JP5260075B2 - Reactive polymer-supported porous film for battery separator and electrode / separator assembly obtained therefrom - Google Patents

Description

  The present invention relates to a reactive polymer-supported porous film for a battery separator and an electrode / separator assembly obtained therefrom.

  In recent years, lithium ion secondary batteries having a high energy density have been widely used as power sources for small to portable electronic devices such as mobile phones and notebook personal computers. Such a lithium ion secondary battery is obtained by laminating or winding sheet-like positive and negative electrodes and, for example, a polyolefin resin porous film, and charging the battery into a battery container made of, for example, a metal can. It is manufactured through a process of injecting an electrolytic solution into a container, sealing, and sealing.

  However, in recent years, there has been a strong demand for further downsizing and weight reduction of the above-described small or portable electronic devices. Therefore, further thinning and weight reduction of lithium ion secondary batteries are also required. In place of the conventional metal can container, a laminate seal type battery container is also used.

  According to such a laminated seal type battery container, since the surface pressure for maintaining the electrical connection between the separator and the electrode cannot be sufficiently applied to the electrode surface as compared with the conventional metal can container, Due to the expansion and contraction of the electrode active material during charging and discharging, the distance between the electrodes partially increases with time, the internal resistance of the battery increases, the battery characteristics deteriorate, and the resistance varies within the battery. However, there arises a problem that the battery characteristics deteriorate.

  Further, when manufacturing a sheet battery having a large area, the distance between the electrodes cannot be kept constant, and there is a problem that battery characteristics cannot be sufficiently obtained due to variations in resistance inside the battery.

  Therefore, conventionally, in order to solve such problems, it has been proposed to join an electrode and a separator by an adhesive resin layer comprising an electrolyte phase, a polymer gel layer containing an electrolyte solution, and a polymer solid layer. (For example, refer to Patent Document 1). In addition, after applying a binder resin solution containing polyvinylidene fluoride resin as a main component to the separator, an electrode is superimposed on the separator and dried to form a battery laminate, and after charging the battery laminate into a battery container, It has also been proposed to obtain a battery in which an electrolyte is injected into a battery container and an electrode is bonded to a separator (see, for example, Patent Document 2).

  Further, the separator impregnated with the electrolytic solution and the positive and negative electrodes are joined and adhered by the porous adhesive resin layer, and the electrolytic solution is held in the through-hole in the adhesive resin layer, thereby separating the separator. It has also been proposed to use a battery in which an electrode is bonded to the battery (see, for example, Patent Document 3).

However, according to such a method, in order to obtain a sufficient adhesive force between the separator and the electrode, the thickness of the adhesive resin layer must be increased, and the electrolytic solution for the adhesive resin Since the amount cannot be increased, the resulting battery has a problem that the internal resistance becomes high and the cycle characteristics and the high rate discharge characteristics cannot be sufficiently obtained.
JP-A-10-177865 Japanese Patent Laid-Open No. 10-189054 JP-A-10-172606

  The present invention has been made to solve the above-described problems in the production of a battery in which an electrode is bonded to a separator, and has sufficient adhesiveness with the electrode and is excellent in heat resistance. Another object of the present invention is to provide a reactive polymer-supported porous film for a battery separator that provides a battery with excellent safety at high temperatures.

  Furthermore, an object of the present invention is to provide an electrode / separator assembly obtained from such a crosslinkable polymer-supported porous film.

  According to the present invention, there is provided a reactive polymer-supported porous film for a battery separator in which a reactive polymer is supported on a porous film, the porous film comprising a polyolefin and a styrene-butadiene copolymer. A cross-linkable polymer comprising a cross-linked product of a resin composition comprising a gel fraction of 5% or more and having a plurality of reactive groups capable of reacting with isocyanate groups and a plurality of cationically polymerizable functional groups in the molecule. A reactive polymer-supported porous film for a battery separator is provided, wherein the reactive polymer is formed from a crosslinked polymer obtained by reacting with a polyfunctional isocyanate and crosslinking.

  Furthermore, according to the present invention, an electrode is laminated on the reactive polymer-supported porous film to obtain an electrode / reactive polymer-supported porous film laminate, which is charged into a battery container, and then a cationic polymerizable catalyst. An electrode / separator assembly obtained by contacting with an electrolyte solution containing

  A reactive polymer-supported porous film for a battery separator according to the present invention is a reactive polymer-supported porous film for a battery separator obtained by supporting a reactive polymer on a porous film, The film is made of a crosslinked resin composition containing a polyolefin and a styrene-butadiene copolymer, and has a gel fraction of 5% or more, and a reactive group capable of reacting with an isocyanate group in the molecule and cationic polymerization. The reactive polymer is formed from a cross-linked polymer obtained by reacting a cross-linkable polymer having a plurality of functional groups with a polyfunctional isocyanate for cross-linking.

  Therefore, an electrode is laminated on such a reactive polymer-supported porous film to form an electrode / reactive polymer-supported porous film laminate, which is charged into a battery container, and then an electrolytic solution containing a cationic polymerization catalyst is prepared. It is injected into the battery container, the reactive polymer of the electrode / reactive polymer-supported porous film laminate is brought into contact with the electrolytic solution, and the reaction is performed at least in the vicinity of the interface between the porous film and the electrode. At least a part of the conductive polymer is swollen in the electrolytic solution, or eluted into the electrolytic solution, and cationically polymerized to gel at least a part of the electrolytic solution, thereby firmly bonding the porous film and the electrode. Thus, an electrode / porous film assembly can be obtained.

  Furthermore, according to the reactive polymer-supported porous film of the present invention, since the reactive polymer is previously cross-linked, the reactivity is reduced when the electrode / reactive polymer-supported porous film laminate is immersed in the electrolytic solution. Elution and diffusion of the polymer from the electrode / reactive polymer-supported porous film laminate into the electrolyte solution is suppressed, and the reactive polymer swells. As a result, the electrode is used by using a small amount of the reactive polymer. Can be adhered to the porous film (separator), and the porous film has excellent ion permeability and functions well as a separator. Further, the reactive polymer is not excessively eluted and diffused in the electrolytic solution, and does not adversely affect the electrolytic solution.

  Thus, according to the present invention, an electrode / separator assembly having strong adhesion between the electrode / separator is formed in situ in the battery manufacturing process, and a battery having low internal resistance and excellent high rate characteristics can be easily obtained. Can get to.

  A reactive polymer-supported porous film for a battery separator according to the present invention is a reactive polymer-supported porous film for a battery separator obtained by supporting a reactive polymer on a porous film, The film is made of a crosslinked resin composition containing a polyolefin and a styrene-butadiene copolymer, and has a gel fraction of 5% or more, and a reactive group capable of reacting with an isocyanate group in the molecule and cationic polymerization. The reactive polymer is formed from a cross-linked polymer obtained by reacting a cross-linkable polymer having a plurality of functional groups with a polyfunctional isocyanate to cross-link it.

