JPH10125134A - Polymer electrolyte - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer electrolyte with high ion conductivity, high film forming capability, high flexibility, and high mechanical strength. SOLUTION: A polymer electrolyte contains repeating monomers of polymer containing a fluorine atom and lithium carboxylate in the functional group and an organic solvent, and in addition a metal salt is added to the polymer electrolyte. As the metal salt, an alkali metal salt is also used. Lithium trifluoromethacrylate is used as the repeated monomer of the polymer, and a monomer capable of copolymerizing with the repeated monomer of lithium trifluoromethacrylate are used to constitute the polymer electrolyte. As the organic solvent, an organic solvent having at least one of an oxygen atom and a nitrogen atom in the structure, or a solvent prepared by mixing two or more of these organic solvents is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer electrolyte having ion conductivity, and more particularly, to a polymer electrolyte having high ion conductivity by containing an alkali metal ion type conductive carrier such as lithium ion. And
Also, the present invention relates to a polymer electrolyte having excellent film-forming properties, flexibility, and mechanical strength.

[0002]

2. Description of the Related Art A battery using a polymer electrolyte has improved reliability without leakage, and can be thinned, laminated and flexible, and uses an organic solvent for the electrolyte. There are advantages such as higher flame retardancy. From such a viewpoint, polymer electrolytes are receiving attention as electrochemical device materials. The properties required for this polymer electrolyte are generally high ionic conductivity, no electron conductivity, excellent film-forming properties so that it can be formed into a thin shape, and excellent flexibility. And the like.

There are two types of such polymer electrolytes: (A) an all solid type polymer electrolyte comprising a polymer and a metal salt; and (B) a gel type polymer electrolyte comprising a polymer, a metal salt and a low molecular weight solvent. Can be roughly divided into

As the all-solid type polymer electrolyte (A), polyethylene oxide having a polyether structure [(−
CH ₂ CH ₂ O—) _n ]: (PEO), Li salt or Na
A complex with an alkali metal salt such as a salt is known to exhibit relatively high alkali metal ion conductivity. However, in the case of a composite film of PEO and an alkali metal salt, the molecular weight of the organic polymer constituting the composite film is 1000.
At about 0, the film formability is excellent, and the ionic conductivity has a relatively high value of about 10 ⁻³ to 10 ⁻⁴ S / cm at a temperature of 100 ° C. or higher. However, the ionic conductivity of this composite membrane rapidly decreases at a temperature of 60 ° C. or lower, and at room temperature, 10 ⁻⁷ S /
It shows a very low value of about cm or less. For this reason, it becomes impossible to incorporate it as a material for a normal battery having a room temperature in a use temperature range.

Therefore, as shown in chemical formulas (2), (3) and (4), a polymer electrolyte comprising various organic polymers having a structure similar to PEO and an alkali metal salt has been developed. The ionic conductivity is about 10 ⁻⁵ S / cm, which is slightly improved as compared with the composite membrane composed of PEO and an alkali metal salt, but is still insufficient in practical use. And poor flexibility.

[0006]

Embedded image

Embedded image

Embedded image Where m and n are arbitrary integers

On the other hand, polyvinylidene fluoride (PVdF), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), and polymethyl methacrylate (PMMA) are used for the polymer of the gel type polymer electrolyte (B). And the like. A gel-type polymer electrolyte obtained by swelling a low-molecular solution obtained by dissolving a metal salt in these polymers has a high ionic conductivity of about 10 ⁻³ S / cm. At this time, in order to prevent the polymer itself from dissolving even when the solvent is swollen, improvements such as cross-linking by actinic radiation, light, electron beam, heating, and the like are performed to secure mechanical strength. A way to do this is also being considered.

However, compared to conventional electrolytes comprising an organic solvent and a metal salt, there is a need for an electrolyte having a lower ionic conductivity and a higher mechanical strength.

