JP2005209474A - Reactive polymer carrying porous film for battery separator and its use - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reactive polymer carrying porous film for a battery separator, which has sufficient adhesiveness between an electrode and the separator and low internal resistance, and which can be suitably used for manufacturing a battery having high rate characteristics and a method for manufacturing a battery by use of the reactive polymer carrying porous film. <P>SOLUTION: A probe with a diameter of 1mm is placed on a porous film under a load of 70g, and while heating this porous film from a room temperature at a temperature raising speed of 2°C/minute, its thickness is measured by using a penetrating probe type thermomechanical analyzer. At this time, a porous film the temperature of which is 200°C or more when the thickness of the porous film becomes 1/2 of the thickness at the time when the probe is placed on it is used as a base material porous film, and a reactive polymer formed by making a cross-linking polymer having an at least one kind of reactive group selected from a 3-oxetanyl group react to an epoxy group in a molecule is reacted to polycarboxylic acid, and by making the base material porous film carry the reactive polymer formed by cross-linking a part of it, in order to make the reactive polymer carrying porous film for the battery separator. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  INDUSTRIAL APPLICABILITY The present invention is useful for manufacturing a battery, and the battery thus manufactured has excellent adhesion to an electrode even under a high temperature environment, and does not melt or break, and has a small heat shrinkage. The present invention relates to a reactive polymer-supported porous film for a battery separator that functions as a separator and therefore has excellent safety, and a method for producing a battery using such a reactive polymer-supported porous film.

  Conventionally, as a method of manufacturing a battery, a positive electrode and a negative electrode are laminated with a separator for preventing a short circuit between the electrodes, or a positive (negative) electrode, a separator, a negative (positive) electrode, and a separator are laminated. It is known that the electrode / separator laminate is stacked in order and wound into an electrode / separator laminate, and after the electrode / separator laminate is charged into the battery container, an electrolytic solution is injected into the battery container and sealed. (For example, see Patent Documents 1 and 2).

  However, according to the battery obtained in this way, the electrode expands or contracts during use, and the adhesion between the electrode and the separator is deteriorated, battery characteristics are deteriorated, and internal short circuit is caused. As a result, the battery was heated and heated, and in some cases, the separator could even melt and break.

  On the other hand, especially in the production of stacked batteries, in many cases, the polyvinylidene fluoride resin solution is used as an adhesive, the electrode and the separator are bonded, and then the solvent used in the resin solution is removed under reduced pressure. The method to do is adopted. However, according to such a method, there are problems that the process is complicated, the quality of the obtained product is difficult to stabilize, and the adhesion between the electrode and the separator is not sufficient (for example, patent document) 3).

  In addition, 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, it is important to improve the heat resistance of the battery separator and reduce the heat shrinkage rate under such a high temperature environment. 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.

That is, conventionally, such a porous film for a separator that is excellent in heat resistance, does not melt or break, and has a low heat shrinkage rate under a high temperature environment has not been known.
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 adhesiveness with the electrode even in a high temperature environment. An object of the present invention is to provide a reactive polymer-supported porous film for battery separators that functions as a separator with low heat shrinkage, without melting or rupturing, and thus excellent in safety. . Furthermore, this invention aims at providing the manufacturing method of the battery using such a reactive polymer carrying | support porous film.

  According to the present invention, a probe having a diameter of 1 mm is placed on a porous film under a load of 70 g using a needle-inserted probe thermomechanical analyzer, and the porous film is heated from room temperature at a rate of temperature rise of 2 ° C./min. The thickness of the porous film is measured while heating the porous film, and the temperature at which the thickness of the porous film is ½ of the thickness when the probe is mounted is 200 ° C. or higher. A reactive material obtained by reacting a crosslinkable polymer having at least one reactive group selected from 3-oxetanyl group and epoxy group in the molecule with a polycarboxylic acid, and partially crosslinking it. There is provided a reactive polymer-supported porous film for a battery separator, characterized in that a polymer is supported on a substrate porous film.

  In particular, in the present invention, the porous film preferably comprises a polyolefin resin composition comprising a polyolefin resin having a weight average molecular weight of at least 500,000 and a crosslinkable rubber having a double bond in the molecular chain. It is obtained by crosslinking a crosslinkable rubber.

  Further, according to the present invention, a crosslinkable polymer having at least one reactive group selected from a 3-oxetanyl group and an epoxy group in the molecule and a polycarboxylic acid are supported on the substrate porous film, For the battery separator described above, which is characterized by reacting a part of the reactive group with a polycarboxylic acid, partially crosslinking the reactive polymer, and thus forming a reactive polymer on the substrate porous film. A method for producing a reactive polymer-supported porous film is provided.

  Furthermore, according to the present invention, an electrode is laminated on the reactive polymer-supported porous film described above to obtain an electrode / reactive polymer-supported porous film laminate, and this electrode / reactive polymer-supported porous film laminate. Is charged into the battery container, and an electrolytic solution containing a cationic polymerization catalyst is injected into the battery container to electrolyze at least a part of the reactive polymer at least in the vicinity of the interface between the porous film and the electrode. Provided is a method for producing a battery, characterized in that it is swollen in a liquid, or eluted in an electrolytic solution, cationically polymerized, and at least a part of the electrolytic solution is gelled to bond a porous film and an electrode. Is done.

  The reactive polymer-supported porous film for a battery separator according to the present invention has a reactive polymer of the crosslinkable polymer having at least one reactive group selected from a 3-oxetanyl group and an epoxy group in the molecule. A part is reacted with a polycarboxylic acid, a part of the crosslinkable polymer is cross-linked to form a reactive polymer, and this is supported on the base porous film. The film was placed on a porous film with a probe having a diameter of 1 mm under a load of 70 g using a needle probe type thermomechanical analyzer, and the porous film was heated from room temperature at a heating rate of 2 ° C./min. However, the thickness of the porous film was measured, and at that time, it had a thermal characteristic that the temperature when the thickness of the porous film was ½ of the thickness when the probe was mounted was 200 ° C. or more. Is shall. In particular, according to the present invention, such a porous substrate film comprises a polyolefin resin composition comprising a polyolefin resin having a weight average molecular weight of at least 500,000 and a crosslinkable rubber having a double bond in the molecular chain. Those obtained by crosslinking the crosslinkable rubber are preferred.

  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 remaining reactive group of the polymer is cationically polymerized, the reactive polymer is further cross-linked, and at least a part of the electrolytic solution is gelled, thereby firmly bonding the porous film and the electrode, and the electrode / porous film. A joined body can be obtained.

  Here, 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 electrolyte solution. Occasionally, the reactive polymer is prevented from eluting and diffusing into the electrolyte from the electrode / reactive polymer-supported porous film laminate, and the reactive polymer swells, resulting in the use of a small amount of reactive polymer. As a result, the electrode can be adhered to the porous film (separator), and the porous film has excellent ion permeability and functions well as a separator. Further, the reactive polymer is not excessively eluted and diffused in the electrolytic solution, and does not adversely affect the electrolytic solution.

  Furthermore, according to the present invention, the porous film in the adhesive-carrying porous film is preferably crosslinkable having a double bond in the molecular chain and a polyolefin resin having a weight average molecular weight of at least 500,000 as described above. It is made of a polyolefin resin composition with rubber, and is obtained by crosslinking the crosslinkable rubber and has a heat-resistant temperature of 200 ° C. or higher. By using the adhesive-supporting porous film according to the present invention without forming a film and functioning as a separator having a small heat shrinkage, a battery excellent in safety at high temperatures can be obtained.

