JP2001210367A - Nonaqueous electrolyte battery and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-weight and inexpensive battery in which especially a reliability concerning the encapsulation of package type battery is enhanced and in which a reduced pressure process is simplified, and which is superior in a long term reliability. SOLUTION: As a salt of electrolyte, LiBF4 is used, and as solvents, ethylene carbonate, γ-butyrolactone, propylene carbonate and aliphatic esters with the boiling point not less than 150 deg.C at the normal pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte battery and a method for producing the same, and more particularly to an electrolyte composition for a non-aqueous electrolyte battery.

[0002]

2. Description of the Related Art Recent portable devices are required to be lightweight and small in size, as represented by portable telephones. A battery as a power source in the portable device is also required to be reduced in size, weight, and thickness, and a battery having a high energy density is strongly demanded.

On the other hand, particularly in the case of a non-aqueous electrolyte battery, as an electrochemically active substance, those utilizing intercalation or doping of a layered compound have been particularly studied. Performance is expected. For example, an example in which graphite is used as an electrochemically active material for the negative electrode has also emerged as a solution to problems such as cycle characteristics of the electrochemically active material. This graphite is characterized by a high doping capacity, a low self-discharge rate, excellent cycling properties, and most notably, a base potential very close to lithium metal. That is, in the case of a lithium ion battery as a non-aqueous electrolyte battery that achieves the above-described object,
For example, a lithium-containing transition metal oxide or the like for the positive electrode, a carbonaceous material such as graphite for the negative electrode, an electrolyte in which LiPF ₆ or the like is dissolved in a solvent such as ethylene carbonate for the electrolyte, and a metal can for the exterior material are used. . It is known that LiPF ₆ used in this electrolyte reacts with a trace amount of water present inside the battery to release hydrofluoric acid.
For this reason, metal such as nickel-plated iron or stainless steel or aluminum or the like for the purpose of weight reduction is used for the metal can used for the exterior material so that water from the outside is not mixed. In order to further reduce the weight, use of a metal-resin composite including a gold foil and a resin film as an exterior material has been studied.

However, if ethylene carbonate is used as the main solvent of the electrolytic solution, there is a problem in low-temperature characteristics. That is, since the melting point of ethylene carbonate is as high as 37 ° C., the electrolyte is easily coagulated at a low temperature. Therefore, for the purpose of improving the low-temperature characteristics, Japanese Patent No. 280,365 proposes a mixed solvent of ethylene carbonate, propylene carbonate, and γ-butyrolactone. JP-A-5-242910 proposes mixing ethylene carbonate, propylene carbonate, γ-butyrolactone and the like with a chain ester having a boiling point of less than 150 ° C. such as dimethyl carbonate, methyl propionate, and n-methyl butyrate. Has been made.

[0005]

In a non-aqueous electrolyte battery using a metal-resin composite material as an exterior material, the sealing property of the exterior material is an important issue. As the metal foil used for the metal-resin composite material, a lightweight and inexpensive aluminum foil is usually used. Aluminum is vulnerable to acids, especially volatile acids (such as hydrofluoric acid). When these acids reach the metal foil, peeling occurs at the interface between the metal foil and the resin film,
There is a problem that a problem occurs in long-term reliability of the battery.
That is, it is considered that hydrofluoric acid released by the reaction between LiPF ₆ and water permeates the resin film of the battery package material and causes corrosion on the surface of the metal foil, so that the metal foil and the resin film are peeled off. As the peeling of the metal foil and the resin film progresses, the sealing property of the battery deteriorates, and the mixing of moisture is further promoted.

That is, a first object of the present invention is to solve the above-mentioned problem relating to corrosion of a metal battery case, and particularly to a battery using a metal-resin composite material as an exterior material, has excellent sealing properties and excellent long-term reliability. Another object of the present invention is to provide a lightweight battery.

