JP2007035556A - Separator for battery and manufacturing method of battery using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separator which can be manufactured efficiently by bonding an electrode sheet with a separator temporarily to make a lamination of the electrode sheet/separator and to prevent the electrode sheet and the separator from moving separately, and which has not only an excellent ion permeability and electric insulation but also a high efficiency as well as high safety with a function as a junction of the electrode/separator having a strong adhesiveness between electrode sheets, and to provide a manufacturing method of the above separator and a battery using the above separator. <P>SOLUTION: A pair of films 1 composed of a microcapsule having an epoxy group and an epoxy resin hardening agent and a reactive polymer with a cross-linking structure face each other in separation and a single layer of insulating fine particles is bonded and held between the pair of films. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a battery separator that is useful for manufacturing a battery and can contribute to safety during use in a battery manufactured using the battery, and a method for manufacturing the battery separator. Furthermore, the present invention relates to a battery manufacturing method using such a battery separator.

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

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

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

  Therefore, in order to improve the safety of the battery, reduction of the thermal contraction rate of the battery separator under such a high temperature environment is an important issue. In this regard, for example, in order to suppress 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 4). However, according to this method, contrary to the above method, the obtained porous film has not been stretched, and therefore there is a problem that the strength is not sufficient. In addition, there is a problem that the plasticizer used as an auxiliary material remains as a waste and a problem of regeneration of the extraction solvent.

As described above, the battery separator is made of a breathable resin porous film because of its required characteristics, and is conventionally manufactured through many complicated processes such as stretching and extraction using various auxiliary materials. The manufacturing cost was high.
JP 09-161814 A JP 11-329439 A Japanese Patent Application Laid-Open No. 09-012756 Japanese Patent Laid-Open No. 05-310989

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

  According to the present invention, a pair of films comprising a reactive polymer having an epoxy group and further containing a microcapsule encapsulating an epoxy resin curing agent and having a crosslinked structure are opposed to each other. There is provided a battery separator characterized in that insulating fine particles form a single layer therebetween and are sandwiched and supported by the pair of films.

  According to the present invention, a microcapsule containing a polyfunctional isocyanate and an epoxy resin curing agent is mixed with a solution of a crosslinkable polymer having a hydroxy group and an epoxy group, and the resulting solution of the crosslinkable polymer is peelable. A film made of a first crosslinkable polymer containing microcapsules encapsulating the polyfunctional isocyanate and an epoxy resin curing agent is formed on the peelable film by coating on the film and drying. Insulating fine particles are dispersed in a single layer on the film made of the first crosslinkable polymer on the peelable film obtained in this manner, and are adhered and supported on the film made of the first crosslinkable polymer. , A microphone containing a polyfunctional isocyanate and an epoxy resin curing agent in a solution of a crosslinkable polymer having a hydroxy group and an epoxy group The capsule is mixed, and the resulting solution of the crosslinkable polymer is applied onto a peelable film, dried, and composed of a second crosslinkable polymer containing microcapsules containing the polyfunctional isocyanate and the epoxy resin curing agent. A film is prepared, and the film made of the second crosslinkable polymer is laminated and bonded onto the insulating fine particles on the film made of the first crosslinkable polymer, and then heated to heat the first and The second crosslinkable polymer is cross-linked by reaction with the polyfunctional isocyanate to make each of them a reactive polymer, thus containing an epoxy group and further containing a microcapsule encapsulating an epoxy resin curing agent. , A pair of films made of a reactive polymer having a cross-linked structure are facing away from each other, and the insulating fine particles are in between Method for producing a battery separator are bonded carried sandwiched the pair of film are provided without.

  Furthermore, according to the present invention, an electrode sheet is laminated on the battery separator described above and pressed to form an electrode sheet / separator laminate. After the laminate is charged into the battery container, A method for producing a battery comprising injecting an electrolyte, heating, activating an epoxy resin curing agent, crosslinking and curing a reactive polymer with its epoxy group, and bonding an electrode sheet to a separator. Provided.

  The battery separator of the present invention has an epoxy group and further contains a microcapsule encapsulating an epoxy resin curing agent, and a pair of films made of a reactive polymer having a crosslinked structure are separated from each other. Insulating fine particles are sandwiched between the pair of films and bonded and supported by forming a single layer between them, so that the positive electrode and the negative electrode can be physically separated from each other. Has insulation. In addition, since the insulating fine particles are preferably sandwiched and supported in a single layer between the pair of films facing each other, preferably with a gap between the particles, the battery reaction The ions that contribute to the water easily pass through the gaps between the insulating fine particles inside the separator, and therefore the battery separator of the present invention also has excellent ion permeability.

  Furthermore, according to the battery separator of the present invention, the electrode sheet is easily temporarily bonded to the separator by pressure-bonding the electrode sheet to a film made of a reactive polymer under heating, if necessary. A laminated body can be obtained, and when the battery is assembled, the electrolyte quickly penetrates into the separator, and a battery having excellent performance can be obtained.

  In addition, since the reactive polymer in the battery separator of the present invention is cross-linked in advance, the elution of the reactive polymer into the electrolytic solution is prevented even when the electrode sheet / separator laminate is immersed in the electrolytic solution. Therefore, it is effectively used for adhesion of the electrode sheet. In addition, since the reactive polymer has a high degree of swelling, it reacts with an activated epoxy resin curing agent while it swells in the electrolyte solution at the interface between the separator and the electrode sheet temporarily bonded to the separator. The crosslinkable polymer further cross-links the electrode sheet more firmly to the separator to give an electrode sheet / separator assembly, and thus the resulting battery is a reaction that forms a separator even when placed in a high temperature environment. Since the insulating polymer maintains the insulating property without contracting, it is excellent in safety.

  In the present invention, the crosslinkable polymer means a polymer that has an epoxy group together with a hydroxy group and can be cross-linked by reacting with a polyfunctional cross-linking agent having reactivity with the hydroxy group, for example, a polyfunctional isocyanate. . The reactive polymer refers to a polymer having an epoxy group and further containing a microcapsule encapsulating an epoxy resin curing agent and having a cross-linked structure. It can be obtained by reacting the polymer with the polyfunctional isocyanate through its hydroxy group to crosslink the crosslinkable polymer.

