WO2002075748A1

WO2002075748A1 - Polymer electrolyte gel and method for preparation thereof

Info

Publication number: WO2002075748A1
Application number: PCT/JP2002/002335
Authority: WO
Inventors: Koji Tanaka
Original assignee: Toyo Boseki Kabushiki Kaisha
Priority date: 2001-03-19
Filing date: 2002-03-13
Publication date: 2002-09-26
Also published as: JP2002279826A; TW540175B

Abstract

A polymer electrolyte gel which comprises a crosslinked polymer formed through the ring-opening and crosslinking of a polymer having two or more epoxy groups in a molecule by the use of a supporting electrolyte as a catalyst, the supporting electrolyte and an organic solvent; and a method for preparing the polymer electrolyte gel. In the case of a lithium secondary cell or the like using a liquid electrolyte such as an organic solvent, it is difficult to prepare a satisfactorily lightweight cell, since the sealing of the electrolyte or the like is required for preventing the leakage of a liquid. A polymer electrolyte gel has been developed for overcoming the above defect through solidification of an electrolyte. However, the gelation by heating combined with the use of a catalyst results in the adverse effect on the conductivity of an ion due to impurities derived from the residual catalyst in the resulting polymer electrolyte gel, and the gelation by irradiation of a light needs the lamination of the resulting gel with an electrode, which leads to the reduction of the conductivity of an ion due to the interfacial resistance between electrolyte and electrode layers. The polymer electrolyte gel is free from the problems associated with above conventional polymer electrolyte gels, and thus exhibits enhanced ion conductivity.

Description

Description Polymer electrolyte gel and method for producing the same

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

For lithium ion secondary batteries, capacitors, capacitors, etc., which use electrolytes mainly composed of organic solvents, in order to prevent fires due to liquid leakage or short circuit accidents, the electrolyte is sealed or solid to prevent accidents due to impact. A simple casing was required, making it difficult to reduce the weight.

In order to improve this disadvantage, it is desired to solidify the electrolyte. As one measure for solidification, the development of polymer electrolyte gels is underway. In the early stage of development, gels formed by physical interaction between high molecules (physical gels) disclosed in Japanese Patent Application Laid-Open No. 6-68906, Japanese Patent Application Laid-Open No. 7-45271, etc. ) Was mainly considered. However, since physical gels are thermoreversible, gels liquefy at high temperatures, and there was a major problem with heat resistance.

As a method for improving the heat resistance, it is effective to use a crosslinked polymer having a three-dimensional structure by a covalent bond. For example, there are many reports such as Japanese Patent Application Laid-Open No. H10-74526, Japanese Patent Application Laid-open No. H11-21038, Japanese Patent Application Laid-Open No. 2000-080038, and the like. ing. However, these polymer electrolyte gels are not yet sufficient in terms of ionic conductivity and safety. That is, the previous reports describe a gelation method in which a polymer or low molecule having a plurality of vinyl groups is converted into a crosslinked polymer by radical polymerization by heating, but a peroxide compound is used as a catalyst. Since a diazo compound is used, it is inevitable that unreacted catalyst and decomposition products of the catalyst remain in the generated polymer electrolyte gel. These residues change in the gel and contribute to lowering the ion conductivity of the polyelectrolyte gel. When a azo compound is used, nitrogen gas is generated at the time of decomposition, so that bubbles that 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 peroxide compounds are used, there is a risk of explosion due to shock or friction during radical polymerization for gelling, and special care must be taken when handling. Peroxide compounds that remain in the gel unreacted also pose a problem in product safety.

Even in a gelation method by forming a crosslinked polymer by the same radical polymerization, a photoinitiator such as benzyl dimethyl ketal described in JP-A-2000-18038 is used. In the case of the method used for forming a crosslinked polymer by light irradiation, there is no danger of gas generation or explosion due to decomposition, so the above-mentioned problem 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.

That is, in the gelling method by forming a crosslinked polymer by heating, it is possible to gel after injecting a precursor solution of the 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 is improved, 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.