[0007] Further, during the manufacturing process, a vacuum injection step of introducing an electrolytic solution into the power generating element portion, a vacuum impregnating step of impregnating the electrolytic solution into the pores of the electrodes and the separator, or a vacuum sealing step of sealing the exterior material are performed. If it has, when a chain ester having a boiling point of less than 150 ° C. is mixed with the electrolytic solution, the low boiling point component of the electrolytic solution volatilizes and the electrolytic solution composition changes, or the electrolytic solution causes bumping, and the scattered droplets are sealed. Part was contaminated, and sufficient sealing strength was not obtained in some cases. In order to prevent this, for example, in the vacuum injection step, a plurality of tubes with a valve were installed in the battery case, the inside of the battery case was evacuated before the introduction of the electrolyte, and the valve was switched to introduce the electrolyte. In the vacuum impregnation process, it is necessary to perform a series of operations such as releasing the decompression, and in the vacuum impregnation process, it is necessary to perform an operation such as gradually increasing or decreasing the degree of vacuum by a series of programmed valve operations. There was such a problem.

That is, a second object of the present invention is to provide a simple manufacturing method while maintaining good low-temperature performance of a lithium battery, and to reduce the manufacturing cost.

[0009]

In order to achieve the above object, the present invention provides a battery using at least LiBF ₄ as an electrolyte salt, wherein the solvent is ethylene carbonate, γ-
A nonaqueous electrolyte battery comprising at least butyrolactone, propylene carbonate, and a chain ester, wherein the chain ester has a boiling point of 150 ° C. or higher at normal pressure. Further, the non-aqueous electrolyte battery in which the exterior material is a metal-resin composite film. Further, the method includes at least one or more decompression processing steps, and the degree of vacuum in the decompression processing step is one.
A method for manufacturing a nonaqueous electrolyte battery, wherein the pressure is in the range of 333 Pa to 13332 Pa.

That is, LiPF ₆ is highly reactive with a trace amount of water and easily generates hydrofluoric acid which is highly corrosive to metals.
Li, which is known not to react with water without using
By using BF ₄ as the electrolyte salt, the above-mentioned problem relating to corrosion can be solved, so that long-term reliability can be obtained without deterioration in sealing performance even in long-term use. The concentration of LiBF ₄ dissolved in the electrolytic solution is arbitrary. This effect is particularly remarkable when a metal-resin composite film, which is greatly affected by corrosion, is applied to a battery using an exterior material.

In addition, by using a chain ester having a boiling point of 150 ° C. or more without using a chain ester having a boiling point of less than 150 ° C., electrolysis can be performed even in a vacuum atmosphere used for a vacuum treatment step such as vacuum impregnation or vacuum sealing. There is no bumping or splashing of the liquid, and volatilization of the solvent is minimized. Therefore,
The apparatus used for the decompression process does not require a complicated series of valve operations and the like, and can be replaced with an extremely simple apparatus. Examples of the chain ester that can be used in the present invention include methyl n-caproate (boiling point 151 ° C.), ethyl n-caproate (boiling point 168 ° C.), methyl n-caprylate (boiling point 194-195 ° C.), Ethyl caprylate (bp 207 ° C), methyl n-caprate (bp 24
0 ° C.), ethyl n-caprate (boiling point 245 ° C.), methyl linoleate (boiling point about 370 ° C.), methyl benzoate (boiling point 198 ° C.), methyl bromoacetate (boiling point about 160 ° C.),
Methyl 2-bromopropionate (boiling point about 155 ° C), 2
-Methyl bromobutyrate (boiling point: about 230 ° C.), but is not limited thereto, and the selection thereof and the mixing ratio with the electrolytic solution are arbitrary. Further, two or more of these chain esters may be used as a mixture.

When the above electrolyte composition of the present invention is applied to a battery using a metal-resin composite film as an exterior material, more remarkable effects are recognized in addition to the above effects. That is, a battery using a chain ester having a boiling point of 150 ° C. or higher has a small amount of the organic solvent that permeates the resin in the sealing portion and escapes from the battery system, and can provide a battery with excellent long-term reliability.

