphate, or the like. In other words, the stage in which the phenolic hydroxyl group-containing resin and the phosphate ester are thermally melted in the first baking step and the volume tends to decrease is referred to as a melting stage. Further, the stage in which the volume of the phenolic hydroxyl group-containing resin which is reduced by melting in the first baking step exhibits expansion is referred to as a carbonaceous material precursor formation stage.

The gas atmosphere in the first baking step and the second firing step described above is not particularly limited, and can be carried out, for example, in an inert gas atmosphere. Examples of the inert gas include nitrogen gas, argon gas, helium gas, and the like. Among these gases, nitrogen is particularly preferred.

The gas atmospheres of the first baking step and the second firing step may be the same or different.

The conditions such as the temperature increase rate, the firing temperature, and the firing time in the first firing step and the second firing step can be appropriately adjusted in order to optimize the characteristics of the negative electrode of the carbon material to be used for the intended use.

According to the above carbon material production method, a carbon material for a secondary battery negative electrode can be obtained. The charge and discharge capacity and charge and discharge efficiency of the carbon material produced by the present production method are improved, and the battery characteristics are excellent.

The carbon material produced in the present embodiment can be used as an active material for a negative electrode used in a negative electrode of a secondary battery.

Further, the method for producing a carbon material for a secondary battery negative electrode of the present invention described above is manufactured. An example of the method of the carbon material of the present embodiment does not exclude the case where the carbon material is produced by another manufacturing method.

In the following, the negative electrode active material of the present invention containing the carbon material of the present invention, the secondary battery negative electrode of the present invention including the negative electrode active material layer containing the negative electrode active material, and the present invention including the secondary battery negative electrode The secondary battery will be described.

<Active material for negative electrode>

The active material for a secondary battery negative electrode of the present invention contains the above-described carbon material for a secondary battery negative electrode of the present invention. When the carbon material of the present invention is excellent in occlusion of an alkali metal ion such as lithium ion or sodium ion, the active material for a negative electrode of the present invention contributes to an improvement in charge capacity and charge and discharge efficiency of the negative electrode. In the present invention, the active material for a negative electrode refers to a material which can occlude and release a chemical species which becomes a charge carrier in a negative electrode of a secondary battery. Examples of the above chemical species include an alkali metal ion secondary battery, and examples thereof include lithium ions and sodium ions.

Hereinafter, the active material for a negative electrode containing the resin composition of the present invention will be described.

The active material for a negative electrode is a substance which can absorb and release a chemical species such as an alkali metal ion (for example, lithium ion or sodium ion) in a secondary battery such as an alkali metal ion battery. The active material for a negative electrode described in the present specification means a material containing a carbon material produced by using the resin composition of the present invention.

The active material for a negative electrode may be substantially composed only of the carbon material of the present invention, and may further contain a material different from the carbon material. As such a material, for example, a material which is generally known as a negative electrode material such as ruthenium, ruthenium oxide or other graphite material can be mentioned.

50% of the cumulative distribution of the volume basis of the graphite material used The particle diameter (average particle diameter) is preferably 2 μm or more and 50 μm or less, more preferably 5 μm or more and 30 μm or less.

<Secondary battery negative electrode and secondary battery>

Hereinafter, the secondary battery negative electrode of the present invention and the secondary battery of the present invention including the secondary battery negative electrode will be described.

The secondary battery of the secondary battery of the present invention has a secondary battery negative electrode active material layer containing the active material for a secondary battery negative electrode of the present invention, and a negative electrode current collector layer in which a secondary battery negative electrode active material layer is laminated. Composition.

Moreover, the secondary battery of the present invention comprises the above-described secondary battery negative electrode of the present invention, an electrolyte, and a secondary battery positive electrode.

The negative electrode of the present invention is constituted by using the active material for a negative electrode of the present invention, and is excellent in charge capacity and charge and discharge efficiency. Further, the secondary battery of the present invention comprising the negative electrode of the present invention exhibits an improvement in charge capacity and charge and discharge efficiency of the negative electrode and exhibits excellent battery performance.

[Examples]

Hereinafter, examples and comparative examples of the present invention will be described. However, the present invention is not limited to the examples and comparative examples shown below. Furthermore, in the examples, "parts" means "parts by mass" and "%" means "mass%".

(Synthesis of phenolic hydroxyl-containing resin)

First, the phenolic hydroxyl group-containing resin used in the examples or the comparative examples was synthesized in the following manner.

(Synthesis of novolac type phenol resin)

100 parts of phenol, 64.5 parts of 37% formaldehyde aqueous solution, and 3 parts of oxalic acid were placed in a three-necked flask equipped with a stirrer and a cooling tube, and reacted at 100 ° C for 3 hours, and then heated and dehydrated to obtain a novolak type. 90 parts of phenol resin. The hydroxyl equivalent of the novolac type phenol resin obtained by the above method was measured in accordance with JIS K 0070 (1992) and titration, and found to be 105 g/eq.

(Synthesis of Resol Resin Phenol Resin)

100 parts of phenol, 55 parts of paraformaldehyde, and 1 part of zinc acetate were placed in a three-necked flask equipped with a stirrer and a cooling tube, and reacted at 100 ° C for 3 hours, followed by dehydration, and then at 100 ° C for 2 hours under reaction conditions. It was aged to obtain 90 parts of a solid novolac type phenol resin. The hydroxyl equivalent of the novolac type phenol resin obtained by the above method was measured in accordance with JIS K 0070 (1992) and titration, and found to be 105 g/eq.

(Synthesis of xylene modified novolac resin)

100 parts of phenol resin, 70 parts of NIKANOL H (manufactured by Fudow Co., Ltd.) as a xylene resin, and 1 part of 25% sulfuric acid were placed in a three-necked flask equipped with a stirrer and a cooling tube, and reacted at a reflux temperature for 2 hours. Then, 48 parts of a 37% aqueous solution of Formalin was added successively and reacted for 2 hours. Thereafter, calcium hydroxide was added for neutralization, and the temperature was dehydrated to obtain 160 parts of a xylene-modified phenol resin.

The hydroxyl equivalent of the xylene-modified phenol resin obtained by the above method was measured in the same manner as in Example 1 and found to be 155 g/eq.

<Example 1>

With respect to 100 parts of the novolac type phenol resin obtained by the above-described method, 10 parts of triphenyl phosphate (manufactured by Daiha Chemical Industry Co., Ltd., trade name: TPP) and hexamethylenetetramine 3 were used by a vibration ball mill. The granules were pulverized and mixed to obtain a resin composition. The resin composition obtained by the above method was designated as Example 1.

The resin of Example 1 was heated at a rate of 100 ° C / hour under a nitrogen atmosphere. The composition was heated from room temperature to 550 ° C, and then kept in a fired state for 1.5 hours to carry out a carbonization treatment (first baking step). Thereafter, a pulverization step is carried out to obtain a carbon material precursor.

The carbon material precursor was fired at room temperature at a temperature elevation rate of 100 ° C / hr in a nitrogen atmosphere to a temperature of 1200 ° C, and then the carbonized state was maintained for 2 hours to carry out carbonization treatment (second baking step). The carbon material thus obtained was used as the carbon material of Example 1.

Further, the pulverization conditions of the above pulverization step in Example 1 are as follows. In Examples 2 to 9 and Comparative Example 1, the pulverization step was also carried out between the first baking step and the second firing step under the pulverization conditions described below.

<Example 2>

The same material and the same method were used except that the triphenyl phosphate used in Example 1 was changed to 10 parts of an aromatic condensed phosphate ester (manufactured by Daiha Chemical Industry Co., Ltd., trade name: PX-200). A resin composition was prepared to obtain a resin composition. The resin composition obtained by the above method was designated as Example 2.

A carbon material was produced in the same manner as in the method of producing the carbon material of Example 1 except that Example 2 was used, and the carbon material was used as Example 2.

<Example 3>

The resin composition was obtained by pulverizing and mixing 10 parts of triphenyl phosphate (manufactured by Daiba Chemical Industry Co., Ltd., trade name: TPP) with a vibrating ball mill to 100 parts of the novolac type phenol resin obtained in the above manner. . The resin composition obtained by the above method was designated as Example 3.

The first firing step and the second firing step were carried out for carbonization under the same conditions as in the method for producing a carbon material according to Example 1 except that the resin composition of Example 3 was used. deal with. The carbon material thus obtained was used as the carbon material of Example 3.

<Example 4>

A resin composition was prepared in the same manner as in Example 1 except that the curing agent was not used, and was set as Example 4.

A carbon material was produced in the same manner as in the above-described production method of the carbon material of Example 1, except that the resin composition of Example 4 was used, and this carbon material was used as the carbon material of Example 4.

<Example 5>

The resin composition was obtained by pulverizing and mixing 10 parts of triphenyl phosphate (manufactured by Daiha Chemical Industry Co., Ltd., trade name: TPP) with a vibrating ball mill to 100 parts of the xylene-modified novolac resin obtained by the above-mentioned manner. Things. The resin composition obtained by the above method was designated as Example 5.

The first baking step and the second firing step were subjected to carbonization treatment under the same conditions as those of the above-described method for producing a carbon material, except that the resin composition of Example 5 was used. The carbon material thus obtained was used as the carbon material of Example 5.

<Example 6>

The resin composition was prepared in the same manner as in Example 1 except that the temperature in the second baking step was changed from 1200 ° C to 1100 ° C, and the conditions were the same as those in the above-described Example 1 carbon material formation method. The first baking step and the second firing step are performed to perform carbonization treatment. The carbon material thus obtained was used as the carbon material of Example 6.

<Example 7>

The resin composition was prepared in the same manner as in Example 1 and changed to the pulverization conditions different from the pulverization conditions of Example 1 as described below, and in addition to the above Example 1 The carbon baking treatment is carried out under the same conditions as in the method of producing the carbon material by performing the first baking step and the second baking step. The carbon material thus obtained was used as the carbon material of Example 7.

<Example 8>

The resin composition was prepared in the same manner as in Example 1 and changed to the pulverization conditions different from the pulverization conditions of Example 1 as described below, except for the method of producing the carbon material of Example 1 described above. The first baking step and the second firing step are carried out under the conditions of carbonization. The carbon material thus obtained was used as the carbon material of Example 8.

<Example 9>

Compared with 100 parts of a biphenyl aralkyl resin (manufactured by Nippon Kayaku Co., Ltd., trade name: Kayahard GPH-103, hydroxyl equivalent 228) as a commercial product, triphenyl phosphate was used in a vibrating ball mill (Da Ba Chemical Industry Co., Ltd.) Manufactured by the company, trade name: TPP) 10 parts, and hexamethylenetetramine 3 parts were pulverized and mixed to obtain a resin composition. The resin composition obtained by the above method was designated as Example 9. The phosphorus content in Example 9 was calculated to be 0.84%.

The first baking step and the second baking step were subjected to carbonization treatment under the same conditions as in the method for producing a carbon material of Example 1, except that the resin composition of Example 9 was used. The carbon material thus obtained was used as the carbon material of Example 9.

<Comparative Example 1>

The novolac type phenol resin obtained by the above method was used as Comparative Example 1.

100 parts of the novolac type phenol resin of Comparative Example 1 was heated from room temperature at a temperature elevation rate of 100 ° C / hr in a nitrogen atmosphere, and the temperature was raised to 550 ° C, and then the baked state was maintained for 1.5 hours to carry out carbonization treatment (first Burning step). Thereafter, a pulverization step is carried out to obtain a carbon material precursor.

