KR100856955B1 - Polyvinyl acetal resin varnish, gelling agent, nonaqueous electrolyte and electrochemical device - Google Patents

Abstract

The present invention provides a polyvinyl acetal resin varnish and its use, which are low enough to have no problems in practical use, irritant, toxic, environmental pollution, odor and flammability, and have high safety and low viscosity. As the organic solvent for dissolving the polyvinyl acetal resin, a polyvinyl acetal resin is related to its kind by using a non-aqueous solvent, preferably a carbonate ester, more preferably a mixed solvent of a cyclic carbonate and a chain carbonate ester. It dissolves uniformly without, and a high safety and low viscosity varnish is obtained. Since the varnish has the action of gelling an organic solvent, it can be used as a gelling agent in various applications.

Description

Polyvinyl acetal resin varnish, gelling agent, non-aqueous electrolyte and electrochemical device {POLYVINYL ACETAL RESIN VARNISH, GELLING AGENT, NONAQUEOUS ELECTROLYTE SOLUTION, AND ELECTROCHEMICAL DEVICE}

The present invention relates to a polyvinyl acetal resin varnish. The polyvinyl acetal resin varnish of the present invention is useful as, for example, a coating material for a conductive material, an adhesive for an inorganic material and an organic material, and the like.

The present invention also relates to the use of a polyvinyl acetal resin varnish, and more particularly, to a nonaqueous electrolyte and an electrochemical device obtained by using a gelling agent of an organic solvent containing a polyvinyl acetal resin varnish, a polyvinyl acetal resin varnish. It is about.

Polyvinyl acetal resin is a generic term for resins obtained by aldehyde acetalization of polyvinyl alcohol. Polyvinyl acetal resins are used for a wide range of applications as coating materials or adhesives because they have good electrical insulation, excellent adhesion and chemical resistance, and high mechanical strength such as flexibility and abrasion resistance. For example, it is used as an adhesive for procedures, such as an enamel wire varnish, a magnetic tape binder, glass fiber, and a carbon fiber, etc. Moreover, it is used as a coating material or an adhesive agent in structural buildings, aircraft, etc.

When using polyvinyl acetal resin for the said use, it is preferable to melt | dissolve and varnish in a solvent. However, in esters such as methyl acetate, ethyl acetate and butyl acetate, which are common industrial solvents, and ketones such as methyl ethyl ketone, acetone and cyclohexane, polyvinyl acetal resin cannot be dissolved sufficiently uniformly.

For this reason, in the varnishing of polyvinyl acetal resin, glacial acetic acid, monochloroacetic acid, benzyl alcohol, cresol, xylenol, fufural, dioxane, tetrahydrofuran, pyridine, dichloroloethane, chloroform, N-methylpi Rollidone, dimethyl sulfoxide, the mixed solvent of toluene and ethanol, etc. are used. All of these solvents have only problems such as strong irritation, relatively high toxicity to the human body, high environmental pollution, bad smell, and high flammability.

Therefore, in the polyvinyl acetal resin varnishing, a facility having sufficient capability in exhaust, decontamination, detoxification, static electricity removal, etc. is installed so that the solvent does not come into contact with the human body or be released into the environment. It is necessary to take a lot of safety measures.

In addition, polyvinyl acetal resins are used in electrochemical devices such as batteries, capacitors, and solar cells using an electrolyte called grezelel, in order to achieve high capacity, thinner thickness, improved shape freedom, and the like in charge and discharge capacity. It is used in order to gelatinize and obtain a film-like electrolyte (gel-type polymer electrolyte) (Japanese Unexamined-Japanese-Patent No. 57-143355 etc.). In the prior art, in order to obtain a film-like electrolyte using a polyvinyl acetal resin, it is necessary to contain the resin at least 10% by weight of the total amount of the electrolyte solution, but if molecules of the polyvinyl acetal resin are dispersed in such a high concentration in the electrolyte solution This molecule inhibits the movement of ions. For this reason, the ionic conductivity is lower than that of the electrolyte, resulting in poor electrical load characteristics. Reducing the content of the polyvinyl acetal resin can increase the ionic conductivity, but the gel strength is lowered, which loses the inherent advantages of the gel polymer electrolyte that improves the shape freedom of the electrochemical device.

Moreover, it is also known to use it as a solid polymer electrolyte, without impregnating a polyvinyl acetal resin with a solvent (Unexamined-Japanese-Patent No. 10-50141). However, this electrolyte also has a very low ion conductivity, which greatly reduces the electrical load characteristics.

Disclosure of the Invention

An object of the present invention is to provide a polyvinyl acetal resin varnish with little trouble and high safety in any of irritant, toxic, environmental pollution, odor and flammability. Furthermore, in order to improve workability, such as a painting work, it is providing the low viscosity polyvinyl acetal resin varnish.

An object of the present invention is to provide a high-safety and low-viscosity polyvinyl acetal resin varnish for use as an electrolytic solution in electrochemical devices.

The present inventors 1) The polyvinyl acetal resin varnish preferably contains a polyvinyl acetal resin mixed with a carbonate ester, in particular a polyvinyl acetal resin is contained at a high concentration when a mixed solvent of a cyclic carbonate and a chain carbonate is used. 2) The polyvinyl acetal resin varnish was found to be useful as a gelling agent, such as a nonaqueous electrolyte, an organic solvent, etc. in an electrochemical device, and came to complete this invention.

The present invention is a polyvinyl acetal resin varnish characterized in that the polyvinyl acetal resin is dissolved in a nonaqueous solvent made of carbonate ester.

The polyvinyl acetal resin varnish of the present invention is characterized in that the carbonate ester is a mixture of a cyclic carbonate ester and a chain carbonate ester.

Furthermore, the polyvinyl acetal resin varnish of this invention is characterized by the moisture content of 200 ppm or less.

Furthermore, the polyvinyl acetal resin varnish of the present invention is characterized in that the polyvinyl acetal resin is a polyvinyl formal resin.

Furthermore, the polyvinyl acetal resin varnish of the present invention is characterized in that the polyvinyl acetal resin is an acid modified product.

Furthermore, the polyvinyl acetal resin varnish of the present invention has a polyvinyl acetal resin having a proton content of 0.25 at 4.25 to 4.35 ppm based on the peak (2.49 ppm) of DMSO-d ₆ in ¹ H-NMR measurement. It is characterized by the fact that the molar / kg or less.

Furthermore, the polyvinyl acetal resin varnish of this invention is characterized by the hydroxyl group content of polyvinyl acetal resin being 0.1-2 mol / kg.

Moreover, this invention contains the polyvinyl acetal resin varnish of any one of the above, and it is a gelling agent characterized by gelatinizing an organic solvent.

Moreover, this invention is a nonaqueous electrolyte solution containing an electrolyte and the above-mentioned polyvinyl acetal resin varnish.

In addition, the nonaqueous electrolyte of the present invention contains an electrolyte, a nonaqueous solvent, and a polyvinyl acetal resin, and furthermore, a polyamide acetal resin has a number average molecular weight? In terms of polystyrene, and a nonaqueous number of polyvinyl acetal resins. The concentration c (wt%) in the electrolyte solution is characterized by having the following relationship.

100 ≤ λ ^1/2 × c ≤ 1000

Furthermore, the nonaqueous electrolyte of the present invention is characterized in that the concentration of the polyvinyl acetal resin is 0.3 to 3.5% by weight of the amount of the nonaqueous electrolyte.

Furthermore, the non-aqueous electrolyte of the present invention is characterized by further containing a compound that generates an acid.

Furthermore, the nonaqueous electrolyte of the present invention is characterized in that the acid-producing compound is a Lewis acid having a fluorine atom and / or a Lewis acid salt.

The present invention is also an electrochemical device comprising at least a negative electrode, a separator, a positive electrode and a nonaqueous electrolyte, and an electrochemical device characterized in that the negative electrode and / or the positive electrode and the separator are bonded by a crosslinked product of a polyvinyl acetal resin.

Furthermore, the electrochemical element of this invention is characterized by the ratio with respect to the total amount of a crosslinked material and the said crosslinked material and a nonaqueous electrolyte solution being 3.5 weight% or less.

Furthermore, the electrochemical device of the present invention comprises an active material in which the negative electrode includes an active material capable of occluding and / or discharging lithium metal and / or lithium, and the positive electrode can generate an electromotive force of 3 V or more with respect to the dissolution precipitation potential of lithium. And the nonaqueous electrolyte contains an electrolyte selected from lithium salts.

In addition, the present invention is laminated with a negative electrode, a separator and a positive electrode, filled with the electrochemical device formed by impregnating any one of the above-described non-aqueous electrolyte solution to produce a crosslinked product of a polyvinyl acetal resin, the crosslinked product A method of manufacturing an electrochemical device, characterized in that for bonding the cathode and / or the positive electrode and the separator by the.

Compared with the polyvinyl acetal resin varnish prepared by using the conventional organic solvent, the polyvinyl acetal resin varnish of the present invention has less problems in terms of safety and can have a low viscosity, and can work safely and efficiently. .

In addition, since the polyvinyl acetal resin varnish of the present invention can be used as a gelling agent of an organic solvent, for example, organic fragrance, waste oil, biomolecular polymer material (for example, artificial skin polymer material), lithium battery, electricity Gelling of electrolyte solution etc. in electrochemical elements, such as a double layer capacitor, can be performed.

Implement the invention  Best form for

The present invention includes a polyvinyl acetal resin varnish, a non-aqueous electrolyte, an electrochemical device, and a manufacturing method thereof. Hereinafter, each form is explained in full detail.

Polyvinyl acetal resin varnish of this invention is a solution which melt | dissolves polyvinyl acetal resin in the carbonate ester solvent.

[Polyvinyl Acetal Resin]

Polyvinyl acetal resins are generic terms such as resins obtained by aldehyde acetalization of polyvinyl alcohol, resins obtained by esterification of polyvinyl alcohol, and resins obtained by acetalization and esterification of polyvinyl alcohol.

As polyvinyl acetal resin, it is a general formula, for example.

[Tue 1]

[Wherein, R ₁ represents a hydrogen atom or an alkyl group.]

Vinyl acetal unit (1) represented by

[Tue 2]

Vinyl alcohol unit (2) represented by, and general formula

[Tue 3]

[Wherein, R ₂ represents a hydrogen atom, an alkyl group or an alkyloxy group.]

The polyvinyl acetal resin containing the vinyl carboxylate unit (3) represented by the repeating unit is mentioned. In this polyvinyl acetal resin, 50-80 weight% of vinyl acetal units (1), 0.1-20 weight% of vinyl alcohol units (2), and 10-20 weight% of vinyl carboxylate units (3), respectively. It is easy to obtain to include.

Specific examples of the polyvinyl acetal resin that includes the repeating unit (1) to (3), for example, polyvinyl formal (R ₁ = a hydrogen atom, a vinyl carboxylate unit (3 in the vinyl acetal unit (1) ) R ₂ = methyl group), polyvinyl acetonitrile acetal (plastic R ₂ = methyl group), polyvinyl propynyl LAL (vinyl acetal units in a R ₁ = methyl group, and a vinyl carboxylate unit (3) in the acetal unit (1) according to In (1), R ₁ = ethyl group, R ₂ = methyl group in vinyl carboxylate unit (3), polyvinyl butyral (R ₁ = propyl group, vinyl carboxylate unit (3 in vinyl acetal unit (1)) ) R ₂ = methyl group) and the like. Among these, polyvinyl formal is preferable from the viewpoint of the chemical safety of the varnish obtained.

From the viewpoint of increasing the dissolution concentration in the varnish, the polyvinyl acetal resin according to the present invention preferably has a small number of vinyl alcohol units (2), and has a low molecular weight in a range that does not adversely affect adhesion or coating properties. It is preferable. Here, content of the vinyl alcohol unit (2) of polyvinyl acetal resin becomes like this. Preferably it is 0.1-20 weight%, More preferably, it is 0.5-10 weight%, Especially preferably, it is 1-6 weight%. If the content of the vinyl alcohol unit 2 is significantly less than 0.1% by weight, the coating property of the polyvinyl acetal resin, the adhesiveness, the gelling property of the organic solvent, and the like may decrease. On the other hand, when it exceeds 20 weight% significantly, there exists a possibility that the melt concentration in a varnish may become too low. By the way, the content of the vinyl alcohol unit (2) in the polyvinyl acetal resin depends on the type and production method of the polyvinyl acetal resin, for example, 10-20% by weight in polyvinyl butyral, polyvinyl formal It is about 5 weight%, and a polyvinyl formal side is preferable. Of course, even if it is another polyvinyl acetal resin, if content of the vinyl alcohol unit 2 can be adjusted in the said range, it can use suitably like polyvinyl formal.

In the polyvinyl acetal resin according to the present invention, the vinyl acetal unit (1) and the vinyl carboxylate unit (3) preferably contain many vinyl acetal units (1) from the viewpoint of chemical stability of the varnish. . The content of the vinyl acetal unit 1 is preferably 50 to 99% by weight, more preferably 60 to 95% by weight, particularly preferably 75 to 95% by weight.

The molecular weight of the polyvinyl acetal resin depends on the molecular weight of the polyvinyl alcohol of the raw material, and is represented by the number average degree of polymerization of the vinyl alcohol of the raw material, preferably 50 to 5000, more preferably 100 to 3000, particularly preferably 300 ~ 1500. If the molecular weight of the polyvinyl acetal resin is too small, there is a risk that the coating property, adhesiveness, gelling property of the organic solvent, and the like of the polyvinyl acetal resin are impaired.

Furthermore, among polyvinyl acetal resins, the hydroxyl group content is preferably 0.1 to 2 mol / kg, more preferably 0.3 to 1.5 mol / kg.

In the present invention, polyvinyl acetate, polypropionate vinyl and the like are also included in the polyvinyl acetal.

[Production Method of Polyvinyl Acetal Resin]

Polyvinyl acetal resin can be manufactured by acetalizing and / or esterifying polyvinyl alcohol.

Acetalization of polyvinyl alcohol can be performed according to a well-known method. For example, aldehyde may be applied to polyvinyl alcohol in the presence of an acid catalyst in water. As an aldehyde, a well-known thing can be used, For example, formaldehyde, acetaldehyde, propionaldehyde, butylaldehyde, isobutylaldehyde, etc. are mentioned. Among these, formaldehyde is preferable. Although the usage-amount of an aldehyde can be suitably selected according to polyvinyl alcohol concentration etc., it is 0.1-4 mol, More preferably, it is 0.2-3 mol per liter of reaction solvent (water). Examples of the acid catalyst include sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, trichloroacetic acid, organic sulfonic acid, and the like, and sulfuric acid and hydrochloric acid are preferable. Although the usage-amount of an acidic catalyst can be suitably selected according to the density | concentration of polyvinyl alcohol resin, an aldehyde, etc., per 1 liter of reaction solvent (water), Preferably it is 1-6 gram equivalent, More preferably, it is 2-5 gram equivalent. Acetalization reaction becomes like this. Preferably it is carried out at the temperature of 5-90 degreeC, More preferably, it is 25-80 degreeC, and it finishes in about 1 to 10 hours.