[0009]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a polymer electrolyte which exhibits high ionic conductivity even at around room temperature, and is excellent in film formability, flexibility and mechanical strength. It is.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and comprises a polymer repeating monomer containing a fluorine atom and a lithium carboxylate structure in a functional group, and an organic solvent. A polymer electrolyte consisting of
Further, a polymer electrolyte in which a metal salt is added to the polymer electrolyte is constituted. In addition, the metal salt includes an alkali metal salt.

[0011] Lithium trifluoromethacrylate represented by the chemical formula (1) is used as a polymer repeating monomer,

Embedded image Here, m and n: arbitrary integers X: generic name of copolymerizable monomer units Constituting a polymer electrolyte which is a copolymer of a repeating monomer of the polymer of lithium trifluoromethacrylate and a copolymerizable monomer. .

The above problem is solved by using an organic solvent having at least one of an oxygen atom and a nitrogen atom in its structure, or a solvent obtained by mixing a plurality of these organic solvents.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention have replaced the methyl group of methacrylic acid with fluorine and further converted the carboxylic acid group into a lithium salt as lithium monomer trifluoromethacrylate as a monomer unit. We thought that the organic polymer, which is a copolymer, was promising as a material to solve the problem.

Conventionally, an organic polymer which is a copolymer of a monomer unit capable of copolymerizing with a lithium salt of methacrylic acid as a monomer unit has been developed. However, since the acidity of the carboxylic acid group is weak, lithium ions are not easily dissociated, which is insufficient as the high-ion conductive polymer electrolyte material of the present invention. It has been mainly used as a material for ion-exchange membranes and the like for capturing metal salts.

Therefore, in order to increase the acidity of the carboxylic acid group, trifluoromethacrylate in which the hydrogen atom of the methyl group of methacrylic acid is replaced by a fluorine atom having a high electronegativity is used. Thereby, the electron density on the oxygen atom of the carboxylic acid group is reduced by the introduced fluorine atom, and the lithium ion is easily dissociated. That is, the conductive carrier ions are dissociated by the swollen electrolytic solution, and conductivity is developed.
The lithium trifluoromethacrylate (hereinafter referred to as “T
(Abbreviated as "FMALi") as a monomer unit, and the use of an organic polymer, which is a copolymer of a monomer unit copolymerizable therewith, as a constituent material of a polymer electrolyte, has found that the object of the present invention can be achieved. .

That is, the present invention provides a polymer electrolyte comprising TFMALi as a monomer unit, an organic polymer which is a copolymer of a monomer unit copolymerizable therewith, and a solvent, Further, the present invention provides a polymer electrolyte characterized in that the above-mentioned polymer electrolyte contains an alkali metal salt in the same manner as a general-purpose gel electrolyte.

As X in the chemical formula (1), which is a monomer unit copolymerizable with TFMALi, a vinyl monomer unit can be appropriately used. As the vinyl monomer constituting such a vinyl monomer unit, one kind of monomer may be used, or two or more kinds of monomers may be used in combination. Specific examples of such vinyl monomers include, for example, CH ₂ ＣＨCHC
OOH, CH ₂ ＣＨCHCOOM (where M is a metal ion), CH ₂ ＣＨCHCOOR (where R is an alkyl group), CH ₂ ＣＨCHCOO (CH ₂ CH ₂ O) _n
CH ₃ (where n is an integer from 1 to 23), CH ₂ =
CHCOO (CH ₂ CH ₂ O) _n H (where n is 1-2)
3, an acrylic monomer such as glycidyl acrylate, and a methacrylic monomer which is a partially substituted product thereof, CH ₂ ＣC [COO (CH ₂ CH ₂ O)
_n CH ₃ ] ₂ (where n is an integer of 1 to 23), C
H ₂ ＣＨCH (C ₆ H ₅ ), CH ₂ ＣＨCH (CN), CH
_{2 = CH (OH), CH} 2 = CHCONH 2, can be preferably exemplified vinylpyrrolidone.

