JP2005353584A - Lithium-ion secondary battery and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce efficiently a lithium ion secondary battery in which deterioration of capacity accompanying repetition of charge and discharge cycle is suppressed. <P>SOLUTION: The lithium ion secondary battery is equipped with a positive electrode including a positive electrode core material and a positive electrode mixture layer carried by the positive electrode core material, a negative electrode including a negative electrode core material and a negative electrode mixture layer carried by the negative electrode core material, a separator, a non-aqueous electrolytic solution containing a non-aqueous solvent including carbonic ester and a solute dissolved in the non-aqueous solvent, and a porous membrane adhered on one of the surface of the positive electrode and the negative electrode. The porous membrane contains an inorganic filler and a membrane binding agent, and the solubility parameter of the membrane binding agent is different from the solubility parameter of the non-aqueous solvent by one or more. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lithium ion secondary battery, and mainly relates to improvement of life characteristics of the lithium ion secondary battery.

  A lithium ion secondary battery has an electrode plate group including a positive electrode, a negative electrode, and a separator that is interposed between the positive electrode and the negative electrode and holds a nonaqueous electrolytic solution. The positive electrode includes a positive electrode core material and a positive electrode mixture layer supported on the positive electrode core material, and the negative electrode includes a negative electrode core material and a negative electrode mixture layer supported on the negative electrode core material. For the separator, a microporous sheet containing polyethylene resin or the like is used. The positive and negative electrode mixture layers include an electrode active material and an electrode binder. Conventionally, a thermoplastic resin or a modified rubber material is used as the electrode binder.

  To produce positive and negative electrodes, first, an electrode mixture containing an electrode active material and an electrode binder is mixed with an electrode dispersion medium to prepare an electrode mixture slurry. Next, the obtained electrode mixture slurry is applied to an electrode core material, and the applied slurry is dried to form an electrode mixture layer. The drying temperature is generally 130 ° C. or lower, and drying is performed using hot air. The electrode mixture layer after drying is rolled with a roll press, and then the electrode core material and the electrode mixture layer are cut into a predetermined shape together to obtain a desired electrode.

  In recent years, a technique for adhering a porous film to the surface of an electrode has been proposed from the viewpoint of improving the quality of a lithium ion secondary battery. In order to adhere the porous film to the electrode surface, first, a film mixture containing an inorganic filler and a film binder is mixed with a film dispersion medium to prepare a porous film paste. Next, the porous film paste is applied to the electrode mixture layer, and the applied paste is dried to form a porous film (see Patent Document 1).

Conventionally, as an electrode binder contained in an electrode mixture, a resin material that is dissolved or uniformly dispersed in an electrode dispersion medium used when preparing an electrode mixture slurry is used. For the membrane binder contained in the porous membrane, a resin material that is dissolved or uniformly dispersed in the membrane dispersion medium used when preparing the porous membrane paste is used. For example, N-methyl-2-pyrrolidone (NMP) is used as the electrode dispersion medium and the membrane dispersion medium.
Japanese Patent No. 3371301

  Generally, in order to dissolve or uniformly disperse the membrane binder in the membrane dispersion medium, it is necessary that the affinity between the membrane binder and the membrane dispersion medium be high. When the most common NMP is used as the membrane dispersion medium, a material having a solubility parameter of about 9 to 11 is selected as the membrane binder. This is in order to obtain a uniform coating film free from lumps and unevenness of the binder. As a result, a porous film having a high yield and stable quality can be formed.

However, when a membrane binder as described above is used, depending on the combination of the membrane binder and the solvent type of the non-aqueous electrolyte, the membrane binder may dissolve or swell in the electrolyte. Battery performance may be reduced. This is because the conductivity of the electrolytic solution decreases when the membrane binder swells to block or dissolve the pores of the porous membrane.
That is, an object of the present invention is to provide a porous film having improved quality and excellent battery performance in the production process of the porous film, thereby providing a battery having both safety and battery performance.

  When the solubility parameter of the membrane binder that is dissolved or uniformly dispersed in the dispersion medium and the solubility parameter of the non-aqueous solvent of the non-aqueous electrolyte are particularly approximated, the present inventors have the above-mentioned problems. As a result of studying in detail the relationship between the solubility parameter of the membrane binder and the solubility parameter of the nonaqueous solvent, the present invention has been completed.

  The solubility parameter is an index indicating the polarity of substances, for example, an index of affinity between substances. In general, the closer the solubility parameters between substances, the better the compatibility of those substances (see Physics Dictionary, Baifukan Publishing). For example, the solubility parameter of a dispersion medium such as NMP is close to the solubility parameter of a non-aqueous solvent containing a carbonate, and these are highly compatible. Therefore, it is considered that the membrane binder dissolved or uniformly dispersed in the membrane dispersion medium has high compatibility with a non-aqueous solvent containing a carbonic ester and is likely to swell in the non-aqueous solvent.

  In view of the above, the present invention includes (a) a positive electrode including a positive electrode core material and a positive electrode mixture layer supported on the positive electrode core material, and (b) a negative electrode core material and a negative electrode mixture layer supported on the negative electrode core material. A negative electrode, (c) a separator, (d) a non-aqueous electrolyte containing a non-aqueous solvent containing a carbonate and a solute dissolved in the non-aqueous solvent, and (e) adhered to at least one surface of the positive electrode and the negative electrode The present invention relates to a lithium ion secondary battery comprising a porous film, wherein the porous film includes an inorganic filler and a film binder, and the solubility parameter of the film binder is one or more different from the solubility parameter of the nonaqueous solvent.

  The present invention also includes (a) a step of preparing an electrode mixture slurry by mixing an electrode mixture containing an electrode active material and an electrode binder with an electrode dispersion medium, and (b) an electrode mixture slurry. Is applied to the electrode core material, and the applied slurry is dried to form an electrode mixture layer. (C) A solute is dissolved in a non-aqueous solvent containing a carbonate to prepare a non-aqueous electrolyte. (D) a step of mixing a membrane mixture containing an inorganic filler and a membrane binder with a membrane dispersion medium to prepare a porous membrane paste, (e) a porous membrane paste as an electrode mixture Applying to the surface of the layer, drying the applied paste to form a porous film, and (f) assembling a battery using an electrode having a porous film and a non-aqueous electrolyte, The solubility parameter of the membrane binder is one or more different from that of the non-aqueous solvent. It relates to a process for the preparation of ion secondary battery.

  It is preferable that the film binder includes a heat crosslinkable resin, and the curing of the heat crosslinkable resin is completed in a state before liquid injection in the battery manufacturing process. Furthermore, the heat-crosslinking resin is preferably a one-pack type from the viewpoint of simplifying the manufacturing process of the porous film paste.

