JP2006179279A - Separator for battery and method of manufacturing battery using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separator for a battery useful for manufacturing the battery and capable of contributing to safety in use of the battery manufactured, and to provide a method of manufacturing the battery using the separator. <P>SOLUTION: The separator for the battery comprises a foamed sheet of a reactive polymer formed by reacting a crosslinking agent comprising a multi-functional compound having reactivity to a functional group so that part of the functional group reacts with a crosslinkable polymer having the functional group. The battery is manufactured in such a way that an electrode sheet/separator laminate is formed by laminating the electrode sheet on the separator and bonding them, the laminate is put into a battery container, and an electrolyte in which the crosslinking agent comprising the multi-functional compound having reactivity to the functional group of a reactive polymer forming the separator is dissolved is poured in the battery container to crosslink the reactive polymer, and thereby, the electrode sheet is bonded to the separator. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a battery separator that is useful for battery production and can contribute to safety during use of the battery thus produced, and a battery production method using the battery separator.

  Conventionally, as a battery manufacturing method, a positive electrode sheet and a negative electrode sheet are laminated with a separator for preventing a short circuit between the electrodes, or a positive (negative) electrode sheet, a separator, and a negative (positive) electrode sheet. And separators are laminated in this order and wound to form an electrode sheet / separator laminate. After the electrode / separator laminate is charged into the battery container, an electrolyte is injected into the battery container and sealed. Methods are known (see, for example, Patent Documents 1 and 2).

  However, in such a battery manufacturing method, the electrode sheet and the separator are liable to shift each other during storage and transportation of the electrode sheet / separator laminate, resulting in low battery manufacturing productivity, There were problems such as the occurrence of defective products. Further, according to the battery thus obtained, the electrode expands or contracts at the time of use, the adhesion between the electrode sheet and the separator is deteriorated, and the battery characteristics are deteriorated. A short circuit occurred, and the battery was heated and heated. In some cases, the battery could even be destroyed.

  On the other hand, porous films for battery separators are conventionally produced by various production methods. For example, as one method, a method of manufacturing a sheet made of polyolefin resin and stretching it at a high magnification is known (see, for example, Patent Document 3). However, the battery separator made of a porous membrane obtained by stretching at a high magnification in this way is significantly shrunk under a high temperature environment such as when the battery is abnormally heated due to an internal short circuit or the like. There is a problem that it does not function as a partition between electrodes.

Therefore, in order to improve the safety of the battery, reduction of the thermal contraction rate of the battery separator under such a high temperature environment is an important issue. In this regard, for example, in order to suppress the thermal shrinkage of the battery separator in a high-temperature environment, for example, ultrahigh molecular weight polyethylene and a plasticizer are melt-kneaded and extruded into a sheet form from a die, and then the plasticizer is extracted and removed. And the method of manufacturing the porous film | membrane used for a battery separator is also known (refer patent document 4). However, according to this method, contrary to the above method, the obtained porous film has not been stretched, and thus there is a problem that the strength is not sufficient.
JP 09-161814 A JP 11-329439 A Japanese Patent Application Laid-Open No. 09-012756 Japanese Patent Laid-Open No. 05-310989

  The present invention has been made to solve the above-described problems in the manufacture of a conventional battery. In the manufacture of a battery, an electrode sheet and a separator are temporarily bonded together to form an electrode sheet / separator laminate. As a result, the battery can be efficiently manufactured without the mutual movement of the electrode sheet and the separator, and after the battery is manufactured, the electrode sheet is not only superior in both ion permeability and electric insulation. It is an object of the present invention to provide a battery separator that functions as an electrode sheet / separator assembly having strong adhesion to the battery and provides a battery with high performance and excellent safety. Furthermore, this invention aims at providing the manufacturing method of a battery using such a battery separator.

  According to the present invention, a crosslinking agent comprising a polyfunctional compound having reactivity to the functional group is reacted so that a part of the functional group reacts with the crosslinkable polymer having a functional group, and the crosslinkability is increased. A battery separator comprising a foamed sheet of a reactive polymer obtained by partially crosslinking a polymer is provided.

  Further, according to the present invention, the electrode sheet is laminated on the separator, and the electrode is laminated to form an electrode sheet / separator laminate. After the laminate is charged into the battery container, the reactive polymer that forms the separator is formed. Injecting an electrolytic solution in which a crosslinking agent composed of a polyfunctional compound having reactivity with respect to the functional group is dissolved into the battery container, further crosslinking the reactive polymer, and bonding the electrode sheet to the separator. A battery manufacturing method is provided.

  The separator for a battery according to the present invention is a reactive polymer obtained by reacting a crosslinkable polymer having a functional group in the molecule with a crosslinker composed of a polyfunctional compound having reactivity with the functional group, and partially crosslinking the polymer. If the electrode sheet is pressure-bonded to this separator while heating, if necessary, the electrode sheet can be easily temporarily bonded to the separator, and the electrode sheet / separator laminate Can be obtained.

  Therefore, by using such an electrode sheet / separator laminate in the production of a battery, it is possible to efficiently produce a battery without shear movement between the electrode sheet and the separator. In addition, even when such a laminate is prepared in a battery container and an electrolyte solution is injected into the battery container, the reactive polymer that forms the separator is already partially crosslinked, so that it elutes into the electrolyte solution. The temporary adhesion with the electrode / separator is maintained. Further, by dissolving the same cross-linking agent as described above in this electrolytic solution, the further adhesion of the reactive polymer in the electrode sheet / separator causes the separator to adhere more strongly to the electrode sheet. A joined body can be formed, and thus the battery performance can be kept high and the battery safety can be contributed.

  Moreover, since the battery separator of the present invention is made of a polymer foam sheet, if the electrolyte is poured into the battery container after being charged into the battery container, the electrolyte quickly penetrates and spreads through the separator. Therefore, the electrolyte solution can be quickly injected into the battery container. In addition, since the battery separator of the present invention is made of a polymer foam sheet, it is excellent in both ion permeability and electrical insulation, and provides a high-performance battery.

  In the present invention, the crosslinkable polymer refers to a polymer that has a functional group in the molecule and can be cross-linked by reacting with a cross-linking agent composed of a polyfunctional compound having reactivity with the functional group. The reactive polymer refers to a polymer obtained by reacting the crosslinkable polymer with a part of its functional group and the crosslinker, and crosslinking the crosslinkable polymer with a part of the functional group. Thus, the reactive polymer is already partially crosslinked by itself. The battery separator according to the present invention comprises such a foamed sheet of reactive polymer.

