JP2002237305A - Nonaqueous electrolytic battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolytic solution battery having a superior cycle performance which is free from falling off and peeling-off of carbonaceous materials out of a current collector in working of a carbon negative electrode material for the nonaqueous electrolyte. SOLUTION: A binder of the negative electrode contains metal salt(s) of carboxymethylcellulose and butadiene containing rubber, and that which has the value of etherification degree of the metal salt(s) of carboxymethylcellulose larger than 0.65 is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a carbon anode used for a non-aqueous electrolyte battery, and more particularly to a binder used for the carbon anode.

[0002]

2. Description of the Related Art Carbonaceous materials such as coke, graphite, and graphite are frequently used for negative electrodes of nonaqueous electrolyte secondary batteries, particularly lithium ion batteries. In such a negative electrode, a binder is generally added for the purpose of binding the carbonaceous materials or binding the carbonaceous material and the negative electrode current collector. As the binder, polytetrafluoroethylene is mainly used to increase the solubility in a solvent for dispersion and suppress the solubility in an electrolytic solution. Modified ones, or copolymers of these with polyethylene and polypropylene have been used. Further, for reasons such as the reaction of the fluorine resin with lithium, a thermosetting resin such as a vinyl chloride-vinyl acetate copolymer, a phenol resin, a styrene-butadiene rubber, etc. have been used instead of the fluorine resin. Further, JP-A-11-1113
Japanese Patent Application Publication No. 00-200100 discloses that JI is used as a binder in order to improve the binding force between carbonaceous materials and between the carbonaceous material and the negative electrode current collector.
If the tensile strength by S standard test is 80kg / cm2 or more,
A technique using a butadiene-containing rubber binder having a breaking elongation of 500% or more is disclosed.

On the other hand, when a slurry containing a carbonaceous material is applied on a current collector, carboxymethyl cellulose or the like is used as a thickener in order to improve the applied state. Japanese Patent Application Laid-Open No. Hei 9-161777 discloses that in order to suppress a decrease in the electron conductivity of a negative electrode due to the addition of the thickener, a metal salt of carboxymethyl cellulose is used as the thickener, and styrene-butadiene is used as a binder. Techniques for use with rubber are disclosed.

However, even if these techniques are used,
In particular, the binding force between the carbonaceous material and the negative electrode current collector is not sufficient. For example, a slurry containing the carbonaceous material is applied on the current collector, dried, cut, and roll-pressed. In some cases, peeling or falling off from the negative electrode current collector.

This will be described in more detail. A carbon negative electrode and a power generating element for a battery are usually prepared as follows. A slurry obtained by kneading the carbonaceous material into a paste together with a binder, a thickener, and a solvent for dispersion is applied on a negative electrode current collector, and dried. Next, a slit is cut into a band having a predetermined width. Thereafter, roll pressing is performed. The strip-shaped negative electrode thus obtained is wound together with the separator and the positive electrode. Here, in the slit cutting step, the negative electrode material near the blade of the slitter may fall off. Alternatively, the negative electrode material may adhere to the roll side in the roll pressing step and peel off from the negative electrode current collector. Further, in the winding step, the negative electrode material was sometimes dropped. In addition, even if no dropout occurs in these steps, the negative electrode swells due to the electrolyte during use of the battery, which makes it impossible to maintain electron conduction between the negative carbonaceous material powders and causes a reduction in battery capacity. was there. These problems are likely to occur particularly when, for example, graphite having strong self-lubricating properties and cleavage properties is used.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to improve the binding force between carbonaceous materials and the binding force between carbonaceous materials and a negative electrode current collector. An object of the present invention is to prevent the carbonaceous material from peeling off or falling off, suppress the swelling of the negative electrode in the battery, and improve the high-rate discharge characteristics and the cycle characteristics of the nonaqueous electrolyte battery using the carbon negative electrode.

[0007]

According to the present invention, there is provided a negative electrode having a carbonaceous material capable of occluding and releasing lithium ions, a binder and a current collector, a positive electrode, and a negative electrode. In a non-aqueous electrolyte battery having an aqueous electrolyte, the binder contains a carboxymethylcellulose metal salt and a butadiene-containing rubber, and the value of the degree of etherification of the carboxymethylcellulose metal salt is greater than 0.65. I have. In particular, when the value of the degree of etherification is larger than 0.70, it is more preferable that a battery having excellent high-rate discharge characteristics can be provided.

Further, the present invention is characterized in that the value of the degree of etherification is less than 0.95, as described in claim 2.

Here, the degree of etherification refers to the degree of etherification of carboxymethylcellulose having one carboxymethyl group per unit of anhydrous glucose (DS. ) 1.0. The degree of etherification can theoretically be up to 3.

In other words, the present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, surprisingly, the value of the degree of etherification of carboxymethylcellulose metal salt, which has been conventionally known as a thickener, has been surprisingly reduced. It has been found that there is a great relationship between the binding strength, particularly the binding strength between the carbonaceous material and the negative electrode current collector.

