JP2002190301A - Electrode carbon material of nonaqueous-solvent secondary battery, and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode carbon material of a nonaqueous-solvent secondary battery having a high charge capacity, and to provide a method for manufacturing the same. SOLUTION: An electrode carbon material of a nonaqueous-solvent secondary battery has no diffraction peaks by X ray diffraction in (002) plane and (004) plane, and has a six-membered ring carbon structure in the carbon material, and is obtained by carbonizing an organic polymer material, in which at least a benzen ring structure is contained in the molecule, at a sintering temperature of 800 to 2,000 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrode carbon material for a non-aqueous solvent secondary battery and a method for producing the same. More specifically, the present invention relates to an improved carbon material for a negative electrode of a nonaqueous solvent secondary battery having a high charge capacity and a method for producing the same.

[0002]

2. Description of the Related Art Carbon materials used as negative electrodes of non-aqueous solvent secondary batteries include (a) large charge / discharge capacity, (b) low discharge potential and good flatness, and (c) good cycle characteristics. (D) a high charge / discharge rate, (e) a small change in volume accompanying a charge / discharge reaction, (f) excellent electrode formability,
(G) Conditions such as low cost are desired.

Many such carbon materials for negative electrodes are known. For example, (A) the plane spacing of the (002) plane by the X-ray wide-angle diffraction method is (d ₀₀₂ ) where d ₀₀₂ ≦ 0
336nm and and (B) the correlation length obtained by small-angle X-ray scattering method (I _C) is I _C> 12 nm satisfy the condition of (JP-A-9-265936), an average particle size of 4~40μm and wavelength 5145Å Raman spectrum analysis using argon ion laser light of 1570-1620
The intensity of the peak present in the range of cm ^-1 was determined as IA, 135
The intensity of the peak existing in the range of 0 to 1370 cm ^-1 is represented by I
When B, the R value (= IB / IA), which is the ratio, is 0.001 to 0.07, and 1570 to 1620
A graphite material (Japanese Patent Laid-Open No. 11-25979) for a lithium ion secondary battery having a Δv value of 14 to 22 which is a half width of a peak existing at cm ⁻¹ is known. However, the charge capacity of these negative electrodes is LiC
_A capacity near the theoretical capacity of 372 Ah / kg (based on carbon) determined from the composition of ₆ was obtained, which is not yet satisfactory.

[0004] As for the technology using hard carbon, for example, a method has been proposed in which natural materials are carbonized and used (Japanese Patent Laid-Open No. 10-284089). However, although a high charging capacity can be obtained by this method, the use of Poaceae bamboo as a raw material may cause natural destruction when used for industrial purposes, and is insufficient in terms of resources.

Further, a carbonaceous material for a secondary battery electrode using a carbonized aromatic compound having a phenolic hydroxyl group has been proposed (JP-A-10-223226).
However, the charge capacity is about 660 Ah / kg, and a satisfactory charge capacity cannot be obtained.

[0006]

Accordingly, an object of the present invention is to provide a novel electrode carbon material for a non-aqueous solvent secondary battery and a method for producing the same.

Another object of the present invention is to provide an electrode carbon material for a non-aqueous solvent secondary battery having a high charge capacity of 700 Ah / kg or more and a method for producing the same.

[0008]

The above objects are achieved by the following (1) to (14).

(1) An aqueous solvent secondary battery characterized in that it has no diffraction peak on the (002) and (004) planes by X-ray diffraction and has a six-membered ring carbon structure in the carbon material. Electrode carbon material.

