JP4537736B2 - battery - Google Patents

Description

  The present invention relates to a battery having high safety even at high temperatures, and more specifically, since a separator made of a porous film adheres firmly to an electrode and does not thermally shrink in a high temperature environment, thus, high safety at high temperatures. The present invention relates to a battery having

  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).

  Problems with the battery obtained in this way are that if the battery is left in an abnormally high temperature environment, overcharged, or if a short circuit occurs between electrodes inside or outside the battery, Generated abnormally, and the rapid rise in temperature caused the electrolyte inside the battery to be ejected outside the battery, possibly resulting in destruction.

  Conventionally, a porous film for a battery separator is produced, for example, by a method of stretching a molded resin sheet at a high magnification. Therefore, a battery separator made of such a porous film, for example, contracts significantly in a high temperature environment where the battery is abnormally heated due to an internal short circuit, and in some cases, the separator itself melts and breaks, There is a problem that it does not function as a partition between electrodes. Thus, 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 (see Patent Document 3).

In this regard, in order to suppress thermal shrinkage of the battery separator in a high temperature environment, a method of manufacturing a porous film by a method that does not include a stretching process in the manufacturing process has been proposed. However, since this method does not include a stretching treatment, there is a problem that the resulting film does not have sufficient strength (see Patent Document 4).
JP 09-161814 A JP 11-329439 A JP 09-12756 A Japanese Patent Laid-Open No. 05-310989

  The present invention has been made in order to solve the above-described problems in the conventional battery. When the battery is placed in a high temperature environment, the separator is firmly bonded to the electrode, and (almost) ) It is an object to provide a battery which does not shrink by heat and thus has excellent safety in a high temperature environment.

  According to the present invention, the glass transition temperature is in the range of 0 to 100 ° C., and the reactive polymer having a functional group capable of reacting with an isocyanate group under heating is supported on the porous film, and the porous film is sandwiched between the porous films. In this battery, a positive electrode and a negative electrode are stacked in contact with each other to form an electrode / porous film laminate, and this electrode / porous film laminate is charged into a battery container together with an electrolyte containing polyfunctional isocyanate. Thus, there is provided a battery characterized in that the adhesive force by the reactive polymer between the porous film and the electrode is 0.05 N / 10 mm or less at room temperature in the presence of the electrolytic solution.

  In the battery of the present invention, the reactive polymer supported on the separator (porous film) has little effect on the battery characteristics at room temperature, but is reactive when the battery is placed in a high temperature environment. The polymer reacts with the polyfunctional isocyanate in the electrolytic solution, crosslinks, the separator adheres firmly to the electrode, and the separator does not shrink (almost), so that the safety of the battery is maintained.

  In the present invention, the porous film is made of an appropriate resin, for example, a polyolefin resin such as polyethylene, polypropylene, and polybutylene, a so-called thermoplastic elastomer, nylon, cellulose acetate, polyacrylonitrile, polynorbornene, and the like. Can be obtained by a method such as a dry film forming method or a wet film forming method, as already known. For example, it can be obtained by mixing the resin with a solvent, heating, melting and kneading into a sheet, then rolling and stretching, and then extracting and removing the solvent used. If necessary, the resin can contain a cross-linkable rubber to form a porous film as described above, and then cross-linked with heat, ultraviolet light, electron beam or the like to impart heat resistance.

  In the present invention, a reactive polymer having a glass transition temperature in the range of 0 to 100 ° C. and having non-adhesive properties at room temperature (25 ° C.) and capable of reacting with an isocyanate group under heating is porous. The film is supported on a film to form a reactive polymer-supported porous film. Here, the reactive polymer is non-adhesive at room temperature, as described later, this reactive polymer is supported on a porous film, and the porous film is sandwiched between and in contact with the positive electrode and the negative electrode. Are stacked to form an electrode / porous film laminate, and the adhesive force between the porous film and the electrode in this laminate is measured in the presence of an electrolyte containing polyfunctional isocyanate, for example, When this adhesive solution is impregnated and the adhesive force between the porous film and the electrode is measured, it means that the adhesive force is 0.05 N / 10 mm or less.