  In the reactive polymer-supported porous film for battery separator according to the present invention, the base porous film is a gel of 5% or more comprising a cross-linked product of a resin composition containing a polyolefin resin and a styrene-butadiene copolymer. It is a porous film having a fraction. Such a porous film is prepared by, for example, producing a porous film from a resin composition containing a polyolefin resin and a styrene-butadiene copolymer, heat-treating the film, or irradiating with an electron beam or an ultraviolet ray to form the double bond. Can be obtained by reacting to give a cross-linked structure.

  The polyolefin resin is preferably a polyethylene resin. For example, a high density polyethylene resin, an ultrahigh molecular weight polyethylene resin, or a mixture thereof is preferably used. The styrene-butadiene copolymer may be a random copolymer, but is preferably a block copolymer. The resin composition containing such a polyolefin resin and a styrene-butadiene copolymer may contain other resins as necessary in order to improve the molding processability and adhesion. An example of such a resin is a modified polyolefin resin obtained by graft polymerization of maleic anhydride onto polyethylene or polypropylene.

  In the present invention, such a porous film has a gel fraction of 5% or more. When the gel fraction is less than 5%, the film resistance at high temperatures is insufficient, and when the battery is exposed to high temperatures, the separator may be broken, leading to a short circuit of the electrodes. In the present invention, the gel fraction of the porous film is in the range of 5 to 90%, preferably in the range of 5 to 70%.

  According to the present invention, the porous film usually has pores having an average pore diameter of 0.01 to 5 μm and a porosity in the range of 20 to 95%. The porosity of the porous film is preferably in the range of 30 to 90%, and most preferably in the range of 40 to 85%. When the porosity of the porous film is too low, when used as a battery separator, the ion conduction path is reduced and sufficient battery characteristics cannot be obtained. On the other hand, when the porosity is too high, when used as a battery separator, the strength is insufficient, and in order to obtain the required strength, a thick substrate porous film must be used. This is not preferable because the internal resistance of the battery increases.

  Further, according to the present invention, the porous film usually has an air permeability of 1500 seconds / 100 cc or less, preferably 1000 seconds / 100 cc or less. When the air permeability is too high, ion conductivity is low when used as a battery separator, and sufficient battery characteristics cannot be obtained.

  The strength of the porous film is preferably 1 N or more in terms of piercing strength. This is because when the piercing strength is less than 1N, the base material may be broken when a surface pressure is applied between the electrodes, thereby causing an internal short circuit.

  In the present invention, the crosslinkable polymer refers to a polymer having a plurality of reactive groups capable of reacting with isocyanate groups (isocyanate reactive groups) and cationic polymerizable functional groups in the molecule, and thus such crosslinkable polymers. A reactive polymer can be obtained by reacting with a polyfunctional isocyanate as a crosslinking agent through the reactive group and crosslinking. The reactive polymer-supported porous film for a battery separator according to the present invention can be obtained by supporting the reactive polymer on the substrate porous film.

  According to the present invention, the isocyanate-reactive group is not particularly limited as long as it is a functional group having active hydrogen capable of reacting with an isocyanate group. For example, a hydroxyl group, a carboxyl group, an amino group, an imino group , A urethane group, a urea group, and the like. Among them, a hydroxyl group or a carboxyl group is preferable.

  Moreover, in this invention, the cationically polymerizable functional group which a crosslinkable polymer has is at least 1 sort (s) chosen from 3-oxetanyl group and an epoxy group.

  According to the present invention, such a crosslinkable polymer is preferably composed of a radical polymerizable monomer having an isocyanate-reactive group, a radical polymerizable monomer having a 3-oxetanyl group, and a radical polymerizable monomer having an epoxy group. It can be obtained by a radical copolymer of at least one selected radical polymerizable monomer and another radical polymerizable monomer.

  Particularly preferably, in the present invention, the crosslinkable polymer is a polymer having a plurality of isocyanate-reactive groups in the molecule and a plurality of 3-oxetanyl groups and epoxy groups as cationically polymerizable functional groups, or 3 in the molecule. -Refers to a polymer having a plurality of oxetanyl groups and epoxy groups. Therefore, such a crosslinkable polymer is preferably a radical polymerizable monomer having an isocyanate reactive group (an isocyanate reactive group-containing radical polymerizable monomer). ), A radical polymerizable monomer having a 3-oxetanyl group (3-oxetanyl group-containing radical polymerizable monomer), a radical polymerizable monomer having an epoxy group (epoxy group-containing radical polymerizable monomer), and other radical polymerizable monomers Radical copolymerization with monomer or isocyanate A refractory-containing radical polymerizable monomer, and any of the 3-oxetanyl group-containing radically polymerizable monomer and the epoxy group-containing radically polymerizable monomer, can be obtained by radical copolymerization of other radical polymerizable monomers.

  As described above, polymers having a 3-oxetanyl group or an epoxy group in the molecule are already known as described in, for example, JP-A Nos. 2002-110245 and 2001-176555.

  Examples of the isocyanate-reactive group-containing radical polymerizable monomer include carboxyl group-containing radical copolymerizable monomers such as (meth) acrylic acid, itaconic acid, maleic acid, 2-hydroxyethyl (meth) acrylate, 2- Mention may be made of hydroxyl group-containing radical copolymerizable monomers such as hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2-hydroxyhexyl (meth) acrylate, in particular hydroxylalkyl (meth) acrylate. . In the present invention, (meth) acrylate means acrylate or (meth) acrylate.

  According to the present invention, when obtaining a crosslinkable polymer having a cationic polymerizable functional group together with an isocyanate reactive group, the isocyanate reactive group-containing radical polymerizable monomer is 0.1 to 10% by weight of the total monomer amount, Preferably, it is used in a range of 0.5 to 5% by weight. When the isocyanate-reactive group-containing radical polymerizable monomer is more than 10% by weight of the total monomer amount, when the resulting crosslinkable polymer is reacted with a polyfunctional isocyanate to partially crosslink the crosslinkable polymer. In the electrode / porous film (separator) bonded body finally obtained, the reactive polymer is difficult to swell sufficiently in the electrolyte solution because the crosslink density is large and the resulting reactive polymer becomes dense. A battery with excellent characteristics cannot be obtained. However, conversely, when the isocyanate-reactive group-containing radical polymerizable monomer is less than 0.1% by weight of the total monomer amount, elution of the reactive polymer partially crosslinked with the crosslinkable polymer into the electrolyte solution, Diffusion is not sufficiently suppressed, and many of the reactive polymers are eluted and diffused in the electrolyte solution, so that sufficient adhesion cannot be obtained between the porous film and the electrode, and the characteristics are also excellent. I can't get a battery.

  According to the present invention, the 3-oxetanyl group-containing radical polymerizable monomer is preferably represented by the general formula (I)

(In the formula, R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.)
The 3-oxetanyl group containing (meth) acrylate represented by these is used.

  Specific examples of such a 3-oxetanyl group-containing (meth) acrylate include, for example, 3-oxetanylmethyl (meth) acrylate, 3-methyl-3-oxetanylmethyl (meth) acrylate, 3-ethyl-3-oxetanylmethyl ( Examples include meth) acrylate, 3-butyl-3-oxetanylmethyl (meth) acrylate, and 3-hexyl-3-oxetanylmethyl (meth) acrylate. These (meth) acrylates are used alone or in combination of two or more.