As is conventionally known, the binding strength between the carbonaceous material and the negative electrode current collector can be improved by increasing the amount of a binder such as styrene-butadiene rubber. However, when the amount of the binder is increased, the energy density of the negative electrode decreases, and the electron conduction between the carbonaceous materials is hindered, which causes a reduction in battery performance. Thus, the present inventors have studied variously changing the ratio of a rubber-based binder such as styrene-butadiene rubber and a thickener such as carboxymethylcellulose to be added to the negative electrode. Did not reach. Next, when the various physical properties of the thickener were changed and examined, it was surprisingly found that the value of the degree of etherification of the metal salt of carboxymethylcellulose, which was considered to be unrelated to the binding force with the negative electrode current collector, was surprisingly increased. It has been found that the above problem can be solved by setting the value in a specific range.

That is, when the value of the degree of etherification of the metal salt of carboxymethylcellulose added to the negative electrode is low, the binding force with the negative electrode current collector is not sufficient, and the carbonaceous material often falls off in the slit cutting step. Occurred. As the value of the degree of etherification was increased, the binding force with the negative electrode current collector was improved, and the falling off in the cutting step using the slitter did not occur. However, when the value of the degree of etherification was set to be high, the carbonaceous material sometimes adhered to the roll side in the roll pressing step and was peeled off from the current collector. This is presumably because, since a metal was used for the roll, the use of carboxymethylcellulose having a high degree of etherification resulted in the carbonaceous material having an increased binding force with the metal being easily attached to the roll side. From this point of view, when the above-described production process is adopted, it is expected that the value of the degree of etherification of the carboxymethylcellulose metal salt added to the negative electrode material has a preferable constant range. The present inventors have found through various experiments a preferable range for the value of the degree of etherification. These experiments and their results will be described in detail in the following examples.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments.

The nonaqueous electrolyte battery according to the present invention comprises a positive electrode having a positive electrode active material as a main component, a negative electrode having a carbonaceous material as a main component, and a nonaqueous electrolyte containing an electrolyte salt in a nonaqueous solvent. Generally, a separator is provided between the positive electrode and the negative electrode.

As the non-aqueous electrolyte, those generally proposed for use in lithium batteries and the like can be used. As the non-aqueous solvent, cyclic carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate, and vinylene carbonate;
cyclic esters such as γ-butyrolactone and γ-valerolactone; chain carbonates such as dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate; chain esters such as methyl formate, methyl acetate and methyl butyrate; tetrahydrofuran or derivatives thereof; 1,3
Ethers such as dioxane, 1,4-dioxane, 1,2-dimethoxyethane, 1,4-dibutoxyethane and methyldiglyme; nitriles such as acetonitrile and benzonitrile; dioxolane or a derivative thereof; sulfolane, sultone or Derivatives and the like may be used alone, or a mixture of two or more thereof, but are not limited thereto.

As the electrolyte salt, for example, LiCl
O_Four, LiBF_Four, LiAsF₆, LiPF₆, LiCF_Three
SO_Three, LiN (CF_ThreeSO_Two)_Two, LiN (C_TwoF_FiveS
O_Two)_Two, LiSCN, LiBr, LiI, Li_TwoSO_Four,
Li_TwoB_TenCl_Ten, NaClO_Four, NaI, NaSCN,
NaBr, KCLO_Four, KSCN and other lithium (L
i) one of sodium (Na) or potassium (K)
Inorganic ion salt containing LiN (CF _ThreeSO_Two)_Two, LiN
(C_TwoF_FiveSO_Two)_Two, (CH_Three)_FourNBF_Four, (CH_Three)_FourN
Br, (C_TwoH_Five)_FourNCLO_Four, (C_TwoH_Five)_FourNI, (C_Three
H₇)_FourNBr, (n-C_FourH₉) _FourNCLO_Four, (N-C_Four
H₉)_FourNI, (C_TwoH_Five)_FourN-maleate, (C_TwoH
_Five)_FourN-benzoate, (C_TwoH_Five)_FourN-phta
quaternary ammonium salts such as late, stearyl sulfone
Lithium oxide, lithium octyl sulfonate, dodecyl
Organic ion salts such as lithium benzene sulfonate;
These ionic compounds may be used alone or in combination of two or more.
It is possible to use a mixture of the above.

In particular, LiBF ₄ has a lower reactivity with water present in the electrolytic solution than the other fluorinated lithium salts exemplified above, and thus generates hydrofluoric acid which causes corrosion of the electrodes and the exterior material. The degree is small, for example, for the purpose of weight reduction,
Even when a thin material such as a metal-resin composite film is employed as the exterior material, a non-aqueous electrolyte battery having high durability can be obtained, and thus is preferable as an electrolyte salt.

Further, LiBF ₄ and LiN (C ₂ F ₅ S
By mixing and using a lithium salt having a perfluoroalkyl group such as O ₂ ) ₂ , the viscosity of the electrolytic solution can be further reduced, so that the low-temperature characteristics can be further improved, which is more desirable. The concentration of the electrolyte salt in the electrolytic solution is from 0.1 mol / l to 5 mol / l in order to reliably obtain a nonaqueous electrolyte battery having high battery characteristics.
1 is preferable, and more preferably, 1 mol / l to 2.
5 mol / l.

