JP3071897B2 - Battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel secondary battery having excellent cyclability, output characteristics, storage characteristics and safety.

[0002]

2. Description of the Related Art In recent years, various non-aqueous secondary batteries have been proposed as small and lightweight secondary batteries which can replace conventional acid-lead batteries and nickel / cadmium batteries. As a positive electrode active material used for a positive electrode used in such a non-aqueous secondary battery, for example, a chalcogenite-based compound having a layered structure has been drawing attention as an example utilizing intercalation of a layered compound. For example, although Li _n TiS _2, Li _n MoS chalcogenide compounds such as ₂ has a relatively excellent cycle property, the electromotive force is low, even when a Li metal as a negative electrode, a practical discharge voltage It was at most around 2 V, which was not satisfactory in terms of high electromotive force, which is one of the characteristics of non-aqueous batteries.

On the other hand, Li _n V ₂ similarly having a layered structure
S _5, Li _n V ₂ O metal oxide-based compounds such as ₁₃ are focused at a point having a characteristic of high electromotive force. However, these metal oxide compounds are poor in performance in terms of cycleability, utilization rate, that is, overvoltage during charge / discharge, that is, when actually usable for charge / discharge, and have not yet been put to practical use. .

[0004]

SUMMARY OF THE INVENTION Among them, Japanese Patent Application Laid-Open
Which are disclosed in JP-A-136131, JP-A-62-90863 and JP-A-3-49155.
CoO ₂ , Li _x Co _y N _z O ₂ (where N is Al, I
represents at least one selected from the group consisting of n and Sn. ),
A composite metal oxide containing Li and Co as the main components, such as Li _x Ni _y Co _(1-y) O ₂ , has an electromotive force of 4 V or more, and has a theoretical energy density (per positive electrode active material) of 1 , 1
Since it has a surprising value of 00 WHr / kg or more, it is a cathode active material that has received particular attention in recent years.

[0005] However, although the composite metal oxide has excellent characteristics as described above, there are points to be improved in storage characteristics, output characteristics, and the like in order to be used as a battery that can be put into practical use.

[0006]

Means for Solving the Problems The present inventors have proposed such L
i, a result of intensive studies for the battery characteristics of the composite metal oxide composed mainly of Co, and carbon as a negative electrode active material, a positive
Make the particle size of the composite metal oxide that constitutes the poles a specific range .
As a result , the inventors have found that excellent properties such as storage characteristics and output characteristics are exhibited, and have completed the present invention.

A secondary battery according to the present invention is a secondary battery using a composite metal oxide containing Li and Co as main components as a positive electrode active material and carbon as a negative electrode active material .
Particle size distribution of the composite metal oxide containing Li and Co as main components
D (25%) = 0.5-3.0 μ , D (50%) = 2
-10 μm , D (75%) = 3.5-30 μ .

Hereinafter, the composite metal oxide containing Li and Co as main components in the present invention is a compound having a layered structure and capable of electrochemically intercalating and deintercalating Li ions. And at least 50% by weight of Co in the metal component.

Although not particularly limited, examples of such a composite metal oxide include, for example, LiCoO ₂ disclosed in JP-A-55-136131 and JP-A-62-90.
General formula Li _x Co _y N _z disclosed in JP 863
O ₂ (where N represents at least one selected from the group consisting of Al, In, and Sn, and x, y, and z each are 0.05 ≧ x ≧
1.10, 0.85 ≧ y ≧ 1.00, 0.001 ≧ z ≧
Represents the number 0.10. ) And Li _x Ni _(1-y) O ₃ disclosed in JP-A-3-49155 (where 0
≦ x ≦ 1, 0 ≦ y ≦ 0.10).

In order to obtain such a composite metal oxide, an Li compound such as lithium hydroxide, lithium oxide, lithium carbonate and lithium nitrate and a cobalt compound such as cobalt oxide, cobalt hydroxide, cobalt carbonate and cobalt nitrate are further required. Then, it can be easily obtained by a firing reaction with another metal compound.