For esterification of polyvinyl alcohol, formic acid esterification, acetic acid esterification, propionic acid esterification, carbonate esterification, 1,2-hydroxy ethylene structure contained in polyvinyl alcohol and / or 1,3-hydroxy-1, Cyclic carbonate esterification of a 3-propylene structure, etc. are mentioned.

Esterification of polyvinyl alcohol can be performed according to well-known methods, such as a transesterification reaction. Regarding esterification, carbonic acid esterification is described as an example. Carbonate esterification can be performed by transesterification of polyvinyl alcohol and dialkyl carbonate directly or by mixing in a solvent in the presence or absence of an esterification catalyst. As the esterification catalyst, those commonly used in the art can be used, and examples thereof include an alkylammonium salt, a pyridinium salt, diazabicycloalkenes, a tertiary amine, an alkylammonium group, and a tertiary amino group. Alkaline catalysts; and the like. The esterification catalyst can use 1 type (s) or 2 or more types. The amount of esterification catalyst used may be appropriately selected from a wide range depending on the amount of polyvinyl alcohol, the type and amount of dialkyl carbonate, the type and amount of solvent, the reaction temperature, the reaction pressure, the reaction time, the target value of the degree of carbonate esterification, and the like. Although preferably, the amount is preferably 50% by weight or less, preferably 30% by weight or less of the total amount of polyvinyl alcohol. Examples of the dialkyl carbonate include dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, di-propyl carbonate, diisopropyl carbonate, di-butyl carbonate, diisobutyl carbonate, disec-butyl carbonate and the like. Although the usage-amount of dialkyl carbonate is not specifically limited, Preferably it is 0.1-20 times molar amount with respect to polyvinyl alcohol, More preferably, it is 0.1-10 times molar amount. As a solvent, each raw material can be melt | dissolved or disperse | distributed, and what is inert to a transesterification reaction can be used, For example, aromatic hydrocarbons, such as aliphatic hydrocarbons, benzene, toluene, and xylene, acetone, methyl ethyl ketone, methyl Ketones such as propyl ketone, halogenated hydrocarbons such as dichloromethane and dichloroloethane, ethers such as zimelim, dioxane, tetrahydrofuran and the like. These solvents can use 1 type (s) or 2 or more types. Carbonate esterification reaction, Preferably it is carried out at the boiling point of the alcohol byproduced by this reaction-the boiling point of the reaction solvent, or 200 degrees C., More preferably, under the temperature of 50-180 degreeC, for 5 minutes-50 hours, Preferably it ends in 10 minutes-30 hours. In addition, this carbonate esterification reaction can be performed also in any pressure under reduced pressure, normal pressure, or pressurization. Other esterification reaction can also be performed similarly to the conventional method, except using raw material compounds other than the corresponding dialkyl carbonate.

Acetalization and esterification of polyvinyl alcohol are carried out by acetalization and esterification of polyvinyl alcohol in the same manner as above.

[Acid Modification of Polyvinyl Acetal Resin]

Although the polyvinyl acetal resin which concerns on this invention can use said polyvinyl acetal resin as it is as a raw material which prepares varnish, it is preferable to perform acid denaturation from the viewpoint of the gelation property of the organic solvent mentioned later or a non-aqueous electrolyte solution. Do. The reason for this is not clear enough, but it is assumed as follows. That is, in the presence state of the vinyl alcohol unit (2) in a polyvinyl acetal resin, the random phase which is independent in a polymer chain, a 1, 2- dihydroxy ethylene structure, or a 1, 3- dihydroxy- 1, 3- propylene When a plurality of contiguous block phases have the same structure, and acid modification is carried out, the intramolecular exchange reaction of the acetal ring takes place, and the structure of the independent vinyl alcohol unit (2) is connected to a plurality of organic solvents. It is estimated that gelation property improves.

As for the acid modified substance of the polyvinyl acetal resin which concerns on this invention, the acid modified substance of polyvinyl formal resin is preferable, Furthermore, it is preferable that hydroxyl group content is 0.1-2 mol per 1 kg of said acid modified substances, and 0.3- It is especially preferable that it is 1.5 mol.

When the hydroxyl group content is in the range of 0.1 to 2 mol, the solubility or homogeneous-swelling property of the acid-modified substance in the nonaqueous electrolyte, the adhesion between the negative electrode and / or the positive electrode and the separator by crosslinking the acid-modified substance, and the like This is particularly good.

In addition, the molecular weight of the acid-modified product of the polyvinyl acetal resin is not particularly limited, but, for example, when used for gelation of the nonaqueous electrolyte solution in an electrochemical device, the main liquidity (injectability) of the nonaqueous electrolyte solution to an electrochemical device is used. In order to improve the adhesive strength and increase the adhesive strength of the laminate composed of the negative electrode, the separator and the positive electrode in the electrochemical device, preferably 0.30,000 to 300,000, more preferably 10,000 to 150,000, particularly preferably 4 It is only 80,000. Here, molecular weight means the number average molecular weight of polystyrene conversion by GPC (gel permeation chromatography) measurement. In addition, the molecular weight of the polyvinyl acetal resin depends on the degree of polymerization of the polyvinyl alcohol of the raw material and the molecular weight of the side chain substituent, and is represented by the number average degree of polymerization of the vinyl alcohol of the raw material, preferably 50 to 5000, more preferably 100 to 3000, Especially preferably, it can also be expressed as 300-1500.

In addition, in order to confirm acid-modification of polyvinyl acetal resin, this inventor measures the ¹ H-NMR spectrum of polyvinyl acetal resin before and after acid-modification. Based on the peak of DMSO-d ₆ (2.49 ppm), it is assumed that acid degeneration was received when the peak appearing in the region of 4 to 5 ppm decreased. It is thought that the peak derived from the hydroxyl group of the vinyl alcohol unit of a polyvinyl acetal resin appears in this area | region, and it is guessed that it is a peak peculiar to an independent hydroxyl group by being stuck in an acetal ring or a carboxyl group. Since acid degeneration results in a decrease in the amount of independent hydroxyl groups, a decrease in peak is observed.

On the other hand, the polyvinyl acetal resin has a 1,2-dihydroxyethylene structure and / or 1,3-dihydroxy derived from a structure in which a plurality of vinyl alcohol units are continuous in the main chain together with the independent hydroxyl groups described above. Hydroxyl groups having a -1,3-propylene structure. When the above independent hydroxyl group decreases, the hydroxide in 1,2-dihydroxyethylene and / or 1,3-dihydroxy-1,3-propylene structure with respect to the total hydroxyl group amount in the polyvinyl acetal resin It is assumed that the proportion of the hydroxyl group is increased relatively and can be increased to 70 mol% or more, more preferably 80 mol% or more by acid denaturation.

Moreover, when polyvinyl formal resin is taken as an example, the peak of 4.25 ppm-4.35 ppm reduces or disappears by acid denaturation. Polyvinyl formal resins usually have 0.3 mol / kg or more of protons corresponding to peaks of 4.25 ppm to 4.35 ppm before acid modification, but 30% or more of protons corresponding to peaks of 4.25 to 4.35 ppm due to acid modification, It is preferably reduced by 50% or more, preferably 0.25 mol / kg or less, and more preferably 0.15 mol / kg or less.

The same measurement is also performed with respect to polyvinyl acetal resins other than the polyvinyl formal resin, and it is assumed that the acid treatment can be judged by examining the change in peak intensity.

[Method of Acid Modification of Polyvinyl Acetal]

Acid modification of polyvinyl alcohol resin is performed by various well-known methods. For example, in a state where the polyvinyl acetal resin is suspended or dissolved in a non-aqueous solvent, a suitable acid catalyst is added and heated under stirring or without stirring.

Although the content in the non-aqueous solvent of the polyvinyl acetal resin is not particularly limited, in consideration of allowing the reaction to proceed smoothly, preferably, 0.2 to 20 of the total amount of the reaction mixture consisting of the polyvinyl acetal resin, the acid catalyst and the non-aqueous solvent Wt%, preferably 1-10 wt%. A well-known acid can be used as an acid catalyst, For example, acetic acid, phosphoric acid, hydrochloric acid, hydrofluoric acid, a sulfuric acid, trifluoroacetic acid, nitric acid etc. are mentioned. Of these, acetic acid, phosphoric acid, sulfuric acid and hydrofluoric acid are preferable. An acid may be used individually by 1 type, or may use 2 or more types together. The amount of the acid to be used is not particularly limited, but is preferably 0.0005 to 1% by weight of the reaction mixture, and more preferably 0.001 to 0.01% by weight.

As the non-aqueous solvent, any one can be used as long as it does not inhibit the intramolecular exchange reaction of the acetal ring, and among these, carbonate esters and carbonate esters are preferable. A nonaqueous solvent can be used individually by 1 type, or can use 2 or more types together. When carbonate ester is used as a reaction solvent, since the solution after completion | finish of reaction can be used as the varnish of this invention as it is, it is more preferable. The reaction between the polyvinyl acetal resin and the acid is preferably performed at a temperature of room temperature to 100 ° C, more preferably 40 to 70 ° C, and preferably ends at 1 to 100 hours, more preferably 5-48 hours. .,

After completion | finish of reaction, the said acid-modified substance is isolate | separated from the reaction mixture containing the acid-modified substance of polyvinyl acetal resin by general purification means, such as reprecipitation, and is used for varnish of this invention.

[Non-aqueous solvent]

Carbonate ester is used as a non-aqueous solvent used for varnish.

Carbonate ester is a solvent which has esterified structure of carbonic acid and alcohol, has low irritation, toxicity, and bad smell, and has a considerably low environmental impact. Moreover, compared with the carboxylic acid ester solvent of a similar structure, flammability is considerably low and it is more safe. For example, the flash point of diethyl carbonate is 31 degreeC with respect to the flash point of 14 degreeC of ethyl acetate, and is more than room temperature. For this reason, the polyvinyl acetal resin varnish of this invention can work more safely than the polyvinyl acetal resin varnish used conventionally.

The carbonic acid ester includes a chain carbonic acid ester in which two substituents are not connected to each other and a cyclic carbonic acid ester having a structure in which two substituents are connected to each other.

Examples of the chain carbonate include dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl n-propyl carbonate, ethyl n-propyl carbonate, din-propyl carbonate, methyl iso-propyl carbonate, ethyl iso-propyl carbonate and diiso-. Propyl carbonate, butyl methyl carbonate, butyl ethyl carbonate, butyl n-propyl carbonate, dibutyl carbonate, methyl-2,2,2-trifluoroethyl carbonate, ethyl-2,2,2-trifluoroethyl carbonate, di (2,2,2-trifluoroethyl) carbonate, methyl-3,3,3,2,2-pentafluoropropylcarbonate, ethyl-3,3,3,2,2-pentafluoropropylcarbonate, Propyl-3,3,3,2,2-pentafluoropropylcarbonate, di (3,3,3,2,2-pentafluoropropyl) carbonate, and the like.

Examples of the cyclic carbonate include ethylene carbonate, 1,2-propylene carbonate, 1,3-propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentene carbonate, and 2,3-pentene Carbonate, 1,2-hexene carbonate, 2,3-hexene carbonate, 3,4-hexene carbonate, n-butylethylene carbonate, n-hexylethylene carbonate, cyclohexyl ethylene carbonate, fluoroethylene carbonate, 1,1-di Fluoroethylene carbonate, 1,2-difluoroethylene carbonate, trifluoromethylethylene carbonate, fluoromethylethylene carbonate, difluoromethylethylene carbonate, chloroethylene carbonate and the like.

Among the carbonate esters exemplified above, carbonate esters having a small molecular weight are preferred from the viewpoint of solubility and varnish viscosity of the polyvinyl acetal resin. As such carbonate esters, ethylene carbonate, 1,2-propylene carbonate, 1,3-propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl n-propyl carbonate, ethyl-n-propyl carbonate, din- Propyl carbonate, methyl iso-propyl carbonate, ethyl iso-propyl carbonate, diiso-propyl carbonate, di-n-propyl carbonate and the like are preferred, and ethylene carbonate, 1,2-propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, di Ethyl carbonate and the like are more preferred, and ethylene carbonate and 1,2-propylene carbonate are most preferred.

Although the linear carbonate ester and the cyclic carbonate may be used alone or in combination thereof, in order to further improve the solubility of the polyvinyl acetal resin, it is preferable to use a mixed solvent of the chain carbonate ester and the cyclic carbonate ester. When only one of the chain carbonate or cyclic carbonate is used, the polyvinyl acetal resin may be dissolved by limiting the molecular weight and chemical structure of the polyvinyl acetal resin to a specific one or by heating the varnish. Can be. Here, to increase the solubility of the polyvinyl acetal resin, for example, to dissolve the polyvinyl acetal resin at a higher concentration, to be able to dissolve regardless of the type of polyvinyl acetal resin, at the time of dissolution Means no heating at the time), no precipitation of the polyvinyl acetal resin, etc., even if the varnish temperature is lowered to room temperature or less after varnish preparation.

When a mixed solvent of cyclic carbonate and chain carbonate is used, the solubility of the polyvinyl acetal resin is extremely improved, the dissolution concentration in the varnish of the polyvinyl acetal resin is greatly improved, and the viscosity of the varnish can be lowered. have.

Although the reason for such an effect is not clear, the cyclic carbonate melt | dissolves the polar part of a polyvinyl acetal resin, the chain carbonate ester melt | dissolves a nonpolar part, and further, the mutual relationship of a cyclic carbonate and a chain carbonate ester is carried out. It is thought that it is because solubility is extremely good.

As a mixed solvent of the cyclic carbonate and the chain carbonate, ethylene carbonate and / or 1,2-propylene carbonate are used as the cyclic carbonate, and dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, The use of dimethyl carbonate and ethyl methyl carbonate, diethyl carbonate and ethyl methyl carbonate is exemplified. In these, since the solubility of polyvinyl acetal resin improves, the combination containing ethylene carbonate is preferable.

The volume compounding ratio (cyclic carbonate: chain carbonate) between the cyclic carbonate and the chain carbonate can be appropriately selected from a wide range depending on the type and concentration of the polyvinyl acetal resin to be dissolved, but preferably 1: 19-19: 1, More preferably, it is 1: 4-9: 1, Especially preferably, it is 1: 3-3: 1. By setting it as such a range, the dissolution concentration in the varnish of polyvinyl acetal resin can be raised, and the viscosity of a varnish can be made lower.

Moreover, the moisture content of a nonaqueous solvent is 200 ppm or less, Preferably it is 50 ppm or less, More preferably, it is 20 ppm or less. If it exists in this range, the moisture content of polyvinyl acetal resin varnish will be suppressed low and a favorable varnish will be obtained.

[Polyvinyl Acetal Resin Varnish]

The polyvinyl acetal resin varnish of this invention consists of said polyvinyl acetal or its acid modified substance, and a carbonate ester solvent.