  In the electrolytic solution, the solubility parameter of the non-aqueous solvent containing a carbonate is preferably 11.5-14. Moreover, if the solubility parameter is within the above range, a solvent other than the carbonate ester can be used.

The solubility parameter of the electrode dispersion medium is preferably different from that of the non-aqueous solvent by one or more.
The solubility parameter of the membrane dispersion medium is preferably different from that of the non-aqueous solvent by one or more.

  According to the present invention, it is possible to obtain a uniform coating film free from lumps and unevenness of the binder in the manufacturing process of the porous film, so that the yield and quality can be improved. Furthermore, it is possible to prevent the pores of the porous membrane from being blocked by swelling of the membrane binder with the electrolyte solution, and the conductivity of the electrolyte solution from being lowered due to the membrane binder being dissolved in the electrolyte solution. Therefore, a decrease in battery performance can be avoided.

The form of the lithium ion secondary battery according to the present invention is not particularly limited and includes various types such as a cylindrical type, a square type, and a laminated type. In particular, the positive electrode and the negative electrode are wound through a separator. This is effective in a cylindrical or square battery including the electrode plate group.
FIG. 1 is a longitudinal sectional view of an example of a general cylindrical lithium ion secondary battery. The positive electrode 5 and the negative electrode 6 are wound through a separator 7 and constitute a columnar electrode plate group. One end of a positive electrode lead 5 a is connected to the positive electrode 5, and one end of a negative electrode lead 6 a is connected to the negative electrode 6. The electrode plate group impregnated with the nonaqueous electrolyte is accommodated in the inner space of the battery can 1 while being sandwiched between the upper insulating ring 8a and the lower insulating ring 8b. A separator is interposed between the electrode plate group and the inner surface of the battery can 1. The other end of the positive electrode lead 5 a is welded to the back surface of the battery lid 2, and the other end of the negative electrode lead 6 a is welded to the inner bottom surface of the battery can 1. The opening of the battery can 1 is closed by a battery lid 2 having an insulating packing 3 disposed on the periphery.

  Although not shown in FIG. 1, a porous film having an electronic insulating property is bonded to at least one surface of the positive electrode and the negative electrode. The porous membrane contains filler particles and a membrane binder. In the porous membrane, when the internal short circuit occurs, a large amount of heat is generated, and the separator contracts, the positive electrode mixture or current collector and the negative electrode mixture or current collector are directly replaced with the separator. Play a role to prevent contact. FIG. 1 is only one form of the lithium ion secondary battery according to the present invention, and the scope of the present invention is not limited to the case of FIG.

  The positive electrode includes a positive electrode core material and a positive electrode mixture layer carried thereon. An aluminum foil or the like is preferably used as the positive electrode core material. The positive electrode mixture layer generally includes a positive electrode active material, a positive electrode binder, and a conductive agent. The negative electrode includes a negative electrode core material and a negative electrode mixture layer carried thereon. As the negative electrode core material, a copper foil or a nickel foil is preferably used. The negative electrode mixture layer generally contains a negative electrode active material and a negative electrode binder.

  In the present invention, the membrane binder of the porous membrane has a solubility parameter that is one or more different from the solubility parameter of the nonaqueous solvent of the nonaqueous electrolyte. When the solubility parameter of the membrane binder is one or more different from the solubility parameter of the non-aqueous solvent of the non-aqueous electrolyte, the swelling of the porous membrane by the non-aqueous electrolyte can be remarkably suppressed.

  A non-aqueous electrolyte used for a lithium ion secondary battery includes a non-aqueous solvent containing a carbonate and a solute that dissolves therein. The solubility parameter of a non-aqueous solvent containing a carbonate ester approximates that of NMP. Therefore, a conventional membrane binder that dissolves in NMP, that is, a resin whose solubility parameter is close to the solubility parameter of the electrolytic solution is not suitable in the present invention.

  When the difference between the solubility parameter of the membrane binder and the solubility parameter of the non-aqueous solvent of the non-aqueous electrolyte is less than 1, swelling of the porous membrane by the non-aqueous electrolyte cannot be suppressed. In order to remarkably improve the life characteristics of the lithium secondary battery, it is desirable that the difference in solubility parameter is 1 or more, more preferably 1.5 or more.

The solubility parameter (SP) of the substance is expressed by the following formula.
SP = ΔE / V = (ΔH−RT) / V = (C / M) (ΔH−RT)
ΔE: Evaporation energy (cal / mol)
V: Molecular volume (ml / mol)
ΔH: latent heat of vaporization (cal / mol)
R: Gas constant (cal / mol)
C: Density (g / ml)
M: Molecular weight T: Absolute temperature (K)

The solubility parameter of the non-aqueous solvent containing carbonate ester is, for example, 11.5-14. Examples of the carbonate ester include ethylene carbonate (EC, solubility parameter: 14.7), propylene carbonate (PC, solubility parameter: 13.3), dimethyl carbonate (DMC, solubility parameter: 9.9), diethyl carbonate (DEC, Solubility parameter: 8.8), methyl ethyl carbonate (MEC), etc. can be mentioned. Although carbonate ester can also be used individually by 1 type, it is preferable to use combining 2 or more types. When using a mixed solvent in which two or more kinds are combined, the sum (ΣSP _n V _n ) of the product (SP _n V _n ) of the solubility parameter (SP _n ) of each component and the volume ratio (V _n ) of each component Can be used as the solubility parameter of the mixed solvent.

  The resin used as the membrane binder is preferably a thermally cross-linked resin from the viewpoint of suppressing the swelling of the porous membrane due to the non-aqueous electrolyte. A thermally crosslinkable resin means a resin that can undergo a crosslinking reaction by heating. The heat-crosslinking resin can be substantially dissolved in the dispersion medium for film before heating, and a suitable paste for the film can be obtained. If the crosslinking reaction is allowed to proceed after heating, that is, after the coating is formed, dissolution and swelling in the electrolyte solution can be prevented. As a result, the discharge rate characteristics of the battery even under severe use conditions at high temperatures And life characteristics can be enhanced. In the present specification, the thermally crosslinkable resin can also be referred to as a curable resin. Moreover, hardening means progressing cross-linking, and the heat-crosslinking resin that has been cross-linked is also referred to as a cured product. The cured product preferably has a solubility in the non-aqueous electrolyte (wt% of the component dissolved in the electrolyte in the cured product) of 5 wt% or less.