  Further, in the present invention, the electrode sheet / separator laminate refers to a laminate in which an electrode sheet is pressure-bonded, temporarily bonded, and bonded to a separator made of a reactive polymer foam sheet as described above. The electrode sheet / separator assembly is an electrode sheet / separator laminate in which electrode is formed by further reacting the reactive polymer that forms the separator with the cross-linking agent at the unreacted functional group and cross-linking. The sheet is bonded to a porous film.

  The battery separator according to the present invention, as described above, is a cross-linking formed of a polyfunctional compound having reactivity with respect to the functional group such that the cross-linkable polymer having the functional group reacts with a part of the functional group. It is made of a foamed sheet of a reactive polymer obtained by reacting an agent and partially crosslinking the crosslinkable polymer. That is, by causing a predetermined amount of a crosslinking agent capable of reacting with the functional group to the crosslinkable polymer to react under a predetermined condition, the crosslink reaction by the functional group of the crosslinkable polymer is controlled to partially crosslink the functional group. It can be added to the reaction. As described above, the battery separator according to the present invention already has a crosslinked structure due to the reaction between a part of the functional groups and the crosslinking agent, and further crosslinks with the unreacted functional groups and further with the crosslinking agent. And a reactive polymer foam sheet.

  In the present invention, the crosslinkable polymer is, for example, a copolymerizable monomer having at least one functional group selected from a hydroxy group, a carboxyl group and an epoxy group, and other copolymerizable compounds having no such functional group. The monomer can be obtained by ordinary radical copolymerization such as solution polymerization, bulk polymerization, and emulsion polymerization. For example, solution polymerization can be obtained as a polymer solution by copolymerizing required monomers in a solvent such as benzene, toluene, xylene, ethyl acetate, and butyl acetate. On the other hand, according to the emulsion polymerization method, since an aqueous dispersion of a crosslinkable polymer can be obtained, after the polymer is separated and dried from this, it is dissolved in a solvent as described above and used as a polymer solution. According to the present invention, the crosslinkable polymer thus obtained preferably has a weight average molecular weight in the range of 200,000 to 3,000,000.

  Examples of the copolymerizable monomer having a carboxyl group as the functional group include (meth) acrylic acid, itaconic acid, maleic acid and the like. Examples of the copolymerizable monomer having a hydroxy group as the functional group include And hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl acrylate and the like. Furthermore, examples of the copolymerizable monomer having an epoxy group as a functional group include glycidyl (meth) acrylate, epoxycyclohexyl (meth) acrylate, vinylcyclohexene epoxide, and the like. Among these, acrylic monomers such as (meth) acrylic acid, hydroxyalkyl (meth) acrylate, glycidyl (meth) acrylate, and the like are preferably used.

  On the other hand, examples of other copolymerizable monomers having no functional group include (meth) acrylic acid esters, (meth) acrylamides, (meth) acrylonitriles, (meth) acrylic acid polyethylene glycol alkyl ethers (meth) In addition to acrylic monomers, various vinyl monomers such as styrene, vinyl acetate, N-vinyl pyrrolidone, vinylene carbonate and the like can be mentioned.

  Examples of the (meth) acrylic acid ester include ethyl (meth) acrylate, butyl (meth) acrylate, propyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, and the like. As described above, alkyl esters having 1 to 12 carbon atoms in the alkyl group are preferably used.

  In addition to the above, for example, (meth) acrylic acid isobornyl ester, dicyclopentenyl ester, tetrahydrofurfuryl ester, etc., and cyclic hydrocarbon groups such as benzyl and cyclohexyl groups and maleimide groups in the molecule. The (meth) acrylic acid ester having a glass transition temperature of a homopolymer such as (meth) acrylic acid ester having a high polarity group such as an imide group or the like having a glass transition temperature of 23 ° C. or higher is obtained. It is preferably used when it is necessary to increase the glass transition temperature of the resulting crosslinkable polymer. As the (meth) acrylic acid polyethylene glycol alkyl ether, methyl ether or ethyl ether having 3 to 100, preferably 5 to 30, oxyethylene units is preferably used.

  Examples of the (meth) acrylamide include N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-di-n-propyl (meth) acrylamide, and N, N-. Examples include diisopropyl (meth) acrylamide, N- (meth) acryloylmorpholine, N- (meth) acryloylpyrrolidone, N- (meth) acryloylpiperidine, N- (meth) acryloylpyrrolidine.

  In particular, in the present invention, as a preferred example of the crosslinkable polymer, an acrylic monomer component such as (meth) acrylic acid ester, (meth) acrylonitrile, (meth) acrylamide, together with the acrylic monomer component having the functional group described above. And a crosslinkable polymer. For example, a crosslinkable polymer having a (meth) acrylonitrile component up to 80% by weight, preferably in the range of 5 to 70% by weight is excellent in heat resistance and solvent resistance. It is an example. A crosslinkable polymer comprising 0.1 to 20% by weight of a monomer component having a functional group, 10 to 95% by weight of a (meth) acrylic acid ester component and 4.9 to 60% by weight of (meth) acrylonitrile is such a preferred crosslink. It is an example of a conductive polymer.

  In the present invention, the radical polymerizable monomer having at least one functional group selected from the above hydroxyl group, carboxyl group and epoxy group is preferably in the range of 0.1 to 20% by weight in the total monomers, particularly The range of 0.1 to 10% by weight is preferable. When the ratio of the radical polymerizable monomer having at least one functional group selected from the above hydroxyl group, carboxyl group and epoxy group in the total amount of the monomer is less than 0.1% by weight, the resulting crosslinkable polymer has a crosslinking agent. Even when the cross-linkable polymer is reacted, the cross-linking degree of the cross-linkable polymer is too small, and when the obtained separator / electrode sheet is laminated and brought into contact with the electrolytic solution, the reactive polymer easily elutes into the electrolytic solution. The sheet / separator laminate may be separated. On the other hand, when the content exceeds 20% by weight, there is a possibility that when the resulting crosslinkable polymer is reacted with a crosslinker, the crosslinkable polymer is excessively crosslinked, making it difficult to pressure-bond the electrode sheet to the resulting separator. is there.

  However, in the present invention, the crosslinkable polymer is not limited to the above, and any crosslinkable polymer may be used as long as it has the functional group in the molecule and can react and crosslink with a crosslinking agent composed of a polyfunctional compound. . Therefore, for example, a polyolefin-based polymer having a hydroxy group, a rubber-based polymer, a polyester-based polymer, a polyether-based polymer, or the like, an acrylic-modified fluororesin having a hydroxy group in the molecule (for example, Cephalal Coat FG730B manufactured by Central Glass Co., Ltd., Can be obtained as a varnish.) Can also be suitably used as a crosslinkable polymer.