  A reactive polymer-supported porous film for a battery separator according to the present invention was prepared by placing a probe having a diameter of 1 mm on a porous film under a load of 70 g using a needle-inserted probe thermomechanical analyzer. The thickness of the porous film is measured while heating the porous film at a rate of temperature increase of 2 ° C./min. At that time, the thickness of the porous film is ½ of the thickness when the probe is mounted. A porous film having a temperature of 200 ° C. or higher is used as a base porous film, and a crosslinkable polymer having at least one reactive group selected from a 3-oxetanyl group and an epoxy group in the molecule and a polycarboxylic acid. A reactive polymer obtained by reacting and partially crosslinking is supported on a porous substrate film.

  According to the present invention, the porous substrate film preferably comprises a polyolefin resin composition comprising a polyolefin resin having a weight average molecular weight of at least 500,000 and a crosslinkable rubber having a double bond in the molecular chain. It is obtained by crosslinking a crosslinkable rubber.

  That is, according to the present invention, a cross-linkable polymer having at least one reactive group selected from a 3-oxetanyl group and an epoxy group in the molecule and a base porous film having the above-described thermal properties are added to the polyporous polymer film. Reacting with a carboxylic acid and partially supporting a reactive polymer formed by crosslinking to form a reactive polymer-supporting porous film for a battery separator, and the porous film as a separator as described later For a functioning battery, this separator does not melt or break easily even at high temperatures, maintains its thickness, has a low thermal shrinkage, and prevents short-circuiting between electrodes. Can be improved.

  Here, the measurement of the thickness of the substrate porous film using the probe-type thermomechanical analyzer will be described. First, when the tip of a cylindrical probe having a diameter of 1 mm to which a load is applied is placed on the porous film, the porous film is brought into contact with the tip of the probe by the load from the probe. Its thickness is somewhat reduced. The thickness of the porous film at this time is referred to as the initial thickness. Thereafter, as the temperature of the porous film rises, its thickness gradually decreases, but when the resin constituting the porous film melts or becomes a semi-molten state, a large thickness reduction occurs. Due to the subsequent shrinkage, a phenomenon in which the thickness returns slightly is observed. Furthermore, when the porous film is continuously heated, the thickness starts decreasing again after the thickness increases due to the shrinkage. Therefore, according to the present invention, the temperature of the porous film when the thickness of the porous film continues to decrease and becomes 1/2 of the initial thickness is defined as the heat resistant temperature of the porous film. . If this heat-resistant temperature is high, the porous film can maintain its thickness up to a higher temperature without melting and rupturing. Therefore, by using such a porous film as a separator, A battery excellent in safety under the environment can be obtained.

  Therefore, according to the present invention, the substrate porous film is not particularly limited as long as it has solvent resistance and oxidation-reduction resistance in addition to the above thermal characteristics. For example, polyethylene, polypropylene, A porous film made of polyolefin resin such as polybutylene, polyamide, cellulose acetate, polyacrylonitrile, or the like can be used.

  However, according to the present invention, the base porous film is composed of a polyolefin resin composition comprising a polyolefin resin having a weight average molecular weight of 500,000 or more and a crosslinkable rubber having a double bond in the molecular chain. A porous film obtained by crosslinking a functional rubber is preferably used. The polyolefin resin composition may contain a polyolefin resin or a thermoplastic elastomer having a weight average molecular weight of less than 500,000 as necessary.

  Examples of the polyolefin resin having a weight average molecular weight of 500,000 or more include polyolefin resins such as polyethylene and polypropylene. These polyolefin resins may be used alone or in admixture of two or more. However, according to the present invention, among these, an ultrahigh molecular weight polyethylene resin having a weight average molecular weight of 500,000 or more is preferably used because the obtained porous film has high strength.

  Examples of the crosslinkable rubber include diene polymers having a double bond in the molecule such as polybutadiene and polyisoprene, and ternary copolymer having a double bond in the molecule such as ethylene-propylene-diene monomer. A coalescence or the like is preferably used. In the ethylene-propylene-diene monomer terpolymer, examples of the diene monomer include dicyclopentadiene, ethylidene norbornene, and hexadiene. Among these, ethylidene norbornene is preferably used from the viewpoint of crosslinking reactivity. . That is, the terpolymer having ethylidene norbornene as a constituent component has excellent crosslinking reactivity, and the heat resistance of the resulting porous film can be improved more reliably. In addition, for example, a terpolymer having ethylidene norbornene as a constituent component has an alicyclic structure derived from a diene monomer and a double bond, but a part of the double bond is hydrogenated. It is also possible to use. Further, these terpolymers may be any of random copolymers, block copolymers, graft copolymers, and the like. Such terpolymers are commercially available as various EPDMs.

  In order to sufficiently crosslink such a terpolymer, the proportion of the diene monomer component in the terpolymer is preferably 3% by weight or more based on the total weight of ethylene, propylene and diene monomer. A range of 20% by weight is particularly preferred. In particular, according to the present invention, the ratio of ethylene / propylene / diene monomer component is 0.5 to 0.75 / 0.05 to 0.47 / 0.03 to 0.2 in weight ratio. A polymer is preferably used.

  Further, polynorbornene, which is a ring-opening polymer of norbornene, is a polymer having a glass transition point of about 35 ° C. having a double bond in the molecule, and is not itself rubbery, but an aromatic oil, A composition obtained by blending oils such as naphthenic oil and paraffinic oil has a glass transition point of about −60 ° C. and has properties of an elastic body. Various rubber modifiers, etc. However, in the present invention, it can be suitably used as a crosslinkable polymer, so it is included in the crosslinkable rubber.

  Examples of the polyolefin resin having a weight average molecular weight of less than 500,000 include polyolefin resins such as polyethylene and polypropylene, and modified polyolefin resins such as an ethylene-acrylic monomer copolymer and an ethylene-vinyl acetate copolymer. Examples of the thermoplastic elastomer include thermoplastic elastomers such as polystyrene, polyolefin, polydiene, vinyl chloride, and polyester. The lower limit of the weight average molecular weight of such a polyolefin resin having a weight average molecular weight of less than 500,000 is not particularly limited, but is usually about 20,000. These polyolefin resins and thermoplastic elastomers may be used alone or in combination of two or more. Among the thermoplastic elastomers, those having a double bond in the molecule can be used as the crosslinkable rubber.

  According to the present invention, polyolefin resins having a weight average molecular weight of less than 500,000 include, among these, polyethylene resins having a low melting point, polyolefin elastomers having crystallinity, and polymethacrylates having a low melting temperature. Is preferable in that it has a low shutdown temperature.

  According to the present invention, the base porous film comprises a polyolefin resin composition comprising a polyolefin resin having a weight average molecular weight of 500,000 or more and a crosslinkable rubber having a double bond in the molecular chain, as described above. What crosslinks the said crosslinkable rubber | gum is used suitably, but the ratio of the polyolefin resin whose weight average molecular weight is 500,000 or more in the said polyolefin resin composition is a porous obtained from this polyolefin resin composition here. In view of the strength of the quality film and the balance with other components, the range of 5 to 95% by weight in the polyolefin resin composition is preferable, and the range of 10 to 90% by weight is particularly preferable. On the other hand, in the polyolefin resin composition, the proportion of the crosslinkable rubber is 3% by weight or more, and particularly preferably in the range of 5 to 35% by weight.

  In the polyolefin resin composition, when the proportion of the crosslinkable rubber is less than 3% by weight, the resulting porous film may not be sufficiently improved in heat resistance even by crosslinking of the crosslinkable rubber.