The carbon material precursor was fired at room temperature at a temperature elevation rate of 100 ° C / hr in a nitrogen atmosphere to a temperature of 1200 ° C, and then the carbonized state was maintained for 2 hours to carry out carbonization treatment (second baking step). The carbon material thus obtained was used as the carbon material of Comparative Example 1.

The phosphorus content contained in each of the examples and the comparative examples was calculated and shown in Table 1.

Further, the pulverization step in each of the examples and the comparative examples was carried out under the following pulverization conditions using the fired product obtained in the first baking step. The carbon precursor obtained by the pulverization step is supplied to the second firing step.

Example 1: The intermediate obtained by carrying out the first baking step was naturally placed and cooled to room temperature, and placed in a ball mill pulverizing device. 15mm alumina ball 5000g and A 10 mm alumina ball was placed in a container of 900 g to obtain a pulverized intermediate. Then, the above-mentioned pulverized intermediate was passed through a sieve of 75 μm mesh to remove coarse particles, thereby obtaining a pulverized material (carbon precursor).

Examples 2 to 6: The pulverization step was carried out under the same conditions as in Example 1 to obtain a pulverized material (carbon precursor).

Example 7: The intermediate obtained by carrying out the first baking step was naturally placed and cooled to room temperature, and the apparatus was pulverized using a cyclone mill at a powder supply amount of 50 g/min, an air volume of 0.5 m ³ /min, and a first crushing impeller. The pulverization intermediate was obtained by pulverizing under the conditions of a rotation speed of 15,000 rpm and a second pulverization impeller rotation speed of 15,000 rpm. Then, the pulverized intermediate was passed through a sieve of 75 μm mesh to remove coarse particles, thereby obtaining a pulverized material (carbon precursor).

Example 8: The intermediate obtained by carrying out the first baking step was naturally placed and cooled to room temperature, and the apparatus was pulverized by a cyclone mill at a powder supply amount of 30 g/min, an air volume of 0.8 m ³ /min, and a first crushing impeller. The pulverization intermediate was obtained by pulverizing under the conditions of a rotation speed of 13,000 rpm and a second pulverization impeller rotation speed of 13,000 rpm. Then, the pulverized intermediate was passed through a sieve of 75 μm mesh to remove coarse particles, thereby obtaining a pulverized material (carbon precursor).

Comparative Example 1: A pulverization step was carried out under the same conditions as in Example 1 to obtain a pulverized material (carbon precursor).

Further, the pulverizing apparatus used in the above pulverization treatment is as follows.

The ball mill pulverizing device uses a rotary ball mill (1 segment-B, supplied by Jinjiang Chamber of Commerce Co., Ltd.).

The cyclone mill pulverizing apparatus was a dry pulverizer (150 BMW type cyclone mill, manufactured by Shizuoka Plant Co., Ltd.).

[Measurement of true specific gravity]

With respect to the carbon materials of each of the examples and the comparative carbon materials obtained in the above manner, the true specific gravity was measured by a true specific gravity measuring method using butanol. The measurement results are shown in Table 1.

[Measurement of surface area]

Using a particle size distribution measuring apparatus (particle size distribution measuring apparatus LA-920, manufactured by Horiba, Ltd.), the particle size distribution under the basis of the number of the carbon materials of each of the examples and the comparative carbon materials was measured in the following order.

20 mg of the carbon material obtained by the above method, 1 ml of a surfactant (Tween 20, manufactured by Kishida Chemical Co., Ltd.) diluted to about 1 wt%, and about 5 ml of distilled water were placed in a polymer material container, and placed in a polymer container. In the ultrasonic cleaner, while mixing with a dropper for 1 minute, ultrasonic waves were applied and dispersed to obtain a dispersion. The dispersion was supplied to the above-described particle size distribution measuring apparatus, and the particle size distribution was measured at a setting of a relative refractive index of 1.5.

Using the data obtained by the above particle size distribution measurement, the surface area per unit volume was calculated from the above formula (1). The calculated values are shown in Table 1.

[calculation of mean square radius]

Using the data obtained by the particle size distribution measurement described above, the mean square radius of each of the carbon materials of the examples and the comparative example carbon materials was calculated from the above formula (2). The calculated values are shown in Table 1.

<Production of a half-cell type lithium ion secondary battery>

(production of negative electrode)

In order to evaluate the battery characteristics of the carbon materials of the respective examples obtained in the above manner and the carbon materials of the comparative examples, a negative electrode using each carbon material was produced as described below.

Compared with the carbon materials of the respective examples and the carbon materials of the comparative example, 100% of the styrene-butadiene rubber blended as a binder at a ratio of 3%, and the carboxymethyl group as a tackifier was blended at a ratio of 1.5%. The cellulose is blended into a conductive material of acetylene black in a ratio of 2%, and an appropriate amount of pure water is added for dilution mixing to obtain a slurry-form negative electrode mixture.

The slurry-form negative electrode mixture obtained above was applied to a copper foil (current collector) having a thickness of 10 μm in the same manner each time, and vacuum-dried at 110 ° C for 1 hour. Then, it was press-molded by a roll press to a thickness of 60 μm, and was punched into a specific shape to prepare a disk having a diameter of 13 mm and an electrode active material layer (parts other than the current collector) having a thickness of 50 μm. A negative electrode for a lithium ion secondary battery.

(production of working electrode)

A lithium metal having a thickness of 1 mm was prepared as a working electrode.

(Preparation of electrolyte)

An electrolytic solution was prepared by dissolving lithium hexafluorophosphate in a mixture of ethyl carbonate and diethyl carbonate (volume ratio of 3:7) at a concentration of 1 mol/liter.

(Production of lithium ion secondary battery)

A lithium ion secondary battery was produced in the following manner using the negative electrode, the working electrode, and the electrolytic solution obtained in the above manner.

A negative electrode, a separator (polypropylene porous film, thickness: 25 μm), and a working electrode were placed in a specific position of a two-electrode cell manufactured by Baoquan Co., Ltd., and an electrolytic solution was injected to prepare a lithium ion secondary battery.

[Evaluation of initial charge and discharge characteristics]

Using the half-cell type lithium ion secondary battery fabricated by the above method, battery characteristics were evaluated as described below.

The measurement temperature was set to 25 ° C, and the current density during charging was set to 25 mA/g for constant current charging. From the time point when the potential reached 0 V, constant voltage charging was performed while maintaining 0 V, and charging was performed until the current density became 2.5 mA/g. Up to now, the above electric quantity is used as the initial charging capacity.

Then, the current density at the time of discharge was set to 25 mA/g, and constant current discharge was performed, and the amount of electricity at the time point when the potential reached 2.5 V was used as the initial discharge capacity.

The initial charge and discharge efficiency is calculated by multiplying the value obtained by dividing the initial discharge capacity by the initial charge capacity by 100 as shown in the following formula (3). In addition, the result of the evaluation of the initial charge and discharge characteristics is shown in Table 1.

In the evaluation of the initial charge and discharge characteristics, "charging" means that a working electrode made of lithium ion free metal lithium is moved to a negative electrode formed using a carbon material by applying a voltage. In addition, "discharge" means a phenomenon in which lithium ions are moved from a negative electrode composed of a carbon material to a working electrode made of metallic lithium.

Initial charge and discharge efficiency (%) = [first discharge capacity (mAh / g) / initial charge capacity (mAh/g)]×100 (3)

<Production of full-cell type lithium ion secondary battery>

In order to evaluate the battery characteristics in the low-temperature environment of the examples and comparative examples obtained in the above manner, a full-cell type lithium ion secondary battery was produced.

The production method was carried out by the same method except that the working electrode in the above-described method for producing a half-cell type lithium ion secondary battery was changed to a positive electrode.

As the positive electrode, a person who uses LiCoO ₂ as an active material and applies it to a current collector is used, and as a current collector of a positive electrode, a single-layer sheet (manufactured by Pionics Co., Ltd., trade name; Pioxcel C-100) was formed into a disc having a diameter of 12 mm.

[Low temperature environmental test]

The measurement was carried out in the following manner using the all-cell type lithium ion secondary battery fabricated by the above method.

The measurement temperature was set to 25 ° C, and the current density during charging was set to 25 mA / g for constant current charging. From the time point when the potential reached 4.2 V, the constant voltage was charged while maintaining 4.2 V, and the current density was 2.5 mA. Immediately after /g, the current density at the time of discharge was set to 25 mA/g, and constant current discharge was performed, and the discharge was performed until the potential reached 2.5 V. Further, charging and discharging were carried out under the same conditions, and charging and discharging were carried out for a total of five cycles to carry out an aging treatment.

After the aging treatment, each of the lithium ion secondary batteries was charged to 4.2 V at a constant current of 0.2 C in a temperature environment of 25 ° C, and thereafter, charged at a constant voltage of 4.2 V until the current value was attenuated to 0.02 C. Then, the discharge was performed at a constant current of 0.2 C, adjusted so as to become 50% of SOC (State of Charge), and left at 25 ° C for 1 hour. Then, each lithium ion secondary battery was allowed to stand in a temperature environment of -20 ° C for 1 hour, and the following "low temperature environment charge and discharge treatment" was carried out for 3 times. cycle.

That is, in the low-temperature environmental discharge treatment, the lithium ion secondary battery is set in a temperature environment of -20 ° C, and the voltage at the time of charging at a specific current value for 10 seconds is measured, and then placed for 10 minutes, and then discharged only at a specific current value. The voltage was measured at 10 seconds and then left for 10 minutes. Specifically, the above-mentioned specific current value is 1/3 C, 0.5 C, and 1 C from the first cycle to the third cycle. In the above low-temperature environmental discharge treatment, the upper limit voltage was set to 4.2 V, and the lower limit voltage was set to 2.5 V.

Here, "1C" means the current density at the end of discharge in one hour.

Regarding the above-described low-temperature environmental discharge treatment, the current value is plotted on the horizontal axis, and the voltage after charging or discharging for 10 seconds on the vertical axis is plotted, and the charging time and the discharge time in the battery are determined based on the absolute value of the slope of the approximate straight line. DC resistance (DC-IR), and based on this value, the low-temperature environmental characteristics were evaluated in the following manner. Lower DC-IR means less resistance and good output characteristics.

The DC resistance during charging is 195 Ω or less, and/or the DC resistance during discharge is 215 Ω or less...... ◎

The DC resistance during charging exceeds 195 Ω and is 210 Ω or less, and the DC resistance during discharge exceeds 215 Ω and is 220 Ω or less... ○

The DC resistance during charging exceeds 210Ω, and/or the DC resistance during discharge exceeds 220Ω...△

[Evaluation of high temperature storage characteristics]

Using the all-cell type lithium ion secondary battery of each of the examples and the comparative examples produced as described above, the high-temperature storage characteristics were evaluated as follows.

The measurement temperature was set to 25 ° C, and the current density at the time of charging was set to 25 mA/g for constant current charging. From the time point when the potential reached 4.2 V, 4.2 V was maintained and constant voltage charging was performed. The battery was charged until the current density reached 2.5 mA/g, and then the current density at the time of discharge was set to 25 mA/g, and a constant current discharge was performed, and the discharge was performed until the potential reached 2.5 V, which was taken as one cycle. Further, charging and discharging were carried out under the same conditions, and charging and discharging were carried out for a total of five cycles to carry out an aging treatment. The discharge capacity (discharge capacity I) at the time of discharge in the fifth cycle of the above aging treatment was measured.