  According to the present invention, when the reactive polymer is thus supported on the porous film, the reactive polymer is partially supported within a range of 5 to 95% of the surface area of the surface of the porous film on which the reactive polymer is supported. In particular, it is preferably supported in the range of 10 to 80%.

  In the present invention, the reactive polymer has a glass transition temperature in the range of 0 to 100 ° C., preferably 30 to 80 ° C., and is non-adhesive at normal temperature. A polymer having a functional group capable of reacting with a group. Examples of the functional group include a carboxyl group and a hydroxyl group.

  The reactive polymer can be usually obtained by copolymerizing a polymerizable monomer having the functional group with a polymerizable monomer having no such functional group, preferably by radical copolymerization. Examples of the polymerizable monomer having a carboxyl group as the functional group include (meth) acrylic acid, itaconic acid, maleic acid and the like. Moreover, as a polymerizable monomer which has a hydroxyl group as said functional group, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate etc. can be mentioned, for example. . On the other hand, as a monomer which does not have the said functional group, (meth) acrylic acid ester can be mentioned as a preferable specific example, for example.

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

  In particular, in the present invention, the reactive polymer includes, as an example, 0.1 to 20% by weight of a monomer component having a functional group capable of reacting with an isocyanate group as described above, and the (meth) acrylic acid ester as necessary. Depending on the monomer, for example, a copolymerizable monomer component having a nitrile group, preferably obtained by copolymerization with a vinyl monomer such as (meth) acrylonitrile, styrene, α-methylstyrene or vinyl acetate. Can do.

  In particular, in the present invention, a reactive polymer having a copolymerizable monomer component having a nitrile group, preferably a (meth) acrylonitrile component up to 80% by weight, preferably in the range of 5 to 70% by weight, This is an example of a preferred reactive polymer because of its excellent properties and solvent resistance.

  However, in the present invention, the reactive polymer is not limited to the above examples, and is a polymer having a functional group capable of reacting with an isocyanate group, for example, a functional group such as a carboxyl group or a hydroxyl group as described above. For example, a polyolefin polymer, a rubber polymer, a polyester polymer or the like having such a functional group can also be used.

  The reactive polymer as described above can be obtained as a polymer solution by copolymerizing the above-described monomers in a solvent such as benzene, toluene, xylene, ethyl acetate and butyl acetate. On the other hand, by emulsion polymerization, an aqueous dispersion of a reactive polymer can be obtained. Thus, after the polymer is separated and dried from this, it is dissolved in a solvent as described above and used as a polymer solution. In addition, when using the emulsion method, in addition to the above-described monomers, a polyfunctional crosslinking monomer such as divinylbenzene or trimethylolpropane triacrylate may be used in a proportion of 1% by weight or less of the total monomer amount.

  In order to obtain a reactive polymer-supported porous film by supporting the reactive polymer as described above on a porous film, for example, the reactive polymer may be applied directly on the porous film and dried. Moreover, after apply | coating to an appropriate peelable sheet and making it dry, you may transfer on a porous film. In addition, in order to improve the coating properties of reactive polymers on porous films, organic solvents such as methyl ethyl ketone and methyl isobutyl ketone, and inorganic fine powders such as heavy calcium carbonate and silica sand fine powder are fluid. You may mix | blend with a reactive polymer in the ratio of 50 weight% or less as a modifier.

  Furthermore, according to the present invention, when the reactive polymer is supported on the porous film, it is preferably supported partially as described above, specifically, for example, linear, speckled, lattice-shaped, for example. It is preferable to partially carry it in a stripe shape, a turtle shell pattern shape, or the like. In particular, according to the present invention, it is preferable to support the reactive polymer in the range of 5 to 95% of the surface area of the porous film to which the reactive polymer is applied.

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

  According to the present invention, in this way, the reactive polymer is supported on both the front and back sides or one side of the porous film, and the electrodes, that is, the negative electrode and the positive electrode are stacked so as to be in contact with each other. Used as an electrode / porous film laminate. Of course, it can also be set as the laminated body which has the structure of a positive (negative) pole / porous film / negative (positive) pole / porous film. If necessary, the electrode may be brought into contact with the reactive polymer-supported porous film so as to be laminated.