By setting the degree of vacuum in the decompression treatment step to a higher vacuum side than 13332 Pa, the injection and impregnation of the electrolytic solution becomes sufficient. In addition, by setting the vacuum side lower than 1333 Pa, the effect of preventing volatilization and bumping of the solvent component of the electrolytic solution is sufficiently exhibited. Therefore, the degree of vacuum in the decompression process is set to 1
By setting it in the range of 333 Pa to 13332 Pa, the effects of the present invention can be maximized. Further, when the metal-resin composite film is applied to a battery using as an exterior material, in addition to the above-described effects, contamination of a sealing portion due to scattering of an electrolytic solution or the like can be prevented, so that sufficient sealing strength can be obtained.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is not limited by the following description. FIG. 1 is a front view showing an example of the embodiment of the present invention, and FIG. 2 is a cross-sectional view of a terminal portion in a portion A of the battery of FIG. It comprises a positive electrode current collector 1, a positive electrode 2, a separator 3, a negative electrode 4, a negative electrode current collector 5, a metal-resin composite 6, and a terminal 7.

The separator 3 used in the nonaqueous electrolyte battery of the present invention is preferably made of a porous material in order to exhibit excellent rate characteristics. Examples of the material constituting the porous body include fluororesins, polyolefins represented by polyethylene and polypropylene, polyesters represented by polyethylene terephthalate and polybutylene terephthalate, polyphenylene sulfite, polyimide, polyacrylonitrile, and polymethyl methacrylate. Is mentioned.

It is preferable that the porous body has good wettability with an electrolytic solution. If the wettability is poor, it is preferable to perform a treatment with a surfactant or the like. Among the above materials, fluororesins and the like are preferable because of their excellent wettability with an electrolytic solution. As the fluororesin, polyvinylidene fluoride or a copolymer containing vinylidene fluoride is preferable. Copolymers containing polyvinylidene fluoride or vinylidene fluoride are homopolymers, copolymers obtained by emulsion polymerization or suspension polymerization,
It is possible to use a block copolymer or the like. For example, vinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-perfluorovinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, Vinylidene fluoride-fluoroethylene copolymer, vinylidene fluoride-hexafluoroacetone copolymer, vinylidene fluoride-ethylene copolymer, vinylidene fluoride-propylene copolymer, vinylidene fluoride-trifluoropropylene copolymer, Examples thereof include vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer and vinylidene fluoride-ethylene-tetrafluoroethylene copolymer. These can be used alone or as a mixture, or further, mixed with a polymer other than the above fluororesin. A polymer having a cross-linking site in a polymer other than the above fluoride can also be used. However, from the viewpoint of solvent resistance after crosslinking, the content of vinylidene fluoride is preferably 50% by weight or more. More preferably 75% by weight
Or more, and most preferably 95% or more.

Further, for the purpose of improving the tensile strength of the separator 3, another porous film or a fibrous material is bonded to the porous body. An equivalent measure may be taken to embed it inside. As the porous film or fibrous material, polyolefins represented by polyethylene and polypropylene, polyesters represented by polyethylene terephthalate and polybutylene terephthalate, polyphenylene sulfide, polyimide, glass and the like are preferable. Among them, the polyester nonwoven fabric is preferable from the viewpoints of impregnation of the electrolyte, ease of fusion, and cost. The thickness of the nonwoven fabric is preferably thin from the viewpoint of energy density. That is, the thickness is 50 μm or less, preferably 30 μm or less. Further, the basis weight of the nonwoven fabric is preferably 20 g / m ² or less from the viewpoint of the holding amount of the porous material or fibrous material to be embedded. Further, from the viewpoint of strength, 5 g / m ² or more is preferable. further,
For the purpose of improving the tensile strength, a cloth or a nonwoven fabric having a straight-line weft arrangement can be used.

The porosity of the separator 3 used in the battery of the present invention 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.