  Furthermore, according to the present invention, the polyolefin resin composition for producing the porous film may contain a polyolefin resin having a weight average molecular weight of less than 500,000 or a thermoplastic elastomer, if necessary. In such a case, it is preferable that those ratios are in the range of 1 to 50% by weight in total amount in the polymer composition. By having such a component in the base porous film, the resulting porous film has a shutdown function at a lower temperature.

  Next, a porous material comprising a polyolefin resin composition comprising a polyolefin resin having a weight average molecular weight of at least 500,000 as described above and a crosslinkable rubber having a double bond in the molecular chain, and the crosslinkable rubber is crosslinked. The production of the film will be described. Such a porous film can be obtained by forming a film by an appropriate method such as a conventionally known dry film forming method or wet film forming method and then cross-linking the crosslinkable rubber in the film.

  That is, for example, the polyolefin resin composition is mixed with a solvent, kneaded and heated and dissolved to form a slurry-like kneaded product, which is then formed into a sheet using appropriate means, and the sheet is rolled. Furthermore, after a uniaxial or biaxial stretching is performed to obtain a film, a porous film can be obtained by extracting and removing the solvent from the film. Next, by utilizing the double bond of the crosslinkable rubber possessed by the porous film, the crosslinkable rubber can be crosslinked to give the porous film the required heat resistance.

  In the production of the porous film, examples of the solvent for obtaining the slurry-like kneaded product include aliphatic or alicyclic hydrocarbons such as nonane, decane, undecane, dodecane, decalin, liquid paraffin, and the boiling point. Mineral oil fractions corresponding to these solvents are used, and among these, non-volatile solvents containing a large amount of alicyclic hydrocarbons such as liquid paraffin are preferably used.

  The ratio of the polyolefin resin composition in the slurry kneaded material is preferably in the range of 5 to 30% by weight, more preferably in the range of 10 to 30% by weight, and most preferably in the range of 10 to 25% by weight. That is, the proportion of the polyolefin resin composition in the slurry-like kneaded material is preferably 5% by weight or more from the viewpoint of improving the strength of the obtained porous film, and on the other hand, a polyolefin resin having a weight average molecular weight of 500,000 or more is sufficient. It is preferably 30% by weight or less so that it can be dissolved in a solvent and kneaded to near the extended state, and sufficient entanglement of the polymer chain can be obtained. In addition, additives such as antioxidants, ultraviolet absorbers, dyes, nucleating agents, pigments, antistatic agents, and the like may be blended into the kneaded material as necessary, as long as the object of the present invention is not impaired. it can.

  In order to mix and knead the polyolefin resin composition and the solvent to obtain a slurry-like kneaded product and form this into a sheet, any conventionally known method can be used. For example, the polyolefin resin composition and the solvent are kneaded batch-wise using a Banbury mixer, a kneader, etc., and the resulting kneaded product is rolled between a pair of cooled rolls or a pair of cooled pairs. The sheet may be sandwiched between metal plates and cooled to form a sheet by rapid crystallization, or may be formed into a sheet using an extruder or the like equipped with a T die or the like. The kneading temperature is not particularly limited, but is preferably in the range of 100 to 200 ° C.

  The thickness of the sheet thus obtained is not particularly limited, but is usually preferably in the range of 3 to 20 mm. Further, the obtained sheet is rolled using a heat press or the like, and 0.5 to 3 mm. You may make it thickness. This rolling is usually preferably performed at a temperature of 100 to 140 ° C. In order to stretch the obtained sheet, although not particularly limited, a normal tenter method, roll method, inflation method or a combination of these methods may be used, and uniaxial stretching, Any method such as biaxial stretching can be employed. In the case of biaxial stretching, both longitudinal and transverse simultaneous stretching or sequential stretching may be used. It is preferable that the temperature of an extending | stretching process is the range of 100-140 degreeC.

  The solvent removal treatment is a treatment for removing the solvent from the sheet to form a porous structure, and can be performed, for example, by washing the sheet with a solvent and removing the remaining solvent. Solvents include hydrocarbons such as pentane, hexane, heptane and decane, chlorinated hydrocarbons such as methylene chloride and carbon tetrachloride, fluorinated hydrocarbons such as ethane trifluoride, ethers such as diethyl ether and dioxane, Easily volatile solvents such as alcohols such as methanol and ethanol, and ketones such as acetone and methyl ethyl ketone are used. These are used individually or in mixture of 2 or more types. The solvent removal treatment of the sheet using such a solvent is performed, for example, by immersing the sheet in the solvent or by showering the solvent on the sheet.

  According to the present invention, after obtaining a porous film from the polyolefin resin composition in this manner, it is preferable to perform a heat treatment in order to reduce its heat shrinkability. This heat treatment may be a single-stage heat treatment in which the porous film is heated once, or may be a multi-stage heat treatment in which the porous film is first heated at a relatively low temperature and then heated at a higher temperature. Moreover, the temperature rising type heat processing which heats a porous film, raising temperature may be sufficient. However, it is desirable that this heat treatment is performed so as not to impair desirable characteristics inherent in the porous film, such as air permeability.

  In the case of the above-mentioned one-stage heat treatment, the heating temperature is preferably in the range of 40 to 140 ° C., although it depends on the composition of the porous film. Moreover, according to the temperature rising type or multistage heat treatment that starts heating from a relatively low temperature and then increases the heating temperature, it can also serve as crosslinking of the crosslinkable rubber in the porous film, and heat resistance of the porous film Therefore, heat treatment can be performed without impairing desirable properties of the porous film such as air permeability by heating, and the required heat treatment can be performed in a short time. In particular, in the multi-stage heat treatment, the first heating temperature depends on the composition of the porous film, but is preferably in the range of 40 to 90 ° C., and the second heating temperature depends on the composition of the porous film. However, it is preferably in the range of 90 to 140 ° C.

  According to the present invention, the crosslinkable rubber in the porous film is cross-linked as described above in order to increase the heat resistance of the porous film obtained before or after the heat treatment step. By such crosslinking of the crosslinkable rubber, the heat resistance (fracture resistance) at a high temperature of the obtained porous film can be remarkably improved. As described above, it is also preferable from the viewpoint of productivity to crosslink the crosslinkable rubber in the porous film also serving as the heat treatment of the porous film, and thus also in the porous film serving as the heat treatment of the porous film. By crosslinking the crosslinkable rubber, the heat shrinkability of the porous film can be reduced, and at the same time, the heat resistance of the porous film can be remarkably improved.

  Here, in order to crosslink the crosslinkable rubber in the obtained porous film, the porous film is heated in the presence of oxygen, ozone, oxygen compound, etc., and the crosslinkable rubber is subjected to a crosslinking reaction. Among them, it is preferable to crosslink the crosslinkable rubber in the presence of oxygen. Therefore, for example, the porous film is heated in air or irradiated with ultraviolet rays or an electron beam. Further, if necessary, a conventionally known peroxide can be used in combination to promote the intended crosslinking reaction. Of course, if necessary, a plurality of crosslinking methods may be used in combination.

  In the present invention, the substrate porous membrane film functions as a separator after the production of the battery, so that the thickness is preferably in the range of 1 to 60 μm, and particularly preferably in the range of 5 to 50 μm. . When the film thickness is less than 1 μm, the strength is insufficient, and there is a possibility of causing an internal short circuit when used as a separator in a battery. On the other hand, when it exceeds 60 μm, the distance between the electrodes is too large, The internal resistance of the battery becomes excessive. The substrate porous film should have pores with an average pore diameter of 0.01 to 5 μm, and the porosity should be in the range of 20 to 80%, particularly in the range of 25 to 75%. It is good. Further, the base porous film should have an air permeability determined in accordance with JIS P 8117 in the range of 100 to 1000 seconds / 100 cc, and particularly preferably in the range of 100 to 900 seconds / 100 cc. .