  Further, according to the present invention, the epoxy group-containing radical polymerizable monomer is preferably represented by the general formula (II)

(In the formula, R ₃ represents a hydrogen atom or a methyl group, and R ₄ represents the formula (1)

Or formula (2)

The epoxy group containing group represented by these is shown. )
The epoxy group containing (meth) acrylate represented by these is used.

  Specific examples of such an epoxy group-containing (meth) acrylate include, specifically, 3,4-epoxycyclohexylmethyl (meth) acrylate, glycidyl (meth) acrylate, and the like. These (meth) acrylates are used alone or in combination of two or more.

  According to the present invention, the other radical polymerizable monomer to be copolymerized with the isocyanate-reactive radical polymerizable monomer, the 3-oxetanyl group-containing radical polymerizable monomer and / or the epoxy group-containing radical polymerizable monomer is preferably represented by the general formula ( III)

(In the formula, R ₅ represents a hydrogen atom or a methyl group, A represents an oxyalkylene group having 2 or 3 carbon atoms (preferably an oxyethylene group or an oxypropylene group), and R ₆ represents 1 to 1 carbon atoms. 6 represents an alkyl group having 6 carbon atoms or a fluorinated alkyl group having 1 to 6 carbon atoms, and n represents an integer of 0 to 12.)
(Meth) acrylate represented by the general formula (IV)

(In the formula, R ₇ represents a methyl group or an ethyl group, and R ₈ represents a hydrogen atom or a methyl group.)
It is at least 1 sort (s) chosen from vinyl ester represented by these.

  Specific examples of the (meth) acrylate represented by the general formula (III) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2,2,2 -Trifluoroethyl (meth) acrylate, 2,2,3,3-tetrafluoropropyl (meth) acrylate, etc. can be mentioned.

  Besides these, for example,

Etc. In the formula, R ₅ represents a hydrogen atom or a methyl group, and n is an integer of 0 to 12.

  Specific examples of the vinyl ester represented by the general formula (IV) include vinyl acetate and vinyl propionate.

  As described above, the crosslinkable polymer having a plurality of 3-oxetanyl groups and / or epoxy groups together with an isocyanate-reactive group is preferably an isocyanate-reactive group-containing monomer and a 3-oxetanyl group and / or an epoxy-containing radically polymerizable polymer. A radical copolymer can be obtained by radical copolymerizing a monomer and another radical polymerizable monomer using a radical polymerization initiator. This radical copolymerization may be carried out by any polymerization method such as solution polymerization, bulk polymerization, suspension polymerization, emulsion polymerization, etc., but solution polymerization or suspension polymerization in terms of ease of polymerization, adjustment of molecular weight, post-treatment, etc. Is preferred.

  The radical polymerization initiator is not particularly limited, and examples thereof include N, N′-azobisisobutyronitrile, dimethyl N, N′-azobis (2-methylpropionate), and benzoyl peroxide. Lauroyl peroxide is used. In this radical copolymerization, a molecular weight modifier such as mercaptan can be used as necessary.

  According to the present invention, the crosslinkable polymer as described above is reacted with a polyfunctional isocyanate, and the reactive polymer obtained by crosslinking is supported on the substrate porous film, and an electrode is laminated thereon to form an electrode / porous structure. A film laminate, which is immersed in an electrolytic solution containing a cationic polymerization catalyst, preferably an electrolytic solution containing an electrolyte that also serves as a cationic polymerization catalyst, and the reactive polymer supported on the porous film is mixed with the electrolytic solution. Contact, swell at least part of the electrolyte, or elute and diffuse in the electrolyte, crosslink by cationic polymerization, and gel the electrolyte in the vicinity of the interface between the porous film and the electrode By this, the electrode and the porous film can be adhered.

  Therefore, according to the present invention, when obtaining a crosslinkable polymer containing a 3-oxetanyl group and / or an epoxy group together with an isocyanate-reactive group, a 3-oxetanyl group-containing radical polymerizable monomer and / or an epoxy group-containing radical polymerization is obtained. The sex monomers are used so that the total amount thereof is in the range of 5 to 50% by weight, preferably 10 to 30% by weight of the total monomer amount. Therefore, in the case of obtaining a crosslinkable polymer containing a 3-oxetanyl group, the 3-oxetanyl group-containing radical polymerizable monomer is in the range of 5 to 50% by weight, preferably 10 to 30% by weight of the total monomer amount. In the same manner, in the case of obtaining a crosslinkable polymer containing an epoxy group, the epoxy group-containing radical polymerizable monomer is 5 to 50% by weight, preferably 10 to 30% by weight of the total monomer amount. Used in a range.

  Further, a 3-oxetanyl group-containing radical polymerizable monomer and an epoxy group-containing radical polymerizable monomer are used in combination, and these are copolymerized with other radical polymerizable monomers to form an isocyanate-reactive group together with a 3-oxetanyl group and an epoxy group. In the case of obtaining a crosslinkable polymer having a ratio, the proportion of the epoxy group-containing radical polymerizable monomer in the total amount of the 3-oxetanyl group-containing radical polymerizable monomer and the epoxy group-containing radical polymerizable monomer is 90% by weight or less. Used as follows.

  When obtaining a 3-oxetanyl group-containing crosslinkable polymer or an epoxy group-containing crosslinkable polymer, the total amount of the 3-oxetanyl group-containing radical polymerizable monomer and the epoxy group-containing radical polymerizable monomer is more than 5% by weight of the total monomer amount. When the amount is small, as described above, the amount of the crosslinkable polymer required for gelation of the electrolytic solution is increased, so that the performance of the obtained battery is deteriorated. On the other hand, when it is more than 50% by weight, the retention property of the electrolyte solution of the formed gel is lowered, and the adhesion between the electrode / separator in the obtained battery is lowered.

  In the present invention, the crosslinkable polymer preferably has a weight average molecular weight of 10,000 or more. When the weight average molecular weight of the crosslinkable polymer is less than 10,000, a large amount of the crosslinkable polymer is required to gel the electrolytic solution, so that the characteristics of the obtained battery are deteriorated. On the other hand, the upper limit of the weight average molecular weight of the crosslinkable polymer is not particularly limited, but is about 3 million, preferably about 2.5 million so that the electrolytic solution can be held as a gel. In particular, according to the present invention, the crosslinkable polymer preferably has a weight average molecular weight in the range of 100,000 to 2,000,000.

  A reactive polymer-supported porous film for a battery separator according to the present invention is obtained by reacting a crosslinkable polymer as described above with a polyfunctional isocyanate and supporting the cross-linked reactive polymer on a substrate porous film. Is.

  According to the present invention, it is desirable that the reactive polymer obtained by crosslinking the crosslinkable polymer in this way has an insoluble content in the range of 5 to 80%. Here, the insoluble fraction is, as will be described later, a porous film carrying a crosslinked reactive polymer in an ethylene carbonate / diethyl carbonate (volume ratio 1/1) mixed solvent at room temperature with stirring for 2 hours. After dipping, the ratio of the reactive polymer remaining on the porous film when dipped in ethyl methyl carbonate.

