JP2002279826A - Polymer electrolyte gel and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ion conductive polymer electrolyte gel which is useful as a material for an electrochemical device, and a manufacturing method of the same. SOLUTION: The polymer electrolyte gel is composed of a supporting electrolyte, an organic solvent, and a bridged polymer which is obtained by the ring- opening reaction of a polymer having not less than two epoxy groups in one molecule of which, epoxy rings are opened and bridged by using the supporting electrolyte as a catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polymer electrolyte gel having high ionic conductivity and a method for producing the same.

[0002]

2. Description of the Related Art In a lithium ion secondary battery, a capacitor, a capacitor, etc. using an electrolyte mainly composed of an organic solvent, in order to prevent fire due to liquid leakage or short circuit accident,
A strong casing for enclosing the electrolyte and preventing accidents due to impact became essential, and it was difficult to reduce the weight.

In order to remedy this drawback, it has been desired to solidify the electrolyte. As one measure for solidification, development of a polymer electrolyte gel has been promoted. In the early stage of development, JP-A-6-68906 and JP-A-7-4527
A gel (physical gel) formed by physical interaction between macromolecules, which is disclosed in, for example, Japanese Unexamined Patent Publication No. 1 (1999), has been mainly studied. However, since the physical gel is thermoreversible, there has been a major problem in heat resistance such that the gel is liquefied at a high temperature.

As a method for improving the heat resistance, it is effective to use a crosslinked polymer having a three-dimensional structure by covalent bonds. For example, JP-A-10-74526, JP-A-11-214038, JP-A-2000-
There are many reports such as 80138. However, these polymer electrolyte gels are not yet sufficient in terms of ionic conductivity and safety. In other words, previous reports include:
A gelation method is described in which a polymer or a low molecule having a plurality of vinyl groups is formed into a cross-linked polymer by radical polymerization by heating, but since a peroxide compound or an azo compound is used as a catalyst, the gelation method has been described. It is inevitable that unreacted catalyst and decomposition products of the catalyst remain in the polymer electrolyte gel. These residues change in the gel and contribute to reducing the ionic conductivity of the polyelectrolyte gel.

[0005] When an azo compound is used, nitrogen gas is generated at the time of decomposition, so that bubbles which are difficult to remove are generated in the gel and ion conductivity is reduced. In addition, the flow of ions is biased, and there is a risk of overheating. When a peroxide compound is used, there is a danger of explosion due to impact or friction during radical polymerization for gelling, so that careful handling is required. Permanent peroxide compounds remaining in the gel unreacted also pose a problem in product safety.

[0006] Even in the gelling method by forming a crosslinked polymer by the same radical polymerization, Japanese Patent Laid-Open No. 2000-80
In the case of a method of forming a crosslinked polymer by light irradiation using a photoinitiator such as benzyldimethyl ketal described in Japanese Patent No. 138 or the like, there is no danger of gas generation or explosion due to decomposition. Does not occur. However, when a gelling method by forming a crosslinked polymer by light irradiation is applied to a lithium ion secondary battery, a capacitor, or the like, disadvantages arise due to restrictions on a manufacturing process as described below.

In other words, in the gelling method by forming a crosslinked polymer by heating, it is possible to gel after injecting a precursor solution of a polymer electrolyte gel into a cell assembled in advance. When the gel is formed by such a method, the contact between the polymer electrolyte gel and the electrode becomes good, and the interface resistance is suppressed. However, in the gelation method by light irradiation, the cells cannot be irradiated with light, so that they cannot be gelled after injection. Inevitably, the gel prepared in advance is bonded to the electrode, but as a result, the interface resistance between the polymer electrolyte gel and the electrode increases, and the ionic conductivity decreases.

Further, the decrease in ionic conductivity due to the above-mentioned gelling method becomes more remarkable at a low temperature of 0 ° C. or less, and lithium ion secondary batteries and capacitors to which these methods are applied are used in cold regions. Can be difficult.

[0009]

As described above, in the method of gelation by radical polymerization by heating, impurities derived from the catalyst remaining in the polymer electrolyte gel adversely affect ionic conductivity and safety. I was Further, in the gelation method by radical polymerization by light irradiation, the magnitude of the interfacial resistance in the cell due to the restriction of light irradiation has reduced ionic conductivity. The present inventor has conducted intensive studies to overcome the drawbacks of such conventional polymer electrolyte gels, and as a result, a gel free of the drawbacks can be obtained by forming a crosslink of a specific polymer into a material with a specific catalyst. The inventors have found that the present invention has been achieved. An object of the present invention is to provide a polymer electrolyte gel having more excellent ion conductivity than a conventionally known polymer electrolyte gel, and a method for producing the gel.

