Manufacture of crosslinking polymer solid electrolyte

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a method for producing a polymer solid electrolyte used for manufacturing a primary battery, a secondary battery, etc., particularly a polymer solid electrolyte most suitable for a high temperature operating type secondary battery for electric vehicles and nighttime power storage.

【0002】

[Conventional technology]

Conventionally researched and developed solid electrolytes include β-alumina and Li.₂TiO₃, RbAg₄l₅, Silver iodide, or phosphotungstic acid, so-called inorganic materials are widely known. However, inorganic materials have drawbacks such as (1) heavy specific gravity, (2) inability to form into arbitrary shapes, (3) inability to obtain flexible and thin films, and (4) low ionic conductivity at room temperature. This is a practical problem.

【0003】

In recent years, organic materials have been attracting attention as materials for improving the above-mentioned drawbacks. The general composition of organic materials is LiClO on macromolecules such as polyalkylene oxide, silicone rubber, fluororesin or polyphosphazene.₄, LiBF₄It is composed of polymer solid electrolyte (SPE), which is a mixture of and dissolved electrolytes that serve as carriers. Such SPEs are lighter and more flexible than inorganic materials, and have the characteristics of being easy to mold and process into films, but they have been more practical while maintaining these characteristics for the past few years. R & D is being actively carried out to build a typical SPE.

【0004】

The application fields of SPE are roughly classified into (1) small low-power consumer secondary batteries that operate at room temperature, and (2) large high-power secondary batteries that operate at high temperatures. Here, (1) is a secondary battery using a so-called gel-like SPE as a diaphragm, which has improved ionic conductivity by absorbing and retaining a low boiling point aproton-based organic electrolytic solution in a polymer material. However, since the battery configuration is almost the same as that of a lithium-ion battery, it has already reached the stage of practical use as a small and ultra-thin battery with low output.

【0005】

On the other hand, (2) is a lithium polymer battery that assumes the use of lithium metal for the negative electrode, and is expected to be applied to electric vehicles and large secondary batteries for nighttime power storage in the near future. However, in these large batteries, the amount of heat generated during charging and discharging becomes enormous, and the temperature of the battery itself rises considerably. Therefore, when a gel-based SPE such as (1) is used, the outer can of the battery is affected by the vapor pressure of the electrolytic solution. It has been pointed out that there is a danger that the battery will swell or, in the worst case, explode. Therefore, in order to solve these problems, a so-called high-temperature operation type large secondary battery, which has improved ionic conductivity by raising the temperature of SPE alone (dry type) to 60 to 80 ° C, has been proposed in Europe and the United States. Long-term research and development has been carried out mainly. However, the reality is that SPE, which is highly safe even in such a high temperature region, has excellent film strength, and does not generate vapor pressure at all in the battery system, has not yet been obtained. [0006]

[Problems to be Solved by the Invention]

Examples of the research in (2) above include M. Watanabe et al, So1id State Ionics 79, (1995) 306-312. And S. Kohjiya et al, Second International Symposium on Polymer Electorolytes, ed. By B. Scrosati, Elsevier. , Appl.Sci., London (1990), pp.187-196., Etc., but all SPEs have an ionic conductivity near room temperature of 10.^-4Although it reaches the S / cm level, the film strength is not sufficient and it has not been put into practical use.

【0007】

On the other hand, the Applicants first mentioned Patent No. 1842047 (Japanese Patent Publication No. 5-51612) and Makromol.Chem.Macromol.Symp.25 (1989) 249, Reactive and Functional Polymers, 37 (1998) 169-182. And J. Polym. Sci., Part A: Polym. Chem., 36, (1998) 3021-3034, etc., proposed a method for synthesizing a block-graft copolymer as a model of the present invention.

【0008】

Further, in Patent No. 1842048 (Japanese Patent Publication No. 5-51632), in order to utilize this block-graft copolymer as an ionic conductive solid, 0.05 to 80 mol% of Li, with respect to its alkylene oxide unit, A block-graft copolymer composition in which an inorganic salt containing at least one element selected from Na, K, Cs, Ag, Cu and Mg is mixed is proposed as an SPE. We proposed a Li battery containing a composite of the block-graft copolymer with the Li ion salt as an electrolyte. However, all of the above proposals have not been put into practical use because their ionic conductivity at room temperature is low.