Using a full-cell type lithium ion secondary battery which was aged as described above, the current density was set to 25 mA/g for constant current charging, and from the time point when the potential reached 4.2 V, 4.2 V was further maintained for constant voltage charging. The battery was charged until the current density reached 2.5 mA/g, and a lithium ion secondary battery in which the SOC was adjusted to 100% was prepared.

The lithium ion secondary battery obtained by the above method was stored in a dryer adjusted to a temperature of 60 ° C for one week, and the discharge capacity of the stored lithium ion secondary battery was confirmed in the following manner.

In other words, the lithium ion secondary battery after storage was charged and discharged at a current value of 0.2 C, and a total of three cycles of charge and discharge were performed as one cycle. The discharge capacity (discharge capacity II) at the time of discharge in the third cycle was measured.

As shown in the following formula (4), the discharge capacity (discharge capacity II) of the third cycle of the lithium ion secondary battery after storage is divided by the discharge capacity (discharge capacity I) of the fifth cycle during the aging treatment. The obtained value was multiplied by 100, and the value thus obtained was evaluated as "high temperature storage characteristic".

High-temperature storage characteristics (%) = [discharge capacity II (mAh / g) / discharge capacity I (mAh / g)] × 100 (4)

The high temperature storage characteristics of each of the examples and the comparative examples are shown in Table 1.

[Evaluation of high temperature life characteristics]

Aging is performed in the same manner as the aging treatment in the above-described high-temperature storage property evaluation The full-cell type lithium ion secondary batteries of the respective examples and comparative examples obtained by the treatment were evaluated for high-temperature life characteristics as follows.

That is, after the aging treatment, each lithium ion secondary battery was charged to 4.2 V at a constant current of 1 C in a temperature environment of 55 ° C, and thereafter, charged at a constant voltage of 4.2 V until the current value was attenuated to 0.02 C. , kept at 55 ° C for 30 minutes. Then, it was discharged to 2.5 V at a constant current of 1 C, and kept at a temperature of 55 ° C for 30 minutes, thereby taking one cycle. The discharge capacity (discharge capacity III) of the lithium ion secondary battery at the time of discharge in the first cycle was measured.

Then, 99 cycles of charge and discharge were performed under the same conditions as above, and charging and discharging for a total of 100 cycles were performed. The discharge capacity (discharge capacity IV) at the time of discharge in the 100th cycle was measured, and "high-temperature life characteristic evaluation" was performed. Specifically, as shown in the following formula (5), the discharge capacity (discharge capacity IV) of the 100th cycle is divided by the discharge capacity (discharge capacity III) of the first cycle, and the value obtained is multiplied by 100 to The value thus obtained was evaluated as "high temperature life characteristics".

High-temperature life characteristics (%) = [discharge capacity IV (mAh / g) / discharge capacity III (mAh / g)] × 100 (5)

The high temperature life characteristics of each of the examples and the comparative examples are shown in Table 1.

[Decomposition evaluation of lithium ion secondary battery after high temperature life test]

The above-described lithium ion secondary batteries of the respective examples and comparative examples evaluated by the high-temperature life characteristics were decomposed in an environment having a dew point of -60 ° C or less, and the presence or absence of lithium deposition was visually confirmed.

Specifically, five lithium ion secondary batteries of each of the examples and the comparative examples evaluated by the high-temperature life characteristics were prepared, and each of the lithium ion secondary batteries was decomposed and confirmed on the exposed negative electrode surface. The number of lithium ion secondary batteries deposited by lithium was evaluated.

In each of the examples and the comparative examples, the number of lithium ion secondary batteries in which lithium was precipitated on the surface of the negative electrode in five lithium ion secondary batteries is shown in Table 1.

As shown in Table 1, when Examples 1 to 5 having the same firing conditions were compared with Comparative Example 1, each of the Examples showed a higher initial charge capacity. Further, each of the examples shows a case where the initial discharge capacity is increased while the initial charge capacity is increased, and the occluded lithium ions are reversibly released. As a result, in Examples 1 to 5, the charge and discharge efficiency was higher than that of Comparative Example 1.

Further, in Example 9, the improvement in battery characteristics was also confirmed.

Examples 1, 2, and 4 to 6 using a novolac type phenol resin as a phenolic hydroxyl group-containing resin remarkably exhibited an improvement in charge and discharge efficiency.

The surface area per unit volume of the carbon materials of Examples 1 to 7 was in the range of 10000 cm ² /cm ³ or more and 16,000 cm ² /cm ³ or less, showing good low-temperature characteristics. Among them, the carbon materials of Examples 1 to 6 having a surface area per unit volume of 12,000 cm ² /cm ³ or more exhibited particularly excellent low-temperature characteristics.

The mean square radius of the carbon materials of the third embodiment and the seventh embodiment is included in the range of 1 μm ² or more and 4 μm ² or less, thereby preventing deterioration of self-discharge in a high-temperature environment, and it is expected to exhibit good properties against the current collector. Coating properties.

The true specific gravity of the carbon materials of Examples 1, 2, 4, and 6 to 8 was in the range of 1.5 g/cm ³ or more and 1.7 g/cm ³ or less. Therefore, the value of the charge and discharge capacity of the secondary battery negative electrode formed using these is stable, and it is expected to contribute to the life characteristics of the secondary battery.

High temperature storage according to lithium ion secondary batteries using the respective examples and comparative examples The characteristic evaluation showed higher high temperature storage characteristics of more than 80%. In particular, in the examples, the high-temperature storage characteristics were 85% or more, and even when stored at a high temperature of about 60 ° C, it was shown that the discharge capacity before storage was maintained at a very high ratio. As a result, the carbon material for a secondary battery negative electrode of the present invention contained in the negative electrode can maintain a favorable carbon structure even in a high-charge state in a high-temperature environment. It is presumed that the self-discharge of lithium occluded in the carbon material and the formation of a film on the surface of the negative electrode are hard to be generated by the maintenance of the carbon structure, so that the secondary battery of the present invention can be maintained at a high level in a high temperature environment. Lithium occlusion of the negative electrode is released.

Moreover, according to the evaluation of the high-temperature life characteristics of the lithium ion secondary batteries using the respective examples and comparative examples, high-temperature storage characteristics of 80% or more were exhibited. In particular, the high-temperature life characteristics of the examples were all 85% or more, and even when it was repeatedly used at a high temperature of about 55 ° C, it was shown that the discharge capacity can be maintained at a very high ratio. Thus, it is revealed that the negative electrode containing the carbon material for a secondary battery negative electrode of the present invention is excellent in cycle characteristics in a high temperature environment.

In addition, the lithium ion secondary batteries of the respective examples and comparative examples were decomposed after the evaluation of the high-temperature life characteristics. As a result, lithium deposition of the lithium ion secondary battery of the example was not observed on the negative electrode. On the other hand, in the lithium ion secondary battery of the comparative example, it was confirmed that lithium was deposited on the negative electrode at a ratio of 20% (specifically, one of five). As a result, the carbon material for a secondary battery negative electrode of the present invention contained in the negative electrode can maintain the structure of the carbon structure and the negative electrode plate satisfactorily even when it is repeatedly used in a high-temperature environment. It is presumed that by the maintenance of the structure of the carbon structure and the negative electrode plate, the negative electrode of the present invention can reduce the change in electrical resistance at a higher level in the storage and release of lithium at a high temperature, and as a result, precipitation of lithium is suppressed.

<Example 10>

100 parts of phenol, 100 parts of p-xylylene dimethyl ether, and 0.1 part of diethyl sulfate were placed in a three-necked flask equipped with a stirrer and a cooling tube, and dehydration reaction was carried out for 3 hours in a range of 140 ° C or more and 160 ° C or less. Add calcium hydroxide for neutralization. Thereafter, the temperature was dehydrated to obtain 120 parts of a phenol aralkyl resin as a resin containing a modified phenolic hydroxyl group.

The hydroxyl equivalent of the phenol aralkyl resin obtained by the above method was measured in accordance with JIS K 0070 (1992) and titration, and found to be 175 g/eq.

The phenol aralkyl resin obtained by the above method was heated at room temperature under a nitrogen atmosphere at a temperature increase rate of 100 ° C / hr. After reaching 550 ° C, the calcination state was maintained for 1.5 hours to carry out carbonization treatment (first burning) Into the steps). Thereafter, a pulverization step is carried out to obtain a carbon material precursor.

The carbon material precursor 204g obtained by the above method was expanded and allowed to stand in a heat treatment furnace of 24 L (40 cm in length, 30 cm in width, 20 cm in height) in a furnace having a thickness as thin as possible, under a nitrogen atmosphere. The temperature increase rate of 100 ° C / hr was calcined from room temperature to 1200 ° C, and then the calcination state was maintained for 2 hours to carry out carbonization treatment (second baking step). The carbon material for secondary batteries obtained above was used as Example 10.

Further, the pulverization conditions of the above pulverization step in Example 10 are as follows. Other Examples and Comparative Examples The pulverization step was also carried out between the first baking step and the second firing step under the pulverization conditions described below.

<Example 11>

100 parts of phenol resin, 70 parts of NIKANOL H (manufactured by Fudow Co., Ltd.) as a xylene resin, and 1 part of 25% sulfuric acid were placed in a three-necked flask equipped with a stirrer and a cooling tube. The reaction was carried out at reflux temperature for 2 hours. Then, 48 parts of a 37% aqueous solution of Formalin was added successively and reacted for 2 hours. Thereafter, calcium hydroxide was added for neutralization, and the temperature was dehydrated to obtain 160 parts of a xylene-modified phenol resin as a resin containing a modified phenolic hydroxyl group.

The hydroxyl equivalent of the xylene-modified phenol resin obtained by the above method was measured in the same manner as in Example 10, and found to be 155 g/eq.

The first baking step and the second baking step were carried out in the same manner as in the above-described Example 10 except that the xylene-modified phenol resin obtained by the above method was used, and the carbonization treatment was carried out. The carbon material for secondary batteries obtained above was used as Example 11.

<Comparative Example 2>

100 parts of phenol, 64.5 parts of 37% formaldehyde aqueous solution, and 3 parts of oxalic acid were placed in a three-necked flask equipped with a stirrer and a cooling tube, and reacted at 100 ° C for 3 hours, and then heated and dehydrated to obtain 90 parts of a novolac type phenol resin.

The hydroxyl equivalent of the novolac type phenol resin obtained by the above method was measured in the same manner as in Example 10, and found to be 105 g/eq.

The first baking step and the second baking step were carried out in the same manner as in the above-described Example 10 except that the novolac type phenol resin obtained by the above method was used. The carbon material for secondary batteries obtained above was used as Comparative Example 2.

<Comparative Example 3>

In the same manner as in the above-described Example 10, except that 10 parts of triphenyl phosphate and 3 parts of hexamethylenetetramine were added to 100 parts of the novolak-type phenol resin obtained in the same manner as in Comparative Example 2, The first baking step and the second baking step perform carbonization treatment. The carbon material for secondary batteries obtained above was used as Comparative Example 3.

Further, the pulverization step in each of the examples and the comparative examples was carried out under the following pulverization conditions using the fired product obtained in the first baking step. The carbon precursor obtained by the pulverization step is supplied to the second firing step.

Example 10: The intermediate obtained by carrying out the first baking step was naturally placed and cooled to room temperature, and placed in a ball mill pulverizing device. 15mm alumina ball 5000g and A 10 mm alumina ball was placed in a container of 900 g to obtain a pulverized intermediate. Then, the above-mentioned pulverized intermediate was passed through a sieve of 75 μm mesh to remove coarse particles, thereby obtaining a pulverized material (carbon precursor).