Lithium in the electrolyte in the battery of the present invention
LiBF as salt_FourIs preferable, and furthermore, for low temperature characteristics.
LiBF_FourCan be used in combination with other salts
Noh. For example, LiClO_Four, LiAsF₆, Li
PF₆ , LiCF_Three SO_Three , LiCF_Three CO_Two , LiS
CN, LiBr, LiI, Li_TwoSO_Four, Li_Two B_TenCl
_Ten, NaClO_Four , NaI, NaSCN, NaBr, K
ClO_Four , KSCN, etc., one of Li, Na, or K
Seed-containing inorganic ion salt, LiN (CF_ThreeSO_Two) _Two, Li
N (C_TwoF_FiveSO_Two)_Two, (CH_Three)_Four NBF_Four , (CH
_Three )_Four NBr, (C_Two H_Five )_Four NCLO_Four, (C_Two H
_Five )_Four NI, (C_Three H₇ )_FourNBr, (n-C_Four H₉ )
_Four NCLO_Four , (N-C_FourH₉ )_Four NI, (C_Two H_Five )_Four
 N-maleate, (C_Two H_Five )_Four N-benzo
ate, (C_Two H_Five )_FourQuaternary such as N-phthalate
Ammonium salt, lithium stearyl sulfonate, octane
Lithium tylsulfonate, dodecylbenzenesulfonic acid
Organic ion salts such as lithium are exemplified.

The organic solvent for dissolving LiBF ₄ is at least ethylene carbonate, propylene carbonate,
It is a mixed solvent containing γ-butyrolactone and a chain ester. That is, a high-boiling-point mixed solvent composed of ethylene carbonate, propylene carbonate, and γ-butyrolactone is preferable because it has excellent battery characteristics and low volatility of the electrolyte. Further, the boiling point is 150 ° C (normal pressure: 101080 Pa)
Mixing the above-mentioned high boiling chain ester is preferable in that low-temperature characteristics are improved. As a chain ester, methyl ester has excellent potential resistance and is excellent. Examples of the chain ester used in the present invention include methyl n-caproate (boiling point 151 ° C.) and ethyl n-caproate (boiling point 168).
° C), n-methyl caprylate (bp 194-195)
° C), ethyl n-caprylate (boiling point 207 ° C), methyl n-caprate (boiling point about 240 ° C), ethyl n-caprate (boiling point 245 ° C), methyl linoleate (boiling point about 37 ° C)
0 ° C.), methyl benzoate (boiling point: 198 ° C.), methyl bromoacetate (boiling point: about 160 ° C.), methyl 2-bromopropionate (boiling point: about 155 ° C.), methyl 2-bromobutyrate (boiling point: about 230 ° C.), and the like. However, the present invention is not limited to these. The mixing ratio of these solvents is not particularly limited, but each of ethylene carbonate, γ-butyrolactone and propylene carbonate is at least 10% by volume.
% By volume or less, and 1% by volume or more
0 vol% or less is preferable.

Further, cyclic carbonates such as butylene carbonate, chloroethylene carbonate and vinylene carbonate; cyclic esters such as γ-valerolactone; tetrahydrofuran or derivatives thereof, 1,3-dioxane, 1,2-dimethoxyethane, methyldiglyme Ethers such as acetonitrile and benzonitrile; dioxalane or a derivative thereof; sulfolane, sultone or a derivative thereof alone or a mixture of two or more thereof can also be added. However, it is not limited to these. By adding such an organic solvent, battery characteristics such as cycle characteristics and stability can be improved.

The electrolytic solution may be injected after the separator is sandwiched between the electrodes and laminated or wound up. As the liquid injection method, liquid injection may be performed at normal pressure, but it is preferable to perform liquid injection under vacuum. As the vacuum injection, various methods are possible, such as a method in which an electrolyte is injected into a previously evacuated battery and the pressure is returned to normal pressure. As the vacuum impregnation, various methods are possible, such as a method of injecting a liquid under normal pressure in advance and then applying a vacuum. In these cases, the degree of vacuum is preferably 13332 Pa or less from the viewpoint of speeding up the impregnation by vacuum. Also,
From the viewpoint of suppressing the volatility of the solvent of the electrolytic solution, a degree of vacuum of 1333 Pa or more is desirable. Further, a pressure impregnation method may be used for the purpose of increasing the impregnation speed.