The concentration of the polyvinyl acetal resin in the varnish of the present invention is not particularly limited and can be appropriately selected from a wide range depending on the kind of the polyvinyl acetal resin, the use of the varnish to be obtained, and the like. In consideration of the viscosity of the varnish, the polyvinyl acetal resin is preferably 0.2 to 20% by weight, more preferably 1 to 10% by weight, particularly preferably 1 to 5% by weight, based on the total amount of varnish. Concentration can be variously selected in this range according to a use.

Moreover, the kind of polyvinyl acetal resin is taken into consideration in the solubility with respect to the said nonaqueous solvent, the viscosity of a varnish, the gelation property of the organic solvent mentioned later, among the things melt | dissolving in the said nonaqueous solvent according to the kind of nonaqueous solvent used. It is chosen appropriately.

As for the moisture content of the varnish of this invention, it is preferable that it is small from a viewpoint of gelatinization, such as the organic solvent mentioned later and the non-aqueous solvent in an electrochemical element. On the other hand, when the amount of water is too small, the varnish may gel, so it is necessary to contain an appropriate amount of water. For this purpose, preferably 2 ppm or more and 200 ppm or less, more preferably 2 ppm or more and 100 ppm or less, particularly preferably 5 ppm or more and 50 ppm or less. As a method of reducing the amount of moisture contained in the varnish, a method of reducing the amount of moisture contained in the nonaqueous solvent and the polyvinyl acetal resin in advance, a small amount of the nonaqueous solvent in the varnish is distilled out, and the water is allowed to flow out of the azeotrope with the nonaqueous solvent. And a method of removing the water by treating the varnish with a dehydrating agent. As a dehydrating agent, moisture adsorption agents, such as anhydrous sodium sulfate, a molecular sieve, and a silica gel, are mentioned, for example. The moisture adsorbent is filled into the column and passed through the varnish or mixed with the varnish and stirred to remove moisture from the varnish. By these methods, the moisture content in the varnish can be 50 ppm or less.

Varnishes of the present invention are solvents other than carbonates and polyvinyl acetal resins in a range that does not impair the desirable properties (for example, a range that is not so high that it does not interfere with work irritant, toxic, flammable, etc.). You may also include the synthetic resin. Examples of solvents other than carbonate include water, alcohols, carboxylic acid esters, ethers, amides, carbamic acid esters, phosphoric acid esters, aromatic hydrocarbons, and fluorine-substituted hydrocarbons. Moreover, as synthetic resins other than polyvinyl acetal resin, if it melt | dissolves uniformly in nonaqueous solvents, such as carbonate ester, and it does not impair the adhesiveness, coating property, and gelation property of polyvinyl acetal resin, it will not specifically limit, For example, polyester, polycarbonate, polyether, polyimide, etc. are mentioned.

Next, the use of the polyvinyl acetal resin varnish of the present invention will be described.

[Gelation of Organic Solvents with Polyvinyl Acetal Resin Varnish]

The polyvinyl acetal resin varnish of the present invention can be used as a gelling agent for gelling various organic solvents. The gelling agent of the present invention can gel an organic solvent even if the concentration of the polyvinyl acetal resin is in a small amount such as 1 to 2% by weight. Based on this property, the varnish of the present invention can be, for example, a gelling agent such as a non-aqueous electrolyte in an electrochemical device such as a biomolecule polymer material such as an organic fragrance or an artificial skin material, a lithium battery, or an electric double layer capacitor. It can be used as. For example, when used for gelation of a nonaqueous electrolytic solution, it is effective for the prevention of liquid leakage of an electrochemical device, and the shape freedom of an electrochemical device can be improved.

The mechanism in which the organic solvent gels with the polyvinyl acetal resin varnish of the present invention is not necessarily clear. However, when the water in the organic solvent is removed while the polyvinyl acetal resin is uniformly dissolved in the organic solvent, the vinyl alcohol of the polyvinyl acetal resin It is considered that the hydroxyl groups of the unit (2) strongly interact with each other to bond similarly and form a mesh structure of a three-dimensional polyvinyl acetal resin in an organic solvent.

It is preferable that the gelling agent of this invention has a small moisture content, Preferably it is 200 ppm or less, More preferably, it is 100 ppm or less, Especially preferably, it is good to set it as 50 ppm or less. A dehydrating agent is used to remove the moisture contained in the varnish. As the dehydrating agent, a reactive dehydrating agent is preferable in order to completely or almost completely remove the moisture in the varnish and the organic solvent. Examples of such dehydrating agents include silyl esters, boric acid esters, disilazanes, isocyanates, organometallic compounds, and metal alkoxides. The amount of the dehydrating agent added is determined in consideration of the amount of water in the mixture of the polyvinyl acetal resin varnish and the organic solvent to gel. Usually, it is preferable to add 1-100 times the amount equivalent to reaction with containing water, Preferably it is 10-50 times.

[Non-aqueous electrolyte]

The nonaqueous electrolyte of this invention contains the polyvinyl acetal resin varnish of this invention and electrolyte as an essential component. The nonaqueous electrolyte of the present invention may contain a compound that generates an acid together with the essential component.

The polyvinyl acetal resin may be acid-modified or not acid-modified, but is more preferably acid-modified. When the polyvinyl acetal resin varnish of the present invention is used, gelation of the nonaqueous electrolyte is likely to occur, and adhesion between the negative electrode and / or the positive electrode and the separator of the electrochemical device described later is increased.

(a) Varnish containing polyvinyl acetal resin

The varnish containing polyvinyl acetal resin melt | dissolves the above-mentioned polyvinyl acetal resin in a nonaqueous solvent.

The carbonate ester solvent used to varnish the polyvinyl acetal resin also acts as a nonaqueous electrolyte solvent for dissolving or dispersing the electrolyte in the nonaqueous electrolyte of the present invention. As a non-aqueous solvent used for the varnish of this invention, although carbonate ester is used as mentioned above, when using it for a non-aqueous electrolyte solvent, it can also contain the non-aqueous solvent compatible with this field other than carbonate ester.

As non-aqueous solvents other than carbonate ester, For example, cyclic carboxylic acid esters, such as (gamma) -butyrolactone, chain carboxylic acid esters, such as methyl acetate, methyl propionate, pentafluoropropyl acetate, and a methyl trifluoro acetate , Ethers such as dimethoxyethane and tetrahydrofuran, amides such as N-methylpyrrolidone and dimethylformamide, carbamates such as methyl-N, N-dimethyl carbamate and N-methyloxazolidinone, Ureas such as N, N-dimethylimidazolidinone, boric acid esters such as triethyl borate and tributyl borate, phosphoric acid esters such as trimethyl phosphate and trioctyl phosphate, benzene, toluene, xylene, fluorobenzene, and fluorine Aromatic hydrocarbons such as rotoluene, chlorobenzene, biphenyl and fluorobiphenyl; and fluorinated ethers such as trifluoroethylmethyl ether. A nonaqueous solvent can be used individually by 1 type, and can use 2 or more types together. These non-aqueous solvents include those having irritation, toxicity, environmental pollution, odor, flammability, and the like, but the non-aqueous electrolyte is used in a sealed state inside the electrochemical device, and the amount thereof is also small.

(b) Content in nonaqueous electrolyte of polyvinyl acetal resin

The content of the polyvinyl acetal resin in the non-aqueous electrolyte is not particularly limited, but the reduction in ionic conductivity, load characteristics, and high temperature storage characteristics of the electrochemical device is prevented as much as possible, and the mechanical strength of the laminate of the negative electrode, the separator, and the positive electrode is reduced. From the viewpoint of increasing as much as possible, Preferably it is 0.3-3.5 weight% of the total amount of non-aqueous electrolyte, More preferably, it is 0.7-2.3 weight%.

Further, in the present invention, the square root of the number average molecular weight λ of the polyvinyl acetal resin (λ ¹⁾ from the viewpoint of further increasing the injection property of the nonaqueous electrolyte into the electrochemical device, the adhesive strength of the laminate composed of the negative electrode, the separator and the positive electrode, and the like. ^{/ 2),} a polyvinyl product with a concentration c (wt.%) in the non-aqueous electrolyte solution of the acetal resin ^(1/2 × λ c) is preferably 100 ~ 1000 (100≤λ ^1/2 × c≤1000 ), And more preferably in the range of 200 to 800 (200 ≦ λ ^1/2 × c ≦ 800). Here, a number average molecular weight means the number average molecular weight of polystyrene conversion by a gel permeation chromatography (GPC) measurement. The conditions of gel permeation chromatography are as follows. A differential refractive index detector is used for the detector, Shoudex KF-805L (trade name) x 2 as the separation column, and Shoudex KF-800P (trade name) as the free column, and tetrahydrofuran as the carrier solvent. Polystyrene of the molecular weight standard and 20 mg of polyvinyl acetal resin of a sample are dissolved in 20 ml of tetrahydrofuran, and it is set as a sample. The flow rate of the carrier solvent is 1 ml / min, and 100 ul of the sample is injected at 30 ° C to obtain a chromatogram.

(b) electrolyte

The electrolyte can be appropriately selected and used among those commonly used in this field depending on the type of electrochemical device. When the nonaqueous electrolyte of the present invention containing, for example, a lithium salt is used as the electrolyte, a lithium battery excellent in charge and discharge load characteristics and shape retention is obtained. Moreover, when the nonaqueous electrolyte solution of this invention containing an alkylammonium salt is used as electrolyte, the electric double layer capacitor which is excellent in charge / discharge load characteristic and shape retention is obtained. The content in the nonaqueous electrolyte of the electrolyte can be appropriately selected from a wide range depending on the type of electrolyte and the type of electrochemical device, but is usually 0.1 to 10 mol / liter, preferably 0.3 to 3 mol / liter.

(c) compounds that produce acids

In addition to the polyvinyl acetal resin varnish and electrolyte, it is preferable to add a compound which produces an acid to the nonaqueous electrolyte of the present invention. The compound which produces | generates an acid mainly contains the aldehyde group which the hydroxyl group in the main chain of polyvinyl acetal resin electrolytically oxidizes by electricity supply in a filling process, and the 1,2-dihydroxyethylene structure or 1,3 in a main chain. It shows the action of catalyzing the reaction with hydroxyl groups which avoid electrolytic oxidation in the dihydroxy-1,3-propylene structure. Acid modification of the polyvinyl acetal resin can also be performed. Therefore, even if the polyvinyl acetal resin contained in the nonaqueous electrolytic solution is not acid-modified, if an acid-producing compound is added, an acid may be added to generate water or an acid is generated in the filling step and the aging step. Acid-modified polyvinyl acetal resin can also be made. However, it is preferable to add the polyvinyl acetal resin varnish to which the polyvinyl acetal resin was acid-modified previously from a viewpoint of raising the adhesive strength of the laminated body which consists of a negative electrode, a separator, and a positive electrode to a nonaqueous electrolyte.

In the nonaqueous electrolyte of the present invention, the use of a compound that generates an acid can easily cause gelation of the nonaqueous electrolyte, and can improve the adhesion between the negative electrode and / or the positive electrode and the separator of the electrochemical device described later.

Examples of the compound that generates an acid include a compound that generates an acid by reaction with water, a compound that is electrolytically oxidized in the operating voltage range of an electrochemical device, and the like, but an acid is generated by reaction with water. Particularly preferred are compounds to be added.

The compound which produces | generates an acid by reaction with water produces | generates an acid by reacting with the moisture which remain | survives in the separator and electrode of an electrochemical element. Generation of acid can be accelerated by heating of the aging step. In addition, in the current technology, it is not possible to completely remove the moisture in the electrochemical device. As such a compound, a well-known compound which produces | generates an acid by reaction with water can be used, For example, Lewis acid, Lewis acid salt, sulfuric acid ester, nitrate ester etc. which have a halogen atom are mentioned. As a Lewis acid having a halogen atom, for example,

Fluorine, chlorine, bromine, etc. are mentioned as a halogen atom, A fluorine atom is preferable in consideration of the influence on corrosion resistance of an electrochemical element, etc. Examples of the sulfate esters include 1,3-propanesultone, methyl benzenesulfonate, 1,3-propa-2-enesultone, 1,4-butanesultone, dimethyl sulfate, diethyl sulfate, and ethylene sulfate. Can be mentioned. As nitrate ester, a nitrate ether etc. are mentioned, for example. Among these, Lewis acids and Lewis salts having a halogen atom are preferable, and considering the handleability and availability, LiPF ₆ , LiBF ₄ , R ₄ NPF ₆ (R = organic), R ₄ NBF ₄ (R = Organic group), SiF _n R _(4-n) (n = 1 to 4, R = organic), and the like are more preferable. LiPF ₆ , LiBF ₄ , R ₄ NPF ₆ (R = organic), R ₄ NBF ₄ (R = organic) and the like are particularly preferable because they act as electrolyte salts of electrochemical devices. The said compound can be used individually by 1 type, or can use 2 or more types together. Content in the nonaqueous electrolyte of the compound which generate | occur | produces an acid by reaction with water is suitably selected according to the kind of electrochemical element. In the case where the electrochemical device is a lithium battery, for example, there is a fear of deterioration in battery characteristics due to the compound, so that the content of the compound in the nonaqueous electrolyte is 0.2 mol / liter or less, preferably 0.05 mol / liter or less. However, when the electrochemical device is a lithium battery, and the compound is a Lewis acid or a Lewis acid salt having a fluorine atom, and a lithium salt, adverse effects on the properties are less likely to appear, and therefore, it may be contained in excess of 0.2 mol / liter.

Compounds electrolytically oxidized in the operating voltage range of the electrochemical device may be electrolytically oxidized in the initial charging process of the electrochemical device to generate an acid and contribute to crosslinking of the polyvinyl acetal resin. As such a compound, for example, water, methanol, ethanol, propanol, ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, toluene, diphenylmethane, cyclohexylbenzene, acetone, malonic esters, polyvinyl alcohol Protic compounds, such as these, etc. are mentioned. The said compound can be used individually by 1 type, or can use 2 or more types together. What is necessary is just to select suitably the voltage applied at the time of initial charge in the operating voltage range of an electrochemical element, and the compound electrolytically oxidizes. For example, with respect to the dissolution precipitation potential of lithium, the compound to be electrolytically oxidized is 3 V or more in the case of alcohols, and 4 V or more in the case of aromatic compounds. The content in the non-aqueous electrolyte of the compound to be electrolytically oxidized can be appropriately selected from a wide range depending on the kind of electrochemical device, the kind of the crosslinkable polymer material present in the laminate composed of the negative electrode, the separator, and the positive electrode, but usually 0.002 to 0.1 Moles / liter, preferably 0.005 to 0.05 moles / liter.

Moreover, the compound which produces | generates an acid by reaction with said water, and the compound electrolytically oxidized in the operating voltage range of an electrochemical element can also be used together.

Among these, the compound which generate | occur | produces an acid by reaction with water is preferable, and the Lewis acid and Lewis acid salt which have a halogen atom are especially preferable.