  The battery according to the present invention can be obtained by charging the electrode / porous film laminate into a battery container, and then injecting an electrolyte containing polyfunctional isocyanate into the battery container and sealing the battery. That is, the battery according to the present invention has an electrolytic solution containing the electrode / porous film laminate and the polyfunctional isocyanate in a battery container, and according to the present invention, at room temperature (25 ° C.). The adhesive force between the electrode in the presence of the electrolytic solution and the porous film is 0.05 N / 10 mm or less, and the electrode / porous film laminate is heated at 150 ° C. for 1 hour in the presence of the electrolytic solution. The area shrinkage ratio of the porous film is 20% or less.

  According to such a battery, since the reactive polymer supported on the porous film is non-adhesive at room temperature (25 ° C.), the porous film functioning as a separator is in contact with the electrode. However, since there is almost no adhesion between the porous film and the electrode, and therefore the reactive polymer is not resistant to the battery reaction, the battery is similar to not carrying the reactive polymer on the separator. It has the characteristic of. However, in a high temperature environment where the battery is abnormally heated due to an internal short circuit or the like and has a temperature of 100 ° C. or higher, the organic solvent forming the electrolytic solution partially volatilizes and pressure is generated inside the battery. The separator is brought into intimate contact with the electrode, and at least a part of the reactive polymer supported on the porous film is melted to cause a cross-linking reaction with the polyfunctional isocyanate in the electrolytic solution, thereby adhering to the porous film. Since strong adhesion occurs between the electrodes and the porous film, thermal contraction of the porous film in a high temperature environment is suppressed. Thus, according to the battery of the present invention, the battery characteristics in the normal temperature range are maintained, and the safety is ensured even when the battery is placed in a high temperature environment.

  As will be described later, in the present invention, the organic solvent for forming the electrolytic solution is not particularly limited. For example, the boiling point of the solvent often used in the electrolytic solution is 83 ° C. for dimethoxyethane, dimethyl carbonate. Is 90 ° C., ethyl methyl carbonate is 107 ° C., diethyl carbonate is 126 ° C., etc., and when the battery is placed in a high temperature environment such as 100 to 150 ° C., at least a part of the battery volatilizes, As described above, the separator is brought into close contact with the electrode.

  In the present invention, the polyfunctional isocyanate is not particularly limited. For example, aromatic, araliphatic such as phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, diphenyl ether diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, etc. In addition to alicyclic and aliphatic diisocyanates, so-called isocyanate adducts obtained by adding these diisocyanates to polyols such as trimethylolpropane are also preferably used.

  The proportion of the polyfunctional isocyanate in the electrolytic solution is usually in the range of 0.1 to 20 parts by weight with respect to 100 parts by weight of the reactive polymer supported on the porous film. When the proportion of the polyfunctional isocyanate is less than 0.1 parts by weight with respect to 100 parts by weight of the reactive polymer supported on the porous film, the reaction supported on the separator (porous film) in a high temperature environment The crosslinking reaction of the functional polymer with the polyfunctional isocyanate is insufficient, and a strong adhesion cannot be obtained between the electrode and the separator. However, when the proportion of the polyfunctional isocyanate is more than 20 parts by weight with respect to 100 parts by weight of the reactive polymer, the reactive polymer after crosslinking is too hard, so that the adhesion between the separator and the electrode is inhibited, May adversely affect battery characteristics.

  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. Further, a salt containing an inorganic acid such as sulfuric acid, borohydrofluoric acid, hydrofluoric acid, hexafluorophosphoric acid, perchloric acid, or an organic acid as an anionic component 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 electrolyte 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. In the following, the physical properties of the 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

Example 1
(Preparation of porous film)
Norbornene ring-opening polymer powder (Neonsolex 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 a polymer composition consisting of 80% by weight of 3.5 million ultra high molecular weight polyethylene and 84 parts by weight of fluid paraffin were mixed uniformly in a slurry state, using a small kneader at a temperature of 160 ° C. for about 60 minutes, After melt-kneading, the kneaded product thus obtained was sandwiched between metal plates cooled to 0 ° C. and rapidly cooled to obtain a sheet. Next, this sheet was heat-pressed at 115 ° C. to a thickness of 0.5 mm, and then simultaneously biaxially stretched 4.5 × 4.5 times in length and width at 115 ° C., and then the solvent was removed with heptane. Thereafter, the film thus obtained was heat-treated in air at 85 ° C. for 6 hours, and then heat-treated at 118 ° C. for 1.5 hours to obtain a target porous film. This porous film had a thickness of 25 μm, a porosity of 50%, and an average pore diameter of 0.1 μm.

