JP2010067435A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery capable of improving discharge capacity maintenance rate even under high-rate conditions and low temperature conditions. <P>SOLUTION: The nonaqueous electrolyte secondary battery is provided which includes a positive electrode, a negative electrode, a separator arranged between the positive electrode and the negative electrode, and a nonaqueous electrolytic solution, and in which the negative electrode has a negative electrode active material containing amorphous carbon material, and the separator is composed of a laminate film in which a heat resistant porous layer and a porous film are laminated. The nonaqueous electrolyte secondary battery is provided in which the heat resistant porous layer in the laminate film is arranged on the negative electrode side. The nonaqueous electrolyte secondary battery is provided in which the heat resistant porous layer contains a heat resistant resin. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery.

  A nonaqueous electrolyte secondary battery is a secondary battery in which a separator is disposed between a positive electrode, a negative electrode, and the positive electrode and the negative electrode. A typical lithium secondary battery as a nonaqueous electrolyte secondary battery has already been It has been put into practical use as a power source for mobile phones, notebook computers, etc., and is also being applied to medium and large applications such as automobile applications and power storage applications.

  As a conventional non-aqueous electrolyte secondary battery, Patent Document 1 describes using a non-graphitizable carbon material as a negative electrode and a polyethylene or polypropylene porous film as a separator.

JP 2006-147288 A

  However, in the above-mentioned non-aqueous electrolyte secondary battery, it is difficult to say that the discharge capacity maintenance rate when the charge / discharge cycle is repeated many times under high-rate conditions or low-temperature conditions, and there is still room for improvement. is there. An object of the present invention is to provide a non-aqueous electrolyte secondary battery capable of improving the discharge capacity retention rate even under high-rate conditions and low-temperature conditions.

The inventors of the present invention have intensively studied to solve the above-mentioned problems and have arrived at the present invention. That is, the present invention provides the following inventions.
<1> a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, the negative electrode having a negative electrode active material containing an amorphous carbon material, A non-aqueous electrolyte secondary battery, wherein the separator comprises a laminated film in which a heat-resistant porous layer and a porous film are laminated.
<2> The nonaqueous electrolyte secondary battery according to <1>, wherein the heat-resistant porous layer in the laminated film is disposed on the negative electrode side.
<3> The nonaqueous electrolyte secondary battery according to <1> or <2>, wherein the heat resistant porous layer is a heat resistant porous layer containing a heat resistant resin.
<4> The nonaqueous electrolyte secondary battery according to <3>, wherein the heat-resistant resin is a nitrogen-containing aromatic polymer.
<5> The nonaqueous electrolyte secondary battery according to <3> or <4>, wherein the heat resistant resin is an aromatic polyamide.
<6> The nonaqueous electrolyte secondary battery according to any one of <3> to <5>, wherein the heat-resistant porous layer further contains a filler.
<7> The nonaqueous electrolyte secondary battery according to <6>, wherein the weight of the filler is 20 or more and 95 or less when the total weight of the heat resistant porous layer is 100.
<8> The nonaqueous electrolyte secondary battery according to any one of <1> to <7>, wherein the heat-resistant porous layer has a thickness of 1 μm to 10 μm.

  According to the present invention, it is possible to provide a nonaqueous electrolyte secondary battery in which the discharge capacity retention rate is improved when the charge / discharge cycle is repeated many times under a high rate condition or a low temperature condition. The battery is a secondary battery having extremely excellent heat resistance, and is extremely useful industrially.

  The non-aqueous electrolyte secondary battery of the present invention includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, and the negative electrode includes an amorphous carbon material. It has a negative electrode active material, and this separator consists of a laminated | multilayer film by which the heat resistant porous layer and the porous film were laminated | stacked.

  First, the separator in the present invention will be described. The separator in the present invention comprises a laminated film in which a heat resistant porous layer and a porous film are laminated. From the viewpoint of ion permeability, the separator preferably has an air permeability of 50 to 300 seconds / 100 cc, more preferably 50 to 200 seconds / 100 cc, as measured by the Gurley method. Moreover, the porosity of a separator is 30-80 volume% normally, Preferably it is 40-70 volume%. The thickness of the separator is preferably about 5 to 200 μm, and preferably about 5 to 40 μm, as long as the mechanical strength is maintained because the volume energy density of the battery is increased and the internal resistance is reduced.

  In the laminated film, the heat resistant porous layer is a layer having higher heat resistance than the porous film, and the heat resistant porous layer may be formed of an inorganic powder or may contain a heat resistant resin. When the heat resistant porous layer contains a heat resistant resin, the heat resistant porous layer can be formed by an easy technique such as coating. Examples of the heat resistant resin include polyamide, polyimide, polyamideimide, polycarbonate, polyacetal, polysulfone, polyphenylene sulfide, polyether ketone, aromatic polyester, polyether sulfone, and polyetherimide. Preferred heat resistant resins are polyamide, Polyimide, polyamideimide, polyethersulfone, and polyetherimide are preferable, and polyamide, polyimide, and polyamideimide are more preferable heat resistant resins. Even more preferred heat resistant resins are nitrogen-containing aromatic polymers such as aromatic polyamides (para-oriented aromatic polyamides, meta-oriented aromatic polyamides), aromatic polyimides, aromatic polyamideimides, and particularly preferred heat resistant resins are aromatic. From the viewpoint of being a polyamide and easily usable, a particularly preferred heat resistant resin is a para-oriented aromatic polyamide (hereinafter sometimes referred to as “para-aramid”). Further, examples of the heat resistant resin include poly-4-methylpentene-1 and cyclic olefin polymers. By using these heat resistant resins, the heat resistance of the laminated film, that is, the thermal film breaking temperature of the laminated film is further increased. Among these heat-resistant resins, when using a nitrogen-containing aromatic polymer, because of the polarity in the molecule, compatibility with the electrolyte, that is, the liquid retention in the heat-resistant porous layer may be improved, The rate of impregnation of the electrolytic solution during the production of the nonaqueous electrolyte secondary battery is also high, and the charge / discharge capacity of the nonaqueous electrolyte secondary battery is further increased.

  The thermal film breaking temperature of such a laminated film depends on the type of heat-resistant resin, and is selected and used according to the use scene and purpose of use. More specifically, as the heat resistant resin, the cyclic olefin polymer is used at about 400 ° C. when the nitrogen-containing aromatic polymer is used, and at about 250 ° C. when poly-4-methylpentene-1 is used. When using, the thermal film breaking temperature can be controlled to about 300 ° C., respectively. Moreover, when the heat resistant porous layer is made of an inorganic powder, the thermal film breaking temperature can be controlled to, for example, 500 ° C. or higher.

  The para-aramid is obtained by condensation polymerization of a para-oriented aromatic diamine and a para-oriented aromatic dicarboxylic acid halide, and the amide bond is in the para position of the aromatic ring or an oriented position equivalent thereto (for example, 4,4′- It consists essentially of repeating units bonded at opposite orientations, such as biphenylene, 1,5-naphthalene, 2,6-naphthalene, etc., oriented in the opposite direction coaxially or in parallel. Specifically, poly (paraphenylene terephthalamide), poly (parabenzamide), poly (4,4′-benzanilide terephthalamide), poly (paraphenylene-4,4′-biphenylenedicarboxylic acid amide), poly ( Para-aligned or para-oriented such as paraphenylene-2,6-naphthalenedicarboxylic acid amide), poly (2-chloro-paraphenylene terephthalamide), paraphenylene terephthalamide / 2,6-dichloroparaphenylene terephthalamide copolymer Examples include para-aramid having a structure according to the type.