In addition, the decrease in ion conductivity caused by the above-mentioned gelation method becomes more remarkable at low temperatures of 0 ° C or less, and lithium ion secondary batteries and capacitors using these methods are not suitable for use in cold regions. It can be difficult.

As described above, in the method of gelation by radical polymerization by heating, impurities derived from the catalyst remaining in the polymer electrolyte gel had an adverse effect on ionic conductivity and safety. In addition, in the gelation method by radical polymerization by light irradiation, the large interfacial resistance in the cell due to the restriction of light irradiation reduced the ionic conductivity. The present inventors have conducted intensive studies to overcome the disadvantages of the conventional polymer electrolyte gel. The inventors have found that a gel free from defects can be obtained by forming a crosslink of a specific polymer with a specific catalyst using a specific catalyst. 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. Disclosure of the invention

The first invention of the present invention relates to a crosslink obtained by subjecting a polymer having two or more epoxy groups per molecule (hereinafter referred to as an epoxy group-containing polymer) to a ring-opening and crosslinking reaction of an epoxy ring using a supporting electrolyte as a catalyst A polymer electrolyte gel comprising a polymer (hereinafter, referred to as an epoxy crosslinked polymer), the supporting electrolyte and an organic solvent.

According to a second invention, an epoxy group-containing polymer is obtained by polymerizing a monomer containing a vinyl group and an epoxy group in one molecule as an essential component, and does not contain metal ions other than lithium. A polymer electrolyte gel according to the invention.

A third invention is the supporting electrolyte is a polymer electrolyte gel according to any one of the first or second invention is a I-one compound containing a L i BF ₄ and Z or L i PF _6.

A fourth invention is the polymer electrolyte gel according to any one of the first, second, and third inventions, wherein the epoxy crosslinked polymer is 2 to 20% by weight based on the polymer electrolyte gel. The invention of claim 5 relates to 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 essential components, and a epoxide ring is subjected to ring-opening cross-linking reaction using the supporting electrolyte as a catalyst. The method for producing a polymer electrolyte gel according to any one of the first, second, third, and fourth inventions, wherein a crosslinked polymer is formed. It is. BEST MODE FOR CARRYING OUT THE INVENTION

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 an epoxy group by a polymer reaction called ring-opening bond of an epoxy ring. The prerequisite of being able to form a crosslinked polymer This means that if it is two or more in one molecule, the number, the bonding position, and the type of the main chain of the polymer are not particularly limited. Further, the mixture is not limited to one type, and may be a mixture of two or more types of epoxy group-containing polymers. Further, the number average molecular weight is not particularly limited, but is generally about 500 to 100000. Such an epoxy group-containing polymer can be obtained by introducing an epoxy group into an unsaturated hydrocarbon polymer or a polymer having a reactive functional group, such as a polyester, polyester, polyurethane, or vinyl polymer. Can be. For example, an epoxy group can be introduced into polybutadiene or polyisoprene having a double bond in a polymer by reacting the double bond with peracetic acid. In addition, polyethylene oxide having a hydroxyl group in the polymer can be used. Epoxy groups can be introduced into polypropylene oxide or the like by adding epichlorohydrin to hydroxyl groups and dehydrochlorinating with sodium hydroxide.

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

In order to use the vinyl polymer obtained by vinyl polymerization directly as an epoxy group-containing polymer, the vinyl polymer is a homopolymer of a monomer containing a vinyl group and an epoxy group, or the monomer is a copolymer component. It is essential that the copolymer be one of the above. Examples of monomers containing a vinyl group and an epoxy group include glycidyl methacrylate, glycidyl acrylate, 2-methyldaricidyl acrylate, 1,2-epoxy-1-butene, isopreneoxide, 1,2-epoxy-1 2-methyl-3-butene, 1,2-epoxy-5-hexene, 3-ethenyl-7-oxabicyclo [4,1,0] heptane, arylglycidyl ether, [(2-propenyloxy) methyl] oxylan, etc. No.