  According to the battery separator of the present invention, a film made of a crosslinkable polymer containing microcapsules encapsulating an epoxy resin curing agent is cross-linked in this way to form a film made of a reactive polymer. A pair of films consisting of a pair of films are spaced apart from each other, and insulating fine particles are preferably sandwiched between the pair of films, preferably in a single layer with a gap between them, Therefore, the pair of films are bonded to each other through the insulating fine particles.

  Moreover, in this invention, an electrode sheet / separator laminated body means the thing which pressure-bonded the electrode sheet to the above separators, temporarily bonded, and bonded together. An electrode sheet / separator assembly is an electrode sheet formed by activating an epoxy resin curing agent encapsulated in microcapsules to crosslink an epoxy group of a reactive polymer in the electrode sheet / separator laminate. The one that is adhered to the separator.

  That is, according to the present invention, as described above, a reactive polymer can be obtained by reacting a crosslinkable polymer with a polyfunctional isocyanate. Therefore, since the reactive polymer already has a crosslinked structure and has an epoxy group, the reactive polymer swells in the electrolytic solution, while the microcapsule encapsulating the epoxy resin curing agent is destroyed in the electrolytic solution. The functional polymer is cross-linked by the activated epoxy resin curing agent, and the electrode sheet is bonded to the film made of the reactive polymer of the separator by such a cross-linking reaction to form an electrode sheet / separator assembly.

  In the present invention, the crosslinkable polymer is a radical copolymerization of a radically polymerizable monomer having a hydroxy group, a radically polymerizable monomer having an epoxy group, and another radically polymerizable monomer having no such functional group according to a conventional method. Can be obtained.

  In order to radically copolymerize such a radically polymerizable monomer having a hydroxyl group, a radically polymerizable monomer having an epoxy group, and another radically polymerizable monomer having no functional group, for example, these monomers are mixed with ethyl acetate. And solution polymerization using a radical polymerization initiator such as benzoyl peroxide and azobisisobutyronitrile as a polymerization initiator. The monomer may be emulsion polymerized in water. According to the present invention, the crosslinkable polymer thus obtained preferably has a weight average molecular weight in the range of 200,000 to 3,000,000.

  Examples of the radical polymerizable monomer having a hydroxy group include 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate. Examples of the radical polymerizable monomer having an epoxy group include glycidyl (meth) acrylate and 3,4-epoxycyclohexylmethyl (meth) acrylate.

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

  Examples of the (meth) acrylic acid ester include ethyl (meth) acrylate, butyl (meth) acrylate, propyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, and the like. As described above, a linear or branched alkyl ester having 1 to 18 carbon atoms in the alkyl group is preferably used.

  In addition to the above, for example, esters having a cyclic group such as isobornyl ester, dicyclopentenyl ester, tetrahydrofurfuryl ester, benzyl ester, cyclohexyl ester, etc. of (meth) acrylic acid, and (meth) acrylic having a maleimide group (Meth) acrylic acid esters and (meth) acrylamides whose homopolymers have a glass transition temperature of about 40 ° C. or higher, such as acid esters and imide (meth) acrylates having highly polar groups such as imide groups, are obtained. It is preferably used when it is necessary to increase the glass transition temperature of the resulting crosslinkable polymer.

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

  In particular, in the present invention, as a preferred example of the crosslinkable polymer, an acrylic monomer component such as (meth) acrylic acid ester, (meth) acrylonitrile, (meth) acrylamide, together with the acrylic monomer component having the functional group described above. And a crosslinkable polymer. For example, a crosslinkable polymer having a (meth) acrylonitrile component in an amount of up to 80% by weight, preferably in the range of 5 to 30% by weight is excellent in heat resistance and solvent resistance. It is an example.

  In the present invention, (meth) acryl means acryl or methacryl, (meth) acrylate means acrylate or methacrylate, (meth) acryloyl means acryloyl or methacryloyl, (meth) acrylonitrile means acrylonitrile or methacrylonitrile Means.

  In the present invention, in the production of the crosslinkable polymer, it is preferable that the radical polymerizable monomer having the epoxy group occupies a ratio of 0.1 to 30% by weight in the total monomers. When the ratio of the radically polymerizable monomer having an epoxy group is less than 0.1% by weight in all monomers, a microcapsule in which an epoxy resin curing agent is encapsulated in the resulting crosslinkable polymer is dispersed to form a battery separator. Even if an electrode sheet is laminated to form an electrode sheet / separator laminate and an epoxy resin curing agent is allowed to act on the reactive polymer in the laminate in the electrolyte, the reactive polymer is sufficient. Therefore, the electrode sheet cannot be strongly bonded to the separator. On the other hand, when the ratio of the radically polymerizable monomer having an epoxy group is more than 30% by weight in all monomers, a gel is easily generated during the production of the crosslinkable polymer, and the reactive polymer in the electrode sheet / separator is Although it seems that crosslinking is excessive when the epoxy curing agent is crosslinked and cured in the electrolytic solution, the characteristics of the obtained battery are deteriorated.

  Moreover, it is preferable that the radically polymerizable monomer which has a hydroxyl group is the range of 0.1 to 10 weight% in all the monomers. When the ratio of the radically polymerizable monomer having a hydroxy group is less than 0.1% by weight in the total amount of monomers, the degree of cross-linking in the resulting reactive polymer is increased even if polyfunctional isocyanate is reacted with the resulting cross-linkable polymer. When the obtained separator electrode sheet is laminated and brought into contact with the electrolytic solution, the reactive polymer is likely to elute into the electrolytic solution, and the electrode sheet / separator may be separated. On the other hand, when it exceeds 10% by weight, when the resulting crosslinkable polymer is reacted with polyfunctional isocyanate, the resulting reactive polymer has an excessive degree of crosslinking, and the electrode sheet can be pressure-bonded to the resulting separator. May be difficult.

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

  When the glass transition temperature of the crosslinkable polymer is in the range of 0 to 100 ° C., in order to temporarily bond the electrode sheet to the separator including the reactive polymer film obtained from such a crosslinkable polymer, the separator is usually used. It is necessary to heat and crimp the electrode sheet to this. However, when the glass transition temperature of the crosslinkable polymer is in the range of 0 to 100 ° C., in particular, at room temperature or higher, most preferably, when it is 40 ° C. or higher, the separator does not have blocking properties at room temperature, The advantage that there is no need to sandwich a release sheet between the separators when they are stacked or rolled, and that they adhere to equipment related to bonding the electrode sheet to the separator, such as a guide roll There is an advantage that it is excellent in workability and handling.