  From the viewpoint of imparting the above properties to the thermally crosslinkable resin, the thermally crosslinkable resin preferably has a crosslinkable group capable of forming a crosslinked structure by heating. Examples of the crosslinkable group include an epoxy group, a hydroxyl group, an N-methylolamide group (N-oxymethylamide group), and an oxazolyl group.

  The thermally crosslinkable resin as the membrane binder is preferably a resin having a masked crosslinking point because it is easy to handle and the crosslinking reaction is easily controlled. The “masked cross-linking point” refers to an active point that is temporarily inactivated by some method, such as shielding by a molecular chain, or an active point newly generated by a change in molecular structure. When the resin having a masked cross-linking point reaches a predetermined temperature, the masked cross-linking point is activated (revived) and a cross-linking reaction is started.

  Further, it is more preferable that the thermally cross-linked resin having a masked cross-linking point is a one-pack type from the viewpoint of simplifying the manufacturing process of the porous film paste. In the conventional two-pack type heat-crosslinking resin using a cross-linking agent having no masked cross-linking point, the cross-linking reaction is performed in the preparation process of the porous film paste, for example, the mixing step of the film mixture and the film dispersion medium. Progresses. Therefore, the porous film paste is excessively thickened, and the viscosity and dispersion state of the porous film paste during storage are also unstable. As a result, the coating process of the porous film paste is not stable. On the other hand, the above-mentioned problems can be improved by using the one-pack type heat-crosslinking resin having a masked cross-linking point of the present invention.

  Here, the one-component resin refers to a curable resin that maintains a liquid state even when left at a predetermined temperature for a certain period of time. As the one-component resin used in the present invention, a stable resin that only progresses to a crosslinking reaction of 5% or less even when it is mixed with a dispersion medium, for example, when left at 40 ° C. for 72 hours, is used. desirable. The degree of progress of the crosslinking reaction can be determined, for example, by differential scanning calorimetry (DSC).

  The weight average molecular weight of the resin used as the membrane binder, particularly a one-part thermally cross-linked resin, is preferably 3,000 to 300,000. When the weight average molecular weight is less than 3000, the filler particles may be easily precipitated in the porous film paste in which the filler particles are dispersed. Moreover, when the weight average molecular weight exceeds 300,000, the viscosity of the porous film paste may become too high.

  Resins used as membrane binders, especially one-part thermally cross-linked resins, contain a hydrophilic group with a high degree of dissociation in the molecular chain. This is preferable in that the balance with the stability of the dispersed state is excellent. Highly dissociated hydrophilic groups include groups containing sulfur or phosphorus (groups of strong acid salts) such as sulfuric acid groups, sulfonic acid groups, phosphoric acid groups, acidic phosphoric acid ester groups, phosphonic acid groups, Strong electrolyte groups such as quaternary ammonium groups are preferred.

  A resin containing a hydrophilic group with a high degree of dissociation can be obtained, for example, by copolymerizing a monomer containing a hydrophilic group with a high degree of dissociation and a monomer copolymerizable therewith. . Monomers containing hydrophilic groups with a high degree of dissociation include monomers containing groups of strong acid salts containing sulfur such as unsaturated organic sulfonates and unsaturated organic sulfates, and unsaturated organic phosphoric acids. Examples thereof include monomers containing strong acid salt groups containing phosphorus such as salts and unsaturated organic phosphonates, and unsaturated monomers containing groups of quaternary ammonium salts.

  Examples of the monomer copolymerizable with a monomer containing a hydrophilic group having a high dissociation degree include, for example, methyl acrylate, acrylic acid-n-propyl, isopropyl acrylate, acrylic acid-t-butyl, and hexyl acrylate. Alkyl acrylates such as cyclohexyl acrylate, dodecyl acrylate, lauryl acrylate; methyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, t-butyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, methacrylic acid Methacrylic acid alkyl esters such as dodecyl acid lauryl methacrylate; alkyl esters of unsaturated polycarboxylic acids such as dimethyl fumarate, diethyl maleate, butylbenzyl maleate; -2-methoxyethyl acrylate, methacrylic acid-2- Unsaturated carboxylic acid ester containing alkoxy group such as toxiethyl; α, β-unsaturated nitrile such as acrylonitrile, methacrylonitrile; carboxylic acid vinyl ester such as vinyl acetate and vinyl propionate; vinyl chloride, vinyl fluoride, bromide Halogenated olefins such as vinyl, vinylidene chloride, vinylidene fluoride, ethylene trifluoride, tetrafluoroethylene, and hexafluoropropylene; vinyl ethers such as methyl vinyl ether, isobutyl vinyl ether, and cetyl vinyl ether; unsaturateds such as maleic acid and itaconic acid Unsaturated carboxylic acid anhydrides such as carboxylic acid, maleic anhydride, itaconic anhydride, unsaturated carboxylic acid amides such as (meth) acrylamide, N, N-dimethyl (meth) acrylamide; α-oleic such as ethylene and propylene Fin; vinylidene cyanide; and the like. In particular, a copolymer containing an acrylonitrile unit is preferable in that it has an excellent balance between flexibility and strength.

  A method of copolymerizing a monomer containing a hydrophilic group having a high degree of dissociation and a monomer copolymerizable therewith is not particularly limited. For example, a solution polymerization method, a suspension polymerization method, an emulsion weight Legal or the like can be used. Examples of the polymerization initiator used for the polymerization include lauroyl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, 3,5,5-trimethylhexanoyl peroxide. Organic peroxides such as; azo compounds such as α, α′-azobisisobutyronitrile; persulfates such as ammonium persulfate and potassium persulfate;

  It is desirable that the one-part resin having a masked crosslinking point contains a polyacrylonitrile chain. This is because a resin containing a polyacrylonitrile chain is excellent in the balance between flexibility and strength. For example, in the vicinity of the center of the columnar electrode plate group, the radius of the cylinder formed by the electrode plate is very small and is generally about 0.5 to 1.5 mm. Therefore, the porous film adhered to the electrode plate surface is similarly bent. Therefore, it is desired to form a porous film excellent in flexibility, which is not damaged even when bent in this manner, on the electrode plate.

  The thermally crosslinkable resin as the membrane binder is preferably one that undergoes a rapid crosslinking reaction at 100 ° C. or higher. Therefore, the temperature at which the masked crosslinking point is activated (revived) is preferably 100 ° C. or higher. When the temperature at which the crosslinking point is activated is less than 100 ° C., the paste temperature becomes high during the preparation process of the porous film paste, for example, the mixing of the film mixture and the film dispersion medium. The paste viscosity becomes unstable. In addition, if the temperature at which the crosslinking reaction proceeds is too high, an electrode constituent material such as an active material may be deteriorated during the crosslinking reaction. Therefore, the temperature at which the crosslinking point is activated is preferably 220 ° C. or lower. . The temperature at which the crosslinking point is activated is defined as the peak temperature of the endothermic peak obtained in, for example, differential scanning calorimetry (DSC).