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. Further, the present invention is not limited to one kind, and two or more kinds of vinyl monomers may be used. Examples of such vinyl monomers Examples include acrylonitrile, 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 the hardness and other characteristics required for the polymer electrolyte gel. , Usually monomers containing vinyl and epoxy groups

The molar ratio of — / other vinyl monomers to be copolymerized is from 5/95 to 100, preferably from 20 to 80/85. If 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. May not be able to proceed efficiently. When the ratio is 100 mol%, that is, 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. The molecular weight of such a vinyl polymer is not particularly important since it eventually becomes a crosslinked body, and may be any value as long as it can be dissolved in a system of an organic solvent Z and a supporting electrolyte. It is in the order of 0 to 1 0 0 0 0 0 0 0.

In preparing such a vinyl polymer, it is important to carry out polymerization so that the epoxy group does not react 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 polymerization, so that the resulting polymer cannot be crosslinked and gelled in the subsequent process, or conversely, is crosslinked during polymerization. And the resulting polymer may be insoluble in organic solvents. Even when synthesizing by radical polymerization, the choice of polymerization catalyst is important because the electrochemical characteristics of the polymer electrolyte gel may be reduced depending on the type of 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 secondary batteries, Since metal ion impurities other than ON, such as metal ions and earth metal ions, increase the interface resistance, it is desirable to reduce such sodium ions as much as possible.

When redox polymerization must be used as described above, there is a method of washing with a strongly acidic aqueous solution to remove metal ion impurities incorporated in high molecules, but it is efficient for industrial production. Not a way. 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 metal ions such as an organic peroxide compound or an azo compound, ultraviolet irradiation, electron beam irradiation, or the like is used. It is recommended to polymerize by means of

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 in the case of 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, even if it is LB grade, there is no absolute absence of impurity metal ions at present. is there. Therefore, in the polymer electrolyte gel which is the final product of the present invention, the amount of the impurity metal ions derived from the epoxy group-containing polymer does not exceed the amount of the impurity metal ions derived from the coexisting supporting electrolyte or organic solvent. Therefore, it is treated as “not included”.

In the solution polymerization method recommended by the present invention, a radical polymerization catalyst that does not generate metal ions in an L.B. grade organic solvent, a monomer containing a vinyl group and an epoxy group, and in some cases, a copolymerization in addition to these. A solution was prepared by dissolving the vinyl monomer to be dissolved in a ratio of approximately 6 parts by weight of the organic solvent, 0.2 part of the polymerization catalyst, and 4 parts of the monomer, and the pinyl polymer, an epoxy group-containing polymer, was dissolved by heating or light irradiation. Create a molecular solution. The obtained polymer solution can be used as it is as a precursor of the polymer electrolyte gel, so there is no need to purify the polymer to remove impurities or to dry and dissolve it, simplifying the process. It is advantageous for industrial production.

The vinyl polymer that is the epoxy group-containing polymer described above is a polymer of the present invention. In the electrolyte gel, the epoxy ring contained in the polymer forms an epoxy-crosslinked polymer that has undergone a ring-opening crosslinking reaction, and the entire system is in a gel state.The ratio of the epoxy-crosslinked polymer to the polymer electrolyte gel is Is 2 to 20% by weight, preferably 2 to 10% by weight, based on 100% by weight of the entire polymer electrolyte gel. 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 ionic conductivity may be significantly reduced. In addition, when the epoxy ring contained in the epoxy group-containing polymer undergoes a ring-opening cross-linking reaction, no by-product is eliminated or another molecule is added. The ratio to the molecular electrolyte gel is equal to the ratio of the epoxy group-containing polymer to the solution before the ring-opening crosslinking reaction.

As a supporting electrolyte is employed in the present invention is then, L i C L_〇 _{_{4, L i BF 4, L}} i PF 6, L i inorganic compound such as As F ₆ and L i S_〇 _₃ CF _3, L iN (S_〇 _{_{_{2 CF 3) 2, L i}}} C fluorine lithium salts such as (S_〇 ₂ CF ₃₎ _3, tetraethylammonium Ann monitor © beam tetrafluoropropoxy O b borate, Kisafuruororin salt to tetra E chill ammonium Niu arm, monomethyl Triethylammonium tetrafluoroborate, monomethyltriethylammonium hexafluorophosphate and the like which are dissolved in an organic solvent are preferably used, and particularly preferred are L i BF ₄ and L i FF ₆ , or a combination of these.