  According to the present invention, a polyfunctional isocyanate is used as a crosslinking agent in order to crosslink such a crosslinkable polymer into a reactive polymer. Examples of such polyfunctional isocyanates include phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, diphenyl ether diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, and other aromatic, araliphatic, alicyclic, and aliphatic diisocyanates. A so-called isocyanate adduct obtained by adding a polyol such as trimethylolpropane to diisocyanate is also preferably used. Such polyfunctional isocyanate is usually used in the range of 0.1 to 10 parts by weight per 100 parts by weight of the crosslinkable polymer.

  As described above, the battery separator according to the present invention has a pair of films made of a reactive polymer having an epoxy group and containing a microcapsule encapsulating an epoxy resin curing agent. The insulating fine particles are preferably bonded and supported in a single layer so that there is a gap between the particles between the pair of films. Therefore, the pair of films are interposed via the insulating fine particles. Are attached to each other. However, in the present invention, it is not necessary for all the insulating fine particles to have a gap between them, and some of the insulating fine particles may be in contact with each other or attached to each other, and the pair of insulating fine particles via the insulating fine particles As long as the adhesion of the film made of the reactive polymer is not inhibited, a part of the insulating fine particles may be stacked and adhered and supported between the films.

  Based on an electron micrograph, if schematically shown in FIG. 1, a battery separator according to the present invention has a pair of films 1 and 1 made of a reactive polymer facing away from each other, and insulating fine particles 2 are preferable. Is sandwiched between a pair of these films and is supported by a single layer with a gap 3 therebetween. In other words, the pair of films made of the reactive polymer are bonded and bonded to each other via the insulating fine particles. Here, the reactive polymer plays the role of an adhesive.

  In the present invention, the insulating fine particles form a single layer between the films made of the reactive polymer, and are sandwiched and supported by the adhesive. The insulating fine particles are interspersed between the films made of the reactive polymer. With or without interstices (ie, in contact with each other) and without being stacked and dispersed and bonded.

  In order to obtain such a battery separator, in accordance with the present invention, insulating fine particles having a predetermined average particle diameter are used, and such insulating fine particles are formed as a single layer on a film made of a crosslinkable polymer. It is preferable that the film is uniformly dispersed and adhered and supported on the film, and the thickness of the film made of the crosslinkable polymer is preferably in the range of 0.3 to 5.0 μm. In particular, the insulating fine particles are made of the crosslinkable polymer. When adhering and supporting on the surface, the insulating fine particles can be dispersed and dispersed uniformly on the film made of a crosslinkable polymer so as to form a single layer while having a gap between them. preferable. In particular, according to the present invention, when the insulating fine particles are bonded and supported on the film made of the crosslinkable polymer, the insulating fine particles are 5 times the average particle diameter value between them, preferably 2 It is preferable to disperse the insulating fine particles uniformly in a single layer on the film made of the crosslinkable polymer so as to have a void having a value of twice or less, and to adhere and support the film on the film.

  Further, according to the present invention, the film made of another crosslinkable polymer that is laminated and bonded onto the insulating fine particles on the film made of the crosslinkable polymer has a thickness in the range of 0.3 to 5.0 μm. It is preferable to have. According to the present invention, since the crosslinkable polymer is cross-linked into a reactive polymer, the film made of the reactive polymer also preferably has a thickness in the range of 0.3 to 5.0 μm.

  According to the present invention, the insulating fine particles have an effective dimension of the obtained battery separator, in particular, an effective thickness, whereby the positive and negative electrodes are physically separated to have excellent insulating properties. In addition, it is preferable that the obtained battery is a spherical particle having an average particle diameter in the range of 1 to 100 μm so that the obtained battery has excellent characteristics and is easy to handle. When the average particle size of the insulating fine particles is smaller than 1 μm, even if the insulating fine particles are bonded and supported in a single layer between a pair of reactive polymer films, the resulting separator has positive and negative electrode sheets. Since it is difficult to physically isolate and the insulation effect is poor, the resulting battery may be inferior in performance. On the other hand, when the average particle diameter exceeds 100 μm, the thickness of the obtained separator becomes excessive, and similarly, the obtained battery may be inferior in performance.

  In particular, according to the present invention, it is preferable to make the thickness of the film made of the crosslinkable polymer smaller than the average particle diameter of the insulating fine particles used. Among them, according to the present invention, for example, an insulating fine particle having an average particle diameter of 5 to 75 μm, more preferably 10 to 50 μm, has a thickness of 0.3 to 5.0 μm, and more preferably 0.5 to 3.0 μm. It is preferable to adhere and carry on a film made of a crosslinkable polymer in the above range.

  When the thickness of the film made of the crosslinkable polymer is smaller than 0.3 μm, the film is inferior in adhesion to the insulating fine particles, and the obtained separator is also inferior in adhesion to the electrode sheet. On the other hand, when the thickness of the film made of the crosslinkable polymer is larger than 5.0 μm, the battery finally obtained using such a film is inferior in its characteristics.

  In the present invention, the thickness of the film made of the crosslinkable polymer and the thickness of the film made of the reactive polymer in the separator obtained using the crosslinkable polymer should be accurately determined from observation with a scanning electron microscope (SEM) photograph, respectively. Can do. As described above, the crosslinkable polymer is crosslinked to obtain a reactive polymer. Therefore, the thickness of the film made of the crosslinkable polymer and the thickness of the film made of the reactive polymer are substantially the same.

  In the present invention, the insulating fine particles may be organic or inorganic as long as they do not dissolve in the electrolytic solution used for battery production. Examples of the insulating fine particles that are organic materials include polymer particles such as fluororesin, polystyrene, and three-dimensionally cross-linked acrylic resins. Examples of the insulating fine particles that are inorganic materials include ceramics such as alumina and silica. Fine particles, silica balloons and the like can be mentioned, but are not limited thereto.