The organic polymer of the formula (1) contains one or more other monomer units in addition to TFMALi in order to control the physical and chemical properties of the organic polymer. In this case, as a method of controlling the physical properties and the chemical properties, the characteristics of each monomer unit may be expressed to a desired degree by changing the composition ratio of these monomer units.

For example, when a methacrylic monomer having a polyether skeleton as a side chain is contained as a monomer other than TFMALi, and the content of the methacrylic monomer is increased, the crystallinity of the organic polymer decreases. Conversely, the flexibility increases, and the mechanical strength when the organic solvent is swollen further increases. In addition, when a monomer having a hydroxyl group in a part of a side chain is contained, the hydroxyl group acts as a crosslinking site at the time of a crosslinking reaction, so that the higher the content of the monomer, the higher the degree of crosslinking and the stronger the crosslinking. The mechanical strength of the polymer electrolyte can be increased.

However, the proportion of the TFMALi monomer unit in the organic polymer represented by the chemical formula (1) is 10 mol%.
The content is more preferably 30 mol% or more. TFM
When the proportion of the ALi monomer unit is less than 5 mol%, the ionic conductivity is reduced. On the other hand, when the content is 90 mol% or more, the solubility (compatibility) with respect to the organic solvent is extremely reduced, and processing becomes difficult.

The TFMAL used in the present invention
In addition to using the i-type copolymer alone, a polymer blend obtained by blending with another polymer compatible with these can also be used. Examples of such other polymers include PEO and chemical formula (2)
Organic polymers which have been used in conventional polymer electrolytes, such as organic polymers represented by (4), polyacrylonitrile (PAN) and polymethyl methacrylate (PMMA);
Further, an organic polymer or the like can be used in which a similar polymer having a structure having a 5-membered cyclic carbonate group as a functional group or a linear or branched methylene bond via a chain carbonate group is used. The blending ratio can be appropriately selected according to the required physical properties and chemical properties, such as the required ionic conductivity and the flexibility of the film.

The metal salt constituting the polymer electrolyte in the present invention may be any of those conventionally used in polymer electrolytes. For example, lithium salts include LiBr,
LiI, LiSCN, LiBF ₄ , LiAsF ₆ , Li
ClO ₄ , LiCF ₃ SO ₃ , LiPF ₆ , LiN (C
_{F 3 SO 2) 2, LiC} (CF 3 SO 2) 3 and the like. In addition, anions of these lithium salts and alkali metal salts other than lithium salts, for example, salts of potassium, sodium and the like can also be used. In this case, a plurality of salts may be used simultaneously. In addition, it is also possible to use a metal salt different from the metal ion species in the trifluoromethacrylic acid metal salt of the polymer constituent unit,
When applied to a battery or the like, it is preferable to use the same metal ion species.

The ratio of the metal salt to the organic polymer constituting the polymer electrolyte varies depending on the type of the metal salt used, the type of the derivative of the organic polymer, and the like. It is preferable to be in the range of about 0.1 to 2.0 mol / l. If the ratio is too low, the ionic conductivity will decrease. If the ratio is too high, the ionic conductivity will decrease, and film deposition properties will decrease due to salt precipitation.

As the solvent constituting the polymer electrolyte in the present invention, those used in conventional polymer electrolytes can be used, and ethylene carbonate such as generally used as a lithium-based non-aqueous electrolyte is used. (EC), propylene carbonate (PC), butylene carbonate, dimethoxyethane (DME), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), dioxolan, γ-
Butyrolactone, sulfolane, dimethylformaldehyde (DMF), dimethylsulfoxide (DMSO), tetrahydrofuran (THF), and the like can be appropriately used, and a plurality of these organic solvents can be used at the same time.