Next, 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 the epoxy group-containing polymer and the supporting electrolyte. Are ethylene carbonate (abbreviated EC), propylene carbonate (abbreviated FC), butylene carbonate (abbreviated BC), getyl carbonate (abbreviated DEC), dimethyl carbonate (abbreviated DMC), and ethyl methyl carbonate (abbreviated EMC) Ether compounds such as carbonic acid esters such as ethylene glycol, propylene glycol, methyl sorb, and ethyl sorb, as well as gamma mabutyrolactone (abbreviated as GBL), sulfolane, dimethyl sulfoxide, adipitolyl, glutaronitrile, N —Single or two or more such as methylpyrrolidone and trimethyl phosphate Mixed solvent is recommended.

These organic solvents have an excellent ability to dissolve the epoxy group-containing polymer and the supporting electrolyte. As long as the boiling point is high, those having a high boiling point are preferred. Organic solvents having a boiling point of 90 ° C or less are easily evaporated and may have problems due to their high vapor pressure.

The epoxy bridge polymer, supporting electrolyte, and organic solvent obtained by the ring-opening crosslinking reaction of the epoxy group-containing polymer described above are essential components of the polymer electrolyte gel referred to in the present application. It is possible to add a polymer compound or a conductive additive which does not form a polymer.

The proportion of each of these components in the polyelectrolyte gel should be determined in consideration of the target electrochemical properties and physical properties. It is appropriate to use 0% by weight, 1 to 30% by weight of the supporting electrolyte, and the remainder being organic solvents 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. Thus, the epoxy groups can be ring-opened and crosslinked to form an epoxy crosslinked polymer, and the solution can be crosslinked to form a gel. As described above, in preparing the solution, a high molecular 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 processes are performed in a dry atmosphere having a dew point of 150 ° C. or less in a state where the outside air is shut off, in order to prevent an increase in moisture content due to moisture absorption.

The solution is changed from a solution state to a gel state (gelation) because a cross-linked structure is formed by a ring-opening cross-linking reaction between epoxy groups of the epoxy group-containing polymer as described above (cross-linked gelation). Cause). Tertiary amines, Lewis acids, protonic acids and the like can be used as a usual catalyst for this kind of cross-linking gelation reaction, and a gel is formed by heating at several tens of degrees Celsius for several hours. However, in this case, after cross-linking and gelation, all of these catalysts remain in the gel as impurities, hindering the movement of ions and increasing the interfacial wiping. It cannot be adopted because it causes a decrease in conductivity. Therefore, in the present invention, it is recommended to use a supporting electrolyte as a catalyst in this reaction, and particularly to use Li BF ₄ and Li PF 6. The present invention using a supporting electrolyte as a catalyst enables cross-linking and gelation without leaving any impurities in the gel, and is very preferable because the above-mentioned problem is overcome. 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 gelling 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 in which the epoxy group-containing polymer obtained by pre-polymerization is dissolved in the organic solvent, or in 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. Industrially, the latter method is particularly recommended because the production efficiency is high and a homogeneous polymer solution can be easily obtained because the step of removing and purifying the polymer from the polymerization system and purifying or drying and dissolving the polymer can be omitted. 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 remove the catalyst residue from the polymer solution by the solution polymerization method.

The epoxy ring-opening and cross-linking reaction of the present invention proceeds by directly heating the solution of the epoxide group-containing polymer, the organic solvent and the supporting electrolyte mixed and dissolved by the above-described method, and the desired polymer electrolyte gel is obtained. 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 to be used, that is, as a catalyst, Li BF ₄ or Li PF ₆ has a high catalytic ability and a rapid reaction. Depending on the type of supporting electrolyte, high temperature and long time are required for the cross-linking gelation to develop, but this reaction can be promoted by adding a small amount of Li BF ₄ or Li PF _6. is there. Epoxy rings are highly reactive, and even in this ring-opening cross-linking reaction, almost all of the epoxy rings present in the epoxy group-containing polymer are likely to react, but some epoxy rings are cross-linked due to steric hindrance. It is thought that there are times when it does not.