  The battery separator according to the present invention can be obtained, for example, as follows under the above-described conditions. Add a microcapsule containing a polyfunctional isocyanate and an epoxy resin curing agent to the solution of a crosslinkable polymer having a hydroxy group and an epoxy group, and mix and stir to encapsulate the polyfunctional isocyanate and the epoxy resin curing agent. Then, a solution of the crosslinkable polymer containing the microcapsules is obtained, and then this solution is applied onto a peelable film, for example, a peeled polyester film, and dried to enclose the polyfunctional isocyanate and the epoxy resin curing agent. A film made of the first crosslinkable polymer containing the microcapsules thus formed is formed on the peelable film. Next, the insulating fine particles are preferably dispersed uniformly in a single layer so as to have a gap between the particles on the film made of the first crosslinkable polymer on such a peelable film. Adhesive support. Next, the film made of the second crosslinkable polymer was laminated and bonded onto the insulating fine particles adhered and supported in a single layer on the film made of the first crosslinkable polymer in this way. After that, it is further heated so that the first and second crosslinkable polymers are cross-linked by reaction with the polyfunctional isocyanate to make each of them a reactive polymer, thus having an epoxy group, and further cured with an epoxy resin. A pair of films made of a reactive polymer having a cross-linked structure are spaced apart from each other, and the insulating fine particles form a single layer therebetween and are sandwiched between the pair of films. Thus, a battery separator bonded and supported can be obtained.

  The film made of the second crosslinkable polymer may be the same as the film made of the first crosslinkable polymer, and in addition to the type of polymer, the type of microcapsule encapsulating a polyfunctional isocyanate or an epoxy resin curing agent. However, the thickness may be different from the film made of the first crosslinkable polymer, but the thickness range is the same as the thickness range of the film made of the first crosslinkable polymer. , Preferably in the range of 0.3 to 5.0 μm.

  In the separator of the present invention, the film composed of the pair of reactive polymers is bonded to each other by the adhesiveness of the reactive polymer itself that forms the film via insulating fine particles. According to the present invention, as described above, the insulating fine particles are preferably dispersed on the film made of the first crosslinkable polymer, preferably in a single layer so as to have a gap therebetween, and uniformly dispersed, Adhering and supporting, and then laminating and laminating the second crosslinkable polymer film on the insulating fine particles forming a single layer on the first crosslinkable polymer film, and then heating, The first and second crosslinkable polymers are cross-linked to make each a reactive polymer. Here, according to the present invention, when the insulating fine particles are uniformly dispersed in a single layer on the film made of the first crosslinkable polymer and adhered and supported, the film made of the first crosslinkable polymer. A part of the solvent used in the preparation may be left, and the insulating fine particles may be dispersed on such a film so as to adhere and carry on the film. Preferably, the film is made of the first crosslinkable polymer. After the film is dried, the film is heated to an appropriate temperature to make it sticky, and the insulating fine particles are sprayed on such a film so as to adhere and carry on the film.

  In order to cause the crosslinkable polymer to react with the polyfunctional isocyanate as described above and to form a film made of the reactive polymer, as described above, the polyfunctional isocyanate is added to the solution of the crosslinkable polymer, After that, it may be heated. The amount of the polyfunctional isocyanate varies depending on the amount of the functional group in the crosslinkable polymer, the type of the polyfunctional isocyanate used, the heating temperature, and the like, but can be easily determined experimentally. Usually, in order to crosslink a crosslinkable polymer into a reactive polymer, polyfunctional isocyanate is blended in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the crosslinkable polymer. What is necessary is just to heat and react for 2 to 7 days at temperature.

  In the present invention, the microcapsules encapsulating an epoxy resin curing agent are stable in a solvent for forming a crosslinkable polymer solution, and stable when forming a film made of a crosslinkable polymer or a film made of a reactive polymer. Preferably, a curing agent that cures the epoxy resin at a temperature of 50 ° C. or higher, that is, a curing agent that is activated at a temperature of 50 ° C. or higher is included, and such a curing agent is contained in the electrolytic solution. It is to be eluted. In the present invention, such an epoxy resin curing agent microcapsule preferably has a particle size of 100 nm or less.

  As such an epoxy resin curing agent microcapsule, for example, NovaCure HX-3722 and HX-3748 manufactured by Asahi Kasei Corporation are preferably used. In the present invention, the mechanism by which the epoxy resin curing agent in the microcapsule elutes in the electrolyte solution is not necessarily clear, but the electrolyte solution dissolves the microcapsule wall, causing cracks, and the curing agent in the microcapsule is electrolyzed. Elutes into the liquid, or the electrolytic solution penetrates into the microcapsule, and the curing agent swells due to the electrolytic solution penetrated into the microcapsule, destroys the microcapsule wall, and the curing agent is eluted into the electrolytic solution. It seems to be a thing. As the curing agent encapsulated in the microcapsule, for example, an acid anhydride is used.

  Furthermore, in the battery separator according to the present invention, the reactive polymer has a gel fraction in the range of 20 to 100%, and preferably has a gel fraction in the range of 25 to 90%. Here, the gel fraction means that a solution containing A part by weight of the crosslinkable polymer and B part by weight of the polyfunctional isocyanate is cast on a peelable support, and after removing the solvent, the temperature is 50 ° C. for 3 days. The film is made of a reactive polymer by heating and crosslinking the crosslinkable polymer, and this film is immersed in a nonaqueous solvent for an electrolyte used in a battery at a temperature of 23 ° C. for 7 days. A value defined as (C / (A + B)) × 100 (%), assuming that the remaining reactive polymer is C parts by weight after substitution with a readily volatile solvent such as ethyl acetate or tetrahydrofuran and drying. It is.

  In the present invention, a reactive polymer film having a gel fraction in the range of 20 to 100% is not limited, but as described above, usually, with respect to 100 parts by weight of the crosslinkable polymer. It can be obtained by blending polyfunctional isocyanate in the range of 0.1 to 10 parts by weight and heating to allow the crosslinking reaction to proceed until the resulting reactive polymer is characteristically stabilized. Although the heating temperature for crosslinking of the crosslinkable polymer and the reaction time therefor depend on the crosslinkable polymer used, the polyfunctional isocyanate, the kind thereof, and the like, these reaction conditions can be determined by experiments. For example, heating and reacting at a temperature of 50 ° C. for 2 to 7 days usually completes the crosslinking reaction of the crosslinkable polymer with the polyfunctional isocyanate and stabilizes the resulting reactive polymer in terms of properties.