[0010]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
Polymer having two or more epoxy groups in one molecule (hereinafter, referred to as
A cross-linked polymer (hereinafter referred to as an epoxy cross-linked polymer) formed by a ring-opening cross-linking reaction of an epoxy ring using a supporting electrolyte as a catalyst and a polymer electrolyte gel comprising the supporting electrolyte and an organic solvent Is achieved by

Further, the present invention provides a highly improved epoxy-containing polymer by polymerizing a monomer containing a vinyl group and an epoxy group in one molecule as an essential component and containing no metal ion other than lithium. Achieved.

In addition to this, the supporting electrolyte is Li
The object is more highly achieved by being an ionic compound containing BF ₄ and / or LiPF ₆ and the epoxy cross-linked polymer being 2 to 20% by weight based on the polymer electrolyte gel.

Further, such a polymer electrolyte gel is prepared by dissolving an epoxy group-containing polymer in a solution in which an epoxy group-containing polymer and a supporting electrolyte are dissolved in an organic solvent as an essential component, using the supporting electrolyte as a catalyst to open the epoxy ring. It is obtained by a production method characterized in that a cross-linking reaction is performed to form an epoxy cross-linked polymer.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The epoxy group-containing polymer referred to in the present application needs to contain two or more epoxy groups in one molecule, which means that the polymer has a polymer reaction called an epoxy ring opening bond. It means the necessary condition that a cross-linked polymer can be formed, and if it is two or more in one molecule, the number, the bonding position, and the type of the main chain of the polymer, etc. There is no particular limitation. The mixture is not limited to one type, and may be a mixture of two or more types of epoxy group-containing polymers.

Such an epoxy group-containing polymer is obtained by introducing an epoxy group into a polymer having a reactive functional group, such as an unsaturated hydrocarbon polymer, polyether, polyester, polyurethane, or vinyl polymer. Obtainable. For example, an epoxy group can be introduced into polybutadiene or polyisoprene having a double bond in the polymer by reacting the double bond with peracetic acid, and polyethylene oxide or polypropylene having a hydroxyl group in the polymer. An epoxy group can be introduced into an oxide or the like by adding epichlorohydrin to a hydroxyl group and dehydrochlorinating with sodium hydroxide.

In addition to the above-described method of introducing an epoxy group into an existing polymer, a method of directly synthesizing an epoxy group-containing polymer using vinyl polymerization can also be employed. In the vinyl polymerization, various vinyl monomers can be used as a copolymer component. Therefore, by changing the copolymer component, it is possible to easily cope with required characteristics, and a wide range of applications is suitable. Therefore, this case will be described below.

In order to use a vinyl polymer obtained by vinyl polymerization directly as an epoxy group-containing polymer,
It is essential that the vinyl polymer is a homopolymer of a monomer containing a vinyl group and an epoxy group, or a copolymer containing the monomer as one of the copolymerization components. Examples of monomers containing a vinyl group and an epoxy group include glycidyl methacrylate, glycidyl acrylate, 2-methylglycidyl acrylate, 1,2-epoxy-3-butene, isoprene oxide, 1,2-epoxy-2-methyl -3-butene, 1,2-epoxy-5-hexene, 3
-Ethenyl-7-oxabicyclo [4,1,0] heptane, allyl glycidyl ether, [(2-propenyloxy) methyl] oxirane and the like.

The other monomer to be copolymerized with the monomer containing a vinyl group and an epoxy group is not particularly limited as long as it is a vinyl monomer. Also, it is not limited to one type,
Two or more vinyl monomers may be used. Examples of such vinyl monomers include acrylonitrile,
Examples include methacrylonitrile, acrylates, methacrylates, and vinyl ethers.
These vinyl monomers to be copolymerized are appropriately selected in consideration of the type of the organic solvent used for the polymer electrolyte gel and the properties required for the target polymer electrolyte gel.