【0009】

Therefore, in order to improve the ionic conductivity at room temperature, the applicant has stated in Japanese Patent Application Laid-Open No. 3-188151 that a block-is obtained by adding a polyalkylene oxide to an inorganic ion salt composite of a block-graft copolymer. We have proposed a graft copolymer composition, but if too much polyalkylene oxide is added to the block-graft copolymer, the polystyrene domain that maintains the mechanical strength will be partially dissolved and the film strength will be weakened. It turned out that it would end up.

【0010】

In order to solve this newly derived problem, the applicant has stated in Japanese Patent Application Laid-Open No. 10-237143 that a block using polystyrene substituted with a silyl group, which is insoluble in various polyalkylene oxides, as a block chain. -We developed a graft copolymer and proposed a block-graft copolymer composition to which polyalkylene oxide was added. Further, in JP-A-10-208545, in order to protect the polystyrene domain from the solubility of the polyalkylene oxide added in a large amount to the block-graft copolymer, the polystyrene domain is chemically crosslinked using a cross-linking agent. , Proposed a cross-linked SPE with a rope structure. Further, in JP-A-10-223042 and JP-A-10-245427, self-crosslinking capable of easily cross-linking a polystyrene domain simply by irradiating with high energy rays without adding a cross-linking agent. A type block-graft copolymer was proposed.

【0011】

As a result, an SPE with greatly improved ionic conductivity and film strength not only near room temperature but also at high temperatures (60 to 80 ° C) was completed, and high-temperature batteries at a practical level could be easily and mass-produced. I can now do it.

【0012】

However, some types of polyalkylene oxides added to the block-graft copolymer exhibit some vapor pressure in the temperature range of 60 to 80 ° C. In addition, when this SPE is applied to a large battery that operates at a high temperature, the temperature often rises by several tens of degrees from the assumed temperature range depending on the operating conditions of the battery, so there is a temperature margin on the high temperature side. Wider and safer batteries are required.

【0013】

Therefore, an object of the present invention is to obtain a three-dimensional network structure by simultaneously cross-linking a self-crosslinking block-graft copolymer and an added reactive polyalkylene oxide with respect to a polymer-based solid electrolyte. An attempt to provide a method for producing a crosslinked polymer solid electrolyte having high ionic conductivity, high film strength, and excellent moldability and processability without generating vapor pressure even at a high temperature of 100 ° C or higher. It is something to do.

【0014】

[Means for Solving Problems and Embodiments of the Invention]

In order to solve such a problem, the present invention presents a block chain A composed of repeating units represented by the following general formula I, a block chain B composed of repeating units represented by the following general formula II, and / or the following general formula. A self-crosslinking block-graft copolymer composed of a block chain C composed of a repeating unit represented by III is added with a reactive polyalkylene oxide represented by the following general formula IV and a lithium-based inorganic salt, and the above self-crosslinking is performed. Provided is a method for producing a crosslinked polymer solid electrolyte, which comprises crosslinking a type block-graft copolymer and the above-mentioned reactive polyalkylene oxide.

【0015】

In this case, in particular, at least one block chain A having a degree of polymerization of 10 or more consisting of repeating units represented by the general formula I and at least one block having a degree of polymerization of 300 or more consisting of repeating units represented by the general formula II. A self-crosslinked block-graft copolymer composed of chain B and having a composition ratio (degree of polymerization ratio) of block chain A and block chain B of 1:30 to 30: 1 and a degree of polymerization of 310 or more, or general It is composed of at least one block chain A having a degree of polymerization of 10 or more composed of repeating units represented by the formula I, and at least one block chain C having a degree of polymerization of 200 or more consisting of repeating units represented by the general formula III. , Reactivity represented by the general formula IV to a self-crosslinking block-graft copolymer having a degree of polymerization of 210 or more and a composition ratio (degree of polymerization ratio) of block chain A and block chain C of 1: 20 to 20: 1. The self-crosslinking block-graft is added by adding a polyalkylene oxide, preferably a monofunctional and a bifunctional polyalkylene oxide in combination, and adding a lithium-based inorganic salt, preferably by irradiating an electron beam. It is preferable to carry out a cross-linking reaction between the copolymer and the above-mentioned reactive polyalkylene oxide.

【0016】

[Chemical 5]

<img file="JP2000285751A_D0001.tif" />(Here, R¹Is a hydrogen atom, methyl or ethyl group, R²Is a hydrogen atom or a methyl group, R³Is an alkyl group, an aryl group, an acyl group, a silyl group or a cyanoalkyl group, and n is an integer of 1 to 100. The number average molecular weight of the graft chain represented by Ia below in the formula is 45 to 4,400.

