JP2007157569A - Manufacturing method of reactant polymer carrying porous film for battery separator and battery using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a reactant polymer-carrying porous film for a separator which, while having a sufficient adhesiveness between an electrode and a separator, has a low inner resistance and is suitable for manufacturing a battery with high rate characteristics, and a manufacturing method of a battery using the above reactant polymer-carrying porous film. <P>SOLUTION: The reactant polymer-carrying porous film for a battery separator is manufactured in a process in which a cross-linking polymer having in a molecule at least one kind of a first reactant group chosen from a hydroxy group, a carboxyl group and an amino group and a second reactant group having a cationic polymerizing property is made to react with a cross-linking agent having a reactant property with the above first reactant group, and partially, a cross-linked reactive polymer and lithium salt are carried on a porous film. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, a crosslinkable polymer having a first reactive group capable of reacting with a crosslinker in the molecule and a second reactive group having cationic polymerizable properties is reacted with a crosslinker to partially crosslink. A reactive polymer-supported porous film for a battery separator in which a reactive polymer and a lithium salt are supported on a porous film, and an electrode using such a reactive polymer-supported porous film. The present invention relates to a method of manufacturing a battery obtained by bonding a battery to a separator.

  In recent years, lithium ion secondary batteries having high energy density have been widely used as power sources for small 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 it into a battery container made of, for example, a metal can. It is manufactured through a process of injecting an electrolytic solution into a battery container, sealing, and sealing.

  However, in recent years, the demand for further miniaturization and weight reduction of the above-described small portable electronic devices is very strong. Therefore, further thinning and weight reduction of lithium ion secondary batteries are also demanded. In place of the conventional metal can container, a laminate film type battery container is also used.

  According to such a laminated film type battery container, 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 are deteriorated.

  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 a problem, an electrode and a separator are joined by an adhesive resin layer composed of a mixed phase of an electrolyte solution phase, a polymer gel layer containing an electrolyte solution, and a polymer solid phase. Has been proposed (see, for example, Patent Document 1). In addition, after applying a binder resin solution containing polyvinylidene fluoride resin as a main component to the separator, the electrode is superimposed on the separator and dried to form an electrode laminate, and the electrode laminate is charged into a battery container. It has also been proposed to obtain a battery in which an electrolytic solution is injected into a battery container and an electrode is adhered to a separator (see, for example, Patent Document 2).

  In addition, the separator impregnated with the electrolytic solution and the positive and negative electrodes are joined and adhered to each other with a porous adhesive resin layer, and the electrolytic solution is held in the through hole in the adhesive resin layer. It has also been proposed to use a battery in which an electrode is bonded to (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.

  Furthermore, as described above, in a battery in which a separator and an electrode are bonded using an adhesive resin, the adhesive strength between the separator and the electrode is lowered when placed in a high temperature environment. There is a risk of causing a short circuit between the electrodes due to contraction. In the battery, the adhesive resin is swollen by the electrolytic solution. However, compared to the electrolytic solution, electrolyte ions are less likely to diffuse into the adhesive resin, so the adhesive resin layer has a high internal resistance. Adversely affects battery characteristics.

  On the other hand, various manufacturing methods are conventionally known for porous films for battery separators. As one method, for example, a method of manufacturing a sheet made of a polyolefin resin and stretching the sheet at a high magnification is known (for example, see Patent Document 4). 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 thermal contraction of the battery separator in a high temperature environment, for example, melt and knead ultra high molecular weight polyethylene and a plasticizer, and extrude the plasticizer from a die, and then extract and remove the plasticizer. And the method of manufacturing the porous film | membrane used for a battery separator is also known (refer patent document 5). 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 JP-A-10-172606 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 production of a battery in which an electrode is bonded to a separator, and has sufficient adhesion between the electrode / separator and has a low internal resistance and a high level. To provide a reactive polymer-supported porous film for a separator that can be suitably used for manufacturing a battery having excellent rate characteristics, and a method for manufacturing a battery using such a reactive polymer-supported porous film With the goal.

  According to the present invention, the crosslinkable polymer having at least one first reactive group selected from a hydroxy group and a carboxyl group in the molecule and a second reactive group having a cationic polymerizable property is used. A reactive polymer for a battery separator, characterized in that a reactive polymer obtained by reacting with a reactive group and a reactive crosslinking agent and carrying a partially crosslinked reactive polymer together with a lithium salt is supported on a porous film. A supported porous film is provided.

  Further, according to the present invention, an electrode / reactive polymer-supported porous film laminate formed by laminating an electrode on the reactive polymer-supported porous film, and the electrode is adhered to the reactive polymer-supported porous film. An electrode / reactive polymer-supported porous film assembly is provided.

  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, and this electrode / reactive polymer-supported porous film laminate is obtained. After being charged into the battery container, an electrolyte containing a cationic polymerization catalyst is injected into the battery container, and at least a part of the reactive polymer is cationically polymerized to bond the porous film and the electrode. A method for producing the battery is provided.

  The reactive polymer-supported porous film for a battery separator according to the present invention has a second reaction having a cationic polymerization property with at least one first reactive group selected from a hydroxy group and a carboxyl group in the molecule. A crosslinkable polymer having a reactive group is reacted with a crosslinking agent having reactivity with the first reactive group, and a partially crosslinked reactive polymer is supported on a porous film together with a lithium salt. is there.