The lithium-containing transition metal oxide used in the positive electrode of the present invention includes a general formula Li _y MO ₂ , Li _y
Mn _2-x M _X O ₄ (M is one or more metal elements of groups I to VIII, for example, Li, Ca, Cr, Ni, Fe, Co)
And the like. Here, the x value indicating the replacement amount of the different element is effective up to the maximum replaceable amount, but from the viewpoint of discharge capacity, 0 ≦ x ≦ 1 is preferable. As for the y value indicating the amount of lithium, the maximum amount capable of reversibly using lithium is effective, but from the viewpoint of discharge capacity, 0 ≦ y ≦ 2
Is preferred. ) And the like, but are not limited thereto.

The lithium-containing transition metal oxide is
Other active materials may be mixed and used. For example, CuO,
Cu_TwoO, Ag_Two O, CuS, CuSO_FourI family gold
Genus compound, TiS_Two , SiO_TwoGroup IV metals such as SnO and SnO
Compound, V_Two O_Five , V₆ O₁₂, VO_x, Nb_TwoO_Five , B
i_Two O_Three , Sb_Two O_ThreeGroup V metal compounds such as CrO_Three,
Cr_Two O_Three, MoO_Three , MoS_Two, WO_Three , SeO_Two What
Which group VI metal compound, MnO_Two , Mn_Two O_Three Such as VII
Group metal compound, Fe_Two O_Three , FeO, Fe_Three O _Four , Fe
PO_Four, Ni_Two O_Three , NiO, CoO_Three , CoO, etc.
It is represented by a group III metal compound or the like. In addition, disulfi
De, polypyrrole, polyaniline, polyparaphenylene
Conductive materials such as polystyrene, polyacetylene and polyacene materials
Molecular compounds, pseudo-graphite structure carbonaceous materials, etc.
However, the present invention is not limited to these.

The material of the negative electrode is not particularly limited, but a graphite material is preferred from the viewpoint of avoiding decomposition of propylene carbonate used for the electrolyte solvent. For example, those having the following physical properties may be mentioned.
It is not limited to these ranges. Analysis results by X-ray diffraction or the like; Lattice spacing (d ₀₀₂ ) 3.33 to 3.50 ° Size of crystallite in a-axis direction La 200 ° or more Size of crystallite in c-axis direction Lc 200 ° or more True density 2. 00 to 2.25 g / cm ³

Furthermore, it is also possible to add a metal oxide such as tin oxide or silicon oxide to the graphite material, or to add phosphorus or boron to perform reforming. Also, graphite and lithium metal, lithium-aluminum,
By using lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium, or an alloy containing a lithium metal such as a wood alloy in combination, or by electrochemically reducing the carbonaceous material used in the present invention, It is also possible to insert lithium in the material in advance.

Further, at least the surface layer portion of the positive and negative electrode active material powders has good electron conductivity and ion conductivity.
Alternatively, it can be modified with a compound having a hydrophobic group. For example, gold, silver, carbon, nickel, copper,
Plating, sintering, mechanofusion, etc. of a substance having good electron conductivity such as amorphous carbon, a substance having good ion conductivity such as lithium carbonate, boron glass and solid electrolyte, or a substance having a hydrophobic group such as silicone oil, Coating by applying techniques such as vapor deposition and baking.
In the case of using graphite as the negative electrode active material, it is desirable to modify the surface of the particles with amorphous carbon because decomposition of propylene carbonate can be suppressed.

It is desirable that the electrochemically active substance used in the present invention has an average particle size of 100 μm or less. In particular, the electrochemically active substance used for the positive electrode is desirably 10 μm or less for the purpose of improving high output characteristics. In order to obtain a powder having a predetermined shape, a pulverizer, a classifier, or the like can be used. For example, mortar, ball mill, sand mill, vibration ball mill, planetary ball mill, jet mill,
A counter jet mill, a swirling air jet mill, a sieve, or the like is 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 method for coating the positive electrode and the negative electrode of the present invention may be, for example, a roller coating such as an applicator roll, a screen coating, a doctor blade method, a spin coating, a bar coder, or any other means. It is desirable, but not limited to, to apply to the shape.However, when these means are used, it is possible to increase the actual surface area of the electrochemically active substance in contact with the electrolyte layer and the current collector. is there.

