JPH08306352A - Nonaqueous battery - Google Patents

Abstract

PURPOSE: To provide a non-aqueous high power battery with increased battery's capacity by using a separator with high heat resistance, ion permeability, thinness, and insulating property. CONSTITUTION: As a separator to be set between electrodes of a non-aqueous battery, a paper sheet is used, wherein the sheet is manufactured by using at least 10wt.% of a raw material prepared by unentangling reproduced cellulose fibers, which can be unentangled by beating, by beating within a range from 0-600ml CSF.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous battery using a non-aqueous electrolytic solution and a separator which is disposed between a positive electrode and a negative electrode and which allows ions to pass through while insulating, and particularly, a thin separator body. The present invention relates to a non-aqueous battery using a high-performance separator capable of achieving the above-mentioned properties and sufficiently exhibiting various characteristics required for this type of separator.

[0002]

2. Description of the Related Art Recently, small and cordless portable electronic devices such as portable telephones, portable notebook computers, and video movies have been remarkably spread. For such equipment, non-aqueous electrolyte batteries such as lithium batteries and lithium ion secondary batteries, which are small in size and have a high capacity, have been widely used.

In a non-aqueous battery, a woven fabric, a non-woven fabric, a glass woven fabric, or a synthetic material having fine pores is provided as a separator which is disposed between the positive electrode and the negative electrode of the battery and insulates the electrodes and allows ions to pass therethrough. A resin microporous membrane is used,
In particular, polyolefin microporous membranes such as polyethylene microporous membranes are often used because of their thinness, tensile strength and ion permeability. However, since the synthetic resin microporous membrane is inferior in heat resistance, the present inventor pays attention to paper excellent in heat resistance as a separator for a non-aqueous battery.

[0004]

However, although paper is excellent in heat resistance and tensile strength and is effective in a battery of an aqueous electrolyte solution, when a paper separator is used for a non-aqueous battery, it is inferior in ion permeability, and The separator is required to be thinner due to the demand for higher capacity of the non-aqueous battery. However, if the separator paper is thin, the insulating property between the positive electrode and the negative electrode may be poor and the electrodes may be short-circuited.

Therefore, in the present invention, by using a separator which is excellent in heat resistance and ion permeability, and which is thin and excellent in insulating property, it is possible to increase the battery capacity and realize a high performance non-aqueous battery. With the goal.

[0006]

In order to achieve the above-mentioned object, the non-aqueous battery of the present invention comprises a beating raw material of beatingable regenerated cellulose fiber in a separator interposed between electrodes.
It is characterized by using a paper which has been made into paper by using at least wt%.

The beating raw material of regenerated cellulose fiber is
A value C indicating the degree of beating specified in JIS P 8121
Beat in the range of SF 600 to 0 ml.

The paper has a thickness of 20 to 60 μm and a density of 0.25 to 0.70 g / cm ³ .

Further, the positive electrode active material is TiS ₂ , MoS ₂ , N
Metal chalcogen compounds such as bSe, V ₂ O ₅ , MnO ₂ ,
Metal oxides such as Nb ₂ O ₅ , LiCoO ₂ , LiNiO ₂ ,
Any one of lithium-containing composite metal oxides such as Li _x Mn ₂ O ₄ , high molecular weight polymers such as polyaniline and polypyrrole, fluorocarbons, and the negative electrode active material is Li metal and LiA
Lithium alloy such as l, carbonaceous material, polyacene, poly-
Conductive polymer material such as P-phenylene, Li _x Fe
₂ O ₂ , any one of metal oxides such as Li _x WO ₂ , the electrolyte of the electrolytic solution is LiClO ₄ , LiPF ₆ , LiAsF ₆ ,
LiBF ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, (CF ₃
SO ₂ ) ₂ NLi or any one of a mixture of two or more lithium salts, and the solvent of the electrolytic solution is propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane. , 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-
Any one kind or a mixture of two or more kinds of methyltetrahydrofuran, 1,3-dioxolane, sulfolane, methylsulfolane, acetonitrile, propionitrile, methyl formate, ethyl formate, methyl acetate, ethyl acetate and the like is used.

Further, LiCoO ₂ and LiN are used as the positive electrode active material.
A carbonaceous material is used for the lithium-containing composite oxide such as iO ₂ and Li _x Mn ₂ O ₄ , and the negative electrode active material.