  Although there is no limitation to obtain a reactive polymer having an insoluble fraction in the range of 5 to 80%, usually, the polyfunctional isocyanate has 1 mol part of the isocyanate-reactive group of the crosslinkable polymer. Crosslinkable polymer and polyfunctional in an appropriate solvent so that the isocyanate group has 0.1 to 10 mol parts, preferably 0.3 to 5 mol parts, particularly preferably 0.5 to 3 mol parts Isocyanate is mixed, preferably applied to the substrate porous film, dried, and then heated to cause the crosslinking reaction of the crosslinkable polymer until the resulting reactive polymer is characteristically stabilized. Can be obtained by:

  In the present invention, the crosslinkable polymer is reacted with the polyfunctional isocyanate, and the reactive polymer obtained by crosslinking is supported on the porous substrate film, for example, as described above, including the crosslinkable polymer and the polyfunctional isocyanate. The solution may be supported on the substrate porous film and then heated to cause the crosslinkable polymer to react with the crosslinking agent. However, the method is not particularly limited to this method.

  For example, the crosslinkable polymer solution may be applied to the porous film and dried, and then the crosslinkable polymer may be contacted with the polyfunctional isocyanate solution. After making it react and bridge | crosslink to make a reactive polymer, after applying the solution containing this reactive polymer to a peelable sheet and making it dry, you may transfer to a base material porous film.

  In particular, one preferred method according to the present invention is to apply a solution comprising both a crosslinkable polymer and a polyfunctional isocyanate to a peelable sheet and dry to form a crosslinkable polymer / polyfunctional isocyanate layer on the peelable sheet. After forming, the peelable sheet is superposed on the substrate porous film and heated and pressed to transfer the crosslinkable polymer / polyfunctional isocyanate layer to the substrate porous film, and then the crosslinkable polymer / polyfunctional isocyanate layer is transferred to the substrate porous film. Heating to an appropriate temperature forms a reactive polymer on the porous film.

  According to the present invention, as long as the resulting reactive polymer has the insoluble fraction, it is not always necessary to react all the isocyanate-reactive groups in the crosslinkable polymer with the polyfunctional isocyanate. The heat-curing temperature and the time for it depend on the crosslinkable polymer and polyfunctional isocyanate used, but these reaction conditions can be determined by experiments. Usually, when heated and reacted at a temperature of 50 ° C. for 48 hours, the crosslinking reaction is completed, and a reactive polymer having the above-mentioned insoluble fraction and stable in characteristics can be obtained.

  When the insoluble fraction of the reactive polymer is less than 5%, an electrode is pressure-bonded to a porous film supporting such a reactive polymer to form an electrode / porous film laminate, which is used as an electrolyte solution. When immersed, most of the reactive polymer elutes and diffuses into the electrolyte, and even if the reactive polymer is further cationically polymerized and crosslinked, effective adhesion can be obtained between the electrode and the porous film. Can not. On the other hand, when the insoluble fraction of the reactive polymer is more than 80%, an electrode / porous film laminate is formed, and when this is immersed in an electrolytic solution, the reactive polymer has low swelling and the resulting electrode / porous A battery having a quality film assembly has a high internal resistance, which is not preferable for battery characteristics. In particular, according to the present invention, the insoluble fraction of the reactive polymer is preferably in the range of 10-60%, and most preferably in the range of 10-40%.

  In the present invention, the polyfunctional isocyanate is not particularly limited. Aromatic, araliphatic, alicyclic, and aliphatic polyfunctional isocyanates such as isocyanate and tris (phenylisocyanate) thiophosphate, and multi-functional isocyanates of these isocyanates are used. A so-called isocyanate adduct obtained by adding such a polyol is also preferably used.

  As described above, according to the present invention, the reaction product obtained by reacting the crosslinkable polymer with the polyfunctional isocyanate and crosslinking, that is, the reactive polymer, is immersed in the electrolytic solution even in the electrolytic solution. Elution and diffusion are suppressed. Therefore, a reactive polymer having such an insoluble fraction of 5 to 80% is supported on a porous film, and an electrode is laminated thereon to form an electrode / reactive polymer-supported porous film laminate, which is a battery. After charging in the container, an electrolytic solution containing an electrolyte containing a cationic polymerization catalyst is injected into the battery container, and the reactive polymer of the electrode / reactive polymer-supported porous film laminate is brought into contact with the character electrolyte. Then, in the vicinity of the interface between the porous film and the electrode, a part of the reactive polymer swells in the electrolytic solution or elutes into the electrolytic solution, and the cationic polymerizable functional group causes the electrolytic solution. Cation polymerization catalyst, preferably cation polymerization with an electrolyte that also serves as a cation polymerization catalyst, gelling the electrolyte, and firmly bonding the electrode to the porous film with good adhesion, thus Electrode / porous film (i.e., a separator in a battery obtained) can be obtained joined body.

  Thus, according to the present invention, the reactive polymer is partially cross-linked in advance so as to have an insoluble content of 5 to 80%. Therefore, even when immersed in the electrolytic solution, the reactive polymer enters the electrolytic solution. Is prevented or reduced, and is effectively used for adhesion between the electrode and the porous film. By using a relatively small amount of the reactive polymer, the electrode and the porous film can be stabilized. In addition, it can be more firmly bonded.

  Furthermore, in a porous film carrying a cross-linked reactive polymer, the reactive polymer is stable in the absence of a cationic polymerization catalyst. Even if it preserves, it does not deteriorate.

  Next, a method for producing a battery according to the present invention using the reactive polymer-supported porous film thus obtained will be described.

  First, an electrode is laminated or wound on the reactive polymer-supported porous film to obtain an electrode / reactive polymer-supported porous film laminate, and then this laminate is a battery made of a metal can, a laminate film, or the like. In the case where it is necessary to weld the terminal and weld the terminal, etc., this is performed, and then a predetermined amount of an electrolytic solution in which the cationic polymerization catalyst is dissolved is injected into the battery container, and the battery container is sealed and sealed, A reactive polymer supported on a reactive polymer-supported porous film is brought into contact with the electrolytic solution, and at least a part thereof is swollen in the electrolytic solution in the vicinity of the interface between the porous film and the electrode, or the electrolytic solution It elutes and diffuses in, crosslinks by cationic polymerization, gels at least part of the electrolyte, adheres the electrode to the porous film, and thus separates the porous film. And data electrode to the separator can be obtained strongly adhered cells.

  In the present invention, the reactive polymer functions to cause the electrolyte solution to gel at least in the vicinity of the interface between the porous film and the electrode and to bond the electrode and the porous film by crosslinking by cationic polymerization. To do.

  In the present invention, the reactive polymer can be cationically polymerized and crosslinked at room temperature, although it depends on its structure, the amount supported on the porous film, and the type and amount of the cationic polymerization catalyst, but it is heated. Thus, cationic polymerization can be promoted. In this case, although it depends on the heat resistance and productivity of the material constituting the battery, the heating is usually performed at a temperature of about 40 to 100 ° C. for about 0.5 to 48 hours. In addition, in order to swell, elute or diffuse an amount of polymer sufficient to adhere the electrode to the porous film, the electrolyte may be poured into the battery container and then left at room temperature for several hours.