  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. The reactive polymer is injected into the battery container, and at least in the vicinity of the interface between the porous film and the electrode, at least a part of the reactive polymer is swollen in the electrolytic solution or eluted into the electrolytic solution, and the reactive polymer is obtained. The second reactive group possessed by cation is polymerized, the reactive polymer is further cross-linked, and at least a part of the electrolytic solution is gelled, whereby the porous film and the electrode are firmly bonded, and the electrode / porous A quality film joined body can be obtained.

  Moreover, according to the reactive polymer-supported porous film of the present invention, since the reactive polymer is partially crosslinked in advance, the electrode / reactive polymer-supported porous film laminate is immersed in the electrolytic solution. The elution and diffusion of the reactive polymer from the electrode / reactive polymer-supported porous film laminate into the electrolytic solution is suppressed, and the reactive polymer swells. As a result, a small amount of the reactive polymer should be used. Thus, the electrode can be adhered to the porous film (separator), and the porous film is excellent in 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.

  Furthermore, according to the present invention, the reactive polymer-supported porous film also supports a lithium salt as well as the above-mentioned reactive polymer. Therefore, when the battery is manufactured, the reactive polymer swells and adheres to the electrode and the separator. When functioning as an agent layer, the reactive polymer-supported porous film supports lithium salt in advance even if the electrolyte salt and electrolyte ions from the electrolyte solution are not sufficiently diffused into the adhesive layer. Therefore, the adhesive layer already has a sufficient lithium salt. Therefore, the internal resistance of the adhesive layer is low, and a battery having excellent characteristics can be obtained.

  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 with low internal resistance and excellent high rate characteristics is produced. It can be easily obtained with good quality.

  In the present invention, a porous film having a thickness in the range of 3 to 50 μm is preferably used. When the thickness of the porous film is less than 3 μm, the strength is insufficient, and the electrode may cause an internal short circuit when used as a separator in a battery. On the other hand, when the thickness of the porous film exceeds 50 μm, a battery using such a porous film as a separator has a too large distance between electrodes, and the internal resistance of the battery becomes excessive.

  The porous film has pores having an average pore diameter of 0.01 to 5 μm and a porosity in the range of 20 to 95%, preferably 30 to 90%, most preferably 35. A range of ˜85% is used. When the porosity 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 porous film must be used. This is not preferable because the internal resistance of the battery increases.

  Further, a porous film having an air permeability of 1500 seconds / 100 cc or less, preferably 1000 seconds / 100 cc or less is used. When the air permeability is too high, the 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. This is because when the piercing strength is less than 1 N, the porous film may be broken when a surface pressure is applied between the electrodes, thereby causing an internal short circuit.

  According to the present invention, the porous film is not particularly limited as long as it has the above-described characteristics, but if considering solvent resistance and oxidation-reduction resistance, polyolefin such as polyethylene and polypropylene is used. A porous film made of a resin is preferred. However, among them, when heated, the resin melts and the pores are blocked. As a result, the battery can have a so-called shutdown function. Resin films are particularly suitable. Here, the polyethylene resin includes not only a homopolymer of ethylene but also a copolymer of ethylene with an α-olefin such as propylene, butene and hexene. According to the present invention, a laminated film of a porous film such as polytetrafluoroethylene or polyimide and the polyolefin resin porous film is also suitably used as a porous film because of its excellent heat resistance.

  In the present invention, the crosslinkable polymer has at least one first reactive group selected from a hydroxy group and a carboxyl group in the molecule, and a second reactive group having cationic polymerizability, The polymer which gives the reactive polymer partially bridged by making it react with the crosslinking agent which consists of a polyfunctional compound having reactivity with one reactive group. In the present invention, the reactive polymer-supported porous film for a battery separator is obtained by reacting such a crosslinkable polymer with a crosslinking agent having reactivity with the first reactive group, and partially crosslinking the polymer. The resulting reactive polymer is supported on a porous film together with a lithium salt.

  According to the present invention, the second reactive group of the crosslinkable polymer, that is, the reactive group having cationic polymerizability, is preferably at least one reactive group selected from an oxetanyl group and an epoxy group. The oxetanyl group is preferably a 3-oxetanyl group.

  Thus, in the molecule, at least one first reactive group selected from a hydroxy group and a carboxyl group, and at least one second cationic reaction selected from the above oxetanyl group and an epoxy group. The crosslinkable polymer having a reactive group is preferably at least selected from a first radical polymerizable monomer having a first reactive group, a radical polymerizable monomer having an oxetanyl group, and a radical polymerizable monomer having an epoxy group. It is a radical copolymer of one type of second radical polymerizable monomer and a third radical polymerizable monomer other than these.

  Such a crosslinkable polymer is preferably at least one selected from a first radical polymerizable monomer having a first reactive group, a radical polymerizable monomer having an oxetanyl group, and a radical polymerizable monomer having an epoxy group. It can be obtained by radical copolymerization of a second radical polymerizable monomer of the seed and a third radical polymerizable monomer other than these.

  According to the present invention, when the crosslinkable polymer is thus obtained, the second radical polymerizable monomer is in the range of 5 to 50% by weight, preferably 10 to 30% by weight of the total monomer amount. Used as follows. Therefore, if a crosslinkable polymer containing an oxetanyl group is obtained as the second reactive group, the oxetanyl group-containing radical polymerizable monomer is 5 to 50% by weight of the total monomer amount, preferably 10 to 30%. Used in the range of% by weight. Similarly, in the case of obtaining a crosslinkable polymer containing an epoxy group as the second reactive group, the epoxy group-containing radical polymerizable monomer is 5 to 50% by weight of the total monomer amount, preferably 10 to 10%. It is used in the range of 30% by weight.