An excellent feature of the present invention described in detail above is that a polymer electrolyte gel can be obtained substantially without a catalyst by selecting an epoxy group-containing polymer as a starting material. 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 the catalyst is decomposed in the formed gel. No product or unreacted catalyst remains. Although a particular procedure is required, a gel containing no impurities can be obtained 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 ion conductivity. Example

Hereinafter, the present invention will be described more specifically with reference to representative examples and comparative examples, but the present invention is not limited to these examples. 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.

(Creation method of electrochemical characteristic evaluation cell)

A flat 0.2 mm thick lithium foil (electrode) is placed on the bottom of a stainless steel Petri dish, and a 0.2 mm thick Teflon square spacer is set on it. Then, add an appropriate amount of a solution prepared by mixing the epoxy group-containing polymer solution prepared in the following Examples and Comparative Examples and the supporting electrolyte solution in advance, and put a 0.2 mm thick Place a lithium foil (electrode), cover the petri dish so that there is no gap between the spacer and the lithium foil, and heat at 60 ° C for 1 hour to open and crosslink epoxy groups. The reaction was carried out to form a crosslinked gel, and a gel film of a polymer electrolyte gel having a thickness of 200 m was formed. The gel film sandwiched between the lithium foils is sandwiched between a 0.3 mm-thick nickel plate with a lead wire, inserted between two glass plates, and fixed with clips to evaluate the electrochemical characteristics. Cell was created.

(Evaluation of electrochemical characteristics)

The above-mentioned cell for electrochemical property evaluation was connected to an AC impedance measurement device (Solartron 1286 + 1250), and at 25, from 100 kHz to 1 Hz. The impedance at the measurement frequencies of 100 kHz and 100 Hz was measured as the bulk resistance value and the interface resistance value, respectively. The ionic conductivity was calculated from the bulk resistance value and the cell thickness and area.

After the above AC impedance measurement was continued at 25 ° C for 24 hours, the cell for evaluation was removed. Connected to an electrochemical measurement device (Solartron S 1-1280B), and subjected to polarization electrolysis using a cyclic voltammetry with an inversion voltage of ± 0.5 V and a potential sweep rate of 1 OmV / s at 25 ° C. The polarization current value at +0.5 V in the cycle was measured, and this was defined as the CV polarization current value for the lithium anode. Hereinafter, the value of the CV polarization current with respect to the lithium negative electrode 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 cell formation was determined. From these measurement results, the ratio between the interface resistance value immediately after the start of the measurement and the interface resistance value after 24 hours was determined, and was defined as the rate of increase in the interface resistance. 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 with a dew point of 50 ° C.

10 g of polyethylene glycol monomethyl ether (number average molecular weight 2000) was added to an aqueous solution in which 0.22 g of sodium hydroxide was dissolved in 20 g of water. This was heated to 45 ° C, 0.46 g of epichlorohydrin was added rapidly with vigorous stirring, heated to 95 ° C, and continued to stir for 80 minutes. The resulting solution is extracted with benzene, and a glycidyl-substituted terminal hydroxyl group of the polyethylene glycol monomethyl ester is substituted with a glycidyl group from the extract. An epoxy group-containing polymer was obtained.

4 g of the above polymer was dissolved in 6 g of a mixed solvent in which ethylene carbonate (EC) and propylene carbonate (PC) were mixed in a volume ratio of 2Z1 to obtain a single epoxy group-containing polymer solution. This A separately from a mixed solvent 9. 22 g of the the L i BF ₄ creates a 0. 78 g dissolved supporting electrolyte solution. A gel film was prepared using the monoepoxy group-containing polymer solution (2.0 Og) and the supporting electrolyte solution (8 Og) in accordance with the above-mentioned method, but could not be gelled.

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 was heated to 45 ° C., and 1.85 g of epichlorohydrin was added rapidly with vigorous stirring, heated to 95 ° C., and continued to stir for 80 minutes. Extract the resulting solution with benzene and freeze An epoxy group-containing high molecule having two epoxy groups in one molecule in which the hydroxyl groups at both ends of polyethylene dalicol were substituted and modified with glycidyl groups was obtained from the extract by the drying method. 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, according to the method described above, A cell was created and measurements were made.