(d) Preparation of nonaqueous electrolyte

The nonaqueous electrolyte of this invention can be adjusted to a desired composition according to a conventional method. For example, another nonaqueous electrolyte comprising a lithium salt and a nonaqueous electrolyte solvent is prepared in advance, and the polyvinyl acetal resin varnish and the acid-producing compound of the present invention are mixed and dissolved in the polyvinyl acetal resin varnish of the present invention. The method of mixing and dissolving the compound which produces | generates a lithium salt and an acid, the method of mixing and dissolving the non-aqueous solvent, the compound which produces | generates a lithium salt and an acid in the polyvinyl acetal resin varnish of this invention, etc. are mentioned. Among these, the method of preparing the other nonaqueous electrolyte which consists of a lithium salt and a nonaqueous solvent beforehand, and mixing and dissolving the compound which produces | generates the polyvinyl acetal resin varnish and acid of this invention to this is most preferable from a viewpoint of workability. However, the compound which produces | generates an acid is added as needed. Usually, the nonaqueous electrolyte solution obtained as mentioned above is inject | poured in an electrochemical element.

Moreover, the nonaqueous electrolyte of this invention produces the laminated body which makes a polyvinyl acetal resin exist in a separator, between a negative electrode and / or a positive electrode, and a separator, and melt | dissolves electrolyte in the non-aqueous solvent in this laminated body in general. It can also be prepared by injecting a nonaqueous electrolyte (does not contain polyvinyl acetal resin). The nonaqueous electrolyte of the present invention is obtained by contacting the general nonaqueous electrolyte and the polyvinyl acetal resin injected into the laminate and dissolving or swelling the polyvinyl acetal resin in the nonaqueous electrolyte.

When employing such a preparation method, after injecting a general nonaqueous electrolyte into the laminate, it is preferable to leave it for a while in order to sufficiently dissolve or swell the polyvinyl acetal resin. There is no restriction | limiting in particular in neglect condition, Taking into consideration that a metal component elutes from a metal tube, an electrical power collector, etc., for example, half day-2 days at room temperature, several hours-1 day at 45 degreeC, 1-at 60 degreeC, for example. Several hours.

[Electrochemical device]

The electrochemical device of the present invention comprises a negative electrode, a separator, a positive electrode and a nonaqueous electrolyte, and the negative electrode and / or the positive electrode and the separator are bonded by an adhesive layer made of a crosslinked product of polyvinyl acetal resin. Especially, it is preferable that the contact bonding layer is formed between the electrode of both a cathode and an anode, and a separator.

The adhesive layer may be formed so as to cover the entire surface of the negative electrode and the separator, or the positive electrode and the separator, or may be formed in an arbitrary pattern on a part thereof.

In the electrochemical device of the present invention, the crosslinked product of the polyvinyl acetal resin is preferably 3.5 wt% or less, more preferably 0.3 to 3.5 wt%, based on the total amount of the nonaqueous electrolyte solvent, the electrolyte, and the total amount of the crosslinked product. In particular, it is contained in the ratio of 0.5 to 2.5 weight%. When it exists in this range, since the characteristic as an electrochemical element is prevented from falling, and the adhesive strength of the laminated body which consists of a negative electrode, a separator, and a positive electrode is prevented from falling, it is especially effective. Moreover, since the adhesiveness of an electrode and a separator improves rather than the substance in which the polyvinyl acetal resin is acid-modified, the said crosslinked material is preferable.

The crosslinked product of the polyvinyl acetal resin can impart sufficient shape retention to the electrochemical device at least in the amount of addition, so that the movement of ions between the positive electrode and the negative electrode is not inhibited by the crosslinked product. In other words, in the use of a small amount of the crosslinked product, since sufficient shape retention can be imparted to the electrochemical device, it is possible to minimize the decrease in ionic conductivity due to the presence of the crosslinked product and to obtain an electrochemical device having excellent charge and discharge load characteristics. Can be. In addition, the crosslinked product is an electrochemical device which is excellent in shape retaining ability and high temperature holding property in a wide temperature range without fear of melting or melting in a nonaqueous electrolyte solution even when the electrochemical device is exposed to high temperature. Can be obtained.

The electrochemical element of this invention contains the nonaqueous electrolyte of this invention. However, the polyvinyl acetal resin in the nonaqueous electrolyte is a crosslinked product by energization in the filling step. When the polyvinyl acetal resin is acid-modified, it is more likely to be subjected to electrolytic oxidation by energization than a substance which is not acid-modified to form a crosslinked product. In addition, since the non-aqueous electrolyte containing acid-modified polyvinyl acetal resin has higher adhesive strength than the non-aqueous electrolyte containing polyvinyl acetal resin that does not undergo acid denaturation, the non-aqueous electrolyte contains polyvinyl acetal resin that does not undergo acid denaturation. With a small amount, it is possible to increase the mechanical strength of the electrochemical device, improve its shape retention and high temperature storage. In addition, since the content of the acid-modified substance can be considerably reduced, even if the non-aqueous electrolyte is gelated at the time of crosslinking by energization, gelation does not occur as much as it inhibits the movement of ions, and thus the ion conductivity of the non-aqueous electrolyte is not practically impaired. It does not fall as much as giving, and it has the advantage that the electrochemical element excellent in the electrical load characteristic and the charge / discharge characteristic is obtained.

The negative electrode used in the electrochemical device of the present invention includes a negative electrode active material and a negative electrode current collector. Although a negative electrode active material is conventionally used in this field according to the kind of electrochemical element, 1 type, or 2 or more types can be suitably selected and used out of it. As a negative electrode electrical power collector, copper, nickel, stainless steel, aluminum, titanium, etc. are mentioned, for example.

The negative electrode is formed into a negative electrode current collector by molding a composition containing a negative electrode active material and a binder into a desired shape, or adding a solvent to a composition containing the negative electrode active material and a binder to form a negative electrode slurry, which is then negative electrode. After coating and drying on one side of the current collector, if necessary, pressing is carried out to increase the packing density of the negative electrode active material, and the negative electrode active material coated with the negative electrode active material or the binder is molded into a desired shape by roll molding, compression molding, or the like. It can be created according to the method.

As a binder used in these methods, what is commonly used in this field can be used, For example, latexes, such as a fluororesin, cellulose, rubber, etc. are mentioned. As the solvent, those which are commonly used in this field can be used, for example, water, N-methylpyrrolidone, dimethylacetamide, dimethylformamide, propylene carbonate, γ-butyrolactone, N-methyloxazolidinone and the like. Can be mentioned. A solvent may be used individually by 1 type, or may use 2 or more types together as needed.

Moreover, as a negative electrode, after raising the active material packing density of a negative electrode active material layer, it is preferable to provide the coating layer containing said polyvinyl acetal resin on the surface of a negative electrode active material layer. By using such a negative electrode, the side reaction which arises on the surface of a negative electrode is suppressed, and the capacity | capacitance as an electrochemical element of the electrochemical element obtained can be enlarged.

The positive electrode used in the electrochemical device of the present invention comprises a positive electrode active material and a positive electrode current collector. Although the positive electrode active material is commercially available in this field according to the kind of electrochemical element, 1 type, or 2 or more types can be selected suitably from these, and can be used. As the positive electrode current collector, a passive film is formed on the surface by anodization in a nonaqueous electrolyte, such as Al, Ti, Zr, Hf, Nb, Ta, or an alloy containing two or more thereof. The metal to form etc. are mentioned. The positive electrode may contain a conductive assistant. A well-known thing can be used as a conductive support agent, For example, carbon black, amorphous whisker, graphite, etc. are mentioned. The positive electrode can be produced in the same manner as in the manufacturing method of the negative electrode, except that a positive electrode active material is used instead of the negative electrode active material, and a positive electrode current collector is used instead of the negative electrode current collector.

The separator used in the electrochemical device of the present invention is a membrane that electrically insulates the positive electrode and the negative electrode and transmits ions. Although various known ones can be used, a porous membrane can be suitably used. Examples of the material of the porous membrane include polyolefin, polyimide, polyvinylidene fluoride, polyester, and the like, and the shape of the microporous membrane includes a microporous film, a nonwoven fabric, and the like. It is preferable that the separator which concerns on this invention is a porous polyolefin film, and a porous polyethylene film, a porous polypropylene film, or a multilayer film of a porous polyethylene film and a porous polypropylene film is especially preferable. The surface of the porous membrane may be coated with a resin other than excellent thermal stability.

The electrochemical device of the present invention includes, for example, a battery such as a lithium secondary battery, a lithium primary battery, a magnesium battery, a calcium battery, an aluminum electrolytic capacitor, an electric double layer capacitor, an electrochemical capacitor, and the like.

As described above, the electrochemical device of the present invention is excellent in electrical load characteristics, charge and discharge characteristics, shape retention properties and high temperature storage properties, and exhibits high mechanical strength. In addition, the electrochemical device of the present invention is easy to thin, and even if used for a long time, sufficient electrical load characteristics and charge / discharge characteristics can be maintained, and there is no worry of liquid leakage or damage, so that a special structure is provided to prevent them. There is no need to do it.

[Method of manufacturing electrochemical device]

In the electrochemical device of the present invention, a non-aqueous electrolyte containing a polyvinyl acetal resin component is impregnated into a laminate including a negative electrode, a separator, and a positive electrode, and then electrolytically oxidizes the polyvinyl acetal resin by energizing in a filling step. It is obtained by making it a crosslinked material. The biggest characteristic of the manufacturing method of this invention is to bridge | crosslink polyvinyl acetal resin by triggering a filling operation, and to bond a negative electrode and / or a positive electrode, and a separator. Here, a polyvinyl acetal resin component is a mixture of a) polyvinyl acetal resin or b) polyvinyl acetal resin, and the compound which produces | generates an acid.

In the manufacturing method of the electrochemical device of the present invention, a laminate containing a cathode, a separator, and a cathode is housed in an electrochemical device housing, and then a nonaqueous electrolyte is injected into the stack to seal the housing. Although a general method for producing an electrochemical device for initial charging and aging is taken, the nonaqueous electrolyte of the present invention is used as the electrolyte. The polyvinyl acetal resin contained in the non-aqueous electrolyte can be crosslinked by energization in the initial filling step to produce the electrochemical device of the present invention.

The polyvinyl acetal resin may be acid-modified even when acid-modified, but is acid-modified because crosslinking of the polyvinyl acetal resin is liable to occur in the energizing step and the adhesion between the negative electrode and the separator and / or the positive electrode and the separator is high. Preferred materials are preferred. In the case where the polyvinyl acetal resin is not acid-modified, if the nonaqueous electrolyte contains an acid-producing compound, the acid and the polyvinyl acetal resin are acid-modified by generating an acid in the nonaqueous electrolyte in the filling step and the aging step. Crosslinking easily occurs.

According to the production method of the present invention, an electrochemical device having the same or higher adhesive strength of the components constituting the electrochemical device can be obtained in a much smaller amount of polyvinyl acetal resin than the conventional gel polymer electrolyte. Furthermore, even if the polyvinyl acetal resin crosslinks to gel the non-aqueous electrolyte, since the amount of the crosslinked product is very small, there is almost no inhibition of movement of ions in the non-aqueous electrolyte, and thus the high ionic conductivity of the non-aqueous electrolyte is sufficiently exhibited. In addition, an electrochemical device having excellent electrical load characteristics can be obtained.

Moreover, although the following method is mentioned as a method of obtaining the electrochemical element of a similar structure, it is not preferable. In the method of injecting the nonaqueous electrolyte after adhering the electrode and the separator in advance with an adhesive, it is very difficult to inject the nonaqueous electrolyte. In addition, after swelling in the non-aqueous electrolyte solution and applying the adhesive showing the adhesive property to the electrode and the separator for the first time, the non-aqueous electrolyte is injected into the separator to bond the electrode and the separator. Such an adhesive has a swelling property to the non-aqueous electrolyte solution. Since it is high, when exposed to high temperature or stored for a long time, it will melt | dissolve in a nonaqueous electrolyte solution and adhesiveness will fall.

Since the manufacturing method of this invention is performed in the normal process of manufacturing an electrochemical element, and does not need to add a new process, the general manufacturing equipment of an electrochemical element can be used as it is, and it can be made into a simple manufacturing process. have.

1) A step of injecting a nonaqueous electrolyte into a laminate comprising a cathode, a separator, and an anode

In the present invention, first, the negative electrode, the separator, and the positive electrode are laminated. This laminated body is formed in arbitrary shapes, such as cylindrical shape, coin shape, square shape, and film form, as needed, and is accommodated in the housing | casing for electrochemical elements, such as a bag made of a metal tube and a metal laminate film. The nonaqueous electrolyte of the present invention is injected into the laminate. As the injection, a general injection method of the nonaqueous electrolyte can be adopted.

In addition, since it is necessary to have fluidity | liquidity in order to inject | pour a nonaqueous electrolyte into a laminated body, it is preferable that the acid amount of a nonaqueous electrolyte is kept low until it injects into a laminated body. "Acid" as used herein is a compound which gradually degrades an acid denatured substance, and is not a compound which produces an acid. An acid is mainly contained as an impurity in each component contained in a nonaqueous electrolyte, and hydrogen fluoride is illustrated. Specifically, the amount of acid in the nonaqueous electrolyte is usually 20 mmol / liter or less, preferably 5 millimoles / liter or less, and more preferably 2 mmol / liter or less. If the amount of acid is large, there is a possibility that the acid denatured material is crosslinked or deteriorated before the nonaqueous electrolyte is injected into the laminate, and the nonaqueous electrolyte is thickened, so that the injection into the laminate becomes difficult.

In the laminate, for example, a polyvinyl acetal resin is present between the cathode and the separator, between the anode and the separator, and in the separator, and the laminate contains components other than the polyvinyl acetal resin. The nonaqueous electrolyte solution (that is, the solvent and the acid generating compound added as needed) may be injected. The polyvinyl acetal resin can be used in the form of a bead, a powder or a pellet, or a sheet or a film containing a polyvinyl acetal resin. In these cases, since the polyvinyl acetal resin does not have to be dissolved in the nonaqueous electrolyte, the viscosity of the nonaqueous electrolyte is not increased, and the injection into the laminate becomes easy, and thus an electrochemical device can be easily obtained. Also in this case, it is preferable to make the acid amount of a nonaqueous electrolyte liquid into the said range.

Moreover, you may form the coating layer containing polyvinyl acetal resin on the surface of the negative electrode active material layer of a negative electrode, the both surfaces or one surface of a separator, or the surface of the positive electrode active material layer of a positive electrode. Even by this, manufacture of the electrochemical element of this invention can be simplified. The coating layer is coated with a solution or slurry in which a polyvinyl acetal resin is dissolved or dispersed in an organic solvent, or the varnish of the present invention is applied to the surface on which the coating layer is to be formed, for example, by heating or the like according to a known method. It can form by removing a solvent. As an organic solvent used here, the well-known thing which can disperse | distribute or disperse | distribute the acid-modified substance of polyvinyl acetal resin uniformly can be used, without corroding a negative electrode active material or a positive electrode active material, For example, propylene carbonate and ethylene Carbonate, N-methylpyrrolidinone, dimethylformamide, gamma -butyrolactone, and the like. Moreover, the method of thermally spraying polyvinyl acetal resin, the method of sputtering polyvinyl acetal resin, the method of crimping polyvinyl acetal resin, etc. are mentioned. Moreover, you may use polyvinyl acetal resin as a part or all part of the binder for forming an active material layer, and may contain polyvinyl acetal resin in a negative electrode active material layer.