  Further, when an oxetanyl group-containing radical polymerizable monomer and an epoxy group-containing radical polymerizable monomer are used in combination to obtain a crosslinkable polymer having both an oxetanyl group and an epoxy group as the second reactive group, the oxetanyl group is also used. The total amount of the containing radical polymerizable monomer and the epoxy 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.

  When obtaining the crosslinkable polymer, if the amount of the second radical polymerizable monomer is less than 5% by weight in the total monomer amount, the amount of the reactive polymer required for gelation of the electrolytic solution is increased as described later. Therefore, the performance of the obtained battery is lowered. 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 / porous film (separator) in the obtained battery is lowered.

  On the other hand, the first radical polymerizable monomer having the first reactive group is used in the range of 0.1 to 10% by weight, preferably 0.5 to 5% by weight of the total monomer amount. When the first radical polymerizable monomer is less than 0.1% by weight of the total monomer amount, the crosslinking agent composed of a polyfunctional compound capable of reacting with the first reactive group of the crosslinkable polymer is reacted with the crosslinkable polymer. Even when the reactive polymer is partially crosslinked, the insoluble content of the reactive polymer is too small, and the electrode / porous film laminate is immersed in the electrolytic solution. Elution and diffusion into the electrolyte are not sufficiently suppressed, and the amount of reactive polymer elution and diffusion from the electrode / porous film laminate into the electrolyte increases, resulting in a gap between the porous film and the electrode. Therefore, it is impossible to obtain a battery having excellent characteristics.

  However, when the amount of the first radical polymerizable monomer is more than 10% by weight of the total monomer amount, when the resulting crosslinkable polymer is reacted with a crosslinking agent to partially crosslink the crosslinkable polymer, When the density of the reactive polymer produced is too high and the electrode / porous film laminate is immersed in the electrolytic solution, the reactive polymer does not swell sufficiently in the electrolytic solution. You can't get a good battery.

  In the present invention, as the first radical polymerizable monomer having the first reactive group, the first reactive group is a carboxyl group, for example, (meth) acrylic acid, itaconic acid, maleic acid, etc. Examples of the first reactive group that is a hydroxy group include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6- Hydroxyalkyl (meth) acrylates such as hydroxyhexyl (meth) acrylate, ethylene glycol mono (meth) acrylate, diethylene glycol mono (meth) acrylate, triethylene glycol mono (meth) acrylate, hexaethylene glycol mono (meth) acrylate, propylene (Poly) alkylene glycol mono (meth) acrylate such as recall mono (meth) acrylate, dipropylene glycol mono (meth) acrylate, tripropylene glycol mono (meth) acrylate, pentapropylene glycol mono (meth) acrylate, 2-hydroxyethyl (Meth) acrylate and γ-butyrolactone ring-opening adduct and the like can be mentioned. Here, (meth) acrylic acid means acrylic acid or methacrylic acid, and (meth) acrylate means acrylate or methacrylate.

  Further, as the second reactive group, the second radical polymerizable monomer having an oxetanyl group 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 oxetanyl group containing (meth) acrylate represented by these is used.

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

  In addition, as the second reactive group, the second radical polymerizable monomer having an epoxy group 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.

  The third radical polymerizable monomer other than those copolymerized together with the first radical polymerizable monomer and the second radical polymerizable monomer according to the present invention preferably has 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 or a fluorinated alkyl group having 1 to 6 carbon atoms, and n represents an integer of 0 to 3.)
(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,

(In each formula, R ₅ represents a hydrogen atom or a methyl group, and n is an integer of 0 to 3.)
Etc.

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

  In particular, according to the present invention, as described later, a layer of a crosslinkable polymer is formed on a peelable sheet, and this is transferred onto the porous film without causing deformation, deterioration or melting of the porous film. The crosslinkable polymer preferably has a glass transition temperature of 70 ° C. or lower, and preferably has a glass transition temperature in the range of 20 to 60 ° C.

  As described above, among other radical polymerizable monomers capable of setting the glass transition point of the crosslinkable polymer to preferably 70 ° C. or less, among those contained in the (meth) acrylate represented by the general formula (III), For example, ethyl acrylate, butyl acrylate, propyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, and the like can be given.

  As described above, the crosslinkable polymer includes the first radical polymerizable monomer having the first reactive group, the second radical polymerizable monomer having the second reactive group, and the third radical polymerization other than these. It can obtain by carrying out radical copolymerization with a functional 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.

  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.

  In the present invention, the lithium salt carried by the crosslinkable polymer-supported porous film is a salt containing lithium ions as a cation component and an inorganic acid or an organic acid as an anion component. Examples of the inorganic acid include hydrochloric acid, nitric acid, Examples thereof include phosphoric acid, sulfuric acid, borohydrofluoric acid, hydrofluoric acid, hexafluorophosphoric acid, perchloric acid, and examples of organic acids include organic carboxylic acids, organic sulfonic acids, and fluorine-substituted organic sulfones. An acid etc. can be mentioned.

  Accordingly, specific examples of such lithium salts include, for example, lithium acetate, lithium bromide, lithium chloride, lithium carbonate, lithium fluoride, lithium hydride, lithium hydroxide, lithium iodate, lithium lactate, lithium metaborate, Lithium metasilicate, lithium molybdate, lithium niobate, lithium nitrate, lithium oxalate, lithium phosphate, lithium stearate, lithium sulfate, lithium tetraborate, lithium tetrachloride cuprate, lithium tungstate, lithium perchlorate, Examples thereof include lithium bisfluoroethanesulfonylimide and lithium bis (trifluoromethylsulfonyl) imide. However, in the present invention, the lithium salt is not limited to these.