【0017】

[Chemical 6]

<img file="JP2000285751A_D0002.tif" />(Here, R⁴Is a hydrogen atom, a methyl or ethyl group, and y is 2 or 3.

【0018】

[Chemical 7]

<img file="JP2000285751A_D0003.tif" />(Here, R⁴And R⁵Is a hydrogen atom, a methyl or ethyl group, and y is 2 or 3. The total of k and m is more than 200, and the composition ratio of k and m is 95: 5 to 50:50. The arrangement method is random or alternating.

【0019】

[Chemical 8]

<img file="JP2000285751A_D0004.tif" />(Here, R⁶And R⁷Is a hydrogen atom or a methyl group, R⁸Is H₂C = CHCO-, H₂C = C (CH)₃) CO-, vinyl group, allyl group, epoxide, alkyl group with 25 or less carbon atoms, phenyl group or substituted phenyl group, R⁹Is ethylene oxide or tetramethylene oxide. Both e and f are integers from 0 to 25, but they cannot be 0 at the same time, and when one is 0, the other is always an integer of 1 or more. X is -PhC (CH)₃)₂Indicates PhO- or single bond. In addition, Ph represents a phenylene group.

【0020】

In this method, the reactive polyalkylene oxide is compatible with the graft component of the self-crosslinking block-graft copolymer, and both can be crosslinked at the same time in a state where a microphase-separated structure is formed. The stem molecules increase the mechanical strength of the film, the graft components and the crosslinked polyalkylene oxide form a continuous phase to secure the passage of metal ions, and no vapor pressure is generated from the polyalkylene oxide, which is thermally stable. A high-quality film can be formed.

【0021】

Then, as the reactive polyalkylene oxide, a monofunctional or bifunctional acrylate-based, methacrylate-based, allyl-based, epoxide or the like represented by the general formula IV is used, and for example, if it is irradiated with an electron beam, it is reactive. The cross-linking reaction of the polyalkylene oxide can be completed.

【0022】

By this production method, it is possible to easily and surely produce a crosslinked polymer solid electrolyte having high ionic conductivity and high film strength without generating any vapor pressure even at a high temperature. In order to take advantage of the characteristics of the block-graft copolymer to maintain excellent mechanical strength and high ionic conductivity even at high temperatures, and to obtain a safe polymer electrolyte, self-crosslinking block-graft copolymer weight It was found that it would be effective if both the coalescence and the polyalkylene oxide added thereto were crosslinked at the same time to form a three-dimensional network structure, and the present invention was completed.

【0023】

Hereinafter, the present invention will be described in more detail. As described above, the block-graft copolymer which is the basis of the crosslinked polymer solid electrolyte of the present invention is composed of the block chain A composed of the repeating unit represented by the general formula I and the repeating unit represented by the general formula II. A block-graft copolymer composed of a block chain B and / or a block chain C composed of a repeating unit represented by the general formula III, particularly preferably Patent No. 1842047 and JP-A-10-237143 described above. It is basically the same as that disclosed in the publication, but when the structure is shown again, at least one type of block chain A having a degree of polymerization of 10 or more composed of repeating units represented by the general formula I and The composition ratio (degree of polymerization ratio) of block chain A and block chain B, which is composed of at least one type of block chain B having a degree of polymerization of 300 or more consisting of repeating units represented by the general formula II, is 1: 30 to 30 :. It consists of a block-graft copolymer having a degree of polymerization of 310 or more, which is 1, or at least one block chain A having a degree of polymerization of 10 or more consisting of a repeating unit represented by the general formula I, and a repeating unit represented by the general formula III. A block with a degree of polymerization of 210 or more, which is composed of at least one type of block chain C having a degree of polymerization of 200 or more and has a composition ratio (degree of polymerization ratio) of block chain A and block chain C of 1: 20 to 20: 1. It is a graft copolymer.

【0024】

[Chemical 9]

<img file="JP2000285751A_D0005.tif" />(Here, R¹Is a hydrogen atom, methyl or ethyl group, R²Is a hydrogen atom or a methyl group, R³Is an alkyl group, an aryl group, an acyl group, a silyl group or a cyanoalkyl group, and n is an integer of 1 to 100. In the formula, the number average molecular weight of the graft chain represented by Ia below is 45 to 4,400.