When polyvinyl acetal resin is present in a laminate composed of a negative electrode, a separator, and a positive electrode, the amount of polyvinyl acetal resin to be used is appropriately selected depending on the volume and porosity of the electrochemical device, the liquid amount of the non-aqueous electrolyte, and the like. Can be. When the amount of the polyvinyl acetal resin used is too small, the adhesive strength is weakened, and when too large, the ion migration in the nonaqueous electrolyte may be inhibited.

When the coating layer of polyvinyl acetal resin is formed on the surface of the negative electrode active material layer of the negative electrode, electrolysis of the nonaqueous electrolyte which occurs on the surface of the negative electrode active material layer is suppressed, and as a result, the first charge and discharge to the negative electrode The charging and discharging efficiency is improved, and the effect of increasing the capacity of the electrochemical device is also obtained. Although the reason is not clear enough, it is presumed that the diffusion of the non-aqueous solvent molecules to the surface of the negative electrode active material layer is suppressed or the protective layer formed on the surface of the negative electrode active material layer at the time of initial charging is stabilized. This effect becomes further remarkable by forming the coating layer containing polyvinyl acetal resin after raising the packing density of a negative electrode active material layer. As a method for increasing the packing density, for example, a method of press-pressing the negative electrode, a method of selecting the particle size distribution of the negative electrode active material to be the most capable of filling, forming a negative electrode active material layer by a plating method or a CVD method, the negative electrode active material And a method of increasing the packing density by controlling the formation rate, the feed rate, and the like. For example, the porosity is used as an index of the packing density in the negative electrode active material layer. The lower the porosity, the higher the packing density. In the present invention, the packing density may be increased so that the porosity of the negative electrode active material layer is 0.05 to 0.95, preferably 0.1 to 0.9, and more preferably 0.1 to 0.5. Moreover, when giving priority to suppressing electrolysis of a nonaqueous electrolyte, the usage-amount of polyvinyl acetal resin is 0.5-20 mg per 1 m <2> of surface area of a negative electrode active material layer, Preferably it is 1-5 mg.

In addition, the porosity in this invention is a value calculated | required by (V1-VO) / V1 when the volume which subtracted the volume of solid and V1 and the volume which subtracted the weight of the said solid is VO.

2) Process of Crosslinking Polyvinyl Acetal Resin by Filling

The electrochemical device of the present invention, after the non-aqueous electrolyte is injected into the laminate as described above, the electrochemical device is sealed, and in the aging step for the purpose of initial charging and stabilizing the characteristics of the electrochemical device, poor determination, etc. to provide.

In the state in which the nonaqueous electrolyte is injected into the laminate, the polyvinyl acetal resin is present in the state dissolved or swelled in the nonaqueous electrolyte, and the electrode and the separator do not adhere. By energizing in an initial stage of charging, a polyvinyl acetal resin crosslinks and adhere | attaches an electrode and a separator. At this time, when the nonaqueous electrolyte of the present invention contains a compound that generates an acid, crosslinking of the polyvinyl acetal resin proceeds more smoothly, and acid modification and crosslinking of the polyvinyl acetal resin occur.

In order to bridge | crosslink polyvinyl acetal resin, in the charging process, it is good to charge the positive electrode of an electrochemical element so that the electric potential of 3 V or more, preferably 3.8 V or more may be applied with respect to the lithium precipitated battery. The amount of electricity is not particularly limited in the energization. However, the amount of electricity may be appropriately selected so that an electrolytic oxidation reaction of 100 coulombs or more per kg may occur with respect to the polyvinyl acetal resin.

When the nonaqueous electrolyte contains a compound that generates an acid, the electrochemical device may be heated in the initial filling step and the aging step. The heating of the electrochemical device promotes the generation of acid, and the crosslinking of the polyvinyl acetal resin proceeds more smoothly. Heating at this time is performed in the range which does not deteriorate an electrochemical element. As specific heating conditions, 0.5-30 days (preferably 1-7 days) at 45 degreeC, 1 hour-7 days (preferably 5 hours-3 days) at 60 degreeC are mentioned, for example.

In the electrochemical device, the crosslinked product of the polyvinyl acetal resin is insolubilized in the nonaqueous solvent by crosslinking, and exists in a state that can be separated from the nonaqueous solvent by simple separation means such as filtration or centrifugation. Or, it is insoluble in the nonaqueous solvent, but may be dispersed almost uniformly in the nonaqueous solvent and present by gelling the nonaqueous solvent. Whether or not the polyvinyl acetal resin is crosslinked in the electrochemical device can be confirmed secondarily from the improvement of the adhesive strength of the laminate composed of the negative electrode, the separator, and the positive electrode.

In order to improve the adhesive strength of the laminate, it is preferable that the crosslinked product of the polyvinyl acetal resin is selectively present at the interface between the negative electrode and the separator and at the interface between the positive electrode and the separator. When adopting such a structure, W1 (g) is the amount of the nonaqueous electrolyte solution containing the crosslinked product, and when the filtration amount after separation and removal of the crosslinked product is W2 (g), W2 is divided by W1. It is preferable that a rate value (W2 / W1 * 100) is 20% or more, It is more preferable that it is 40% or more, It is especially preferable that it is 60% or more. The upper limit of this percentage value is determined by the content of the acid-modified substance in the nonaqueous electrolyte. In order to have as many crosslinked products of the polyvinyl acetal resin as possible at the interface between the negative electrode and the separator and at the interface between the positive electrode and the separator, it is preferable to crosslink the polyvinyl acetal resin quickly after the electrolytic oxidation on the electrode surface. For example, after the electrochemical device is charged, the electrochemical device may be immediately heated at a temperature as high as possible in a range where the characteristics of the electrochemical device do not decrease. The temperature to heat is 40 degreeC-90 degreeC, It is preferable to set it as 50 degreeC-60 degreeC preferably. The heating time may be determined in consideration of the influence on the battery characteristics.

[Lithium battery]

One embodiment of the electrochemical device of the present invention includes a lithium battery. A lithium battery is a battery in which a nonaqueous electrolyte is injected into a laminate including a negative electrode, a positive electrode, and a separator, and the negative electrode and the separator, and / or the positive electrode and the separator are bonded by a crosslinked product of polyvinyl acetal resin. The nonaqueous electrolyte is characterized in that it contains a lithium salt as an electrolyte, and the negative electrode contains a negative electrode active material capable of occluding and / or releasing lithium metal or lithium.

The negative electrode is configured to include a negative electrode active material and a negative electrode current collector. As the negative electrode active material, a known compound capable of occluding and / or discharging lithium metal or lithium can be used. For example, silicon, a silicon alloy, tin, or a tin alloy capable of alloying with lithium, a lithium-containing alloy, or lithium can be used. And tin oxides that can occlude and release lithium, silicon oxide, transition metal oxides that can occlude and release lithium, transition metal nitrides that occlude and release lithium, and carbon materials that can occlude and release lithium. have. These negative electrode active materials can use 1 type (s) or 2 or more types. As a negative electrode current collector, what is commercially available in this field can be used, For example, copper, nickel, stainless steel, etc. are mentioned.

The negative electrode is uniformly mixed with a negative electrode active material and a binder such as polyvinylidene fluoride, carboxymethyl cellulose, latex, a crosslinkable polymer material and the like, and the mixture is applied onto a negative electrode current collector and dried, preferably It can prepare by performing the press for increasing the packing density of a negative electrode active material. Among the negative electrodes, as described above, after increasing the packing density of the negative electrode active material in the negative electrode active material layer, it is preferable to provide a coating layer containing polyvinyl acetal resin on the surface of the negative electrode active material layer.

The positive electrode includes a positive electrode active material and a positive electrode current collector. As the positive electrode active material, those commonly used in this field can be used. For example, transition metal oxides or transition metal sulfides such as FeS ₂ , MoS ₂ , TiS ₂ , MnO ₂ , V ₂ O ₅ , LiCoO ₂ , LiMnO ₂ , Composite oxides consisting of lithium and transition metals such as LiMn ₂ O ₄ , LiNiO ₂ , LiNi _x Co _(1-x) O ₂ , LiNi _x Co _y Mn _(1-xy) O ₂ , polyaniline, polythiophene, polypyrrole, Conductive polymer materials such as polyacetylene, polyacene, and dimercaptothiadiazole / polyaniline composite, and carbon materials such as fluorinated carbon and activated carbon. Among these, an active material capable of generating an electromotive force of 3 V or more, preferably 3.8 V or more with respect to the dissolution precipitation potential of lithium is preferable, and a composite oxide composed of lithium and a transition metal is particularly preferable. A positive electrode active material can be used individually by 1 type, or can use 2 or more types together. When the positive electrode active material exhibits an electromotive force of 3 V or more relative to the dissolution precipitation potential of lithium, the polyvinyl acetal resin is sufficiently subjected to electrolytic oxidation, and the crosslinking of the polyvinyl acetal resin easily proceeds. As the positive electrode current collector, one commonly used in this field can be used.

The positive electrode is a mixture of a positive electrode active material and a binder such as polyvinylidene fluoride, polytetrafluoroethylene, a crosslinkable polymer material, and the like, and the mixture is applied to the positive electrode current collector and dried, preferably It can produce by pressing in order to raise the packing density of a positive electrode active material. Along with the positive electrode active material, conductive aids such as carbon black, amorphous whiskers and graphite may be used.

As a separator, the same thing as the separator shown on the page of the electrochemical element of this invention can be used.

The nonaqueous electrolyte solution for lithium batteries contains lithium salt and polyvinyl acetal resin varnish as electrolytes.

As the lithium salt, those commonly used as electrolytes for lithium batteries can be used. For example, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , Li ₂ SiF ₆ , LiOSO ₂ C _k F _{(2k + 1)} (k = Integer from 1 to 8), LiPF _n (C _k F _{(2k + 1)} ) _(6-n) (n = 1 to 5, integer from k = 1 to 8), LiC (SO ₂ R ⁵ ) (SO ₂ R ⁶ ) (SO ₂ R ⁷ ), LiN (SO ₂ OR ⁸ ) (SO ₂ OR ⁹ ), LiN (SO ₂ R ¹⁰ ) (SO ₂ R ¹¹ ) (R ⁷ ~ R ¹³ is the same or different carbon number 1 ~ Lithium salts, such as the perfluoroalkyl group of 8), etc. are mentioned. Among these, LiPF ₆ , LiBF ₄ , LiN (SO ₂ R ¹⁰ ) (SO ₂ R ¹¹ ) (R ¹⁰ And R ¹¹ are the same as described above, and LiPF ₆ , LiBF ₄ and the like are particularly preferable. These lithium salts can use 1 type (s) or 2 or more types. The content of the lithium salt in the nonaqueous electrolyte is 0.1 to 3 mol / liter, preferably 0.5 to 2 mol / liter.

Polyvinyl acetal resin varnish dissolves polyvinyl acetal resin in the carbonate ester solvent. The carbonate ester solvent is most suitable for the solvent of the electrolyte solution for lithium secondary batteries from electrochemical safety (oxidation reduction stability) and chemical safety, and is used as a main solvent.

Carbonic acid ester used for a non-aqueous electrolyte includes cyclic carbonate ester and chain carbonate ester. As cyclic carbonate, cyclic carbonates, such as ethylene carbonate, a propylene carbonate, butylene carbonate, a fluoroethylene carbonate, a trifluoroethylene carbonate, are mentioned, for example. Examples of the chain carbonate include chain forms such as dimethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl trifluoroethyl carbonate, ditrifluoroethyl carbonate, diethyl carbonate, dibutyl carbonate and methyl octyl carbonate. Carbonates. As a solvent for a lithium battery, in addition to carbonate ester, carbonate ester is also suitable and can be contained in electrolyte solution. Examples of the carboxylic acid esters include cyclic carboxylic acid esters such as γ-butyrolactone, and chain carboxylic acid esters such as methyl acetate, methyl propionate, pentafluoropropyl acetate, and methyl trifluoroacetate. Although 1 type (s) or 2 or more types can be used for the carbonate ester illustrated above, in consideration of improving the load characteristic, low temperature characteristic, etc. of the battery obtained, it is preferable to use together a cyclic carbonate ester and a chain carbonate ester. The mixing ratio (cyclic carbonate: chain carbonate) of the cyclic carbonate and the chain carbonate is in a weight ratio of 5:95 to 80:20, preferably 10:90 to 70:30, and more preferably 15:85 55:45. By setting it as such a ratio, since the dissociation degree of electrolyte can be improved, suppressing the viscosity rise of a nonaqueous electrolyte solution, the conductivity of the nonaqueous electrolyte solution regarding the charge / discharge characteristic of a battery can be raised, and the solubility of a nonaqueous electrolyte is kept high. Can be. As a result, the non-aqueous electrolyte having excellent electrical conductivity at room temperature or low temperature can be used, so that the charge / discharge load characteristics of the battery from room temperature to low temperature can be improved. In addition, in consideration of adjusting the solvent composition to increase the flash point of the solvent and improving the safety of the battery, it is preferable to use cyclic ester alone or to make the mixed amount of the chain ester be 20% by weight or less of the total amount of the nonaqueous solvent. As cyclic ester in this case, ethylene carbonate, propylene carbonate, (gamma) -butyrolactone, 2 or more types of these mixtures, etc. are preferable. As the chain ester, chain carbonate is preferable.

Moreover, you may use together cyclic carbonate which has a vinyl group together with ester mentioned above. As a result, the reduction decomposition reaction of the nonaqueous electrolyte on the negative electrode is suppressed, and the high temperature storage characteristics, cycle charge and discharge characteristics, and the like of the battery are further improved. As the cyclic carbonates having a vinyl group, known ones can be used. For example, vinylene carbonate, methylvinylene carbonate, ethylvinylene carbonate, propylvinylene carbonate, phenylvinylene carbonate, dimethylvinylene carbonate, diethyl vinyl Ethylene carbonate, dipropyl vinylene carbonate, diphenyl vinylene carbonate, vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate and the like. Among these, vinyl ethylene carbonate, divinyl ethylene carbonate, vinylene carbonate and the like are preferable, and vinylene carbonate is particularly preferable. The cyclic carbonates having a vinyl group can be used alone or in combination of two or more. As a combination in the case of using 2 or more types together, vinylene carbonate, vinyl ethylene carbonate, vinylene carbonate, divinyl ethylene carbonate, etc. are preferable. Content of cyclic carbonate which has a vinyl group is 0.1-10 weight% of the nonaqueous electrolyte whole quantity, Preferably it is 0.5-5 weight%.

The nonaqueous electrolyte solution for lithium batteries may contain solvents, additives, and the like other than those described above in a range that does not impair the characteristics thereof. For example, ethers, amides, carbamates, urea, phosphate esters, aromatic hydrocarbons, fluorinated ethers, etc. are mentioned.