The amount of swelling of the electrolytic solution comprising the metal salt and the organic solvent in the polymer electrolyte [electrolyte solution (g) / organic polymer (g) × 100] (w%) is determined by the type of the metal salt and the organic solvent used, Although the concentration differs depending on the type of the organic polymer used as the structural material, the ionic conductivity increases as the amount of swelling increases when a non-crosslinked polymer is used. The strength and the film properties (self-supporting property) are reduced, and the appearance of an adhesive body is exhibited. Furthermore, at 200 w% or more, it does not become a film,
It becomes a sticky gel. Therefore, it is possible to select a material according to the intended use according to the film properties and the ionic conductivity.
Incidentally, the higher the average molecular weight of the organic polymer, since the tendency of suppressing the decrease in film properties even when the content of the organic solvent is increased is seen, in the case of the polymer electrolyte containing the organic solvent of the present invention, The higher the average molecular weight of the polymer, the more effective.

On the other hand, when a crosslinked polymer is used,
The situation varies depending on the degree of crosslinking, but generally 1000 w%
Even if the swelling amount is increased to the extent, the mechanical strength is not extremely reduced, and a material having high ionic conductivity can be obtained.

The polymer having a crosslinked structure can be prepared by a conventional method. That is, techniques such as actinic radiation, light, electron beam, and heating are effective for a polymer obtained by copolymerizing a monomer unit capable of imparting a crosslinked structure. that time,
If necessary, a photopolymerization initiator such as trimethylsilylbenzophenone, benzoin and 2-methylbenzoin; a polymerization initiator such as benzoyl peroxide, methyl ethyl ketone peroxide and azoisobisbutyronitrile; and toluene-2,4-
It is also effective to add a crosslinking agent such as diisocyanate and 4,4'-diphenylmethane diisocyanate.

Generally, the solid polymer electrolyte of the present invention is used in the form of a film, and the film can be formed by a conventional method. The blending ratio of the organic solvent, the method and the order thereof are not particularly limited. For example, the complex is obtained by dissolving an organic polymer and a metal salt in an organic solvent, spreading this solution on a flat substrate, and evaporating the solvent. A film can be obtained by a casting method of obtaining a film. In this case, as the casting solvent, a solvent capable of dissolving both the polymer and the metal salt, for example, dimethylformamide (D
A moderately polar organic solvent such as MF) or tetrahydrofuran (THF) can be used as appropriate. At this time, without completely evaporating the solvent, a method of producing a state in which the solvent is left enough to maintain a solid film state,
There is a method of swelling the organic solvent and, further, the solution in which the metal salt is dissolved after complete removal, and any method may be used. In addition, it can manufacture similarly using water instead of these organic media. However, it is not appropriate when the polymer electrolyte of the present invention is used for a lithium battery or the like, and is limited to other uses.

[0029] Further, regarding the polymer solid electrolyte which has been subjected to the crosslinking reaction of the present invention, the method of compounding the organic solvent and the order thereof are not particularly limited. A method of preparing a polymer solid electrolyte by adding a mixture adjusted to the above concentration under a nitrogen atmosphere and performing a cross-linking reaction, and an organic electrolysis in which a metal salt is dissolved in an organic solvent in an organic polymer that has been cross-linked. There is a method of swelling the liquid to obtain a solid polymer electrolyte, and any method may be used.

Since the polymer solid electrolyte of the present invention uses a polymer having lithium trifluoromethacrylate in which the hydrogen of the methyl group of lithium methacrylate is substituted by fluorine, the acidity of the carboxylic acid group is increased, High ionic dissociation is caused by swelling the organic solvent. Therefore, it is possible to simultaneously realize high ion conductivity, film formability, flexibility, and mechanical strength. Further, by partially cross-linking the organic polymer, it is possible to increase the mechanical strength without lowering the ionic conductivity.

Hereinafter, the present invention will be specifically described based on embodiments.

Synthesis of TFMALi Copolymer 50 g of trifluoromethacrylic acid was added to chloroform 200
The mixture is dissolved in a 1 ml solution, and an equal amount of 1N LiOHaq is added to neutralize. This solution is concentrated and dried to obtain TFMALi.