  In the present invention, the electrode / reactive polymer-supported porous film laminate only needs to have an electrode laminated on the reactive polymer-supported porous film. Therefore, depending on the structure and form of the battery, the electrode / reactive polymer Examples of the supported porous film laminate include negative electrode / porous film / positive electrode, negative electrode / porous film / positive electrode / porous film, and the like.

  The electrolytic solution is a solution obtained by dissolving an electrolyte salt in an appropriate 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 cationic components, hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid A salt containing an anionic component of an inorganic acid such as borohydrofluoric acid, hydrofluoric acid, hexafluorophosphoric acid or perchloric acid, or an organic acid such as carboxylic acid, organic sulfonic acid or fluorine-substituted organic sulfonic acid. it can. Among these, an electrolyte salt containing an alkali metal ion as a cation component is particularly preferably used.

  Specific examples of the electrolyte salt having such an alkali metal ion as a cation component include, for example, alkali perchlorate such as lithium perchlorate, sodium perchlorate, potassium perchlorate, lithium tetrafluoroborate, tetra Alkali metal tetrafluoroborate such as sodium fluoroborate and potassium tetrafluoroborate, alkali metal hexafluorophosphate such as lithium hexafluorophosphate and potassium hexafluorophosphate, alkali trifluoroacetate such as lithium trifluoroacetate Mention may be made of metals and alkali metals of trifluoromethane sulfonate such as lithium trifluoromethane sulfonate.

  In particular, when obtaining a lithium ion secondary battery according to the present invention, as the electrolyte salt, for example, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate or the like is preferably used.

  Furthermore, any solvent can be used as the solvent for the electrolyte salt used in the present invention as long as it dissolves the electrolyte salt. Examples of the non-aqueous solvent include ethylene carbonate and propylene carbonate. , Cyclic esters such as butylene carbonate and γ-butyrolactone, ethers such as tetrahydrofuran and dimethoxyethane, and chain esters such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, or a mixture of two or more thereof Can be used as

  Moreover, although the said electrolyte salt is suitably determined according to the kind and quantity of the solvent to be used, normally the quantity used as the density | concentration of 1 to 50 weight% is used in the obtained electrolyte solution.

  In the present invention, an onium salt is preferably used as the cationic polymerization catalyst. Examples of such onium salts include ammonium salts, phosphonium salts, arsonium salts, stibonium salts, iodonium salts, and other cationic components, tetrafluoroborate, hexafluorophosphate, trifluoromethanesulfonate, and perchloric acid. An onium salt comprising an anionic component such as a salt can be mentioned.

  However, according to the present invention, among the above-described electrolyte salts, in particular, lithium tetrafluoroborate and lithium hexafluorophosphate also function as a cationic polymerization catalyst, and thus also serve as an electrolyte salt. Are preferably used. In this case, either lithium tetrafluoroborate or lithium hexafluorophosphate may be used alone, or both may be used in combination.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. The characteristics of the porous film and the characteristics of the obtained battery were evaluated as follows.

(Thickness of porous film)
It was determined based on a measurement with a 1/10000 mm thickness gauge and a 10,000 times scanning electronic microscopic photograph of the cross section of the porous film.

(Porosity of porous film)
The weight was calculated from the weight W (g) per unit area S (cm ² ) of the porous film, the average thickness t (cm), and the density d (g / cm ³ ) of the resin constituting the porous film by the following equation.

Porosity (%) = (1− (100 W / S / t / d)) × 100
(Air permeability of porous film)
It calculated | required based on JISP8117.

(Puncture strength)
A piercing test was performed using a compression test kit KES-G5 manufactured by Kato Tech Co., Ltd. The maximum load was read from the load displacement curve obtained by the measurement, and the puncture strength was obtained. A needle having a diameter of 1.0 mm and a radius of curvature of the tip of 0.5 mm was used at a speed of 2 cm / second.

(Gel fraction of porous film)
A porous film cut out in a 10 cm square was folded and sandwiched between 5 cm × 10 cm metal meshes to prepare a 5 cm square sample. The initial weight P ₀ of this sample was measured. Subsequently, this sample was immersed in 100 mL of m-xylene (boiling point 139 ° C.) and then heated to boil xylene for 5 hours. Thereafter, the sample was taken out and dried, and the weight P after boiling xylene treatment was measured in this way, and the gel fraction R was measured from the following equation using these values.

R (%) = (P / P ₀ ) × 100
(Insoluble fraction of reactive polymer)
A reactive polymer layer-carrying porous film carrying a known amount A of a reactive polymer layer was weighed and its weight B was measured. Next, this reactive polymer layer-supported porous film was immersed in a mixed solvent of ethylene carbonate / diethyl carbonate (1/1 volume ratio) at room temperature for 2 hours, then immersed in ethyl methyl carbonate, washed, and air-dried. . Then, the reactive polymer layer carrying porous film processed in this way was weighed, and the weight C was measured. The insoluble fraction of the reactive polymer was calculated by the following formula.

Insoluble fraction (%) = ((A− (BC)) / A) × 100
(Measurement of electrode / separator adhesion)
About each battery obtained by the Example and the comparative example, it decomposed | disassembled before performing a charging / discharging test, and measured the adhesive force between an electrode sheet / separator. That is, the battery is disassembled and the electrode sheet / separator assembly is taken out. Next, the interface of the electrode sheet / separator assembly is peeled off 5 mm from the end, and the end of the electrode sheet and the separator are mutually oriented at 180 °. The load at that time was measured by pulling. This load was divided by the width of the electrode sheet / separator to obtain the adhesive force between the electrode sheet / separator.
(Battery high temperature storage test)
Each battery obtained in Examples and Comparative Examples was fixed to a battery holder, applied with a certain surface pressure, and left in a thermostat at 160 ° C. The positive and negative terminals of the battery were connected to an ohmmeter, and the time when the resistance indicated by the ohmmeter suddenly decreased was measured. The test was up to 60 minutes. After 60 minutes, the battery was taken out of the incubator and allowed to cool, then the battery was disassembled, the area of the separator was measured, and the shrinkage was measured. However, since the separator usually has a larger area than the electrode sheet, the separator protrudes outward from the periphery of the electrode sheet. Therefore, when the battery was disassembled, the shrinkage rate was set to 0% when the area of the separator was equal to the area of the electrode sheet. Therefore, for example, if the area of the separator contracts to 80% of the area of the electrode sheet, the contraction rate of the separator in this case is 20%.

Reference example 1
(Preparation of electrode sheet)
85 parts by weight of lithium cobaltate (Nippon Chemical Industry Co., Ltd., Cellseed C-10) as a positive electrode active material and 10 parts by weight of acetylene black (Denka Black from Denki Kagaku Kogyo Co., Ltd.) as a conductive additive and a binder. 5 parts by weight of vinylidene fluoride resin (KF Polymer L # 1120 manufactured by Kureha Chemical Industry Co., Ltd.) was mixed, and this was made into a slurry using N-methyl-2-pyrrolidone so as to have a solid concentration of 15% by weight. .