The lithium battery of the present invention can be produced according to the above-described method using the nonaqueous electrolyte of the present invention containing lithium salt as the above-described negative electrode, separator, positive electrode, and electrolyte for a lithium battery.

As the non-aqueous electrolyte used herein, to the polyvinyl acetal resin varnish, Lewis acid and / or Lewis acid salt having a halogen atom which is a compound which generates an acid by reaction with lithium salt (electrolyte) and water is added. desirable. As a lithium salt, the thing similar to what is used by the nonaqueous electrolyte solution for lithium batteries can be used with the same content. The above-mentioned thing can also be used as a polyvinyl acetal resin varnish, and the acid-modified varnish of polyvinyl formal resin is especially preferable. The content in the nonaqueous electrolyte of the polyvinyl acetal resin is 3.5% by weight or less, preferably 0.3 to 3.5% by weight, more preferably 0.5 to 2.5% by weight of the total amount of the nonaqueous electrolyte. By setting it as content of this range, the influence on a charge / discharge load characteristic can be minimized, and the lithium battery excellent in shape retention can be obtained.

The above-mentioned thing can also be used also as a Lewis acid or a Lewis acid salt which has a halogen atom, and it is preferable that a halogen atom is a fluorine atom especially. For example, LiPF ₆ and LiBF ₄ which also have a function as an electrolyte salt are preferable. Moreover, in order to raise the crosslinking speed in a nonaqueous electrolyte, Lewis acid and Lewis acid salt with a large acid generation rate are preferable. Among them, SiF _n R _(4-n) (n = 1 to 4, R represents an organic group) is more preferable in consideration of ease of handling, easy availability of high-purity products, stability in electrolyte solution, acid generation rate, and the like. . As specific examples of SiF _n R _(4-n) , for example, trimethylsilyl fluoride, triphenylsilyl fluoride, dimethylsilyl difluoride, diphenylsilyl difluoride, methylsilyl trifluoride, phenylsilyl trifluor Ride etc. are mentioned, and trimethylsilyl fluoride is especially preferable. In addition, when using SiF _n R _(4-n) , SiF _n R _(4-n) is added directly to the non _- aqueous electrolyte, or a compound which changes in the non-aqueous electrolyte to produce SiF _n R _(4-n) is added. Do it. As the change from the non-aqueous electrolyte compounds as _{SiF n R (4-n)} , but may include various silyl esters, among others, the silyl phosphate esters are preferred. Phosphoryl silyl ester not only produces SiF _n R _(4-n) , but also acts as a dehydrating agent and has a characteristic of gelling a liquid containing polyvinyl acetal resin varnish. In the nonaqueous electrolyte of the portion protruding from the electrode laminate in the battery, since no current flow occurs, crosslinking of the acid-modified product is unlikely to occur. However, when the phosphate silyl ester is added to the nonaqueous electrolyte, the nonaqueous electrolyte gels well and the liquid leakage prevention effect is achieved. Becomes higher. The Lewis acid or Lewis acid salt containing a halogen atom can be used individually by 1 type, or can use 2 or more types together. The content of Lewis acid or Lewis acid salt having a halogen atom is 0.01 to 10% by weight, preferably 0.05 to 2% by weight of the total amount of the nonaqueous electrolyte.

The lithium battery of this invention can be made into arbitrary shapes, for example, is formed in cylindrical shape, coin shape, square shape, film shape, etc. However, the basic structure of the battery is the same regardless of the shape, and the design can be changed according to the purpose.

The lithium battery of this invention can be used for the same use as the conventional lithium battery. For example, various types of consumer electronic devices include, among others, cell phones, mobile phones, laptop personal computers, cameras, portable video recorders, portable CD players, portable MD players, and the like.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited thereto. In the following, "%" and "part" shall represent "weight%" and "weight part", unless there is particular limitation. In addition, "V / V" shows a volume ratio.

Synthesis Example 1 Synthesis Example of Polyvinyl Acetal Resin

Alkali saponification of polyvinyl acetate was carried out, and the polyvinyl alcohol resin (soap-degree 89%, average degree of polymerization 800) which the one part acetate-esterified was obtained. After mixing 25 g of this polyvinyl alcohol, 200 ml of 50% acetic acid aqueous solution and 40 ml of 10% hydrochloric acid, 100 ml of formalin (37% aqueous formaldehyde solution) was added and reacted at 30 ° C for 5 hours. After the reaction was completed, dilute acetic acid was added to the reaction solution to precipitate the reaction product. The precipitate was filtered off, neutralized with sodium hydroxide, washed with water and dried to obtain polyvinyl formal. The composition was analyzed on the basis of JIS K6729 "Polyvinyl Formal Test Method" and the composition ratio was 82.5% for vinyl formal units (R ₁ = hydrogen atom in General Formula (1)) and vinyl alcohol unit (2). It was confirmed that it is a polyvinyl formal resin which consists of 5.9% and a vinyl acetate unit (R <_2> = methyl group in General formula (3)) 11.6%. In the said polyvinyl formal resin, the hydroxyl group concentration converted from the composition ratio of the vinyl alcohol unit (2) was 1.34 mol / kg.

In the same manner, polyvinyl formal resins having various molecular weights were obtained by using polyvinyl alcohol resins having various molecular weights instead of polyvinyl alcohol resins having an average degree of polymerization of 800. Each chemical composition was almost the same as the above-mentioned polyvinyl formal resin.

In the same manner, polyvinylacetacetal resin, polyvinylpropyral resin or polyvinyl butyral resin was obtained by using acetaldehyde, propionaldehyde or butylaldehyde instead of formalin. These chemical compositions were 72 weight% of vinyl acetal parts, 16 weight% of vinyl acetate parts, and 12 weight% of vinyl alcohol parts.

Synthesis Example 2 Acid Modification Example of Polyvinyl Acetal Resin

Polyvinyl formal resin (average degree of polymerization 800) obtained in the same manner as in Synthesis example 1 was dissolved in 100 ml of a 2: 1 (volume ratio) mixed solvent of ethylene carbonate and ethyl methyl carbonate at a concentration of 5%, 0.01% sulfuric acid was added, It heated at 45 degreeC for 144 hours (acid-modification treatment), and obtained the solution containing the acid-modified substance of polyvinyl formal resin.

The polyvinyl acetal resin was acid-modified because the proton appears at 4.28 ppm by NMR spectrometer (trade name: JNM-A500 (500 MHz), manufactured by Nippon Electronics Co., Ltd.) before and after acid-modification treatment of polyvinyl formal resin. It confirmed by the change of concentration. In the measurement, DMSO-d ₆ was used as the solvent, DMSO-d ₆ was used as the shift reference (2.49 ppm), and tetrachloroethane was used as the internal standard. The proton concentration at 4.28 ppm was 0.3 mol before the acid modification treatment per kg of polyvinyl formal resin, but was 0.1 mol after the acid modification treatment. It was confirmed that the polyvinyl formal resin was acid-modified by lowering the concentration of protons.

Test Example 1 [Relationship between Solvent Composition and Solubility of Polyvinyl Acetal Resin]

The polyvinyl formal resin obtained by the synthesis example 1 was dried at 80 degreeC under reduced pressure, and the polyvinyl formal resin of 200 ppm of moisture content was produced. As the non-aqueous solvent, EC (ethylene carbonate) or PC (propylene carbonate) was used as the cyclic carbonate, and DMC (dimethyl carbonate), EMC (ethyl methyl carbonate), and DEC (diethyl carbonate) were used as the chain carbonate. The nonaqueous solvent was dried in a molecular sieve, respectively, and the content of water contained was adjusted to 20 ppm or less. The ratio of polyvinyl formal resin and the non-aqueous solvent obtained above was changed and mixed suitably, it stirred at 45 degreeC for 10 hours, and the polyvinyl formal resin varnish was obtained. The solubility and varnish viscosity of the obtained varnish were measured. As a reference example, instead of polyvinyl formal resin, varnish using the polyvinyl propyral, the polyvinyl acetoacetal, and the polyvinyl butyral which were obtained by the synthesis example was created, respectively. The results are shown in Table 1. In the item of the polyacetal resin species in the table, "H" is polyvinyl formal, "P" is polyvinyl propyral, "A" is polyvinyl acetoacetal and "B" is polyvinyl butyral, respectively.

In addition, the evaluation criteria of solubility are (circle); solubility, (triangle | delta); some insoluble, x; insoluble.

* 1 Insoluble matter that does not dissolve.

* 2 Once dissolved, polyvinyl formal resin precipitates when cooled to room temperature.

* 3 No measurement.

From Table 1, it turns out that solubility improves significantly in the mixed solvent of cyclic carbonate and chain carbonate ester. Moreover, it turns out that the solubility of polyvinyl formal resin is excellent in polyvinyl acetal resin.

Test Example 2 [Measurement of Flash Point of Nice]

The polyvinyl formal resin (average degree of polymerization 800) obtained by the synthesis example 1 was melt | dissolved in various nonaqueous solvents, and the polyvinyl formal resin varnish of the density | concentration of 5 weight% was prepared. Flash points of these varnishes were measured by tack closure and summarized in Table 2.

From Table 2, it can be seen that the varnish of the present invention has low flammability, significantly less risk of fire, and high safety.

Test Example 3 [Gelation Test of Non-Aqueous Electrolyte]

The varnish consisting of the polyvinyl formal resin obtained in the synthesis example 1 or the acid denaturation of the polyvinyl formal resin obtained in the synthesis example 2 was mixed with the nonaqueous electrolyte solvent, the dehydrating agent was further mixed, and the nonaqueous electrolyte was prepared.

The varnish was mixed with a non-aqueous solvent such that the concentration of the polyvinyl formal resin or its acid modified substance was 10%, and varnishes of the following A to C were obtained. The varnish A (product of this invention) melt | dissolved the polyvinyl formal resin of the synthesis example 1 in 1: 1 (volume ratio) mixed solvent of EC and MEC. Varnish B (product of this invention) melt | dissolved the acid modified substance of the polyvinyl formal resin of the synthesis example 2 in 1: 1 (volume ratio) mixed solvent of EC and EMC. Varnish C (Comparative Product) dissolved the polyvinyl formal resin of Synthesis Example 1 in a 1: 1 (volume ratio) mixed solvent of toluene and butanol.

As the nonaqueous electrolyte solvent, two types of electric double layer capacitors (hereinafter referred to as "capacitors") and lithium batteries (hereinafter referred to as "lithium batteries") were used.

As the nonaqueous electrolyte solvent for the capacitor, propylene carbonate containing tetrabutylammonium tetrafluoroborate in a ratio of 1 mol / liter was used. As a nonaqueous electrolyte solvent for lithium batteries, a mixed solvent (1: 1 volume ratio) of EC and EMC containing lithium hexafluorophosphate at a ratio of 1 mol / liter was used. The water content of the two kinds of nonaqueous electrolyte solvents was adjusted to 10 ppm or less.

After mixing a nonaqueous electrolyte solvent and varnish in the ratio of 4: 1 (weight ratio), 0.5 weight% of dehydrating agents were added, it was left to stand at room temperature, and the appearance of gelation was observed every 15 minutes. Tributyl borate or tristrimethylsilyl phosphate was used as a dehydrating agent. The results are shown in Table 3.

It can be seen from Table 3 that the varnish of the present invention exhibits the action of gelling the nonaqueous electrolyte solvent by being used in combination with a dehydrating agent, and it is found that the varnish of the present invention is useful for preventing leakage of an electric double layer capacitor or a lithium battery. Moreover, in order to exhibit this effect, it turns out that it is preferable to reduce the moisture content in a varnish.

Synthesis Example 3

Polyvinyl formal with different content ratios of vinyl formal units (R = hydrogen atoms in formula (1)), vinyl alcohol units (2) and vinyl acetate units (R ₂ = methyl groups in formula (3)) Except using resin, it carried out similarly to the synthesis example 2, and obtained the solution containing the acid modified substance of polyvinyl formal resin. The obtained acid modified substance had physical properties shown in Table 4. In addition, in the three kinds of acid-modified products obtained by removing polyvinyl formal having a hydroxyl group content of 2.8 mol / kg, all concentrations of protons at 4.28 ppm were reduced to 70% or less by acid treatment. there was.

(Example 9 and Reference Example 3)

Varnish, ethylene carbonate, and ethyl methyl carbonate containing acid-modified products of polyvinyl formal resin obtained in Synthesis Example 2 and Synthesis Example 3 were mixed to obtain a nonaqueous electrolyte. The non-aqueous electrolyte was prepared at a concentration (c,%) in which the weight ratio of ethylene carbonate and ethyl methyl carbonate was 2: 3, LiPF ₆ was 1 mol / liter, and the acid-modified product of the polyvinyl formal resin is shown in Table 4. did. T1-T10 are nonaqueous electrolytes (Example 9) of this invention, and R1-R4 are nonaqueous electrolytes of a reference example.

In addition, acid modified products of nonaqueous electrolytes T1 to T6 and R1 to R2 were obtained in Synthesis Example 2, and acid modified products of T7 to T10 and R3 to R4 were obtained in Synthesis Example 3.

※ 4 There are many insoluble materials, and output is impossible

Of the non-aqueous electrolyte as shown in Table 4 R ₄ is not a non-aqueous acid-modified water homogeneously dissolved in the solvent left a large amount of the insoluble lysate. From this, it turns out that it is not suitable as an additive to a nonaqueous electrolyte solution when the hydroxyl group content in polyvinyl formal resin exceeds 2 mol / liter. In the other nonaqueous electrolyte, acid-modified substance was dissolved in the nonaqueous solvent.

(Test Example 4)

In the same composition as the non-aqueous electrolyte of T3, a non-aqueous electrolyte using polyvinyl acetal resin, polyvinylpropyral resin or polyvinyl butyral resin was prepared in place of the polyvinyl formal resin. The solubility of each resin in the nonaqueous solvent and the safety when the nonaqueous electrolyte was stored at 25 ° C. were visually observed. The results are shown in Table 6.

Non-aqueous electrolyte Solubility of Resin Storage stability of nonaqueous electrolyte T3 Evenly dissolve Stay liquid for more than 30 days Contains polyvinyl acetal resin Some insolubles Keep liquid for 3 days Contains polyvinylpropyral resin Some insolubles Keep liquid for 7 days Contains polyvinyl butyral resin Some insolubles Keep liquid for 7 days

From Table 5, the non-aqueous electrolyte (T3) using the polyvinyl formal resin can be uniformly dissolved in the electrolytic solution, and even if stored for 30 days or more, the non-aqueous electrolyte of the present invention is maintained in a liquid state free from insoluble matter and precipitates. I know it's best to use. It is evident that the nonaqueous electrolyte solution using another polyvinyl acetal liquid resin needs to be insoluble in some cases, and furthermore, it is better to inject the nonaqueous electrolyte into the electrochemical device immediately after preparation of the nonaqueous electrolyte solution, without preserving it for a long time.