  Furthermore, according to the present invention, the reactive polymer preferably has a swelling degree of 5 times or more, particularly 10 times or more. Here, the degree of swelling means that a solution containing A part by weight of crosslinkable polymer A and part by weight of polyfunctional isocyanate B is cast on a peelable support, and after removing the solvent, it is heated at a temperature of 50 ° C. for 7 days. Then, the crosslinkable polymer is crosslinked to form a reactive polymer film, and the weight in a swollen state when this film is immersed in a nonaqueous solvent for an electrolyte used in a battery at a temperature of 23 ° C. for 7 days is defined as D. Next, the non-aqueous solvent in the film is replaced with a readily volatile solvent such as ethyl acetate or tetrahydrofuran, and after the solvent is dried and removed, the remaining reactive polymer is C parts by weight. It is a value defined as D / C. This degree of swelling can be appropriately adjusted depending on the monomer composition and molecular weight distribution of the crosslinkable polymer, the amount of functional groups of the crosslinkable polymer, the amount of polyfunctional isocyanate used, and the like. According to the present invention, when the swelling degree of the reactive polymer is less than 5 times, the resulting battery may be inferior in characteristics.

  Thus, in the battery separator according to the present invention, the reactive polymer has a gel fraction in the range of 20 to 100% and a swelling degree of 5 times or more. Insulating fine particles having a thickness in the range of ˜5.0 μm and an average particle diameter in the range of 1 to 100 μm are adhered and supported therebetween.

  As described above, the battery separator according to the present invention has a pair of films made of a reactive polymer facing away from each other, and the insulating fine particles form a single layer between the pair of films, Since the pair of films are bonded to each other through the insulating fine particles, the positive and negative electrodes can be physically separated from each other. Therefore, the insulating property between the electrode sheets is excellent, and in the space in the opposing film, there are voids between the insulating fine particles on the film, and the ion permeability is excellent. Furthermore, when assembling the battery, the electrolyte quickly penetrates into the voids inside the separator, so that the productivity of the battery is excellent. Moreover, in the battery, since the electrolytic solution fills the voids inside the separator with the electrolytic solution, the obtained battery is excellent in performance.

  Moreover, the battery separator according to the present invention is not reacted in the absence of polyfunctional isocyanate or until the epoxy resin curing agent in the microcapsule is activated by contact with the electrolytic solution. Since it does not crosslink, it is stable and does not deteriorate even when stored for a long period of time.

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

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

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

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

  That is, after preparing the electrode sheet / separator laminate in a battery container, the electrolyte solution is injected into the battery container and heated to maintain reactivity while maintaining the temporary adhesion of the electrode sheet / separator laminate. The polymer is swollen and the epoxy resin curing agent is eluted from the microcapsules dispersed in the reactive polymer, activated, and the reactive polymer is crosslinked and cured by the epoxy group, so that the electrode sheet and the separator are separated. A stronger bond can be formed between them, and thus a battery having an electrode sheet / separator assembly can be obtained.

  According to the present invention, as described above, since the reactive polymer is previously crosslinked so as to have a gel fraction in the range of 20 to 100%, the electrode sheet / separator laminate is placed in the electrolyte solution. Even when immersed, elution of the reactive polymer into the electrolytic solution is prevented or reduced, so that it is effectively used for adhesion of the electrode sheet. Moreover, since the reactive polymer has a degree of swelling of 5 times or more, the reactive polymer swells at the interface between the separator and the electrode sheet temporarily bonded thereto, and the reactive polymer has an epoxy group and an epoxy. Since it crosslinks by reaction with the resin curing agent, the electrode sheet is more firmly bonded to the separator to give an electrode sheet / separator assembly. According to the present invention, the reactive polymer thus has a degree of swelling substantially equal to that after crosslinking even after crosslinking. The characteristics of the obtained battery are superior as the degree of swelling increases.

  According to the present invention, the electrode sheet is placed on the surface of the reactive polymer film forming the separator, and the electrode sheet is pressurized while being heated to a temperature at which the deformation of the separator does not occur. A part of the separator is press-fitted into the separator, so to speak, the electrode sheet is temporarily bonded to the separator to form an electrode sheet / separator laminate. Injecting into a container, heating, activating the epoxy resin curing agent encapsulated in the microcapsule, reacting the epoxy group of the reactive polymer forming the separator, further crosslinking the reactive polymer, An electrode sheet / separator assembly is obtained. That is, the electrode sheet is actually bonded to the separator.

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

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

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

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

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

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

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

(Reaction polymer gel fraction)
In accordance with the operation in each Example or each Comparative Example, a solution containing A part by weight of crosslinkable polymer and B part by weight of polyfunctional isocyanate B was cast on the peeled polyester film, and after removing the solvent, the temperature was 50 ° C. Heated for 7 days to crosslink the crosslinkable polymer to form a film made of a reactive polymer. This film was immersed in a nonaqueous solvent for an electrolyte used in a battery at a temperature of 23 ° C. for 7 days, and then the nonaqueous After the solvent was replaced with ethyl acetate and dried, when the remaining reactive polymer was C parts by weight, (C / (A + B)) × 100 (%) was taken as the gel fraction.

(Swelling degree of reactive polymer)
In accordance with the operation in each Example or each Comparative Example, a solution containing A part by weight of crosslinkable polymer and B part by weight of polyfunctional isocyanate B was cast on the peeled polyester film, and after removing the solvent, the temperature was 50 ° C. Heat for 7 days to crosslink the crosslinkable polymer to form a reactive polymer film, and the weight in the swollen state when this film is immersed in a nonaqueous solvent for the electrolyte used in the battery at a temperature of 23 ° C. for 7 days Then, when the non-aqueous solvent in the film is replaced with ethyl acetate, the solvent is dried and removed, and the remaining reactive polymer is C parts by weight, D / C is the degree of swelling. did.

Example 1
(Preparation of crosslinkable polymer)
N, N-dimethylacrylamide 35 parts by weight Butyl acrylate 50 parts by weight Acrylonitrile 10 parts by weight Glycidyl methacrylate 5 parts by weight 4-hydroxybutyl acrylate 0.5 parts by weight Azobisisobutyronitrile 0.2 parts by weight Ethyl acetate 150 parts by weight

The monomer, polymerization initiator, and solvent were charged into a four-necked flask equipped with a stirrer, a nitrogen inlet tube, and a condenser, and the inside of the flask was purged with nitrogen under stirring. Next, polymerization is carried out at 60 to 65 ° C. for 8 hours with stirring in a warm water bath, further heated to 75 ° C. and held at this temperature for 3 hours, and then added with ethyl acetate to give a concentration of 20% by weight. A crosslinkable polymer solution was obtained. This crosslinkable polymer had a weight average molecular weight of 6.0 × 10 ⁵ and a glass transition temperature of 8 ° C.