A conductive agent, a binder, a filler, and the like can be added to the electrode mixture of the positive electrode and the negative electrode as needed. Any conductive material may be used as long as it does not adversely affect battery performance. Usually, natural graphite (scale graphite,
Flake graphite, earthy graphite, etc.), artificial graphite, carbon black, acetylene black, Ketjen black, carbon whiskers, carbon fiber and metal (copper, nickel, aluminum, silver, gold, etc.) powder, metal fiber, conductive ceramics A conductive material such as a material can be included as one type or a mixture thereof. Among these, acetylene black is desirable from the viewpoint of conductivity and coatability. The addition amount is preferably 1 to 50% by weight, particularly preferably 2 to 30% by weight. These mixing methods are physical mixing, and ideally, uniform mixing. Therefore, V-type mixer, S-type mixer, grinder, ball mill,
It is possible to mix a powder mixer such as a planetary ball mill in a dry or wet manner.

Examples of the binder include tetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, ethylene-propylene diene terpolymer (E
Thermoplastic resins such as PDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, carboxymethylcellulose, etc., polymers having rubber elasticity, polysaccharides and the like can be used as one kind or as a mixture of two or more kinds. Further, it is preferable that a binder having a functional group that reacts with lithium, such as a polysaccharide, be deactivated by a method such as methylation. The addition amount is preferably 1 to 50% by weight, and
~ 30% by weight is preferred.

As the filler, any material may be used as long as it does not adversely affect battery performance. Examples include olefin polymers such as polypropylene and polyethylene, aerosil, zeolite, glass, carbon, and the like. The addition amount of the filler is preferably 0 to 30% by weight.

The current collector of the electrochemically active substance may be any current collector that does not adversely affect the battery. For example, as the current collector for the positive electrode, in addition to aluminum, titanium, stainless steel, nickel, calcined carbon, conductive polymer, conductive glass, and the like, for the purpose of improving adhesiveness, conductivity, and oxidation resistance, aluminum And the surface of copper or the like treated with carbon, nickel, titanium, silver or the like can be used. Examples of the current collector for the negative electrode include copper, nickel, iron, stainless steel, titanium, aluminum, calcined carbon, conductive polymer, conductive glass, and Al-Cd alloy, as well as adhesiveness, conductivity, and oxidation resistance. For the purpose of improving the properties, a product 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. As these shapes, in addition to the foil shape, a film shape, a sheet shape, a net shape, a punched or expanded material, a lath body, a porous body, a foamed body, a formed body of a fiber group, and the like are used. The thickness is not particularly limited, but a thickness of 1 to 500 μm is used.
Among these current collectors, the positive electrode is an aluminum foil having excellent oxidation resistance, and the negative electrode is stable in a reduction field, and has excellent electrical conductivity, and is inexpensive copper foil, nickel foil, iron foil, And alloy foils containing some of them. Further, it is desirable that the foil having a rough surface roughness of 0.2 μmRa or more, which has excellent adhesion between the electrochemically active material layer and the current collector, is used. Electrolytic foils are excellent for obtaining such a rough surface. Particularly, an electrolytic foil subjected to a napping treatment is most preferable.

As the exterior material, a metal-resin composite of a metal foil and a resin film is preferable from the viewpoint of weight energy density. Examples of the metal foil include aluminum, iron, nickel, copper, SUS, titanium, gold, silver, and any other foil having no pinhole, but a lightweight and inexpensive aluminum foil is preferable. In addition, as the resin film, a resin film having excellent piercing strength such as a polyethylene terephthalate film or a nylon film is used on one or more layers on the outer surface, and a thermoplastic film such as a polyethylene film or a nylon film is used on the inner surface and can be fused. It is preferable to use one or more films. From the viewpoint of solvent resistance, it is desirable to seal the opening of such a resin film with a thermoplastic resin. Furthermore, for the purpose of suppressing battery swelling and improving the adhesion of the electrodes, it is desirable to perform vacuum sealing in a vacuum.

[0035]

The present invention will be described below in more detail with reference to examples.