  According to the present invention, the crosslinkable polymer usually preferably has a glass transition temperature in the range of −30 ° C. to 100 ° C., particularly preferably in the range of 0 ° C. to 80 ° C. When the glass transition temperature of the crosslinkable polymer is 0 ° C. or lower, if the electrode sheet is pressure-bonded to a reactive polymer foam sheet (separator) obtained from such a crosslinkable polymer at room temperature, the electrode sheet is used as the separator. The electrode sheet / separator laminate can be obtained immediately after temporary bonding.

  When the glass transition temperature of the crosslinkable polymer is in the range of 0 to 100 ° C., the electrode sheet is usually temporarily bonded to the separator made of a foamed sheet of a reactive polymer obtained from such a crosslinkable polymer. It is necessary to heat and heat and crimp an electrode sheet to this. However, when the glass transition temperature of the crosslinkable polymer is in the range of 0 to 100 ° C., particularly at room temperature or higher, most preferably 50 ° C. or higher, the separator has no blocking property at room temperature, There is an advantage that when a separator is laminated or wound on a roll, it is not necessary to sandwich a release sheet therebetween.

  According to the present invention, in order to obtain such a reactive polymer by reacting such a crosslinkable polymer with a part of the functional group and partially crosslinking the crosslinkable polymer, a crosslinking agent comprising a polyfunctional compound is provided. Used. When the functional group of the crosslinkable polymer is a hydroxy group or a carboxyl group, as the crosslinking agent, for example, a polyfunctional isocyanate or a polyfunctional epoxy compound is preferably used, and when the functional group is an epoxy group, crosslinking is performed. As the agent, for example, an acid anhydride is preferably used.

  Examples of the polyfunctional isocyanate include phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, diphenyl ether diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, and other aromatic, araliphatic, alicyclic, and aliphatic diisocyanates, and trimethylolpropane. So-called isocyanate adducts obtained by adding these diisocyanates to such polyols are also preferably used.

  As the polyfunctional epoxy compound, N, N, N ′, N′-tetraglycidyl-m-xylenediamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, bisphenol A type epoxy resin, alicyclic ring An epoxy resin, an aliphatic chain epoxy resin, a phenol novolac type epoxy resin, and the like can be given. Examples of the acid anhydride include maleic anhydride, adipic anhydride, and phthalic anhydride.

  The battery separator according to the present invention comprises a reactive polymer foamed sheet obtained by partially crosslinking the crosslinkable polymer as described above with such a crosslinking agent, and here, means for foaming the crosslinkable polymer, As the method, chemical foaming using a foaming agent is preferably employed. However, the means and method for foaming the cross-linkable polymer are not limited to those using such a foaming agent. For example, the solution of the cross-linkable polymer is stirred at a high speed so that bubbles are held in the solution. A battery separator made of a foamed sheet of a reactive polymer can also be obtained by forming a crosslinkable polymer from such a solution and partially crosslinking it. Moreover, it can also be based on foaming using a supercritical liquid such as carbon dioxide gas.

  In chemical foaming using a foaming agent, examples of the foaming agent include azodicarbonamide, dinitrosopentamethylenetetramine, oxybis (benzenesulfonylhydrazide), sodium bicarbonate, and the like, but are not limited thereto. is not. These foaming agents are usually in the range of 1 to 20 parts by weight with respect to 100 parts by weight of the crosslinkable polymer, depending on the foaming ratio and the like in the foamed sheet to be obtained. Although it depends on the foaming ratio of the sheet, a foamed sheet can be obtained by heating the crosslinkable polymer containing these foaming agents to 100 to 200 ° C.

  Thus, when a foaming agent is used, a foaming aid such as zinc oxide, zinc carbonate, zinc stearate, or a core such as silica fine powder is used to adjust the foaming temperature and to make the generated bubbles uniform or fine. An agent, a fluorosurfactant, an alcohol, a polyol compound, or the like can be used in combination.

  The battery separator according to the present invention can be obtained by partially crosslinking and foaming the aforementioned crosslinkable polymer. As an example of the production method, for example, a predetermined amount of the above-mentioned cross-linking agent is added to the above-mentioned cross-linkable polymer solution, that is, it is sufficient to cause the cross-linkable polymer to react with some of the functional groups and partially cross-link. For example, in the case of chemical foaming, a foaming agent as described above is blended, and a solution of the obtained mixture is subjected to an appropriate peelable support, such as a stretched polypropylene film or a release treatment. After casting on paper or the like, the mixture is heated to remove the solvent in the crosslinkable polymer solution. First, a sheet of a mixture containing the crosslinkable polymer, the crosslinker, and the foaming agent is obtained. Subsequently, the sheet of the mixture containing the crosslinkable polymer, the crosslinker, and the foaming agent is sandwiched between, for example, a gas-impermeable film, heated to foam the foaming agent, and the foamable sheet of the crosslinkable polymer. In addition, a battery separator made of a foamed sheet of a reactive polymer can be obtained by reacting the crosslinkable polymer with the crosslinker and partially crosslinking the polymer. If necessary, after obtaining a foamed sheet of a crosslinkable polymer, the crosslinkable polymer may be postcrosslinked.

  According to the present invention, the separator made of the foamed sheet of the reactive polymer thus obtained has a foaming ratio in the range of 2 to 20 times, a thickness in the range of 5 to 500 μm, and a foam diameter of 500 μm or less, preferably 200 μm. The following is preferable. Here, the expansion ratio refers to the ratio of the thickness of the foamed sheet to the thickness of the crosslinkable polymer sheet before foaming. When the thickness of the separator made of the reactive polymer foam sheet is thinner than 5 μm, the strength is insufficient, and an internal short circuit may occur in the battery. However, when the thickness exceeds 500 μm, the internal resistance of the battery becomes excessive as a result of the distance between the electrodes being too large.

Furthermore, the separator made of such a reactive polymer foam sheet according to the present invention has a gel fraction in the range of 20-100%, preferably a gel fraction in the range of 25-80%. Here, the gel fraction refers to a mixture of a crosslinkable polymer A part by weight, a polyfunctional compound B part by weight and a foaming agent , cast on a peelable support, remove the solvent, and then heat, While foaming or after foaming the crosslinkable polymer, it is partially crosslinked to form a foamed sheet made of a reactive polymer. This foamed sheet is used as a non-aqueous solvent for an electrolyte used in a battery at a temperature of 23 ° C. After dipping for 7 days, the non-aqueous solvent was replaced with a readily volatile solvent such as ethyl acetate or tetrahydrofuran and dried, and the remaining reactive polymer was C parts by weight, (C / (A + B )) × 100 (%).