  A reactive polymer-supported porous film for a battery separator according to the present invention comprises a crosslinkable polymer having at least one reactive group selected from a 3-oxetanyl group and an epoxy group in a molecule and a polycarboxylic acid. A reactive polymer obtained by reacting and partially cross-linking is supported on the base porous film as described above.

  Further, according to the present invention, the crosslinkable polymer refers to a polymer having at least one reactive group selected from a 3-oxetanyl group and an epoxy group in the molecule, preferably a radical having a 3-oxetanyl group. It is a radical copolymer of at least one radical polymerizable monomer selected from a polymerizable monomer and a radical polymerizable monomer having an epoxy group and another radical polymerizable monomer.

  Particularly preferably, in the present invention, the crosslinkable polymer refers to a polymer having a 3-oxetanyl group and an epoxy group in the molecule, or a polymer having an epoxy group in the molecule. Is preferably a radical copolymerization of a radical polymerizable monomer having a 3-oxetanyl group with a radical polymerizable monomer having an epoxy group and another radical polymerizable monomer, or a radical polymerizable monomer having an epoxy group and another radical polymerizable monomer. It can be obtained by radical copolymerization with a radical polymerizable monomer.

  As already known, 3-oxetanyl groups and epoxy groups can react with carboxyl groups and can be cationically polymerized. According to the present invention, a crosslinkable polymer having at least one reactive group selected from 3-oxetanyl group and epoxy group in the molecule by utilizing such reactivity of 3-oxetanyl group and epoxy group. First, the reactive polymer is reacted with a polycarboxylic acid by these reactive groups to form a partially crosslinked reactive polymer, which is supported on a porous substrate film, and is loaded with a reactive polymer for a battery separator. A porous film is used.

  Furthermore, according to the present invention, as will be described later, an electrode is laminated on such a reactive polymer-supported porous film to form an electrode / porous film laminate, which is an electrolytic solution containing a cationic polymerization catalyst, preferably Is immersed in an electrolytic solution containing an electrolyte that also serves as a cationic polymerization catalyst, and a partially crosslinked cross-linkable polymer on the porous film, that is, at least a part of the reactive polymer is swollen in the electrolytic solution, or By eluting and diffusing into the electrolyte, the reactive polymer is further cross-linked by cationic polymerization of the remaining reactive groups, and the electrolyte is gelled in the vicinity of the interface between the porous film and the electrode. Adhere the porous film.

  According to the present invention, when obtaining a crosslinkable polymer having at least one reactive group selected from a 3-oxetanyl group and an epoxy group in the molecule, a 3-oxetanyl group-containing radical polymerizable monomer and / or epoxy is obtained. The group-containing radical polymerizable monomer is used so that the total amount of the reactive groups is in the range of 5 to 50% by weight, preferably 10 to 30% by weight of the total monomer amount. Therefore, in the case of obtaining a crosslinkable polymer containing a 3-oxetanyl group, the 3-oxetanyl group-containing radical polymerizable monomer is in the range of 5 to 50% by weight, preferably 10 to 30% by weight of the total monomer amount. In the same manner, in the case of obtaining a crosslinkable polymer containing an epoxy group, the epoxy group-containing radical polymerizable monomer is 5 to 50% by weight, preferably 10 to 30% by weight of the total monomer amount. Used in a range.

  Also, a crosslinkability having both a 3-oxetanyl group and an epoxy group by using a 3-oxetanyl group-containing radical polymerizable monomer and an epoxy group-containing radical polymerizable monomer together and copolymerizing these with another radical polymerizable monomer Even in the case of obtaining a polymer, the total amount of the 3-oxetanyl group-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. Furthermore, among the 3-oxetanyl group-containing radical polymerizable monomer and the epoxy group-containing radical polymerizable monomer, the epoxy group-containing radical polymerizable monomer is used so as to be 90% by weight or less.

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

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

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

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

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

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

Or formula (2)

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

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

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

(In the formula, R ₅ represents a hydrogen atom or a methyl group, A represents an oxyalkylene group having 2 or 3 carbon atoms (preferably an oxyethylene group or an oxypropylene group), and R ₆ represents 1 to 1 carbon atoms. 6 represents an alkyl group 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,

Etc. In formula, n is an integer of 0-3.

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

  As described above, the crosslinkable polymer having at least one reactive group selected from a 3-oxetanyl group and an epoxy group in the molecule is preferably a radical polymerizable monomer having an 3-oxetanyl group and an epoxy group. It can be obtained as a radical copolymer by radically copolymerizing at least one radical polymerizable monomer selected from the radical polymerizable monomers having and another radical polymerizable monomer using a radical polymerization initiator. This radical copolymerization may be carried out by any polymerization method such as solution polymerization, bulk polymerization, suspension polymerization, emulsion polymerization, etc., but solution polymerization or suspension polymerization in terms of ease of polymerization, adjustment of molecular weight, post-treatment, etc. Is preferred.

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

  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.

  Crosslinkable polymers having at least one reactive group selected from a 3-oxetanyl group and an epoxy group in the molecule as described above are described in JP-A Nos. 2001-176555 and 2002-110245. As is already known.

  The reactive polymer-supported porous film for a battery separator according to the present invention is obtained by reacting a crosslinkable polymer as described above with a polycarboxylic acid, and partially crosslinking the substrate as a reactive polymer. It is carried on. Crosslinking of such a crosslinkable polymer with a polycarboxylic acid is, for example, as described in Japanese Patent Application Laid-Open No. 11-43540 and Japanese Patent Application Laid-Open No. 11-116663, and 3-oxetanyl group or epoxy which the crosslinkable polymer has And a polycarboxylic acid (that is, a carboxyl group). According to the present invention, by utilizing this reactivity of a 3-oxetanyl group or an epoxy group, a crosslinkable polymer is reacted with polycarboxyl and partially crosslinked to obtain a reactive polymer.

  In the present invention, the polycarboxylic acid for partially crosslinking the crosslinkable polymer has 2 or more carboxyl groups in the molecule, preferably 2 to 6 in the molecule, particularly preferably in the molecule. It is an organic compound having 2 to 4 carboxyl groups.