Example 2>

In the mixed solvent of Comparative Example 1, 6.0 g of bisphenol A-epiclo-mouth hydrin copolymer in which both terminals are daricidyl groups (Poly (Bisphenol A-co-epichlorohydrin), gly-ci dyl end-capped, number average molecular weight 1075 ) 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>

Acrylonitrile (hereinafter abbreviated as AN) 2.0 g, vinyl acetate (hereinafter abbreviated as VAc) 0.4 g, glycidyl methacrylate (hereinafter abbreviated as GMA) 1.6 g, in 6 g of the same mixed solvent as in Comparative Example 1, 0.2 g of benzyl dimethyl ketal (hereinafter abbreviated as BDK) as a polymerization catalyst was added and dissolved. It has a peak one peak wavelength in 360 nm, after illumination at this wavelength is polymerized shines irradiation 10 minutes of 1 OmWZcm ² UV at 50 ° C, the vacuum vessel of the gauge-pressure 0. 09 MP a The unreacted monomer was removed 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.

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

Example 5>

800 ml of water is placed in a 2 liter flask, and a mixed solution of 50 g of AN, 10 g of VAc, and 40 g of GMA, and 0.6 g of sodium pyrosulfite and 0.2 g of ammonium persulfate as polymerization catalysts are dissolved in 120 ml of water. Each of the solutions thus obtained was continuously supplied over 2 hours. After this supply is completed, The polymerization was continued for hours. After the polymerization was completed, the flask was cooled to room temperature, and the contents were filtered and washed three times to remove unreacted monomers and polymerization catalyst residues, and the resulting epoxy group-containing polymer was dried under reduced pressure at 70 ° C. Water was removed by drying overnight in a vessel. In this polymer, a sulfone group derived from a polymerization catalyst was introduced and was not ion-exchanged. 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. Then, a cell was prepared and measured according to the method described above.

A mixed solvent of EC and Jetyl carbonate (DEC) mixed in a volume ratio of 1Z3

After adding 1.0 g of 68, stearyl methacrylate (hereinafter abbreviated as SMA) 0.8 g, GMA 2.2 g, and BDKO. 2 g as a polymerization catalyst and dissolving, ultraviolet light was obtained in the same manner as in Example 3. Polymerization and removal of unreacted monomers were performed to prepare a high-molecular solution containing epoxy group-containing high molecules. Separately, the mixed solvent 8.6 gtL i PF

A supporting electrolyte solution in which 1.4 g of ₆ was dissolved was prepared. Using 2.0 g of the epoxy group-containing polymer solution and 8.0 g of the supporting electrolyte solution, the heating conditions were set as described above.

A cell was prepared with the temperature changed to 70 ° C for 18 hours, and the measurement was performed.

And the epoxy group-containing polymer solution 2. 0 g of Example 3, a mixed solvent 8. 7 5 g of Comparative Example 1 L i S0 ₃ CF ₃ and 1. 25 g dissolved supporting electrolyte solution 8. 0 g mixed the solution was 0. 02 g dissolved L i BF ₄ as a supporting electrolyte of crosslinked gelling purposes. Using this solution, a cell was prepared and measured according to the method described above. <Comparative Example 2>

And the epoxy group-containing polymer solution 2. 0 g of Example 3, a mixed solvent 8. 7 5 g of Comparative Example 1 L i S_〇 ₃ CF ₃ and 1. 25 g dissolved supporting electrolyte solution 8. 0 g the mixed solution was dissolved 0. 02 g of one of the tin tetrachloride electrolyte L i S0 _₃ CF ₃ are more overwhelmingly powerful ring opening catalyst Lewis acid as a crosslinking gelling catalyst. Using this solution, a cell was prepared and measured according to the method described above.