(Examples 10-19 and Reference Examples 4-8)

1) Fabrication of Cathode

74 parts of mesocarbon microbeads (brand name: MCMB10-28, product made by Osaka Gas), 20 parts of natural graphite (brand name: LF18A, manufactured by Nakagoshi Graphite Co., Ltd.) and 6 parts of polyvinylidene fluoride (PVDF, binder) The mixture was dispersed and dispersed in 100 parts of N-methylpyrrolidinone to prepare a negative electrode mixture slurry. This negative electrode mixture slurry was applied to a negative electrode current collector of a strip-shaped copper foil having a thickness of 18 μm and dried. This was pressed at a pressure of about 29.42 × 10 ⁶ Pa (300 kg / cm 2) to form a negative electrode. The porosity of the negative electrode active material in this negative electrode was 0.3.

2) fabrication of anode

82 parts of LiCoO ₂ (brand name: HLC-22, manufactured by Honjo FMc Energy Systems Co., Ltd.), 7 parts of graphite (conductive agent), 3 parts of acetylene black (conductive agent) and 8 parts of polyvinylidene fluoride (PVDF, binder) mixed, N- methylpyrrolidone were dispersed in 80 parts, to prepare a LiCoO ₂ mixture slurry. This LiCoO ₂ mixture slurry was applied and dried on an aluminum foil (anode current collector) having a thickness of 20 μm. This was pressed at a pressure of about 9.8 × 10 ⁷ Pa (1000 kg / cm 2) to form a positive electrode. The porosity of the positive electrode active material in this positive electrode was 0.25.

3) Production of coin type battery

As a negative electrode, the negative electrode obtained in said 1) was penetrated into the circular shape of 14 mm in diameter, and was used. This negative electrode had a thickness of the negative electrode mixture of 80 μm and a weight of 20 mg / 14 mmφ.

As the positive electrode, the positive electrode obtained in the above 2) was used through a circular shape having a diameter of 13.5 mm. The LiCoO ₂ electrode had a thickness of 70 μm and a weight of 42 mg / 13.5 mmφ in the LiCoO ₂ mixture.

A negative electrode (diameter of 14 mm) is disposed on the negative electrode tube surface in a stainless steel battery tube of size 2032, and a separator (25 μm thick, 16 mm diameter) and a positive electrode (diameter) made of a microporous polypropylene film are further disposed. 13.5 mm) were laminated one by one. Thereafter, between the separator and the negative electrode and the separator and the positive electrode, 0.25 ml of the ten kinds of the present invention nonaqueous electrolytes (T1 to T10) of Example 9 or four kinds of the nonaqueous electrolytes (R1 to R4) of Reference Example 3 were injected and An aluminum plate (thickness 1.2 mm, diameter 16 mm) and a spring were accommodated. Finally, a gas-tight lid in the battery was maintained by passing through a polypropylene gasket to manufacture a coin-type lithium ion secondary battery having a diameter of 20 mm and a height of 3.2 mm.

4) Fabrication of cylindrical secondary battery

First, a negative electrode was produced as follows. 70 parts of mesocarbon microbeads (brand name: MCMB10-28, product made by Osaka Gas Co., Ltd.), 20 parts of natural graphite (brand name: LF18A, manufactured by Nakagoshi Graphite Co., Ltd.), and 10 parts of polyvinylidene fluoride as a binder The negative electrode mixture was prepared, and this was further dispersed in N-methyl-2-pyrrolidone to obtain a slurry. And this slurry was apply | coated uniformly to both surfaces of the 10-micrometer-thick strip | belt-shaped copper foil which is a negative electrode electrical power collector, and was compression-molded by the roll press after drying, and the negative electrode was produced.

Next, the positive electrode was produced as follows. A positive electrode mixture was prepared by mixing 91 parts of LiCoO ₂ (trade name: HLC-22, manufactured by Honjo FMC Energy Systems Co., Ltd.), 6 parts of graphite as a conductive agent, and 3 parts of polyvinylidene fluoride as a binder. Furthermore, this was dispersed in N-methyl-2-pyrrolidone to make a slurry. And this slurry was apply | coated uniformly to both surfaces of the aluminum foil with a thickness of 20 micrometers which is a positive electrode electrical power collector, and was compression-molded by the roll press after drying, and the positive electrode was produced.

Next, a wound body was produced by passing a separator made of a microporous polypropylene film having a thickness of 20 µm, laminating the negative electrode and the positive electrode in sequence, and winding the wafer multiple times in a spiral winding. The insulation board was inserted in the bottom part of the iron battery tube which nickel-plated this, and the wound body was accommodated. Then, in order to take the current collector of the negative electrode, one end of the negative electrode lead made of nickel was pressed on the negative electrode, and the other end was welded to the battery tube. In order to collect the positive electrode, one end of an aluminum positive electrode lead was provided at the positive electrode, and the other end was electrically connected to the battery lid through a current blocking thin plate which cuts off the current in accordance with the battery breakdown voltage.

Next, five non-aqueous electrolyte solutions of the present invention (T1, T2, T3, T5, T6) in Example 9 and 4 ml of the nonaqueous electrolyte solutions (R1, R2) in Reference Example 3 were respectively injected into the cell tube, The operation to pressurize the inside of the battery tube and return to normal pressure was repeated, and the electrolyte solution was injected into the battery tube. Finally, the battery lid was fixed by winding the battery tube through an insulating rod gasket coated with asphalt to produce a cylindrical nonaqueous electrolyte battery having a diameter of 18 mm and a height of 65 mm.

5) Crosslinking by filling

2 mA for the coin-type lithium ion secondary batteries of Examples 10 to 19 obtained in 3) above, and 4.2 V at a current of 0.2 A for the cylindrical lithium ion secondary batteries of Examples 11-20 obtained in 4) above. The acid-modified product of the polyvinyl formal resin contained in the nonaqueous electrolyte was crosslinked to prepare a coin type and cylindrical lithium ion secondary battery of the present invention.

(Test Example 5)

A coin-type lithium secondary battery using T5 of Example 9 was prepared as a nonaqueous electrolyte. After charging this to 0.5V, 3.8V, or 4.0V by the electric current of 2mA, it was left to stand at room temperature (25 degreeC) or 50 degreeC for 24 hours. This left to stand for 24 hours corresponds to the aging step in the general production method of electrochemical devices. Then, this coin-type lithium secondary battery was disassembled and the adhesiveness of an electrode and a separator was investigated. The results are shown in Table 6.

Moreover, the coin-type lithium secondary battery left unattended at room temperature (25 degreeC) or 50 degreeC for 24 hours was examined similarly, the adhesiveness of an electrode and a separator was investigated. The results are shown in Table 6.

No. Charging voltage Neglect temperature Presence or absence of adhesion One Do not charge 25 ℃ Not glued 2 Do not charge 50 ℃ Not glued 3 0.5 V 25 ℃ Not glued 4 0.5 V 50 ℃ Not glued 5 3.8V 25 ℃ adhesion 6 3.8V 50 ℃ Strongly adhesive 7 4.0V 25 ℃ Strongly adhesive 8 4.0V 50 ℃ Strongly adhesive

From Table 6, by charging to 3.8V or 4.0V, it is clear that the acid modified substance of the polyvinyl acetal resin contained in the non-aqueous electrolyte of T5 crosslinks, and the electrode (cathode and anode) and a separator adhere. Moreover, when charging to 3.8-4.0V and then aging at 50 degreeC, it is also clear that adhesive strength becomes higher. On the other hand, in charging or not charging to 0.5V, even if it warms in an aging process, crosslinking of an acid modified substance does not occur and it turns out that an electrode and a separator do not adhere completely.

In addition, it is estimated that the instrumental difference between the acid modified product of the polyvinyl formal resin and the crosslinked product of the acid modified product is evident in both ¹³ C-solid NMR spectrums. Specifically, it carried out as follows. The battery was disassembled, and the gel material present in the separator or at the interface between the separator and the electrode was collected. The gel material was placed in a commercially available Teflon (registered trademark) sealed cell, and the sealed cell was inserted into a 7.5 mm sample tube. The sample tube was spun at 2000 Hz and subjected to ¹³ C-solid NMR measurement. The measurement apparatus used the CMX300 7.5 mm probe manufactured by Chemagnetics. The measurement conditions were performed by the single-pulse method at the resonance frequency of 75.5578 MHz, the pulse was a 30-degree pulse of 1.7 µs and the bandwidth was 30 kHz.

In the ¹³ C-solid NMR spectrum measured by the above method, the signal of the crosslinked product was reduced in the vicinity of 70 ppm, and the signal which was not present in the acid denatured substance was observed in the vicinity of 90 to 110 ppm, compared to the acid modified product. The signal near 70 ppm is assumed to be a signal of carbon bonded to a hydroxyl group, and the signal near 90 to 110 ppm is assumed to be a signal of carbon bonded to two oxygens of an acetal ring. Therefore, the signal around 70ppm decreases and the signal which does not exist in the original acidic modified product about 90-110ppm is observed that the hydroxyl group in the acidic modified product of the polyvinyl formal resin produced at the terminal of the polymer chain was observed. It can be assumed that it forms a new acetal ring and reacts with, indicating that the polymer chain is crosslinked.

(Test Example 6)

Cylindrical and coin-type lithium ion secondary batteries were prepared using electrolyte solutions T1 to T3, T5, T6, R1, and R2, respectively. The possible pouring amount (g) of the nonaqueous electrolyte to the cylindrical battery was investigated.

In addition, the impedance of 10 kHz was measured about the coin type and cylindrical battery, and the impedance change rate was investigated according to the following formula. The results are shown in Table 7.

Impedance Rate = X / Y

X: impedance of each battery

Y: Impedance of the battery in which the nonaqueous electrolyte solution of Example 10 was injected

From Table 7, in Example, it turns out that the liquid injection amount of a nonaqueous electrolyte solution falls in the reference example, while the liquid-liquid fall of the nonaqueous electrolyte solution to a battery hardly falls.

In addition, from Table 8, in the example, the change rate of the impedance of 10 kHz was hardly increased in the reference example. The impedance of 10 kHz corresponds to the electrical resistance derived from the nonaqueous electrolyte in the battery, and a large impedance indicates that the injection of the nonaqueous electrolyte into the battery is insufficient, or the penetration of the electrolyte into the pores in the active material or between the active materials is insufficient. . Therefore, the non-aqueous electrolyte having lambda ^{1 /} 2xc of 1000 or more has poor liquid injection property of the non-aqueous electrolyte solution to the battery, and particularly, in the cylindrical battery in which the electrode active material or the like is highly charged, the drop in the liquid injection property was remarkable.

(Test Example 7)

Coin-type lithium ion secondary batteries were created using electrolyte solutions T1-T10 and R1-R4, respectively. They were charged to 4.2V and discharged to 3.0V at a current of 0.5mA. The discharge capacity at this time was made into "initial discharge capacity." The battery was charged to 4.0V and left for 24 hours. About this battery, the adhesive evaluation shown below, initial charge / discharge characteristic evaluation, and battery characteristic evaluation after high temperature storage were performed. The results are shown in Table 8.

[Adhesive Evaluation]

These batteries were dismantled, peeled off with an electrode and a separator, and the adhesiveness was investigated and evaluated according to the following criteria.

(Double-circle): The active material layer of a electrode and a separator were firmly in contact with each other, and even if peeling operation was carried out, it peeled from the interface of an electrical power collector and an active material layer, and the separator remained as it was attached to the active material layer of an electrode.

(Circle): Although the active material layer and separator of an electrode were fully in contact, when peeling operation, the electrode peeled from the interface of the active material layer and a separator.

(Triangle | delta): Although the active material layer of a electrode and a separator were in close_contact | adherence, when peeling operation was carried out, an electrode peeled easily from the interface of the active material layer and a separator.

[Initial charge / discharge characteristic evaluation]

After charging the battery to 4.2V, it discharged to 3.0V by the electric current of 10mA, and calculated | required "discharge capacity at 10mA." Subsequently, after charging to 4.2V, it discharged to 3.0V by the electric current of 5mA, and calculated | required "discharge capacity at 5mA." Let percentage of "discharge capacity at 10mA" with respect to "first discharge capacity" be made into "high load index", and percentage of "discharge capacity at 5mA" with respect to "first discharge capacity" be made into "heavy load index" Evaluated and compared.

[Evaluation of Battery Characteristics after High Temperature Storage]

After charging these batteries to 4.2V, after storing them for 3 days at 85 degreeC, the "high load index" and the "heavy load index" were calculated | required again.

As mentioned above, in the battery of Examples 10-19 using the nonaqueous electrolyte whose (lambda) ^{1 /} 2xc is 100-1000, an electrode and a separator adhere | attach, and it is excellent also in a battery characteristic.

On the other hand, although the electrode and the separator adhere to the battery of the reference examples 4-6 which used the electrolyte solution whose (lambda) ^{1 /} 2xc is larger than 1000, battery characteristics are falling. Although λ ^1/2 × c is from 100 to 1000, in Reference Example 7 using an electrolyte solution in which the concentration of the hydroxyl group in the acid-modified product of the polyvinyl formal resin is 2.0 mol / kg or more, the electrode and the separator are adhered. Battery characteristics are deteriorating.

(Examples 20-29 and Comparative Example 3)

1) Preparation of Non-Aqueous Electrolyte (Examples 21 to 30)

EC and MEC were mixed in a ratio of 2: 3 (weight ratio), and LiPF ₆ (electrolyte) and vinylene carbonate were dissolved in this mixed solvent. The varnish which melt | dissolved the polyvinyl formal resin in the mixed solvent of EC: MEC = 2: 3 (weight ratio) was added to this electrolyte solution, and it melt | dissolved. Thereafter, tristrimethylsilyl phosphate was added to prepare a nonaqueous electrolyte solution of the present invention, which is shown in Table 9.

The content of LiPF ₆ is 1 mol / liter and the content of vinylene carbonate is 1%. Content of polyvinyl formal resin and tristrimethylsilyl phosphate is as Table 10 showing. In addition, the nonaqueous electrolyte contained 0.01% of hydrofluoric acid produced by reacting LiPF ₆ and water in the electrolyte.

Tristrimethylsilyl phosphate is used as a compound for producing trimethylsilyl fluoride in a nonaqueous electrolyte, and trimethylsilyl fluoride is Lewis acid having a high acid generating rate.

2) Preparation of nonaqueous electrolyte (comparative example 3)

EC and MEC are mixed in a ratio of 2: 3 (weight ratio), and in this mixed solvent, LiPF ₆ (electrolyte), vinylene carbonate, trimetholpropane ethoxylate acrylate (EO / OH = 14/3, Aldrich Co., Ltd.) and a radical polymerization initiator (brand name: Pabutyl (trademark) PV, Nippon Oil Holding Co., Ltd. product) were added and dissolved sequentially, and the nonaqueous electrolyte solution of the comparative example was prepared.

The content of LiPF ₆ and vinylene carbonate is 1 mol / liter, and the content of vinylene carbonate is 1%. The content of trimetholpropane ethoxylate acrylate is 5%. The radical polymerization initiator was added 3000 ppm. Here, trimethylolpropane ethoxylate acrylate is a macromonomer for a gel polymer electrolyte. A radical polymerization initiator is an additive for gelatinizing the said macromonomer.