Each of these composite metal oxides has, as a positive electrode active material, high voltage and high capacity, which are excellent characteristics not found in other active materials. In particular, the general formula Li
_x Co _y N _z O ₂ (where N represents at least one selected from the group consisting of Al, In, and Sn, and x, y, and z are respectively 0.05 ≧ x ≧ 1.10 and 0.85 ≧ y ≧ 1.00,
It represents the number of 0.001 ≧ z ≧ 0.10. ) Is a composite metal oxide that is particularly excellent in properties such as cycleability and is preferably used in the present invention.

In the present invention, the average particle size of the composite metal oxide containing Li and Co as main components , that is, D (5)
0%) should be in the range of 2-10μ. When the average particle diameter D (50%) is less than 2 μm, the current efficiency and the high-temperature storage characteristics are deteriorated, which is not preferable.
If it exceeds 10 μm, the output characteristics deteriorate, which is not preferable.

Further , D (25%) of the particle size distribution is 0.5 to
A range of 3.0μ is preferred. The D (25%) is 0.5 μ
If it is less than 1, the decrease in current efficiency is not preferable.
If it exceeds 3.0 μm, the output characteristics and further the storage characteristics deteriorate, which is not preferable.

Further, D (75%) of the particle size distribution is 3.5 to
A range of 30μ is preferred. When the D (75%) is less than 3.5μ, the current efficiency is deteriorated, and when it exceeds 30μ, the output characteristics are deteriorated, which is not preferable.

There are various methods for obtaining a composite metal oxide containing Li and Co as main components having a particle size and a particle size distribution within the scope of the present invention. For example, the composite metal oxide obtained by the firing reaction as described above is subjected to a classifier,
The simplest method is to make the particle size distribution within the range specified by the present invention.

As another method, the average particle diameter D (50%) of the cobalt compound used in the calcination reaction is 0.5 to 1.5.
By using μ of cobalt oxide, a composite metal oxide having a particle size distribution directly within the range specified in the present invention can be obtained. When cobalt oxide having a particle size of less than 0.5 μm is used, it is difficult to make D (50%) of the obtained composite metal oxide 2 μm or more. When cobalt oxide exceeding 1.5μ is used, D (25%) of the composite metal oxide
Exceeds 3μ, which is not preferable.

The negative electrode active material used in the battery of the present invention is
And a carbon negative electrode is a preferable negative electrode material without causing a phenomenon such as dendrite.

Basic components for assembling the secondary battery of the present invention, particularly a non-aqueous secondary battery, include an electrode using the active material, a separator, and a non-aqueous electrolyte. The separator is not particularly limited, and examples thereof include woven fabric, nonwoven fabric, glass woven fabric, and synthetic resin microporous membrane. When a thin film and a large-area electrode are used, the separator is disclosed in, for example, JP-A-58-59072. The synthetic resin microporous membrane to be used is particularly preferably a polyolefin-based microporous membrane in terms of thickness, strength and membrane resistance.

The electrolyte of the non-aqueous electrolyte is not particularly limited. For example, LiClO ₄ , LiBF ₄ , L
iAsF ₆ , CF ₃ SO ₂ Li, LiPF ₆ , LiI,
LiAlCl ₄ , NaClO ₄ , NaBF ₄ , NaI,
(N-Bu) ₄ NCLO ₄ , (n-Bu) ₄ NF ₄ , K
PF _6, and the like.

Examples of the organic solvent for the electrolyte used include, for example, ethers, ketones, lactones, nitriles, amines, amides, sulfur compounds, chlorinated hydrocarbons, esters, carbonates, nitro acids and the like. Compounds, phosphate ester compounds, sulfolane compounds and the like can be used, among which ethers, ketones, nitriles, chlorinated hydrocarbons, carbonates,
Sulfolane compounds are preferred. More preferred are cyclic carbonates.

Representative examples of these are tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, anisole, monoglyme, acetonitrile, propionitrile, 4-methyl-2-pentanone, butyronitrile, valeronitrile, benzonitrile, , 2-
Dichloroethane, γ-butyrolactone, dimethoxyethane, methylformate, propylene carbonate, ethylene carbonate, vinylene carbonate, dimethylformamide, dimethylsulfoxide, dimethylthioformamide, sulfolane, 3-methyl-sulfolane, trimethyl phosphate, triethyl phosphate and these ethyl salts Examples thereof include a mixed solvent, but are not necessarily limited thereto.