The ratio of the monomer containing a vinyl group and an epoxy group to the other monomer to be copolymerized in the vinyl polymer should be determined in consideration of hardness and other characteristics required for the polymer electrolyte gel. Usually, the molar ratio of the monomer containing a vinyl group and an epoxy group / the other vinyl monomer to be copolymerized is 5/95 to 100/0, preferably 20/80 to 85/15. When the ratio of the monomer containing a vinyl group and an epoxy group in the vinyl polymer is less than 5 mol%, the formation of an epoxy cross-linked polymer by a ring-opening cross-linking reaction between epoxy groups to develop a subsequent gelled state. It may be difficult to proceed efficiently.
When the ratio is 100 mol%, that is, when alone, the formation of the epoxy cross-linked polymer proceeds efficiently, but the cross-linking becomes dense, so that the amount of the organic solvent that can be retained is reduced. Incidentally, the molecular weight of the vinyl polymer is not particularly important since it eventually becomes a crosslinked body, and may be any degree as long as it can be dissolved in an organic solvent / supporting electrolyte system, and is generally about 1,000 to 1,000,000 in number average molecular weight. It is.

In preparing such a vinyl polymer, it is important to carry out polymerization so that the epoxy group is not reacted and metal ions other than lithium do not enter. As such a polymerization method, a radical polymerization method is generally used. In the case of ionic polymerization, the epoxy group undergoes a ring-opening bond reaction during the polymerization, so that the resulting polymer cannot be crosslinked and gelled in a subsequent step, or on the contrary, it is crosslinked during the polymerization. And the resulting polymer may be insoluble in organic solvents. Even in the case of synthesis by radical polymerization, the selection of the polymerization catalyst is important because the electrochemical characteristics of the polymer electrolyte gel may be reduced depending on the type of the polymerization catalyst.

For example, in redox polymerization using sodium sulfite and sodium persulfate, sodium sulfonate derived from a polymerization catalyst radical is formed as a polymer terminal group, resulting in a large amount of sodium ions in the polymer. When used as a polymer electrolyte gel for lithium ion secondary batteries, metal ion impurities such as alkali metal ions and alkaline earth metal ions other than lithium ions increase the interface resistance,
It is desirable to reduce such sodium ions as much as possible.

When redox polymerization as described above must be employed, there is a method of washing with a strongly acidic aqueous solution in order to remove metal ion impurities taken into the polymer. It is not an efficient method. Therefore, in order to prevent the above-mentioned polymer from containing metal ions other than lithium, it is desirable to minimize the use of such a polymerization catalyst or to avoid its use. From such a viewpoint, in synthesizing the vinyl polymer, industrially, a polymerization catalyst that does not generate a metal ion such as an organic peroxide compound or an azo compound, ultraviolet irradiation, or electron beam irradiation is used. It is recommended to polymerize.

In the present invention, the fact that the epoxy group-containing polymer does not contain a metal ion other than lithium does not mean that the impurity metal ion is “absolutely null”. That is, even the organic solvent used in the solution polymerization method recommended by the present invention as a useful method for producing an epoxy group-containing polymer described later is described in L. et al. B. At present, impurity metal ions are not absolutely absent even in grades. Therefore, in the polymer electrolyte gel which is the final product of the present invention, the amount of impurity metal ions derived from the epoxy group-containing polymer does not exceed the amount of impurity metal ions derived from the coexisting supporting electrolyte or organic solvent. Absent"
Treat.

In the solution polymerization method recommended by the present invention, L.
B. A radical polymerization catalyst that does not generate metal ions in a graded organic solvent, a monomer containing a vinyl group and an epoxy group, and optionally a vinyl monomer to be copolymerized, in some cases, are generally in a weight ratio of the organic solvent 6, the polymerization catalyst 0.1.
2. A solution in which the monomer 4 is dissolved is prepared, and a polymer solution in which a vinyl polymer which is an epoxy group-containing polymer is dissolved by heating or light irradiation. Since the obtained polymer solution can be used as it is as a precursor of the polymer electrolyte gel, there is no need to purify the polymer to remove impurities or to further dry and dissolve it, thus simplifying the process. It is advantageous for industrial production.

The vinyl polymer which is an epoxy group-containing polymer described above is an epoxy cross-linked polymer in which the epoxy ring contained in the polymer is a ring-opening cross-linking reaction in the polymer electrolyte gel of the present invention, and the entire system is formed. Although it is in a gel state, the ratio of the epoxy cross-linked polymer to the polymer electrolyte gel is 2 to 20% by weight, preferably 2 to 10% by weight. If the proportion is less than 2% by weight, it may be difficult to form a gel, and if it exceeds 20% by weight, the ion conductivity may be significantly reduced in some cases. In addition, when the epoxy ring contained in the epoxy group-containing polymer undergoes a ring-opening cross-linking reaction, by-products are not eliminated or another molecule is not added. The ratio to the electrolyte gel is equal to the ratio of the epoxy group-containing polymer to the solution before the ring-opening crosslinking reaction.