<Comparative Example 3> Add 2.84 g of AN, 16 g of VACl, and 0.2 g of BDK as a polymerization catalyst to 6 g of the same mixed solvent as in Comparative Example 1, and dissolve.Then, UV polymerization and unreacted are performed in the same manner as in Example 3. The monomer was removed to prepare an AN / V Ac copolymer solution. 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 ANZVAc copolymer solution, 1.0 g of the crosslinkable monomer solution, 8.0 g of the supporting electrolyte solution of Comparative Example 1, and 0.04 g of azobisisobutyronitrile was used. Then, the heating conditions were changed to 70 ° C. for 5 hours in the above-described method to prepare a cell, and the measurement was performed. The gel film formed 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 polyester of Example 1 ゃ Example 2 Various types of organic solvents (Examples 3 and 6) and types of supporting electrolytes (Examples 3, 6, and 7) can also be selected. However, when the epoxy group-containing polymer contains a metal ion other than lithium as in Example 5, although it is superior to the conventional one, the characteristics are slightly lower than those of the other examples.

Compared to the polymer electrolyte gel of the present invention, in Comparative Example 1, a polymer containing a single epoxy group was used, and there was only one epoxy group per molecule, and even if an epoxy ring caused a ring-opening reaction, It does not gel because it produces only chain polymers. The presence of large amounts of metal ions derived from tin tetrachloride which acts in preference to Comparative Example 2, L i S_〇 ₃ CF ₃ are, Comparative Example 3 is a ring-opening crosslinking reaction to catalyze the supporting electrolyte Epokishi ring Although a crosslinked gel was formed, the presence of non-removable bubbles generated in the gel by the decomposition gas of azobisisobutyronitrile deteriorated the electrochemical characteristics. table 1

The epoxy group-containing polymer solution 0.5 of Example 3 and 9.5 g of the supporting electrolyte solution obtained by dissolving 0.7 g of Li BF ₄ in 9.3 g of the mixed solvent of Comparative Example 1 were used. A cell was prepared and measured according to the method described in (1).

Example 9>

Using 3.5 g of the supporting electrolyte solution obtained by dissolving 0.9 g of Li BF ₄ in 9.1 g of the mixed solvent of Comparative Example 1 and 3.5 g of the epoxy group-containing polymer solution of Example 3, A cell was prepared and measured according to the method described above.

Using the epoxy-containing polymer solution 5. O g Example 3, the supporting electrolyte solution 5. Og was 1. 09 g dissolved L i BF ₄ in a mixed solvent 8. 9 lg of Comparative Example 1, above A cell was prepared and measured according to the method described above.

Table 2 shows the measurement results of the epoxy cross-linked polymer concentration, the ionic conductivity, the interface resistance increase rate, 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 cross-linked polymer concentration of 2.0 to 20.0% by weight, all of which are excellent. It has been demonstrated to exhibit the following characteristics. A closer look shows that the lower the epoxy-crosslinked polymer concentration, the better the properties are, but this is probably because the smaller the epoxy-crosslinked polymer, the easier the ions to move. However, if the epoxy cross-linking polymer concentration is too low, gel formation may not be possible.

Table 2

Industrial applications

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

Claims

The scope of the claims

1. A bridging polymer (hereinafter, referred to as an epoxy group-containing polymer) obtained by subjecting a polymer having two or more epoxy groups to an epoxy ring-containing cross-linking reaction with a supporting electrolyte as a catalyst. A polymer electrolyte gel comprising the supporting electrolyte and an organic solvent.

2. The epoxy group-containing polymer according to claim 1, wherein the polymer is obtained by polymerizing a monomer containing a vinyl group and an epoxy group in one molecule as an essential component, and does not contain metal ions other than lithium. Polymer electrolyte gel.

3. The polymer electrolyte gel according to claim 1, wherein the supporting electrolyte is an ionic compound containing Li BF ₄ and / or Li PF ₆ .

4. The polymer electrolyte gel according to any one of claims 1, 2, and 3, wherein the epoxy cross-linked polymer accounts for 2 to 20% by weight based on the polymer electrolyte gel.

5. An epoxy-crosslinked polymer obtained by subjecting 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 to a ring-opening bridge 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, 2, 3, and 4, wherein