  The aromatic polyimide is preferably a wholly aromatic polyimide produced by condensation polymerization of an aromatic dianhydride and a diamine. Specific examples of the dianhydride include pyromellitic dianhydride, 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic Examples thereof include acid dianhydride, 2,2′-bis (3,4-dicarboxyphenyl) hexafluoropropane, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, and the like. Specific examples of the diamine include oxydianiline, paraphenylenediamine, benzophenonediamine, 3,3′-methylenedianiline, 3,3′-diaminobenzophenone, 3,3′-diaminodiphenylsulfone, 1,5 '-Naphthalenediamine and the like. Moreover, a polyimide soluble in a solvent can be preferably used. An example of such a polyimide is a polycondensate polyimide of 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride and an aromatic diamine.

  As the above-mentioned aromatic polyamideimide, those obtained from condensation polymerization using aromatic dicarboxylic acid and aromatic diisocyanate, those obtained from condensation polymerization using aromatic diacid anhydride and aromatic diisocyanate Is mentioned. Specific examples of the aromatic dicarboxylic acid include isophthalic acid and terephthalic acid. Specific examples of the aromatic dianhydride include trimellitic anhydride. Specific examples of the aromatic diisocyanate include 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, orthotolylane diisocyanate, m-xylene diisocyanate, and the like.

  In order to further enhance the ion permeability, the heat-resistant porous layer is preferably a thin heat-resistant porous layer having a thickness of 1 μm to 10 μm, more preferably 1 μm to 5 μm, particularly 1 μm to 4 μm. The heat-resistant porous layer has fine pores, and the size (diameter) of the pores is usually 3 μm or less, preferably 1 μm or less.

  In addition, when the heat resistant porous layer contains a heat resistant resin, it can further contain a filler. The filler may be selected from organic powder, inorganic powder, or a mixture thereof as the material thereof. The particles constituting the filler preferably have an average particle size of 0.01 μm or more and 1 μm or less.

  Examples of the organic powder include styrene, vinyl ketone, acrylonitrile, methyl methacrylate, ethyl methacrylate, glycidyl methacrylate, glycidyl acrylate, and methyl acrylate, or a copolymer of two or more kinds, polytetrafluoroethylene, 4 fluorine. Examples include fluorine-containing resins such as fluorinated ethylene-6-propylene-propylene copolymer, tetrafluoroethylene-ethylene copolymer, and polyvinylidene fluoride; melamine resin; urea resin; polyolefin; and powders made of organic substances such as polymethacrylate. . The organic powder may be used alone or in combination of two or more. Among these organic powders, polytetrafluoroethylene powder is preferable from the viewpoint of chemical stability.

  Examples of the inorganic powder include powders made of inorganic substances such as metal oxides, metal nitrides, metal carbides, metal hydroxides, carbonates, sulfates, etc. Among these, they are made of inorganic substances having low conductivity. Powder is preferably used. Specific examples include powders made of alumina, silica, titanium dioxide, calcium carbonate, or the like. The inorganic powder may be used alone or in combination of two or more. Among these inorganic powders, alumina powder is preferable from the viewpoint of chemical stability. Here, it is more preferable that all of the particles constituting the filler are alumina particles, and it is even more preferable that all of the particles constituting the filler are alumina particles, and part or all of them are substantially spherical alumina particles. It is embodiment which is. Incidentally, when the heat-resistant porous layer is formed from an inorganic powder, the inorganic powder exemplified above may be used, and may be mixed with a binder as necessary.

  When the heat-resistant porous layer contains a heat-resistant resin, the filler content depends on the specific gravity of the filler material. For example, when the total weight of the heat-resistant porous layer is 100, the filler weight is usually 5 It is 95 or more and it is preferable that it is 20 or more and 95 or less, More preferably, it is 30 or more and 90 or less. These ranges are particularly suitable when all of the particles constituting the filler are alumina particles.

  Examples of the shape of the filler include a substantially spherical shape, a plate shape, a columnar shape, a needle shape, a whisker shape, and a fibrous shape, and any particle can be used. It is preferable that Examples of the substantially spherical particles include particles having a particle aspect ratio (particle major axis / particle minor axis) in the range of 1 to 1.5. The aspect ratio of the particles can be measured by an electron micrograph.

  In the laminated film, the porous film has fine pores and usually has a shutdown function. The size (diameter) of the micropores in the porous film is usually 3 μm or less, preferably 1 μm or less. The porosity of the porous film is usually 30 to 80% by volume, preferably 40 to 70% by volume. In the nonaqueous electrolyte secondary battery, when the normal use temperature is exceeded, the micropores can be blocked by the deformation and softening of the porous film by the shutdown function.

  In the laminated film, the resin constituting the porous film may be selected from those that do not dissolve in the electrolyte solution in the nonaqueous electrolyte secondary battery. Specific examples include polyolefin resins such as polyethylene and polypropylene, and thermoplastic polyurethane resins, and a mixture of two or more of these may be used. In terms of softening and shutting down at a lower temperature, the porous film preferably contains a polyolefin resin, and more preferably contains polyethylene. Specific examples of polyethylene include polyethylene such as low density polyethylene, high density polyethylene, and linear polyethylene, and also include ultrahigh molecular weight polyethylene. In the sense of further increasing the puncture strength of the porous film, the resin constituting it preferably contains at least ultra high molecular weight polyethylene. Moreover, it may be preferable to contain the wax which consists of polyolefin of a low molecular weight (weight average molecular weight 10,000 or less) in the manufacture surface of a porous film.

  Moreover, the thickness of the porous film in a laminated | multilayer film is 3-30 micrometers normally, Preferably it is 3-25 micrometers. Moreover, as thickness of a laminated film, it is 40 micrometers or less normally, Preferably, it is 20 micrometers or less. Moreover, when the thickness of the heat resistant porous layer is A (μm) and the thickness of the porous film is B (μm), the value of A / B is preferably 0.1 or more and 1 or less.

Next, an example of manufacturing a laminated film will be described.
First, the manufacturing method of a porous film is demonstrated. The production of the porous film is not particularly limited. For example, as described in JP-A-7-29563, a plasticizer is added to a thermoplastic resin to form a film, and then the plasticizer is mixed with an appropriate solvent. As described in JP-A-7-304110, a film made of a thermoplastic resin produced by a known method is used, and a structurally weak amorphous portion of the film is selectively stretched. And a method of forming micropores. For example, when the porous film is formed from a polyolefin resin containing ultrahigh molecular weight polyethylene and a low molecular weight polyolefin having a weight average molecular weight of 10,000 or less, it is produced by the following method from the viewpoint of production cost. It is preferable. That is,
(1) A step of kneading 100 parts by weight of ultrahigh molecular weight polyethylene, 5 to 200 parts by weight of a low molecular weight polyolefin having a weight average molecular weight of 10,000 or less, and 100 to 400 parts by weight of an inorganic filler to obtain a polyolefin resin composition ( 2) Step of forming a sheet using the polyolefin resin composition (3) Step of removing inorganic filler from the sheet obtained in step (2) (4) Stretching of the sheet obtained in step (3) Or a method comprising a step of obtaining a porous film, or (1) 100 parts by weight of ultrahigh molecular weight polyethylene, 5 to 200 parts by weight of a low molecular weight polyolefin having a weight average molecular weight of 10,000 or less, and 100 to 400 parts by weight of an inorganic filler And a step of obtaining a polyolefin resin composition by kneading (2) a step of molding a sheet using the polyolefin resin composition (3) obtained in step (2) From in stretched sheet obtained in the step of stretching the sheet (4) Step (3), the method comprising the step of removing the inorganic filler to obtain a porous film.