【0025】

[Chemical 10]

<img file="JP2000285751A_D0006.tif" />【0026】

Where R³The alkyl group is preferably 1 to 10 carbon atoms, particularly 1 to 2 carbon groups, and the aryl group is 6 to 10 carbon atoms, particularly 6 to 8 carbon atoms, and a phenyl group is particularly preferable. Examples of the acyl group include those having 1 to 9 carbon atoms, particularly 1 to 2 carbon atoms , and specific examples thereof include a formyl group and an acetyl group. As a silyl group, -SiR₃(R is a monovalent hydrocarbon group having the same or different carbon atoms of 3 to 15, particularly 3 to 6, preferably an alkyl group). Examples of the cyanoalkyl group include a cyanoethyl group and a cyanopropyl group in which a part of hydrogen atoms of an alkyl group having 2 to 10 carbon atoms, particularly 2 to 4 carbon atoms, is replaced with a cyano group.

【0027】

[Chemical 11]

<img file="JP2000285751A_D0007.tif" />(Here, R⁴Is a hydrogen atom, a methyl or ethyl group, and y is 2 or 3.

【0028】

[Chemical 12]

<img file="JP2000285751A_D0008.tif" />(Here, R⁴And R⁵Is a hydrogen atom, a methyl or ethyl group, and y is 2 or 3. The total of k and m is more than 200, and the composition ratio of k and m is 95: 5 to 50:50. The arrangement method is random or alternating.

【0029】

This block-graft copolymer is composed of a block chain A composed of the same or different repeating units represented by the general formula I, a block chain B composed of the same or different repeating units represented by the general formula II, and / or a general formula. The block chain C consisting of the same or different repeating units represented by III is arbitrarily arranged such as AB, AC, BAB, BAB', CAC, C'AC, BAC, BAB'AB, C'ABAC. However, preferably BAB, BAB', B'ABAB', BAB'AB, CAC, CAC', C'ACAC', CAC'AC, and more preferably BAB, BAB', CAC, CAC', etc. An array can be mentioned. In this sequence example, B, B'and C, C'are included in the block chain B and the block chain C, respectively, but R⁴And R⁵Indicates that the block chains are different from each other or have different degrees of polymerization.

【0030】

The degree of polymerization of the block chains A of the polymer is preferably 10 or more, the degree of polymerization of B is preferably 300 or more, and the degree of polymerization of C is 200 or more. It is preferably 1: 30 to 30: 1, and preferably 1: 20 to 20: 1 for block chains A and C. The degree of polymerization of the block-graft copolymer obtained by copolymerization is preferably 310 or more and 50,000 or less for the sequences of block chains A and B, and 210 or more and 50,000 or less for the sequences of block chains A and C.

【0031】

The block chain A of the polymer is a part that functions as a polymer electrolyte, and when the degree of polymerization is less than 10, it does not show a microphase-separated structure in which the ionic conductive domain, which is a characteristic of this polymer, is a continuous phase. There is. Further, since the block chain B is a portion that retains the mechanical strength, if the degree of polymerization is less than 300, the entanglement between the polymer molecules is insufficient and the mechanical strength of the film is lowered. In other words, if the composition ratio of block chains A and B is less than 1:30, the graft component is too small and it becomes difficult to retain the function as a polymer electrolyte, and if it exceeds 30: 1, the stem component as a block chain There is a risk that the mechanical strength cannot be maintained. However, since the mechanical strength of the block chain C, which has a higher Tg of the polymer than the block chain B, can be maintained even at an exceptionally low degree of polymerization, the degree of polymerization is 200 or more here, and the composition ratio with the block chain A ( The degree of polymerization ratio) can be 1: 20 to 20: 1, and the degree of polymerization of the copolymer obtained by copolymerization can be 210 or more.

【0032】

In the crosslinked polymer solid electrolyte of the present invention, a reactive polyalkylene oxide represented by the following general formula IV and a lithium-based inorganic salt are added to the block-graft copolymer to form the block-graft copolymer and its reactivity. It is a cross-linking reaction of a polyalkylene oxide.

【0033】

[Chemical 13]

<img file="JP2000285751A_D0009.tif" />(Here, R⁶And R⁷Is a hydrogen atom or a methyl group, R⁸Is H₂C = CHCO-, H₂C = C (CH)₃) CO-, vinyl group, allyl group, epoxide, alkyl group with 25 or less carbon atoms, phenyl group or substituted phenyl group, R⁹Is ethylene oxide or tetramethylene oxide. Both e and f are integers from 0 to 25, but they cannot be 0 at the same time, and when one is 0, the other is always an integer of 1 or more. X is -PhC (CH)₃)₂Indicates PhO- or single bond. In addition, Ph represents a phenylene group.