  In the present invention, to obtain a foamed sheet of a reactive polymer having a gel fraction in the range of 20 to 100%, it is not limited, but as described above, usually, with respect to 100 parts by weight of the crosslinkable polymer. In combination with the foaming agent, the polyfunctional compound is blended in the range of 0.1 to 10 parts by weight, heated to foam the crosslinkable polymer, and until the reactive polymer obtained is stabilized characteristically, It can be obtained by carrying out a crosslinking reaction. Although the heating temperature for crosslinking of the crosslinkable polymer and the reaction time therefor depend on the crosslinkable polymer used, the polyfunctional compound, the type thereof, and the like, these reaction conditions can be determined by experiments. For example, heating and reacting at a temperature of 50 ° C. for 7 days usually completes the cross-linking reaction of the cross-linkable polymer with the polyfunctional compound and stabilizes the resulting reactive polymer in terms of properties.

  Furthermore, according to the present invention, the separator made of a foamed sheet of reactive polymer preferably has a degree of swelling of 5 times or more, particularly 10 times or more. Here, the degree of swelling means that a mixture of A part by weight of crosslinkable polymer B, part by weight of polyfunctional compound B and a foaming agent is cast on a peelable support, and after removing the solvent, Heating to foam the crosslinkable polymer, or after foaming, partially cross-linking to form a foamed sheet made of a reactive polymer, and this foamed sheet becomes a non-aqueous solvent for the electrolyte used in the battery A value defined as D / C, assuming that the weight in the swollen state when immersed at a temperature of 23 ° C. for 7 days is D, and then the remaining reactive polymer is C parts by weight after the separator is dried. It is. This degree of swelling can be appropriately adjusted depending on the monomer composition and molecular weight distribution of the crosslinkable polymer, the amount of functional groups possessed by the crosslinkable polymer, the amount of crosslinker used, and the like. According to the present invention, when the swelling degree of the reactive polymer is less than 5 times, the obtained battery may be inferior in characteristics.

  In the absence of a cross-linking agent, a separator made of such a foamed sheet of a reactive polymer is stable and can be altered even when stored for a long period of time because it does not react or crosslink. Absent.

  According to the present invention, if an electrode sheet is pressure-bonded to a separator made of a foamed sheet of such a reactive polymer under heating as necessary, the electrode sheet can be easily temporarily bonded and bonded to the separator. Thus, an electrode sheet / separator laminate can be obtained.

  According to the present invention, an electrode sheet, that is, a negative electrode sheet and a positive electrode sheet are respectively pressure-bonded to the front and back surfaces of the separator, temporarily bonded, and bonded together to form an electrode sheet / separator laminate. Only the electrode sheet, that is, either the negative electrode sheet or the positive electrode sheet may be pressure-bonded and temporarily bonded to form an electrode sheet / separator laminate. Of course, it can also be set as the laminated body which has the structure of a positive (negative) electrode sheet / separator / negative (positive) electrode sheet / separator.

  In the present invention, the electrode sheet, that is, the negative electrode sheet and the positive electrode sheet are different depending on the battery, but in general, an active material and, if necessary, a conductive agent are supported on a conductive base material using a resin binder. A sheet-like material is used.

  According to the present invention, by using such an electrode sheet / separator laminate, there is no mutual movement of the electrode sheet and the separator, and the battery can be efficiently manufactured. The separator contributes to the safety of the battery as an electrode sheet / separator assembly bonded to the electrode sheet.

  That is, after the electrode sheet / separator laminate is charged into a battery container, it comprises a polyfunctional compound as described above having reactivity with the unreacted functional group of the reactive polymer forming the separator. By injecting an electrolytic solution in which a cross-linking agent is dissolved into a battery container, reacting with the unreacted functional group of the reactive polymer forming the separator of the electrode sheet / separator, and further cross-linking this, A battery having an electrode sheet / separator assembly obtained by bonding and integrating the electrode sheet to the separator and firmly bonding the electrode sheet to the separator can be obtained. However, according to the present invention, the crosslinking agent used here may be the same as or different from the one used to obtain a reactive polymer by partially crosslinking the crosslinkable polymer.

  The ratio of the crosslinking agent in the electrolytic solution is usually in the range of 0.1 to 20 parts by weight with respect to 100 parts by weight of the separator made of the reactive polymer. When the proportion of the cross-linking agent is less than 0.1 parts by weight with respect to 100 parts by weight of the separator, the cross-linking of the reactive polymer by the cross-linking agent is insufficient, and in the resulting electrode sheet / separator assembly, It is not possible to obtain a strong bond between the separator and the separator. However, when the proportion of the crosslinking agent is more than 20 parts by weight with respect to 100 parts by weight of the reactive polymer, the separator after crosslinking may be too hard and may inhibit the adhesion between the separator and the electrode sheet.

  According to the present invention, as described above, the reactive polymer is previously cross-linked so as to have a gel fraction in the range of 5 to 100%, so that the electrode sheet / separator laminate is placed in the electrolyte solution. Even when immersed, elution of the reactive polymer into the electrolytic solution is prevented or reduced, so that it is effectively used for adhesion of the electrode sheet. Moreover, since the reactive polymer has a degree of swelling of 5 times or more, it crosslinks by the curing reaction of the epoxy group while swelling so as to enclose these at the interface between the separator and the electrode sheet temporarily bonded thereto, The sheet is more firmly bonded to the separator to provide an electrode sheet / separator assembly. According to the present invention, the degree of swelling of the reactive polymer is almost the same as that before crosslinking even after crosslinking by the epoxy group curing reaction. The characteristics of the obtained battery are superior as the degree of swelling increases.

  According to the present invention, the temperature is such that the electrode is placed along the surface of the separator made of a foamed sheet of a reactive polymer obtained by partially crosslinking the crosslinkable polymer in advance and the separator is not deformed. The electrode sheet is preferably partially pressed into a separator made of a reactive polymer, so that the electrode sheet is temporarily bonded to the separator to form an electrode sheet / separator laminate. After charging this laminate into a battery container, an electrolytic solution in which a crosslinking agent is dissolved is poured into the battery container, and reacted with unreacted functional groups of the reactive polymer that forms the separator. Are further cross-linked to obtain an electrode sheet / separator assembly. That is, the electrode sheet is actually bonded to the separator.