  From the viewpoint of the strength and ion permeability of the porous film, the inorganic filler used preferably has an average particle diameter (diameter) of 0.5 μm or less, more preferably 0.2 μm or less. Here, the value measured from an electron micrograph is used for the average particle diameter. Specifically, 50 particles are arbitrarily extracted from the inorganic filler particles photographed in the photograph, the particle diameter is measured, and the average value is used.

  Inorganic fillers include calcium carbonate, magnesium carbonate, barium carbonate, zinc oxide, calcium oxide, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, calcium sulfate, silicic acid, zinc oxide, calcium chloride, sodium chloride, magnesium sulfate, etc. Is mentioned. These inorganic fillers can be removed from the sheet or film with an acid or alkaline solution. Calcium carbonate is preferably used from the viewpoints of particle size controllability and selective solubility in acid.

  The method for producing the polyolefin resin composition is not particularly limited, but a mixing device, such as a roll, a Banbury mixer, a single screw extruder, a twin screw extruder, or the like, is used to mix materials constituting the polyolefin resin composition such as polyolefin resin and inorganic filler. And mixed to obtain a polyolefin resin composition. When mixing the materials, additives such as fatty acid esters, stabilizers, antioxidants, ultraviolet absorbers and flame retardants may be added as necessary.

  The manufacturing method of the sheet | seat which consists of the said polyolefin resin composition is not specifically limited, It can manufacture by sheet | seat shaping | molding methods, such as an inflation process, a calendar process, T-die extrusion process, and a Skyf method. Since a sheet with higher film thickness accuracy can be obtained, it is preferable to produce the sheet by the following method.

  A preferred method for producing a sheet comprising a polyolefin resin composition is a method of rolling a polyolefin resin composition using a pair of rotational molding tools adjusted to a surface temperature higher than the melting point of the polyolefin resin contained in the polyolefin resin composition. It is a method to do. The surface temperature of the rotary forming tool is preferably (melting point + 5) ° C. or higher. The upper limit of the surface temperature is preferably (melting point + 30) ° C. or less, and more preferably (melting point + 20) ° C. or less. Examples of the pair of rotary forming tools include a roll and a belt. The peripheral speeds of the two rotary forming tools do not necessarily have to be exactly the same peripheral speed, and the difference between them may be about ± 5% or less. By producing a porous film using a sheet obtained by such a method, a porous film excellent in strength, ion permeation, air permeability and the like can be obtained. Moreover, you may use what laminated | stacked the sheet | seat of the single layer obtained by the above methods for manufacture of a porous film.

  When the polyolefin resin composition is roll-formed with a pair of rotary molding tools, the polyolefin resin composition discharged in a strand form from an extruder may be directly introduced between the pair of rotary molding tools, and once pelletized polyolefin A resin composition may be used.

  When stretching a sheet made of a polyolefin resin composition or a sheet from which the inorganic filler has been removed, a tenter, a roll, an autograph or the like can be used. From the air permeable side, the draw ratio is preferably 2 to 12 times, more preferably 4 to 10 times. The stretching temperature is usually carried out at a temperature not lower than the softening point of the polyolefin resin and not higher than the melting point, preferably 80 to 115 ° C. If the stretching temperature is too low, film breakage tends to occur during stretching, and if it is too high, the air permeability and ion permeability of the resulting porous film may be lowered. Moreover, it is preferable to heat set after extending | stretching. The heat set temperature is preferably a temperature below the melting point of the polyolefin resin.

  In the present invention, a porous film containing a thermoplastic resin obtained by the method as described above and a heat-resistant porous layer are laminated to obtain a laminated film. The heat resistant porous layer may be provided on one side of the porous film or may be provided on both sides.

As a method of laminating a porous film and a heat-resistant porous layer, a method of separately producing a heat-resistant porous layer and a porous film and laminating each of them, and containing a heat-resistant resin and a filler on at least one surface of the porous film Examples of the method include forming a heat-resistant porous layer by applying a coating liquid to be applied. In the present invention, when the heat-resistant porous layer is relatively thin, the latter method is preferable from the viewpoint of productivity. Specific examples of a method for forming a heat resistant resin layer by applying a coating solution containing a heat resistant resin and a filler to at least one surface of the porous film include the following steps.
(A) A slurry-like coating liquid is prepared by dispersing 1 to 1500 parts by weight of a filler in 100 parts by weight of a heat resistant resin in a polar organic solvent solution containing 100 parts by weight of a heat resistant resin.
(B) The coating solution is applied to at least one surface of the porous film to form a coating film.
(C) The heat resistant resin is deposited from the coating film by means of humidification, solvent removal, or immersion in a solvent that does not dissolve the heat resistant resin, and then dried as necessary.
The coating liquid is preferably applied continuously by a coating apparatus described in JP-A-2001-316006 and a method described in JP-A-2001-23602.

  When the heat resistant resin is para-aramid in the polar organic solvent solution, a polar amide solvent or a polar urea solvent can be used as the polar organic solvent. Specifically, N, N— Examples include, but are not limited to, dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone (NMP), and tetramethylurea.

  When para-aramid is used as the heat-resistant resin, it is preferable to add an alkali metal or alkaline earth metal chloride during para-aramid polymerization for the purpose of improving the solubility of para-aramid in a solvent. Specific examples include lithium chloride or calcium chloride, but are not limited thereto. The amount of the chloride added to the polymerization system is preferably in the range of 0.5 to 6.0 mol, more preferably in the range of 1.0 to 4.0 mol, per 1.0 mol of the amide group produced by condensation polymerization. . If the chloride is less than 0.5 mol, the solubility of the resulting para-aramid may be insufficient, and if it exceeds 6.0 mol, the solubility of the chloride in the solvent may be substantially exceeded, which may be undesirable. . In general, if the alkali metal or alkaline earth metal chloride is less than 2% by weight, the solubility of para-aramid may be insufficient. If it exceeds 10% by weight, the alkali metal or alkaline earth metal chloride may be insufficient. May not dissolve in polar organic solvents such as polar amide solvents or polar urea solvents.

  Further, when the heat resistant resin is an aromatic polyimide, the polar organic solvent for dissolving the aromatic polyimide includes those exemplified as the solvent for dissolving the aramid, dimethyl sulfoxide, cresol, o-chlorophenol, etc. Can be suitably used.

  As a method for obtaining a slurry-like coating liquid by dispersing a filler, a pressure disperser (gorin homogenizer, nanomizer) or the like may be used as the apparatus.

  Examples of the method of applying the slurry-like coating liquid include a coating method such as a knife, blade, bar, gravure, die, etc., and coating of a bar, knife, etc. is simple, but industrially, Die coating having a structure in which the solution does not come into contact with outside air is preferable. Moreover, coating may be performed twice or more. In this case, it is usual to carry out after depositing the heat-resistant resin in the step (c).

  In the case where the heat resistant porous layer and the porous film are separately manufactured and laminated, it is preferable to fix them by a method using an adhesive, a method using heat fusion, or the like.