  Examples of the dicarboxylic acid having two carboxyl groups in the molecule include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid. C2-C20 straight chain aliphatic saturated dicarboxylic acid such as acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid, nonadecanedioic acid, eicosanedioic acid, methylmalonic acid, Branched aliphatic saturated dicarboxylic acids having 3 to 20 carbon atoms such as ethylmalonic acid, n-propylmalonic acid, n-butylmalonic acid, methylsuccinic acid, ethylsuccinic acid, 1,1,3,5-tetramethyloctylsuccinic acid Acid, maleic acid, fumaric acid, citraconic acid, γ-methylcitraconic acid, mesaconic acid, γ-methylmesaconic acid, Linear or branched aliphatic unsaturated dicarboxylic acids such as itaconic acid and glutaconic acid, hexahydrophthalic acid, hexahydroisophthalic acid, hexahydroterephthalic acid, methylhexahydroxyphthalic acid, methylhexaisophthalic acid, methylhexahydroterephthalic acid , Cyclohexene-1,2-dicarboxylic acid, cyclohexene-1,6-dicarboxylic acid, cyclohexene-3,4-dicarboxylic acid, cyclohexene-4,5-dicarboxylic acid, etc. tetrahydrophthalic acid, cyclohexene-1,3-dicarboxylic acid Tetrahydroisophthalic acid such as cyclohexene-1,5-dicarboxylic acid and cyclohexene-3,5-dicarboxylic acid, tetrahydroterephthalic acid such as cyclohexene-1,4-dicarboxylic acid and cyclohexene-3,6-dicarboxylic acid, 1,3 -Siku Hexadiene-1,2-dicarboxylic acid, 1,3-cyclohexadiene-1,6-dicarboxylic acid, 1,3-cyclohexadiene-2,3-dicarboxylic acid, 1,3-cyclohexadiene-5,6-dicarboxylic acid 1,4-cyclohexadiene-1,2-dicarboxylic acid, dihydrophthalic acid such as 1,4-cyclohexadiene-1,6-dicarboxylic acid, 1,3-cyclohexadiene-1,3-dicarboxylic acid, Dihydroisophthalic acid such as 3-cyclohexadiene-3,5-dicarboxylic acid, 1,3-cyclohexadiene-1,4-dicarboxylic acid, 1,3-cyclohexadiene-2,5-dicarboxylic acid, 1,4-cyclo Dihydroterephthalic acid such as hexadiene-1,4-dicarboxylic acid, 1,4-cyclohexadiene-3,6-dicarboxylic acid, methyl tet Hydrophthalic acid, endomethylenetetrahydrophthalic acid, endocis-bicyclo [2.2.1] hept-5-ene-2,3-dicarboxylic acid, methyl-endocis-bicyclo [2.2.1] hept-5-ene- Saturated or unsaturated carboxylic acid such as 2,3-dicarboxylic acid, chlorendic acid, phthalic acid, terephthalic acid, isophthalic acid, 3-methylphthalic acid, 3-ethylphthalic acid, 3-n-propylphthalic acid, 3-isopropyl 3-alkylphthalic acid such as phthalic acid, 3-n-butylphthalic acid, 3-isobutylphthalic acid, 3-s-butylphthalic acid, 3-t-butylphthalic acid, 2-methylphthalic acid, 4-ethylphthalic acid, 4-n -Propylphthalic acid, 4-isopropylpyrphthalic acid, 4-n-butylphthalic acid, 4-isobutylphthalic acid, 4-s-butylphthalic acid Acid, 4-alkylphthalic acid such as 4-t-butylphthalic acid, 2-methylisophthalic acid, 2-ethylisophthalic acid, 2-n-propylphthalic acid, 2-isopropylpropylphthalic acid, 2-n-butylphthalic acid 2-alkylphthalic acid such as 2-isobutylphthalic acid, 2-s-butylphthalic acid, 2-t-butylphthalic acid, 4-methylisophthalic acid, 4-ethylisophthalic acid, 4-n-propylisophthalic acid, 4- 4-alkylisophthalic acid such as isopropylpyrophthalic acid, 4-n-butylisophthalic acid, 4-isobutylisophthalic acid, 4-s-butylisophthalic acid, 4-t-butylisophthalic acid, 5-methylisophthalic acid, 5 -Ethylisophthalic acid, 5-n-propylisophthalic acid, 5-isopropyl-isophthalic acid, 5-n-butylisophthalic acid, 5-isobu 5-alkylisophthalic acid such as ruisophthalic acid, 5-s-butylisophthalic acid, 5-t-butylisophthalic acid, methyl terephthalic acid, ethyl terephthalic acid, n-propyl terephthalic acid, isopropyl terephthalic acid, n-butyl terephthalic acid Acid, isobutyl terephthalic acid, s-butyl terephthalic acid, alkyl terephthalic acid such as t-butyl terephthalic acid, naphthalene-1,2-dicarboxylic acid, naphthalene-1,3-dicarboxylic acid, naphthalene-1,4-dicarboxylic acid, Naphthalene-1,5-dicarboxylic acid, naphthalene-1,6-dicarboxylic acid, naphthalene-1,7-dicarboxylic acid, naphthalene-1,8-dicarboxylic acid, naphthalene-2,3-dicarboxylic acid, naphthalene-2,6 -Dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, anthracene 1,3-dicarboxylic acid, anthracene-1,4-dicarboxylic acid, anthracene-1,5-dicarboxylic acid, anthracene-1,9-dicarboxylic acid, anthracene-2,3-dicarboxylic acid, anthracene-9,10-dicarboxylic acid Specific examples include aromatic dicarboxylic acids such as acids, 2,2′-bis (carboxychiphenyl) hexafluoropropane, and the like.

  Examples of the polycarboxylic acid having three or more carboxyl groups in the molecule include aliphatic tricarboxylic acids such as tricarballylic acid, citric acid, isocitric acid and aconitic acid, aromatic tricarboxylic acids such as hemimellitic acid and trimellitic acid, C4-C13 aliphatic tetracarboxylic acid such as 2,3,4-butanetetracarboxylic acid, alicyclic tetracarboxylic acid such as maleated methylcyclohexene tetracarboxylic acid, merophanic acid, planitic acid, pyromellitic acid, Specific examples include aromatic tetracarboxylic acids such as benzophenone tetracarboxylic acid, hexahydromellitic acid, benzenepentacarboxylic acid, and mellitic acid.

  In the present invention, a polyol ester of a polycarboxylic acid and a polyol as described above, preferably a diol ester of a dicarboxylic acid and a diol, particularly a (poly) alkylene glycol or polymethylene diol, is also used as the polycarboxylic acid. be able to. Examples of such diol esters include ethylene glycol didipate.

  Furthermore, in the present invention, the polycarboxylic acid may be a polymer carboxylic acid having a plurality of carboxyl groups in the molecule. Examples of such a polymer carboxylic acid include a copolymer of (meth) acrylic acid and (meth) acrylic acid ester.

  The reactive polymer-supported porous film for a battery separator according to the present invention is obtained by reacting the crosslinkable polymer with the polycarboxylic acid as described above, and partially crosslinking it to form a reactive polymer, which is porous. It is carried on a film. Thus, in order to carry the reactive polymer on the porous film, it is not particularly limited. For example, the crosslinkable polymer is mixed with a polycarboxylic acid in an appropriate solvent such as acetone, ethyl acetate, or butyl acetate. Dissolve and apply this solution to the substrate porous film by casting, spray coating, etc. and impregnate it, and then dry it to remove the solvent used. A porous film carrying a polymer and a polycarboxylic acid is heated to an appropriate temperature to cause the crosslinkable polymer to react with the polycarboxylic acid, and partially crosslink the crosslinkable polymer as described above. In this way, a reactive polymer-supported porous film for a battery separator according to the present invention is obtained.

  According to the present invention, if necessary, an onium salt may be supported on the porous film as a catalyst together with the crosslinkable polymer and the polycarboxylic acid. As such an onium salt, those described later can be used.

  In the present invention, the means and method for supporting the reactive polymer obtained by partially crosslinking the crosslinkable polymer with the polycarboxylic acid on the substrate porous film are not limited to the above examples. The solution may be applied to a porous film and dried, and then the polycarboxylic acid solution may be applied to and impregnated into such a porous film, dried, and then heated to an appropriate temperature. Moreover, after apply | coating the solution containing a crosslinkable polymer and polycarboxylic acid to a peelable sheet, drying and transferring this to a base material porous film, you may heat to appropriate temperature.