(2) In Raman spectroscopy using an argon laser having a wavelength of 514.5 nm, 1510 to 16
The area of the peak existing in the range of 80 cm ^-1 is G, 120
The area of the peak existing in the range of 0 to 1450 cm ^-1 is represented by D
The electrode carbon material according to (1), wherein the R value (R = D / G area ratio) is 0.9 or less. (3) G-band half width by Raman spectroscopy is 50 to 1.
The electrode carbon material according to the above (1) or (2), which is 50 cm ^-1 . (4) The electrode carbon material according to any one of the above (1) to (3), wherein the graphite content in the carbon material is 1% by weight or less. (5) The electrode carbon material according to any one of (1) to (4), wherein the carbon content in the carbon material is 99% by weight or more. (6) The above (1) to (5), wherein the organic polymer material having at least a benzene ring structure in the molecule is carbonized.
An electrode carbon material according to any one of the above. (7) The non-polymer according to any one of (1) to (6), wherein the organic polymer material having at least a benzene ring structure in the molecule is carbonized at a firing temperature of 800 to 2000 ° C. A method for producing an electrode carbon material for an aqueous solvent secondary battery. (8) The method according to (7), wherein the benzene ring content in the organic polymer material is 80% by weight. (9) The organic polymer material according to (7) or (8), wherein the organic polymer material is calcined in a vacuum or an inert gas at a temperature of 400 to 600 ° C. for 5 to 10 hours before carbonization. Method. (10) The method according to any one of (7) to (9), wherein the carbonization is performed under a vacuum of 10 ² Pa or less. (11) A carbon negative electrode using the electrode carbon material described in any one of (1) to (6) above. (12) The carbon negative electrode as described in 11 above, wherein a general formula Li
A composite oxide having a layered crystal structure represented by MO ₂ , wherein M is composed of two types of metal elements, contains at least one type of 3d transition metal, and has a difference in the number of electrons between the two types of metal elements. A secondary battery characterized by combining an odd number of positive electrodes made of a composite oxide. (13) The carbon negative electrode as described in 11 above, wherein a general formula Li
A composite oxide having a layered crystal structure represented by _x-1 MO ₂ , wherein M is at least manganese and the amount of Li deficiency X is a rational number of 0 <X <1. A rechargeable battery characterized by being combined. (14) The carbon negative electrode as described in 11 above, wherein a general formula Li
A composite oxide having a layered crystal structure represented by α _-1 AαMnO ₂ , wherein A comprises at least an alkali metal and Ag, and the substitution amount α of A is 0.03 <α <
A secondary battery comprising a combination of a positive electrode made of a composite oxide of 0.2.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The electrode carbon material of the non-aqueous solvent secondary battery according to the present invention has a (002) plane and (0
It is essential that the material does not substantially have a diffraction peak on the (04) plane. That is, it is essential that it is not substantially graphitized. Further, it is necessary that the electrode carbon material has a six-membered ring carbon structure.

When Raman spectroscopy is performed using an argon laser having a wavelength of 514.5 nm, 1510
G is the area of the peak existing in the range of １６1680 cm ⁻¹
When the area of the peak existing in the range of 1200 to 1450 cm ^-1 is R, the R value (R = D / G area ratio) is 0.9 or less, preferably 0.4 to 0.9. Use something. That is, if the R value is 0.4 or more, the graphite content becomes 1% by weight or less without excessive progress of the graphitization, and the charge capacity becomes high. Also,
When the R value does not exceed 0.9, the six-membered ring carbon structure is more present in the carbon material, and the charge capacity is similarly increased.

Further, G by Raman spectroscopy at this time
The band half width is desirably 50 to 150 cm ^-1 . In other words, if the G band half-width is 50 cm ^-1 or more, the carbonization of the carbon material does not proceed excessively, and the graphite content does not exceed 1% by weight, so that a material having a high charge capacity can be obtained. On the other hand, the G band half width is 150c.
When m ⁻¹ , the effect of impurities is small and a product having a high charge capacity can be obtained.

Further, the graphite content in the carbon material is 1% by weight or less. That is, when the graphite content is 1% by weight or less, a material having a high charge capacity can be obtained. Further, the carbon content in the carbon material is 99% or more. That is, when the carbon content is 99% by weight or more,
This is because a graphite having a high charge capacity can be obtained without increasing the graphite content.

The electrode carbon material of the non-aqueous solvent secondary battery according to the present invention is produced by carbonizing an organic polymer material having at least a benzene ring structure in a molecule at a firing temperature of 800 to 2000 ° C. That is, an amorphous 6-membered ring carbon structure is formed in carbon. This amorphous six-membered ring carbon structure aims at a middle point between the characteristics of each of the conventional hard carbon and graphite, and has found that a negative electrode characteristic of high charge capacity can be exhibited.

Examples of the organic polymer material having at least a benzene ring in the molecule used as a raw material include polyphenylene resins composed of phenyl compounds such as biphenyl and terphenyl, and aromatic hydrocarbons composed of polycyclic aromatic compounds such as naphthalene and anthracene. There are hydrogen resin, benzene and naphthalene copolymer, phenyl group-containing thermoplastic resin such as polyphenylene sulfide and polyphenylene oxide, phenol-formaldehyde resin, polyphenylene vinylene, polynaphthalene vinylene and the like. Is used.