Next, as the supporting electrolyte employed in the present invention, LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆
Inorganic compounds such as LiSO ₃ CF ₃ , LiN (SO ₂ C
F ₃ ) ₂ , lithium fluoride such as LiC (SO ₂ CF ₃ ) ₃ , tetraethylammonium tetrafluoroborate, tetraethylammonium hexafluorophosphate, monomethyltriethylammonium tetrafluoroborate, monomethyltriethylammonium hexafluorophosphate Acid salts and the like that dissolve in an organic solvent are preferably used, and particularly preferred are LiBF ₄ , Li
PF ₆ or a combination thereof.

The organic solvent used in the present invention means a solvent having a water content of 0.1% by weight or less and capable of dissolving an epoxy group-containing polymer and a supporting electrolyte. As a solvent, ethylene carbonate (abbreviation E
C), carbonates such as propylene carbonate (abbreviation PC), butylene carbonate (abbreviation BC), diethyl carbonate (abbreviation DEC), dimethyl carbonate (abbreviation DMC), ethyl methyl carbonate (abbreviation EMC), ethylene glycol, propylene glycol, and methyl In addition to ether compounds such as cellosolve and ethyl cellosolve, a single solvent or a mixture of two or more solvents such as gamma-butyrolactone (GBL), sulfolane, dimethyl sulfoxide, adiponitrile, glutaronitrile, N-methylpyrrolidone, and trimethyl phosphate are recommended. .

As for these organic solvents, those having a high boiling point are preferable as long as the dissolving ability of the epoxy group-containing polymer and the supporting electrolyte is excellent. Organic solvents having a boiling point of 90 ° C. or less are liable to evaporate, and are liable to cause problems due to their high vapor pressure.

The epoxy cross-linked polymer obtained by the ring-opening cross-linking reaction of the epoxy group-containing polymer described above, the supporting electrolyte and the organic solvent are essential components of the polymer electrolyte gel referred to in the present application. A polymer compound that does not form a crosslink or a conductive additive may be added.

The proportion of each of these components in the polymer electrolyte gel should be determined in consideration of the target electrochemical properties and physical properties. Suitably, it is 2 to 20% by weight, the supporting electrolyte is 1 to 30% by weight, and the balance is an organic solvent and other components.

The polymer electrolyte gel of the present invention is obtained by reacting the epoxy group-containing polymer in a solution in which an epoxy group-containing polymer and a supporting electrolyte are dissolved in an organic solvent as essential components, using the supporting electrolyte as a catalyst. It can be obtained by ring-opening and cross-linking epoxy groups to form an epoxy-crosslinked polymer, and crosslinking and gelling the solution. As described above, in preparing the solution, a polymer compound that does not form crosslinks, a conductive additive, and the like may be added as other components. In addition, it is important that these manufacturing steps are performed in a state where the outside air is shut off or in a dry atmosphere having a dew point of −50 ° C. or less in order to prevent an increase in the moisture content due to moisture absorption.

The solution is changed from a solution state to a gel state (gelation) as described above because a cross-linked structure is formed by a ring-opening cross-linking reaction between epoxy groups of the epoxy group-containing polymer (cross-linked gel). ). As a usual catalyst for this kind of cross-linking gelation reaction, a tertiary amine, Lewis acid, protonic acid, or the like can be used. However, in this case, after cross-linking and gelation, all of these catalysts remain in the gel as impurities, preventing the movement of ions and increasing the interfacial resistance. It cannot be adopted because it causes a decrease. Therefore, in the present invention,
It is recommended to use a supporting electrolyte as a catalyst in this reaction, especially the use of LiBF ₄ and LiPF ₆ . The present invention using a supporting electrolyte as a catalyst enables cross-linking and gelation without leaving any impurities in the gel, and overcomes the above-mentioned problems, which is very preferable.

The method of preparing the solution in which the essential components are dissolved is not particularly limited, but the supporting electrolyte also functions as a cross-linking gelation catalyst, and therefore it is more preferable to mix the supporting electrolyte last. For example, a method of dissolving a supporting electrolyte in a polymer solution in which an epoxy group-containing polymer is dissolved in an organic solvent, a method of adding an organic solvent in which a supporting electrolyte is dissolved in advance to the polymer solution, and the like are given.