As the positive electrode active material which is a main component of the positive electrode, it is desirable to use a lithium-containing transition metal oxide, a lithium-containing phosphate, a lithium-containing sulfate, or the like, alone or as a mixture. Examples of lithium-containing transition metal oxides include general formulas Li _y Co _1-x M _x O ₂ and Li _y Mn _2-x M _x
O ₄ (M is a metal of Group I to VIII (eg, Li, C
a, Cr, Ni, Fe, and Co), and the x value indicating the amount of dissimilar element substitution is effective up to the maximum amount that can be substituted, but is preferably 0 from the viewpoint of discharge capacity.
≦ x ≦ 1. For the y value indicating the amount of lithium, the maximum amount capable of reversibly using lithium is effective,
Preferably, 0 ≦ y ≦ 2 from the viewpoint of discharge capacity. ), But is not limited thereto.

Further, another positive electrode active material may be mixed with the lithium-containing compound and used as the other positive electrode active material. Examples of the other positive electrode active material include Group I materials such as CuO, Cu ₂ O, Ag ₂ O, CuS, and CuSO _4. metal compounds, TiS _2, SiO _2, IV group metal compound of SnO, _{etc., V 2 O 5, V 6} O 1 2, VO x, Nb 2 O 5, Bi
Group V metal compounds such as ₂ O ₃ and Sb ₂ O ₃ , CrO ₃ and Cr ₂ O
Group VI metal compound such as ₃ , ₃ , MoO ₃ , MoS ₂ , WO ₃ , SeO ₂ , Group VII metal compound such as MnO ₂ , Mn ₂ O ₃ , Fe ₂
O ₃ , FeO, Fe ₃ O ₄ , Ni ₂ O ₃ , NiO, CoO ₃ ,
Group VIII metal compound such as CoO or the general formula Li _x M
X ₂ , Li _x MN _y X ₂ (M and N are metals of Group I to VIII, X
Represents a chalcogen compound such as oxygen and sulfur. ) And the like, for example, a metal compound such as a lithium-cobalt-based composite oxide or a lithium-manganese-based composite oxide,
Examples include, but are not limited to, conductive polymer compounds such as disulfide, polypyrrole, polyaniline, polyparaphenylene, polyacetylene, and polyacene-based materials, and pseudo-graphite structured carbonaceous materials.

Among the carbonaceous materials of the negative electrode, which are the main components of the negative electrode, graphite has an operating potential very close to that of metallic lithium. It is preferable as a negative electrode material because irreversible capacity can be reduced.

The analysis results of X-ray diffraction of graphite which can be suitably used are shown below: Lattice spacing (d002) 0.333 to 0.350 nm Crystallite size La in the a-axis direction La 20 nm or more c-axis Direction crystallite size Lc 20 nm or more True density 2.00 to 2.25 g / cm ^{3 In} addition, metal oxides such as tin oxide and silicon oxide, phosphorus, boron, amorphous carbon and the like are added to graphite. It is also possible to carry out the reforming. In particular, by modifying the surface of graphite by the above-described method, it is possible to suppress the decomposition of the electrolyte and to improve the battery characteristics, which is desirable. Further, lithium metal, lithium-aluminum, lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium, and a lithium metal-containing alloy such as a wood alloy may be used in combination with graphite, Graphite or the like into which lithium has been inserted by chemical reduction can also be used as the negative electrode active material.

It is also possible to modify at least the surface layer portion of the powder of the positive electrode active material and the powder of the negative electrode material with a material having good electron conductivity and ion conductivity, or a compound having a hydrophobic group. For example, substances having good electron conductivity such as gold, silver, carbon, nickel, and copper; substances having good ion conductivity such as lithium carbonate, boron glass, and solid electrolyte;
Alternatively, a material having a hydrophobic group such as silicone oil may be coated by applying a technique such as plating, sintering, mechanofusion, vapor deposition, or baking.

The powder of the positive electrode active material and the powder of the negative electrode material are:
The average particle size is desirably 100 μm or less.
In particular, the powder of the positive electrode active material is desirably 10 μm or less for the purpose of improving the high output characteristics of the nonaqueous electrolyte battery. In order to obtain the powder in a predetermined shape, a pulverizer or a classifier is used. For example, a mortar, a ball mill, a sand mill, a vibration ball mill, a planetary ball mill, a jet mill, a counter jet mill, a swirling air jet mill, a sieve, and the like are used. At the time of pulverization, wet pulverization in which an organic solvent such as water or hexane coexists can be used. The classification method is not particularly limited, and a sieve, an air classifier, or the like is used as needed in both dry and wet methods.

The positive electrode active material and the negative electrode material, which are the main components of the positive electrode and the negative electrode, have been described in detail. In addition to the main components, the positive electrode and the negative electrode contain a conductive agent, a binder, and a filler. , May be contained as other components.