These raw materials are steamed in a vacuum or an inert gas at a temperature of 400 to 600 ° C.
Temporary firing is performed for a time. The inert gas can be selected from argon gas, neon gas, nitrogen gas and the like, but inexpensive nitrogen gas is desirable. When pre-baking in vacuum,
The degree of vacuum is desirably 10 ² Pa or less.

It is desirable that the calcined product obtained in this manner is coarsely pulverized after cooling. After supplying this calcined product to a crucible made of graphite, it is set in a vacuum electric furnace and subjected to main baking. The firing temperature can be selected from 800 to 2000 ° C. That is, when the temperature is lower than 800 ° C., the firing time for carbonization becomes too long.
The graphite content in the resulting carbon material increases.
In this case, the degree of vacuum is desirably 10 ² Pa or less,
It is preferably at most 0 ¹ Pa. The firing time is not particularly limited, but is preferably 3 hours or more. The carbon content in the obtained carbon material in the carbon material is desirably 99% by weight or more. That is, if the content does not exceed 99% by weight, the irreversible capacity at the time of charging and discharging increases, and the battery becomes unsuitable as a negative electrode material. For this reason, it is necessary that the organic polymer material containing a benzene ring, which is a starting material, has a small amount of impurities, and a material that is easily decomposed into carbon during firing is desirable.

When the carbon content of the calcined product is low, a hydrogen reduction treatment is performed to remove impurities such as oxygen in the carbon material. The reduction treatment temperature can be selected from 800 to 2000 ° C. In other words, when the temperature is lower than 800 ° C., the processing time for reduction becomes longer, while when it exceeds 2000 ° C., the graphite content in the material increases. The processing time is not particularly limited, but is preferably 5 hours or more.

The obtained carbon material for an electrode has a binder which is stable to a non-aqueous solvent,
% By mass. Examples of such a non-aqueous solvent-stable binder include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, and polypropylene. If necessary, the viscosity is adjusted with an organic solvent of N-methyl-2-pyrrolidone. This is stirred into a paste using a disperser such as a homogenizer, and defoaming treatment such as vacuum defoaming is performed to prepare a coating liquid for electrode production. This coating solution is applied on a copper foil using a doctor blade or the like, and dried at a temperature of 120 to 150 ° C., whereby a carbon electrode of a nonaqueous solvent secondary battery is obtained.

Using this carbon electrode, the positive electrodes shown in Tables 1 and 2 were arranged at the counter electrode, and LiPF ₆ , L
iClO ₄ , LiBF ₄ , LiCH ₃ SO ₄ , LiAs
Using F ₆ , LiCl, LiBr, lithium nickelate or the like, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, sulfolane, 1,3 -One or more organic solvents such as dioxolane are selected, and a mixed solvent is prepared as necessary to obtain a non-aqueous solvent secondary battery.

[0022]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Negative electrode material 1 A commercially available phenol-formaldehyde resin containing 5% by weight of hexamethylenetetramine as a curing agent was used in 150 parts.
After curing for 3 hours at 5 ° C.,
Preliminary firing was performed at a temperature of 00 ° C. for 5 hours. After cooling, coarsely crushed, high temperature hot press vacuum furnace (manufactured by Shimadzu Corporation)
The main firing was performed at 1200 ° C. for 5 hours at a degree of vacuum of 10 ¹ Pa. After cooling, the mixture was pulverized with an alumina ball mill for 1 hour to prepare a carbon powder having an average particle size of about 30 μm.

Negative electrode material 2 A commercially available phenol-formaldehyde resin containing 5% by weight of hexamethylenetetramine as a curing agent was used in 150 parts.
After curing for 3 hours at 5 ° C.,
Preliminary firing was performed at a temperature of 00 ° C. for 5 hours. After cooling, coarsely crushed, high temperature hot press vacuum furnace (manufactured by Shimadzu Corporation)
The main firing was performed at 800 ° C. for 5 hours at a degree of vacuum of 10 ¹ Pa. After cooling, the mixture was pulverized with an alumina ball mill for 1 hour to prepare a carbon powder having an average particle size of about 30 μm. This powder is set in a quartz tube, and 80
Hydrogen reduction treatment was performed at 0 ° C. for 8 hours to produce a carbon powder.