  In the present invention, the lithium salt is used in the range of 0.1 to 90% by weight, preferably 1 to 70% by weight, and most preferably 10 to 50% by weight, based on the total of the reactive polymer and the lithium salt. It is done.

  The reactive polymer-supported porous film for the battery separator according to the present invention is such that such a lithium salt is supported on the porous film together with the reactive polymer, and the reactive polymer is the crosslinkable polymer. Is reacted with a crosslinking agent by the first reactive group and partially crosslinked. As described above, the crosslinkable polymer reacts with the crosslinking agent by the first reactive group to crosslink, and is described in, for example, JP-A-11-43540 and JP-A-11-116663. In addition, the second reactive group causes cationic polymerization and crosslinking.

  In the present invention, a polyfunctional isocyanate is preferably used as the crosslinking agent. Examples of such a polyfunctional isocyanate include phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, diphenyl ether diisocyanate, hexamethylene diisocyanate, and cyclohexane diisocyanate. In addition to aromatic, araliphatic, alicyclic, and aliphatic diisocyanates, so-called isocyanate adducts obtained by adding these diisocyanates to polyols such as trimethylolpropane are also preferably used.

  In obtaining the reactive polymer-supported porous film according to the present invention, first, in order to support the crosslinkable polymer, the lithium salt, and the crosslinker on the porous film, for example, the crosslinkable polymer, the lithium salt, and the crosslinker are mixed with acetone, It was dissolved in an appropriate solvent such as ethyl acetate and butyl acetate, and a solution of a mixture of this crosslinkable polymer, lithium salt and crosslinker was applied and impregnated on the porous film by appropriate means such as casting or spray coating. Then, the solvent used may be removed by drying.

  As another method, a solution containing a crosslinkable polymer and a lithium salt is applied to a porous film and dried, and then a solution of a crosslinking agent is applied to such a porous film, impregnated, and dried. Also, a mixture of a crosslinkable polymer, a lithium salt, and a crosslinking agent can be supported on the porous film.

  In this way, after the crosslinkable polymer, the lithium salt, and the crosslinker are supported on the porous film, by heating to an appropriate temperature, the crosslinkable polymer is reacted with the crosslinker, and partially crosslinked, The reactive polymer and the lithium salt can be supported on the porous film.

  Furthermore, as another method, after preparing a solution containing a crosslinkable polymer, a lithium salt, and a crosslinker, the crosslinkable polymer is reacted with a crosslinker in advance and partially crosslinked to obtain a reactive polymer. The solution containing the reactive polymer may be applied to an appropriate peelable sheet, dried, and then transferred to a porous film.

  However, one particularly preferable method for supporting the crosslinkable polymer, the lithium salt, and the crosslinker on the porous film is to apply a solution containing the crosslinkable polymer, the lithium salt, and the crosslinker to the peelable sheet and then dry it. After forming a layer made of a mixture of a crosslinkable polymer, a lithium salt and a crosslinker on the peelable sheet, the peelable sheet is stacked on the porous film and heated and pressed to crosslink the crosslinkable polymer with the lithium salt. The layer made of the mixture with the agent is transferred to the porous film.

  In particular, according to the present invention, when producing a crosslinkable polymer, together with a first radical polymerizable monomer having a first reactive group and a second radical polymerizable monomer having a second reactive group, As described above, by selecting and using a third radically polymerizable monomer other than these and copolymerizing them, the glass transition temperature of the resulting crosslinkable polymer is preferably lowered to 70 ° C. or lower. Therefore, by using such a crosslinkable polymer, as described above, a layer composed of a mixture of the crosslinkable polymer, the lithium salt and the crosslinker is formed on the peelable sheet, and this layer is formed of the crosslinkable polymer. Preferably, the porous film is heated while being heated to a temperature of 100 ° C. or lower so as not to cause deformation or melting of the porous film. By words, it is possible to transfer a layer of porous without adversely affecting the film, a mixture composed of a porous film crosslinkable polymer and a lithium salt and a crosslinking agent.

  As the above-mentioned peelable sheet, a polypropylene resin sheet is typically preferably used, but is not limited thereto. For example, a sheet of polyethylene terephthalate, polyethylene, vinyl chloride, engineer plastic, paper (particularly, resin-impregnated paper) ), Synthetic paper, and laminates thereof. These sheets may be back-treated with a compound such as silicone or long-chain alkyl as necessary.

  Thus, the layer of the mixture of the crosslinkable polymer, the lithium salt, and the crosslinking agent is transferred to the porous film, and a layer made of the mixture of the crosslinkable polymer, the lithium salt, and the crosslinking agent is formed on the porous film. When, for example, a solution of a mixture of a crosslinkable polymer, a lithium salt, and a crosslinker is applied to the surface of the porous film, the crosslinkable polymer and the lithium salt are placed in the pores inside the porous film. A layer of the mixture of the crosslinkable polymer, the lithium salt and the crosslinker is reliably formed on the surface of the porous film without intruding the mixture with the crosslinker and thus without clogging the pores of the porous film. be able to.

  Thus, after making the porous film carry the mixture of the crosslinkable polymer, the lithium salt and the crosslinker, this is heated to an appropriate temperature to cause the crosslinkable polymer to react with the crosslinker. A reactive polymer-supported porous film can be obtained by crosslinking.