In addition to the thermally crosslinkable resin or its cured product, various resin components can be used for the film binder. For example, styrene-butadiene rubber (SBR), modified SBR containing acrylic acid units or acrylate units, polyethylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer ( FEP), polyacrylic acid derivatives, polyacrylonitrile derivatives, and the like can be used. These may be used alone or in combination of two or more. Of these, polyacrylic acid derivatives and polyacrylonitrile derivatives are particularly preferable. These derivatives preferably contain at least one selected from the group consisting of a methyl acrylate unit, an ethyl acrylate unit, a methyl methacrylate unit, and an ethyl methacrylate unit in addition to the acrylic acid unit and / or the acrylonitrile unit. .
In the present invention, it is particularly preferable to use a film binder comprising only a heat crosslinkable resin or a cured product thereof, or a film binder comprising a heat crosslinkable resin or a cured product thereof and another resin component. The proportion of the thermally crosslinkable resin or the cured product thereof in the entire film binder is preferably 50% by weight or more.

  In general, a lithium ion secondary battery includes a step of preparing an electrode mixture slurry by mixing an electrode mixture containing an electrode active material and an electrode binder with an electrode dispersion medium, Applying to the core material, drying the applied slurry to form an electrode mixture layer, dissolving the solute in a non-aqueous solvent containing a carbonate to prepare a non-aqueous electrolyte, and A step of assembling the battery using the prepared electrode and the non-aqueous electrolyte. In the present invention, a film mixture containing an inorganic filler and a film binder is further mixed with a film dispersion medium to prepare a porous film paste, and the porous film paste is formed into an electrode mixture layer. The process of apply | coating and drying the apply | coated paste and forming a porous film is performed.

  When an organic solvent is used as the dispersion medium, it is common to use steam as a heat source for the coating film dryer from the viewpoint of ensuring safety. However, the ultimate temperature of a coating film dryer using steam as a heat source is usually about 130 ° C. or lower. Therefore, when NMP having a boiling point of 202 ° C. is used as a dispersion medium, it takes time for drying, which hinders improvement in productivity. Therefore, it is more preferable to use, for example, methyl ethyl ketone (MEK), cyclohexanone (ANON) or the like as the electrode dispersion medium or the membrane dispersion medium. In particular, when methyl ethyl ketone is used as the electrode dispersion medium, the amount of water absorbed by the electrode mixture slurry is significantly lower than that of conventional NMP, so that the production process is less susceptible to environmental changes. Accordingly, the change in the viscosity of the electrode mixture slurry is also reduced, and stable application to the electrode core material becomes possible.

  The electrode mixture slurry can be prepared by mixing an electrode mixture containing an active material and an electrode binder with an electrode dispersion medium. As the electrode dispersion medium, it is preferable to use one that dissolves the electrode binder. The electrode binder contained in the electrode mixture slurry is preferably, for example, 1 to 6 parts by weight per 100 parts by weight of the active material.

  Next, the electrode mixture slurry is applied to the electrode core material, and the obtained coating film is heated. The electrode dispersion medium is volatilized by heating. In addition, it is preferable to roll the electrode coating film after drying with a roll press to adjust the density of the electrode mixture layer.

  The porous film paste can be prepared by mixing a film mixture containing an inorganic filler and a film binder with a film dispersion medium. As the membrane dispersion medium, it is preferable to use one that dissolves the membrane binder. The film binder contained in the porous film paste is preferably 1 to 10 parts by weight, more preferably 3.5 to 10 parts by weight, per 100 parts by weight of the inorganic filler. If the proportion of the membrane binder is too large, the battery performance tends to be lowered, and if the proportion of the membrane binder is too small, the strength of the porous membrane may be insufficient.

  Next, the porous film paste is applied to at least one surface of the positive electrode and the negative electrode, and the obtained coating film is heated. The membrane dispersion medium is volatilized by heating. In the case of using a membrane binder containing a thermally crosslinkable resin, subsequently, a crosslinking reaction of the thermally crosslinkable resin is allowed to proceed. In the porous film thus obtained, since the thermally cross-linked resin forms a cured product, a porous film having excellent strength can be obtained. Note that the membrane dispersion medium may be volatilized at a temperature at which the crosslinking reaction of the membrane binder hardly proceeds, and then the membrane binder may be crosslinked. Alternatively, the membrane dispersion medium may be volatilized and bonded. The crosslinking reaction of the agent may proceed simultaneously.

As the positive electrode active material, composite lithium oxide is preferably used. The composite lithium oxide is not particularly limited, lithium cobaltate (LiCoO _2), modified lithium cobaltate, lithium nickelate (LiNiO _2), modified lithium nickelate, lithium manganate (LiMn ₂ O ₄ ), Modified products of lithium manganate, and those obtained by substituting a part of Co, Mn or Ni of these oxides with other transition metal elements. Some modified bodies contain elements such as aluminum and magnesium. There are also those containing at least two of cobalt, nickel and manganese. Mn-based lithium-containing transition metal oxides such as LiMn ₂ O ₄ are particularly promising because they are abundant on the earth and are inexpensive.

  Although it does not specifically limit as a negative electrode active material, Carbon materials, such as various natural graphite, various artificial graphite, petroleum coke, carbon fiber, organic polymer baked material, silicon-containing composite materials, such as an oxide and a silicide, various metals or alloys Materials can be used.

  A conductive agent can be included in the positive electrode mixture layer or the negative electrode mixture layer. As such a conductive agent, acetylene black, ketjen black (registered trademark), various graphites, and the like can be used. These may be used alone or in combination of two or more.

Various resin materials can be used for the electrode binder.
Examples of the positive electrode binder include polytetrafluoroethylene (PTFE), polyacrylic acid derivative rubber particles (such as “BM-500B (trade name)” manufactured by Nippon Zeon Co., Ltd.), and polyvinylidene fluoride (PVdF). Can be used. PTFE and BM-500B are CMC, polyethylene oxide (PEO), and modified acrylonitrile rubber ("BM-720H (trade name)" manufactured by Nippon Zeon Co., Ltd.), which are thickeners for the raw material paste of the positive electrode mixture layer. It can also be used in combination with. Even if PVdF is single, it has a function as a positive electrode binder and a function as a thickener.