Negative electrode material 3 A commercially available phenol-formaldehyde resin containing 5% by weight of hexamethylenetetramine as a curing agent was used in 150 parts.
After curing for 3 hours at 5 ° C.,
Preliminary firing was performed at a temperature of 00 ° C. for 5 hours. After cooling, coarsely crushed, high temperature hot press vacuum furnace (manufactured by Shimadzu Corporation)
, And baked at 2000 ° C. for 5 hours at a degree of vacuum of 10 ¹ Pa. After cooling, the mixture was pulverized with an alumina ball mill for 1 hour to prepare a carbon powder having an average particle size of about 30 μm.

Negative Electrode Material 4 A commercially available self-condensation type phenol-formaldehyde resin (35% by weight of methanol) is cured at 150 ° C. for 3 hours, and then calcined at 500 ° C. for 5 hours in a nitrogen gas atmosphere. Was. After cooling, coarsely pulverized, set in a high-temperature hot press vacuum furnace (manufactured by Shimadzu Corporation), and set the degree of vacuum to 1
Main firing was performed at 1200 ° C. for 5 hours at 0 ¹ Pa. After cooling, the mixture was pulverized with an alumina ball mill for 1 hour to prepare a carbon powder having an average particle size of about 30 μm.

Negative Electrode Material 5 A commercially available self-condensed phenol-formaldehyde resin (35% by weight of methanol) is cured at 150 ° C. for 3 hours, and then temporarily calcined at 500 ° C. for 5 hours in a nitrogen gas atmosphere. Was. After cooling, coarsely pulverized, set in a high-temperature hot press vacuum furnace (manufactured by Shimadzu Corporation), and set the degree of vacuum to 1
The main baking was performed at 800 ° C. for 5 hours at 0 ¹ Pa. After cooling,
Pulverized for 1 hour with an alumina ball mill, the average particle size is about 3
A 0 μm carbon powder was produced. This powder was set in a quartz tube, and subjected to a hydrogen reduction treatment at 800 ° C. for 8 hours while flowing hydrogen gas to produce a carbon powder.

Negative electrode material 6 A commercially available self-condensation type phenol-formaldehyde resin (35% by weight of methanol) is cured at 150 ° C. for 3 hours, and then calcined at 500 ° C. for 5 hours in a nitrogen gas atmosphere. Was. After cooling, the mixture was roughly pulverized, set in a high-temperature hot press vacuum furnace, and 2,000 hours at a vacuum degree of 10 ¹ Pa for 5 hours.
The main sintering was performed at ℃. After cooling, the mixture was pulverized with an alumina ball mill for 1 hour to prepare a carbon powder having an average particle size of about 30 μm.

Comparative Example 1 Commercially available graphite was used as it was.

Examples 1 to 50 (Preparation of Battery) Positive electrode active materials prepared using the transition metal compounds shown in Tables 1 and 2 were mixed with acetylene black as a conductive material and PTFE powder as a binder. The mixture was mixed at a weight ratio of 80: 16: 4. This mixture was formed into a disk having a diameter of 12 mm with a pressure of ² t / cm ² , and the obtained formed product was heated at 150 ° C. for 16 hours to obtain a positive electrode body.

Next, KF polymer manufactured by Kureha Chemical Industry Co., Ltd. was added to the carbon powder obtained from the above negative electrode materials 1 to 6 for 10 times.
wt%, the viscosity is adjusted with N-methyl-2-pyrrolidone, and the number of revolutions is 3000 rpm with a homogenizer.
Dispersion was performed for 30 minutes. After vacuum degassing, this was coated on a copper foil with a doctor blade so that the film thickness became 100 μm, and dried at 150 ° C. for 10 minutes to obtain a negative electrode body.

As the electrolytic solution, a solution in which LiPF6 was dissolved at a concentration of 1 mol / liter in a mixed solvent of ethylene carbonate and diethyl carbonate at a volume ratio of 1: 1 was used. And a polypropylene film was used as a separator.

An SUS thin plate was used as a current collector for the positive electrode.
The positive electrode body and the negative electrode body were each taken out of the lead, and were opposed to each other with a separator therebetween to form an element. The element was sandwiched between two PTFE plates while being held by a spring. Furthermore, the side surfaces of the element were also covered with a PTFE plate and sealed to obtain a sealed nonaqueous solvent battery cell. Further, the cell was prepared in an argon atmosphere.