[0011]

[Operation] Regenerated cellulose fiber that can be beaten has a highly specific gravity and highly developed fibril network structure.
Uniform fibrillation is possible by performing a beating process with a beating machine. In addition, the regenerated cellulose fiber that can be beaten produces fibrils when it is beaten to increase its flexibility, so that a separator having a high density and excellent tensile strength can be manufactured. The obtained fibrillated fine fibers do not form a film like the case where the fibrillated fine fibers of natural fibers are made into paper, and the fine fibers independent of each other are constituted by innumerable point bonds, so that they are extremely dense. And the cross section of the fibril is almost perfect circle,
Excellent ion permeability.

[0012]

EXAMPLE The present invention is used as a raw material for a separator of a non-aqueous battery, such as a regenerated cellulose fiber having a high degree of polymerization by low acid bath spinning (commonly called polynosic rayon) and a solvent-spun rayon such as an amine / oxide type solvent. This paper focuses on regenerated cellulose fibers that can be beaten (fibrillated) with a beating machine installed in the papermaking process. Paper made using 10% by weight or more of the beating raw material of this beatable regenerated cellulose fiber is used. To create a separator.

Regenerated cellulose fibers are manufactured according to JIS P 81
Value indicating the degree of beating specified in 21 CSF 600 to 0 m
It is preferred to beat within the range of 1. Polynosic rayon and solvent-spun rayon used in the present invention,
In both cases, the unrefined CSF is about 800 ml, and fibrils gradually occur due to beating, but when the degree of beating is shallow, the number of adhesion points due to fibrils is small and the strength becomes weak. Therefore, in order to obtain the necessary fibrils, it is appropriate to beat the CSF to 600 ml or less. Even when both polynosic rayon and solvent-spun rayon are beaten until the CSF value becomes 0 ml, there is no formation of a film due to twisting of the fibers and formation of a film during drying, thus improving the compactness and enhancing the strength. be able to.

The other pulp to be blended with the beaten regenerated cellulose fiber is not particularly limited, and may be any of Manila hemp, sisal pulp, softwood kraft pulp and the like. The degree of beating may be appropriately beaten according to the degree of beating of the regenerated cellulose fiber. The mixing ratio of these is determined by the amount of the beating raw material of the regenerated cellulose fiber.

First, as a raw material for a separator in the non-aqueous battery of the present invention, beaten regenerated cellulose fibers cut into 2 to 5 mm are beaten by a predetermined beater until an appropriate CSF value is obtained. On the other hand, natural fibers as a mixed raw material are similarly beaten appropriately, and then these beaten raw materials are appropriately mixed to produce a separator having a predetermined thickness.
The separator thus obtained is interposed between the positive electrode and the negative electrode, laminated by winding, and impregnated with the electrolytic solution to manufacture the non-aqueous battery of the present invention.

The resulting separator has a thickness of 20-100.
[mu] m, density is 0.25 to 0.90 g / cm < ³ >, and it is effective in the range of commonly used separators, but especially 20 to 60 [mu] m in thickness and density is 0.25 to 0.70 g /
Preferable results can be obtained in the range of cm ³ .

Regenerated cellulose fibers capable of beating such as polynosic rayon and solvent-spun rayon can be beaten to a fibril having a uniform crystal unit by a beating treatment. By mixing this beating raw material with natural fibers, natural fibers are mixed. It fills voids moderately, has a uniform formation and has extremely high density, and since it is formed into a microporous sheet, it has excellent ion permeability,
Moreover, a separator having excellent tensile strength can be obtained.