In the present invention, the amount of the crosslinkable polymer, lithium salt, and crosslinker supported in the porous film depends on the type of crosslinkable polymer used, the lithium salt, and the crosslinker, the mode of the support, etc. in the range of 5 g / m ^2, preferably in the range of 0.8~3g / m ^2. When the amount of the crosslinkable polymer, lithium salt, and crosslinker supported on the porous film is too small, sufficient adhesive force cannot be obtained between the separator and the electrode in the obtained battery. On the other hand, when the amount is too large, the characteristics of the obtained battery are deteriorated, which is not preferable.

  According to the present invention, the reactive polymer obtained by partially crosslinking the crosslinkable polymer in this way usually has an insoluble fraction in the range of 1 to 90%, preferably 3 to 75%. And most preferably has an insoluble fraction in the range of 10 to 65%. Here, the insoluble fraction is, as will be described later, 2 with stirring a porous film carrying a partially crosslinked reactive polymer in an ethylene carbonate / diethyl carbonate (volume ratio 1/1) mixed solvent at room temperature. It refers to the ratio of the reactive polymer remaining on the porous film when immersed in ethyl methyl carbonate after being immersed for a period of time.

  Thus, it is limited to reacting a crosslinkable polymer with a crosslinking agent, for example, a polyfunctional isocyanate and partially crosslinking to obtain a reactive polymer having an insoluble fraction in the range of 1 to 90%. Although not usually, the isocyanate group possessed by the polyfunctional isocyanate is 0.01 per mole of the first reactive group possessed by the crosslinkable polymer, that is, 1 mole part of the reactive group such as hydroxy group or carboxyl group. -5.0 mol part, preferably 0.05-3.0 mol part, and the heating reaction conditions between the crosslinkable polymer and the polyfunctional isocyanate may be adjusted. It is possible to obtain a reactive polymer having an insoluble fraction of When the first reactive group of the crosslinkable polymer is an amino group, the isocyanate group of the polyfunctional isocyanate is 0.01 to 5.0 mol parts, preferably 1 mol part of the active hydrogen, What is necessary is just to adjust the heating reaction conditions of a crosslinkable polymer and polyfunctional isocyanate while using it so that it may become 0.05-3.0 mol part.

  As an example, for example, in the case of a crosslinkable polymer having a hydroxy group as the first reactive group, the isocyanate group of the polyfunctional isocyanate is 0.5 to 2.0 with respect to 1 mol of the first reactive group. A reactive polymer having an insoluble fraction of 1 to 90% can be obtained by using it so as to be a molar part and by subjecting the crosslinkable polymer and the polyfunctional isocyanate to a heat reaction at 50 ° C. for 12 to 60 hours.

  In the present invention, it is preferred that the reactive polymer is supported on the entire surface of the porous film together with the lithium salt. However, in some cases, the reactive polymer is partially on the porous film, that is, for example, streaks, spots, lattices. You may make it carry | support partially in eyes, stripes, a turtle shell pattern, etc.

  According to the present invention, the reactive polymer-supported porous film is laminated with the positive electrode and the negative electrode sandwiched therebetween, and preferably, the positive electrode and the negative electrode are bonded to the crosslinkable polymer-supporting porous film under pressure and pressure. An electrode / reactive polymer-supported porous film laminate can be obtained by temporarily adhering to a film and bonding. Hereinafter, in the present invention, this electrode / reactive polymer-supported porous film laminate may be simply referred to as an electrode / porous film laminate for simplicity.

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

  In the present invention, the electrode / porous film laminate may have an electrode laminated on a reactive polymer-supported porous film. Therefore, for example, a negative electrode / porous film / positive electrode, a negative electrode / porous film / positive electrode / porous film, etc. are used as the electrode / porous film laminate according to the structure and form of the battery. The electrode / porous film laminate may be in the form of a sheet or may be wound.

  The reactive polymer-supported porous film according to the present invention can be suitably used for battery production. That is, an electrode is laminated or wound on a reactive polymer-supported porous film to obtain an electrode / reactive polymer-supported porous film laminate, and then this laminate is a battery container comprising a metal can, a laminate film, or the like. If 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. At least a part of the reactive polymer supported on the porous polymer-supported porous film is swollen in the electrolyte solution in the vicinity of the interface between the porous film and the electrode, or eluted and diffused in the electrolyte solution. The second reactive group is cross-linked by cationic polymerization, and at least a part of the electrolytic solution is gelled to adhere the electrode to the porous film, and thus the porous film is separated. And data electrode to the separator can be obtained strongly adhered cells. In this case, the reactive polymer causes the electrolyte solution to gel at least in the vicinity of the interface between the porous film and the electrode by crosslinking of the reactive group by cationic polymerization, thereby bonding the electrode and the porous film. To function.

  In particular, according to the present invention, in the production of a battery using a reactive polymer-supported porous film, the reactive polymer is partially crosslinked in advance and has an insoluble fraction in the above-described range. Even when immersed in the electrolyte, elution and diffusion into the electrolyte are suppressed. Therefore, if an electrode / porous film laminate containing such a reactive polymer is charged into a battery container and then an electrolyte containing an electrolyte containing a cationic polymerization catalyst is injected into the battery container, the porous film and electrode In the vicinity of the interface with the electrode / porous film laminate, only a part of the reactive polymer in the electrolyte swells or elutes in the electrolyte, and the second reactive group The reactive polymer is cationically polymerized by an electrolyte that also serves as a cationic polymerization catalyst in the electrolytic solution, preferably an electrolyte that also serves as a cationic polymerization catalyst. Further, the polymer is cross-linked, and the electrolytic solution is gelled to firmly adhere the electrode to the porous film with good adhesion. Thus, an electrode / reactive polymer-supported porous film (that is, a separator in the resulting battery) assembly can be obtained. Hereinafter, for the sake of simplicity, the electrode / reactive polymer-supported porous film assembly may be simply referred to as an electrode / reactive polymer assembly.