The polymer solution in which the epoxy group-containing polymer is dissolved in the organic solvent used herein may be a solution obtained by dissolving an epoxy group-containing polymer obtained in advance by polymerization in an organic solvent, or an organic solvent. It may be a solution of an epoxy group-containing polymer prepared by a solution polymerization method in which a monomer is reacted in a solvent. Industrially, the latter is particularly recommended because the production efficiency is high and a homogeneous polymer solution can be easily obtained because the latter can omit the steps of removing and purifying the polymer from the polymerization system and purifying or drying and dissolving it. Is the way. However, the catalyst used in the formation of the epoxy group-containing polymer should be carefully considered so as not to remain as impurities as much as possible or to prevent metal ions other than lithium ions from entering. In some cases, it is also preferable to subject the polymer solution by the solution polymerization method to a treatment for removing catalyst residues.

The epoxy ring-opening and cross-linking reaction of the present invention is carried out by an epoxy group-containing polymer mixed and dissolved by the above-described method,
The process proceeds by directly heating the solution of the organic solvent and the supporting electrolyte, and the desired polymer electrolyte gel is obtained. Most of the conditions include a means for maintaining the temperature at 50 to 70 ° C. for 0.5 to 3 hours. As a supporting electrolyte, that is, a catalyst, LiBF ₄ or LiPF ₆ has a high catalytic ability and a fast reaction.
Depending on the type of supporting electrolyte, a high temperature and a long time are required for the development of cross-linked gelation, but a small amount of LiBF ₄ or LiP
This reaction can be promoted by adding F ₆ . Also, the epoxy ring is highly reactive, and in this ring-opening cross-linking reaction, almost all of the epoxy rings present in the epoxy group-containing polymer will react, but due to steric hindrance, some epoxy rings must be cross-linked. Conceivable.

The excellent features of the present invention described in detail above are as follows.
By selecting an epoxy group-containing polymer as a starting material, a polymer electrolyte gel can be obtained substantially without a catalyst. Since cross-linking gelation can be performed without a catalyst, azo compounds and peroxide compounds that have been widely used as gelling catalysts so far are unnecessary, and decomposition products of catalysts and unreacted catalysts are contained in the formed gel. Does not remain. Although a procedure is particularly required, a gel containing no impurities is possible if the epoxy group-containing polymer itself is used after purification. That is, the polymer electrolyte gel of the present invention is a gel with reduced impurities, and therefore exhibits excellent ionic conductivity.

[0037]

EXAMPLES Hereinafter, the present invention will be described in more detail by way of representative examples and comparative examples, but the present invention is not limited to these examples. The parts described in the following examples are parts by weight unless otherwise specified, and% is percent by weight. From the electrolyte gel obtained in the examples, the following cells were prepared, and the electrochemical characteristics of the cells were evaluated.

[Method of Making Electrochemical Characteristics Evaluation Cell] A flat plate-like lithium foil (electrode) having a thickness of 0.2 mm is placed on the bottom of a stainless steel petri dish, and a 0.2 mm-thick lithium foil is placed thereon.
A Teflon (registered trademark) square spacer is set, and a solution prepared by previously mixing the epoxy group-containing polymer solution prepared in the following Examples and Comparative Examples with the supporting electrolyte solution. Put an appropriate amount, 0.2m thick on this
After placing a petri dish with a lithium foil (electrode) with a thickness of m and placing no gap between the spacer and the lithium foil, heating at 60 ° C for 1 hour to allow ring-opening and crosslinking reaction between epoxy groups. Crosslinked gelation with a thickness of 20
A gel film of a 0 μm polymer electrolyte gel was prepared. The gel film sandwiched between the lithium foils is sandwiched by a nickel plate having a thickness of 0.3 mm with a lead wire, inserted between two glass plates, fixed with clips, and used for a cell for evaluating electrochemical characteristics. It was created.

[Evaluation of Electrochemical Characteristics] The above-mentioned cell for evaluating electrochemical characteristics was connected to an AC impedance measuring device (1286 + 1250, manufactured by Solartone) and the temperature was changed to 25 ° C.
Then, the AC impedance from 100 kHz to 1 Hz was measured, and the impedances at the measurement frequencies of 100 kHz and 100 Hz were defined as the bulk resistance value and the interface resistance value, respectively. The ionic conductivity was calculated from the bulk resistance value and the thickness and area of the cell.