Next, DMF was placed in a glass reaction vessel for sealing.
Weigh 100 ml. There, TFMALi, methoxypolyethylene glycol methacrylate having a polyether structure in a side chain [CH ₂ C (CH ₃ ) COO (C
H ₂ CH ₂ O) ₄ CH ₃ : PEM4], hydroxy acrylate having a hydroxyl group at the terminal [CH ₂ ＣC (C
H ₃ ) COOCH ₂ CH ₂ OH: HEMA], methyl methacrylate [CH ₂ ＣC (CH ₃ ) COOCH ₃ : MM
A], acrylonitrile [CH ₂ ＣＨCH (CN): A
N] according to a predetermined monomer composition ratio (mol%). Further, 0.4% by weight of azobisbutyronitrile (AIBN) is added to the total monomer weight. This reaction vessel was connected to a nitrogen purging apparatus, and the content was cooled and solidified in a dry ice-methanol bath, and then the operation of degassing, introducing nitrogen and dissolving under high vacuum was repeated three times, and finally sealed under high vacuum. .

The reaction vessel was placed in a shaking thermostat at 80 ° C. for 2 hours.
The polymerization reaction is performed for 4 hours. During this time, the viscosity of the polymerization system increases.
Thereafter, the mixture is cooled to room temperature, opened, and the reaction solution is poured into a 5-fold amount of methanol with stirring. This gives a white fibrous solid. After this is filtered, it is thoroughly washed with methanol. The obtained solid is purified by repeating the reprecipitation operation in a DMF-methanol system for two to three times.

As a result, the desired organic polymer was obtained with a yield of about 80%. This organic polymer is used for FT-IR and CDC
was identified by l ₃ in ¹ H-NMR, the copolymerization of the monomer and it was confirmed that according to the charging ratio of the synthesis.

It is relatively easy to control the average molecular weight of the organic polymer by the monomer concentration and the reaction time, and the average molecular weight of the organic polymer prepared under various conditions can be determined by gel permeation chromatography (gel permeation chromatography). GP
As a result of the measurement by C), it was about 1 × 10 ³ to 10 ⁶ .

Preparation of Polymer Solid Electrolyte Film The organic polymer obtained as described above is added to sufficiently dehydrated DMF, sufficiently stirred to form a uniform solution, and then passed through a filter having a pore size of 0.45 μm. The insoluble material was removed, and a film was formed by a casting method. That is, the solution is transferred to a petri dish made of Teflon having a smooth bottom, the solvent is evaporated in a constant temperature oven set at a temperature range of 40 to 60 ° C. under a nitrogen atmosphere, and the solvent is completely removed under vacuum heating. ,
After drying, a polymer electrolyte film was obtained.

This film-like polymer film is immersed in a solution of LiClO ₄ in an appropriate amount dissolved in propylene carbonate (PC) to swell the solution in the polymer film. After a lapse of a predetermined time, the polymer membrane was taken out of the solution, an excess solution was taken out, and a polymer electrolyte was obtained. At this time, the amount of the electrolyte to be swollen can be controlled by the time for immersion and the method of removing the excess solution.

Further, the polymer obtained as described above is added to a solution in which an appropriate amount of LiClO ₄ is dissolved in PC,
The polymer is dissolved uniformly while heating and stirring under a nitrogen atmosphere. This solution was transferred to a Teflon petri dish having a smooth bottom surface, and gradually cooled to obtain a polymer electrolyte.

The polymer electrolyte film thus obtained is a flexible, colorless or pale yellow film. The thickness of the film can be appropriately prepared according to the purpose, but the ionic conductivity is evaluated. It is 50-150
μm was used.

Preparation of Crosslinked Polymer Electrolyte Film A method for preparing a crosslinked polymer electrolyte film is to irradiate an electron beam having an acceleration voltage of 250 kV and an electron dose of 8 Mrad under an inert gas atmosphere to a polymer electrolyte film swollen with an electrolyte. Was obtained. When a terminal such as HEMA contains a monomer having a hydroxyl group, the reaction efficiency of crosslinking can be promoted by adding a diisocyanate-based crosslinking agent.