【0034】

R above⁸Examples of the epoxide of the above are those represented by the following formulas.

【0035】

[Chemical 14]

<img file="JP2000285751A_D0010.tif" />(However, p is an integer of 1 to 25 and q is an integer of 1 to 25.) Also, R⁸Examples of the substituted phenyl group of the above include a tolyl group, a xylyl group and the like.

【0036】

The reactive polyalkylene oxide added to the block-graft copolymer is preferably a polyalkylene glycol acrylate derivative, a methacrylate derivative, a vinyl derivative, or the like, and does not contain active hydrogen, halogen, or the like in its structure. .. Specifically, methoxyethylene glycol mono (meth) acrylate, methoxypolyethylene glycol mono (meth) acrylate, octoxypolyethylene glycol-block-polyethylene glycol mono (meth) acrylate, lauroxypolyethylene glycol mono (meth) acrylate, stearoxy. Polyethylene glycol mono (meth) acrylate, allyloxy polyethylene glycol mono (meth) acrylate, nonylphenoxy polyethylene glycol mono (meth) acrylate, nonylphenoxypolyethylene glycol mono (meth) acrylate, nonylphenoxypoly (ethylene glycol-propylene glycol) mono ( Meta) acrylate, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, polyethylene glycol-block-polyethylene glycol-block-polyethylene glycol di ( Examples thereof include meta) acrylate, polytetramethylene glycol di (meth) acrylate, poly (ethylene glycol-tetramethylene glycol) di (meth) acrylate, and poly (propylene glycol-tetramethylene glycol) di (meth) acrylate. In addition, ethylene oxide-modified bisphenol A di (meth) acrylate in which block chains e and f are bonded with bisphenol A, ethylene oxide-propylene oxide-modified bisphenol A di (meth) acrylate, and propylene oxide-tetramethylene oxide-modified bisphenol A. Di (meth) acrylate, ethylene oxide-block-propylene oxide modified bisphenol

【0037】

In the present invention, basically, a monofunctional polyalkylene oxide and a bifunctional polyalkylene oxide are used in combination. It is also effective to mix and use two or more types of polyalkylene oxides having the same number of functional groups. Further, although not illustrated here, the use of trifunctional or higher functional polyalkylene oxides increases the crosslink density, which is effective when it is desired to improve the film strength at the expense of some ionic conductivity. It becomes a means.

【0038】

The amount of the reactive polyalkylene oxide added is 5% by weight or more, preferably 50 to 600% by weight, based on the block-graft copolymer, and the mixing ratio of the monofunctional polyalkylene oxide and the bifunctional polyalkylene oxide is Is a weight ratio of 5:95 to 95: 5, preferably 10:90 to 70:30. Further, the mixing ratio of the reactive polyalkylene oxides having the same number of functional groups and different types is not particularly limited.

【0039】

The reactive polyalkylene oxide can be added, for example, by adding it to a block-graft copolymer and mechanically kneading it at room temperature or under heating, or by dissolving it in a common solvent with the block-graft copolymer and then casting it. There are various methods for forming a film, but since this block-graft copolymer also has a high function as a polymer compatibilizer, the alkylene oxide added by various methods automatically becomes a graft phase. Assemble to form a microphase-separated structure. Therefore, the addition method is arbitrary and is not particularly limited.

【0040】

The type of lithium-based inorganic salts added to the block-graft copolymer is LiClO.₄, LiBF₄, LiPF₆, LiAsF₆, LiCF₃SO₃And LiN (CF)₃SO₂)₂At least one compound selected from is preferable. The addition ratio is preferably 0.01 to 80 mol%, preferably 0.02 to 15 mol%, based on the total number of moles of the alkylene oxide unit of the reactive polyalkylene oxide added to the graft chain of the block-graft copolymer. Yes, there are no restrictions on the method of addition thereof, as with polyalkylene oxide.