Examples of the positive electrode active material of the non-aqueous battery of the present invention include metal chalcogen compounds such as TiS ₂ , MoS ₂ and NbSe, metal oxides such as V ₂ O ₅ , MnO ₂ and Nb ₂ O ₅ , and L.
Any one of lithium-containing composite metal oxides such as iCoO ₂ , LiNiO ₂ and Li _x Mn ₂ O ₄ , polymer polymers such as polyaniline and polypyrrole, and carbon fluoride is used. In particular, it is a positive electrode active material capable of dedoping and doping lithium ions, and has a general formula of Li _x M _y N _z O ₂ (M represents at least one kind of transition metal, and N represents at least one kind of non-transition metal). M is not particularly limited, but Co, N
i, Fe, Mn, V, Mo, and the like, and N is not particularly limited, but Al, In, Sn, and the like are preferable. As a specific example, when represented by a chemical formula in a discharged state containing Li ions, a lithium cobalt oxide such as Li _x Co _y N _z O ₂ (N
Is at least one metal selected from Al, In and Sn, 0 <x ≦ 1.1, 0.5 <y ≦ 1, z ≦ 0.
1), Li _x CoO ₂ (0 <x ≦ 1), Li _x Co _y Ni _z
O ₂ (0 <x ≦ 1, y + z = 1) Lithium nickel oxide, for example Li _x NiO ₂ (0 <x
≦ 1) Lithium manganese oxide, for example, Li _x MnO ₂ , Li _x
Mn ₂ O ₄ (0 <x ≦ 1), LiCo _x Mn _2-x O ₄ (0 <
x ≦ 0.5) Lithium chromium oxide, for example Li _x Cr ₃ O ₈ (0 <x
≦ 1), LiCrO ₂ lithium vanadium oxide, for example Li _x V ₂ O ₅ (0 <
x ≦ 1), Li _x V ₆ O ₁₃ , Li _{1 + x} V ₃ O ₈ lithium molybdenum oxide, for example Li _x MoO ₂ lithium molybdenum disulfide, for example Li _x MoS ₂ lithium titanium oxide, for example Li _x Ti. ₂ O ₄ lithium titanium sulfide such as Li _x Ti ₂ S ₂ lithium iron oxide such as Li _x FeO ₂ (0 <x ≦
1), Li _x Fe _y N _z O _z (N is Co, Ni, Ti, Mn
At least one metal selected from the group, 0 <x ≦ 1,
0.8 ≦ y ≦ 0.99, 0.01 ≦ z ≦ 0.2) and the like. And, particularly preferably, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, and lithium iron oxide.

Examples of the negative electrode active material of the non-aqueous battery of the present invention include lithium metal and lithium alloys such as LiAl, carbonaceous materials, conductive polymer materials such as polyacene and poly-P-phenylene, and Li _x Fe ₂ O ₂ , Li _x WO ₂ or the like is used. In particular, a negative electrode active material that can be doped with lithium ions and dedoped, graphite, pyrolytic carbon, pitch coke, needle coke,
Petroleum coke, fired body of organic polymer (phenolic resin,
A carbonaceous material such as a furan resin or a fired body such as polyacrylonitrile) is preferable.

The electrolyte of the electrolytic solution used in the non-aqueous battery of the present invention includes LiClO ₄ , LiAsF ₆ and LiPF ₄ .
₆ , LiBF ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, CF
Any one of lithium salts such as ₃ SO ₃ Li and (CF ₃ SO ₂ ) ₂ NLi or a mixture of two or more thereof is used.

As the solvent of the electrolytic solution used in the non-aqueous battery of the present invention, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, sulfolane, methylsulfolane, acetonitrile, propionitrile, methyl formate, ethyl formate, methyl acetate, ethyl acetate, etc. Use a mixture.

The non-aqueous battery of the present invention will be described in more detail below with reference to examples. (1) Method for producing positive electrode Li, C having a composition of Li _1.03 Co _0.92 Sn _0.02 O ₂
o 100 parts by weight of complex oxide, 2.5 parts by weight of graphite and 2.5 parts by weight of acetylene black were mixed, and then 2 parts by weight of fluororubber was mixed with 60 parts by weight of a mixed solvent of ethyl acetate / ethyl cellosolve 1: 1 (weight ratio). The liquids dissolved in the parts were mixed to obtain a slurry coating liquid. Then, this coating solution was applied to both sides of an Al foil having a width of 600 mm and a thickness of 15 μm at a coating amount of 270 g / m ² (when dried) per side using a coating machine having a doctor blade coater head.
The coating thickness is 215 μm. This coated product is pressed with a calendar roll and slit into a 39 mm width using a slitter to obtain a positive electrode for a non-aqueous battery.

(2) Method for preparing negative electrode 100 parts by weight of crushed needle coke and 5 parts by weight of fluororubber were dissolved in 90 parts by weight of a 1: 1 (weight ratio) mixed solvent of ethyl acetate / ethyl cellosolve and mixed. Then, a slurry-like coating liquid was obtained. And this coating liquid is 600m wide
138 g / m ² using a coating machine having a doctor blade coater head on one surface of a Cu foil having a thickness of 10 μm and a thickness of 10 μm.
It is applied with the coating amount (when dry) and the coating thickness is 300 μm.
And After pressing this coated product with a calendar roll,
A slitter is used to slit a width of 40 mm to form a negative electrode for a non-aqueous battery.