If necessary, a battery is formed by using components such as a current collector, a terminal, and an insulating plate. Further, the structure of the battery is not particularly limited, but a positive electrode, a negative electrode, and, if necessary, a paper type battery, a stacked type battery, or a positive electrode, a negative electrode, further having a single-layer or multiple-layer separator. For example, a form of a cylindrical battery or the like in which a separator is wound in a roll shape is given as an example.

[0023]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples, which do not limit the scope of the present invention. Particle size distribution measurement: Dry flow dispersion unit RODOS and laser diffraction type particle size distribution measurement optical system HEROS-BASIS / KA (0.5 to
175 μ range), and the measurement was carried out by dry dispersion under the conditions of an air flow pressure of 5.0 bar, a blowing pressure of 100 mbar, and cascade use.

[0024]

EXAMPLES 1-5 AND COMPARATIVE EXAMPLES 1-4 Cobalt oxide, stannic oxide and lithium carbonate of various particle sizes shown in Tables 1-2 were mixed and fired under the firing temperature conditions shown in Table 1. As a result, Li, Co, and Sn composite metal oxides were obtained. Li _1.03
After mixing 100 parts by weight of a Li / Co composite metal oxide having a composition of Co _0.92 Sn _0.02 O ₂ , 2.5 parts by weight of graphite, and 2.5 parts by weight of acetylene black, 2 parts by weight of fluororubber is mixed with ethyl acetate / ethyl. Cellsolve 1: 1
(Weight ratio) The solutions dissolved in 60 parts by weight of the mixed solvent were mixed to obtain a slurry-like coating solution.

Using a coating machine having a doctor blade coater head, the above coating liquid was applied to both surfaces of an Al foil having a width of 600 mm and a thickness of 15 μm. Coating thickness 29 after double-sided coating
It was 0μ. A solution prepared by dissolving 100 parts by weight of the needle coke pulverized product and 5 parts by weight of fluororubber in 90 parts by weight of a 1: 1 (weight ratio) mixed solvent of ethyl acetate / ethyl cellosolve was mixed to obtain a slurry-like coating liquid. .

Using a coating machine having a doctor blade coater head, the above coating liquid was applied to both surfaces of a Cu foil having a width of 600 mm and a thickness of 10 μm. The coating thickness of the double-sided coating solution is 35
It was 0μ.

After pressing the two types of coated products with a calender roll, both of them were slit to a width of 41 mm using a slitter. A Li _1.03 Co _0.92 Sn _0.02 O ₂ coated product is used as a positive electrode, a needle coke coated product is used as a negative electrode, and a polyethylene microporous membrane (Hypore 4030) is used as a separator.
U Asahi Kasei Kogyo Co., Ltd.)
It was wound into a 4.9 mm coil. This wound coil was placed in a battery can having an outer diameter of 16 mm, and then a solution of LiBF ₄ dissolved at a concentration of 1 M in a mixed solvent of propylene carbonate / γ-butyrolactone in a ratio of 1: 2 (weight ratio) was impregnated as an electrolyte. After that, it is sealed, and 50 mm high A shown in FIG.
We prototyped a battery can of the size. This battery was charged at a constant voltage of 4.2 V, and the battery performance was evaluated. Tables 1 and 2 show the results.
Shown in

[0028]

[Table 1]

[0029]

[Table 2] *) Output characteristics: 2A discharge amount / 1A discharge amount

[0030]

According to the battery of the present invention, carbon is used as a negative electrode active material.
And the particle size of the composite metal oxide forming the positive electrode
In particular, battery efficiency and other cycle characteristics,
It has excellent self-discharge characteristics and is therefore compact and lightweight,
It is extremely useful as a power source for small electronic devices, electric vehicles, power storage, and the like.

[Brief description of the drawings]

FIG. 1 is a partially cutaway view of a battery according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 positive electrode 2 separator 3 negative electrode 4 insulating plate 5 negative electrode lead made of copper 6 positive electrode lead made of aluminum 7 gasket

Claims (1)

(57) [Claims] 1. A secondary battery in which a composite metal oxide containing Li and Co as main components is used as a positive electrode active material and carbon is used as a negative electrode active material , wherein the composite metal oxide containing Li and Co as main components is used. When the particle size distribution is D (25%) = 0.5 to 3.0 μm , D
(50%) = 2-10 μ , D (75%) = 3.5-30
A secondary battery having a range of μ .