(Battery 1 of the Present Invention) A nonaqueous electrolyte battery of the present invention was prepared according to the following procedure. The positive electrode 2 was produced as follows. LiCoO as positive electrode active material
₂ was mixed with acetylene black as a conductive agent and polyvinylidene fluoride as a binder at a weight ratio of 90: 5: 5, and then a positive electrode slurry of the above material was prepared using N-methylpyrrolidone as a solvent. The obtained slurry was applied to both sides of a 20 μm aluminum foil, and N-methylpyrrolidone was removed by drying. This positive electrode plate was pressed by a roll press to obtain a positive electrode 2.

The negative electrode 4 was manufactured as follows. As a negative electrode active material, graphite whose surface is modified with amorphous carbon is mixed with polyvinylidene fluoride at a weight ratio of 95: 5, and then mixed with N-methylpyrrolidone as a solvent. Was prepared. The obtained slurry was applied to both sides of the electrolytic copper foil, and N-methylpyrrolidone was removed by drying. This negative electrode plate was pressed by a roll press to obtain a negative electrode 4.

The separator 3 was manufactured as follows.
Polyethylene terephthalate non-woven fabric (thickness 27μ)
In m), a liquid obtained by dissolving 12 parts by weight of polyvinylidene fluoride and 8 parts by weight of dibutyl phthalate as a plasticizer in 80 parts by weight of N-methylpyrrolidone as a solvent was embedded on release paper. Then, it was immersed in a 1M aqueous solution of lithium hydroxide for coagulation and insolubilization. After drying, excess lithium hydroxide was removed by washing with water. After further vacuum drying at 150 ° C., carbon dioxide gas was injected to return to normal pressure (carbonation treatment). As described above, a thickness of 30 μm and a porosity of about 70
% Separator 3 was obtained.

The negative electrode 4, the separator 3, and the positive electrode 2 were brought into contact by lamination. An aluminum terminal (width 5)
mm, thickness 100 μm) and a nickel terminal (width 5 mm, thickness 100 μm) were connected to the negative electrode 4 by electric resistance welding. After arranging the electrode group on the exterior material 6 made of a cylindrical metal resin composite (polyethylene terephthalate / aluminum foil / modified polypropylene), 20 parts by weight of lithium tetrafluoroborate, 40 parts by weight of ethylene carbonate,
A non-aqueous electrolyte solution obtained by mixing 40 parts by weight of γ-butyrolactone, 20 parts by weight of propylene carbonate, and 5 parts by weight of methyl n-caproate was injected at a vacuum degree of 1333 Pa, and further sealed at a vacuum degree of 1333 Pa. Inventive Battery 1 was produced. No boiling of the electrolyte was observed in the vacuum injection step and the vacuum sealing step. This battery is referred to as Battery 1 of the invention.

(Battery 2 of the Present Invention) A microporous membrane (thickness 27 μm) made of polypropylene treated with a surfactant (polyethylene glycol) was used as the separator 3, and 20 parts by weight of lithium tetrafluoroborate was used as an electrolyte. , A non-aqueous electrolyte obtained by mixing 40 parts by weight of ethylene carbonate, 40 parts by weight of γ-butyrolactone, 20 parts by weight of propylene carbonate and 5 parts by weight of n-methyl caprylate was used in the same manner as the battery 1 of the present invention. Inventive Battery 2 was produced. No boiling of the electrolytic solution was observed in the vacuum injection step and the vacuum sealing step. This battery is referred to as Battery 2 of the invention.

(Comparative Battery 1) Example 1 was repeated except that a non-aqueous electrolyte obtained by mixing 20 parts by weight of lithium tetrafluoroborate, 32 parts by weight of ethylene carbonate and 48 parts by weight of γ-butyrolactone was used as the electrolyte. A non-aqueous electrolyte battery 1 was produced in the same manner as described above. This battery is referred to as a comparative battery.

(Comparative Battery 2) As an electrolyte, 20 parts by weight of lithium tetrafluoroborate, 40 parts by weight of ethylene carbonate, 40 parts by weight of γ-butyrolactone, and 20 parts by weight of methyl acetate (boiling point: 57.5 ° C.) were mixed. A non-aqueous electrolyte battery was produced in the same manner as in Example 1, except that a non-aqueous electrolyte was used. In the vacuum injection step and the vacuum sealing step, boiling of the solvent in the electrolyte was observed.