The conductive agent is not limited as long as it is an electron conductive material that does not adversely affect battery performance.
Natural graphite (flaky graphite, flaky graphite, earthy graphite, etc.), artificial graphite, carbon black, acetylene black, ketjen black, carbon whisker, carbon fiber, metal (copper, nickel, aluminum, silver, gold, etc.) powder, A conductive material such as a metal fiber or a conductive ceramic material can be included as one type or a mixture thereof.

Among these, acetylene black is preferable as the conductive agent from the viewpoints of electron conductivity and coatability. The amount of the conductive agent is preferably 1% by weight to 50% by weight, and more preferably 2% by weight to 3% by weight based on the total weight of the positive electrode or the negative electrode.
0% by weight is preferred. These mixing methods are physical mixing, and ideally, uniform mixing. For this reason, powder mixers such as V-type mixers, S-type mixers, grinders, ball mills, and planetary ball mills are dry-type,
Alternatively, it is possible to mix them by a wet method.

Examples of the binder include thermoplastic resins such as polytetrafluoroethylene, polyvinylidene fluoride, polyethylene and polypropylene, ethylene-propylene diene terpolymer (EPDM), and sulfonated EPD.
M, a polymer having rubber elasticity such as styrene-butadiene rubber (SBR) or fluororubber, or a polysaccharide such as carboxymethylcellulose can be used alone or as a mixture of two or more. Further, it is desirable that a binder having a functional group that reacts with lithium, such as a polysaccharide, be deactivated by, for example, methylation. The amount of the binder added is 1 to the total weight of the positive electrode or the negative electrode.
It is preferably 50% by weight, particularly preferably 2 to 30% by weight.

As the filler, any material may be used as long as it does not adversely affect battery performance. Usually, olefin polymers such as polypropylene and polyethylene, aerosil, zeolite, glass, carbon and the like are used. The amount of the filler is preferably 30% by weight or less based on the total weight of the positive electrode or the negative electrode.

The positive electrode and the negative electrode are prepared by mixing the active material, the conductive agent and the binder with an organic solvent such as N-methylpyrrolidone, toluene, and the like. It is suitably prepared by coating on top and drying. Regarding the application method, for example, it is desirable to apply to any thickness and any shape using means such as roller coating such as an applicator roll, screen coating, a doctor blade method, spin coating, and a bar coder. It is not limited.

The current collector may be any electronic conductor that does not adversely affect the constructed battery. For example, as the positive electrode current collector, aluminum, titanium,
In addition to stainless steel, nickel, calcined carbon, conductive polymer, conductive glass, etc., the surface of aluminum, copper, etc. is coated with carbon, nickel, titanium, silver, etc. for the purpose of improving adhesion, conductivity and oxidation resistance. Can be used. As the current collector for the negative electrode, copper, nickel, iron, stainless steel, titanium, aluminum, calcined carbon, conductive polymer, conductive glass, Al-Cd alloy, etc.
For the purpose of improving conductivity and oxidation resistance, a material obtained by treating the surface of copper or the like with carbon, nickel, titanium, silver, or the like can be used. These materials can be oxidized on the surface.

The current collector may be in the form of a foil, a film, a sheet, a net, a punched or expanded material, a lath, a porous material, a foamed material, a formed fiber group, or the like. Can be There is no particular limitation on the thickness.
〜500 μm is used. Among these current collectors, as the positive electrode, aluminum foil having excellent oxidation resistance is used, and as the negative electrode, copper foil, nickel foil, iron, which is stable in the reduction field and has excellent electrical conductivity, and is inexpensive. It is preferred to use foils, and alloy foils containing some of them.
Further, it is preferable that the foil has a rough surface roughness of 0.2 μm Ra or more, whereby the adhesion between the positive electrode active material or the negative electrode active material and the current collector becomes excellent. Therefore, it is preferable to use an electrolytic foil because of having such a rough surface. In particular, an electrolytic foil subjected to a napping treatment is most preferable.

As the separator for a non-aqueous electrolyte battery, it is preferable to use a porous film or a nonwoven fabric exhibiting excellent rate characteristics alone or in combination. Examples of the material constituting the separator for a non-aqueous electrolyte battery include polyolefin resins represented by polyethylene, polypropylene, etc., polyester resins represented by polyethylene terephthalate, polybutylene terephthalate, etc., polyvinylidene fluoride, vinylidene fluoride-hexa. Fluoropropylene copolymer, vinylidene fluoride-perfluorovinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-fluoroethylene copolymer, fluorine Vinylidene fluoride-hexafluoroacetone copolymer, vinylidene fluoride-ethylene copolymer, vinylidene fluoride-propylene copolymer, vinylidene fluoride-trifluoropropylene copolymer, vinylidene fluoride - tetrafluoroethylene - hexafluoropropylene copolymer, vinylidene fluoride - ethylene - can be mentioned tetrafluoroethylene copolymer.

The porosity of the separator for a non-aqueous electrolyte battery is preferably 98% by volume or less from the viewpoint of strength. Further, the porosity is preferably 20% by volume or more from the viewpoint of charge and discharge characteristics.