  According to the present invention, the reactive polymer obtained by partially crosslinking the crosslinkable polymer in this way has a gel fraction in the range of 1 to 90%, preferably in the range of 3 to 60%. It is desirable to have. Here, the gel fraction is, as will be described later, a porous film carrying a partially crosslinked reactive polymer immersed in toluene at a temperature of 23 ° C. for 7 days, dried, and then the porous film. The ratio of the reactive polymer remaining on the top.

  Thus, to obtain a reactive polymer having a gel fraction in the range of 1 to 90% by reacting a crosslinkable polymer with a polycarboxylic acid and partially crosslinking the polymer, is not limited. Usually, the carboxyl group of the polycarboxylic acid is 0.01 to 1.0 mole part, preferably 0.05 to 0.8 mole part, particularly preferably 1 mole part of the reactive group of the crosslinkable polymer. May be used in an amount of 0.1 to 0.7 mol, and the heating reaction conditions between the crosslinkable polymer and the polycarboxylic acid may be adjusted, and in this way, the reactivity having a desired gel fraction is obtained. A polymer can be obtained.

  The heating reaction condition between the crosslinkable polymer and the polycarboxylic acid depends on the desired gel fraction, but the heating temperature is usually in the range of 30 to 100 ° C., preferably 40 to 80 ° C., and the heating time is It ranges from 10 minutes to 100 hours, preferably from 1 hour to 60 hours.

  As an example, while using so that the carboxyl group which polycarboxylic acid has may be 0.5-1.0 mol part with respect to 1 mol part of reactive groups which a crosslinkable polymer has, crosslinkable polymer, polycarboxylic acid, Can be reacted at 50 ° C. for 12 to 180 hours to obtain a reactive polymer having a gel fraction of 3 to 80%.

  When the gel fraction of the reactive polymer is less than 1%, as will be described later, an electrode is pressure-bonded to a porous film carrying such a reactive polymer to form an electrode / porous film laminate, When this is immersed in the electrolytic solution, most of the reactive polymer is eluted and diffused in the electrolytic solution, and even if the reactive polymer is further cationically polymerized and crosslinked, it is effective between the electrode and the porous film. Adhesion cannot be obtained. On the other hand, when the gel fraction of the reactive polymer is more than 90%, an electrode / porous film laminate is formed, and when this is immersed in an electrolyte solution, the swelling property of the reactive polymer is low, and the resulting electrode / porous A battery having a quality film assembly has a high internal resistance, which is not preferable for battery characteristics. In particular, according to the present invention, the gel fraction of the reactive polymer is preferably in the range of 1 to 90%, preferably in the range of 3 to 60%, most preferably, as described above. It is 5 to 50% of range.

  Thus, according to the present invention, the reactive polymer having the gel fraction obtained by reacting a cross-linkable polymer with a polycarboxylic acid and reacting and cross-linking a part thereof is immersed in an electrolytic solution. In addition, elution and diffusion into the electrolyte are suppressed. Accordingly, such a reactive polymer is supported on a porous film, and an electrode is laminated on the porous film to form an electrode / porous film laminate, which is charged into the battery container, and then the cationic polymerization catalyst is placed in the battery container. When an electrolyte containing an electrolyte containing is injected, only a part of the reactive polymer in the electrode / porous film laminate is swollen in the electrolyte near the interface between the porous film and the electrode, or Due to the remaining reactive groups that were eluted in the electrolyte and not used for the partial cross-linking with the polycarboxylic acid described above, the reactive polymer is a cationic polymerization catalyst in the electrolyte, preferably an electrolyte that also serves as the cationic polymerization catalyst. Cationic polymerization, further cross-linking, gelling the electrolyte solution, and firmly bonding the electrode to the porous film with good adhesion, thus the electrode / porous film (ie, obtained) It is possible to obtain a separator) conjugate in batteries.

  That is, according to the present invention, the partially cross-linked reactive polymer has a gel fraction in the above range, and therefore, even when immersed in the electrolytic solution, elution and diffusion into the electrolytic solution are prevented, Or it can be reduced and effectively used for adhesion between the electrode and the porous film, so that the electrode and the porous film can be bonded stably and more firmly by using a relatively small amount of the reactive polymer. Can do.

  As described above, the reactive polymer-supported porous film according to the present invention can be suitably used for battery production. That is, after being incorporated in the battery, it functions as a separator. According to the present invention, this porous film (ie, separator) has a small area heat shrinkage even at high temperatures, and is usually 25% or less. Yes, preferably 20% or less. Below, the manufacturing method of the battery by this invention using such a reactive polymer carrying | support porous film is demonstrated.

  First, an electrode is laminated or wound on the reactive polymer-supported porous film to obtain an electrode / reactive polymer-supported porous film laminate, and then this laminate is a battery made of a metal can, a laminate film, or the like. In the case where it is necessary to weld the terminal and weld the terminal, etc., this is performed, and then a predetermined amount of an electrolytic solution in which the cationic polymerization catalyst is dissolved is injected into the battery container, and the battery container is sealed and sealed, At least a part of the reactive polymer supported on the reactive 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. Then, it is crosslinked by cationic polymerization, at least a part of the electrolyte is gelled, and the electrode is adhered to the porous film. Thus, the porous film is used as a separator. Electrode can be obtained strongly adhered battery.

  In the present invention, the reactive polymer bonds the electrode and the porous film by cross-linking the reactive group by cationic polymerization to gel the electrolyte at least in the vicinity of the interface between the porous film and the electrode. To function.

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

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

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

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

  In particular, when obtaining a lithium ion secondary battery according to the present invention, as the electrolyte salt, for example, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate 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, Cyclic esters such as butylene carbonate, γ-butyrolactone, terephthalates such as tetrahydrofuran and dimethoxyethane, and chain esters such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate alone or in combination of two or more It can be used as a mixture.
The electrolyte salt is appropriately determined according to the type and amount of the solvent to be used, but is usually used in an amount of 1 to 50% by weight in the obtained gel electrolyte.

  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 / stivonium 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 cation polymerization catalyst, and thus are preferable as the electrolyte salt. 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

(Reaction polymer gel fraction)
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 toluene at a temperature of 23 ° C. for 7 days and then dried. The reactive polymer-supported porous film thus treated was weighed and its weight C was measured. The gel fraction of the reactive polymer is

I asked for it.

(Measurement of heat-resistant temperature of porous film by needle-insertion probe type thermomechanical analyzer)
A 5 mm square porous film sample was placed on a sample stage of a needle-inserted probe thermomechanical analyzer (EXSTAR6000 manufactured by Seiko Denshi Co., Ltd.), and a needle-inserted probe with a 1 mm diameter tip was placed on this sample. A load of 70 gf was applied on the probe, the sample was heated from room temperature at a rate of 2 ° C./min, and the change in the thickness of the sample was measured. The temperature when the thickness of the sample was ½ of the thickness (initial thickness) of the sample when a load was applied to the sample was defined as the heat resistant temperature of the sample.

Reference example 1
(Preparation of electrode sheet)
It is 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 agent 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. This slurry was applied onto an aluminum foil (current collector) having a thickness of 20 μm, applied to a thickness of 200 μm, vacuum-dried at 80 ° C. for 1 hour, and then at 120 ° C. for 2 hours, and then pressurized with a roll press to activate the slurry. A positive electrode sheet having a material layer 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.

(Discharge characteristics of batteries according to examples or comparative examples)
The coin-type battery obtained in the following examples or comparative examples is subjected to a charge / discharge test three times at a rate of 0.2 CmA, and the third discharge capacity of this test is set to a discharge capacity at 0.2 CmA, Next, after charging at 0.2 CmA, discharging was performed at a rate of 1 CmA, and the discharge capacity at this time was defined as the discharge capacity at 1 CmA. From these values, the discharge capacity retention ratio = 1 discharge capacity at 1 CmA / discharge capacity at 0.2 CmA was calculated, and the battery characteristics were evaluated based on this value.