  As in the case of the electrode sheet / separator laminate described above, in the present invention, the electrode sheet / separator assembly is not limited to the negative electrode sheet / separator / positive electrode sheet assembly, but either the negative electrode sheet or the positive electrode sheet / A separator assembly and a configuration of positive (negative) electrode sheet / separator / negative (positive) electrode sheet / separator are also included.

  The electrolytic solution is a solution obtained by dissolving an electrolyte salt in a solvent. Examples of the electrolyte salt include alkali metals such as hydrogen, lithium, sodium, and potassium, alkaline earth metals such as calcium and strontium, tertiary or quaternary ammonium salts, and the like as a cation component, hydrochloric acid, nitric acid, and phosphoric acid. , Salts containing inorganic acids such as sulfuric acid, borohydrofluoric acid, hydrofluoric acid, hexafluorophosphoric acid, perchloric acid, and organic acids such as organic carboxylic acids, organic sulfonic acids, and fluorine-substituted organic sulfonic acids as anionic components Can be used. However, among these, an electrolyte salt containing an alkali metal ion as a cation component is particularly preferably used.

  Any solvent can be used as the solvent for the electrolytic solution as long as it dissolves the above electrolyte salt. Examples of non-aqueous solvents include ethylene carbonate, propylene carbonate, butylene carbonate, and γ-butyrolactone. Cyclic esters such as tetrahydrofuran, ethers such as dimethoxyethane, and chain esters such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. These solvents are used alone or as a mixture of two or more.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

(Measurement of glass transition temperature of crosslinkable polymer)
After the solution of the crosslinkable polymer was cast on a release paper and dried, a sheet having a thickness of 0.2 to 0.5 mm and a width of 5 mm was obtained. The sheet was made a distance of 10 mm between chucks, manufactured by Seiko Electronics Industry Co., Ltd. Using DSM120, the storage elastic modulus (E ′) and loss elastic modulus (E ″) were measured at 10 Hz in a bending mode at a temperature range of −50 ° C. to 200 ° C. and a heating rate of 5 ° C./min. The peak temperature of E ″ / E ′) was taken as the glass transition temperature.

(Preparation of electrode)
Lithium cobaltate (LiCoO ₂ ) having an average particle size of 15 μm, graphite powder and polyvinylidene fluoride resin were mixed at a weight ratio of 85: 10: 5, and this was added to N-methyl-2-pyrrolidone to obtain a solid content concentration of 15 wt. % Slurry was prepared. This slurry was applied to the surface of an aluminum foil having a thickness of 20 μm to a thickness of 200 μm, and then dried at 80 ° C. for 1 hour. Thereafter, the slurry was similarly applied to the back surface of the aluminum foil to a thickness of 200 μm, dried at 120 ° C. for 2 hours, and then passed through a roll press to prepare a positive electrode sheet having a thickness of 200 μm.

  Graphite powder and polyvinylidene fluoride resin were mixed at a weight ratio of 95: 5 and added to N-methyl-2-pyrrolidone to prepare a slurry having a solid content concentration of 15% by weight. This slurry was applied to the surface of a 20 μm thick copper foil to a thickness of 200 μm and then dried at 80 ° C. for 1 hour. Thereafter, the slurry was similarly applied to the back surface of the copper foil to a thickness of 200 μm, dried at 120 ° C. for 2 hours, and then passed through a roll press to prepare a negative electrode sheet having a thickness of 200 μm.

(Evaluation of adhesion between separator and electrode sheet)
Electrolyte solution in which trifunctional isocyanate obtained by adding 3 mol parts of hexamethylene diisocyanate to 1 mol part of trimethylolpropane is dissolved in a positive electrode sheet / separator / negative electrode sheet laminate punched to a predetermined size (used in the following examples) The same as the above), sandwiched between glass plates, put into a desiccator saturated with electrolyte vapor to suppress the evaporation of the electrolyte, and put in a constant temperature room at 50 ° C. for 7 days, The reactive polymer forming the separator in the positive electrode sheet / separator / negative electrode sheet laminate is cross-linked with the trifunctional diisocyanate, and the positive and negative electrode sheets are adhered to the separator, and the positive electrode sheet / separator / negative electrode sheet assembly is obtained. Got.

  The positive electrode / separator / negative electrode sheet assembly thus obtained was cut to a width of 1 cm and then immersed in an electrolytic solution at room temperature for 24 hours. Thereafter, when the positive and negative electrode sheets were peeled off from the positive electrode sheet / separator / negative electrode sheet assembly in a wet state, the case where there was resistance was marked with ◯, and the case where the electrodes had already been peeled was marked with x.

(Evaluation of battery performance)
After charging and discharging 5 times at a rate of 0.2 CmA, charging was performed at a rate of 0.2 CmA, and thereafter, discharging was performed at a rate of 2.0 CmA, and a discharge capacity at 2.0 CmA / 0 The discharge load characteristics were evaluated by the discharge capacity ratio at a rate of 2 CmA.

(Battery heat resistance)
After heating the battery at 150 ° C. for 1 hour, the presence or absence of a short circuit between the electrodes was examined.

(Foam diameter and expansion ratio in the foam sheet)
Ten points of foaming on the surface of the foamed sheet were observed with a microscope, and the average value was taken as the foamed diameter. Moreover, the value which remove | divided the thickness of the sheet | seat after foaming by the thickness of the sheet | seat before foaming was made into the foaming ratio.

Example 1
(Preparation of crosslinkable polymer)
N, N-dimethylacrylamide 50 parts by weight Acrylonitrile 10 parts by weight 2-hydroxyethyl acrylate 3 parts by weight Methyl methacrylate 15 parts by weight Butyl acrylate 22 parts by weight Azobisisobutyronitrile 0.3 part by weight Ethyl acetate 150 parts by weight

The monomer, polymerization initiator, and solvent were charged into a four-necked flask equipped with a stirrer, a nitrogen inlet tube, and a condenser, and the inside of the flask was purged with nitrogen under stirring. Next, polymerization is carried out at 62 ° C. for 8 hours with stirring in a warm water bath, and further heated to 75 ° C. and held at this temperature for 3 hours. A solution of a functional polymer was obtained. This crosslinkable polymer had a weight average molecular weight of 4.5 × 10 ⁵ and a glass transition temperature of 63 ° C.