The separator for a non-aqueous electrolyte battery uses a polymer gel composed of a polymer such as acrylonitrile, ethylene oxide, propylene oxide, methyl methacrylate, vinyl acetate, vinyl pyrrolidone, polyvinylidene fluoride and an electrolyte. Is also good.

Further, the separator for a non-aqueous electrolyte battery is as follows:
It is preferable to use a polymer gel in combination with the above-described porous membrane, nonwoven fabric, or the like, since the liquid retention of the electrolytic solution is improved.
That is, by forming a film coated with a solvent-philic polymer having a thickness of several μm or less on the surface of the polyethylene microporous membrane and the wall surface of the micropore, and holding an electrolyte solution in the micropores of the film, The polymer gels.

Examples of the above-mentioned solvent-philic polymer include polymers crosslinked with polyvinylidene fluoride, an acrylate monomer having an ethylene oxide group or an ester group, an epoxy monomer, a monomer having an isocyanate group, and the like. Upon crosslinking, an actinic ray such as ultraviolet (UV) or electron beam (EB) can be used.

For the purpose of controlling the strength and the physical properties, a physical property modifier within a range that does not hinder the formation of a crosslinked product can be blended and used in the above-mentioned solvent-philic polymer. Examples of the physical property modifier include inorganic fillers such as metal oxides such as silicon oxide, titanium oxide, aluminum oxide, magnesium oxide, zirconium oxide, zinc oxide and iron oxide, and metal carbonates such as calcium carbonate and magnesium carbonate. And polymers {polyvinylidene fluoride, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, and the like}. The amount of the physical property modifier to be added is generally 50% by weight or less, preferably 20% by weight or less, based on the crosslinkable monomer.

As an example of the acrylate monomer, a bifunctional or higher functional unsaturated monomer is preferably exemplified.
More specific examples include bifunctional (meth) acrylate ｛ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, adipic acid / dineopentyl glycol ester di (meth) acrylate, and polyethylene glycol having a degree of polymerization of 2 or more. Di (meth) acrylate, polypropylene glycol di (meth) acrylate having a degree of polymerization of 2 or more, di (meth) acrylate of polyoxyethylene / polyoxypropylene copolymer, butanediol di (meth) acrylate, hexamethylene glycol di (meth) acrylate ) Acrylate, etc., trifunctional (meth)
Acrylate: trimethylolpropane tri (meth) acrylate, glycerin tri (meth) acrylate, tri (meth) acrylate of glycerin ethylene oxide adduct, tri (meth) acrylate of glycerin propylene oxide adduct, glycerin ethylene oxide, propylene oxide addition Tri (meth) acrylate, etc.}, polyfunctional (meth) acrylate having 4 or more functional groups, pentaerythritol tetra (meth) acrylate,
And diglycerin hexa (meth) acrylate. These monomers can be used alone or in combination.

A monofunctional monomer may be added to the acrylate monomer for the purpose of adjusting physical properties. Examples of the monofunctional monomer include unsaturated carboxylic acid acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, vinylbenzoic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, methylenemalonic acid, Aconitic acid, etc., unsaturated sulfonic acid {styrene sulfonic acid, acrylamido-2-methylpropane sulfonic acid, etc.} or salts thereof (Li salt, Na salt, K salt, ammonium salt, tetraalkyl ammonium salt, etc.), and these Is partially esterified with a C1-C18 aliphatic or alicyclic alcohol, alkylene (C2-C4) glycol, polyalkylene (C2-C4) glycol (methyl malate, monohydroxyethyl monomer) Rate, etc.), and ammonia with a primary or secondary amine Those amidation (maleic acid monoamide, N- methyl maleate monoamide, N, N-
An ester of (meth) acrylic acid ester (C1-C18 aliphatic (methyl, ethyl, propyl, butyl, 2-ethylhexyl, stearyl, etc.) alcohol with (meth) acrylic acid,
Or esters of alkylene (C2-C4) glycol (ethylene glycol, propylene glycol, 1,4-butanediol, etc.) and polyalkylene (C2-C4) glycol (polyethylene glycol, polypropylene glycol) with (meth) acrylic acid]; (Meta)
Acrylamide or N-substituted (meth) acrylamide [(meth) acrylamide, N-methyl (meth) acrylamide, N-methylol (meth) acrylamide, etc.]; vinyl ester or allyl ester [vinyl acetate, allyl acetate, etc.]; vinyl ether or allyl Ether [butyl vinyl ether, dodecyl allyl ether, etc.]; unsaturated nitrile compound [(meth) acrylonitrile, crotonnitrile, etc.]; unsaturated alcohol [(meth) allyl alcohol, etc.]; unsaturated amine [(meth) allylamine, dimethylaminoethyl) (Meth) acrylate, diethylaminoethyl (meth) acrylate, etc.];
Heterocycle-containing monomer [N-vinylpyrrolidone, vinylpyridine, etc.]; olefinic aliphatic hydrocarbon [ethylene,
Propylene, butylene, isobutylene, pentene, (C
6-C50) α-olefins, etc.]; olefin-based alicyclic hydrocarbons [cyclopentene, cyclohexene, cycloheptene, norbornene, etc.]; olefin-based aromatic hydrocarbons [styrene, α-methylstyrene, stilbene, etc.];
Unsaturated imide [maleimide etc.]; halogen-containing monomer [vinyl chloride, vinylidene chloride, vinylidene fluoride, hexafluoropropylene etc.] and the like.