(3) Method for producing non-aqueous battery The positive electrode and the negative electrode are stacked on both sides of the separator and wound into a coil having an outer diameter of 14.9 mm using a winding machine. This wound coil was put in a battery can having an outer diameter of 16 mm, and 1: 1: 2 (weight ratio) of propylene carbonate / ethylene carbonate / γ-butyrolactone (weight ratio) was mixed with 1 LiBF _{4 in} a mixed solvent.
After being impregnated with a solution of M concentration as an electrolytic solution and then sealed, a nonaqueous battery having a height of 50 mm was prepared.

(4) Evaluation method of separator The thickness, density and tensile strength were measured by the method specified in JIS C2301. ESR (equivalent series resistance) is 20
It was measured by an LCR meter at a frequency of 1 kHz at ° C.

(5) Evaluation Method for Non-Aqueous Battery The battery capacity was measured when discharged at 0.5 A at 20 ° C. The short-circuit rate represents the ratio of insulation defects of the separator at the initial stage of assembling the non-aqueous battery by the number of insulation defects / total number of measurements. As an item for evaluating heat resistance, the ratio of insulation failure of the separator after leaving the non-aqueous battery in an oven at 200 ° C. for 10 minutes was expressed by the number of insulation failures / total number of measurements.

(Example 1) Polynosic rayon CS
70% of the raw material beaten to 500 ml of F and 30% of the raw material of Manila hemp pulp beaten to 600 ml of CSF are mixed to make paper with a thickness of 50.0 μm and a density of 0.320 g / cm ³ , which is used as a separator. The battery using this separator was measured for tensile strength, ESR, battery capacity, short circuit failure rate, and heat resistance, and the short circuit failure rate after 200 minutes at 200 ° C. was measured. The results are shown in Table 1.

Example 2 Solvent-spun rayon was made into CSF1.
Mix 80% raw material beaten to 00 ml with 20% raw material beaten Manila hemp pulp to CSF 580 ml,
A paper having a thickness of 50.1 μm and a density of 0.315 g / cm ^{3 is made into} a paper and used as a separator. A battery using this separator was similarly measured, and the results are shown in Table 1.

Example 3 Solvent-spun rayon was used as CSF3.
Paper having a thickness of 50.4 μm and a density of 0.318 g / cm ³ is made into paper with the raw material beaten to 0 ml, and this is used as a separator. Measured for batteries using this separator,
Table 1 shows the results.

Example 4 Solvent-spun rayon was CSF0
Paper having a thickness of 25.4 μm and a density of 0.583 g / cm ^{3 is made into} a paper using the raw material beaten to the volume of ml, and this is used as a separator. Measured for batteries using this separator,
Table 1 shows the results.

Comparative Example 1 Thickness 50.1 μm and density 0.
Measurement was carried out on a battery using a polyethylene microporous membrane of 315 g / cm ³ as a separator, and the results are shown in Table 1.

Comparative Example 2 Manila hemp pulp was mixed with CSF70.
Paper having a thickness of 50.2 μm and a density of 0.305 g / cm ³ is made from the raw material beaten to 0 ml, and this is used as a separator. Measured for batteries using this separator,
Table 1 shows the results.

Comparative Example 3 30% of unbeaten viscose rayon and 70% of raw material of Manila hemp pulp beaten to 370 ml of CSF were mixed to produce paper having a thickness of 50.3 μm and a density of 0.310 g / cm ^3. And use this as a separator. Measured for batteries using this separator,
Table 1 shows the results.

Comparative Example 4 Thickness 25.0 μm, Density 0.
Measurements were carried out on a battery using a 585 g / cm ³ polypropylene microporous membrane as a separator, and the results are shown in Table 1.

(Comparative Example 5) Manila hemp pulp was treated with CSF30.
From the raw material beaten to 0 ml, paper having a thickness of 25.2 μm and a density of 0.595 g / cm ³ is made into paper and used as a separator. Measured for batteries using this separator,
Table 1 shows the results.