(Preparation of reactive polymer)
40 parts by weight of acrylonitrile, 3 parts by weight of 2-hydroxyethyl acrylate, 15 parts by weight of methyl methacrylate, 45 parts by weight of 2-ethylhexyl acrylate, 0.3 parts by weight of azobisisobutylnitrile and 300 parts by weight of toluene are subjected to solution polymerization according to a conventional method. Thus, a toluene solution of the reactive polymer was obtained. The weight average molecular weight of this reactive polymer was about 350,000, and the glass transition temperature was 8 ° C.

(Preparation of heat shrinkage suppression porous film)
After applying the toluene solution of the above-mentioned reactive polymer in a plurality of parallel lines on a peelable stretched polypropylene resin film using a wire bar (wire diameter: 0.2 mm) and drying it, the porous film is coated with the porous film. The product was transferred to both front and back surfaces to obtain a reactive polymer-supported porous film.

(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% by weight. % Slurry was prepared. This slurry was applied to the surface of an aluminum foil having a thickness of 20 μm using a coating machine to a thickness of 200 μm, and then dried at 80 ° C. for 1 hour. Next, 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 using a coating machine to a thickness of 20 μm, and then dried at 80 ° C. for 1 hour. Next, 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.

(Preparation of negative electrode / porous film / positive electrode laminate)
The positive electrode sheet was brought into contact with and superposed on the surface of the reactive polymer-supported porous film, and the negative electrode sheet was brought into contact with and superposed on the back surface to obtain a negative electrode / porous film / positive electrode laminate.

(Assembly of the battery and evaluation of the characteristics of the obtained battery)
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. Further, 3 parts by weight of trifunctional isocyanate obtained by adding 3 parts by mole of hexamethylene diisocyanate to 1 part by mole of trimethylolpropane was dissolved in 100 parts by weight of the electrolytic solution.

  The negative electrode / porous film / positive electrode laminate is charged into a 2016-size coin battery can, and an electrolytic solution in which the trifunctional isocyanate is dissolved is poured into the coin-type battery can, and then the battery can is sealed. Thus, a coin-type lithium ion secondary battery was obtained.

  The 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, at a rate of 2.0 CmA. The discharge load characteristic evaluated by the ratio of discharge capacity / discharge capacity at a rate of 0.2 CmA was 90%.

(Measurement of adhesion force between electrode / porous film at room temperature)
Disassembling the assembled coin battery, and from the stress value required to peel the porous film from the positive electrode of the positive electrode / porous film / negative electrode laminate at 180 ° at room temperature (25 ° C.) with the electrolyte moistened. The adhesive strength was determined. As a result, in this example, the adhesive force at normal temperature between the positive electrode / porous film was 0.02 N / 10 mm.

(Measurement of heat shrinkage rate of porous film in electrode / porous film laminate when heat-treated at 150 ° C.)
In the same manner as described above, a positive electrode / porous film / negative electrode laminate was prepared and punched into a predetermined size to obtain a sample. The sample was impregnated with an electrolytic solution in which the trifunctional isocyanate was dissolved, and then sandwiched between glass plates, wrapped with a fluororesin sheet, and placed in a dryer at 150 ° C. for 1 hour. Thereafter, the negative electrode / porous film / positive electrode laminate was taken out from between the glass plates, the porous film was peeled off from the positive electrode and the negative electrode, read with a scanner, and the area shrinkage ratio with respect to the dimensions before shrinkage was determined. As a result, the heat shrinkage rate of the porous film of this example was 3%.

(Measurement of adhesion between electrode / porous film when heat-treated at 150 ° C.)
The battery obtained in “Assembly of battery” was put into a dryer at 150 ° C. for 1 hour and subjected to heat treatment. Thereafter, the battery is disassembled, and the stress value required for peeling the porous film from the positive electrode of the positive electrode / porous film / negative electrode laminate at 180 ° at room temperature (25 ° C.) in a state moistened with an electrolytic solution. The adhesive strength was determined. As a result, in this example, the adhesive strength at normal temperature between the positive electrode / porous film after heat treatment at 150 ° C. was 0.37 N / 10 mm.