  0.2 parts by weight of trifunctional isocyanate obtained by adding 3 parts by mole of hexamethylene diisocyanate to 1 mole part of trimethylolpropane and 100 parts by weight of the solid content of the crosslinkable polymer solution, and epoxy resin curing agent microcapsules ( Asahi Kasei Co., Ltd. NovaCure HX3722) 2.5 parts by weight was added and stirred and mixed to obtain a crosslinkable polymer solution containing microcapsules encapsulating a polyfunctional isocyanate and an epoxy resin curing agent.

  After applying this crosslinkable polymer solution onto a 40 μm thick polyester film peel-treated, an applicator is used, followed by heating to 70 ° C. and drying to form a film made of the first crosslinkable polymer having a thickness of 0.8 μm. It formed on the said polyester film.

  While maintaining the film of the first crosslinkable polymer on the polyester film at a temperature of 85 ° C., spherical alumina particles having an average particle diameter of 18 to 22 μm and a maximum particle diameter of 32 μm are simply formed on the polyester film so as to have a gap therebetween. The layers were uniformly dispersed and adhered and supported on the film made of the first crosslinkable polymer.

Next, in the same manner as the film made of the first crosslinkable polymer, a film made of the second crosslinkable polymer having a thickness of 0.8 μm is formed on the polyester film, and the second crosslinkable polymer on the polyester film is formed. After laminating the film consisting of the above-mentioned film along the alumina particles on the film made of the first crosslinkable polymer on the polyester film, the films are bonded together through a heated rubber roll having a temperature of 85 ° C., and further placed in a thermostatic chamber having a temperature of 50 ° C. After 7 days, the crosslinkable polymer is cross-linked to become a reactive polymer, and thus a pair of films made of the reactive polymer are facing away from each other, and the insulating fine particles have a gap therebetween, A battery separator according to the present invention comprising a layer and sandwiched and supported between the pair of films is a polyester. It was obtained as a laminate sandwiched Rufirumu. This separator had a basis weight (weight per m ² , hereinafter the same) 35 g / m ² and an average thickness of 30 μm. This separator had a cross-sectional structure as shown in FIG.

  One polyester film is peeled from the laminate sandwiched between the polyester films to expose the surface of the separator (that is, the surface of a film made of a reactive polymer), and the positive electrode sheet is overlaid on the surface of the separator. The positive electrode sheet was pressure-bonded to the surface of the separator using a heat laminating roll having a temperature of 85 ° C. Next, the other polyester film is peeled off from the separator, the back surface of the separator is exposed, the negative electrode sheet is overlaid on the back surface of the separator, and the negative electrode sheet is similarly used using a heat bonding roll having a temperature of 85 ° C. Was bonded to the back surface of the separator, thus obtaining a negative electrode sheet / separator / positive electrode sheet laminate (hereinafter sometimes referred to as an electrode sheet / separator laminate).

(Preparation of electrolyte)
In an argon-substituted glove box, electrolyte salt lithium hexafluorophosphate (LiPF ₆ ) was dissolved in an ethylene carbonate / ethyl methyl carbonate mixed solvent (volume ratio 1/2) to a concentration of 1.2 mol / L. An electrolyte solution was prepared.

(Battery assembly)
The electrode sheet / separator laminate is charged into a 2016-size coin-type battery can that also serves as a positive and negative electrode plate, the electrolyte is poured into the coin-type battery can, and then the battery can is sealed. Was made. Thereafter, this work-in-process is put into a thermostatic chamber at a temperature of 50 ° C. for 7 days to activate the epoxy resin curing agent, and to crosslink the epoxy groups in the reactive polymer in the electrode / separator laminate. A coin-type lithium ion secondary battery having a negative electrode sheet / separator / positive electrode sheet assembly (hereinafter sometimes referred to as an electrode sheet / separator assembly) is bonded and integrated with a positive and negative electrode sheet. Obtained.

  The characteristics of the coin-type lithium ion secondary battery thus obtained were evaluated as follows.

(Evaluation of discharge load characteristics)
The obtained battery was charged and discharged five times at a rate of 0.2 CmA, then charged at a rate of 0.2 CmA, and then discharged at a rate of 2.0 CmA, and a rate of 2.0 CmA. The discharge load characteristic was evaluated by the ratio of the discharge capacity at a rate / discharge capacity at a rate of 0.2 CmA.

(Battery heat resistance)
The obtained battery was heated at 150 ° C. for 1 hour, and then the battery characteristics were examined. The case where a short circuit was observed was evaluated as x (battery was inferior in heat resistance), and the case where a short circuit was not observed was evaluated as o (battery was excellent in heat resistance).

(Separator insulation)
When preparing an electrode sheet / separator laminate, a positive electrode sheet is bonded to the surface of a 1.5 cm square separator and pressure bonded with a heating roll at 85 ° C., and the obtained positive electrode sheet / separator laminate is cut into a 2 cm square. did. Similarly, a 1.0 cm square negative electrode sheet was bonded to the back surface of the positive electrode sheet / separator laminate, and pressure-bonded with a heating roll at 85 ° C. to obtain adhesiveness of the electrode sheet / separator laminate. The positive electrode sheet and the negative electrode sheet of the electrode sheet / separator laminate thus obtained were connected to the terminals of the tester, and it was examined whether there was conduction between the electrode sheets. The case where there was no conduction between the electrode sheets was marked as ◯ (the separator was excellent in insulation), and the case where there was conduction between the electrode sheets was marked as x (the separator was poor in insulation).

(Electrode sheet / separator adhesion)
The electrode sheet / separator laminate is cut to a width of 10 mm, immersed in an electrolytic solution containing the same trifunctional isocyanate as used for battery production at a temperature of 50 ° C. for 7 days, and then the porous film is peeled off in a wet state. , When there was resistance, it was marked as ◯ (excellent in adhesiveness), and when it was already peeled and there was almost no resistance, it was marked as x (inferior in adhesiveness).