  That is, according to the present invention, the reactive polymer has an insoluble fraction within the above range. Therefore, even when immersed in the electrolytic solution, elution and diffusion into the electrolytic solution are prevented or reduced. Since it is effectively used for adhesion between the electrode and the porous film, the use of a relatively small amount of the reactive polymer makes it possible to bond the electrode and the porous film stably and more firmly.

  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 24 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.

  According to the present invention, in the battery obtained, the adhesive force obtained between the electrode and the separator (porous film) is usually 0.03 N / cm, although it depends on the heat shrinkage characteristics of the porous film used. It is above, Preferably, it is 0.05 N / cm or more. When this adhesive force is too low, the separator may be thermally contracted, or the separator may be inferior in the function of keeping the distance between the electrodes constant. Further, the above-mentioned adhesive force is not particularly limited at the upper limit for the purpose of the present invention, but in order to increase the adhesive force, it is necessary to increase the amount of the adhesive used, and this As described above, when the amount of the adhesive to be used is increased, the characteristics of the obtained battery may be deteriorated. Therefore, in view of the thermal characteristics of the porous film used for the battery separator and the function of the separator to keep the distance between the electrodes constant, the adhesive force is preferably 1.0 N / cm or less.

  The porous film in the electrode / porous film assembly thus obtained functions as a separator after being incorporated into a battery. Here, in such an electrode / porous film assembly according to the present invention, since the electrode and the porous film are firmly bonded as described above, the separator (porous film) is, for example, 150. Even when placed in a high temperature environment such as ° C., the area heat shrinkage rate is small, usually 20% or less, and preferably 15% or less.

  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 and the like are preferably used.

  Furthermore, as the solvent for the electrolyte salt used in the present invention, any solvent can be used as long as it dissolves the electrolyte salt. Examples of the non-aqueous solvent include ethylene carbonate, propylene carbonate, Use 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 alone or as a mixture of two or more. be able to.

  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 gel electrolyte obtained.

  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. 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. In the following, the physical properties and battery characteristics of the substrate porous film 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− (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.

(Insoluble fraction of reactive polymer)
The reactive polymer-supported porous film supporting a known amount A of the reactive polymer was weighed and its weight B was measured. Next, this reactive polymer-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 carrying | support 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

(Glass transition temperature of crosslinkable polymer)
The glass transition temperature of the crosslinkable polymer was measured as follows. 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, and manufactured by Seiko Electronics Industry Co., Ltd. Using DMS120, the glass transition temperature was determined at 10 kHz in bending mode. The glass transition temperature was determined from the peak temperature of tan δ at a temperature increase rate of 5 ° C./min and a temperature range of 20 to 200 ° C.

(Measurement of area heat shrinkage of separator (porous film) / electrode assembly)
The positive electrode / reactive polymer-supported porous film / negative electrode laminate obtained in the preparation of the reference battery, the example or the comparative example was punched into a predetermined size. This was impregnated with an electrolytic solution composed of a mixed solvent of ethylene carbonate / diethyl carbonate (weight ratio 1/1) in which lithium hexafluorophosphate was dissolved at a concentration of 1.0 mol / L to prepare a sample.

As shown in FIG. 1, a container in which an O-ring 3 is fitted to an annular upper end surface 2 of a peripheral wall of a SUS circular container 1 is prepared, the sample 4 is placed on the bottom of the container, and 9 g / The weight 5 was placed so as to give a surface pressure of m ² , and then the lid 6 was put on the container to seal the inside of the container. Thus, after putting the container containing the sample into a dryer at 150 ° C. for 1 hour, it is allowed to cool, the sample is taken out from the container, the sample separator (porous film) is peeled off from the positive and negative electrodes, and read by the scanner. Thus, the area heat shrinkage rate was determined in comparison with the area of the porous film used first.

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 a vinylidene fluoride resin (KF Polymer L # 1120 manufactured by Kureha Chemical Industry Co., Ltd.) was mixed, and this was mixed with a slurry using N-methyl-2-pyrrolidone so that the solid concentration was 15% by weight. did. The slurry was applied to an aluminum foil (current collector) having a thickness of 20 μm to a thickness of 200 μm, vacuum-dried at 80 ° C. for 1 hour, and 120 ° C. for 2 hours, and then pressed by a roll press to obtain a thickness of the active material layer. A positive electrode sheet having a thickness of 100 μm 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 Is mixed with 10 parts by weight of vinylidene fluoride resin (KF Polymer L # 1120 manufactured by Kureha Chemical Industry Co., Ltd.), and N-methyl-2-pyrrolidone is used so that the solid content concentration becomes 15% by weight. A slurry was obtained. This slurry was applied onto a copper foil (current collector) having a thickness of 20 μm, applied to a thickness of 200 μm, dried at 80 ° C. for 1 hour, dried at 120 ° C. for 2 hours, and then pressed with a roll press, A negative electrode sheet having an active material layer thickness of 100 μm was prepared.