Example 11: A pulverization step was carried out under the same conditions as in Example 10 to obtain a pulverized material (carbon precursor).

Comparative Example 2: A pulverization step was carried out under the same conditions as in Example 10 to obtain a pulverized material (carbon precursor).

Comparative Example 3: The intermediate obtained by carrying out the first baking step was naturally placed and cooled to room temperature, and a pulverizing apparatus was used in a cyclone mill at a powder supply amount of 50 g/min, an air volume of 0.5 m ³ /min, and a first crushing impeller. The pulverization intermediate was obtained by pulverizing under the conditions of a rotation speed of 15,000 rpm and a second pulverization impeller rotation speed of 15,000 rpm. Then, the pulverized intermediate was passed through a sieve having a mesh size of 75 μm to remove coarse particles to obtain a pulverized material (carbon precursor).

Further, the pulverizing apparatus used in the above pulverization treatment is as follows.

The ball mill pulverizing device uses a rotary ball mill (1 segment-B, supplied by Jinjiang Chamber of Commerce Co., Ltd.).

The cyclone mill pulverizing apparatus was a dry pulverizer (150 BMW type cyclone mill, manufactured by Shizuoka Plant Co., Ltd.).

[Measurement of surface area]

The measurement of the surface area was carried out in the same manner as described above. The calculated values are shown in Table 2.

<Production of a half-cell type lithium ion secondary battery>

The production of the half-cell type lithium ion secondary battery was carried out in the same manner as described above.

[Evaluation of initial charge and discharge characteristics]

Using the half-cell type lithium ion secondary battery fabricated by the above method, battery characteristics were evaluated by two evaluation methods in which the measurement conditions were changed as follows.

In the evaluation of the initial charge and discharge characteristics, "charging" means that lithium ions are moved from a working electrode made of metallic lithium to a negative electrode formed using a carbon material by applying a voltage. In addition, "discharge" means a phenomenon in which lithium ions are moved from a negative electrode composed of a carbon material to a working electrode made of metallic lithium.

(Battery characteristics evaluation 1)

The measurement temperature was set to 25 ° C, and the current density during charging was set to 25 mA/g for constant current charging. From the time point when the potential reached 0 V, constant voltage charging was performed while maintaining 0 V, and charging was performed until the current density became 2.5 mA/g. Up to now, the above electric quantity is used as the initial charging capacity.

Then, the current density at the time of discharge was set to 25 mA/g, and constant current discharge was performed, and the amount of electricity at the time point when the potential reached 2.5 V was used as the initial discharge capacity.

The initial charge and discharge efficiency is calculated by multiplying the value obtained by dividing the initial discharge capacity by the initial charge capacity by 100 as shown in the following formula (2). In addition, the result of the evaluation of the initial charge and discharge characteristics is shown in Table 2.

Initial charge and discharge efficiency (%) = [first discharge capacity (mAh / g) / initial charge capacity (mAh/g)]×100 (2)

(Battery characteristics evaluation 2)

The measurement temperature was set to 25 ° C, and the current density at the time of charging was set to 40 mA/g for constant current charging. From the time point when the potential reached 0 V, constant voltage charging was performed while maintaining 0 V, and charging was performed until the current density became 4.0 mA/ The amount of electricity up to g is used as the initial charge capacity.

Then, the current density at the time of discharge was set to 4.0 mA/g to perform constant current discharge, and the amount of electricity at the time point when the potential reached 1.5 V was used as the initial discharge capacity.

The initial charge and discharge efficiency in the battery characteristic evaluation 2 was calculated using the above formula (2). In addition, the result of the evaluation of the initial charge and discharge characteristics is shown in Table 2.

<Production of full-cell type lithium ion secondary battery>

The production of the all-cell type lithium ion secondary battery was carried out in the same manner as described above.

[Low temperature environmental test]

The low temperature environmental test was carried out in the same manner as described above.

Regarding the above-described low-temperature environmental discharge treatment, the current value is plotted on the horizontal axis, and the voltage after charging or discharging for 10 seconds on the vertical axis is plotted, and the charging time and the discharge time in the battery are determined based on the absolute value of the slope of the approximate straight line. DC resistance (DC-IR), and based on this value, the low-temperature environmental characteristics were evaluated in the following manner. Lower DC-IR means less resistance and good output characteristics.

The DC resistance during charging is 195 Ω or less, and/or the DC resistance during discharge is 215 Ω or less...... ◎

The DC resistance during charging exceeds 195 Ω and is 210 Ω or less, and the DC resistance during discharge exceeds 215 Ω and is 220 Ω or less... ○

The DC resistance during charging exceeds 210Ω, and/or the DC resistance during discharge exceeds 220. Ω...△

As shown in Table 2, in Examples 10 and 11, compared with Comparative Example 2, the improvement in charge and discharge efficiency was confirmed in the battery characteristics evaluation under both conditions. In Examples 10 and 11, the improvement of the charge and discharge efficiency was remarkably confirmed in the evaluation 2 of the higher current, and it was revealed that the resin containing the modified phenolic hydroxyl group for the negative electrode of the secondary battery of the present invention can be preferably applied. High current equipment.

Further, the charge and discharge capacity of Example 10 using a phenol aralkyl resin also showed a moderate value, and the charge and discharge efficiency was high, showing that a negative electrode having a balanced battery performance can be provided.

Further, in Example 11 using a xylene-modified phenol resin, it was confirmed that the improvement in charge and discharge efficiency was remarkable.

The surface area per unit volume of the carbon material of each of the examples was in the range of 10000 cm ² /cm ³ or more and 16,000 cm ² /cm ³ or less, showing particularly excellent low-temperature characteristics. In Comparative Example 3, since the conditions were optimized by adding an additive to the carbon material, the charge and discharge efficiency in the battery property evaluations 1 and 2 was improved as compared with Comparative Example 2, but excellent evaluation was not obtained in the evaluation of the low-temperature characteristics. On the other hand, the examples showed satisfactory evaluations in charge and discharge efficiency and low-temperature characteristics evaluation, and exhibited balanced battery performance in a normal temperature environment and a low temperature environment.

<Synthesis of phenolic hydroxyl-containing resin>

First, the novolac type phenol resin used in the examples or the comparative examples was synthesized in the following manner.

100 parts of phenol, 64.5 parts of 37% formaldehyde aqueous solution, and 3 parts of oxalic acid were placed in a three-necked flask equipped with a stirrer and a cooling tube, and reacted at 100 ° C for 3 hours, and then heated and dehydrated to obtain 90 parts of a novolac type phenol resin. The hydroxyl equivalent of the novolac type phenol resin obtained by the above method was measured in accordance with JIS K 0070 (1992) and titration, and found to be 105 g/eq.

<Example 12>

With respect to 100 parts of the novolac type phenol resin obtained by the above-described method, 10 parts of triphenyl phosphate (manufactured by Daiha Chemical Industry Co., Ltd., trade name: TPP) and hexamethylenetetramine 3 were used by a vibration ball mill. The granules were pulverized and mixed to obtain a resin composition.

The resin composition obtained above was heated from room temperature at a temperature elevation rate of 100 ° C / hr in a nitrogen atmosphere to a temperature of 550 ° C, and then the calcination state was maintained for 1.5 hours to carry out carbonization treatment (first baking step). Thereafter, a pulverization step is carried out to obtain a carbon material precursor.

The carbon material precursor was fired at room temperature at a temperature elevation rate of 100 ° C / hr in a nitrogen atmosphere to a temperature of 1200 ° C, and then the carbonized state was maintained for 2 hours to carry out carbonization treatment (second baking step). The carbon material thus obtained was taken as Example 12.

Further, the pulverization conditions of the above pulverization step in Example 12 are as follows. Other Examples and Comparative Examples The pulverization step was also carried out between the first baking step and the second firing step under the pulverization conditions described below.

<Example 13>

A carbon material was produced in the same manner as in the above-mentioned Example 12 except that the blending amount of triphenyl phosphate was changed to 5 parts, and this was designated as Example 13.

<Example 14>

In the second firing step, a carbon material was produced in the same manner as in the above-described Example 12 except that the holding time in the fired state at 1200 ° C was changed to 4 hours, and this was designated as Example 14.

<Example 15>

The resin composition was prepared in the same manner as in Example 12, and the first firing was carried out under the same conditions as in Example 12 except that the pulverization conditions were different from those in the pulverization conditions of Example 12 as described below. Step and second firing step. The carbon material thus obtained was taken as Example 15.

<Comparative Example 4>

100 parts of the novolac type phenol resin obtained by the above-mentioned method was heated up from room temperature in the nitrogen atmosphere, and it was set to the 550 degreeC, and the baking state was hold|maintained for 1.5 hours, and the carbonization process was carried out. a firing step). Thereafter, a pulverization step is carried out to obtain a carbon material precursor.

The carbon material precursor was calcined at room temperature of 1200 ° C at a temperature elevation rate of 100 ° C / hr in a nitrogen atmosphere, and then the carbonized state was maintained for 2 hours in a calcined state (second baking step). The carbon material thus obtained was designated as Comparative Example 4.

<Comparative Example 5>

To 100 parts of the novolac type phenol resin, 5 parts of triphenyl phosphate and 5 parts of hexamethylenetetramine were used, and the mixture was pulverized and mixed by a vibration ball mill to obtain a resin composition.

A carbon material was produced by the same method as Comparative Example 4 described above, except that 100 parts of the novolac type phenol resin used in Comparative Example 4 was used instead of the above resin composition, and this was designated as Comparative Example 5.

Further, the pulverization step in each of the examples and the comparative examples was carried out under the following pulverization conditions using the fired product obtained in the first baking step. The carbon before the pulverization step The drive is supplied to the second firing step.

Example 12: The intermediate obtained by carrying out the first baking step was naturally placed and cooled to room temperature, and placed in a ball mill pulverizing device. 15mm alumina ball 5000g and A 10 mm alumina ball was placed in a container of 900 g to obtain a pulverized intermediate. Then, the pulverized intermediate was passed through a sieve of 75 μm mesh to remove coarse particles, thereby obtaining a pulverized material (carbon precursor).

Example 13: A pulverization step was carried out under the same conditions as in Example 12 to obtain a pulverized material (carbon precursor).

Example 14: The intermediate obtained by carrying out the first baking step was naturally placed and cooled to room temperature, and the apparatus was pulverized using a cyclone mill at a powder supply amount of 30 g/min, an air volume of 0.8 m ³ /min, and a first crushing impeller. The pulverization intermediate was obtained by pulverizing under the conditions of a rotation speed of 13,000 rpm and a second pulverization impeller rotation speed of 13,000 rpm. Then, the pulverized intermediate was passed through a sieve of 75 μm mesh to remove coarse particles, thereby obtaining a pulverized material (carbon precursor).

Example 15: The intermediate obtained by carrying out the first baking step was naturally placed and cooled to room temperature, and the apparatus was pulverized using a cyclone mill at a powder supply amount of 50 g/min, an air volume of 0.5 m ³ /min, and a first crushing impeller. The pulverization intermediate was obtained by pulverizing under the conditions of a rotation speed of 15,000 rpm and a second pulverization impeller rotation speed of 15,000 rpm. Then, the pulverized intermediate was passed through a sieve of 75 μm mesh to remove coarse particles, thereby obtaining a pulverized material (carbon precursor).

Comparative Examples 4 and 5: The pulverization step was carried out under the same conditions as in Example 12 to obtain a pulverized material (carbon material precursor).