Example 2
The same reactive polymer as in Example 1 was applied to a peelable stretched polypropylene resin film in the form of spots on 50% of its surface area, dried, and then transferred to both the front and back surfaces of the same porous film as in Example 1. Thus, a reactive polymer-supported porous film was obtained.

  A battery was assembled and its discharge load characteristics were evaluated in the same manner as in Example 1 except that this reactive polymer-supported porous film was used. The result was 92%. In addition, the battery was disassembled in the same manner as in Example 1 to determine the adhesive strength at normal temperature between the positive electrode and the porous film. The result was 0.01 N / 10 mm, and after heat treatment at 150 ° C. The adhesive force at normal temperature between the positive electrode / porous film was 0.28 N / 10 mm. Furthermore, when the heat shrinkage rate of the porous film was determined in the same manner as in Example 1, it was 7%.

Example 3
A maleic anhydride-modified ethylene-ethyl acrylate copolymer (AR201 manufactured by Mitsui Dupont Polychemical Co., Ltd.) was dissolved in toluene to prepare a 10 wt% concentration solution of the reactive polymer. This was applied to a peelable stretched polypropylene resin film in the form of spots on 30% of its surface area, and this was transferred to both the front and back surfaces of the same porous film as in Example 1 to obtain a reactive polymer-supported porous film. It was.

  A battery was assembled in the same manner as in Example 1 except that this reactive polymer-supported porous film was used, and its discharge load characteristics were evaluated. As a result, it was 94%. When this battery was disassembled and the adhesive strength at normal temperature between the positive electrode and porous film was determined, it was 0.01 N / 10 mm, and the heat treatment at 150 ° C. was performed at normal temperature between the positive electrode and porous film. The adhesive force was 0.35 N / 10 mm. Furthermore, when the heat shrinkage rate of the porous film was determined in the same manner as in Example 1, it was 3%.

Example 4
15 parts by weight of a mixture of 60% by weight of polyethylene having a weight average molecular weight of 200,000 and 40% by weight of ultra high molecular weight polyethylene having a weight average molecular weight of 1,500,000 and 85 parts by weight of liquid paraffin are uniformly mixed in a slurry state at a temperature of 160 ° C. Then, the mixture was melt-kneaded for about 60 minutes using a small kneader, and the kneaded product thus obtained was sandwiched between metal plates cooled to 0 ° C. and rapidly cooled to obtain a sheet. Next, the sheet was heat-pressed at 115 ° C. to a thickness of 0.5 mm, and then simultaneously biaxially stretched 4 × 4 times in length and width at 115 ° C., and then the solvent was removed with heptane. Thereafter, the film thus obtained was heat-treated in air at 85 ° C. for 1 hour, and then heat-treated at 116 ° C. for 1 hour to obtain a target porous film. This porous film had a thickness of 23 μm, a porosity of 43%, and an average pore diameter of 0.1 μm.

  A reactive polymer-supported porous film was obtained in the same manner as in Example 1 except that the porous film was used. Using this, a battery was assembled in the same manner as in Example 1 and its discharge load characteristics were obtained. Was found to be 91%, and the battery was disassembled in the same manner as in Example 1 to determine the adhesive strength between the positive electrode and the porous film at room temperature, and it was 0.02 N / 10 mm. Yes, the adhesive strength at normal temperature between the positive electrode / porous film after heat treatment at 150 ° C. was 0.35 N / 10 mm. Furthermore, when the heat shrinkage rate of the porous film was determined in the same manner as in Example 1, it was 4%.

Example 5
A formulation comprising 41 parts by weight of butyl acrylate, 41 parts by weight of methyl methacrylate, 15 parts by weight of acrylonitrile, 3 parts by weight of 4-hydroxybutyl acrylate, 0.1 part by weight of lauryl mercaptan and 3 parts by weight of a nonionic surfactant was added in water. And then subjected to emulsion polymerization according to a conventional method. The obtained reactive polymer was separated, purified and dried as a solid content, and dissolved in ethyl acetate to obtain a 10% ethyl acetate solution. The weight average molecular weight of this reactive polymer was about 2.3 million, and the glass transition temperature was 34 ° C. A porous film carrying the reactive polymer on both sides was obtained in the same manner as in Example 1 except that this reactive polymer was used.