(Preparation of separator)
1 part by weight of trifunctional isocyanate obtained by adding 3 parts by mole of hexamethylene diisocyanate to 1 part by weight of trimethylolpropane, 5 parts by weight of a foaming agent (Neocelbon 1000S manufactured by Eiwa Kasei Kogyo Co., Ltd.), 3 parts by weight of zinc oxide and fine silica 1 part by weight of the powder was added to 100 parts by weight of the crosslinkable polymer in the ethyl acetate solution of the crosslinkable polymer to obtain a solution of a crosslinkable polymer / crosslinking agent / foaming agent mixture.

  This crosslinkable polymer / crosslinking agent / foaming agent mixture solution was applied onto a release film having a thickness of 40 μm made of a release-treated polyester film, dried at 70 ° C., and then having a thickness of 3 μm on the release sheet. A sheet comprising a mixture of / crosslinking agent / foaming agent (hereinafter, this sheet is simply referred to as a crosslinkable polymer sheet for simplicity) was obtained. A 40 μm thick peelable sheet made of the same polyester film as described above was further superimposed on the above sheet on the peelable sheet, and the resulting laminate was heated at 150 ° C. for 10 minutes to obtain a foamed sheet.

  Thereafter, this foamed sheet is further placed in a thermostatic chamber at 50 ° C. for 3 days, and the hydroxyl group of the crosslinkable polymer forming the foamed sheet is reacted with the above trifunctional isocyanate to partially crosslink the reactive polymer. Thus, a laminate including a separator made of a reactive polymer foam sheet was obtained. The separator made of this reactive polymer foam sheet had a gel fraction of 45%, a thickness of 40 μm, a foaming magnification of 13 times, a foam diameter of 100 μm, and a degree of swelling of 35 times.

  Next, one peelable sheet is peeled and removed from the laminate, the separator is exposed on the other peelable sheet, the positive electrode sheet is overlaid on the surface of the separator, and a heat bonding roll having a temperature of 85 ° C. The positive electrode sheet was pressure-bonded to the separator. Next, the other peelable sheet is peeled and removed to expose the back surface of the separator, and the negative electrode sheet is overlaid on the back surface of the separator. Similarly, using a heat bonding roll at a temperature of 85 ° C., the separator Thus, the negative electrode sheet was pressure-bonded to obtain a negative electrode sheet / separator / positive electrode sheet laminate (hereinafter sometimes referred to as an electrode sheet / separator laminate).

(Assembly of battery and evaluation of battery performance)
In an argon-substituted glove box, electrolyte salt lithium hexafluorophosphate (LiPF ₆ ) was dissolved in an ethylene carbonate / ethyl methyl carbonate mixed solvent (volume ratio 1/2) to a concentration of 1.2 mol / L. An electrolyte solution was prepared. Furthermore, 1 part by weight of trifunctional isocyanate obtained by adding 3 parts by mole of toluene diisocyanate to 1 part by weight of trimethylolpropane was dissolved in 100 parts by weight of the electrolytic solution.

  The electrode sheet / separator laminate is charged into a 2016-size coin-type battery can that also serves as a positive and negative electrode plate, and an electrolyte solution in which the trifunctional isocyanate is dissolved is poured into the coin-type battery can. The work in process was made. Thereafter, this work-in-process is put into a thermostatic chamber at a temperature of 50 ° C. for 7 days, and the reactive polymer in the electrode / separator laminate is cross-linked with the trifunctional isocyanate at its unreacted hydroxyl group, The positive and negative electrode sheets are bonded to and integrated with the separator, and thus a coin-type lithium ion secondary battery having a negative electrode sheet / separator / positive electrode sheet assembly (hereinafter sometimes referred to as an electrode sheet / separator assembly) is obtained. It was.

  Table 1 shows the adhesion between the separator and the electrode sheet in the electrode sheet / separator laminate used in the production of the battery, together with the discharge load characteristics and heat resistance of the battery.

Example 2
In Example 1, a solution of a crosslinkable polymer / crosslinking agent / foaming agent mixture was applied onto a peelable sheet made of a polyester film subjected to a release treatment, and dried to form a crosslinkable polymer sheet having a thickness of 12 μm on the peelable sheet. A separator made of a foam sheet of a reactive polymer was obtained in the same manner as in Example 1 except that it was obtained, and an electrode sheet / separator laminate was obtained using this separator, and a coin-type lithium ion secondary was obtained using this separator. A battery was obtained.

  Table 1 shows the gel fraction, thickness, foaming ratio, foaming diameter, and degree of swelling of the separator, and further, the separator in the electrode sheet / separator laminate used for the battery discharge load characteristics, heat resistance, and battery production. Table 1 shows the adhesion between the electrode sheet and the electrode sheet.

Example 3
In Example 1, except that 3 parts by weight of trifunctional isocyanate was used, a separator made of a foamed sheet of a reactive polymer was obtained in the same manner as in Example 1, and an electrode sheet / separator laminate was obtained using this separator. This was used to obtain a coin-type lithium ion secondary battery.

  Table 1 shows the gel fraction, thickness, foaming ratio, foaming diameter, and degree of swelling of the separator, and further, the separator in the electrode sheet / separator laminate used for the battery discharge load characteristics, heat resistance, and battery production. Table 1 shows the adhesion between the electrode sheet and the electrode sheet.

Example 4
(Preparation of crosslinkable polymer)
Acrylyl morpholine 15 parts by weight Acrylonitrile 10 parts by weight Methacrylic acid 5 parts by weight Butyl acrylate 70 parts by weight Azobisisobutyronitrile 0.3 part by weight Ethyl acetate 150 parts by weight

A solution of a crosslinkable polymer having a concentration of 20% by weight was obtained in the same manner as in Reference Example 1 except that the monomer, polymerization initiator, and solvent were used. This crosslinkable polymer had a weight average molecular weight of 4.5 × 10 ⁵ and a glass transition temperature of −10 ° C.

(Manufacture of separators and batteries)
2 parts by weight of trifunctional isocyanate obtained by adding 3 parts by weight of toluene diisocyanate to 1 part by weight of trimethylolpropane, 5 parts by weight of a foaming agent (Neocelbon 1000S manufactured by Eiwa Chemical Industry Co., Ltd.), 3 parts by weight of zinc oxide and fine silica powder 1 part by weight was added to 100 parts by weight of the crosslinkable polymer in the ethyl acetate solution of the crosslinkable polymer to obtain a solution of a crosslinkable polymer / crosslinking agent / foaming agent mixture.