(Test 1) Using these batteries 1 and 2 of the present invention and comparative battery 1, low-temperature characteristics at -20 ° C were investigated. The test conditions were: charging at 25 ° C, 0.2 hour rate,
4.1V 7 hours constant current constant voltage charge, discharge at 20 ° C
And a low-current discharge at −20 ° C. at a rate of 0.2 hour and a final voltage of 2.7 V. Table 1 shows the results of the obtained discharge capacities.

[0044]

[Table 1]

Table 1 shows that the battery of the present invention exhibits excellent low-temperature characteristics as compared with the comparative battery. It is considered that the reason for this is that the addition of propylene carbonate and a chain ester further lowers the freezing point and viscosity of the solvent, resulting in improved low-temperature characteristics, as compared with the comparative battery composed of ethylene carbonate and γ-butyrolactone. Further, since the boiling point of the added chain ester is 150 ° C. or higher, it does not boil at the time of vacuum injection at a vacuum degree of 1333 Pa and vacuum sealing, so that it is possible to shorten the time of the injection, impregnation, and sealing steps. .

(Test 2) Batteries 1 and 2 of the present invention and Comparative Battery 2
Was stored at 50 ° C. for one month in a discharge state. When the weights after storage were measured, it was confirmed that the batteries 1 and 2 of the present invention hardly changed in weight, whereas the weight of the comparative battery 2 was reduced by about 5%. In addition, the internal resistance after storage was almost unchanged in the case of the batteries 1 and 2 of the present invention, whereas that of the comparative battery 2 was about 1.5 times.

From the above results, the solvent in the electrolyte solution of the battery of the present invention was able to suppress the volatilization of the solvent from the resin sealing portion even when stored at a high temperature because the boiling point of the chain ester added was 150 ° C. or higher. It is considered something. Therefore, it is considered that the amount of the solvent did not change and the internal resistance after storage was not affected. That is, it was found that long-term reliability was excellent even when a chain ester having a boiling point of 150 ° C. or higher was added.

[0048]

As described above, the present invention can provide a lightweight non-aqueous electrolyte battery having high long-term reliability, high performance, and high energy density. Further, the time required for manufacturing processes such as liquid injection, impregnation, sealing, and the like can be shortened, manufacturing equipment can be simplified, and manufacturing costs can be reduced, so that its industrial value is extremely large.

[Brief description of the drawings]

FIG. 1 is a front view of a battery of the present invention.

FIG. 2 is a cross-sectional view of a terminal portion in a portion A of the battery of the present invention.

[Explanation of symbols]

 2 Positive electrode 3 Separator 4 Negative electrode 6 Metal resin composite

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeyoshi Nosaka 2-3-1, Furusobe-cho, Takatsuki-shi, Osaka Inside Yuasa Corporation (72) Inventor Toshiyuki Watanabe 2-chome, Furuso-cho, Takatsuki-shi, Osaka No. 21 Inside Yuasa Corporation (72) Inventor Hiroyuki Yoshida 2-3-21 Kosobe-cho, Takatsuki-shi, Osaka F-term (reference) 5H029 AJ05 AJ12 AJ14 AJ15 AK02 AK03 AK05 AK05 AK06 AK16 AL07 AL12 AL18 AM02 AM03 AM04 AM05 AM07 CJ28 DJ02 EJ12 HJ14 HJ15

Claims (3)

[Claims] 1. A battery using at least LiBF ₄ as an electrolyte salt, wherein the solvent is ethylene carbonate, γ-
A non-aqueous electrolyte battery comprising at least butyrolactone, propylene carbonate and a chain ester, wherein the chain ester has a boiling point of 150 ° C. or higher at normal pressure. 2. The non-aqueous electrolyte battery according to claim 1, wherein the exterior material is a metal-resin composite film. 3. The method for producing a non-aqueous electrolyte battery according to claim 1, comprising at least one or more decompression treatment steps, wherein the degree of vacuum in the decompression treatment step is in a range of 1333 Pa to 13332 Pa. .