The above AC impedance measurement was performed at 25 ° C. for 2 hours.
After continuing for 4 hours, the evaluation cell was connected to an electrochemical measurement device (S1-1280B manufactured by Solartone), and
Inversion voltage ± 0.5V at 5 ° C, potential sweep speed 10mV / s
Was subjected to polarization electrolysis by cyclic voltammetry, and the polarization current value at +0.5 V in the third cycle was measured, and this was defined as the polarization current value with respect to the lithium negative electrode CV. Hereinafter, the polarization current value of the lithium negative electrode CV is simply referred to as a polarization current.

After the measurement of the polarization current, the AC impedance was measured again, and the interface resistance 24 hours after the cell was prepared. From these measurement results, the ratio between the interface resistance immediately after the start of the measurement and the interface resistance after 24 hours was determined.
The rate of increase of the interface resistance value was used. The preparation of the gel film, the preparation of the cells, and the evaluation of the characteristics were performed using a glove box in an argon gas atmosphere at a dew point of -50 ° C.

Comparative Example 1 0.22 g of sodium hydroxide
Was dissolved in 20 g of water, and 10 g of polyethylene glycol monomethyl ether (number average molecular weight 2000) was added to an aqueous solution in which 20 g of water was dissolved.
Was added. This was heated to 45 ° C., and 0.46 g of epichlorohydrin was rapidly added with vigorous stirring, heated to 95 ° C., and continued to be stirred for 80 minutes. The resulting solution is extracted with benzene, and the terminal hydroxyl group of polyethylene glycol monomethyl ether is substituted and modified with a glycidyl group from the extract by freeze-drying to obtain a single epoxy group containing one epoxy group in one molecule. The molecule was obtained.

4 g of the above polymer was dissolved in 6 g of a mixed solvent obtained by mixing ethylene carbonate (EC) and propylene carbonate (PC) at a volume ratio of 2/1 to obtain a single epoxy group-containing polymer solution. Separately, a supporting electrolyte solution was prepared by dissolving 0.78 g of LiBF ₄ in 9.22 g of the above mixed solvent. 1. The single epoxy group-containing polymer solution
Using 0 g of the supporting electrolyte solution and 8.0 g of the supporting electrolyte solution, an attempt was made to form a gel membrane in accordance with the above-mentioned method, but no gelation was possible.

<Example 1> 10 g of polyethylene glycol (number average molecular weight 1000) was added to an aqueous solution in which 0.9 g of sodium hydroxide was dissolved in 20 g of water. This is 4
Heat to 5 ° C., add 1.85 g of epichlorohydrin rapidly with vigorous stirring, warm to 95 ° C.
Stirring was continued for 0 minutes. The obtained solution is extracted with benzene, and an epoxy group-containing polymer having two epoxy groups in one molecule in which the hydroxyl groups at both ends of polyethylene glycol are substituted and modified with glycidyl groups is extracted from the extract by freeze-drying. Obtained. Using 2.0 g of the epoxy group-containing polymer solution prepared in the same manner as in Comparative Example 1 using this polymer and 8.0 g of the same supporting electrolyte solution as in Comparative Example 1, the cell was prepared according to the method described above. Was prepared and measured.

Example 2 6.0 g of the mixed solvent of Comparative Example 1
Bisphenol A-epichlorohydrin copolymer having glycidyl groups at both ends (Poly (Bisphenol A-co-epichl
orohydrin), gly-cidyl end-capped, number average molecular weight 10
75) 4.0 g was dissolved to obtain an epoxy group-containing polymer solution. Using 2.0 g of this solution and 8.0 g of the same supporting electrolyte solution as in Comparative Example 1, a cell was prepared according to the method described above, and measurement was performed.

Example 3 6 g of the same mixed solvent as in Comparative Example 1
2.0 g of acrylonitrile (hereinafter abbreviated as AN),
0.4 g of vinyl acetate (hereinafter abbreviated as VAc), 1.6 g of glycidyl methacrylate (hereinafter abbreviated as GMA),
Benzyldimethyl ketal (hereinafter referred to as BDK)
0.2 g) and dissolved. This is 360
nm has a peak wavelength, and the illuminance at this wavelength is 10
After irradiation with ultraviolet light of mW / cm ² for 10 minutes to polymerize,
At 50 ° C., the mixture was placed in a reduced pressure container having a gauge pressure of −0.09 MPa to remove unreacted monomers to prepare a polymer solution of an epoxy group-containing polymer. Using 2.0 g of the epoxy group-containing polymer solution and 8.0 g of the supporting electrolyte solution of Comparative Example 1, a cell was prepared according to the method described above, and measurement was performed.