3) Fabrication of Cathode

A negative electrode was produced in the same manner as in the above (Examples 10 to 20 and Reference Examples 4 to 8).

4) Fabrication of Anode

A positive electrode was produced in the same manner as in the above (Examples 10 to 20 and Reference Examples 4 to 8).

<Production of coin type battery>

As a negative electrode, the above-mentioned negative electrode was used through the disk shape of diameter 14mm. This coin-like negative electrode had a thickness of the negative electrode mixture of 80 μm and a weight of 20 mg / 14 mmφ.

As an anode, the above-mentioned anode was used through the disk shape of diameter 13.5mm. This coin-shaped LiCoO ₂ electrode had a thickness of 70 µm and a weight of 42 mg / 13.5 mm phi of the LiCoO ₂ mixture.

In a 2032 stainless battery tube, a negative electrode having a diameter of 14 mm, a diameter of 16 mm, a separator made of a microporous polypropylene film having a thickness of 25 μm, and a positive electrode having a diameter of 13.5 mm were stacked in this order. Thereafter, 0.04 ml of the nonaqueous electrolyte solution obtained above was injected into the separator, and an aluminum plate (thickness 1.2 mm, diameter 16 mm) and a spring were accommodated. Finally, by tightly adhering the lid of the battery tube via a polypropylene gasket, the airtightness in the battery is maintained, and the coin-type lithium batteries of Examples 20 to 29 and Comparative Example 3, each having a diameter of 20 mm and a height of 3.2 mm, are provided. Made. In the coin-type lithium battery of Comparative Example 3, the nonaqueous electrolyte was gelated by further heating at 60 ° C. for 5 hours to produce a gel polymer electrolyte.

(Example 31)

1) Fabrication of Cathode

A negative electrode was produced in the same manner as in Example 20. On the surface of the negative electrode active material layer of the negative electrode, a 4% propylene carbonate solution of polyvinyl formal resin was applied at a rate of 5 mg per 1 cm 2 (15 mg per 1 g of graphite) and dried to form a polyvinyl formal film.

2) fabrication of anode

In the same manner as in Example 20, a positive electrode was produced. On the surface of the positive electrode active material layer of the positive electrode, a 4% propylene carbonate solution of polyvinyl formal resin was applied at a rate of 5 mg per 1 cm 2 (15 mg per 1 g of graphite) and dried to form a polyvinyl formal film.

3) Preparation of separator

On the surface of the separator which is a microporous polypropylene film, the 2% propylene carbonate solution of polyvinyl formal resin was apply | coated in the ratio of 2 mg per cm <2>, and it dried, and the polyvinyl formal film was formed.

4) Production of coin type battery

As a negative electrode, the negative electrode in which the polyvinyl formal resin film mentioned above was formed was used through the disk shape of diameter 14mm. This coin-like negative electrode had a thickness of the negative electrode mixture of 80 μm and a weight of about 20 mg / 14 mmφ.

As a positive electrode, the positive electrode in which the polyvinyl formal resin film mentioned above was formed was used through the disk shape of diameter 13.5mm. The coin-shaped LiCoO ₂ electrode had a thickness of 70 μm and a weight of about 42 mg / 13.5 mmφ in the LiCoO ₂ mixture.

As a separator, the microporous polypropylene film of about 25 micrometers in thickness which formed the polyvinyl formal resin film mentioned above was used through 16 mm in diameter.

In a 2032 stainless battery tube, a negative electrode having a diameter of 14 mm, a diameter of 16 mm, a separator made of a microporous polypropylene film having a thickness of 25 μm, and a positive electrode having a diameter of 13.5 mm were stacked in this order. Then, 0.04 ml of nonaqueous electrolyte was injected into the separator, and the aluminum plate (thickness 1.2mm, diameter 16mm) and the spring were accommodated. Finally, in order to maintain the airtightness in a battery, the lid of a battery tube was firmly stuck through the polypropylene gasket. This was left to stand at room temperature for 12 hours to produce a coin-type lithium battery of Example 30.

As the non-aqueous electrolyte, EC and MEC are mixed at a ratio of 2: 3 (weight ratio), and these are added to the mixed solvent so as to have a content of 1 mol / liter of LiPF ₆ (electrolyte) and 1% of vinylene carbonate, Dissolved.

(Comparative Example 4)

A comparative coin-type lithium battery was produced in the same manner as in Example 20 using the nonaqueous electrolyte used in Example 30 as the nonaqueous electrolyte and using the same negative electrode, positive electrode and separator as in Example 20.

(Test Example 8)

<Measurement of viscosity of nonaqueous electrolyte solution>

The viscosity of 25 degreeC was measured about the nonaqueous electrolyte of Examples 20-29 and Comparative Example 4 using the E-type viscosity meter (made by Suegi Industries Co., Ltd.).

<Evaluation of Battery Characteristics>

The coin-type lithium batteries of Examples 20 to 29 and Comparative Examples 3 to 4 were first charged to 4.2 V at a current of 0.5 mA and then discharged until the voltage of the battery became 3 V at a constant current of 5 mA (initial charge). The discharge capacity at this time was made into "initial capacity." In addition, the ratio of the initial stage capacity | capacitance with respect to charging capacity was made into "the initial charge-discharge efficiency%). Next, the battery was discharged at a constant current of 5 mA until charging at 4.2 V until the voltage of the battery became 3 V, and the discharge capacity at this time was defined as “5 mA discharge capacity”. In addition, the ratio of 5 mA discharge capacity with respect to initial stage capacity was made into "5 mA discharge capacity ratio (%)." The measurement was performed at 25 degreeC. Next, after charging the battery to 4.1V and storing it for 2 days (referring to aging preservation) at 60 degreeC, the battery characteristic (5mA discharge capacity) was measured and 5mA discharge capacity ratio (%) was calculated | required. Subsequently, after charging at 4.2V for 3 days (referred to as high temperature storage) after charging to 4.2V, the battery characteristic (5mA discharge capacity) was measured, and 5mA discharge capacity ratio (%) was calculated | required. The storage characteristic was evaluated by comparing with the battery characteristic after initial stage charging. In addition, by the above-mentioned initial charge and aging preservation, the acid is sufficiently generated in the battery, and the polyvinyl formal resin dissolved or swelled in the nonaqueous electrolyte is acid-modified, further crosslinked, separated from the nonaqueous electrolyte, separated from the electrode and the separator. Is strongly bonded.

<Checking the adhesion between the electrode and the separator>

The battery was dismantled after the aging preservation and high temperature preservation tests, peeled off with the electrode and the separator, and examined for adhesiveness.

(Double-circle): The active material layer of a electrode and a separator were firmly in contact with each other, and even if peeling operation was carried out, it peeled from the interface of an electrical power collector and an active material layer, and the separator remained as it was attached to the active material layer of an electrode.

(Circle): Although the active material layer and separator of an electrode were fully in contact with each other, when a peeling operation was performed, the negative electrode peeled from the interface of the active material layer and a separator.

(Triangle | delta): Although the active material layer of a electrode and a separator were in close_contact | adherence, when a peeling operation was performed, the negative electrode peeled easily from the interface of the active material layer and a separator.

X: It peeled easily also from the interface of an active material layer and a separator by a peeling operation also with a positive electrode and a negative electrode.

××: It was not in close contact.

The results are shown in Table 10.

The lithium battery of the Example showed the battery characteristic equivalent to the comparative example 4 which is a normal lithium battery, and it turned out that an electrode and a separator are adhere | attached. In particular, the adhesion between the positive electrode and the separator was high.

By comparison of Example 20 and Examples 21-23, it turned out that the adhesiveness of an electrode and a separator can be improved further by addition of tristrimethylsilyl phosphate. In particular, the adhesion between the cathode and the separator was high.

By comparison of Examples 23-24, it turned out that the adhesiveness of an electrode and a separator can fully be improved by adding polyvinyl formal resin to 2% back and forth in electrolyte solution.

By comparison of Examples 26-29, when the polymerization degree of polyvinyl formal resin was reduced, it turned out that the viscosity of a nonaqueous electrolyte solution can be reduced.

In comparison with Example 30 and other examples and comparative examples, the use of a negative electrode in which a polyvinyl formal resin film was previously formed on the surface of the negative electrode was performed in comparison with the case where the negative electrode was not formed. It was found that the discharge efficiency improved by about 2% and the capacity of the battery also increased. Moreover, it turned out that the adhesiveness of an electrode and a separator also improves.

From Comparative Example 3, in the conventional gel electrolyte, even when the polymer component was 5%, sufficient adhesiveness could not be obtained.

As mentioned above, it is clear by this invention that the lithium battery which is excellent in shape retention property and excellent in charge / discharge load characteristic is obtained.

This invention can be implemented in other various forms, without deviating from the mind or main characteristic. Therefore, the above-described embodiments are merely examples in all respects, and the scope of the present invention is shown in the claims, and is not limited to the specification text at all. Moreover, all the modifications and variations that fall within the scope of the claims are within the scope of the present invention.

Claims (25)

The polyvinyl acetal resin is melt | dissolved in the non-aqueous solvent which consists of carbonate esters, and the said carbonate ester is a mixture of a cyclic carbonate ester and a chain carbonate ester, The polyvinyl acetal resin varnish characterized by the above-mentioned. delete The varnish of polyvinyl acetal resin according to claim 1, wherein the moisture content is 200 ppm or less. The polyvinyl acetal resin varnish according to claim 1 or 3, wherein the polyvinyl acetal resin is a polyvinyl formal resin. The polyvinyl acetal resin varnish according to claim 1 or 3, wherein the polyvinyl acetal resin is an acid modified substance. The content of proton according to claim 1 or 3, wherein the polyvinyl acetal resin exhibits a peak at 4.25 to 4.35 ppm based on the peak (2.49 ppm) of DMSO-d ₆ in ¹ H-NMR measurement. Polyvinyl acetal resin varnish, characterized in that / kg or less. The polyvinyl acetal resin varnish according to claim 1 or 3, wherein the hydroxyl group content of the polyvinyl acetal resin is 0.1 to 2 mol / kg. The gelling agent containing the polyvinyl acetal resin varnish of Claim 1 or 3, and gelatinizing an organic solvent. A nonaqueous electrolyte comprising an electrolyte and the polyvinyl acetal resin varnish according to claim 1. 10. The polyvinyl acetal resin has the following relationship between the number average molecular weight? Of the polystyrene conversion and the concentration c (% by weight) in the nonaqueous electrolyte of the polyvinyl acetal resin. Non-aqueous electrolyte. 100 ≤ λ ^1/2 × c ≤ 1000 10. The nonaqueous electrolyte according to claim 9, wherein the polyvinyl acetal resin has a concentration of 0.3 to 3.5% by weight based on the total amount of the nonaqueous electrolyte. 10. The nonaqueous electrolyte according to claim 9, wherein the nonaqueous electrolyte contains a compound that generates an acid. The nonaqueous electrolyte solution according to claim 12, wherein the compound which produces an acid is selected from the following 1) to 3): 1) Lewis acid with fluorine atom, 2) Lewis salts with fluorine atoms, and 3) Lewis acids with fluorine atoms and Lewis salts with fluorine atoms. An electrochemical device comprising the negative electrode, the separator, the positive electrode, and the nonaqueous electrolyte solution of claim 9 as essential components, wherein the electrode and the separator selected from the following 1) to 3) are adhered by a crosslinked product of polyvinyl acetal resin. Electrochemical device: 1) cathode, 2) an anode, and 3) cathode and anode. The electrochemical device according to claim 14, wherein the ratio of the crosslinked product of the polyvinyl acetal resin to the total amount of the crosslinked product and the nonaqueous electrolyte is 3.5% by weight or less. The negative electrode comprises an active material selected from the following 1) to 9), An electrochemical device characterized in that the anode comprises an active material capable of generating an electromotive force of 3 V or more with respect to the dissolution precipitation potential of lithium, and the nonaqueous electrolyte contains an electrolyte selected from lithium salts: 1) an active material capable of occluding lithium metal, 2) an active material capable of occluding lithium, 3) an active material capable of occluding lithium metal and lithium; 4) an active material capable of releasing lithium metal, 5) an active material capable of releasing lithium, 6) an active material capable of releasing lithium metal and lithium, 7) an active material capable of occluding and releasing lithium metal, 8) an active material capable of occluding and releasing lithium, and 9) An active material capable of occluding and releasing lithium metal and lithium. Stacked cathode, separator and anode, The laminated body is filled with the electrochemical element formed by impregnating the nonaqueous electrolyte solution of Claim 11, and the crosslinked material of polyvinyl acetal resin is produced | generated, A method for producing an electrochemical device, comprising adhering an electrode and a separator selected from the following 1) to 3) by the crosslinked product: 1) cathode, 2) an anode, and 3) cathode and anode. As polyvinyl acetal resin varnish, The acid modified substance of polyvinyl acetal resin is melt | dissolved in the non-aqueous solvent which consists of carbonate esters, Carbonate ester is a mixture of cyclic carbonate and linear carbonate ester, Water content is 200ppm or less, Polyvinyl acetal resin is polyvinyl formal resin, In the polyvinyl acetal resin, the content of protons exhibiting a peak at 4.25 to 4.45 ppm based on the peak of DMSO-d ₆ (2.49 ppm) in ¹ H-NMR measurement is 0.25 mol / kg or less, The hydroxyl group content of the acid-modified product of polyvinyl acetal resin is 0.1-2 mol / kg, The polyvinyl acetal resin varnish. The gelling agent containing the polyvinyl acetal resin varnish of Claim 18, and gelatinizing an organic solvent. A nonaqueous electrolyte comprising an electrolyte and the polyvinyl acetal resin varnish according to claim 18. The number average molecular weight λ of polystyrene conversion by the gel permeation chromatography measurement of polyvinyl acetal resin and the concentration c (% by weight) in the nonaqueous electrolyte of polyvinyl acetal resin have the following relationship. Non-aqueous electrolyte. 100 ≤ λ ^1/2 × c ≤ 1000 21. The nonaqueous electrolyte according to claim 20, wherein the polyvinyl acetal resin has a concentration of 0.3 to 3.5% by weight of the total amount of the nonaqueous electrolyte. 21. The nonaqueous electrolyte according to claim 20, wherein the nonaqueous electrolyte contains a compound that generates an acid. The non-aqueous electrolyte solution according to claim 23, wherein the compound which produces an acid is selected from the following 1) to 3): 1) Lewis acid with fluorine atom, 2) Lewis salts with fluorine atoms, and 3) Lewis acids with fluorine atoms and Lewis salts with fluorine atoms. Stacked cathode, separator and anode, The laminated body was filled with the electrochemical element formed by impregnating the nonaqueous electrolyte solution according to claim 22 to form a crosslinked product of a polyacetal resin. A method for producing an electrochemical device, comprising adhering an electrode and a separator selected from the following 1) to 3) by the crosslinked product: 1) cathode, 2) an anode, and 3) cathode and anode.