  A battery was assembled in the same manner as in Example 1 except that this reactive polymer-supported porous film was used, and its discharge load characteristics were evaluated. As a result, it was 91%. When this battery was disassembled and the adhesive strength at normal temperature between the positive electrode / porous film was determined, it was 0.02 N / 10 mm, and it was heated at 150 ° C. at normal temperature between the positive electrode / porous film. The adhesive force was 0.43 N / 10 mm. Furthermore, when the heat shrinkage rate of the porous film was determined in the same manner as in Example 1, it was 2%.

Comparative Example 1
A battery was assembled in the same manner as in Example 1 without using the reactive polymer on the same porous film as in Example 1, and the discharge load characteristics were evaluated. The result was 95%. . Moreover, when the heat shrinkage rate of the said porous film was calculated | required like Example 1, it was 64%.

Comparative Example 2
In a toluene solution of the same reactive polymer as in Example 1, 3 parts by weight of trifunctional isocyanate formed by adding 3 parts by mole of hexamethylene diisocyanate to 1 part by mole of trimethylolpropane is dissolved in 100 parts by weight of the solid content. It was. In this way, a solution containing a reactive polymer and a trifunctional isocyanate was applied in a plurality of parallel lines on a peelable stretched polypropylene resin film using a wire bar (wire diameter: 0.2 mm), dried, and then carried out. The reactive polymer and trifunctional isocyanate were transferred to both the front and back surfaces of the same porous film as in Example 1. This porous film was put in a thermostatic chamber at a temperature of 70 ° C. for 2 days to crosslink the reactive polymer.

  A battery was assembled and its discharge load characteristics were evaluated in the same manner as in Example 1 except that the porous film carrying the crosslinked reactive polymer was used. The result was 53%. In the same manner as in Example 1, this battery was disassembled and the adhesive strength between the positive electrode and the porous film was determined, and it was 0.5 N / 10 mm. Between the positive electrode and the porous film after heat treatment at 150 ° C. The adhesive strength at room temperature was 0.65 N / 10 mm. Furthermore, when the heat shrinkage rate of the porous film was determined in the same manner as in Example 1, it was 0%.

Comparative Example 3
The same negative electrode / porous film / positive electrode laminate as in Example 1 was charged into a 2016-size coin battery can, and an electrolyte containing no trifunctional isocyanate was injected into the coin-type battery can. Sealing was performed to obtain a coin-type lithium ion secondary battery. With respect to this battery, the discharge load characteristics were evaluated in the same manner as in Example 1. As a result, it was 90%, and in the same manner as in Example 1, the battery was disassembled and the positive electrode / porous film was separated. The adhesion strength was determined to be 0.01 N / 10 mm, and the adhesion strength at normal temperature between the positive electrode / porous film after heat treatment at 150 ° C. was 0.02 N / 10 mm. Furthermore, when the heat shrinkage rate of the porous film was determined in the same manner as in Example 1, it was 58%.

Claims (3)

  A glass transition temperature is in the range of 0 to 100 ° C., and a reactive polymer having a functional group capable of reacting with an isocyanate group under heating is supported on a porous film, and the porous film is sandwiched between and in contact with the porous film. A battery in which a positive electrode and a negative electrode are stacked to form an electrode / porous film laminate, and the electrode / porous film laminate is charged into a battery container together with an electrolyte containing polyfunctional isocyanate, A battery characterized in that an adhesive force by the reactive polymer between the porous film and the electrode in the presence of an electrolytic solution is 0.05 N / 10 mm or less.   The battery according to claim 1, wherein the reactive polymer has a carboxyl group or a hydroxyl group as a functional group. The battery according to claim 1, wherein the area shrinkage of the porous film when the electrode / porous film laminate is heat-treated at 150 ° C. for 1 hour in the presence of an electrolytic solution is 20% or less.