Examples of the epoxy monomer include glycidyl ethers such as bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, brominated bisphenol A diglycidyl ether, phenol novolac glycidyl ether, cresol novolac glycidyl ether, and glycidyl esters. Glycidyl hexahydrophthalate, glycidyl dimer, etc.｝, glycidylamines ｛triglycidyl isocyanurate, tetraglycidyldiaminophenylmethane, etc.｝, linear aliphatic epoxides ｛epoxidized polybutadiene, epoxidized soybean oil, etc.｝,
Alicyclic epoxides {3,4 epoxy-6 methylcyclohexylmethyl carboxylate, 3,4 epoxy cyclohexylmethyl carboxylate, etc.}; These epoxy resins can be used alone or after being cured by adding a curing agent.

Examples of the curing agent include aliphatic polyamines such as diethylenetriamine, triethylenetetramine, 3,9- (3-aminopropyl) -2,4,8,1.
0-tetrooxaspiro [5,5] undecane, etc., aromatic polyamines {metaxylenediamine, diaminophenylmethane, etc.}, polyamides, dimer acid polyamide, etc., acid anhydrides, phthalic anhydride, tetrahydromethyl anhydride Phthalic acid, hexahydrophthalic anhydride, trimellitic anhydride, methylnadic anhydride｝, phenols such as phenol novolak, polymercaptan ｛polysulfide, etc., tertiary amines ｛tris (dimethylaminomethyl) phenol, 2-ethyl -4-methylimidazole, etc., and a Lewis acid complex {boron trifluoride / ethylamine complex, etc.}.

Illustrative examples of the monomer having an isocyanate group include toluene diisocyanate, diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate, and 2,2,4 (2,2,4) -trimethyl-hexamate. Methylene diisocyanate, p-phenylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 3,3'-dimethyldiphenyl 4,4'-diisocyanate, dianisidine diisocyanate, m-xylene diisocyanate Nate, trimethyl xylene diisocyanate, isophorone diisocyanate, 1,5-naphthalenedi isocyanate, trans
-1,4-cyclohexyl diisocyanate, lysine diisocyanate and the like.

In crosslinking the monomer having an isocyanate group, polyols and polyamines [bifunctional compounds {water, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, etc.}, trifunctional compounds} glycerin, trimethylolpropane , 1,2,6-hexanetriol, triethanolamine, etc., tetrafunctional compounds {pentaerythritol, ethylenediamine, tolylenediamine, diphenylmethanediamine, tetramethylolcyclohexane,
Methyl glucoside, etc.｝ pentafunctional compound ｛2,2,6,6
-Tetrakis (hydroxymethyl) cyclohexanol, diethylenetriamine and the like {, 6-functional compound {sorbitol, mannitol, dulcitol, etc.}, 8-functional compound {sucrose, etc.}], and polyether polyols {propylene oxide and / or the polyol or polyamine) An ethylene oxide adduct {, a polyester polyol [condensation product of the polyol and a polybasic acid {adipic acid, o, m, p-phthalic acid, succinic acid, azelaic acid, sebacic acid, ricinoleic acid};
Compounds having active hydrogen can be used in combination, such as polycaprolactone polyol {poly-ε-caprolactone, etc.}, polycondensates of hydroxycarboxylic acids, etc.].

In the crosslinking reaction, a catalyst can be used in combination. Examples of the catalyst include organotin compounds, trialkylphosphines, amines [monoamines {N, N-dimethylcyclohexylamine, triethylamine, etc.}, cyclic monoamines} pyridine, N
-Methylmorpholine, etc., diamines {N, N, N ',
N'-tetramethylethylenediamine, N, N, N ',
N'-tetramethyl 1,3-butanediamine, etc., triamines {N, N, N ', N'-pentamethyldiethylenetriamine, etc.}, hexamines {N, N, N'N'-
Tetra (3-dimethylaminopropyl) -methanediamine, etc., cyclic polyamines, diazabicyclooctane (DABCO), N, N′-dimethylpiperazine, 1,
2-dimethylimidazole, 1,8-diazabicyclo (5,4,0) undecene-7 (DBU) and the like, and salts thereof.

In the non-aqueous electrolyte battery according to the present invention, the electrolyte is injected before or after laminating the non-aqueous electrolyte battery separator, the positive electrode and the negative electrode, and finally,
It is suitably manufactured by sealing with an exterior material. Further, in a non-aqueous electrolyte battery in which a positive electrode and a negative electrode are wound around a power generating element stacked with a non-aqueous electrolyte battery separator interposed therebetween, the electrolyte is injected into the power generating element before and after the winding. Is preferred. As the liquid injection method, it is possible to inject liquid at normal pressure, but a vacuum impregnation method or a pressure impregnation method can also be used.