The crosslinked polymer electrolyte film thus obtained is a colorless or pale yellow film having high flexibility, and the film thickness can be appropriately prepared according to the purpose. 50 to 1 to evaluate
The thing of 50 μm was used.

Evaluation of ionic conductivity The ionic conductivity of the polymer electrolyte film obtained as described above was evaluated as follows. That is, the polymer electrolyte film is pressed against a platinum electrode or a lithium metal electrode and heated and stored at 90 ° C. for several hours so that the contact between the electrode and the film is sufficiently maintained. afterwards,
Ionic conductivity was analytically calculated from the semicircular arc obtained by the constant voltage complex impedance method. In addition, these measurements were performed after putting the evaluation cell in a temperature-variable type thermostat, and required about one hour at an arbitrary temperature to bring the cell into a steady state.

In this case, the electrodes of the plurality of semicircular arc components obtained were changed to platinum and lithium metal, and by changing the area of the electrodes, a resistance portion contributing to ionic conduction in the solid polymer electrolyte was assigned. At this time, the amplitude of the AC voltage used for the measurement was set to about 30 to 100 mV, and the AC frequency band was set to 10 ⁻² to 10 ⁷ Hz.

From the results of the examples described below, the polymer electrolyte film of the present invention has a higher ionic conductivity in the temperature region near room temperature than the conventional composite film of PEO or another organic polymer and an alkali metal salt. It was confirmed that the rate was remarkably high. In addition, the film-forming properties, mechanical strength and flexibility were sufficient.

Examples 1 to 18 Using a copolymer of TFMALi-PEM4, the ratio of TFMALi monomer units to all the constituent monomer units was 80% in Examples 1 to 6, and 5% in Examples 7 to 12.
0%, 20% in Examples 13 to 18, and each PC
A polymer electrolyte was prepared in which the addition amount of was changed, and the ionic conductivity at a temperature of 30 ° C. was measured. The result is shown in FIG.

As is apparent from FIG. 1, TF in the polymer
MALi unit ratio is 20% (Examples 13 to 18), 5
The ionic conductivity tends to increase as it increases to 0% (Examples 7 to 12) and 80% (Examples 1 to 6). Also, the conductivity tends to increase as the added weight of PC increases with respect to the weight of the polymer. However, when the added weight exceeds 2 times, the mechanical strength of the polymer film starts to decrease, and further exceeds 4 times. When it is 6 weight times, the film does not become a self-supporting film but becomes an adhesive.

Therefore, in a system in which PC is swelled in a copolymer of TFMALi-PEM4, the ionic conductivity increases as the number of PC to be swollen increases, but the film-forming property decreases with the increase. It is desirable that the amount of PC is not more than 4 times by weight. However, when the film forming property, that is, the mechanical strength of the polymer film is not a problem in use, it is better to use more PC to swell.

Examples 19 to 36 Using a copolymer of TFMALi-MMA, the ratio of TFMALi monomer units to all the constituent monomer units was 80% in Examples 19 to 24, and Examples 25 to 30 were used.
Was made 50%, and Examples 31 to 36 were made 20%, and a polymer electrolyte was prepared in which the added amount of each PC was changed.
The ionic conductivity at ℃ was measured. The result is shown in FIG.

As is apparent from FIG. 2, TF in the polymer
MALi unit ratio is 20% (Examples 31 to 36), 5
0% (Examples 25 to 30), 80% (Examples 19 to 2)
4), the ionic conductivity tends to increase as the value increases. In addition, the ionic conductivity tends to increase as the added weight of the PC increases with respect to the weight of the polymer. However, when the added weight exceeds 2 weight times, the mechanical strength of the polymer film starts to decrease, and further 4 weight times. If it exceeds, the film formability is significantly reduced,
When it is 6 times by weight, the film does not become a self-supporting film but becomes an adhesive.