(Production of reference battery)
A porous film (separator) made of polyethylene resin having a thickness of 16 μm, a porosity of 40%, an air permeability of 300 seconds / 100 cc, and a puncture strength of 3.0 N was prepared. The negative electrode sheet obtained in Reference Example 1, the porous film, and the positive electrode sheet obtained in Reference Example 1 were laminated in this order to obtain a positive electrode / porous film / negative electrode laminate. After charging this into an aluminum laminate package, an electrolytic solution made of an ethylene carbonate / diethyl carbonate (weight ratio 1/1) mixed solvent in which lithium hexafluorophosphate was dissolved at a concentration of 1.0 mol / L was injected into the package. Then, the package was sealed and a lithium ion secondary battery was assembled. The battery was charged and discharged three times at a rate of 0.1 CmA, then charged at 0.1 CmA, and then discharged at 5 CmA to obtain a 5 CmA discharge capacity A. Further, the area heat shrinkage rate of the separator in the positive electrode / porous film / negative electrode laminate was 72%.

(Discharge characteristics of batteries according to examples or comparative examples)
About the laminate seal type lithium ion secondary battery obtained in the following examples or comparative examples, after charging and discharging three times at a rate of 0.1 CmA, charging at 0.1 CmA, and thereafter at 5 CmA The battery was discharged to obtain a 5 CmA discharge capacity B, and the battery characteristics were evaluated by the percentage (%) of the discharge capacity B to the discharge capacity A of the reference battery.

(Measurement of adhesion between electrode sheet and separator)
The obtained battery is disassembled before charging / discharging, the positive electrode / separator / negative electrode assembly is taken out, the negative electrode / separator interface is peeled over 5 mm from the end of this assembly, and this is sandwiched between chucks of a tensile tester. Thereafter, the chuck was moved in the 180 ° direction at a speed of 1 mm / min to measure the adhesive force, and this was divided by the sample width (cm) to obtain the negative electrode / separator adhesive force (N / cm). Next, the interface between the positive electrode and the separator was peeled over 5 mm from the end of the joined body, and the positive electrode / separator adhesive force (N / cm) was determined in the same manner as in the case of the negative electrode.

Production Example 1
(Production of a crosslinkable polymer containing a hydroxy group and an oxetanyl group (hydroxyethyl methacrylate monomer component 2% by weight and oxetanyl group-containing monomer component 25% by weight, weight average molecular weight 314000))
A 500 mL three-necked flask equipped with a reflux condenser was charged with 58.4 g of methyl methacrylate, 20.0 g of 3-ethyl-3-oxetanylmethyl methacrylate and 1.6 g of 2-hydroxyethyl methacrylate, 158.0 g of ethyl acetate and N, N'-Azobisisobutyronitrile (0.20 g) was charged and mixed with stirring for 30 minutes while introducing nitrogen gas, and then heated to 70 ° C. to initiate radical polymerization. When about 1 hour had passed, the viscosity of the reaction mixture began to rise and polymerization was continued for another 8 hours. Thereafter, the resulting reaction mixture was cooled to 40 ° C., 0.20 g of N, N′-azobisisobutyronitrile was added again, and then reheated to 70 ° C. to further carry out radical polymerization for 8 hours. went.

  After completion of the reaction, the obtained reaction mixture was cooled to 40 ° C., 295 g of ethyl acetate was added, and the mixture was stirred and mixed until the whole became homogeneous, and an ethyl acetate solution (concentration 15% by weight) of the oxetanyl group-containing crosslinkable polymer was obtained. Obtained.

  Next, 100 g of this polymer solution was poured into 600 mL of methanol while stirring with a high-speed mixer to precipitate the polymer. The polymer was separated by filtration, and after washing with methanol several times, dried nitrogen gas (dew point temperature of −150 ° C. or lower) in which liquid nitrogen was vaporized was circulated in a drying tube and dried. It was vacuum-dried in a desiccator for 6 hours to obtain a white powdery oxetanyl group-containing crosslinkable polymer. 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. The glass transition temperature was 115 ° C.

Example 1
10 g of the crosslinkable polymer obtained in Production Example 1 was dissolved in ethyl acetate at room temperature to prepare a 10 wt% crosslinkable polymer solution, and 2.5 g of lithium bis (trifluoromethylsulfonyl) imide (LiTFSI) and Polyfunctional isocyanate (hexamethylene diisocyanate / trimethylolpropane adduct, ethyl acetate solution, solid content 25%, Coronate HL manufactured by Nippon Polyurethane Industry Co., Ltd.) 1.32 g was added and dissolved to obtain a crosslinkable polymer and a lithium salt. A coating solution containing a polyfunctional isocyanate was prepared.

This coating solution was applied to one side of a polyethylene resin porous film (thickness 16 μm, porosity 40%, air permeability 300 seconds / 100 cc, puncture strength 3.0 N) using a # 8 wire bar, and then 50 ° C. To evaporate ethyl acetate to carry a crosslinkable polymer, a lithium salt and a polyfunctional isocyanate. Next, the crosslinkable polymer, lithium salt and polyfunctional isocyanate were similarly supported on the other side of the polyethylene resin porous film thus treated, and thus a crosslinkable polymer-supported porous film was obtained. In this crosslinkable polymer-supported porous film, the supported amount of the crosslinkable polymer, lithium salt and polyfunctional isocyanate per one side of the film was 1.3 g / m ² .

  Next, the crosslinkable polymer-supported porous film is put into a thermostat at 50 ° C. for 48 hours, the crosslinkable polymer supported on the porous film is reacted with polyfunctional isocyanate, and a part of the crosslinkable polymer is obtained. Crosslinking was thus obtained to obtain a reactive polymer-supported porous film. In this reactive polymer-supported porous film, the insoluble content of the reactive polymer was 35%.