  Next, the negative electrode in the present invention will be described. In the present invention, the negative electrode has a negative electrode active material containing an amorphous carbon material. In this invention, it can be set as the negative electrode which has a volume change little and has the outstanding high-rate characteristic by having the said negative electrode active material. As an amorphous carbon material, among carbon materials obtained by carbonizing an organic material, powder X-rays obtained by powder X-ray diffraction measurement (a measurement range of a surface interval is 0.3 nm or more and 1 nm or less). In the diffraction pattern, a carbon material that gives a broad diffraction peak (halo) in a range of 0.34 to 0.50 nm between planes may be used. Examples of the organic material include natural resources such as petroleum and coal, various synthetic resins synthesized from such resources, tar or pitch such as plant residue oil, or plant-derived organic materials such as wood, infusible organic The material etc. can be mentioned, These can be used individually or in mixture of 2 or more types.

  The amorphous carbon material in the present invention is preferably a carbon material obtained by carbonizing a synthetic resin, more preferably a thermosetting resin among the synthetic resins, and the thermosetting resin includes phenol. Examples thereof include a resin, a resorcinol resin, a furan resin, and an epoxy resin. Two or more of these thermosetting resins may be used. The thermosetting resin may contain a curing agent, an additive, and a crosslinking agent. Examples of the curing method include thermal curing, epoxy curing, and isocyanate curing in the case where a phenol resin is used. By carbonization of the thermosetting resin, an amorphous carbon material can be obtained with high yield, the environmental load is small, the manufacturing cost can be reduced, and the industrial utility value is higher.

  As the thermosetting resin, a phenol resin is preferable, and this resin is obtained by polymerizing phenol or a derivative thereof and an aldehyde compound. Phenolic resins are inexpensive among thermosetting resins and have a large industrial production amount, and a carbon material obtained by carbonizing this is preferable as an amorphous carbon material in the present invention.

  Examples of the phenol or derivative thereof include phenol, o-cresol, m-cresol, p-cresol, catechol, resorcinol, hydroquinone, xylenol, pyrogallol, bisphenol A, bisphenol F, p-phenylphenol, p-tert- Examples thereof include butylphenol, p-tert-octylphenol, α-naphthol, β-naphthol and the like, and these can be used alone or in combination of two or more.

  Examples of the aldehyde compound include formaldehyde, paraformaldehyde, trioxane, acetaldehyde, propionaldehyde, polyoxymethylene, chloral, furfural, glyoxal, n-butyraldehyde, caproaldehyde, allylaldehyde, benzaldehyde, crotonaldehyde, acrolein, tetraoxy Examples include methylene, phenylacetaldehyde, o-tolualdehyde, salicylaldehyde, and the like. These can be used alone or in combination of two or more.

  Although it does not specifically limit as a phenol resin, A resol type phenol resin, a novolak type phenol resin, etc. can be used. The resol type phenol resin can be obtained by polymerizing phenol or a derivative thereof and an aldehyde compound in the presence of a basic catalyst, and the novolac type phenol resin can be obtained by using phenol or a derivative thereof and an aldehyde compound as an acidic catalyst. It can be obtained by polymerizing in the presence.

  When a self-hardening resol type phenol resin is used, an acid or a curing agent may be added to the resol type phenol resin, or a novolac type phenol resin may be added to reduce the degree of curing. Moreover, you may add combining them.

  The novolak type phenol resin is a method in which phenol or a derivative thereof and an aldehyde compound are subjected to a condensation reaction at a normal pressure of 100 ° C. for several hours using a known organic acid and / or inorganic acid as a catalyst, followed by dehydration and unreacted monomer removal. A random novolak type in which the position of the methylene group is the same as the ortho-position and the para-position, and phenol or a derivative thereof and an aldehyde compound, such as zinc acetate, lead acetate, zinc naphthenate, etc. After the addition condensation reaction with a catalyst under weak acidity, the condensation reaction proceeds directly or with further addition of an acid catalyst while dehydrating, and if necessary, the step of removing unreacted substances. Many high ortho novolaks are known.

Commercially available phenolic resins can be used, for example,
Powdered phenol resin (manufactured by Gunei Chemical Co., Ltd., trade names: Resitop, PGA-4528, PGA-2473, PGA-4704, PGA-4504, manufactured by Sumitomo Bakelite Co., Ltd., trade names: Sumilite Resin PR-UFC-504, PR -EPN, PR-ACS-100, PR-ACS-150, PR-12687, PR-13355, PR-16382, PR-217, PR-310, PR-311, PR-50064, PR-50099, PR-50102 , PR-50252, PR-50395, PR-50590, PR-50590B, PR-50699, PR-50869, PR-51316, PR-51326B, PR-51350B, PR-51510, PR-51541B, PR-51794, PR -51820, PR-51939, P -53153, PR-53364, PR-53497, PR-53724, PR-53769, PR-53804, PR-54364, PR-54458A, PR-54545, PR-55170, PR-8000, PR-FTZ-1, PR -FTZ-15), flaky phenol resin (manufactured by Sumitomo Bakelite Co., Ltd., trade names: Sumilite Resin PR-12686R, PR-13349, PR-50235A, PR-51363F, PR-51494G, PR-51618G, PR-53194, PR-53195, PR-54869, PR-F-110, PR-F-143, PR-F-151F, PR-F-85G, PR-HF-3, PR-HF-6), liquid phenolic resin (Sumitomo) Bakelite Co., Ltd., trade name: Sumilite Resin PR-500 7, PR-50607B, PR-50702, PR-50781, PR-51138C, PR-51206, PR-51663, PR-51947A, PR-53123, PR-53338, PR-53365, PR-53717, PR-54135, PR-54313, PR-54562, PR-55345, PR-940, PR-9400, PR-967), novolak type liquid phenolic resin (manufactured by Sumitomo Bakelite Co., Ltd., trade names: Sumilite Resin PR-51629, PR-53093, PR-53473, PR-53522, PR-53546, PR-53800, PR-54438, PR-54540C, PR-55438), resol type liquid phenolic resin (manufactured by Gunei Chemical Co., Ltd., trade names: Resitop PL-4826, PL -2390, P L-4690, PL-3630, PL-4222, PL-4246, PL-2211, PL-3224, PL-4329, manufactured by Sumitomo Bakelite Co., Ltd., trade names: Sumilite Resin PR-50273, PR-51206, PR-51781 , PR-53056, PR-53311, PR-53416, PR-53570, PR-54387), finely divided phenol resin (trade name: Bell Pearl, R800, R700, R600, R200, R100, S830, S870) , S890, S895, S290, S190), spherical resin (manufactured by Gunei Chemical Co., Ltd., trade names: Marilyn GU-200, FM-010, FM-150, HF-008, HF-015, HF-075, HF) -300, HF-500, HF-1500), solid Fe Resin (manufactured by Gunei Chemical Co., Ltd., trade names: Resitop PS-2601, PS-2607, PS-2655, PS-2768, PS-2608, PS-4609, PSM-2222, PSK-2320, PS-6132) Etc. are exemplified.

  Moreover, examples of the infusible organic material include organic materials obtained by crosslinking the tar and pitch, and organic materials obtained by oxidizing the tar and pitch, which is a preferred embodiment.

  Examples of tar and pitch include various residual oils during the production of various petrochemical products such as ethylene. More specifically, there can be mentioned petroleum heavy oil composed of distillation residue oil, fluid catalytic cracking residue oil, hydrodesulfurized oil thereof, or mixed oil thereof. Petroleum or coal-based tar or pitch, such as coal tar produced during coal dry distillation, heavy components or pitch obtained by distilling off low-boiling components of coal tar, tar and pitch obtained by liquefaction of coal, and the like can be used. Two or more of these tars and pitches may be mixed and used. As the residual oil of the plant, a residual oil of a plant that produces an organic compound containing oxygen such as phenol is particularly preferable. By using a carbon material obtained by carbonization of tar or pitch such as plant residue oil, resources can be effectively used, and industrial utility value is higher.