Example 4 A cell was prepared and measured in the same manner as in Example 3 except that allyl glycidyl ether was used instead of GMA.

Example 5 Water 8 was placed in a 2 liter flask.
00 ml, into which 50 g of AN, 10 g of VAc,
A mixed solution of 40 g of GMA and a solution in which 0.6 g of sodium pyrosulfite and 0.2 g of ammonium persulfate were dissolved in 120 ml of water each as a polymerization catalyst were continuously supplied over 2 hours. After the completion of the supply, the polymerization was further continued at 65 ° C. for 2 hours. After the polymerization-finished flask was cooled to room temperature with water, the content was filtered and washed three times to remove unreacted monomers and polymerization catalyst residues, and the obtained epoxy group-containing polymer was dried at 70 ° C. in a vacuum dryer. At 1
It was dried at night to remove water. In addition, a sulfone group derived from a polymerization catalyst was introduced into this polymer, and ion exchange was not performed. Therefore, the sulfone group formed a salt with sodium.

Using the obtained epoxy group-containing polymer, an epoxy group-containing polymer solution was prepared in the same manner as in Comparative Example 1, and 2.0 g of this solution and 8.0 g of the same supporting electrolyte solution as in Comparative Example 1 were used. A cell was prepared and measured according to the method described above.

Example 6 EC and diethyl carbonate
(DEC) in a mixed solvent of 6 g mixed in 1/3 by volume ratio
AN 1.0 g, stearyl methacrylate (hereinafter SMA)
0.8 g, GMA 2.2 g, polymerization catalyst
After adding and dissolving 0.2 g of BDK, the same as in Example 3 was performed.
UV polymerization and removal of unreacted monomers
A polymer solution of a polymer having a di-group was prepared. Aside from this
LiPF was added to 8.6 g of the above mixed solvent. ₆Is dissolved in 1.4 g
A supporting electrolyte solution was prepared. The epoxy group-containing polymer
Using 2.0 g of the solution and 8.0 g of the supporting electrolyte solution,
Change the heating conditions to 70 ° C for 18 hours in the method described above.
A cell was created and measurements were made.

Example 7 2.0 g of the epoxy group-containing polymer solution of Example _{3 and} 8.0 g of a supporting electrolyte solution obtained by dissolving 1.25 g of LiSO ₃ CF _{3 in} 8.75 g of the mixed solvent of Comparative Example 1 were used. In the mixed solution, 0.02 g of LiBF ₄ was dissolved as a supporting electrolyte for promoting crosslinking gelation. Using this solution, a cell was prepared and measured according to the method described above.

Comparative Example 2 2.0 g of the epoxy group-containing polymer solution of Example _{3 and} 8.0 g of a supporting electrolyte solution obtained by dissolving 1.25 g of LiSO ₃ CF _{3 in} 8.75 g of the mixed solvent of Comparative Example 1 were used. In the mixed solution, 0.02 g of tin tetrachloride, one of Lewis acids, which is a ring-opening catalyst that is much stronger than the electrolyte LiSO ₃ CF ₃ as a cross-linking gelation catalyst, was dissolved. Using this solution, a cell is prepared according to the method described above,
A measurement was made.

<Comparative Example 3> Mixed solvent 6 similar to Comparative Example 1
After adding and dissolving 2.84 g of AN, 1.16 g of VAc, and 0.2 g of BDK as a polymerization catalyst, UV polymerization and removal of unreacted monomers were carried out in the same manner as in Example 3 to obtain AN.
/ VAc copolymer solution was prepared. Separately, a crosslinkable monomer solution was prepared by dissolving 4.0 g of a polyoxyethylene dimethacrylate having a polymerization degree of 14, which is a crosslinkable monomer, in 6.0 g of the above mixed solvent. A solution prepared by mixing and dissolving 1.0 g of the AN / VAc copolymer solution, 1.0 g of the crosslinking monomer solution, 8.0 g of the supporting electrolyte solution of Comparative Example 1, and 0.04 g of azobisisobutyronitrile was used. A cell was prepared by changing the heating conditions to 70 ° C. for 5 hours in the above-described method, and measurement was performed. Note that the gel film produced by this method contained many bubbles.