【0041】

In the present invention, as a method for cross-linking the reactive polyalkylene oxide added to the block-graft copolymer, a method of cross-linking by heat (thermal cross-linking), a method of irradiating ultraviolet rays to cross-link (ultraviolet irradiation), and electrons. An example is a method of irradiating a line to crosslink (electron beam irradiation). For thermal cross-linking, organic peroxides such as 2,2'-azobis (isobutyronitrile), benzoyl peroxide, and methyl ethyl ketone peroxide are added as thermal polymerization initiators in advance, and the temperature is 85 ° C or higher after film formation. It is a method of heating for a predetermined time, and the ultraviolet irradiation is performed in advance with 2,2-dimethoxy-2-phenylacetophen, benzylmethylketal, trimethylsilylbenzophenone, 2-methylbenzoin, 4-methoxybenzophenone, benzoinmethylether, anthraquinone, etc. This is a method in which the photopolymerization initiator of No. 1 is added, and after film formation, UV irradiation is performed for 3 minutes or more with, for example, a 500 W high-pressure mercury lamp. Further, electron beam irradiation is a method of irradiating an electron beam with an irradiation dose of 5 to 100 Mard. Using an electron beam irradiation device after film formation. As mentioned above, a radical generator (polymerization initiator) is required for thermal cross-linking and ultraviolet irradiation, but the use of this makes the reaction system more complicated and, in some cases, adversely affects the transport of lithium ions. There is also concern about the effect. Therefore, in the present invention, the cross-linking method using an electron beam (radiation), which has a high energy level, is easy to control, and does not require a radical generator, is optimal. When various tests were conducted using 180L] at an acceleration voltage of 200kV and 5 to 100Mrad., It was confirmed that the cross-linking method was very excellent.

【0042】

In the polymer solid electrolyte according to the present invention, the self-crosslinking block-graft copolymer, which is a component thereof, (1) exhibits a clear microphase separation structure, and (2) a stem molecule having high mechanical strength is pseudo-crosslinked. It forms a structure, plays a role of structure retention and enhances material strength, (3) forms a continuous phase even if the graft component is a relatively small molecule, and secures a passage for metal ions, (4) the graft component is copolymerized. Since it has a function as an agent, a large amount of polyalkylene oxide can be stably retained in the film. (5) Since there are no volatile components in the system, it has excellent thermal stability at high temperatures and is highly safe. It has various characteristics.

【0043】

Therefore, when the polymer solid electrolyte of the present invention is applied to, for example, a lithium polymer secondary battery that operates at a high temperature for electric vehicles and nighttime power storage, which are expected to be put into practical use in the future, the weight and thickness of the battery can be reduced. It is possible to make a battery that is very effective and extremely safe.

【0044】

Further, the crosslinked polymer electrolyte of the present invention is also effective when used for various solid-state electrochemical elements such as primary batteries, capacitors, electrochromic displays and sensors, in addition to secondary battery elements.

【0045】

[Example]

Hereinafter, embodiments of the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the block copolymer in the example, each component is connected by -b-, and for example, a three-component block copolymer of polybutenylstyrene, poly-p-hydroxystyrene, and polybutenylstyrene is poly (butenyl). Styrene-bp-hydroxystyrene-b-butenylstyrene), a block chain consisting of a [random / alternating] copolymer of polybutenylstyrene and polystyrene connected with -CO- and a graft chain with -g-. Represent.

【0046】

[Example 1] Electrocrosslinking of a self-crosslinking block-graft copolymer film to which a reactive polyalkylene oxide and a lithium-based inorganic salt are added I The molecular structure of the block-graft copolymer used in Example 1, the composition ratio of each block chain, the composition of the graft chain, and the like are shown below.

【0047】

Block-graft copolymer sample No. B-1 (1) Molecular structure: Poly [butenyl styrene-b- (p-hydroxystyrene-g-ethylene oxide) -b-butenyl styrene] (2) Block chain A (general formula I): R¹= Hydrogen atom, R²= Hydrogen atom, R³= Methyl group, degree of polymerization = 250 (3) Block chain B (general formula II): R⁴= Hydrogen atom, y = 2, degree of polymerization = 500 (4) Block chain arrangement method: BAB (triblock copolymer) (5) Block chain composition ratio (polymerization degree ratio): B: A: B = 500: 250: 500 = 2: 1: 2 (2B: A = 4: 1) (6) Graft chain (general formula Ia): R²= Hydrogen atom, R³= Methyl group, n (degree of polymerization) = 15, number average molecular weight (Mn) = 660 5.0 g of the self-crosslinked block-graft copolymer (Sample No. B-1), 2.0 g of methoxypolyethylene glycol monomethacrylate (Mn = 276), 1.0 g of polyethylene glycol diacrylate (Mn = 214) and LiClO₄After dissolving 0.5 g in 60 ml of dimethyl carbonate, it was flowed into a Teflon petri dish. This sample was allowed to stand at room temperature for about 20 hours under an argon air stream to remove excess solvent, and then heated and dried at 80 ° C. for 2 hours to obtain a film having a film thickness of 20 μm. After irradiating this film with an electron beam having an acceleration voltage of 200 kV and a dose of 10 Mrad., The obtained sample was thermally analyzed with a differential thermal balance DSC-20 (trade name manufactured by Seiko Denshi Kogyo Co., Ltd.). As a result, a weight loss of 1% or less, which was thought to be caused by dimethyl carbonate, was observed around 90 ° C, but no weight change was observed until 250 ° C after that, so the block-graft copolymer weight was observed. The reactive polyalkylene oxide added to the coalescence is completely crosslinked, does not volatilize even at high temperatures of 100-250 ° C, and therefore does not generate vapor pressure and remains stable in the graft phase. all right.