Further, the pulverizing apparatus used in the above pulverization treatment is as follows.

The ball mill crushing device uses a rotary ball mill (1 segment-B, Jinjiang Chamber of Commerce Co., Ltd. Provided by the company).

The cyclone mill pulverizing apparatus was a dry pulverizer (150 BMW type cyclone mill, manufactured by Shizuoka Plant Co., Ltd.).

[Carbon material evaluation]

(phosphorus content)

Each of the examples and comparative examples obtained in the above manner was dissolved in hydrochloric acid to prepare a sample, and the phosphorus contained in the sample was quantified using a high frequency inductively coupled plasma (ICP) luminescence analyzer. The quantitative results are shown in Table 3.

(carbon dioxide adsorption amount)

Each of the examples and comparative examples obtained in the above manner was supplied to a gas adsorption measuring device (manufactured by NIPPON BEL Co., Ltd., BELSORP-max) to measure the amount of carbon dioxide adsorbed in the carbon material. 0.5 g of the measurement sample was placed in a sample tube for measurement, and dried under reduced pressure at 200 ° C for 2 hours, and then the amount of adsorption of carbon dioxide was measured. The measurement temperature was set to 25 ° C, carbon dioxide was introduced into the sample tube, and the adsorption amount of carbon dioxide until the equilibrium pressure in the sample tube reached 110 KPa was determined by a constant volume method. The measurement results are shown in Table 3.

(measurement of true specific gravity)

With respect to each of the examples and comparative examples obtained in the above manner, the true specific gravity was measured by a true specific gravity measuring method using butanol. The measurement results are shown in Table 3.

(Measurement of surface area)

The measurement of the surface area was carried out in the same manner as described above. The calculated values are shown in Table 3.

<Production of a half-cell type lithium ion secondary battery>

The production of the half-cell type lithium ion secondary battery was carried out in the same manner as described above.

[Evaluation of initial charge and discharge characteristics]

The evaluation of the initial charge and discharge characteristics was carried out in the same manner as described above. The initial charge and discharge efficiency is calculated by multiplying the value obtained by dividing the initial discharge capacity by the initial charge capacity by 100 as shown in the following formula (3). In addition, the result of the evaluation of the initial charge and discharge characteristics is shown in Table 3.

Initial charge and discharge efficiency (%) = [first discharge capacity (mAh / g) / initial charge capacity (mAh / g)] × 100 (3)

As shown in Table 3, it was confirmed that any of the examples showed a phosphorus content in a specific range specified by the present invention and a carbon dioxide adsorption amount which did not reach a specific value. On the other hand, it was confirmed that the phosphorus content in Comparative Example 4 was lower than the lower limit of the specific range, and the amount of adsorption of carbon dioxide was significantly higher than a specific value. Further, in Comparative Example 5, although the phosphorus content was in a specific range, the carbon dioxide adsorption amount was a specific value or more.

In the evaluation of the battery characteristics using the respective examples, both the first initial charge capacity and the initial discharge capacity were exhibited. The charge and discharge efficiencies exhibited by the respective examples were remarkably higher than those of the respective comparative examples. Thus, the carbon materials of the examples all showed excellent occlusion release of chemical species such as lithium ions.

<Production of full-cell type lithium ion secondary battery>

The production of the all-cell type lithium ion secondary battery was carried out in the same manner as described above.

[Low temperature environmental test]

The low temperature environmental test was carried out in the same manner as described above.

Regarding the above-described low-temperature environmental discharge treatment, the current value is plotted on the horizontal axis, and the voltage after charging or discharging for 10 seconds on the vertical axis is plotted, and the charging time and the discharge time in the battery are determined based on the absolute value of the slope of the approximate straight line. DC resistance (DC-IR), and according to this value is as follows The method evaluates the low temperature environmental characteristics. Lower DC-IR means less resistance and good output characteristics.

The DC resistance during charging is 195 Ω or less, and/or the DC resistance during discharge is 215 Ω or less...... ◎

The DC resistance during charging exceeds 195 Ω and is 210 Ω or less, and the DC resistance during discharge exceeds 215 Ω and is 220 Ω or less... ○

The DC resistance during charging exceeds 210Ω, and/or the DC resistance during discharge exceeds 220Ω...△

[Composition of target compound]

The P content-converted phosphorus content and the C-converted carbon content in the surface of Example 12 were measured by XPS, and the composition ratios P/C of these were determined and shown in Table 4.

Further, the target compound in the surface of Example 12 was examined by XPS. The composition ratio of each phosphorus compound and reduced phosphorus is shown in Table 4 with respect to 100% of the composition of all the target compounds detected.

As shown in Table 4, it was confirmed that in the example 12, triphenylphosphine ((C ₆ H ₅ ) ₃ P(=O)), triphenylphosphine ((C ₆ H ₅ ) ₃ P), The total composition ratio of the reduced phosphorus is 50% or more, and the composition ratio of the reduced phosphorus is more than 0% and 13% or less.

[Composition analysis of carbon materials]

XPS:

For the carbon material precursor of Example 12 and Example 12, the elements of the surface were quantified in the following manner. That is, the contents of carbon, oxygen, phosphorus, and nitrogen on the surface of the carbon material precursor and Example 12 were measured by XPS, and the composition ratio of each element to the whole was determined. The results are shown in Table 5.

Composition analysis:

For the carbon material precursor of Example 12 and Example 12, the elements of the main body were quantified in the following manner. That is, the contents of carbon, hydrogen, nitrogen, oxygen, and phosphorus contained in the carbon material precursor and the main body of Example 12 were quantified by composition analysis as shown below, and the composition of each element with respect to the whole was determined. ratio. The results are shown in Table 5.

Carbon, hydrogen, and nitrogen were quantified by an oxygen cycle combustion or gas chromatography using an elemental analysis device (manufactured by Sumitomo Analytical Co., Ltd., NCH-22F elemental analysis device). Specifically, Example 12 was completely burned at about 850 ° C to generate CO ₂ gas and H ₂ O gas, and carbon and hydrogen were quantified by gas chromatography. Further, nitrogen was reduced after combustion to form nitrogen gas (N ₂ ), which was also quantified by gas chromatography.

The oxygen system was quantified by a heat-melting or non-dispersive infrared absorption method using an oxygen-containing analyzer (Jumbo Co., Ltd., EMGA 920 oxygen analyzer). Specifically, Example 12 was heated in a helium atmosphere at about 2500 ° C to generate CO gas and CO ₂ gas, and infrared detection was performed.

Phosphorus is quantified by ashing, acid dissolution, and high frequency inductively coupled plasma luminescence spectrometry. Specifically, after ashing Example 12, it was dissolved in hydrochloric acid, and phosphorus was quantified by a high-frequency inductively coupled plasma luminescence spectroscopic analyzer.

As a result of the above XPS and composition analysis, it was confirmed that the composition ratio of carbon in the surface or the main body of Example 12 was more than 96%, and carbon was the main component. From the results shown in Table 5, it was confirmed that with respect to the composition ratio O/C of oxygen to carbon, the composition of the surface detected by XPS was relatively large, and the ratio of oxygen in the surface of Example 12 was higher than that of the host. In other words, the body of Example 12 has a higher carbon ratio than the surface.

As shown in Table 5, Example 12 shows X-ray photoelectron spectroscopy The composition ratio P (XPS) of phosphorus detected by (XPS) is larger than the composition ratio P (COMP) of phosphorus detected by compositional analysis. Further, although the composition ratio P(COMP) is smaller than the composition ratio P (XPS), it shows a remarkable value, and in Example 12, phosphorus is not only remarkably present on the surface but also remarkably exists in the main body.

The surface area per unit volume of the carbon materials of Examples 12, 13 and 15 was in the range of 10000 cm ² /cm ³ or more and 16,000 cm ² /cm ³ or less, showing good low-temperature characteristics. Among them, the carbon materials of Examples 12 and 13 having a surface area per unit volume of 12,000 cm ² /cm ³ or more exhibited particularly excellent low-temperature characteristics.

The mean square radius of the carbon material of the fifteenth embodiment is included in the range of 1 μm ² or more and 4 μm ² or less, thereby preventing deterioration of self-discharge in a high-temperature environment, and it is expected to exhibit good coatability to the current collector.

The true specific gravity of the carbon materials of Examples 12 to 15 was in the range of 1.5 g/cm ³ or more and 1.7 g/cm ³ or less. Therefore, the value of the charge and discharge capacity of the secondary battery negative electrode formed using these is stable, and it is expected to contribute to the life characteristics of the secondary battery.

[Evaluation of high temperature storage characteristics]

The high-temperature storage characteristics were evaluated in the same manner as described above using the all-cell type lithium ion secondary batteries of the respective examples and comparative examples produced as described above.

The high temperature storage characteristics of each of the examples and the comparative examples are shown in Table 3.

[Evaluation of high temperature life characteristics]

The evaluation of the high-temperature life characteristics was carried out in the same manner as described above.

The high temperature life characteristics of each of the examples and the comparative examples are shown in Table 3.

[Decomposition evaluation of lithium ion secondary battery after high temperature life test]

The decomposition evaluation of the lithium ion secondary battery after the high-temperature life test was carried out in the same manner as described above.

In each of the examples and the comparative examples, the number of lithium ion secondary batteries in which lithium was precipitated on the surface of the negative electrode in the five lithium ion secondary batteries is shown in Table 3.

According to the evaluation of the high-temperature storage characteristics of the lithium ion secondary batteries using the respective examples and the comparative examples, high-temperature storage characteristics of 80% or more were exhibited. In particular, in the examples, the high-temperature storage characteristics were 85% or more, and even when stored at a high temperature of about 60 ° C, it was shown that the discharge capacity before storage was maintained at a very high ratio. As a result, the carbon material for a secondary battery negative electrode of the present invention contained in the negative electrode can maintain a favorable carbon structure even in a high-charge state in a high-temperature environment. It is presumed that the self-discharge of lithium occluded in the carbon material and the formation of a film on the surface of the negative electrode are hard to be generated by the maintenance of the carbon structure, so that the secondary battery of the present invention can be maintained at a high level in a high temperature environment. Lithium occlusion of the negative electrode is released.

Moreover, according to the evaluation of the high-temperature life characteristics of the lithium ion secondary batteries using the respective examples and the comparative examples, high-temperature storage characteristics of 80% or more were exhibited. In particular, the high-temperature life characteristics of the examples were all 85% or more, and even when it was repeatedly used at a high temperature of about 55 ° C, it was shown that the discharge capacity can be maintained at a very high ratio. Thus, it is revealed that the negative electrode containing the carbon material for a secondary battery negative electrode of the present invention is excellent in cycle characteristics in a high temperature environment.

Further, after the evaluation of the high-temperature life characteristics, the lithium ion secondary batteries of the respective examples and the comparative examples were decomposed. As a result, the lithium ion secondary battery of the example did not confirm the precipitation of lithium on the surface of the negative electrode. On the other hand, in the lithium ion secondary battery of the comparative example, it was confirmed that lithium was deposited on the surface of the negative electrode at a ratio of 20% (specifically, one of five). This result also shows that the carbon material for a secondary battery negative electrode of the present invention contained in the negative electrode can be satisfactorily even when it is repeatedly used in a high temperature environment. Maintain the structure of the carbon structure and the negative plate. It is presumed that by the maintenance of the structure of the carbon structure and the negative electrode plate, the negative electrode of the present invention can reduce the change in electrical resistance at a higher level in the storage and release of lithium at a high temperature, and as a result, precipitation of lithium is suppressed.