Examples 2 and 3
A separator was obtained in the same manner as in Example 1 except that spherical alumina particles having an average particle diameter shown in Table 1 were used, and a coin-type lithium ion secondary battery was obtained using the separator. Table 1 shows the basis weight of the obtained separator, the discharge load characteristics and heat resistance of the obtained battery, the insulation of the separator, and the adhesion of the electrode sheet / separator.

Example 4
In Example 1, a separator was obtained in the same manner as in Example 1 except that films each having a thickness of 0.5 μm were used as the films made of the first and second crosslinkable polymers, and a coin type was obtained using this separator. A lithium ion secondary battery was obtained. Table 1 shows the basis weight of the obtained separator, the discharge load characteristics and heat resistance of the obtained battery, the insulation of the separator, and the adhesion of the electrode sheet / separator.

Example 5
In Example 1, a separator is obtained in the same manner as in Example 1 except that films each having a thickness of 2.0 μm are used as the films made of the first and second crosslinkable polymers. A lithium ion secondary battery was obtained. Table 1 shows the basis weight of the obtained separator, the discharge load characteristics and heat resistance of the obtained battery, the insulation of the separator, and the adhesion of the electrode sheet / separator.

Example 6
In Example 1, a separator was obtained in the same manner as in Example 1 except that spherical polystyrene particles having an average particle diameter of 15 μm and a maximum particle diameter of 20 μm were used in place of the alumina particles. An ion secondary battery was obtained. Table 1 shows the basis weight of the obtained separator, the discharge load characteristics and heat resistance of the obtained battery, the insulation of the separator, and the adhesion of the electrode sheet / separator.

Example 7
In Example 1, 3 parts by weight of trifunctional isocyanate obtained by adding 3 parts by mole of hexamethylene diisocyanate to 1 part by mole of trimethylolpropane is added to the crosslinkable polymer solution with respect to 100 parts by weight of the solid content to obtain polyfunctionality. A separator was obtained in the same manner except that a crosslinkable polymer solution containing a crosslinking agent was obtained, and a coin-type lithium ion secondary battery was obtained using the separator. Table 1 shows the basis weight of the obtained separator, the discharge load characteristics and heat resistance of the obtained battery, the insulation of the separator, and the adhesion of the electrode sheet / separator.

Example 8
Acrylylmorpholine 45 parts by weight Acrylonitrile 10 parts by weight 3,4-Epoxycyclohexylmethyl methacrylate
5 parts by weight Butyl acrylate 40 parts by weight Hydroxybutyl acrylate 0.5 parts by weight Azobisisobutyronitrile 0.3 part by weight Ethyl acetate 150 parts by weight

The monomer, polymerization initiator, and solvent were charged into a four-necked flask equipped with a stirrer, a nitrogen inlet tube, and a condenser, and the inside of the flask was purged with nitrogen under stirring. Next, polymerization is carried out at 62 ° C. for 8 hours with stirring in a warm water bath, and further heated to 75 ° C. and held at this temperature for 3 hours, followed by addition of ethyl acetate to form a cross-link having a concentration of 20% by weight. A functional polymer solution was obtained. This crosslinkable polymer had a weight average molecular weight of 5.5 × 10 ⁵ and a glass transition temperature of 32 ° C.

  A separator was obtained using the crosslinkable polymer solution in the same manner as in Example 1, and an electrode sheet / separator laminate was obtained using the separator.

  A coin-type lithium ion secondary battery was obtained in the same manner as in Example 1 using the same electrolytic solution as in Example 1. Table 1 shows the basis weight of the obtained separator, the discharge load characteristics and heat resistance of the obtained battery, the insulation of the separator, and the adhesion of the electrode sheet / separator.

Example 9
The solution of the crosslinkable polymer obtained in Example 1 was placed in a flask, and while stirring, n-heptane was added dropwise thereto to remove the clouded and precipitated polymer. Thus, the crosslinkable polymer was reprecipitated and purified. . This crosslinkable polymer was again dissolved in ethyl acetate. This was repeated twice to purify the crosslinkable polymer. This crosslinkable polymer was dissolved in ethyl acetate to obtain a 20 wt% crosslinkable polymer solution.

  A separator was obtained in the same manner as in Example 1 except that this crosslinkable polymer solution was used, and a battery was obtained using this separator. Table 2 shows the gel fraction and swelling degree of the obtained reactive polymer, the basis weight of the obtained separator, the discharge load characteristics and heat resistance of the obtained battery, the insulation of the separator, and the adhesion of the electrode sheet / separator. Show.

Comparative Example 1
A crosslinkable polymer solution was obtained in the same manner except that the trifunctional isocyanate was not added to the crosslinkable polymer solution obtained in Example 1. Using this crosslinkable polymer solution, a separator was obtained in the same manner as in Example 1, and an electrode sheet / separator laminate was obtained using this, and a coin-type lithium ion secondary battery was obtained using this separator. .

  Table 2 shows the basis weight of the obtained separator, the discharge load characteristics and heat resistance of the obtained battery, the insulation of the separator, and the adhesion of the electrode sheet / separator.

Comparative Example 2
A separator was obtained in the same manner except that 10 parts by weight of trifunctional isocyanate was used for the crosslinkable polymer solution obtained in Example 1 with respect to 100 parts by weight of the solid content, and an electrode sheet / separator laminate was obtained using this separator. Using this, a coin-type lithium ion secondary battery was obtained. Table 2 shows the gel fraction and swelling degree of the obtained reactive polymer, the basis weight of the obtained separator, the discharge load characteristics and heat resistance of the obtained battery, the insulation of the separator, and the adhesion of the electrode sheet / separator. Show.

Comparative Example 3
To the crosslinkable polymer solution obtained in Example 1, 1 part by weight of trifunctional isocyanate formed by adding 3 parts by mole of hexamethylene diisocyanate to 1 part by mole of trimethylolpropane is added to 100 parts by weight of the solid content, and the mixture is stirred and mixed. Thus, a crosslinkable polymer solution containing a polyfunctional crosslinking agent was obtained. After applying this crosslinkable polymer solution to a 40 μm thick polyester film subjected to a release treatment using an applicator, it is heated to 70 ° C. and dried to form a 0.8 μm thick first and second crosslinkable polymer. The resulting film was formed on the polyester film.