  The negative electrode sheet obtained in Reference Example 1, the reactive polymer-supported porous film and the positive electrode sheet obtained in Reference Example 1 were laminated in this order to form an electrode / reactive polymer-supported porous film laminate. Was injected into an aluminum laminate package, and an electrolyte solution consisting of ethylene carbonate / diethyl carbonate (weight ratio 1/1) mixed solvent in which lithium hexafluorophosphate was dissolved at a concentration of 1.0 mol / L was injected. Sealed. After that, by heating at 70 ° C. for 7 hours, the crosslinkable polymer is cationically polymerized, crosslinked, the electrode sheet is brought into contact with the porous film (separator), and the electrolyte is partially gelled, A laminate seal type battery was obtained.

  The 5 CmA discharge capacity of this battery was 94% of the discharge capacity of the reference battery. When this battery was disassembled and the adhesive force between the electrode sheet and the separator was measured, it was 0.28 N / cm for the positive electrode and 0.14 N / cm for the negative electrode. Moreover, the area heat shrinkage rate of the separator in the separator / electrode assembly obtained using the reactive polymer-supported porous film was 1.9%.

Comparative Example 1
A poly (vinylidene fluoride / hexafluoropropylene) copolymer (Kynar 2801 manufactured by Elf Atchem) was dissolved in N-methyl-2-pyrrolidone to prepare a polymer solution having a concentration of 10% by weight. After this polymer solution was applied to both sides of a polyethylene resin porous film (film thickness 16 μm, porosity 40%, air permeability 300 sec / 100 cc, puncture strength 3.0 N) with a wire bar (# 20), 60 By heating to 0 ° C., N-methyl-2-pyrrolidone was volatilized, and thus a polyethylene resin porous film having a poly (vinylidene fluoride / hexafluoropropylene) copolymer supported on both sides was obtained.

The negative electrode sheet obtained in Reference Example 1, the porous film carrying the poly (vinylidene fluoride / hexafluoropropylene) copolymer and the positive electrode sheet obtained in Reference Example 1 were laminated in this order, and the temperature was 80 The separator / electrode laminate was obtained by press-bonding at 1 ° C. and a pressure of 5 kgf / cm ² for 1 minute. An electrolytic solution comprising an ethylene carbonate / diethyl carbonate (weight ratio 1/1) mixed solvent in which the separator / electrode laminate is charged in an aluminum laminate package and lithium hexafluorophosphate is dissolved at a concentration of 1.0 mol / L. After the injection, the package was sealed to obtain a laminate seal type battery.

  The 5 CmA discharge capacity of this battery was 50% of the discharge capacity of the reference battery. When the battery was disassembled and the adhesive strength between the electrode and the separator was measured, it was 0.20 N / cm for the positive electrode and 0.09 N / cm for the negative electrode. Further, the area heat shrinkage rate of the separator in the separator / electrode laminate was 30%.

Comparative Example 2
A laminated seal type battery was obtained in the same manner as in Comparative Example 1 except that the concentration of the poly (vinylidene fluoride / hexafluoropropylene) copolymer solution was changed to 5% by weight. The 5 CmA discharge capacity of this battery was 90% of the discharge capacity of the reference battery. When this battery was disassembled and the adhesive force between the electrode sheet and the separator was measured, it was 0.05 N / cm for the positive electrode and 0.0 N / cm for the negative electrode. Further, the area heat shrinkage rate of the separator in the separator / electrode laminate was 60%.

In an Example, it is a figure which shows the apparatus for measuring the area heat shrinkage rate of a separator (porous film) / electrode assembly.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Cylindrical container 4 ... Sample (Separator (porous film) / electrode assembly)
5 ... Weight 6 ... Lid

Claims (9)

  A crosslinkable polymer having at least one first reactive group selected from a hydroxy group and a carboxyl group in the molecule and a second reactive group having cationic polymerization properties is reacted with the first reactive group. A reactive polymer-supported porous film for battery separators, wherein a reactive polymer obtained by reacting with a crosslinking agent having a property and partially crosslinked is supported on a porous film together with a lithium salt.   The reactive polymer-supported porous material for a battery separator according to claim 1, wherein the cross-linking agent polymer is a polymer having at least one reactive group selected from an oxetanyl group and an epoxy group as the second reactive group. the film.   The reactive polymer-supported porous film for battery separator according to claim 1, wherein the crosslinking agent is a polyfunctional isocyanate.   The reactive polymer-supported porous film according to claim 1, wherein the reactive polymer has an insoluble content of 1 to 90%.   An electrode / reactive polymer-carrying porous film laminate obtained by laminating an electrode on the reactive polymer-carrying porous film according to any one of claims 1 to 4.   An electrode / reactive polymer-supported porous film assembly comprising an electrode attached to the reactive polymer-supporting porous film according to any one of claims 1 to 4.   An electrode is laminated on the reactive polymer-supported porous film according to claim 1 to obtain an electrode / reactive polymer-supported porous film laminate, and the electrode / reactive polymer-supported porous film laminate. After the body is charged in the battery container, an electrolyte containing a cationic polymerization catalyst is injected into the battery container, and at least a part of the reactive polymer is cationically polymerized to bond the porous film and the electrode. A battery manufacturing method characterized by the above.   The method for producing a battery according to claim 7, wherein the cationic polymerization catalyst is an onium salt. The method for producing a battery according to claim 8, wherein the electrolytic solution contains at least one selected from lithium hexafluorophosphate and lithium tetrafluoroborate as an electrolyte salt that also serves as a cationic polymerization catalyst.

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