Table 1 shows the measurement results of the ionic conductivity, the interface resistance increase rate, and the polarization current of Examples 1 to 7 and Comparative Examples 1 to 3. The amount of the epoxy crosslinked polymer was 8.0% in each gel. As shown in Table 1, Examples 1 to 7, which are the polymer electrolyte gel of the present invention, showed excellent electrochemical properties. As the epoxy group-containing polymer, if there are two or more epoxy groups in one molecule, not only the vinyl polymer represented by Examples 3 and 4, but also the polyether of Example 1 and the polymer such as Example 2 And the like, and the type of the organic solvent (Examples 3 and 6) and the type of the supporting electrolyte (Examples 3, 6, and 7) can also be selected. However, when a metal ion other than lithium is contained in the epoxy group-containing polymer as in the fifth embodiment, the properties are slightly lower than those of the other embodiments, although they are superior to the related art.

In comparison with the polymer electrolyte gel of the present invention, in Comparative Example 1, a single epoxy group-containing polymer was used, and there was only one epoxy group per molecule, and the epoxy ring caused a ring opening reaction. Does not gel because only linear polymers are formed. In Comparative Example 2, the presence of a large amount of metal ions derived from tin tetrachloride which acted preferentially on LISO ₃ CF ₃ was present, while Comparative Example 3 did not rely on the ring-opening cross-linking reaction using the epoxy ring supporting electrolyte as a catalyst. Although a crosslinked gel is formed, the presence of non-removable bubbles generated in the gel by the decomposition gas of azobisisobutyronitrile lowers the electrochemical characteristics.

[0056]

[Table 1]

Example 8 0.5 g of the epoxy group-containing polymer solution of Example 3 and 9.3 g of the mixed solvent of Comparative Example 1 were mixed with L.
Using 9.5 g of a supporting electrolyte solution in which 0.7 g of iBF ₄ was dissolved, a cell was prepared according to the above-described method, and measurement was performed.

Example 9 3.5 g of the epoxy group-containing polymer solution of Example 3 and 9.1 g of the mixed solvent of Comparative Example 1 were mixed with L.
Using 6.5 g of a supporting electrolyte solution in which 0.9 g of iBF ₄ was dissolved, a cell was prepared according to the method described above, and measurement was performed.

<Example 10> 5.0 g of the epoxy group-containing polymer solution of Example 3 and 8.91 g of the mixed solvent of Comparative Example 1 were used.
4.10 g LiBF ₄ dissolved in a supporting electrolyte solution
Using 0 g, a cell was prepared and measured according to the method described above.

Table 2 shows the measurement results of the concentration of the epoxy cross-linked polymer, the ionic conductivity, the increase in the interface resistance, and the polarization current of the gel films and cells of Examples 3 and 8 to 10. The polymer electrolyte gel of the present invention has an epoxy crosslinked polymer concentration of 2.0 to 2
At 0.0% by weight, it was demonstrated that all exhibited excellent properties. A closer look shows that the lower the epoxy cross-linked polymer concentration, the better the properties are. This is thought to be because the smaller the epoxy cross-linked polymer, the easier the ions to move. However, if the epoxy cross-linked polymer concentration is too low, it may not be possible to form a gel.

[0061]

[Table 2]

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The polymer electrolyte gel of the present invention exhibits excellent ionic conductivity not only at room temperature but also at low temperature, and is very suitable for electrochemical devices such as lithium polymer secondary batteries and electric double layer capacitors. It is useful and can be expected to have excellent electrochemical properties.

Claims (5)

[Claims] 1. A crosslinked polymer (hereinafter, referred to as an epoxy group-containing polymer) formed by a ring-opening crosslinking reaction of an epoxy ring using a supporting electrolyte as a catalyst. , An epoxy-crosslinked polymer), and a supporting electrolyte and an organic solvent. 2. The polymer according to claim 1, wherein the polymer containing an epoxy group is polymerized with a monomer containing a vinyl group and an epoxy group in one molecule as an essential component, and contains no metal ion other than lithium. Electrolyte gel. 3. The polymer electrolyte gel according to claim 1, wherein the supporting electrolyte is an ionic compound containing LiBF ₄ and / or LiPF ₆ . 4. The polymer electrolyte gel according to claim 1, wherein the epoxy crosslinked polymer accounts for 2 to 20% by weight based on the polymer electrolyte gel. 5. The epoxy group-containing polymer in a solution in which an epoxy group-containing polymer and a supporting electrolyte are dissolved in an organic solvent as essential components is subjected to a ring-opening crosslinking reaction of an epoxy ring using the supporting electrolyte as a catalyst. The method for producing a polymer electrolyte gel according to any one of claims 1 to 4, wherein a crosslinked polymer is formed.