(Measurement of thermal shrinkage of separator (porous film))
It is composed of a mixed solvent of ethylene carbonate / diethyl carbonate (weight ratio 1/1) in which lithium hexafluorophosphate is dissolved at a concentration of 1.2 mol / L in the positive electrode / porous film / negative electrode laminate punched out to a predetermined size. After impregnating the electrolytic solution, sandwiched between glass plates, and further wrapped in a fluororesin sheet to suppress the volatilization of the electrolytic solution, put a weight of 100 g on it, placed in a constant temperature room at a temperature of 50 ° C. for 24 hours The reactive polymer carried on the porous film of the positive electrode / porous film / negative electrode laminate is cationically polymerized and crosslinked to bond the positive and negative electrodes to the porous film (that is, the separator in the battery). Thus, a positive electrode / porous film / negative electrode assembly was obtained. Next, the positive electrode / porous film / negative electrode assembly was sandwiched between glass plates and placed in a dryer at 200 ° C. for 1 hour.

  After this, the glass plate is removed from the positive electrode / porous film / negative electrode assembly treated in this way, the separator is peeled off from the positive and negative electrodes, read with a scanner, and compared with the area of the porous film used first, The area heat shrinkage rate was determined.

Production Example 1
(Production of crosslinkable polymer A (3,4-epoxycyclohexylmethyl (meth) acrylate monomer component 5 wt%, 3-oxetanyl group-containing monomer component 20 wt%, methyl methacrylate monomer component 75 wt%))
In a 500 mL three-necked flask equipped with a reflux condenser, 60.0 g of methyl methacrylate, 16.0 g of 3-ethyl-3-oxetanylmethyl methacrylate, 4.0 g of 3,4-epoxycyclohexylmethyl acrylate, 226.6 g of ethylene carbonate Then, 0.15 g of N, N′-azobisisobutyronitrile was charged, and the mixture was stirred and mixed for 30 minutes while introducing nitrogen gas, and then heated to 70 ° C. to carry out radical polymerization for 8 hours. After this, the resulting reaction mixture was cooled to 40 ° C. To this reaction mixture, 226.6 g of diethyl carbonate and 0.15 g of N, N′-azobisisobutyronitrile were added, and the mixture was heated again to 70 ° C., and radical polymerization was further performed for 8 hours. Thereafter, the obtained reaction mixture was cooled to 40 ° C. to obtain a mixed solvent solution of the crosslinkable polymer A in ethylene carbonate / diethyl carbonate (concentration: 15% by weight).

  Next, 100 g of this polymer solution was added to 600 mL methanol while stirring with a high-speed mixer to precipitate the polymer. The polymer was filtered off, washed several times with methanol, put in a drying tube, dried by circulating dry nitrogen gas (dew point temperature of −150 ° C. or lower) in which liquid nitrogen was vaporized, A crosslinkable polymer A was obtained by vacuum drying in a desiccator for 6 hours. The crosslinkable polymer A thus obtained was a pure white powder. As a result of molecular weight measurement by GPC, the weight average molecular weight was 344400 and the number average molecular weight was 174500.

Example 1
(Preparation of porous film A)
Norbornene ring-opening polymer powder (Norex NB manufactured by Nippon Zeon Co., Ltd., weight average molecular weight 2 million or more) 8% by weight, thermoplastic elastomer (TPE824 manufactured by Sumitomo Chemical Co., Ltd.) 12% by weight, and weight average molecular weight 16 parts by weight of polyethylene resin composition consisting of 80% by weight of 3.5 million ultra high molecular weight polyethylene resin and 84 parts by weight of liquid paraffin are mixed in a slurry and dissolved at a temperature of 160 ° C. for about 1 hour using a small kneader. Kneaded. Thereafter, the obtained kneaded material was sandwiched between metal plates cooled to 0 ° C. and rolled into a sheet while rapidly cooling. Next, this sheet was heat-pressed at a temperature of 115 ° C. until the thickness became 0.5 mm, and further, biaxially stretched 4.5 × 4.5 times in length and width at the same temperature, and then heptane was used. The solvent was removed. The porous film thus obtained was heated in air at 85 ° C. for 6 hours, then heated at 118 ° C. for 1.5 hours to heat-treat the porous film, and crosslinkability in the porous film. The intended porous film A was obtained by crosslinking the rubber. This porous film had a thickness of 25 μm and a porosity of 50%, and as described above, the heat-resistant temperature was 370 ° C. when examined using a needle-inserted probe thermomechanical analyzer.

  10 g of the crosslinkable polymer A was added to 90 g of ethyl acetate and stirred at room temperature to obtain a uniform crosslinkable polymer solution. Separately, an ethanolic solution of adipic acid having a concentration of 10% by weight was prepared. While stirring the solution of the crosslinkable polymer A, the adipic acid solution was slowly added dropwise thereto to prepare a mixed solution of the crosslinkable polymer A and adipic acid. The ratio of the number of moles of carboxyl groups of adipic acid to the number of moles of reactive groups possessed by the crosslinkable polymer was 0.5.

After coating the mixed solution of the crosslinkable polymer A and adipic acid on both surfaces of the porous film A with a wire bar (# 7), the mixture is heated at 60 ° C. to volatilize ethyl acetate and ethanol, thus A crosslinkable polymer-supported porous film obtained by supporting a crosslinkable polymer at a coating density of 2.2 g / m ² per side was obtained. Next, the crosslinkable polymer-supported porous film is put into a thermostat at 50 ° C. for 96 hours, the crosslinkable polymer supported on the porous film is reacted with adipic acid, and a part of the crosslinkable polymer is crosslinked. Thus, a reactive polymer-supported porous film was obtained. In this reactive polymer-supported porous film, the gel fraction of the reactive polymer was 55%.

  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 are laminated in this order to form a separator / electrode laminate, which also serves as a positive and negative electrode plate. After charging into a 2016 size coin-type battery can and injecting 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 1.2 mol / L The battery can was sealed. Thereafter, the reactive polymer is heated at 50 ° C. for 24 hours, and the reactive polymer is cationically polymerized, crosslinked, and the electrode sheet is adhered to the porous film (separator), and the electrolytic solution is partially gelled, A coin-type battery was obtained.

  The discharge capacity retention rate of this battery was 96%, and the area heat shrinkage rate of the separator was 14%. Furthermore, when this battery was disassembled and the adhesive force between the electrode sheet and the separator was measured, it was 0.31 N / cm for the positive electrode and 0.19 N / cm for the negative electrode.

Example 2
(Preparation of porous film B)
A polyethylene resin composition comprising 6% by weight of norbornene ring-opening polymer powder (Norsolex NB manufactured by Nippon Zeon Co., Ltd., weight average molecular weight of 2 million or more) and 94% by weight of ultrahigh molecular weight polyethylene resin having a weight average molecular weight of 3 million. 20 parts by weight and 80 parts by weight of liquid paraffin were mixed in a slurry, and dissolved and kneaded at a temperature of 160 ° C. for about 1 hour using a small kneader. Thereafter, the obtained kneaded material was sandwiched between metal plates cooled to 0 ° C. and rolled into a sheet while rapidly cooling. Next, this sheet was heat-pressed at a temperature of 117 ° C. until the thickness became 0.5 mm, and further, biaxially stretched 3.8 × 3.8 times at the same temperature, and then heptane was used. The solvent was removed. The porous film thus obtained was heated in air at 85 ° C. for 6 hours, then heated at 125 ° C. for 2 hours to heat-treat the porous film, and the crosslinkable rubber in the porous film was removed. The target porous film B was obtained by crosslinking. This porous film has pores with a thickness of 23 μm, a porosity of 45%, and an average pore diameter of 0.07 μm. As described above, when examined using a probe-in-probe thermomechanical analyzer, The temperature was 430 ° C.