COMPARATIVE EXAMPLE 6 Softwood kraft pulp was CS
Paper having a thickness of 15.7 μm and a density of 0.835 g / cm ³ is made from the raw material beaten to F0 ml, and this is used as a separator. A battery using this separator was measured and the results are shown in Table 1.

(Comparative Example 7) Manila hemp pulp was CSF 0m
From the raw material beaten to 1 l, the thickness was 20.3 μm and the density was 0.
Paper of 739 g / cm ^{3 is made into} a paper, and this is used as a separator. A battery using this separator was measured and the results are shown in Table 1.

[0038]

[Table 1]

As shown in the measurement results of Table 1, the separators according to the present invention using the paper made by blending the beating raw material of the regenerated cellulose fiber capable of beating are Comparative Examples 1, 2, 4,
Compared with the conventional polyethylene microporous membrane, paper made of Manila hemp pulp, polypropylene microporous membrane, etc. as shown in 5, the ESR, short-circuit rate and heat resistance are improved, and moreover, it has sufficient tensile strength and battery characteristics. It is clear that Also, when beating softwood kraft pulp or Manila hemp pulp as in Comparative Examples 6 to 7, E
SR becomes too large to charge and discharge. Furthermore, when the unbeaten regenerated cellulose fiber as in Comparative Example 4 is blended, the short-circuit rate is inferior.

[0040]

As described in detail above, according to the present invention, since the regenerated cellulose fiber capable of beating has a highly-developed fibril network structure with a high specific gravity, it can be subjected to a beating treatment with a beating machine. Uniform fibrillation is possible. In addition, the regenerated cellulose fiber that can be beaten produces fibrils when it is beaten to increase its flexibility, so that a separator having a high density and excellent tensile strength can be manufactured. The obtained fibrillated fine fibers do not form a film like the case where the fibrillated fine fibers of natural fibers are made into paper, and the fine fibers independent of each other are constituted by innumerable point bonds, so that they are extremely dense. Further, since the cross section of the fibril is almost a perfect circle, it has excellent ion permeability. As a result, according to the present invention, it is possible to increase the battery capacity and realize a high-performance non-aqueous battery by using a separator that is excellent in heat resistance and ion permeability and is thin and excellent in insulation. Becomes

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location H01M 4/06 H01M 6/16 A 6/16 10/40 Z 10/40 D21H 5/14 A ( 72) Inventor Masataka Yamashita 72 Horikawa-cho, Saiwai-ku, Kawasaki City, Kanagawa Prefecture

Claims (5)

[Claims] 1. A non-aqueous battery characterized in that a paper made by using a beating material of beatingable regenerated cellulose fiber in an amount of 10% by weight or more is used as a separator interposed between electrodes. 2. A beating raw material of regenerated cellulose fiber is JI.
A value CSF that indicates the degree of beating specified in SP 8121
The non-aqueous battery according to claim 1, which is beaten in a range of 600 to 0 ml. 3. The paper has a thickness of 20 to 60 μm and a density of 0.
The non-aqueous battery according to claim 1, which has a weight of 25 to 0.70 g / cm ³ . 4. The positive electrode active material is TiS ₂ , MoS ₂ , NbS.
Metal chalcogen compounds such as e, V ₂ O ₅ , MnO ₂ , Nb ₂
Metal oxides such as O ₅ , LiCoO ₂ , LiNiO ₂ , Li _x
Any one of lithium-containing composite metal oxides such as Mn ₂ O ₄ , high molecular weight polymers such as polyaniline and polypyrrole, carbon fluoride, and negative electrode active materials such as Li metal and lithium alloys such as LiAl, carbonaceous materials, polyacene , Conductive polymer materials such as poly-P-phenylene, Li _x Fe ₂ O ₂ , Li _x
Any one of metal oxides such as WO ₂ and the electrolyte of the electrolytic solution is LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiBF ₄ ,
CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ N
Any one or a mixture of two or more lithium salts such as Li, the solvent of the electrolytic solution is propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, 1,2. -Diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, sulfolane, methylsulfolane, acetonitrile, propionitrile, methyl formate, ethyl formate, methyl acetate, ethyl acetate, etc. The non-aqueous battery according to claim 1, which is a mixture of two or more kinds. 5. The positive electrode active material comprises LiCoO ₂ and LiNi.
A lithium-containing composite oxide such as O ₂ or Li _x Mn ₂ O ₄ and a carbonaceous material are used for the negative electrode active material.
The non-aqueous battery described.