  This slurry was applied to an aluminum foil (current collector) having a thickness of 20 μm to a thickness of 200 μm, dried at 80 ° C. for 1 hour, and then at 120 ° C. for 2 hours, and then pressed by a roll press, so that the thickness of the active material layer was A 100 μm positive electrode sheet was prepared.

  In addition, 80 parts by weight of mesocarbon microbeads (MCMB6-28 manufactured by Osaka Gas Chemical Co., Ltd.) as a negative electrode active material, 10 parts by weight of acetylene black (Denka Black manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive auxiliary agent, and a binder 10 parts by weight of vinylidene fluoride resin (KF Polymer L # 1120 manufactured by Kureha Chemical Industry Co., Ltd.) is mixed, and this is slurried with N-methyl-2-pyrrolidone so as to have a solid concentration of 15% by weight. It was.

  This slurry was applied to a copper foil (current collector) having a thickness of 20 μm to a thickness of 200 μm, dried at 80 ° C. for 1 hour, dried at 120 ° C. for 2 hours, and then pressed by a roll press to form an active material layer. A negative electrode sheet having a thickness of 100 μm was prepared.

Production Example 1
(Production of crosslinkable polymer A (hydroxyethyl methacrylate monomer component 5% by weight and 3-oxetanyl group-containing monomer component 25% by weight))
In a 500 mL three-necked flask equipped with a reflux condenser, methyl methacrylate 56.0 g, (3-ethyl-3-oxetanyl) methyl methacrylate 20.0 g, 2-hydroxyethyl methacrylate 4.0 g, ethyl acetate 158.0 g and N, N′-azobisisobutyronitrile (0.18 g) was added, and the mixture was stirred and mixed for 30 minutes while introducing nitrogen gas, and then heated to 70 ° C.

  When about 1 hour had passed, the viscosity of the reaction mixture began to rise, and then polymerization was carried out for 8 hours. Next, the mixture was cooled to about 40 ° C., 0.18 g of N, N′-azobisisobutyronitrile was added again, the mixture was heated again to 70 ° C., and further post-polymerization was performed for 8 hours. Then, it cooled to about 40 degreeC, 295 g of ethyl acetate was added, and it stirred and mixed until the whole became uniform, and the ethyl acetate solution (15 weight% density | concentration) of the crosslinkable polymer A was obtained.

  Next, 100 g of this crosslinkable polymer solution was added to 600 mL of methanol while stirring with a high-speed mixer to precipitate the crosslinkable polymer. The crosslinkable polymer was separated by filtration and washed with methanol several times, then put into a drying tube, and dried by passing dry nitrogen gas (dew point temperature −150 ° C. or lower) in which liquid nitrogen was vaporized. Furthermore, it was vacuum-dried in a desiccator for 6 hours to obtain a crosslinkable polymer A.

  This crosslinkable polymer was a pure white powder. As a result of molecular weight measurement by GPC, the weight average molecular weight was 308,000, and the number average molecular weight was 155000.

Production Example 2
(Production of crosslinkable polymer B, hydroxyethyl methacrylate monomer component 2% by weight and 3-oxetanyl group-containing monomer component 25% by weight)
In the same manner as in Production Example 1, 58.4 g of methyl methacrylate, 20.0 g of (3-ethyl-3-oxetanyl) methyl methacrylate, 1.6 g of 2-hydroxyethyl methacrylate, 158 g of ethyl acetate and N, N′-azobisiso 0.20 g of butyronitrile was added, mixed with stirring for 30 minutes while introducing nitrogen gas, and then heated to 70 ° C.

  When about 1 hour had passed, the viscosity of the reaction mixture began to rise, and then polymerization was carried out for 8 hours. Next, the mixture was cooled to about 40 ° C., 0.20 g of N, N′-azobisisobutyronitrile was added again, the mixture was heated again to 70 ° C., and further post-polymerization was performed for 8 hours. Then, it cooled to about 40 degreeC, 295 g of ethyl acetate was added, and it stirred and mixed until the whole became uniform, and the ethyl acetate solution (15 weight% density | concentration) of the crosslinkable polymer B was obtained.

  Then, it processed like the manufacture example 1, and the crosslinkable polymer B was obtained. This crosslinkable polymer was a pure white powder. As a result of molecular weight measurement by GPC, the weight average molecular weight was 314,000 and the number average molecular weight was 160000.

Production Example 3
(Production of crosslinkable polymer C, 2-hydroxyethyl methacrylate monomer component 5% by weight and 3-oxetanyl group-containing monomer component 20% by weight)
In the same manner as in Production Example 1, 48.0 g of methyl methacrylate, 32.0 g of (3-ethyl-3-oxetanyl) methyl methacrylate, 4.0 g of 2-hydroxyethyl methacrylate, 158 g of ethyl acetate and N, N′-azobisiso 0.16 g of butyronitrile was added, and the mixture was stirred and mixed for 30 minutes while introducing nitrogen gas, and then heated to 70 ° C.

  When about 1 hour had passed, the viscosity of the reaction mixture began to rise, and then polymerization was carried out for 8 hours. Subsequently, it cooled to about 40 degreeC, N, N'- azobisisobutyronitrile 0.16g was added again, and it heated again at 70 degreeC, and also post-polymerized for 8 hours. Then, it cooled to about 40 degreeC, 295 g of ethyl acetate was added, and it stirred and mixed until the whole became uniform, and the ethyl acetate solution (15 weight% density | concentration) of the crosslinkable polymer C was obtained. Then, it processed like the manufacture example 1, and the crosslinkable polymer C was obtained. This crosslinkable polymer was a pure white powder. As a result of molecular weight measurement by GPC, the weight average molecular weight was 347000, and the number average molecular weight was 166000.

Production Example 4
(Production of crosslinkable polymer D, 4-hydroxybutyl acrylate component 0.84% by weight and 3-oxetanyl group-containing monomer component 24% by weight, epoxy group-containing monomer component 1% by weight)
In the same manner as in Production Example 1, 50.4 g of methyl methacrylate, 11.89 g of 2-methoxyethyl acrylate, 20.16 g of (3-ethyl-3-oxetanyl) methyl methacrylate, 0.84 g of 3,4-epoxycyclohexylmethyl acrylate, 4-hydroxybutyl acrylate (0.706 g), ethyl acetate (158 g) and N, N′-azobisisobutyronitrile (0.16 g) were added, and the mixture was stirred and mixed for 30 minutes while introducing nitrogen gas, and then heated to 70 ° C. .

  When about 1 hour had passed, the viscosity of the reaction mixture began to rise, and then polymerization was carried out for 8 hours. Subsequently, it cooled to about 40 degreeC, N, N'- azobisisobutyronitrile 0.16g was added again, and it heated again at 70 degreeC, and also post-polymerized for 8 hours. Then, it cooled to about 40 degreeC, ethyl acetate 38g was added, and it stirred and mixed until the whole became uniform, and the ethyl acetate solution (30 weight% density | concentration) of the crosslinkable polymer D was obtained. Then, it processed like the manufacture example 1, and the crosslinkable polymer D was obtained. This crosslinkable polymer was a pure white powder. As a result of molecular weight measurement by GPC, the weight average molecular weight was 248,000, and the number average molecular weight was 57,000.