The above embodiment includes the following technical ideas.

(1) A resin composition for a secondary battery negative electrode comprising: a phenolic hydroxyl group-containing resin having a hydroxyl group equivalent of 300 g/eq or less, and a self-condensation temperature of a resin having a boiling point temperature or a thermal decomposition temperature exceeding the phenolic hydroxyl group-containing resin; Phosphate or phosphoric acid derivative.

(2) The resin composition for a secondary battery negative electrode according to the above aspect, wherein the phosphoric acid is contained in an amount of 3 parts by mass or more and 15 parts by mass or less based on 100 parts by mass of the phenolic hydroxyl group-containing resin. Ester or the above-mentioned phosphoric acid derivative.

(3) The resin composition for a secondary battery negative electrode according to the above (1), wherein the melting point of the phosphate or the phosphoric acid derivative does not reach the above-mentioned phenolic hydroxyl group-containing resin. Condensation temperature.

(4) The resin composition for a secondary battery negative electrode according to the above (3), wherein the melting point of the phosphate ester or the phosphoric acid derivative and the melting point of the phenolic hydroxyl group-containing resin are both higher than normal temperature and 250 ° C or lower.

(5) The resin composition for a secondary battery negative electrode according to the above (4), wherein a melting start temperature of the phosphate or the phosphoric acid derivative does not reach a melting end temperature of the phenolic hydroxyl group-containing resin.

(6) The resin composition for a secondary battery negative electrode according to any one of the above (1), further comprising a curing agent, and

The phenolic hydroxyl group-containing resin is a novolac type phenol resin.

(7) The resin composition for a secondary battery negative electrode according to any one of the above aspects, wherein the phosphate ester is a phosphate triester.

(8) The resin composition for a secondary battery negative electrode according to the above (7), wherein the phosphate triester is triphenyl phosphate or the triphenyl phosphate derivative.

(9) The resin composition for a secondary battery negative electrode according to the above (8), wherein the triphenyl phosphate derivative is a compound represented by the following chemical formula (1).

[(CH ₃ ) ₂ C ₆ H ₃ O] ₂ P(O)OC ₆ H ₄ OP(O)[OC ₆ H ₃ (CH ₃ ) ₂ ] ₂ (1)

(10) A method for producing a carbon material for a secondary battery negative electrode, which is a secondary battery negative electrode carbon material produced by using the resin composition for a secondary battery negative electrode according to any one of the above (1) to (9) And a method of firing a resin composition for a secondary battery negative electrode to produce a carbon material precursor by firing a resin composition having a maximum temperature of less than 1000 ° C at the time of firing; In the second baking step, the carbon material precursor produced in the first baking step is fired at a firing temperature at a temperature at which the maximum temperature at the time of firing is 1000 ° C or higher, thereby producing a carbon material.

(11) The method for producing a carbon material for a secondary battery negative electrode according to the above aspect, wherein the first baking step includes: a melting step of causing the phenol containing the resin composition for a secondary battery negative electrode The hydroxyl group-containing resin and the above-mentioned phosphate ester or the above-mentioned phosphoric acid derivative are melted; and the carbon material precursor is formed to form a crystallite containing carbon of a degreased and/or graphene-like structure.

(12) A carbon material for a secondary battery negative electrode, which is produced by using the resin composition for a secondary battery negative electrode according to any one of the above (1) to (9), which contains The surface area per unit volume obtained from the particle size distribution based on the number of particles is a carbon particle in a range of 10000 cm ^-1 or more and 16,000 cm ^-1 or less.

(13) The carbon material for a secondary battery negative electrode according to the above (12), wherein the carbon particles have a mean square radius determined from the particle diameter distribution of 1 μm ² or more and 4 μm ² or less.

(14) The carbon material for a secondary battery negative electrode according to the above (12), wherein the carbon particles have a true specific gravity of 1.5 g/cm ³ or more and 1.7 g/cm ³ or less.

The carbon material for a secondary battery negative electrode according to any one of the above-mentioned (12), wherein the carbon particles include an X-ray diffraction method using a CuK α ray as a radiation source. The hard surface of the (002) plane having an average surface spacing d002 of 0.340 nm or more.

(16) The carbon material for a secondary battery negative electrode according to the above (15), wherein the carbon particles contain 90% by mass or more of the hard carbon.

(17) The carbon material for a secondary battery negative electrode according to the above (15), wherein the carbon particles contain the hard carbon and graphite.

(18) The carbon material for a secondary battery negative electrode according to any one of the above (12) to (17), which is used for a secondary battery negative electrode, and is stored at a high temperature as shown in the following high-temperature storage property evaluation. The high-temperature storage characteristic evaluation is performed by using a secondary battery negative electrode including a secondary battery negative electrode carbon material, a positive electrode, an electrolyte containing a dissolved electrolyte, and a separator. The battery is subjected to an aging treatment for performing a specific charge and discharge cycle for 5 cycles, and the discharge capacity at the time of discharge in the fifth cycle of the charge and discharge cycle is measured, and the discharge capacity I is used, and the above-described aging treatment is used. A lithium ion secondary battery is charged with a current density of 25 mA/g for constant current charging, and is kept at a constant voltage of 4.2 V from a time point when the potential reaches 4.2 V, and is charged until the current density reaches 2.5 mA/g. In the lithium ion secondary battery in which the state of charge is adjusted to 100%, the lithium ion secondary battery having the above state of charge of 100% is stored in a dryer whose temperature is adjusted to 60 ° C. After the above-mentioned storage, the lithium ion secondary battery was used, and charged and discharged at a current value of 0.2 C, and a total of three cycles of charge and discharge were performed as one cycle, and the discharge of the third cycle was measured. The discharge capacity was set to the discharge capacity II, and the high-temperature storage characteristics were calculated according to the following formula (4).

High-temperature storage characteristics (%) = [discharge capacity II (mAh / g) / discharge capacity I (mAh / g)] × 100 (4)

(19) The carbon material for a secondary battery negative electrode according to any one of the above (12) to (18), which is used for a secondary battery negative electrode, and exhibits a high temperature life in the following high-temperature life characteristic evaluation. The high-temperature life characteristic evaluation is a lithium ion secondary battery including a secondary battery negative electrode including a carbon material for a secondary battery negative electrode, a positive electrode, an electrolyte containing a dissolved electrolyte, and a separator. The aging treatment is performed for 5 cycles of a specific charge and discharge cycle, and the lithium ion secondary battery after the aging treatment described above is charged to 4.2 V at a constant current of 1 C in a temperature environment of 55 ° C, and thereafter, at 4.2 ° The constant voltage of V is charged until the current value is attenuated to 0.02 C, and then maintained at a temperature of 55 ° C for 30 minutes, and then discharged to 2.5 V at a constant current of 1 C, and the discharge capacity is measured to be the discharge capacity III, and thereafter The battery was kept at a temperature of 55 ° C for 30 minutes, and the above-described charge and discharge cycle was carried out as one cycle. Then, the charge and discharge cycle was further carried out for 99 cycles, and a total of 100 cycles of charge and discharge were performed. Ring, and measuring the discharge of 100 cycles of the discharge capacity to the discharge capacity IV, high-temperature life characteristics according to (5) calculated from the following equation.

High-temperature life characteristics (%) = [discharge capacity IV (mAh / g) / discharge capacity III (mAh / g)] × 100 (5)

(20) The secondary battery negative electrode active material according to any one of the above (12) to (19).

(21) A secondary battery negative electrode comprising: a secondary battery negative electrode active material layer containing the secondary battery negative electrode active material according to (20); and a negative electrode in which the secondary battery negative electrode active material layer is laminated Use a current collector.

(22) A secondary battery comprising the secondary battery negative electrode, the electrolyte, and the secondary battery positive electrode according to (21) above.

(23) A resin containing a modified phenolic hydroxyl group for a negative electrode of a secondary battery, which has a hydroxyl equivalent of 115 g/eq or more.

(24) The resin containing a modified phenolic hydroxyl group for a negative electrode for a secondary battery according to the above (23), which comprises a structure represented by the following formula (4),

(In the formula (4), P represents a structure containing a phenolic hydroxyl group, and A and B represent any atom or group of atoms constituting a main chain of a resin containing a modified phenolic hydroxyl group, and X represents an arbitrary aryl group, n Is an integer greater than 1).

(25) The resin containing a modified phenolic hydroxyl group for a negative electrode of a secondary battery according to the above (24), wherein the above formula (4) is a compound of the following formula (5),

(In the formula (5), X ₁ to X ₄ each independently represent a substituent or a hydrogen atom of the benzene nucleus).

(26) as described (25) of the negative electrode of the secondary battery according to the resin containing the modified phenolic hydroxyl groups, wherein, in the general formula (5) in the above X ₁ to X ₄ in the above any one or more of A base.

(27) The modified phenolic hydroxyl group-containing resin for a secondary battery negative electrode according to the above (26), wherein the X ₁ and the X ₂ in the above formula (5) are both methyl groups, and the above two One methyl group is at a meta position separated by one carbon atom.

(28) The modified phenolic hydroxyl group-containing resin for a secondary battery negative electrode according to any one of the above (23), wherein the secondary battery negative electrode contains a modified phenolic hydroxyl group-containing resin It is a phenol aralkyl resin.

The modified phenolic hydroxyl group-containing resin for a secondary battery negative electrode according to any one of the above-mentioned (23), wherein the modified phenolic hydroxyl group-containing resin for the secondary battery negative electrode A xylene-modified phenol resin obtained by reacting a phenol with a xylene or xylene-modifying compound.

(30) A carbon material for a secondary battery negative electrode produced by using a modified phenolic hydroxyl group-containing resin for a secondary battery negative electrode according to any one of the above (23) to (29).

(31) The carbon material for a secondary battery negative electrode according to the above (30), which has a surface area per unit volume determined from a particle size distribution based on the number of particles, and is 10000 cm ^-1 or more and 16,000 cm ^-1 or less. Range of carbon particles.

(32) The carbon material for a secondary battery negative electrode according to the above (31), wherein the carbon particles include an average of (002) planes obtained by an X-ray diffraction method using CuK α rays as a radiation source. The surface spacing d002 is hard carbon of 0.340 nm or more.

(33) The carbon material for a secondary battery negative electrode according to the above (32), wherein the carbon particles contain 90% by mass or more of the hard carbon.

The carbon material for a secondary battery negative electrode according to the above aspect (32), wherein the carbon particles contain the hard carbon and graphite.

(35) A secondary battery negative electrode active material, which comprises the carbon material for a secondary battery negative electrode according to any one of the above (30) to (34).

(36) A secondary battery negative electrode comprising: a negative electrode active material layer containing the secondary battery negative electrode active material of the above (35); and a negative electrode current collector in which the negative electrode active material layer is laminated.

(37) A secondary battery comprising the secondary battery negative electrode according to the above (36), an electrolyte, and a positive electrode for a secondary battery.

(38) A carbon material for a secondary battery negative electrode which contains phosphorus as a main component and contains phosphorus in a range of 0.3% by mass or more and 1.5% by mass or less, and the amount of adsorption of carbon dioxide is less than 10 ml/g per unit weight.

(39) The carbon material for a secondary battery negative electrode according to the above (38), wherein the carbon dioxide adsorption amount is 5 ml/g or less per unit weight.

(40) The carbon material for a secondary battery negative electrode according to the above (38), wherein the carbon dioxide adsorption amount is 0.05 ml/g or more per unit weight.