  After these films made of the first and second crosslinkable polymers on the polyester film were superposed, they were pasted together through a heated rubber roll at a temperature of 85 ° C., and further placed in a temperature-controlled room at a temperature of 50 ° C. for 7 days. A part of the functional polymer was cross-linked to obtain a reactive polymer, and thus a battery separator in which the reactive polymer was bonded together was obtained as a laminate sandwiched between polyester films.

  One polyester film is peeled from the laminate sandwiched between the polyester films to expose the surface of the separator (that is, the surface of a film made of a reactive polymer), and the positive electrode sheet is overlaid on the surface of the separator. The positive electrode sheet was pressure-bonded to the surface of the separator using a heat laminating roll having a temperature of 85 ° C. Next, the other polyester film is peeled off from the separator, the back surface of the separator is exposed, the negative electrode sheet is overlaid on the back surface of the separator, and the negative electrode sheet is similarly used using a heat bonding roll having a temperature of 85 ° C. Was pressure-bonded to the back surface of the separator, thus obtaining an electrode sheet / separator laminate.

  In the same manner as in Example 1, a coin-type lithium ion secondary battery was obtained using this electrode sheet / separator laminate. Table 2 shows the basis weight of the obtained separator, the discharge load characteristics and heat resistance of the obtained battery, the insulation of the separator, and the adhesion of the electrode sheet / separator.

Comparative Example 4
In Example 1, a separator was obtained in the same manner except that silica fine particles having an average particle diameter of 0.01 μm were used in place of alumina particles, and this was used to produce an electrode sheet / A separator laminate was obtained, and a coin-type lithium ion secondary battery was obtained using the separator laminate. Table 2 shows the basis weight of the obtained separator, the discharge load characteristics and heat resistance of the obtained battery, the insulation of the separator, and the adhesion of the electrode sheet / separator.

  As shown in Table 1 and Table 2, the battery separator according to the present invention provides a battery having excellent discharge load characteristics and heat resistance, as well as excellent insulation properties of the separator and adhesion of the electrode sheet / separator. .

  On the other hand, in Comparative Example 1, the film in the separator is not crosslinked. Therefore, although the film in the separator is crosslinked by the epoxy resin curing agent at the stage of assembling the battery, at the same time, at least a part of the film dissolves in the electrolyte solution, so it does not contribute to the adhesion between the electrode sheet and the separator. Thus, the battery obtained is inferior in electrode sheet / separator adhesion and battery heat resistance.

  According to Comparative Example 2, as a result of excessive crosslinking of the reactive polymer in the separator, the degree of swelling is 3 times, the discharge load characteristics are low, and the heat resistance is poor. According to Comparative Example 3, the battery separator has low discharge load characteristics and poor heat resistance because the insulating fine particles are sandwiched and not adhered between the films made of the reactive polymer. In Comparative Example 4, since the average particle size of the insulating fine particles is too small, similarly, the discharge load characteristics are low and the heat resistance is also poor.

It is principal part sectional drawing which shows an example of the separator for batteries by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Reactive polymer film 2 ... Insulating fine particle 3 ... Void

Claims (6)

  A pair of films made of a reactive polymer having an epoxy group and further containing a microcapsule encapsulating an epoxy resin curing agent and having a crosslinked structure are spaced apart from each other, and the insulating fine particles are in between. A battery separator, comprising a single layer and being sandwiched and supported between the pair of films.   The reactive polymer has a gel fraction in the range of 20 to 100% and a swelling degree of 5 times or more, and the film made of this reactive polymer has a thickness in the range of 0.3 to 5.0 μm, and has an insulating property. The battery separator according to claim 1, wherein the fine particles have an average particle diameter in the range of 1 to 100 μm.   A microcapsule containing a polyfunctional isocyanate and an epoxy resin curing agent is mixed in a solution of a crosslinkable polymer having a hydroxy group and an epoxy group, and the resulting solution of the crosslinkable polymer is applied onto a peelable film and dried. Then, a film made of the first crosslinkable polymer including the microcapsules encapsulating the polyfunctional isocyanate and the epoxy resin curing agent is formed on the peelable film, and then on the peelable film thus obtained. Insulating fine particles are dispersed in a single layer on a film made of the first crosslinkable polymer, and adhered and supported on the film made of the first crosslinkable polymer. Mixing the solution of the crosslinkable polymer with microcapsules containing polyfunctional isocyanate and epoxy resin curing agent The crosslinkable polymer solution is applied onto a peelable film and dried to prepare a film composed of a second crosslinkable polymer containing microcapsules containing the polyfunctional isocyanate and the epoxy resin curing agent. A film made of the second crosslinkable polymer is superposed on and bonded to the insulating fine particles on the film made of the first crosslinkable polymer, and then heated to heat the first and second crosslinkable polymers. Are reacted by the reaction with the above polyfunctional isocyanate to make each of them a reactive polymer, thus containing a microcapsule having an epoxy group and encapsulating an epoxy resin curing agent and having a crosslinked structure. A pair of films made of a conductive polymer are spaced apart from each other, and the insulating fine particles form a single layer between the pair of films. Manufacturing method of the battery separator are bonded carried sandwiched arm.   A microcapsule containing a polyfunctional isocyanate and an epoxy resin curing agent is mixed in a solution of a crosslinkable polymer, and the resulting crosslinkable polymer solution is applied onto a peelable film and dried, and then the above polyfunctional isocyanate and epoxy are mixed. The manufacturing method of the battery separator of Claim 3 which forms the film of thickness 0.3-5.0 micrometers which consists of a crosslinkable polymer containing the microcapsule which included the resin hardening agent on the said peelable film.   The reactive polymer has a gel fraction in the range of 20 to 100% and a swelling degree of 5 times or more, and the film made of the reactive polymer has a thickness in the range of 0.3 to 5.0 μm. The manufacturing method of the separator for batteries of description. An electrode sheet is laminated on the battery separator according to claim 1 or 2 and pressed to form an electrode sheet / separator laminate. After the laminate is charged into a battery container, an electrolyte solution is placed in the battery container. And heating the epoxy resin curing agent to crosslink and cure the reactive polymer with its epoxy group, thereby bonding the electrode sheet to the separator.

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