  As the crosslinking agent for the crosslinking treatment, polyfunctional vinyl monomers such as divinylbenzene, trivinylbenzene, diallyl phthalate, ethylene glycol dimethacrylate, N, N-methylenebisacrylamide and the like that undergo a crosslinking reaction by radical reaction can be used. . Examples of radical initiators include α, α′-azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), lauroyl peroxide, cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, hydrogen peroxide, etc. Can be used.

As the method of oxidation treatment, an oxidizing gas such as air, O ₂ , O ₃ , NO ₂ , a mixed gas obtained by diluting these with nitrogen or the like, or an oxidizing liquid such as sulfuric acid, nitric acid or hydrogen peroxide water is used. And a method of oxidizing at a temperature of 50 to 400 ° C.

  In the carbonization of the organic material or the carbonization of the infusible organic material, the carbonization temperature is usually 800 ° C. or higher, and the carbonization atmosphere is preferably an inert gas atmosphere. Here, the infusibilization treatment can be performed by the above oxidation treatment method. Examples of the inert gas include nitrogen and argon. Carbonization may be performed under reduced pressure. For these infusibilization treatment and carbonization, for example, equipment such as a rotary kiln, roller hearth kiln, pusher kiln, multi-stage furnace, fluidized furnace, etc. may be used. The rotary kiln is general purpose.

  More specifically, when carbonizing the said thermosetting resin, it is preferable that the temperature of carbonization is 1000 degreeC-3000 degreeC. Moreover, when carbonizing the organic material which made these infusible using the said tar and pitch, it is preferable that the temperature of carbonization is a temperature of 800 to 1500 degreeC. However, it is preferable to use, as tar and pitch, residual oil from a plant that produces an organic compound containing oxygen such as phenol. When carbonizing this, the temperature of carbonization is a temperature of 1000 ° C to 3000 ° C. It is preferable.

Further, the amorphous carbon material obtained by carbonization may be pulverized as necessary. For pulverization, for example, an impact friction pulverizer, a centrifugal pulverizer, a ball mill (tube mill, compound mill, A pulverizer for fine pulverization such as a conical ball mill, a rod mill), a vibration mill, a colloid mill, a friction disk mill, or a jet mill is preferably used, and pulverization by a ball mill is generally used. In addition, two or more kinds of amorphous carbon materials obtained by the above production method can be used as a mixture, or one amorphous carbon material can be used by coating an amorphous carbon material different from that. You can also. Moreover, the negative electrode may contain 1 or more types of other negative electrode active materials in the range which does not impair the effect of this invention. Other negative electrode active materials include oxides of silicon represented by the formula SiO _x (where x is a positive real number), such as graphite, SiO ₂ , and SiO, and the formula TiO _x such as TiO ₂ and TiO, where x is Titanium oxide represented by (positive real number), vanadium oxide represented by the formula VO _x (where x is a positive real number) such as V ₂ O ₅ and VO ₂ , Fe ₃ O ₄ , Fe ₂ Iron oxide represented by the formula FeO _x (where x is a positive real number) such as O ₃ and FeO, and tin represented by the formula SnO _x (where x is a positive real number) such as SnO ₂ and SnO An oxide of tungsten, an oxide of tungsten represented by a general formula WO _x (where x is a positive real number) such as WO ₃ and WO ₂ , Li ₄ Ti ₅ O ₁₂ , LiVO ₂ (for example, Li _1.1 V _0.9 O ₂ ) complex metal oxide containing lithium and titanium and / or vanadium such as, Ti ₂ S _3, iS _2, TiS formula TiS _x (wherein, x represents a positive real number) such as sulfides of titanium represented _{by, V 3 S 4, VS 2} , VS formula VS _x such (wherein, x represents a positive real number) in sulfide vanadium _{represented, Fe 3 S 4, FeS 2} , FeS formula FeS _x (wherein, x represents a positive real number) such as sulfides of iron represented by, Mo ₂ S _3, etc. MoS ₂ formula MoS _x (wherein, x represents a positive real number) sulfides of molybdenum represented by, SnS _2, SnS formula SnS _x (wherein, x represents a positive real number) such as sulfides of tin represented by, WS ₂ Tungsten sulfide represented by the formula WS _x (where x is a positive real number), antimony sulfide represented by the formula SbS _x (where x is a positive real number) such as Sb ₂ S ₃ , _{Se 5 S 3, SeS 2,} SeS formula SeS _x (wherein, x represents a positive real number) such as sulfides selenium represented by, L _3-x A x N (wherein, A is Ni and / or Co, 0 <x <3.) And lithium-containing nitrides such. The proportion of the other negative electrode active material that the negative electrode may contain is preferably in the range of 1 part by weight or more and 10 parts by weight or less per 100 parts by weight of the amorphous carbon material. Here, it is more preferable to use graphite as another negative electrode active material. Further, an amorphous carbon material can be used by coating with another negative electrode active material.

  Next, a method for producing a negative electrode will be described. Using the above-described amorphous carbon material as a negative electrode active material, for example, a negative electrode can be produced as follows. In the present invention, the negative electrode can be produced by supporting a negative electrode active material and, if necessary, a negative electrode mixture containing a binder and a conductive agent on a negative electrode current collector.

  As the conductive agent used for the negative electrode mixture, the same carbon material as used in the production of the positive electrode mixture described later can be used. In that case, the ratio of the conductive agent in the negative electrode mixture is 2 to 20 parts by weight with respect to 100 parts by weight of the negative electrode active material. In the case where a fibrous carbon material described later is used as the conductive agent, this ratio can be lowered.

  Examples of the binder used for the negative electrode mixture include a polymer of a fluorine compound. Examples of the fluorine compound include fluorinated alkyl (C1-18) (meth) acrylate, perfluoroalkyl (meth) acrylate [for example, perfluorododecyl (meth) acrylate, perfluoro n-octyl (meth) acrylate, Perfluoro n-butyl (meth) acrylate], perfluoroalkyl-substituted alkyl (meth) acrylate [for example, perfluorohexylethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate], perfluorooxyalkyl (meth) acrylate [ For example, perfluorododecyloxyethyl (meth) acrylate and perfluorodecyloxyethyl (meth) acrylate, etc.], fluorinated alkyl (C1-C18) crotonate, fluorinated alkyl (carbon Number 1-18) Malate and fumarate, fluorinated alkyl (carbon number 1-18) itaconate, fluorinated alkyl-substituted olefin (about 2-10 carbon atoms, about 1-17 fluorine atoms) such as perfluorohexylethylene, carbon Examples thereof include fluorinated olefins, tetrafluoroethylene, trifluoroethylene, vinylidene fluoride, hexafluoropropylene and the like in which fluorine atoms are bonded to double bond carbons of about 2 to 10 and about 1 to 20 fluorine atoms.