The carbon material for a secondary battery negative electrode according to any one of the above-mentioned (38), wherein the phosphorus or the phosphorus-containing compound detected by X-ray photoelectron spectroscopy (XPS) is used as a target compound. And the total composition ratio of the triphenylphosphine oxide, the triphenylphosphine, and the reduced phosphorus contained in the target compound is 50% or more with respect to the composition of the target compound, and the reduced phosphorus is The composition ratio is more than 0% and is 13% or less.

The carbon material for a secondary battery negative electrode according to any one of the above aspects, wherein the composition ratio O/C of oxygen to carbon detected by X-ray photoelectron spectroscopy (XPS) is larger than The composition ratio of oxygen to carbon detected by compositional analysis is O/C.

The carbon material for a secondary battery negative electrode according to any one of the above aspects, wherein the composition ratio P (XPS) of the phosphorus detected by X-ray photoelectron spectroscopy (XPS) is larger than The composition ratio of the phosphorus detected by the composition analysis is P(COMP).

(44) The carbon material for a secondary battery negative electrode according to the above (43), wherein the P(COMP) exceeds zero.

The carbon material for a secondary battery negative electrode according to any one of the above-mentioned items, wherein the surface area per unit volume obtained by the particle size distribution based on the number is 10000 cm ^- Carbon particles in the range of ¹ or more and 16,000 cm ^-1 or less.

(46) The carbon material for a secondary battery negative electrode according to the above (45), wherein the carbon particles have a mean square radius determined from the particle diameter distribution of 1 μm ² or more and 4 μm ² or less.

(47) The carbon material for a secondary battery negative electrode according to the above aspect, wherein the carbon particles have a true specific gravity of 1.5 g/cm ³ or more and 1.7 g/cm ³ or less.

The carbon material for a secondary battery negative electrode according to any one of the above aspects, wherein the carbon particles include: an X-ray diffraction method using a CuK α ray as a radiation source. The hard surface of the (002) plane having an average surface spacing d002 of 0.340 nm or more.

(49) The carbon material for a secondary battery negative electrode according to the above (48), wherein the carbon particles contain 90% by mass or more of the hard carbon.

(50) The carbon material for a secondary battery negative electrode according to the above aspect, wherein the carbon particles contain the hard carbon and graphite.

(51) The carbon material for a secondary battery negative electrode according to any one of the above-mentioned (38) to (50), which is used for a secondary battery negative electrode, and which exhibits high temperature storage in the following high-temperature storage property evaluation. The high-temperature storage characteristic evaluation is performed by using a secondary battery negative electrode including a secondary battery negative electrode carbon material, a positive electrode, an electrolyte containing a dissolved electrolyte, and a separator. The battery is subjected to an aging treatment for performing a specific charge and discharge cycle for 5 cycles, and the discharge capacity at the time of discharge in the fifth cycle of the charge and discharge cycle is measured, and the discharge capacity I is used, and the above-described aging treatment is used. A lithium ion secondary battery is charged with a current density of 25 mA/g for constant current charging, and is kept at a constant voltage of 4.2 V from a time point when the potential reaches 4.2 V, and is charged until the current density reaches 2.5 mA/g. In the lithium ion secondary battery in which the state of charge is adjusted to 100%, the lithium ion secondary battery having 100% of the above state of charge is stored in a dryer adjusted to a temperature of 60 ° C for one week, and stored in the above-mentioned storage. After that, the lithium ion secondary battery was charged and discharged at a current value of 0.2 C, and a total of three cycles of charge and discharge were measured as one cycle. The discharge capacity at the time of discharge in the third cycle was set to the discharge capacity II, and the high-temperature storage characteristics were calculated according to the following formula (4).

High-temperature storage characteristics (%) = [discharge capacity II (mAh / g) / discharge capacity I (mAh / g)] × 100 (4)

(52) The carbon material for a secondary battery negative electrode according to any one of the above (38) to (51), which is used for a secondary battery negative electrode, and exhibits a high temperature life in the following high-temperature life characteristic evaluation. The high-temperature life characteristic evaluation is a lithium ion secondary battery including a secondary battery negative electrode including a carbon material for a secondary battery negative electrode, a positive electrode, an electrolyte containing a dissolved electrolyte, and a separator. The aging treatment is performed for 5 cycles of a specific charge and discharge cycle, and the lithium ion secondary battery after the aging treatment described above is charged to 4.2 V at a constant current of 1 C in a temperature environment of 55 ° C, and thereafter, at 4.2 ° The constant voltage of V is charged until the current value is attenuated to 0.02 C, and then maintained at a temperature of 55 ° C for 30 minutes, and then discharged to 2.5 V at a constant current of 1 C, and the discharge capacity is measured to be the discharge capacity III, and thereafter And maintaining the temperature in a temperature of 55 ° C for 30 minutes, performing the above-described charge and discharge cycle as one cycle, and further performing the charge and discharge cycle for 99 cycles, and performing a charge and discharge cycle of a total of 100 cycles, and The discharge capacity at the time of discharge at the 100th cycle was measured and the discharge capacity IV was set, and the high-temperature life characteristics were calculated according to the following formula (5).

High-temperature life characteristics (%) = [discharge capacity IV (mAh / g) / discharge capacity III (mAh / g)] × 100 (5)

(53) A secondary battery negative electrode active material, comprising the carbon material for a secondary battery negative electrode according to any one of the above (38) to (52).

(54) A secondary battery negative electrode comprising: a secondary battery negative electrode active material layer containing the secondary battery negative electrode active material according to (53); and a secondary battery negative electrode laminated thereon A current collector for the negative electrode of the active material layer is used.

(55) A secondary battery comprising the secondary battery negative electrode of the above (54), an electrolyte, and a secondary battery positive electrode.

10‧‧‧negative

12‧‧‧Negative active material layer

14‧‧‧Negative current collector

20‧‧‧ positive

22‧‧‧ positive active material layer

24‧‧‧ positive current collector

30‧‧‧Parts

40‧‧‧ electrolyte

100‧‧‧Lithium ion secondary battery

Claims (55)