【0048】

[Example 2] Electrocrosslinking of a self-crosslinking block-graft copolymer film to which a reactive polyalkylene oxide and a lithium-based inorganic salt are added II A sample obtained by irradiating a film prepared with the same formulation as in Example 1 before electron beam irradiation with an electron beam having an acceleration voltage of 200 kV and a dose of 1 to 3 Mrad. Was thermally analyzed. Weight loss was observed. On the other hand, all the samples irradiated with a dose of 5 to 100 Mard. Were stable up to 250 ° C, and no weight loss other than the solvent was observed. Therefore, in the following examples, the added reactive polyalkylene oxide can be completely crosslinked, and an irradiation dose of 10 Mrad., Which does not generate vapor pressure even at a high temperature of 100 to 250 ° C., is used as a reference irradiation. The amount was taken.

【0049】

[Example 3] A film prepared with the same formulation as in Example 1 was irradiated with an electron beam having an acceleration voltage of 200 kV and a dose of 10 Mrad., And the obtained sample was vacuum-dried at 100 ° C for 20 hours to achieve a film thickness of 20 μm. A crosslinked polymer solid electrolyte film was obtained. The obtained film is tough despite containing a large amount of polyalkylene oxide, and the storage elastic modulus obtained from the dynamic viscoelasticity tester RSA-II (trade name manufactured by Reometric Inc.) is 30 ° C. At 9.5 x 10⁶Pa, 8.4 × 10 even at 80 ° C⁶Pa and above were shown. In addition, this electrolyte film is 100 kg / cm at 20 ° C.²The polyalkylene oxide contained therein did not exude at all even when compressed under the load of.

【0050】

This film is cut into a disk shape with a diameter of 10 mm, and both sides are sandwiched between lithium metal plates to form electrodes, and an AC impedance measuring device with a frequency of 5 Hz to 5 MHz (multi-frequency LCRX meter 4192A, manufactured by Yokogawa Hewlett-Packard Co., Ltd.) The ionic conductivity was calculated by the complex impedance method using the trade name). As a result, 0.7 × 10 at 80 ° C^-3A value of S / cm was obtained.

【0051】

[Examples 4 to 9] The molecular structure of the self-crosslinked block-graft copolymer (Sample No. B-2 to BT-2) used in Examples 4 to 9, the composition ratio of each block chain, and the graft chain. The composition and the like are shown below. In addition, after adding different types of reactive polyalkylene oxides and lithium-based inorganic salts to the following self-crosslinking block-graft copolymer, a crosslinked polymer solid electrolyte film crosslinked by irradiation with an electron beam was used. When the same evaluation as in Example 3 was performed, the results shown in Table 1 were obtained.

【0052】

Sample No. B-2 (1) Molecular structure: Poly [butenyl styrene-b- (p-hydroxystyrene-g-ethylene oxide) -b-butenyl styrene] (2) Block chain A (general formula I): R¹= Hydrogen atom, R²= Hydrogen atom, R³= Methyl group, degree of polymerization = 250 (3) Block chain B (general formula II): R⁴= Hydrogen atom, y = 2, degree of polymerization = 500 (4) Block chain arrangement method: BAB (triblock copolymer) (5) Block chain composition ratio (polymerization degree ratio): B: A: B = 500: 250: 500 = 2: 1: 2 (2B: A = 4: 1) (6) Graft chain (general formula Ia): R²= Hydrogen atom, R³= Methyl group, n = 23, number average molecular weight (Mn) = 1010 [0053]