Therefore, in a system in which PC is swelled in a copolymer of TFMALi-MMA, the ionic conductivity increases as the number of PC to be swollen increases, but the swelling of the film decreases with the accompanying decrease in film-forming properties. It is desirable that the amount of PC is not more than 4 times by weight. However, when the film forming property, that is, the mechanical strength of the polymer film is not a problem in use, it is better to use more PC to swell.

Examples 37 to 54 Using a copolymer of TFMALi-AN, the ratio of TFMALi monomer units to all the constituent monomer units was 80% in Examples 37 to 42, 50% in Examples 43 to 48, and 20-49% at 49-54
A polymer electrolyte was prepared in which the amount of C was changed, and the temperature was 30 ° C.
Was measured for ionic conductivity. The result is shown in FIG.
Shown in

As is apparent from FIG. 3, TF in the polymer
MALi unit ratio is 20% (Examples 49 to 54), 5
0% (Examples 43 to 48), 80% (Examples 37 to 4)
As the value increases to 2), the ionic conductivity tends to increase. Also, the conductivity tends to increase as the added weight of PC increases with respect to the weight of the polymer, but when the weight exceeds 2 times, the mechanical strength of the polymer film starts to decrease,
When the amount exceeds 4 times by weight, the film-forming property is remarkably deteriorated. When the amount exceeds 6 times by weight, the film does not become a self-supporting film but becomes an adhesive.

Therefore, in a system in which PC is swollen in a copolymer of TFMALi-AN, the ionic conductivity increases as the number of PC to be swollen increases. It is desirable that the amount of PC is not more than 4 times by weight. However, when the film forming property, that is, the mechanical strength of the polymer film is not a problem in use,
The more PC that swells, the better.

Examples 55-66 A copolymer of TFMALi-MMA was used, wherein the ratio of TFMALi monomer units to all constituent monomer units was 50% (Examples 55-60).
A copolymer of ALi-AN, in which the ratio of TFMALi monomer units to all constituent monomer units is 50% (Examples 61 to 66), was 1M-
A polymer electrolyte in which the added amount of LiClO ₄ / PC was changed was prepared, and the ionic conductivity at a temperature of 30 ° C. was measured. FIG. 4 shows the results.

As is apparent from FIG. 4, 1M-LiCl
The conductivity tends to increase as the amount of O ₄ / PC increases with respect to the weight of the polymer. However, when the amount exceeds 2 times, the mechanical strength of the polymer film starts to decrease. If the amount exceeds the above range, the film-forming property is remarkably reduced.
In addition, when compared with the above-described examples to which only PC was added, when 1M-LiClO ₄ / PC was added, ionic conductivity was slightly higher.

Therefore, the copolymer of TFMALi-MMA and the copolymer of TFMALi-AN were added to 1M-LiClO
_In the system in which ₄ / PC is swollen, as in the system in which only PC is swollen, the ionic conductivity increases as the amount of 1M-LiClO ₄ / PC to be swollen increases, but the film-forming property decreases accordingly. Therefore, 1M-LiClO ₄ to be swollen
It is desirable that the amount of / PC be 4 times by weight or less. However, when the film forming property, that is, the mechanical strength of the polymer film is not a problem in use, the swelling 1M-LiCl
The more O ₄ / PC, the better. However, 1M-LiClO ₄ /
The swelling of the electrolyte of the PC causes an increase in the number of carrier ions in the system, so that the ionic conductivity slightly increases. In particular, the lower the swelling amount, the more remarkable the phenomenon.

Examples 67 to 90 Using a TFMALi-HEMA copolymer, the ratio of TFMALi monomer units to all the constituent monomer units was 80% in Examples 67 to 74, and Examples 75 to 8 were used.
2 and 50% in Examples 83 to 90, each of which is a polymer cross-linked by electron beam irradiation using toluene diisocyanate as a cross-linking material.
A polymer electrolyte in which an electrolyte solution of iClO ₄ / PC was swollen was prepared, and the ionic conductivity at a temperature of 30 ° C. was measured. The result is shown in FIG.