  As the negative electrode binder, the same as the positive electrode binder can be used, but a rubbery polymer is preferably used. As the rubbery polymer, those containing a styrene unit and a butadiene unit are preferably used. For example, a styrene-butadiene copolymer (SBR), a modified SBR, or the like can be used, but it is not limited thereto. These rubbery polymers are preferably in the form of particles. The rubber-like polymer exhibiting a particulate form can point-bond the active material particles to each other. Therefore, a negative electrode mixture layer excellent in lithium ion acceptability can be obtained without covering the surface of the negative electrode active material. When the negative electrode binder and the negative electrode thickener are used in combination, a water-soluble polymer is preferably used as the negative electrode thickener. Cellulosic resins are preferred, and carboxymethyl cellulose (CMC) is particularly preferred.

  It is desired that the inorganic filler used for the porous film is electrochemically stable under the usage environment of the lithium ion secondary battery. The inorganic filler is desirably a material suitable for preparing a porous film paste.

The BET specific surface area of the inorganic filler is, for example, preferably 0.9 m ² / g or more, more preferably 1.5 m ² / g or more. Further, from the viewpoint of suppressing the aggregation of the inorganic filler and optimizing the fluidity of the porous film paste, the BET specific surface area is not too large, and is preferably 150 m ² / g or less, for example. The average particle diameter (number-based median diameter) of the inorganic filler is preferably 0.1 to 5 μm.

  In view of the above, the inorganic filler is preferably an inorganic oxide such as alumina (aluminum oxide), magnesia (magnesium oxide), calcium oxide, titania (titanium oxide), zirconia (zirconium oxide), talc, silica, and the like. Can be preferably used. In particular, it is preferable to use α-alumina or Macnesia.

  The non-aqueous solvent containing the carbonate ester can contain other components other than the carbonate ester within a range having a predetermined solubility parameter. Examples of other components include, but are not limited to, chain ethers (eg, dimethyl ether, diethyl ether), cyclic ethers (eg, tetrahydrofuran), chain carboxylic acid esters (eg, methyl formate, methyl acetate, ethyl propionate, etc.) ), Cyclic carboxylic acid esters (for example, γ-butyrolactone, γ-valerolactone, etc.) can be used. However, it is preferable that other components are 30 weight% or less of the whole non-aqueous solvent.

As the solute dissolved in the non-aqueous solvent, it is preferable to use a lithium salt. Examples of the lithium salt include lithium hexafluorophosphate (LiPF ₆ ), lithium perchlorate (LiClO ₄ ), and lithium borofluoride (LiBF ₄ ). The solute concentration dissolved in the non-aqueous solvent is generally 0.5 to 2 mol / L.

In order to improve the cycle life of the battery, an additive that forms a good film on the electrode plate can be mixed with the non-aqueous electrolyte. As such an additive, vinylene carbonate (VC), vinyl ethylene carbonate (VEC), a modified product of VC or VEC, or the like can be used.
Moreover, in order to improve the high temperature storage characteristic of a battery, the additive which coat | covers a positive electrode can be mixed with a non-aqueous electrolyte. As such an additive, propane sultone (PS), ethylene sulfite (ES), a modified product of PS or ES, and the like can be used.
Moreover, in order to improve the stability at the time of overcharge of a battery, the additive which forms a film at the time of overcharge can be mixed with a non-aqueous electrolyte. As such an additive, cyclohexylbenzene (CHB) or a modified product thereof can be used.

A separator will not be specifically limited if it consists of a material which can endure the use environment of a lithium ion secondary battery. In general, a microporous sheet containing a polyolefin resin is used as a separator. Examples of the polyolefin resin include polyethylene and polypropylene. The microporous sheet may be a single layer film containing one kind of polyolefin resin or a multilayer film containing two or more kinds of polyolefin resins. The thickness of the separator is preferably 8 to 30 μm.
EXAMPLES Next, although this invention is demonstrated concretely based on an Example, this invention is not limited to a following example.

[Example]
First, evaluation methods performed in the following examples and comparative examples will be described.
(Capacity maintenance rate after 500 cycles)
The completed battery was precharged / discharged twice and stored in a 45 ° C. environment for 7 days. Then, charging / discharging of the following patterns was repeated 500 times in a 20 degreeC environment. The ratio of the discharge capacity at the 500th cycle to the initial discharge capacity was determined as the capacity retention rate.
Constant current charge: 1400mA (end voltage 4.2V)
Constant voltage charge: 4.2V (end current 100mA)
Constant current discharge: 400mA (end voltage 3V)

(Measurement of molecular weight of binder)
The weight average molecular weight of the resin used for the membrane binder or the electrode binder was determined as a polystyrene equivalent value by gel permeation chromatography using N-methyl-2-pyrrolidone as a solvent.

(Solubility parameter)
When using a thermally crosslinkable resin for the membrane binder or electrode binder, the thermally crosslinkable resin is heated at 170 ° C. for 24 hours, and then at 60 ° C. in various solvents with known solubility parameters. The solvent in which the volume ratio after immersion was the largest after immersion was found for 72 hours, and the solubility parameter of the solvent was used as the solubility parameter of the thermally crosslinkable resin. In addition, the solvent with a known solubility parameter used the some solvent in which the solubility parameter differs 0.1 each and is contained in the range of 8.0-12.0. In the case of a binder that does not crosslink, it was determined in the same manner using a molded product at 100 ° C. or lower.

<< Reference Example 1 >>
(A) Fabrication of positive electrode 100 parts by weight of lithium cobaltate, 4 parts by weight of acrylonitrile copolymer as a positive electrode binder, 1 part by weight of acetylene black, and an appropriate amount of electrode dispersion medium are kneaded in two arms. The mixture was stirred in a machine to prepare a positive electrode mixture slurry having a nonvolatile component content of 50% by weight. This slurry was applied to both surfaces of a 15 μm thick aluminum foil as a positive electrode core material and dried at 120 ° C. Thereafter, the dried coating film was roll-pressed to form a positive electrode mixture layer having a density of 3.3 g / cm ³ . Under the present circumstances, the thickness of the electrode plate which consists of aluminum foil and a positive mix layer was controlled to 160 micrometers. Next, the electrode plate was slit to a width that could be inserted into a can battery case of a cylindrical battery (Part No. 18650) to obtain a positive electrode hoop.

(B) Production of negative electrode 100 parts by weight of artificial graphite, 2 parts by weight of styrene-butadiene rubber derivative (a rubber component of BM-400B manufactured by Nippon Zeon Co., Ltd.) as a negative electrode binder, and CMC1 as a thickener Part by weight and an appropriate amount of water were stirred with a double-arm kneader to prepare a negative electrode mixture slurry. This slurry was applied to both sides of a 10 μm-thick copper foil as a negative electrode core material, dried and then roll-pressed to form a negative electrode mixture layer having a density of 1.4 g / cm ³ . Under the present circumstances, the thickness of the electrode plate which consists of copper foil and a negative mix layer was controlled to 180 micrometers. Thereafter, the electrode plate was slit to a width that could be inserted into a can battery case of a cylindrical battery (Part No. 18650) to obtain a negative electrode hoop.