A carbon material for a secondary battery negative electrode containing phosphorus as a main component and containing phosphorus in a range of 0.3% by mass or more and 1.5% by mass or less, and the amount of adsorption of carbon dioxide is less than 10 ml/g per unit weight. The carbon material for a secondary battery negative electrode according to the first aspect of the invention, wherein the carbon dioxide adsorption amount is 5 ml/g or less per unit weight. The carbon material for a secondary battery negative electrode according to claim 1 or 2, wherein the carbon dioxide adsorption amount is 0.05 ml/g or more per unit weight. The carbon material for a secondary battery negative electrode according to any one of claims 1 to 3, wherein the phosphorus or the phosphorus-containing compound detected by X-ray photoelectron spectroscopy (XPS) is used as a target compound, and is relative to the above The composition of the target compound is 100%, and the total composition ratio of the triphenylphosphine oxide, the triphenylphosphine, and the reduced phosphorus contained in the target compound is 50% or more, and the composition ratio of the reduced phosphorus is 13 %the following. The carbon material for a secondary battery negative electrode according to any one of claims 1 to 4, wherein a composition ratio O/C of oxygen to carbon detected by X-ray photoelectron spectroscopy (XPS) is greater than that detected by composition analysis. The composition ratio of oxygen to carbon is O/C. The carbon material for a secondary battery negative electrode according to any one of claims 1 to 5, wherein a composition ratio P _(XPS) of the phosphorus detected by X-ray photoelectron spectroscopy _{(XPS) is} greater than that detected by composition analysis. The composition ratio of phosphorus is P _(COMP) . The carbon material for a secondary battery negative electrode according to the sixth aspect of the patent application, wherein the P _(COMP) exceeds zero. The carbon material for a secondary battery negative electrode according to any one of claims 1 to 7, which has a surface area per unit volume determined by a particle size distribution on a number basis of 10000 cm ^-1 or more and 16,000 cm. Carbon particles in the range of ^-1 or less. The carbon material for a secondary battery negative electrode according to the eighth aspect of the invention, wherein the carbon particles have a mean square radius determined from the particle diameter distribution of 1 μm ² or more and 4 μm ² or less. The carbon material for a secondary battery negative electrode according to claim 8 or 9, wherein the carbon particles have a true specific gravity of 1.5 g/cm ³ or more and 1.7 g/cm ³ or less. The carbon material for a secondary battery negative electrode according to any one of claims 8 to 10, wherein the carbon particles are obtained by an X-ray diffraction method using a CuK α ray as a radiation source (002) The average surface spacing d ₀₀₂ of the face is hard carbon of 0.340 nm or more. The carbon material for a secondary battery negative electrode according to the eleventh aspect of the invention, wherein the carbon particles contain 90% by mass or more of the hard carbon. The carbon material for a secondary battery negative electrode according to claim 11 or 12, wherein the carbon particles contain the hard carbon and graphite. The carbon material for a secondary battery negative electrode according to any one of claims 1 to 13, which is used for a secondary battery negative electrode, and exhibits a high-temperature storage characteristic of 85% in the following high-temperature storage property evaluation. In the above, the high-temperature storage property evaluation system uses a secondary battery negative electrode including a carbon material for the secondary battery negative electrode, a positive electrode, an electrolyte containing a dissolved electrolyte, and The lithium ion secondary battery of the separator is subjected to an aging treatment for performing a specific charge and discharge cycle for 5 cycles, and the discharge capacity at the time of discharge in the fifth cycle of the charge and discharge cycle is measured, and the discharge capacity I is determined. Using the above-described lithium ion secondary battery after the aging treatment, the current density was set to 25 mA/g for constant current charging, and from the time point when the potential reached 4.2 V, 4.2 V was further maintained to perform constant voltage charging, and charging was performed to current density. A lithium ion secondary battery prepared to have a state of charge of 100% up to 2.5 mA/g, and the lithium ion secondary battery having the above state of charge of 100% in a dryer adjusted to a temperature of 60 ° C After storing for one week, the lithium ion secondary battery was used for charging and discharging at a current value of 0.2 C, and a total of three cycles of charge and discharge were performed as one cycle, and the third cycle was measured. The discharge capacity at the time of discharge was set to discharge capacity II, and the high-temperature storage characteristics were calculated according to the following formula (4). The high-temperature storage characteristics (%) = [discharge capacity II (mAh/g) / discharge capacity I (mAh/g) ]×100 (4) The carbon material for a secondary battery negative electrode according to any one of claims 1 to 14, which is used for a secondary battery negative electrode, and exhibits a high-temperature life characteristic of 85% in the following evaluation of high-temperature life characteristics. In the above-described high-temperature life characteristic evaluation, a secondary battery negative electrode including a secondary battery negative electrode carbon material, a positive electrode, an electrolyte containing a dissolved electrolyte, and The lithium ion secondary battery of the separator is subjected to an aging treatment for performing a specific charge and discharge cycle for 5 cycles, and the lithium ion secondary battery after the above aging treatment is charged at a constant current of 1 C at a temperature of 55 ° C. To 4.2V, thereafter, after charging at a constant voltage of 4.2V until the current value is attenuated to 0.02C, it is kept at a temperature of 55 ° C for 30 minutes, and then discharged to a constant current of 1 C to 2.5 V, and the discharge capacity is measured. In the case of the discharge capacity III, the battery was held in a temperature of 55 ° C for 30 minutes, and the charge and discharge cycle was carried out as one cycle. Then, the charge and discharge cycle was further carried out for 99 cycles, and the total was performed. 100 cycles of charge and discharge cycles, and measuring the discharge capacity at the discharge of the 100th cycle, and setting the discharge capacity IV, and calculating the high temperature life characteristic according to the following formula (5), and the high temperature life characteristic (%) = [discharge capacity IV (mAh/g) / discharge capacity III (mAh/g)] × 100 (5). An active material for a secondary battery negative electrode, which comprises the carbon material for a secondary battery negative electrode according to any one of claims 1 to 15. A secondary battery negative electrode comprising: a secondary battery negative electrode active material layer containing a secondary battery negative electrode active material of claim 16; and a negative electrode set in which the secondary battery negative electrode active material layer is laminated Electric body. A secondary battery comprising a secondary battery negative electrode, an electrolyte, and a secondary battery positive electrode of claim 17 of the patent application. A resin composition for a secondary battery negative electrode, comprising: A phenolic hydroxyl group-containing resin having a hydroxyl group equivalent of 300 g/eq or less, and a phosphate or phosphoric acid derivative having a boiling temperature or a thermal decomposition temperature exceeding a self-condensation temperature of the phenolic hydroxyl group-containing resin. The resin composition for a secondary battery negative electrode according to claim 19, wherein the phosphate ester is contained in an amount of 3 parts by mass or more and 15 parts by mass or less based on 100 parts by mass of the phenolic hydroxyl group-containing resin. Phosphoric acid derivatives. The resin composition for a secondary battery negative electrode according to claim 19, wherein the melting point of the phosphate or the phosphoric acid derivative does not reach the self-condensation temperature of the phenolic hydroxyl group-containing resin. The resin composition for a secondary battery negative electrode according to claim 21, wherein the melting point of the phosphate or the phosphoric acid derivative and the melting point of the phenolic hydroxyl group-containing resin are both higher than normal temperature and 250 ° C or lower. The resin composition for a secondary battery negative electrode according to claim 22, wherein a melting start temperature of the phosphate or the phosphoric acid derivative does not reach a melting end temperature of the phenolic hydroxyl group-containing resin. The resin composition for a secondary battery negative electrode according to any one of claims 19 to 23, further comprising a curing agent, and the phenolic hydroxyl group-containing resin is a novolac type phenol resin. The resin composition for a secondary battery negative electrode according to any one of claims 19 to 24, wherein the phosphate ester is a phosphate triester. The resin composition for a secondary battery negative electrode according to claim 25, wherein the phosphoric acid triester is triphenyl phosphate or the above-described triphenyl phosphate derivative. The resin composition for a secondary battery negative electrode according to claim 26, wherein the triphenyl phosphate derivative is a compound represented by the following chemical formula (1), [(CH ₃ ) ₂ C ₆ H ₃ O] ₂ P(O)OC ₆ H ₄ OP(O)[OC ₆ H ₃ (CH ₃ ) ₂ ] ₂ (1). A method for producing a carbon material for a secondary battery negative electrode according to any one of claims 19 to 27, which has a method for producing a carbon material for a secondary battery negative electrode for a secondary battery negative electrode according to any one of claims 19 to 27, which has In the first baking step, the resin composition for the secondary battery negative electrode is fired to form a carbon material precursor at a firing temperature of not higher than 1000 ° C at the time of firing; and a second firing step is performed. The firing condition at a temperature at which the maximum temperature is 1000 ° C or higher at the time of firing is performed by firing the carbon material precursor generated in the first firing step to produce a carbon material. The method for producing a carbon material for a secondary battery negative electrode according to the invention of claim 28, wherein the first baking step includes: a melting step of causing the phenolic hydroxyl group contained in the resin composition for a secondary battery negative electrode The resin and the phosphate ester or the phosphoric acid derivative are melted; and the carbon precursor precursor is formed to form a crystallite containing carbon of a degreased and/or graphene-like structure. A carbon material for a secondary battery negative electrode, which is produced by using a resin composition for a secondary battery negative electrode according to any one of claims 19 to 27, which contains: The surface area per unit volume obtained by the particle size distribution under the reference is a carbon particle in a range of 10000 cm ^-1 or more and 16,000 cm ^-1 or less. The carbon material for a secondary battery negative electrode according to claim 30, wherein the carbon particles have a mean square radius determined from the particle diameter distribution of 1 μm ² or more and 4 μm ² or less. The carbon material for a secondary battery negative electrode according to claim 30, wherein the carbon particles have a true specific gravity of 1.5 g/cm ³ or more and 1.7 g/cm ³ or less. The carbon material for a secondary battery negative electrode according to any one of claims 30 to 32, wherein the carbon particles are obtained by an X-ray diffraction method using a CuK α ray as a radiation source (002) The average surface spacing d ₀₀₂ of the face is hard carbon of 0.340 nm or more. The carbon material for a secondary battery negative electrode according to claim 33, wherein the carbon particles contain 90% by mass or more of the hard carbon. The carbon material for a secondary battery negative electrode according to claim 33, wherein the carbon particles contain the hard carbon and graphite. The carbon material for a secondary battery negative electrode according to any one of claims 30 to 35, which is used for a negative electrode of a secondary battery, and exhibits a high-temperature storage characteristic of 85% in the evaluation of high-temperature storage characteristics described below. In the above, the high-temperature storage characteristic evaluation is performed by using a lithium ion secondary battery including a secondary battery negative electrode including a secondary battery negative electrode carbon material, a positive electrode, an electrolytic solution obtained by dissolving an electrolyte, and a separator. The specific charge and discharge cycle is subjected to five cycles of aging treatment, and the discharge capacity at the time of discharge in the fifth cycle of the charge and discharge cycle is measured, and the discharge capacity I is used, and the lithium ion after the aging treatment is used twice. Battery, set the current density to 25 mA/g performs constant current charging. From the time point when the potential reaches 4.2V, it is further kept at 4.2V for constant voltage charging, and is charged until the current density reaches 2.5 mA/g, and the state of charge is adjusted to In a 100% lithium ion secondary battery, the lithium ion secondary battery having 100% of the above-described state of charge is stored in a dryer whose temperature is adjusted to 60° C. for one week, and after the storage, the lithium ion secondary battery is used. The current value of 0.2C is charged and discharged, and a total of three cycles of charge and discharge are performed as one cycle, and the discharge capacity at the time of discharge of the third cycle is measured to be the discharge capacity II, according to the following formula ( 4) The high-temperature storage characteristics were calculated, and the high-temperature storage characteristics (%) = [discharge capacity II (mAh/g) / discharge capacity I (mAh/g)] × 100 (4). The carbon material for a secondary battery negative electrode according to any one of claims 30 to 36, which is used for a secondary battery negative electrode, and exhibits a high-temperature life characteristic of 85% in the following high-temperature life characteristic evaluation. In the above-mentioned high-temperature life characteristic evaluation, a lithium ion secondary battery including a secondary battery negative electrode including a secondary battery negative electrode carbon material, a positive electrode, an electrolytic solution obtained by dissolving an electrolyte, and a separator is used. The specific charge and discharge cycle is subjected to an aging treatment of 5 cycles, and the lithium ion secondary battery after the above aging treatment is charged to 4.2 V at a constant current of 1 C in a temperature environment of 55 ° C, and thereafter, at 4.2 V. Constant voltage charging to electricity After the flow value was attenuated to 0.02 C, it was kept at a temperature of 55 ° C for 30 minutes, and then discharged to 2.5 V at a constant current of 1 C, and the discharge capacity was measured to be a discharge capacity III, and thereafter, at a temperature of 55 ° C. The battery was kept in the environment for 30 minutes, and the above-described charge and discharge cycle was carried out as one cycle. Then, the charge and discharge cycle was further carried out for 99 cycles, and a total of 100 cycles of charge and discharge cycles were performed, and the 100th cycle was measured. The discharge capacity at the time of discharge was set to the discharge capacity IV, and the high-temperature life characteristic was calculated according to the following formula (5). The high-temperature life characteristic (%) = [discharge capacity IV (mAh/g) / discharge capacity III (mAh/g) ] × 100 (5). An active material for a secondary battery negative electrode, which comprises the carbon material for a secondary battery negative electrode according to any one of claims 30 to 37. A secondary battery negative electrode comprising: a secondary battery negative electrode active material layer containing a secondary battery negative electrode active material of claim 38; and a negative electrode set in which the secondary battery negative electrode active material layer is laminated Electric body. A secondary battery comprising a secondary battery negative electrode, an electrolyte, and a secondary battery positive electrode of claim 39. A resin containing a modified phenolic hydroxyl group for a negative electrode of a secondary battery, which has a hydroxyl equivalent of 115 g/eq or more. A resin containing a modified phenolic hydroxyl group for use in a negative electrode for a secondary battery of claim 41, which contains a structure represented by the following formula (4), (In the formula (4), P represents a structure containing a phenolic hydroxyl group, and A and B represent any atom or group of atoms constituting a main chain of a resin containing a modified phenolic hydroxyl group, and X represents an arbitrary aryl group, n Is an integer greater than 1). A resin containing a modified phenolic hydroxyl group for use in a negative electrode for a secondary battery of claim 42 wherein the above formula (4) is represented by the following formula (5). (In the formula (5), X ₁ to X ₄ each independently represent a substituent or a hydrogen atom of the benzene nucleus). A resin containing a modified phenolic hydroxyl group for use in a negative electrode for a secondary battery of the _fourth aspect of the invention, wherein any one of X ₁ to X ₄ in the above formula (5) is a methyl group. The resin containing a modified phenolic hydroxyl group for use in a negative electrode for a secondary battery of claim 44, wherein the above X ₁ and the above X ₂ in the above formula (5) are both methyl groups, and the above two The base is in the meta position by one carbon atom. A resin containing a modified phenolic hydroxyl group for use in a negative electrode for a secondary battery according to any one of claims 41 to 45, wherein the resin containing a modified phenolic hydroxyl group for the negative electrode of the secondary battery is a phenol aralkyl Base resin. The resin containing a modified phenolic hydroxyl group for use in a negative electrode for a secondary battery according to any one of claims 41 to 46, wherein the resin containing a modified phenolic hydroxyl group for the negative electrode of the secondary battery is A xylene-modified phenol resin obtained by reacting a phenol with a xylene or xylene modifying compound. A carbon material for a secondary battery negative electrode which is produced by using a resin containing a modified phenolic hydroxyl group for a secondary battery negative electrode according to any one of claims 41 to 47. The carbon material for a secondary battery negative electrode according to the 48th aspect of the patent application, comprising: a surface area per unit volume obtained by a particle size distribution based on the number of particles is 10000 cm ^-1 or more and 16,000 cm ^-1 or less Carbon particles. The carbon material for a secondary battery negative electrode according to claim 49, wherein the carbon particles comprise: an average surface interval of the (002) plane obtained by an X-ray diffraction method using a CuK α ray as a radiation source. d ₀₀₂ is a hard carbon of 0.340 nm or more. The carbon material for a secondary battery negative electrode according to claim 50, wherein the carbon particles contain 90% by mass or more of the hard carbon. The carbon material for a secondary battery negative electrode according to claim 50 or 51, wherein the carbon particles contain the hard carbon and graphite. A secondary battery negative electrode active material comprising the carbon material for a secondary battery negative electrode according to any one of claims 48 to 52. A secondary battery negative electrode comprising: a negative electrode active material layer containing a secondary battery negative electrode active material of claim 53; and a negative electrode current collector in which the negative electrode active material layer is laminated. A secondary battery comprising a secondary battery negative electrode, an electrolyte, and a positive electrode for a secondary battery of claim 54.