As is apparent from FIG. 5, the swelling of 1M-Li
As the amount of the ClO ₄ / PC electrolyte increases, the ionic conductivity tends to increase. In this case, since a crosslinked structure was introduced into the polymer electrolyte, 10% by weight of 1M-LiCl
Even if the O ₄ / PC electrolyte is swollen, the film formability does not decrease. However, when the weight is 10 times or more, the mechanical strength against breakage or the like decreases.

The polymer electrolyte of the present invention uses a fluorine-containing polymer as a polymer or a polymer containing fluorine or phosphorus as a counter anion of an alkali metal salt (BF ₄ ⁻ , PF ₆ ⁻ ) and a solvent as a solvent. By using an organic solvent having a high boiling point or the like, it is possible to impart flame retardancy to a polymer electrolyte material which is originally flammable, thereby ensuring the safety and reliability of a high energy density battery. Therefore, application to a large battery for electric vehicles or power storage is also possible.

The organic polymer represented by the chemical formula (1) used in the present invention can be easily obtained by using, for example, a cationic polymerization method or a coordination polymerization method, and its copolymerization ratio can be controlled. It is easy to do.

[0062]

As is evident from the above description, according to the present invention, as compared with the conventional polymer electrolyte, high ion conductivity is exhibited even at around room temperature, and film forming property, flexibility, It is possible to obtain a polymer solid electrolyte having excellent mechanical strength.

[Brief description of the drawings]

FIG. 1 shows the ionic conductivity at 30 ° C. when PC is swollen in a polymer in which the ratio of the TFMALi-PEM4 copolymer is changed.

FIG. 2 shows the ionic conductivity at 30 ° C. when PC is swollen in a polymer in which the ratio of the TFMALi-MMA-based copolymer has been changed.

FIG. 3 shows ionic conductivity at 30 ° C. when PC is swollen in a polymer in which the ratio of a TFMALi-AN-based copolymer is changed.

FIG. 4 TFMALi-MMA system, TFMALi-A
1M-LiCl was added to the polymer having the N-based copolymer ratio changed.
Ionic conductivity at 30 ° C. when O ₄ / PC is swollen.

FIG. 5 shows the ionic conductivity at 30 ° C. when PC is swollen in a polymer in which the ratio of the TFMALi-HEMA copolymer has been changed.

[Explanation of symbols]

TFMALi: lithium trifluoromethacrylate,
PEM4: methoxy polyethylene glycol methacrylate, MMA: methyl methacrylate, AN: acrylonitrile, HEMA: hydroxy acrylate, PC: propylene carbonate

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08K 3/30 C08K 3/30 C08L 33/02 C08L 33/02 H01M 6/18 H01M 6/18 E 10/40 10/40 B

Claims (5)

[Claims] 1. A polymer electrolyte comprising a polymer repeating monomer containing a fluorine atom and a lithium carboxylate structure as a functional group, and an organic solvent. 2. A polymer electrolyte according to claim 1, wherein a metal salt is added to the polymer electrolyte according to claim 1. 3. A method according to claim 1, wherein lithium trifluoromethacrylate represented by the chemical formula (1) is used as a polymer repeating monomer. However, m and n are arbitrary integers X is a generic name of copolymerizable monomer units, which is a copolymer of a polymer repeating monomer of lithium trifluoromethacrylate and a copolymerizable monomer. The polymer electrolyte according to claim 1. 4. The polymer electrolyte according to claim 2, wherein the metal salt is an alkali metal salt. 5. The organic solvent having at least one of an oxygen atom and a nitrogen atom in its structure,
The polymer electrolyte according to claim 1, wherein the polymer electrolyte is a solvent obtained by mixing a plurality of these organic solvents.