As the positive electrode binder (acrylonitrile copolymer), copolymers A to E containing acrylonitrile units (units), dodecyl acrylate units, and butadiene monooxide units and having different solubility parameters were used. The weight average molecular weight of each copolymer is as follows.
Copolymer A: 178000
Copolymer B: 155000
Copolymer C: 143000
Copolymer D: 126000
Copolymer E: 137000

  As the positive electrode dispersion medium, an electrode dispersion medium having a solubility parameter that is the same as or close to the solubility parameter of the positive electrode binder (acrylonitrile copolymer) contained in the positive electrode mixture slurry was used.

  Specifically, in the positive electrode mixture slurry containing the copolymer A (solubility parameter: 11.3), N-methyl-2-pyrrolidone (NMP, solubility parameter: 11.3, boiling point: 202 ° C.) was used.

  Further, in the positive electrode mixture slurry containing the copolymer D (solubility parameter: 9.8) and the copolymer E (solubility parameter: 9.3), cyclohexanone (ANON, solubility parameter: 9. 9, boiling point 155 ° C.).

  Further, the positive electrode mixture slurry containing the copolymer B (solubility parameter: 10.8) and the copolymer C (solubility parameter: 10.3) includes N-methyl-2-pyrrolidone as a positive electrode dispersion medium, A mixed solvent with cyclohexanone (weight ratio is NMP: ANON = 7: 3) was used.

(C) Preparation of non-aqueous electrolyte ethylene carbonate (EC, solubility parameter: 14.7), dimethyl carbonate (DMC, solubility parameter: 9.9), diethyl carbonate (DEC, solubility parameter: 8.8) Is dissolved in a mixed solvent (solubility parameter: 11.6) at a volume ratio of 4: 4: 2, LiPF ₆ is dissolved at a concentration of 1 mol / L, and 3% by weight of vinylene carbonate (VC) is further added. A water electrolyte was used.

(D) Production of Battery A cylindrical battery having a product number of 18650 was produced using the positive electrode, the negative electrode, and the non-aqueous electrolyte described above. First, the positive electrode and the negative electrode were each cut to a predetermined length. One end of a positive electrode lead was connected to the positive electrode core material. Further, one end of a negative electrode lead was connected to the negative electrode core material. Thereafter, the positive electrode and the negative electrode were wound through a separator made of a polyethylene resin microporous sheet having a thickness of 20 μm to form a columnar electrode plate group. The outer surface of the electrode plate group was interposed with a separator. The electrode plate group was accommodated in the inner space of the battery can while being sandwiched between the upper insulating ring and the lower insulating ring. Next, 5 g of the above non-aqueous electrolyte solution was weighed and poured into a battery can, and the electrode plate group was impregnated with the non-aqueous electrolyte solution in a reduced pressure atmosphere of 133 Pa. The other end of the positive electrode lead was welded to the back surface of the battery lid. The other end of the negative electrode lead was welded to the inner bottom surface of the battery can. Finally, the opening of the battery can was closed with a battery lid with insulating packing on the periphery. Thus, a cylindrical lithium ion secondary battery was completed.

  The capacity retention rate after 500 cycles of charge / discharge of the obtained battery was evaluated by the above method. The results are shown in Table 1. Table 1 shows the difference between the solubility parameter (SP value) of the positive electrode binders (copolymers A to E), the solubility parameter of the nonaqueous solvent, and the solubility parameter of the positive electrode binder.

<< Reference Example 2 >>
(A) Production of positive electrode 100 parts by weight of lithium cobaltate and 4 parts by weight of polyvinylidene fluoride (PVdF) (PVdF component of “# 1320 (trade name)” manufactured by Kureha Chemical Co., Ltd.) as a positive electrode binder Then, 3 parts by weight of acetylene black and an appropriate amount of NMP were stirred with a double-arm kneader to prepare a positive electrode mixture slurry. This slurry was applied to both surfaces of a 15 μm-thick aluminum foil as a positive electrode core material, dried and then roll-pressed to form a positive electrode mixture layer having a density of 3.3 g / cm ³ . Under the present circumstances, the thickness of the electrode plate which consists of aluminum foil and a positive mix layer was controlled to 160 micrometers. Thereafter, the electrode plate was slit to a width that could be inserted into a can battery case of a cylindrical battery (Part No. 18650) to obtain a positive electrode hoop.

(B) Production of negative electrode 100 parts by weight of artificial graphite, 3 parts by weight of acrylonitrile copolymer as a negative electrode binder, and an appropriate amount of electrode dispersion medium were stirred with a double-arm kneader, and a non-volatile component A negative electrode mixture slurry having a content of 70 wt% was prepared. This slurry was applied to both sides of a 10 μm-thick copper foil as a negative electrode core, and dried at 120 ° C. Thereafter, the dried coating film was roll-pressed to form a negative electrode mixture layer having a density of 1.4 g / cm ³ . Under the present circumstances, the thickness of the electrode plate which consists of copper foil and a negative mix layer was controlled to 180 micrometers. Next, the electrode plate was slit to a width that could be inserted into a can battery case of a cylindrical battery (Part No. 18650) to obtain a negative electrode hoop.

  As the negative electrode binder, copolymers A to B containing the same acrylonitrile unit (unit), dodecyl acrylate unit, and butadiene monooxide unit as used for the positive electrode binder in Reference Example 1 and having different solubility parameters. E was used.

  As the negative electrode dispersion medium, a negative electrode dispersion medium having a solubility parameter that is the same as or close to the solubility parameter of the negative electrode binder (acrylonitrile copolymer) contained in the negative electrode mixture slurry was used. These are the same as those used in Reference Example 1.

(C) Production of Battery A cylindrical lithium ion secondary battery was completed in the same manner as in Reference Example 1 except that the above positive electrode and negative electrode were used.

  The capacity retention rate after 500 cycles of charge / discharge of the obtained battery was evaluated by the above method. The results are shown in Table 2. Table 2 shows the difference between the solubility parameter (SP value) of the negative electrode binders (copolymers A to E), the solubility parameter of the nonaqueous solvent, and the solubility parameter of the negative electrode binder.