Production Example 5
(Preparation of porous film A)
Styrene-butadiene block copolymer (JSR Co., Ltd. JSR-TR2601K, styrene content 30 wt%) 5 wt%, modified polyolefin resin (Nippon Polyethylene Co., Ltd. Adtex DH0200, melting point 135 ° C.) 28.5 wt% %, A resin composition consisting of 66.5% by weight of ultra high molecular weight polyethylene having a weight average molecular weight of 2 million and 85 parts by weight of liquid paraffin are uniformly mixed in a slurry state, and at 160 ° C. using a small kneader, Dissolved and kneaded for 60 minutes. Thereafter, the kneaded product was sandwiched between metal plates cooled to 0 ° C. and rapidly cooled to obtain a resin sheet. Subsequently, this resin sheet was heat-pressed at 115 ° C. until the thickness became 0.4 mm, and further press-molded at 20 ° C. while maintaining the above thickness.

  Next, the obtained resin sheet was biaxially stretched 4.0 × 4.0 times in length and width simultaneously at a temperature of 120 ° C. and a speed of 10 mm / second, and then desolvated with heptane to obtain a porous film. It was. This porous film was heat-treated in air at 85 ° C. for 12 hours, and then heat-treated at 126 ° C. for 3 hours to obtain a porous film A. This porous film A had a film thickness of 21 μm, a porosity of 44%, an air permeability of 186 seconds / dL, a puncture strength of 239 gf, and a gel fraction of 12.4%.

Production Example 6
(Preparation of porous film B)
The same styrene-butadiene block copolymer as in Production Example 1 2.5% by weight, high-density polyethylene (melting point 135 ° C.) 29.3% by weight, ultrahigh molecular weight polyethylene having a weight average molecular weight of 2 million 68.2% by weight 15 parts by weight of the resin composition and 85 parts by weight of liquid paraffin were uniformly mixed in a slurry state, and dissolved and kneaded for 60 minutes at 160 ° C. using a small kneader. Thereafter, the kneaded product was sandwiched between metal plates cooled to 0 ° C. and rapidly cooled to obtain a resin sheet. The resin sheet was heat-pressed at 115 ° C. until the thickness became 0.4 mm, and further press-molded at 20 ° C. while maintaining the thickness.

  Next, the obtained resin sheet was biaxially stretched 4.0 × 4.0 times in length and width simultaneously at a temperature of 120 ° C. and a speed of 10 mm / second, and then desolvated with heptane to obtain a porous film. It was. This porous film was heat-treated in air at 85 ° C. for 12 hours, and then heat-treated at 126 ° C. for 3 hours to obtain a porous film B. This porous film B had a film thickness of 19 μm, a porosity of 50%, an air permeability of 167 seconds / dL, a piercing strength of 311 gf, and a gel fraction of 5.3%.

Production Example 7
(Preparation of porous film C)
The same styrene-butadiene block copolymer 5% by weight as in Production Example 1, modified polyolefin resin (Adtex DH0200 manufactured by Nippon Polyethylene Co., Ltd., melting point 135 ° C.) 28.5% by weight, ultra high molecular weight having a weight average molecular weight of 2 million 15 parts by weight of a resin composition composed of 66.5% by weight of polyethylene and 85 parts by weight of liquid paraffin were uniformly mixed in a slurry state, and dissolved and kneaded at 160 ° C. for 60 minutes using a small kneader. Thereafter, the kneaded product was sandwiched between metal plates cooled to 0 ° C. and rapidly cooled to obtain a resin sheet. The resin sheet was heat-pressed at 115 ° C. until the thickness became 0.4 mm, and further press-molded at 20 ° C. while maintaining the thickness.

Next, the obtained resin sheet was biaxially stretched 4.0 × 4.0 times in length and width simultaneously at a temperature of 120 ° C. and a speed of 10 mm / second, and then desolvated with heptane to obtain a porous film. It was. This porous film was heat-treated in air at 85 ° C. for 12 hours, and then heat-treated at 126 ° C. for 1 hour. Furthermore, this porous film was immersed in a benzophenone / methanol solution at a concentration of 0.1% by weight, and then irradiated with ultraviolet rays at a dose of 0.2 J / cm ² to obtain a porous film C. This porous film C had a film thickness of 20 μm, a porosity of 50%, an air permeability of 175 seconds / dL, a puncture strength of 229 gf, and a gel fraction of 62%.

Production Example 8
(Preparation of porous film D)
The same styrene-butadiene block copolymer 10% by weight as in Production Example 1, modified polyolefin resin (Nippon Polyethylene Co., Ltd. Adtex DH0200, melting point 135 ° C.) 27% by weight, ultrahigh molecular weight polyethylene 63 having a weight average molecular weight of 2 million 15 parts by weight of a resin composition comprising 85% by weight and 85 parts by weight of liquid paraffin were uniformly mixed in a slurry state and dissolved and kneaded for 60 minutes at 160 ° C. using a small kneader. Thereafter, the kneaded product was sandwiched between metal plates cooled to 0 ° C. and rapidly cooled to obtain a resin sheet. The resin sheet was heat-pressed at 115 ° C. until the thickness became 0.4 mm, and further press-molded at 20 ° C. while maintaining the thickness.

  Next, the obtained resin sheet was biaxially stretched 4.0 × 4.0 times in length and width simultaneously at a temperature of 120 ° C. and a speed of 10 mm / second, and then desolvated with heptane to obtain a porous film. It was. This porous film was heat-treated in air at 85 ° C. for 12 hours, and then heat-treated at 126 ° C. for 3 hours to obtain a porous film D. This porous film had a film thickness of 23 μm, a porosity of 46%, an air permeability of 275 seconds / dL, a puncture strength of 273 gf, and a gel fraction of 23%.

Production Example 9
(Preparation of porous film X)
15 parts by weight of a resin composition comprising 30.0% by weight of a modified polyolefin resin (Adtex DH0200 manufactured by Nippon Polyethylene Co., Ltd., melting point 135 ° C.), 70.0% by weight of ultrahigh molecular weight polyethylene having a weight average molecular weight of 2 million, and liquid paraffin 85 parts by weight were uniformly mixed in a slurry state, and melt kneaded for 60 minutes at 160 ° C. using a small kneader. Thereafter, the kneaded product was sandwiched between metal plates cooled to 0 ° C. and rapidly cooled to obtain a resin sheet. The resin sheet was heat-pressed at 115 ° C. until the thickness became 0.4 mm, and further press-molded at 20 ° C. while maintaining the thickness.

  Next, the obtained resin sheet was biaxially stretched 4.0 × 4.0 times in length and width simultaneously at a temperature of 120 ° C. and a speed of 10 mm / second, and then desolvated with heptane to obtain a porous film. It was. This porous film was heat-treated in air at 85 ° C. for 12 hours, and then heat-treated at 126 ° C. for 3 hours to obtain a porous film X. This porous film had a film thickness of 20 μm, a porosity of 41%, an air permeability of 200 seconds / dL, a puncture strength of 225 gf, and a gel fraction of 3%.