As the exterior material, a thin material is preferable from the viewpoint of reducing the weight of the nonaqueous electrolyte battery. For example, a metal-resin composite film in which a metal foil is sandwiched between resin films is preferable. Specific examples of the metal foil include aluminum,
Iron, nickel, copper, stainless steel, titanium, gold, silver, etc.
There is no limitation as long as the foil has no pinhole, but a lightweight and inexpensive aluminum foil is preferred. As the resin film on the outside of the battery, a resin film having excellent piercing strength such as a polyethylene terephthalate film or a nylon film can be used, and as the resin film on the inside of the battery, a polyethylene film or a nylon film can be used. It is preferable to use a film that has a solvent resistance.

[0048]

Example (Experiment 1: Adhesion test to negative electrode current collector)
Styrene-butadiene rubber having a gel content of 60% by weight or more and a ratio of styrene to butadiene of 7: 3 was used. The carboxymethylcellulose metal salt has a viscosity in the range of 15 to 400 Pa · s when 1% by weight is dispersed in water among samples commercially available from various companies, and has various etherification degrees. What had it was used. here,
The value of the degree of etherification is not strictly determined, and is often defined with a certain range. However, in the description in the following examples, the range of the degree of etherification indicated for each sample is described. The median value or representative value was used.

The carbonaceous material has a lattice spacing d ₀₀₂ of 0.3
35 nm, crystallite size Lc in the c-axis direction is 100 nm
As described above, artificial graphite having a bulk density of 1.0 g / cm ³ was used.

An appropriate amount of water is added to 97 parts by weight of the artificial graphite, 2 parts by weight (dry weight) of styrene-butadiene rubber and 1 part by weight (dry weight) of sodium salt of carboxymethylcellulose, and the mixture is kneaded. It was adjusted. After applying the slurry to one surface of an electrolytic copper foil having a thickness of 12 μm, air-drying, and then applying the same to the other surface,
It dried at 130 degreeC under reduced pressure for 12 hours, and obtained the negative electrode plate.

The Japanese Industrial Standard JIS K5400 (199)
The negative electrode plate was evaluated for adhesion of the carbonaceous material coating film formed on the negative electrode current collector in accordance with the “cross-cut method”, which is a coating film adhesion test method specified in “0th edition”. The number of samples was set to n = 10, and the evaluation score was obtained in accordance with the evaluation standard defined in the above standard.

FIG. 1 shows the relationship between the value of the degree of etherification of the metal salt of carboxymethylcellulose used for the negative electrode and the average value of the evaluation scores obtained by the grid method. From these results, it is found that when carboxymethylcellulose having a degree of etherification of greater than 0.65 is used, good adhesion to the negative electrode current collector can be obtained.

(Experiment 2: Evaluation of Peeling Resistance to Press Roll) The negative electrode plate was passed between two stainless steel rolls and roll-pressed. At this time, depending on the negative electrode plate, the carbonaceous material coating film was peeled off from the negative electrode current collector and attached to the roll side. Regarding the negative electrode using the carboxymethylcellulose metal salt having various degrees of etherification described above, ten roll press samples were cut out from one type of negative electrode, and the presence or absence of peeling from the negative electrode current collector was examined. Summarized in Here, “○” indicates that no peeling from the negative electrode current collector occurred for all 10 sheets, and “X” indicates that one or more peels from the negative electrode current collector occurred.

[0054]

[Table 1]

From this result, it was found that the value of the degree of etherification was 0.9.
It was found that the negative electrode using a carboxymethylcellulose metal salt of less than 5 had sufficient peeling resistance from the negative electrode current collector to roll pressing.

(Experiment 3: High Rate Discharge Characteristics Test) In order to examine the electrochemical characteristics of the negative electrode plate after the roll pressing, a single-pole three-terminal cell provided with a reference electrode was prepared. For the negative electrode using carboxymethylcellulose having a degree of etherification of 0.95 or more, a portion where the adhesion to the roll side did not occur was selected and used in this experiment. Lithium metal was used for both the reference electrode and the counter electrode. The working area of the working electrode made of the negative electrode plate was 2.25 cm ² . The electrolytic solution was prepared by mixing ethylene carbonate and γ-butyrolactone at a volume ratio of 3: 7, and adding lithium tetrafluoroborate to the mixture.
The solution dissolved at a concentration of mol / l was used.

Using the three-terminal cell, doping and undoping of lithium ions was repeated for the working electrode.
The doping was performed by flowing a constant current of 1 mA between the working electrode and the counter electrode until the potential of the working electrode dropped to 30 mV. The undoping was performed by flowing a constant current of 1 mA or 10 mA between the working electrode and the counter electrode until the potential of the working electrode increased to 1000 mV. A current value of 1 mA corresponds to 0.2 It (5 hour rate) with respect to the negative electrode plate of the working electrode, and a current value of 10 mA corresponds to 2.0 It (0.5 hour) with respect to the negative electrode plate of the working electrode. Rate).