<< Reference Example 3 >>
A cylindrical lithium ion secondary battery was completed in the same manner as Reference Example 1 except that the negative electrode of Reference Example 2 was used. The capacity retention rate after 500 cycles of charge / discharge of the obtained battery was evaluated by the above method. The results are shown in Table 3.

<< Reference Example 4 >>
As the positive electrode binder, a one-part thermally crosslinked acrylonitrile copolymer containing a sulfonic acid group as a hydrophilic group having a high degree of dissociation was used in place of the acrylonitrile copolymer. The one-part thermally crosslinked acrylonitrile copolymer used here has a masked crosslinking point, and contains an acrylonitrile unit, a dodecyl acrylate unit, and a butadiene monooxide unit, and has a weight average molecular weight of 239000. there were. Even when this one-component thermally crosslinked acrylonitrile copolymer was allowed to stand at 40 ° C. for 72 hours, the crosslinking reaction proceeded only at 5% by weight or less. Further, a non-aqueous electrolyte solution (a mixture containing EC, DMC, and DEC at a volume ratio of 4: 4: 2) obtained by heating a one-component heat-crosslinked acrylonitrile copolymer at 170 ° C. for 24 hours. The solubility in a non-aqueous electrolyte solution in which LiPF ₆ was dissolved in a solvent at a concentration of 1 mol / L and 3% by weight of vinylene carbonate (VC) was further added was 5% by weight or less.

A positive electrode mixture having a density of 3.3 g / cm ^{3 on} the positive electrode core material in the same manner as in Reference Example 1 except that the one-component thermally cross-linked acrylonitrile copolymer having a masked cross-linking point was used. A layer was formed. Thereafter, in the nitrogen gas atmosphere, the positive electrode mixture layer was heated at 170 ° C. for 24 hours to crosslink the one-component thermally crosslinked acrylonitrile copolymer.

  A cylindrical lithium ion secondary battery was completed in the same manner as in Reference Example 1 except that the positive electrode was used. The capacity retention rate after 500 cycles of charge / discharge of the obtained battery was evaluated by the above method. The results are shown in Table 4. Table 4 shows solubility parameters of the positive electrode binder used here.

<< Reference Example 5 >>
As a positive electrode binder, a positive electrode mixture slurry was prepared using a polyacrylonitrile derivative containing an unmasked hydroxyl group instead of the one-component thermally crosslinked acrylonitrile copolymer. To the positive electrode mixture slurry, 20 parts by weight of polyisocyanate having an isocyanate group (—NCO) at the terminal as a crosslinking agent for the polyacrylonitrile derivative was added per 100 parts by weight of the polyacrylonitrile derivative.
When a mixture of 100 parts by weight of a polyacrylonitrile derivative containing an unmasked hydroxyl group and 20 parts by weight of a polyisocyanate having an isocyanate group at the end was left at 40 ° C. for 72 hours, it exceeded 5% by weight of the mixture. The amount of crosslinking reaction proceeded.

  A cylindrical lithium ion secondary battery was completed in the same manner as in Reference Example 4 except that this positive electrode mixture slurry was used. That is, here, the positive electrode mixture layer was heated at 170 ° C. for 24 hours in a nitrogen gas atmosphere to crosslink the polyacrylonitrile derivative. The capacity retention rate after 500 cycles of charge / discharge of the obtained battery was evaluated by the above method. The results are shown in Table 4. Table 4 shows solubility parameters of the positive electrode binder used here.

Example 1
(A) Preparation of porous film paste 100 parts by weight of α-alumina “AKP50 (trade name)” having a median diameter of 0.3 μm manufactured by Sumitomo Chemical Co., Ltd. as an inorganic filler and acrylonitrile as a film binder 4 parts by weight of the polymer and an appropriate amount of the membrane dispersion medium were stirred for 30 minutes with a dissolver as a preliminary stirrer. The obtained pre-stirred product was further stirred with a bead mill (KDC-PAILOT-A type, manufactured by Shinmaru Enterprise Co., Ltd.) with an internal volume of 2 liters, and the residence time was set to 10 minutes. A porous film paste was prepared. The bead mill incorporates a disk-shaped disk, and the contents of the mill are stirred by the rotation of the disk. The residence time is defined by a value obtained by dividing the internal volume of the mill by the flow rate of the pre-stirred material fed into the mill and corresponds to the dispersion processing time.

  As the membrane binder, a copolymer A to A containing the same acrylonitrile unit (unit), dodecyl acrylate unit, and butadiene monooxide unit as used as the positive electrode binder in Reference Example 1 and having different solubility parameters. E was used.

  As the membrane dispersion medium, a membrane dispersion medium having a solubility parameter that is the same as or close to the solubility parameter of the membrane binder (acrylonitrile copolymer) contained in the porous membrane paste was used. These are the same as those used as the positive electrode dispersion medium in Reference Example 1.

(B) Formation of porous film A negative electrode similar to that of Reference Example 1 was prepared, and the above porous film paste was applied to the surface of the negative electrode mixture layer, dried at 120 ° C., and dried to a thickness of 10 μm adhered to the negative electrode. A coating film was obtained.

(C) Production of Battery Reference Example, except that the negative electrode having the above porous film adhered to the surface and the same positive electrode as Reference Example 2 were used, and a polyethylene resin microporous sheet having a thickness of 10 μm was used as a separator. In the same manner as in Example 1, a cylindrical lithium ion secondary battery was completed.

  The capacity retention rate after 500 cycles of charge / discharge of the obtained battery was evaluated by the above method. The results are shown in Table 5. Table 5 shows the difference between the solubility parameter (SP value) of the membrane binder (copolymers A to E), the solubility parameter of the nonaqueous solvent, and the solubility parameter of the membrane binder.

Example 2
As the membrane binder, a one-component thermally crosslinked acrylonitrile copolymer containing a sulfonic acid group as a hydrophilic group having a high degree of dissociation was used instead of the acrylonitrile copolymer described above. The one-part thermally crosslinked acrylonitrile copolymer used here has a masked crosslinking point, and contains an acrylonitrile unit, a dodecyl acrylate unit, and a butadiene monooxide unit, and has a weight average molecular weight of 239000. there were. Even when this one-component thermally crosslinked acrylonitrile copolymer was allowed to stand at 40 ° C. for 72 hours, the crosslinking reaction proceeded only at 5% by weight or less. Further, the solubility of the cured product obtained by heating the one-component heat-crosslinked acrylonitrile copolymer at 170 ° C. for 24 hours in a predetermined nonaqueous electrolytic solution was 5% by weight or less.