  Other examples of the binder include monomer addition polymers containing an ethylenic double bond that does not contain a fluorine atom. Examples of such monomers include (cyclo) alkyl (C1-22) (meth) acrylate [for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (Meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, octadecyl (meth) acrylate, etc.]; aromatic ring-containing (meth) acrylate [for example, benzyl (Meth) acrylate, phenylethyl (meth) acrylate, etc.]; mono (meth) acrylate of alkylene glycol or dialkylene glycol (alkylene group having 2 to 4 carbon atoms) [for example, 2-hydroxyethyl (meth) acrylate, 2- Hi Roxypropyl (meth) acrylate, diethylene glycol mono (meth) acrylate]; (poly) glycerin (degree of polymerization 1 to 4) mono (meth) acrylate; polyfunctional (meth) acrylate [for example, (poly) ethylene glycol (degree of polymerization 1) ~ 100) di (meth) acrylate, (poly) propylene glycol (degree of polymerization 1-100) di (meth) acrylate, 2,2-bis (4-hydroxyethylphenyl) propane di (meth) acrylate, trimethylolpropane tri ( (Meth) acrylate monomers such as (meth) acrylate]; (meth) acrylamide (meth) acrylamide, (meth) acrylamide derivatives [eg, N-methylol (meth) acrylamide, diacetone acrylamide, etc.] Acrylamide monomer; ) Cyano group-containing monomers such as acrylonitrile, 2-cyanoethyl (meth) acrylate, 2-cyanoethylacrylamide; styrene and styrene derivatives having 7 to 18 carbon atoms [for example, α-methylstyrene, vinyltoluene, p-hydroxystyrene and Styrene monomers such as divinylbenzene] Diene monomers such as alkadienes having 4 to 12 carbon atoms [for example, butadiene, isoprene, chloroprene, etc.]; Carboxylic acid (2 to 12 carbon atoms) vinyl esters [for example, , Vinyl acetate, vinyl propionate, vinyl butyrate and vinyl octoate, etc.], carboxylic acid (2 to 12 carbon atoms) (meth) allyl ester [for example, (meth) allyl acetate, (meth) allyl propionate and octanoic acid ( Alkenyl ester monomers such as (meth) allyl etc.]; Epoxy group-containing monomers such as zir (meth) acrylate and (meth) allyl glycidyl ether; monoolefins having 2 to 12 carbon atoms [for example, ethylene, propylene, 1-butene, 1-octene and 1-dodecene, etc.] Monoolefins; chlorine, bromine or iodine atom-containing monomers, halogen atom-containing monomers other than fluorine such as vinyl chloride and vinylidene chloride; (meth) acrylic acid such as acrylic acid and methacrylic acid; butadiene, isoprene, etc. Examples thereof include a conjugated double bond-containing monomer. Further, as the addition polymer, for example, a copolymer such as an ethylene / vinyl acetate copolymer, a styrene / butadiene copolymer, or an ethylene / propylene copolymer may be used. Moreover, the carboxylic acid vinyl ester polymer may be partially or completely saponified, such as polyvinyl alcohol. The conjugate may be a copolymer of a fluorine compound and a monomer containing an ethylenic double bond not containing a fluorine atom.

  Other examples of the binder include, for example, polysaccharides such as starch, methylcellulose, carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylhydroxyethylcellulose, nitrocellulose, and derivatives thereof; phenol resin; melamine resin; polyurethane resin A urea resin; a polyamide resin; a polyimide resin; a polyamideimide resin. Further, two or more of the aforementioned binders may be mixed and used. As a compounding quantity of a binder, it is about 0.5-20 weight part normally with respect to 100 weight part of negative electrode active materials, Preferably it is 2-10 weight, In this way, binding property with a negative electrode collector. It is also possible to obtain a more excellent negative electrode mixture. The negative electrode mixture can also contain an aggregation inhibitor such as vinylpyrrolidone.

  Examples of the negative electrode current collector include Cu, Ni, and stainless steel, and Cu is preferable because it is difficult to form an alloy with lithium and it can be easily processed into a thin film. Examples of the shape of the negative electrode current collector include a foil shape, a flat plate shape, a mesh shape, a net shape, a lath shape, a punching metal shape, an embossed shape, or a combination thereof (for example, a mesh flat plate). Is mentioned. Concavities and convexities by etching treatment may be formed on the surface of the negative electrode current collector.

  The method for supporting the negative electrode mixture on the negative electrode current collector is the same as in the case of the positive electrode described later, and is pasted into a paste using a method by pressure molding, a solvent, etc., dried and pressed. Examples of the method include pressure bonding. Solvents include aprotic polar solvents such as N-methyl-2-pyrrolidone, alcohols such as isopropyl alcohol, ethyl alcohol or methyl alcohol, ethers such as propylene glycol dimethyl ether, ketones such as acetone, methyl ethyl ketone or methyl isobutyl ketone And protic polar solvents such as water. When the binder is thickened, a plasticizer may be used to facilitate application to the current collector. By the method mentioned above, the negative electrode in this invention can be manufactured. The thickness of the negative electrode is usually about 5 to 500 μm.

  In the present invention, the positive electrode only needs to be capable of doping and dedoping lithium ions at a higher potential than the negative electrode. The positive electrode can be produced by supporting a positive electrode mixture containing a positive electrode active material, a binder and, if necessary, a conductive agent on a positive electrode current collector.

Examples of the positive electrode active material include known materials. Specifically, the lithium composite metal oxide contains at least one transition metal element selected from V, Mn, Fe, Co, Ni, Cr, and Ti. The lithium composite metal oxide having an α-NaFeO ₂ type structure is preferable, and in terms of high average discharge potential, lithium cobaltate, lithium nickelate, and lithium nickelate are more preferable. Examples thereof include lithium composite metal oxides that are partially substituted with other elements such as Mn and Co. In addition, a lithium composite metal oxide having a spinel structure such as lithium manganese spinel can be given.

  A carbon material can be used as the conductive agent, and examples of the carbon material include graphite powder, carbon black, acetylene black, and fibrous carbon materials (carbon nanotubes, carbon nanofibers, etc.). Since carbon black and acetylene black are fine and have a large surface area, adding a small amount to the positive electrode mixture can increase the electrical conductivity inside the electrode and improve the charge / discharge efficiency and rate characteristics. This decreases the binding property between the positive electrode mixture and the positive electrode current collector by the binder, and causes an increase in internal resistance. Usually, the ratio of the conductive agent in the positive electrode mixture is 5 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the positive electrode active material. When the fibrous carbon material as described above is used as the conductive agent, this ratio can be lowered.

  As the binder, a thermoplastic resin can be used. Specifically, polyvinylidene fluoride (hereinafter sometimes referred to as PVDF), polytetrafluoroethylene (hereinafter sometimes referred to as PTFE), and four fluorine. Fluoropolymers such as fluorinated ethylene / hexafluoropropylene / vinylidene fluoride copolymers, propylene hexafluoride / vinylidene fluoride copolymers, tetrafluoroethylene / perfluorovinyl ether copolymers, polyethylene, polypropylene, etc. Polyolefin resin and the like. Moreover, you may mix and use these 2 or more types. In addition, a fluororesin and a polyolefin resin are used as a binder so that the fluororesin is 1 to 10 parts by weight and the polyolefin resin is 0.1 to 2 parts by weight with respect to 100 parts by weight of the positive electrode active material. By containing, a positive electrode mixture excellent in binding property with the positive electrode current collector can be obtained. The positive electrode mixture can also contain an aggregation inhibitor such as vinylpyrrolidone.

  As the positive electrode current collector, Al, Ni, stainless steel or the like can be used, and Al is preferable in that it is easily processed into a thin film and is inexpensive. Examples of the shape of the positive electrode current collector include a foil shape, a flat plate shape, a mesh shape, a net shape, a lath shape, a punching metal shape, an embossed shape, or a combination thereof (for example, a mesh flat plate). Is mentioned. Concavities and convexities by etching treatment may be formed on the surface of the positive electrode current collector.