(Evaluation) Using the above sealed non-aqueous solvent battery cell, a voltage of 4.3 V to 2.
The charge / discharge was repeated at a constant current of 0.5 mA / cm ² until 0 V, and the number of cycles until the discharge capacity became less than 80% of the initial discharge capacity was obtained. The results are shown in Tables 1 and 2 below. .

With respect to the electrode carbon material, the results of X-ray diffraction measurement and Raman spectroscopy measurement are shown in Tables 1 and 2.
It is shown along with.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

As described above, the electrode carbon material of the non-aqueous solvent secondary battery according to the present invention is obtained by carbonizing a raw material having a benzene ring in an organic polymer material at a low temperature of 800 to 2000 ° C. Thereby, an amorphous 6-membered ring carbon structure is formed in carbon. This amorphous six-membered ring carbon structure aims at a middle point between the characteristics of the conventional hard carbon and graphite, and can exhibit negative electrode characteristics of high charge capacity.

In addition, by combining with a positive electrode composed of a Li-containing manganese layered composite oxide, a high-performance and compact electric vehicle battery excellent in cycle durability as compared with a conventional lithium secondary battery can be obtained.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H029 AJ03 AK03 AL06 AM03 AM05 AM07 CJ02 DJ17 HJ01 HJ02 HJ04 HJ13 HJ14 HJ15 5H050 AA08 BA17 CA07 CA08 CA09 CB07 DA02 DA03 EA24 FA19 GA02 GA27 HA01 HA02 HA04 HA13 HA14 HA15 HA20

Claims (14)

[Claims] 1. The (002) plane and the (0) plane by X-ray diffraction
An electrode carbon material for a non-aqueous solvent secondary battery, wherein the carbon material does not have a diffraction peak on the 04) plane and has a six-membered ring carbon structure in the carbon material. 2. Raman spectroscopy using an argon laser having a wavelength of 514.5 nm has a value of 1510 to 1680.
The area of the peak existing in the range of cm ^-1 is G,
When the area of a peak existing in the range of 1450 cm ^-1 is represented by D, the R value (R = D / G area ratio), which is the ratio, is 0.1.
The electrode carbon material according to claim 1, which is 9 or less. 3. The electrode carbon material according to claim ¹ , wherein the G band half-width by Raman spectroscopy is 50 to 150 cm ^−1. 4. The graphite content in the carbon material is 1
The electrode carbon material according to any one of claims 1 to 3, which is not more than weight%. 5. The carbon material has a carbon content of 99% by weight.
The electrode carbon material according to any one of claims 1 to 4, which is as described above. 6. An organic polymer material having at least a benzene ring structure in the molecule, which is obtained by carbonizing an organic polymer material.
6. The electrode carbon material according to any one of 5. 7. The non-aqueous solution according to claim 1, wherein the organic polymer material having at least a benzene ring structure in the molecule is carbonized at a firing temperature of 800 to 2000 ° C. A method for producing an electrode carbon material for a solvent secondary battery. 8. The method according to claim 7, wherein the benzene ring content in the organic polymer material is 80% by weight. 9. The organic polymer material is heated at a temperature of 400 to 600 ° C. in a vacuum or an inert gas before carbonization.
The method according to claim 7 or 8, which is calcined for 10 to 10 hours. 10. The method according to claim 7, wherein the carbonization is performed under a vacuum of 10 ² Pa or less. 11. A carbon negative electrode using the electrode carbon material according to claim 1. 12. The carbon negative electrode according to claim 11,
A composite oxide having a layered crystal structure represented by a general formula LiMO ₂ , wherein M is composed of two kinds of metal elements,
A secondary battery comprising a combination of a positive electrode comprising a composite oxide containing at least one 3d transition metal and having an odd number of electrons between the two metal elements. 13. The carbon negative electrode according to claim 11,
A composite oxide having a layered crystal structure represented by the general formula Li _x-1 MO ₂ , wherein M is at least manganese, and the amount X of Li is a rational number of 0 <X <1. A secondary battery comprising a combination of positive electrodes. 14. The carbon negative electrode according to claim 11,
A composite oxide having a layered crystal structure represented by the general formula Liα _-1 AαMnO ₂ , wherein A comprises at least an alkali metal and Ag, and the substitution amount α of A is 0.0
A secondary battery in which a positive electrode made of a composite oxide satisfying 3 <α <0.2 is combined.