  This crosslinkable polymer / crosslinking agent / foaming agent mixture solution was applied onto a release film having a thickness of 40 μm made of a release-treated polyester film, dried at 70 ° C., and then having a thickness of 3 μm on the release sheet. A sheet was obtained. On this crosslinkable polymer sheet on the peelable sheet, a peelable sheet having a thickness of 40 μm made of the same polyester film as described above was further superposed, and the resulting laminate was heated at 150 ° C. for 10 minutes to obtain a foamed sheet. It was. Thereafter, this is further placed in a thermostatic chamber at 50 ° C. for 3 days, the carboxyl group of the crosslinkable polymer forming the foamed sheet is reacted with the above trifunctional isocyanate and partially crosslinked, and the reactive polymer is foamed. A laminate including a separator made of a sheet was obtained, and an electrode sheet / separator laminate was obtained using this laminate in the same manner as in Example 1.

(Assembly of battery and evaluation of battery performance)
In an argon-substituted glove box, electrolyte salt lithium hexafluorophosphate (LiPF ₆ ) was dissolved in an ethylene carbonate / ethyl methyl carbonate mixed solvent (volume ratio 1/2) to a concentration of 1.2 mol / L. An electrolyte solution was prepared. Furthermore, 0.2 part by weight of N, N, N ′, N′-tetraglycidyl-m-xylenediamine, which is a tetrafunctional epoxy compound, was dissolved in 100 parts by weight of the electrolytic solution.

  The electrode sheet / separator laminate is charged into a 2016-size coin-type battery can serving also as a positive / negative electrode plate, and an electrolyte solution in which the tetrafunctional epoxy compound is dissolved is injected into the coin-type battery can. The can was sealed and the work in process was made. Thereafter, this work-in-process is put into a thermostatic chamber at a temperature of 50 ° C. for 7 days to cause the reactive polymer in the electrode / separator laminate to undergo a crosslinking reaction with the tetrafunctional epoxy compound at its unreacted carboxyl group. The positive and negative electrode sheets were bonded to and integrated with the separator, thus obtaining a coin-type lithium ion secondary battery having an electrode sheet / separator assembly.

  Table 1 shows the gel fraction, thickness, foaming ratio, foaming diameter, and degree of swelling of the separator, and further, the separator in the electrode sheet / separator laminate used for the battery discharge load characteristics, heat resistance, and battery production. Table 1 shows the adhesion between the electrode sheet and the electrode sheet.

Example 5
100 g of an ethyl acetate solution of the crosslinkable polymer obtained in Example 1 was placed in a flask, and n-heptane was dropped into the flask while stirring to take out the precipitated polymer. After such reprecipitation purification operation was further repeated twice, the resulting crosslinkable polymer was dried under reduced pressure, and thus the crosslinkable polymer was purified. The weight average molecular weight of the crosslinkable polymer thus purified was 5.0 × 10 ⁵ , and the glass transition temperature was 68 ° C. This crosslinkable polymer was dissolved in ethyl acetate to obtain a 20 wt% ethyl acetate solution.

(Preparation of separator)
1 part by weight of trifunctional isocyanate obtained by adding 3 parts by mole of hexamethylene diisocyanate to 1 part by weight of trimethylolpropane, 5 parts by weight of a foaming agent (Neocelbon 1000S manufactured by Eiwa Kasei Kogyo Co., Ltd.), 3 parts by weight of zinc oxide and fine silica 1 part by weight of the powder is added to 100 parts by weight of the crosslinkable polymer in an ethyl acetate solution of the crosslinkable polymer to obtain a solution of the crosslinkable polymer / crosslinking agent / foaming agent mixture. Using the solution of the agent mixture, an electrode sheet / separator laminate was obtained in the same manner as in Example 1. Subsequently, using this electrode sheet / separator laminate, a coin-type lithium ion secondary battery was obtained in the same manner as in Example 1.

  Table 1 shows the adhesion between the separator and the electrode sheet in the electrode sheet / separator laminate used in the production of the battery, together with the discharge load characteristics and heat resistance of the battery.

Example 6
1 part by weight of trifunctional isocyanate obtained by adding 3 parts by mole of hexamethylene diisocyanate to 1 part by weight of trimethylolpropane, 5 parts by weight of a blowing agent (Neocelbon 1000S manufactured by Eiwa Kasei Kogyo Co., Ltd.), 3 parts by weight of zinc oxide, and silica fine particles 1 part by weight of powder is acrylic modified fluororesin varnish (Cefal Coat FG730B manufactured by Central Glass Co., Ltd., solid content 40% by weight, hydroxyl value 8 mgKOH / g, weight average molecular weight of acrylic modified fluororesin is about 200,000, glass transition temperature of coating film (75 ° C.) 60 parts by weight of toluene together with 20 parts by weight of toluene to obtain a solution of a crosslinkable polymer / crosslinking agent / foaming agent mixture. In the same manner as in Example 1, an electrode sheet / separator laminate was obtained. Subsequently, using this electrode sheet / separator laminate, a coin-type lithium ion secondary battery was obtained in the same manner as in Example 1.

  Table 1 shows the adhesion between the separator and the electrode sheet in the electrode sheet / separator laminate used in the production of the battery, together with the discharge load characteristics and heat resistance of the battery.

Comparative Example 1
3 parts by weight of hexamethylene diisocyanate added to 1 part by mole of trimethylolpropane 1 part by weight of trifunctional isocyanate, 5 parts by weight of foaming agent (Neocelbon 1000S manufactured by Eiwa Kasei Kogyo Co., Ltd.), 3 parts by weight of zinc oxide and fine silica One part by weight of the powder was added to 100 parts by weight of the crosslinkable polymer to the solution of the crosslinkable polymer having a concentration of 20% by weight obtained in Example 1 to obtain a solution of a crosslinkable polymer / crosslinker mixture.

  The solution of this crosslinkable polymer / foaming agent mixture was applied onto a peelable polyester film having a thickness of 40 μm and dried at 70 ° C., and the crosslinkable polymer / foaming agent having a thickness of 3 μm was coated on the peelable sheet. A sheet made of the mixture was obtained. A 40 μm thick peelable sheet made of the same polyester film as described above was further superimposed on the above sheet on the peelable sheet, and the resulting laminate was heated at 150 ° C. for 10 minutes to obtain a foamed sheet.

  Next, one peelable sheet is peeled and removed from the laminate, a separator is exposed on the other peelable sheet, the positive electrode sheet is overlaid on the surface of the separator, and a heat bonding roll having a temperature of 85 ° C. The positive electrode sheet was pressure-bonded to the separator. Next, the other peelable sheet is peeled and removed to expose the back surface of the separator, and the negative electrode sheet is overlaid on the back surface of the separator. Similarly, using a heat bonding roll at a temperature of 85 ° C., the separator The negative electrode sheet was pressure-bonded to the electrode sheet / separator laminate.