  As a method of supporting the positive electrode mixture on the positive electrode current collector, a method of pressure molding, or a method of pasting using an organic solvent, applying on the positive electrode current collector, drying and pressing to fix the positive electrode current collector Is mentioned. In the case of forming a paste, a slurry composed of a positive electrode active material, a conductive agent, a binder, and an organic solvent is prepared. Examples of the organic solvent include amine solvents such as N, N-dimethylaminopropylamine and diethylenetriamine, ether solvents such as tetrahydrofuran, ketone solvents such as methyl ethyl ketone, ester solvents such as methyl acetate, dimethylacetamide, N-methyl- Examples include amide solvents such as 2-pyrrolidone. Examples of the method for applying the positive electrode mixture to the positive electrode current collector include a slit die coating method, a screen coating method, a curtain coating method, a knife coating method, a gravure coating method, and an electrostatic spray method. The positive electrode in this invention can be manufactured by the method mentioned above. The thickness of the positive electrode is usually about 5 to 500 μm.

In the secondary battery, the electrolytic solution is usually composed of an organic solvent containing an electrolyte. Examples of the electrolyte include LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiN (SO ₂ CF ₃ ) (COCF ₃ ), Li (C ₄ F ₉ SO ₃ ), LiC (SO ₂ CF ₃ ) ₃ , Li ₂ B ₁₀ Cl ₁₀ , LiBOB (where BOB is bis (oxalato) borate). ), Lithium salts such as lower aliphatic carboxylic acid lithium salts and LiAlCl _4, and a mixture of two or more of these may be used. The lithium salt is usually selected from the group consisting of LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ and LiC (SO ₂ CF ₃ ) ₃ containing fluorine among these. Those containing at least one selected are used.

Examples of the organic solvent in the electrolytic solution include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one, and 1,2-di (methoxy). Carbonates such as carbonyloxy) ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran Ethers such as methyl formate, methyl acetate, and γ-butyrolactone; Nitriles such as acetonitrile and butyronitrile; N, N-dimethylformamide, N, N-dimethylacetoa Amides such as carbon; Carbamates such as 3-methyl-2-oxazolidone; Sulfur-containing compounds such as sulfolane, dimethyl sulfoxide, 1,3-propane sultone, or those obtained by further introducing a fluorine substituent into the above organic solvent Usually, two or more of these are mixed and used. Among these, a mixed solvent containing carbonates is preferable, and a mixed solvent of cyclic carbonate and acyclic carbonate or cyclic carbonate and ether is more preferable. As the mixed solvent of the cyclic carbonate and the non-cyclic carbonate, a mixed solvent containing ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is preferable in that it has a wide operating temperature range, excellent load characteristics, and hardly decomposes. Further, in view of particularly excellent safety improving effect is obtained, it is preferable to use an electrolytic solution containing an organic solvent having a lithium salt and a fluorine substituent containing fluorine such as LiPF _6. A mixed solvent containing ethers having fluorine substituents such as pentafluoropropyl methyl ether and 2,2,3,3-tetrafluoropropyl difluoromethyl ether and dimethyl carbonate has excellent high-current discharge characteristics, preferable.

  The concentration of the electrolyte in the nonaqueous electrolytic solution is usually about 0.1 mol / L to 2 mol / L, and preferably about 0.3 mol / L to 1.5 mol / L.

  Moreover, you may use a well-known technique for manufacture of a nonaqueous electrolyte secondary battery (for example, lithium secondary battery). For example, the above-described positive electrode, separator (laminated film), and negative electrode are laminated in this order and wound as necessary to obtain an electrode group, and the electrode group is housed in a container such as a battery can. It can be manufactured by impregnating an electrode group with an electrolytic solution. Here, the heat-resistant porous layer in the separator (laminated film) may be disposed on either the positive electrode side or the negative electrode side, but is preferably disposed on the negative electrode side. By disposing the heat-resistant porous layer on the negative electrode side, depletion of the electrolyte is suppressed, and the discharge capacity retention rate under high rate conditions and low temperature conditions is further improved. Moreover, when the heat resistant porous layer is laminated | stacked on both surfaces of the porous film, two heat resistant porous layers will be arrange | positioned at the positive electrode side and the negative electrode side, respectively.

  As the shape of the electrode group, for example, a shape in which the cross section when the electrode group is cut in a direction perpendicular to the winding axis is a circle, an ellipse, a rectangle, a rectangle with rounded corners, etc. Can be mentioned. In addition, examples of the shape of the battery include a paper shape, a coin shape, a cylindrical shape, and a square shape.

  Next, the present invention will be described in more detail using examples.

Production Example 1 (Production Example of Laminated Film)
(1) Production of coating solution After 272.7 g of calcium chloride was dissolved in 4200 g of NMP, 132.9 g of paraphenylenediamine was added and completely dissolved. To the obtained solution, 243.3 g of terephthalic acid dichloride (hereinafter abbreviated as TPC) was gradually added and polymerized to obtain para-aramid, which was further diluted with NMP to obtain a para-aramid solution having a concentration of 2.0% by weight ( A) was obtained. To 100 g of the obtained para-aramid solution, 2 g of alumina powder (a) (manufactured by Nippon Aerosil Co., Ltd., alumina C, average particle size 0.02 μm, particles are substantially spherical, particle aspect ratio is 1) and alumina powder (b) 2 g (Sumitomo Chemical Co., Ltd. Sumiko Random, AA03, average particle size 0.3 μm, particles are approximately spherical, particle aspect ratio is 1) and 4 g in total are added and mixed as a filler, and processed three times with a nanomizer, Furthermore, it filtered with 1000 mesh metal-mesh and deaerated under reduced pressure, and manufactured the slurry-form coating liquid (B). The weight of alumina powder (filler) with respect to the total weight of para-aramid and alumina powder is 67% by weight.

(2) Production of Laminated Film As the porous film, a polyethylene porous film (film thickness 12 μm, air permeability 140 seconds / 100 cc, average pore diameter 0.1 μm, porosity 50%) was used. The polyethylene porous film was fixed on a PET film having a thickness of 100 μm, and the slurry-like coating liquid (B) was applied onto the porous film by a bar coater manufactured by Tester Sangyo Co., Ltd. While the coated porous film on the PET film is integrated, it is immersed in water which is a poor solvent to deposit a para-aramid porous layer (heat-resistant porous layer), and then the solvent is dried to obtain a heat-resistant porous layer. A laminated film 1 in which a porous film and a porous film were laminated was obtained. The thickness of the laminated film 1 was 16 μm, and the thickness of the para-aramid porous layer (heat resistant porous layer) was 4 μm. The air permeability of the laminated film 1 was 180 seconds / 100 cc, and the porosity was 50%. When the cross section of the heat-resistant porous layer in the laminated film 1 was observed with a scanning electron microscope (SEM), a relatively small micropore of about 0.03 μm to 0.06 μm and a relatively large micropore of about 0.1 μm to 1 μm. It was found to have Further, as described above, para-aramid, which is a nitrogen-containing aromatic polymer, is used for the heat resistant porous layer of the laminated film 1, and the thermal film breaking temperature of the laminated film 1 is about 400 ° C. The laminated film was evaluated by the following method.