When a constant current value of 1 mA is used as the undoping current, the amount of undoped electricity is defined as C1, and the amount of undoping is 10 mA.
The amount of undoped electricity when the constant current value of is used is C2,
The ratio of C2 to C1 (C2 / C1) was taken as the high rate discharge characteristic value. The high-rate discharge characteristic values for each type of negative electrode plate were determined and arranged in relation to the degree of etherification of the carboxymethyl cellulose metal salt used for the negative electrode, and are shown in FIG. From this result, it was found that a negative electrode using a carboxymethylcellulose metal salt having a degree of etherification of greater than 0.70 can obtain a good high-rate discharge characteristic value.

(Confirmation of Performance in Nonaqueous Electrolyte Battery) 90% by weight of LiCoO ₂ as a positive electrode active material, 5% by weight of acetylene black as a conductive agent and 5% by weight of polyvinylidene fluoride as a binder were mixed, and N-methylpyrrolidone was mixed. And kneaded using The obtained paste was applied on an aluminum foil, dried and pressed to prepare a positive electrode plate. The positive electrode terminal was welded to the positive electrode plate by ultrasonic welding.

The negative electrode plate was prepared by the method described in Experiment 2. However, the degree of etherification of the metal salt of carboxymethyl cellulose was 0.85. On the negative electrode plate,
The negative electrode terminal was welded by resistance welding.

A separator is made of a polypropylene microporous membrane whose surface has been modified with polyacrylate to improve the retention of the electrolyte, and is laminated in the order of negative electrode / separator / positive electrode and wound in a flat shape to form an electrode as a power generation element. A group was obtained.

A metal resin composite film composed of polyethylene terephthalate (15 μm) / aluminum foil (50 μm) / metal adhesive polypropylene film (50 μm) is used as the outer package, and the open ends of the positive electrode terminal and the negative electrode terminal are exposed outside. As described above, airtight sealing was performed except for the portion that became a liquid injection hole.

An electrolyte obtained by dissolving lithium tetrafluoroborate at a concentration of 2 mol / l in a mixture of ethylene carbonate and γ-butyrolactone at a volume ratio of 3: 7 was supplied through the injection hole at 1333 Pa. After the injection under a reduced pressure atmosphere, the injection hole portion was heat-sealed under the same reduced pressure atmosphere of 1333 Pa to produce a large number of flat nonaqueous electrolyte batteries having a designed capacity of 570 mAh.

A charge / discharge cycle test was performed on these non-aqueous electrolyte batteries. Charging was performed at a constant current and constant voltage of 60 mA and 4.2 V, and discharging was performed at a constant current of 60 mA and a final voltage of 3 V. The results are shown in FIG. from this result,
Without the negative electrode active material swelling and causing performance degradation,
It was confirmed that a battery with excellent performance with small capacity reduction even after long-term repeated charge / discharge could be provided.

[0065]

According to the present invention, as described in claim 1, a carbonaceous material capable of inserting and extracting lithium ions,
In a nonaqueous electrolyte battery including a negative electrode having a binder and a current collector, a positive electrode, and a nonaqueous electrolyte, the binder contains a carboxymethylcellulose metal salt and a butadiene-containing rubber, and the carboxymethylcellulose metal salt Since the value of the degree of etherification is characterized by being greater than 0.65, the adhesion to the negative electrode current collector becomes good, and the carbonaceous material does not fall off in the cutting step or the winding step of the negative electrode, A high-performance non-aqueous electrolyte battery can be provided, in which good high-rate discharge characteristics are obtained, and the electrodes do not swell in the electrolytic solution to deteriorate the performance.

Further, according to the present invention, as described in claim 2, the value of the degree of etherification is less than 0.95, so that the carbonaceous material is reduced in the roll pressing step of the negative electrode. A negative electrode with high production efficiency can be provided without peeling.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the value of the degree of etherification of a metal salt of carboxymethyl cellulose and the adhesion strength to a negative electrode current collector.

FIG. 2 is a graph showing a relationship between a value of a degree of etherification of a metal salt of carboxymethyl cellulose and a high-rate discharge characteristic of a negative electrode.

FIG. 3 is a graph showing the charge / discharge cycle performance of the battery of the present invention.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenji Kono 2-3-1-21, Kosobe-cho, Takatsuki-shi, Osaka Inside Yuasa Corporation (72) Inventor Taizo Harada 2-3-1, Furuso-cho, Takatsuki-shi, Osaka No. F-term in Yuasa Corporation (reference) DA11 EA21 EA23 HA00

Claims (2)

[Claims] 1. A non-aqueous electrolyte battery comprising a negative electrode having a carbonaceous material capable of inserting and extracting lithium ions, a binder and a current collector, a positive electrode, and a non-aqueous electrolyte, wherein the binder is carboxy. A nonaqueous electrolyte battery comprising a methylcellulose metal salt and a butadiene-containing rubber, wherein the carboxymethylcellulose metal salt has a degree of etherification of greater than 0.65. 2. The non-aqueous electrolyte battery according to claim 1, wherein the value of the degree of etherification is less than 0.95.