In an argon-substituted glove box, electrolyte salt lithium hexafluorophosphate (LiPF ₆ ) was dissolved in an ethylene carbonate / ethyl methyl carbonate mixed solvent (volume ratio 1/2) to a concentration of 1.2 mol / L. An electrolyte solution was prepared. Furthermore, 1 part by weight of trifunctional isocyanate obtained by adding 3 parts by mole of toluene diisocyanate to 1 part by weight of trimethylolpropane was dissolved in 100 parts by weight of the electrolytic solution.

  The electrode sheet / separator laminate is charged into a 2016-size coin-type battery can that also serves as a positive and negative electrode plate, and an electrolyte solution in which the trifunctional isocyanate is dissolved is poured into the coin-type battery can. The work in process was made. Thereafter, this work-in-process is put into a thermostatic chamber at a temperature of 50 ° C. for 7 days, and the reactive polymer in the electrode / separator laminate is cross-linked with the trifunctional isocyanate at its unreacted hydroxyl group, Positive and negative electrode sheets were bonded and integrated with the separator, and thus a coin-type lithium ion secondary battery having an electrode sheet / separator assembly was obtained.

  Table 1 shows the adhesion between the separator and the electrode sheet in the electrode sheet / separator laminate used in the production of the battery, together with the discharge load characteristics and heat resistance of the battery.

Comparative Example 2
A solution of a crosslinkable polymer / crosslinking agent / foaming agent mixture was obtained in the same manner as in Example 1, except that 10 parts by weight of trifunctional isocyanate was added to 100 parts by weight of the ethyl acetate solution of the crosslinkable polymer. A coin-type lithium ion secondary battery was obtained in the same manner as in Example 1 except that this was used. Table 1 shows the adhesion between the separator and the electrode sheet in the electrode sheet / separator laminate used in the production of the battery, together with the discharge load characteristics and heat resistance of the battery.

Comparative Example 3
1 part by weight of a trifunctional isocyanate obtained by adding 3 parts by mole of hexamethylene diisocyanate to 1 part by weight of trimethylolpropane was added to 100 parts by weight of the crosslinkable polymer in an ethyl acetate solution of the above crosslinkable polymer. A solution of the crosslinker mixture was obtained.

  This crosslinkable polymer / crosslinking agent mixture solution was applied onto a peelable polyester film having a thickness of 40 μm and dried at 70 ° C., and the crosslinkable polymer / crosslinking agent having a thickness of 3 μm was coated on the peelable sheet. A sheet made of the mixture was obtained.

  Thereafter, the sheet made of the crosslinkable polymer / crosslinking agent mixture is placed in a thermostatic chamber at 50 ° C. for 3 days, the hydroxy group of the crosslinkable polymer is reacted with the trifunctional isocyanate, and partially crosslinked to be reactive. A laminate was obtained which was a polymer and thus contained a separator consisting of a sheet of reactive polymer.

  Next, one peelable sheet is peeled and removed from the laminate, the separator is exposed on the other peelable sheet, the positive electrode sheet is overlaid on the surface of the separator, and a heat bonding roll having a temperature of 85 ° C. The positive electrode sheet was pressure-bonded to the separator. Next, the other peelable sheet is peeled and removed to expose the back surface of the separator, and the negative electrode sheet is overlaid on the back surface of the separator. Similarly, using a heat bonding roll at a temperature of 85 ° C., the separator The negative electrode sheet was pressure-bonded to the electrode sheet / separator laminate.

  A coin-type lithium ion secondary battery having an electrode sheet / separator assembly was obtained in the same manner as in Example 1 except that this electrode sheet / separator laminate was used. Table 1 shows the adhesion between the separator and the electrode sheet in the electrode sheet / separator laminate used in the production of the battery, together with the discharge load characteristics and heat resistance of the battery.

Comparative Example 4
In Example 1, a solution of a crosslinkable polymer / crosslinking agent / foaming agent mixture was obtained, and a sheet of 0.2 mm thick crosslinkable polymer / crosslinking agent / foaming agent mixture was obtained using this solution. Thereafter, a coin-type lithium ion secondary battery having an electrode sheet / separator assembly was obtained in the same manner as in Example 1 except that a sheet composed of the crosslinkable polymer / crosslinking agent / foaming agent mixture was used. Table 1 shows the adhesion between the separator and the electrode sheet in the electrode sheet / separator laminate used in the production of the battery, together with the discharge load characteristics and heat resistance of the battery.

  As shown in Table 1, the battery separator according to the present invention is excellent in adhesion to the electrode sheet, and thus provides a high-performance battery excellent in heat resistance.

  On the other hand, according to Comparative Example 1, the crosslinkable polymer was previously made into a foam sheet without being partially crosslinked, and an electrode sheet was pressure-bonded to the electrode sheet / separator laminate. Therefore, in the obtained battery, the adhesiveness between a separator and an electrode sheet is inferior, and therefore the obtained battery is inferior in heat resistance.

According to Comparative Example 2, as a result of excessive crosslinking of the crosslinkable polymer, the swelling degree of the separator made of the foamed sheet of the reactive polymer is remarkably small, and particularly, the adhesion between the separator and the electrode sheet is inferior. Also, heat resistance is poor. Further, according to Comparative Example 3, the separator is made of a sheet that does not cause the reactive polymer to be foamed. Therefore, the adhesion between the separator and the electrode sheet and the heat resistance of the battery are excellent, but the battery performance is insufficient. It is. According to Comparative Example 4, since the separator is too thick, the battery performance is not sufficient.

Claims (3)

  A cross-linking agent made of a polyfunctional compound having reactivity with the functional group is reacted so that a part of the functional group reacts with the cross-linkable polymer having a functional group, and the cross-linkable polymer is partially cross-linked. A battery separator comprising a foamed sheet of a reactive polymer.   The battery separator according to claim 1, wherein the crosslinkable polymer having a functional group has at least one functional group selected from a hydroxy group, a carboxyl group, and an epoxy group. An electrode sheet is laminated on the separator according to claim 1 or 2 and pressed to form an electrode sheet / separator laminate. After the laminate is charged into a battery container, the reactive polymer that forms the separator is formed. An electrolyte solution in which a crosslinking agent composed of a polyfunctional compound having reactivity with a functional group is dissolved is injected into the battery container, the reactive polymer is further crosslinked, and the electrode sheet is adhered to the separator. A battery manufacturing method.