(Evaluation of battery characteristics and measurement of separator area heat shrinkage)
In Example 1, a porous film carrying a reactive polymer having a gel fraction of 55% was obtained in the same manner as in Example 1 except that the porous film B was used instead of the porous film A. . Using this porous polymer B carrying the reactive polymer, a negative electrode / separator / positive electrode laminate was obtained in the same manner as in Example 1, and using this, a coin-type lithium was obtained in the same manner as in Example 1. An ion secondary battery was assembled. The discharge capacity retention rate of this battery was 94%, and the thermal shrinkage rate of the separator was 18%. Furthermore, when this battery was disassembled and the adhesive force between the electrode sheet and the separator was measured, it was 0.29 N / cm for the positive electrode and 0.20 N / cm for the negative electrode.

Example 3
(Preparation of porous film C)
15 parts by weight of a polyethylene resin composition comprising 20% by weight of EPDM (Esprene 512F manufactured by Sumitomo Chemical Co., Ltd., 4% by weight of ethylidene norbornene) and 80% by weight of ultrahigh molecular weight polyethylene resin having a weight average molecular weight of 1,500,000 and 85 liquid paraffins The parts by weight were uniformly mixed in a slurry state, and dissolved and kneaded at a temperature of 160 ° C. for about 1 hour using a small kneader. Thereafter, the obtained kneaded material was sandwiched between metal plates cooled to 0 ° C. and rolled into a sheet while rapidly cooling. Next, the sheet was heat-pressed at a temperature of 115 ° C. until the thickness became 0.4 mm, and further, biaxially stretched 4.0 × 4.0 times in length and width at a temperature of 123 ° C., and then heptane was used. The solvent was removed. The porous film thus obtained was heated in air at 85 ° C. for 6 hours, then heated at 116 ° C. for 1.5 hours to heat-treat the porous film, and the crosslinkability in the porous film. by crosslinking the rubber, to obtain a porous film C of interest. This porous film C has pores having a thickness of 24 μm, a porosity of 42%, and an average pore diameter of 0.08 μm. As described above, when examined using a probe-in-probe thermomechanical analyzer, The heat resistant temperature was 320 ° C.

(Evaluation of battery characteristics and measurement of separator area heat shrinkage)
In Example 1, a porous film carrying a reactive polymer having a gel fraction of 55% was obtained in the same manner as in Example 1 except that the porous film C was used in place of the porous film A. . Using the porous film carrying the reactive polymer, a negative electrode / separator / positive electrode laminate was obtained in the same manner as in Example 1, and a coin-type battery was prepared in the same manner as in Example 1 using this. Assembled. The discharge capacity retention rate of this battery was 95%, and the thermal shrinkage rate of the separator was 12%. Furthermore, when this battery was disassembled and the adhesive force between the electrode sheet and the separator was measured, it was 0.29 N / cm for the positive electrode and 0.19 N / cm for the negative electrode.

Comparative Example 1
A coin-type battery was assembled in the same manner as in Example 1 using the same porous film A as in Example 1 without supporting the reactive polymer. The evaluation of the discharge capacity retention rate of this battery was 97%, and the thermal shrinkage rate of the separator was 72%.

Comparative Example 2
(Preparation of porous film D)
15 parts by weight of a polyethylene resin composition consisting of 60% by weight of a polyethylene resin having a weight average molecular weight of 200,000 and 40% by weight of an ultrahigh molecular weight polyethylene resin having a weight average molecular weight of 1,500,000 and 85 parts by weight of liquid paraffin are mixed in a slurry form. Using a kneader, the mixture was dissolved and kneaded at a temperature of 160 ° C. for about 1 hour. Thereafter, the obtained kneaded material was sandwiched between metal plates cooled to 0 ° C. and rolled into a sheet while rapidly cooling. Next, this sheet was heat-pressed at a temperature of 115 ° C. until the thickness became 0.5 mm, and further, biaxially stretched 4.0 times and 4.0 times in length and width at the same temperature, and then heptane was used. The solvent was removed. The porous film thus obtained was heated in air at 85 ° C. for 6 hours, and then heated at 116 ° C. for 1 hour to obtain the intended porous film D. This porous film D has pores with a thickness of 24 μm, a porosity of 39%, and an average pore diameter of 0.1 μm. As described above, when examined using a probe-type thermomechanical analyzer, The heat resistant temperature was 160 ° C.

(Evaluation of battery characteristics and measurement of separator area heat shrinkage)
A reactive polymer-supported porous film having a gel fraction of 55 % was obtained in the same manner as in Example 1 except that the porous film D was used in place of the porous film A. Using this reactive polymer-supported porous film, a coin-type battery was obtained in the same manner as in Example 1. With respect to this battery, the discharge capacity retention rate was evaluated in the same manner as in Example 1, and it was 94%. Moreover, although it was going to measure the area heat shrinkage rate of the separator in this battery, the separator broke and the area heat shrinkage rate could not be measured. Furthermore, 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 0.21 N / cm for the negative electrode.

Claims (5)

  Using a probed thermomechanical analyzer, a probe with a diameter of 1 mm was placed on a porous film under a load of 70 g, and the porous film was heated from room temperature at a heating rate of 2 ° C./min. The thickness was measured, and at that time, the porous film having a temperature of 200 ° C. or higher when the thickness of the porous film was ½ of the thickness when the probe was placed was used as the substrate porous film, A reactive polymer obtained by reacting a cross-linkable polymer having at least one reactive group selected from 3-oxetanyl group and epoxy group in the molecule with a polycarboxylic acid and partially cross-linking the above-mentioned porous substrate A reactive polymer-supported porous film for a battery separator, wherein the porous film is supported on a porous film.   The substrate porous film comprises a polyolefin resin composition of a polyolefin resin having a weight average molecular weight of at least 500,000 and a crosslinkable rubber having a double bond in the molecular chain, and is formed by crosslinking the crosslinkable rubber. The porous polymer-supported porous film according to claim 1.   The crosslinkable polymer is a radical copolymer of at least one radical polymerizable monomer selected from a radical polymerizable monomer having a 3-oxetanyl group and a radical polymerizable monomer having an epoxy group and another radical polymerizable monomer. The reactive polymer-supported porous film according to claim 1.   A cross-linkable polymer having at least one reactive group selected from a 3-oxetanyl group and an epoxy group in the molecule and a polycarboxylic acid are supported on the base porous film, and a part of the reactive group is made of poly Reactivity for battery separator according to claim 1, characterized by reacting with a carboxylic acid to partially crosslink the reactive polymer, thus forming a reactive polymer on the substrate porous film. A method for producing a polymer-supporting porous film. 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 charging the body into the battery container, an electrolytic solution containing a cationic polymerization catalyst is injected into the battery container, and at least a part of the reactive polymer is removed in the vicinity of the interface between the porous film and the electrode. A method for producing a battery, comprising swelling in an electrolytic solution or eluting into the electrolytic solution, cationic polymerization, gelling at least a part of the electrolytic solution, and bonding the porous film and the electrode.