  A porous film paste was prepared in the same manner as in Example 1 except that the one-component thermally crosslinked acrylonitrile copolymer having the above-mentioned masked crosslinking points was used, and this was used as in Example 1. Thus, a porous film was formed on the negative electrode mixture layer. Thereafter, the negative electrode was heated in a nitrogen gas atmosphere at 170 ° C. for 24 hours to crosslink the acrylonitrile copolymer.

  A cylindrical lithium ion secondary battery was completed in the same manner as in Example 1 except that the porous film was formed. The capacity retention rate after 500 cycles of charge / discharge of the obtained battery was evaluated by the above method. The results are shown in Table 6. Table 6 shows solubility parameters of the membrane binder used here.

Example 3
As a film binder, a porous film paste was prepared using a polyacrylonitrile derivative containing an unmasked hydroxyl group in place of the one-component thermally crosslinked acrylonitrile copolymer. To the porous film paste, 20 parts by weight of polyisocyanate having an isocyanate group (—NCO) at the terminal was added as a crosslinking agent for the polyacrylonitrile derivative per 100 parts by weight of the polyacrylonitrile derivative.
When a mixture of 100 parts by weight of a polyacrylonitrile derivative containing an unmasked hydroxyl group and 20 parts by weight of a polyisocyanate having an isocyanate group at the end was left at 40 ° C. for 72 hours, it exceeded 5% by weight of the mixture. The amount of crosslinking reaction proceeded.

  A cylindrical lithium ion secondary battery was completed in the same manner as in Example 2 except that this porous film paste was used. That is, here, after the coating film of the porous film paste on the negative electrode mixture layer was dried, the negative electrode was heated in a nitrogen gas atmosphere at 170 ° C. for 24 hours to crosslink the polyacrylonitrile derivative. The capacity retention rate after 500 cycles of charge / discharge of the obtained battery was evaluated by the above method. The results are shown in Table 6. Table 6 shows solubility parameters of the membrane binder used here.

The solubility parameter of the non-aqueous solvent of the non-aqueous electrolyte is 11.6.
The difference between the solubility parameter of the nonaqueous solvent of the nonaqueous electrolyte and the solubility parameter of acrylonitrile copolymer A (the solubility parameter of NMP) is 0.3.
The difference between the solubility parameter of the non-aqueous solvent of the non-aqueous electrolyte and the solubility parameter of acrylonitrile copolymer B is 0.8.
The difference between the solubility parameter of the non-aqueous solvent of the non-aqueous electrolyte and the solubility parameter of the acrylonitrile copolymer C is 1.3.
The difference between the solubility parameter of the nonaqueous solvent of the nonaqueous electrolyte and the solubility parameter of the acrylonitrile copolymer D is 1.8.
The difference between the solubility parameter of the non-aqueous solvent of the non-aqueous electrolyte and the solubility parameter of the acrylonitrile copolymer E is 2.3.

  As described above, the difference in solubility parameter between the acrylonitrile copolymers C to D and the nonaqueous solvent of the nonaqueous electrolytic solution exceeds 1.0. Therefore, when acrylonitrile copolymers C to D are used for the membrane binder, as shown in Tables 1 to 3 and Table 5, the capacity retention rate after 500 cycles of charge and discharge are all It is good. Further, when a one-component heat-crosslinked acrylonitrile copolymer having a solubility parameter of 9.8 as in the case of acrylonitrile copolymer D is used, an even better capacity retention rate is obtained.

  On the other hand, the difference in solubility parameter between the acrylonitrile copolymers A and B and the nonaqueous solvent of the nonaqueous electrolytic solution is less than 1.0. Therefore, when acrylonitrile copolymers A and B are used for the membrane binder, as shown in Tables 1 to 3 and Table 5, the capacity retention rate after 500 cycles of charge and discharge are all It is insufficient.

  As described above, according to the present invention, it is possible to obtain a lithium ion secondary battery in which capacity deterioration due to repetition of charge / discharge cycles is suppressed.

It is a longitudinal cross-sectional view of an example of a cylindrical lithium ion secondary battery.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery can 2 Battery cover 3 Insulation packing 5 Positive electrode 5a Positive electrode lead 6 Negative electrode 6a Negative electrode lead 7 Separator 8a Upper insulating ring 8b Lower insulating ring

Claims (10)

A positive electrode comprising a positive electrode core material and a positive electrode mixture layer carried on the positive electrode core material;
A negative electrode comprising a negative electrode core material and a negative electrode mixture layer carried on the negative electrode core material;
Separator,
A non-aqueous electrolyte containing a non-aqueous solvent containing a carbonate and a solute that dissolves in the non-aqueous solvent, and a porous film adhered to at least one surface of the positive electrode and the negative electrode,
The porous membrane includes an inorganic filler and a membrane binder;
The lithium ion secondary battery in which the solubility parameter of the membrane binder is different from the solubility parameter of the non-aqueous solvent by one or more.   The lithium ion secondary battery according to claim 1, wherein the film binder includes a cured product of a heat crosslinkable resin.   The lithium ion secondary battery according to claim 2, wherein the thermally crosslinkable resin is a one-pack type.   The lithium ion secondary battery according to claim 1 whose solubility parameter of the nonaqueous solvent containing said carbonate is 11.5-14. A step of preparing an electrode mixture slurry by mixing an electrode mixture containing an electrode active material and an electrode binder with an electrode dispersion medium;
Applying the electrode mixture slurry to an electrode core material and drying the applied slurry to form an electrode mixture layer;
Dissolving a solute in a non-aqueous solvent containing a carbonate to prepare a non-aqueous electrolyte,
A step of preparing a porous film paste by mixing a film mixture containing an inorganic filler and a film binder with a film dispersion medium;
The step of applying the porous film paste to the surface of the electrode mixture layer, drying the applied paste to form a porous film, and the electrode having the porous film and the nonaqueous electrolytic solution. Using the process of assembling the battery,
A method for producing a lithium ion secondary battery, wherein the solubility parameter of the membrane binder is at least one different from the solubility parameter of the non-aqueous solvent.   The method for producing a lithium ion secondary battery according to claim 5, wherein the membrane binder contains a heat-crosslinking resin.   The method for producing a lithium ion secondary battery according to claim 6, wherein the thermally crosslinkable resin is a one-pack type.   The manufacturing method of the lithium ion secondary battery of Claim 5 whose solubility parameter of the nonaqueous solvent containing the said carbonate ester is 11.5-14.   The method for producing a lithium ion secondary battery according to claim 5, wherein the solubility parameter of the electrode dispersion medium is one or more different from the solubility parameter of the non-aqueous solvent.   The method for producing a lithium ion secondary battery according to claim 5, wherein the solubility parameter of the dispersion medium for a film differs from the solubility parameter of the nonaqueous solvent by one or more.

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