Production Example 10
(Preparation of porous film Y)
A slurry of 15 parts by weight of a resin composition comprising 30% by weight of a high-density polyethylene resin (3000B, Mitsui Chemicals Co., Ltd., melting point 135 ° C.) and 70% by weight of ultrahigh molecular weight polyethylene having a weight average molecular weight of 2 million and 85 parts by weight of liquid paraffin The mixture was uniformly mixed and dissolved and kneaded at 160 ° C. using a small kneader for 60 minutes. Thereafter, the kneaded product was sandwiched between metal plates cooled to 0 ° C. and rapidly cooled to obtain a resin sheet. The resin sheet was heat-pressed at 115 ° C. until the thickness became 0.4 mm, and further press-molded at 20 ° C. while maintaining the thickness.

  Next, the obtained resin sheet was biaxially stretched 4.0 × 4.0 times in length and width simultaneously at a temperature of 120 ° C. and a speed of 10 mm / second, and then desolvated with heptane to obtain a porous film. It was. This porous film was heat-treated in air at 85 ° C. for 12 hours, and then heat-treated at 126 ° C. for 3 hours to obtain a porous film Y. This porous film had a thickness of 20 μm, a porosity of 41%, an air permeability of 200 seconds / dL, a puncture strength of 225 gf, and a gel fraction of 0%.

Examples 1-11
(Preparation of reactive polymer-supported porous film)
100 parts by weight of the crosslinkable polymer in an ethyl acetate solution (10% by weight concentration) of the crosslinkable polymers A to D using a trifunctional isocyanate obtained by adding 3 parts by mole of hexamethylene diisocyanate to 1 part by mole of trimethylolpropane. The amount shown in Table 1 was added to each to obtain a solution of a crosslinkable polymer AD / crosslinking agent mixture.

After applying the solution of the crosslinkable polymer AD to the crosslinker mixture onto a peelable sheet made of a stretched polypropylene film and drying at 70 ° C., either one or both surfaces of the porous films AD And laminated with a heat laminating roll having a temperature of 90 ° C. Then, after putting in a thermostat at a temperature of 50 ° C. or 90 ° C. for 48 hours to crosslink the crosslinkable polymers A to D, the release sheet made of the stretched polypropylene film is removed, and the reactive polymers A to D Battery separators made of D / porous films A to D were obtained. In these battery separators, the amount of the reactive polymer supported on the porous film was 0.5 g / m ² .

  Along with the names of these battery separators, the crosslinkable polymer, the porous film, the amount of the crosslinking agent used for their production (parts by weight relative to 100 parts by weight of the crosslinkable polymer), and the porous crosslinkable polymer / crosslinking agent layer Bonding surface to film (single side or double side), crosslinkable polymer carrying amount of porous film (when carrying crosslinkable polymer on both sides of porous film), crosslinkable crosslinkable polymer Table 1 shows the heating temperature and heating time and the insoluble fraction of the resulting reactive polymer.

Comparative Examples 1-4
In the above Examples 1 to 11, the reactive polymer A or D / porous film X was used in the same manner except that the solution of the crosslinkable polymer A or D / crosslinking agent mixture was used and the porous film X or Y was used. Alternatively, a battery separator made of Y was obtained. In these battery separators, the amount of the reactive polymer supported on the porous film was 0.5 g / m ² .

  Along with the names of these battery separators, the crosslinkable polymer, the porous film, the amount of the crosslinking agent used for their production (parts by weight relative to 100 parts by weight of the crosslinkable polymer), and the porous crosslinkable polymer / crosslinking agent layer Bonding surface to film (single side or double side), crosslinkable polymer carrying amount of porous film (when carrying crosslinkable polymer on both sides of porous film), crosslinkable crosslinkable polymer Table 1 shows the heating temperature and heating time and the insoluble fraction of the resulting reactive polymer.

Examples 12-22
Each of the battery separators obtained in Examples 1 to 11 was sandwiched between the positive electrode and the negative electrode obtained in Reference Example 1, and further, the battery separator was pressure-bonded to the electrode by hot pressing at a temperature of 80 ° C. An electrode / separator laminate was obtained. At this time, the size of the battery separator was set to 1 mm at the portion protruding from the electrode.

  After the electrode / separator laminate was prepared in an aluminum laminate package, an electrolytic solution was injected into the package. Here, the electrolytic solution is prepared by dissolving lithium hexafluorophosphate at a concentration of 1.0 mol / L in a mixed solvent of ethylene carbonate / diethyl carbonate (volume ratio 1: 1). Next, after sealing the laminate package and leaving it to stand at room temperature for 12 hours, it is heated at 50 ° C. for 24 hours to react the cationic polymerizable functional group of the reactive polymer in the separator to further crosslink the reactive polymer. Then, the separator was adhered to the electrode, and thus a battery having an electrode / separator assembly was produced. Table 2 shows the adhesion force of the electrode / separator in these batteries and the results of the high-temperature storage test.

Comparative Examples 5-8
Batteries were produced in the same manner as in Examples 12 to 22 except that the battery separators obtained in Comparative Examples 1 to 4 were used. Table 3 shows the adhesion force of the electrode / separator in these batteries and the results of the high temperature storage test. All the batteries obtained had a short short circuit time.

Comparative Examples 9-12
Batteries were produced in the same manner as in Examples 12 to 22 except that the porous film A, C, X, or Y was used as the battery separator. Table 3 shows the adhesion force of the electrode / separator in these batteries and the results of the high temperature storage test. In any of the batteries obtained, the electrode / separator was not adhered, and the short circuit time was short.

Claims (6)

A reactive polymer-supported porous film for battery separators comprising a reactive polymer supported on a porous film, wherein the porous film is a crosslinked resin composition containing a polyolefin and a styrene-butadiene copolymer. A film having a gel fraction in the range of 5 to 23%, a radical polymerizable monomer having at least one reactive group selected from a hydroxyl group and a carboxyl group, and a radical polymerizable monomer having a 3-oxetanyl group A cross-linkable polymer that is a radical copolymer of a radical polymerizable monomer having at least one cationic polymerizable functional group selected from a radical polymerizable monomer having an epoxy group and another radical polymerizable monomer Reactivity mentioned above from crosslinked polymer obtained by reacting with isocyanate and crosslinking Reactive polymer-supported porous film for battery separator, characterized by Rimmer becomes. The reactive polymer-supported porous film for a battery separator according to claim 1, wherein the ratio of the styrene-butadiene copolymer in the porous film is in the range of 2.5 to 10% by weight. An electrode is laminated on the reactive polymer-supported porous film according to claim 1 or 2 to obtain an electrode / reactive polymer-supported porous film laminate, which is charged into a battery container, and a cationically polymerizable catalyst is obtained. The electrode / separator assembly obtained by making it contact with the electrolyte solution containing. The electrode / separator assembly according to claim 3 , wherein the cationic polymerization catalyst is an onium salt. The electrode / separator assembly according to claim 3 , wherein the electrolytic solution contains at least one selected from lithium hexafluorophosphate and lithium tetrafluoroborate as an electrolyte salt serving also as a cationic polymerization catalyst. A battery comprising the electrode / separator assembly according to claim 3 .