(3) Evaluation of laminated film (A) Thickness measurement The thickness of the laminated film and the thickness of the porous film were measured in accordance with JIS standards (K7130-1992). Moreover, as the thickness of the heat resistant porous layer, a value obtained by subtracting the thickness of the porous film from the thickness of the laminated film was used.
(B) Measurement of air permeability by Gurley method The air permeability of the laminated film was measured by a digital timer type Gurley type densometer manufactured by Yasuda Seiki Seisakusho Co., Ltd. based on JIS P8117.
(C) Porosity A sample of the obtained laminated film was cut into a 10 cm long square and the weight W (g) and thickness D (cm) were measured. Obtain the weight (Wi (g)) of each layer in the sample, and obtain the volume of each layer from Wi and the true specific gravity (true specific gravity i (g / cm ³ )) of the material of each layer, The porosity (volume%) was obtained from the following formula.
Porosity (volume%) = 100 × {1− (W1 / true specific gravity 1 + W2 / true specific gravity 2 + ·· + Wn / true specific gravity n) / (10 × 10 × D)}

Production Example 2 (Production of positive electrode)
Positive electrode active material (Cellseed C-10N (Nippon Chemical Industry Co., Ltd., LiCoO ₂ )): Conductive agent (acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd.)): Binder (PTFE31-JR (Mitsui / DuPont Fluorochemical Co., Ltd.) Manufactured)): The binder (Serogen 4H (Daiichi Kogyo Seiyaku Co., Ltd.)) was mixed so that the mixing ratio was 92: 2.7: 4.55: 0.75 (weight ratio). A certain amount of water is put into a kneader to dissolve serogen 4H, and then a positive electrode active material, a conductive agent and a PTFE binder are added and kneaded, and the viscosity of the obtained paste becomes 2700 ± 1000 cp suitable for coating. Thus, water was added again to obtain a positive electrode mixture. The paste was applied to predetermined portions on both sides of a 20 μm thick Al foil serving as a positive electrode current collector, dried, roll pressed, and slitted to obtain a positive electrode 1 having a width of 54 mm.

Production Example 3 (Manufacture of negative electrode)
Negative electrode active material (amorphous carbon material): The binder (Serogen 4H (Daiichi Kogyo Seiyaku Co., Ltd.)) was weighed so that the mixing ratio was 98: 2 (weight ratio). After a certain amount of water is put into a kneader and serogen 4H is dissolved, the negative electrode active material is added and kneaded, and water is added again so that the viscosity of the obtained paste is 2100 ± 500 cp suitable for coating. In addition, a paste of negative electrode mixture was obtained. The paste was applied to predetermined portions on both sides of a 12 μm-thick Cu foil serving as a negative electrode current collector, dried, roll-pressed, and slitted to obtain a negative electrode 1 having a width of 56 mm. In addition, as an amorphous carbon material, the powder form obtained by carbonizing 50 g of Bell Pearl R800 (manufactured by Air Water Co., Ltd .; phenol resin) in an alumina sheath and holding it at 1100 ° C. for 20 hours in an Ar stream. An amorphous carbon material was used.

Example 1 (Production of non-aqueous electrolyte secondary battery of the present invention)
The laminated film in Production Example 1 was used as a separator, laminated together with positive electrode 1 in Production Example 2 in which an aluminum tab was welded, and negative electrode 1 in Production Example 3 in which a nickel tab was welded, and wound in a spiral shape. The obtained winding group was put into a battery can for 18650 cylindrical batteries, necked with a table lathe, and the bottom of the negative electrode tab and the lid of the positive electrode tab were welded, followed by vacuum drying overnight. Thereafter, the solvent carbonate-based in a glove box in an argon gas atmosphere, a non-aqueous electrolyte solution of LiPF ₆ salt containing 1.3 mol / L (manufactured by Kishida Chemical), and 6g poured performs caulking, 18650 cylindrical A battery was manufactured. The heat-resistant porous layer in the laminated film was arranged on the negative electrode side.

(High rate cycle test)
Using the nonaqueous electrolyte secondary battery obtained above, a high rate cycle test was performed under the following evaluation conditions.
Initial charging / discharging: Starting from 50 mA, the current value was increased stepwise by 50 mA every 30 minutes, charged to 4.2 V, and then discharged to 3 V.
High-rate cycle test charge / discharge conditions: Charging was performed by CC-CV (constant current constant voltage) charging at 5 C up to 4.2 V. The discharge was CC discharge at 5C and cut off at a voltage of 2.9V. Charging / discharging after the next cycle was performed at the same rate as described above, with the rest period between charging and discharging being 15 minutes, and cut off at a charging voltage of 4.2 V and a discharging voltage of 2.9 V as in the first cycle. This charging / discharging was repeated 500 times in a thermostat set to 20 ° C.

(Low temperature cycle test)
Using the nonaqueous electrolyte secondary battery obtained above, a low temperature cycle test was performed under the following evaluation conditions.
Initial charging / discharging: Starting from 50 mA, the current value was increased stepwise by 50 mA every 30 minutes, charged to 4.2 V, and then discharged to 3 V.
Low temperature cycle test charge / discharge conditions: Charging was performed by CC-CV (constant current constant voltage) charging at 0.2 C up to 4.2 V. The discharge was CC discharge at 0.2 C and cut off at a voltage of 2.9 V. Charging / discharging after the next cycle was performed at the same rate as described above, with the rest period between charging and discharging being 15 minutes, and cut off at a charging voltage of 4.2 V and a discharging voltage of 2.9 V as in the first cycle. This charging / discharging was repeated 500 times in a thermostat set to −20 ° C.

(Evaluation results of the nonaqueous electrolyte secondary battery of the present invention)
Using the non-aqueous electrolyte secondary battery of Example 1, a high rate cycle test and a low temperature cycle test were performed under the above conditions. As a result, the following results were obtained. As a result of the high rate cycle test, the discharge capacity at 500th cycle (discharge capacity retention rate) relative to the discharge capacity at 1st cycle was as good as 84% or more. As a result of the low-temperature cycle test, the discharge capacity at 500th cycle (discharge capacity retention rate) with respect to the discharge capacity at 1st cycle was as good as 84% or more.

Comparative Example 1 (Comparative secondary battery)
A comparative secondary battery 1 was produced in the same manner as in Example 1 except that a polyolefin porous film having no heat-resistant porous layer was used as a separator. In the same manner as in Example 1, a high rate cycle test, a low temperature A cycle test was performed.

(Comparison secondary battery evaluation results)
As a result of the high-rate cycle test, the discharge capacity at 500th cycle (discharge capacity retention rate) with respect to the discharge capacity at 1st cycle was lower than 80%. As a result of the low-temperature cycle test, the discharge capacity at 500th cycle (discharge capacity retention rate) with respect to the discharge capacity at 1st cycle was lower than 80%.

Claims (8)

  A positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, wherein the negative electrode has a negative electrode active material containing an amorphous carbon material, A non-aqueous electrolyte secondary battery comprising a laminated film in which a heat-resistant porous layer and a porous film are laminated.   The nonaqueous electrolyte secondary battery according to claim 1, wherein the heat resistant porous layer in the laminated film is disposed on the negative electrode side.   The nonaqueous electrolyte secondary battery according to claim 1, wherein the heat resistant porous layer is a heat resistant porous layer containing a heat resistant resin.   The nonaqueous electrolyte secondary battery according to claim 3, wherein the heat resistant resin is a nitrogen-containing aromatic polymer.   The nonaqueous electrolyte secondary battery according to claim 3 or 4, wherein the heat resistant resin is an aromatic polyamide.   The nonaqueous electrolyte secondary battery according to claim 3, wherein the heat resistant porous layer further contains a filler.   The nonaqueous electrolyte secondary battery according to claim 6, wherein a weight of the filler is 20 or more and 95 or less, where 100 is a total weight of the heat resistant porous layer.   The nonaqueous electrolyte secondary battery according to claim 1, wherein the heat-resistant porous layer has a thickness of 1 μm or more and 10 μm or less.