Sample No.BT-1 (1) Molecular structure: Poly [(Styrene-co-butenyl styrene) -b- (p-hydroxystyrene-g-ethylene oxide) -b- (styrene-co-butenyl styrene)] (2) Block chain A (general formula I): R¹= Hydrogen atom, R²= Hydrogen atom, R³= Methyl group, degree of polymerization = 250 (3) Block chain C (general formula III): R⁴= Hydrogen atom, R⁵= Hydrogen atom, y = 2, m (degree of polymerization) = 100, k (degree of polymerization) = 400 (4) Block chain arrangement method: CAC (triblock copolymer) (5) Block chain composition ratio (polymerization degree ratio): C: A: C = (100 + 400): 250: (100 + 400) = 2: 1: 2 (2C: A = 4: 1) (6) Graft chain (general formula Ia): R²= Hydrogen atom, R³= Methyl group, n = 9, number average molecular weight (Mn) = 400 [0054]

Sample No. BT-2 (1) Molecular structure: Poly [(Styrene-co-butenyl styrene) -b- (p-hydroxystyrene-g-ethylene oxide) -b- (styrene-co-butenyl styrene)] (2) Block chain A (general formula I): R¹= Hydrogen atom, R²= Hydrogen atom, R³= Methyl group, degree of polymerization = 250 (3) Block chain C (general formula III): R⁴= Hydrogen atom, R⁵= Hydrogen atom, y = 2, m (degree of polymerization) = 50, k (degree of polymerization) = 450 (4) Block chain arrangement method: CAC (triblock copolymer) (5) Block chain composition ratio (polymerization degree ratio): C: A: C = (50 + 450): 250: (50 + 450) = 2: 1: 2 (2C: A = 4: 1) (6) Graft chain (general formula Ia): R²= Hydrogen atom, R³= Methyl group, n = 14, number average molecular weight (Mn) = 620 [0055]

[table 1]

<img file="JP2000285751A_D0011.tif" />A: Methoxypolyethylene glycol monomethacrylate (Mn = 276) B: Polyethylene glycol diacrylate (Mn = 302) C: Methoxypolyethylene glycol monoacrylate (Mn = 466) D: Polypropylene glycol dimethacrylate (Mn = 386) E: Methoxypolyethylene glycol monomethacrylate (Mn = 496) F: Aryloxy Polyethylene Glycol Monomethacrylate (Mn = 214) G: Octoxy Polyethylene Glycol-Polypropylene Glycol Monomethacrylate (Mn = 898) H: Polypropylene glycol diacrylate (Mn = 302) I: Poly (ethylene glycol-tetramethylene glycol) dimethacrylate (Mn = 600) J: Lauroxy Polyethylene Glycol Monoacrylate (Mn = 400) K: Polypropylene glycol diacrylate (Mn = 518) L: Methoxypolyethylene glycol monoacrylate (Mn = 482) M: Allyloxy polyethylene glycol monoacrylate (Mn = 380) [0056]

From these results, the crosslinked polymer solid electrolyte produced by the present invention contains a large amount of polyalkylene oxide and lithium-based inorganic salts in the film, even at a high temperature of 100 ° C. or higher. It was found that the film has high ionic conductivity and high film strength without generating vapor pressure.

【0057】

[Comparative Example 1] A film-like solid electrolyte having a film thickness of 100 μm was prepared according to the method for forming a polymer solid electrolyte described in US Pat. No. 5,296,318. The method is VdF / HFP copolymer [Atochem Kyner FLEX 2801 (trade name)] 5.0 g, methoxypolyethylene glycol monomethacrylate (Mn = 273) 2.0 g, polyethylene glycol diacrylate (Mn = 214) 1.0 g and LiClO.₄After 0.5 g was dissolved and mixed in 50 ml of tetrahydrofuran, it was flowed into a Teflon petri dish. This sample was allowed to stand at room temperature for about 20 hours under an argon air stream to remove excess solvent, and then heated and dried at 80 ° C. for 2 hours. However, since Atochem Kyner FLEX 2801 and polyalkylene oxide were not compatible at all, macro phase separation occurred and only a semi-solid film that did not completely solidify could be obtained.

【0058】

[Comparative Example 2] When the semi-solid film prepared in Comparative Example 1 was irradiated with an electron beam having an acceleration voltage of 200 kV and a dose of 10 Mrad., An inhomogeneous film in which macrophase separation remained was obtained. At an electron beam dose of 50 Mad. Or higher, the decomposition reaction of Atochem Kyner FLEX 2801 proceeded and fluorine gas was generated.

【0059】

[Effect of the invention]

According to the present invention, a crosslinked polymer solid electrolyte suitable for use as a large secondary battery or the like, which has excellent film strength, high ionic conductivity, good moldability into a film, and good processability, can be obtained.