JPH0594822A - Battery - Google Patents

Abstract

PURPOSE:To increase the cycle property, the output property, the preservative property, and the safety. CONSTITUTION:In a secondary battery including a complex metal oxide mainly of Li and Co as the positive electrode active material, the mean particle diameter D (50 %) of the compound metallic oxide is made in the scope 2 to 10mu. And the scopes of the grading distribution are: D (25%)=0.5 to 3.0mu, D (50%)=2 to 10mu, and D (75%)=3.5 to 30mu. And a cobalt oxide of the scope of mean grading D (50%)=0.5 to 1.5mu is used as the material. As a result, the resultant battery is compact and light weight, and the battery efficiency, the cycle property, and the self-discharge property are excellent in particular. Consequently, it is useful extremely for a power source of a compact electronic apparatus, an electric automobile, and for power storage.

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 cycleability, output characteristic, storage characteristic 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 replacing conventional acid-lead batteries and nickel / cadmonium batteries. As a positive electrode active material used for a positive electrode used in such a non-aqueous secondary battery, for example, a chalcogenite compound having a layered structure has attracted attention as an example using 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 The voltage was about 2 V at most, which was not satisfactory in terms of high electromotive force, which is one of the features of non-aqueous batteries.

On the other hand, Li _n V ₂ which also has 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 inferior in performance in terms of cycleability, utilization rate, that is, when they can be actually used for charging / discharging, and further, overvoltage during charging / discharging. ..

[0004]

SUMMARY OF THE INVENTION
-136131, JP-A-62-90863, JP-A-3-49155
CoO ₂ , Li _x Co _y N _z O ₂ (where N is Al, I
It represents at least one selected from the group consisting of n and Sn. ),
Li _x Ni _y Co _(1-y) O ₂ and other composite metal oxides containing Li and Co as the main components have an electromotive force of 4 V or more and a theoretical energy density (per positive electrode active material) of 1 , 1
Since it has an astonishing value of not less than 00 WHr / kg, it is a positive electrode active material that has been particularly attracting attention in recent years.

However, although the composite metal oxide has excellent characteristics as described above, there are some points to be improved such as storage characteristics and output characteristics in order to use it as a battery which can be practically used.

[0006]

SUMMARY OF THE INVENTION The present inventors
As a result of diligent study on the battery characteristics of the composite metal oxide containing i and Co as the main components, it was found that excellent storage characteristics, output characteristics and the like are exhibited in a specific particle size range,
The present invention has been completed.

That is, the secondary battery of the present invention is made of Li, C
In a secondary battery using a composite metal oxide containing o as a main component as a positive electrode active material, the average particle diameter D (50%) of the composite metal oxide containing Li and Co as the main components is in the range of 2 to 10 μm. It is characterized by being.

Hereinafter, the composite metal oxide containing Li and Co as the main components in the present invention is a compound having a layered structure and capable of electrochemically intercalating or deintercalating Li ions. At least Co is contained in an amount of 50% by weight or more 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.
The general formula Li _x Co _y N _z disclosed in Japanese Patent No. 863 publication.
O ₂ (wherein N represents at least one selected from the group consisting of Al, In and Sn, and x, y and z are each 0.05 ≧ x ≧
1.10, 0.85 ≧ y ≧ 1.00, 0.001 ≧ z ≧
Represents a number of 0.10. ), And Li _x Ni _(1-y) O ₃ disclosed in Japanese Patent Laid-Open No. 3-49155 (however, 0
≦ x ≦ 1, 0 ≦ y ≦ 0.10) and the like.

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

In the present invention, the average particle diameter D (50%) of the composite metal oxide containing Li and Co as main components is 2 to 10.
Must be in the μ range. The average particle diameter D (50%)
Is less than 2 μ, it is not preferable because it causes deterioration of current efficiency and deterioration of high temperature storage characteristics. On the other hand, when it exceeds 10 μ, the output characteristics deteriorate, which is not preferable.

The cumulative distribution 25 is not particularly limited.
The% particle diameter D (25%) is preferably in the range of 0.5 to 3.0 μ. When the D (25%) is less than 0.5 μ, the current efficiency is significantly decreased, which is not preferable. On the other hand, when it exceeds 3.0 μ, output characteristics and storage characteristics are deteriorated, which is not preferable.

Similarly, although not particularly limited, the cumulative distribution 75% D (75%) is preferably in the range of 3.5 to 30 μ. When the D (75%) is less than 3.5 μ, the current efficiency is deteriorated, and when it exceeds 30 μ, the output characteristics are deteriorated, which is not preferable.

There are various methods for obtaining a composite metal oxide containing Li and Co as the main components and having a particle size and 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 in the present invention.

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

The electrode active material used in the battery of the present invention is not particularly limited, but Li metal, Li-Al alloy, carbon negative electrode and the like can be exemplified. Particularly, the carbon negative electrode does not cause a phenomenon such as dendrite and is a preferable combination. Is.

As a basic constituent element for assembling the secondary battery of the present invention, particularly a non-aqueous secondary battery, an electrode using the above active material, a separator, and a non-aqueous electrolytic solution can be mentioned. The separator is not particularly limited, and examples thereof include woven cloth, non-woven cloth, glass woven cloth, and synthetic resin microporous film. When a thin film or a large-area electrode is used, it is disclosed in, for example, JP-A-58-59072. The synthetic resin microporous membrane to be used, particularly the polyolefin microporous membrane is preferable in terms of thickness, strength and membrane resistance.

The electrolyte of the non-aqueous electrolytic solution is not particularly limited, but as an 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
Examples include PF _{6 and the} like.

Examples of the organic solvent of the electrolytic solution used include ethers, ketones, lactones, nitriles, amines, amides, sulfur compounds, chlorinated hydrocarbons, esters, carbonates, nitro. A compound, a phosphate compound, a sulfolane compound, or the like can be used, and among these, ethers, ketones, nitriles, chlorinated hydrocarbons, carbonates,
Sulfolane compounds are preferred. More preferred are cyclic carbonates.

Typical examples of these are tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, anisole, monoglyme, acetonitrile, propionitrile, 4-methyl-2-pentanone, butyronitrile, valeronitrile, benzonitrile, 1 , 2-
Dichloroethane, γ-butyrolactone, dimethoxyethane, methyl formate, propylene carbonate, ethylene carbonate, vinylene carbonate, dimethylformamide, dimethyl sulfoxide, dimethylthioformamide, sulfolane, 3-methyl-sulfolane, trimethyl phosphate, triethyl phosphate, and triethyl phosphate thereof. Examples of the mixed solvent include, but are not necessarily limited to, these.

Further, if necessary, a battery is constructed 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 further, if necessary, a paper-type battery having a single layer or multiple layers of a separator, a laminated battery, or a positive electrode, a negative electrode, and further required. For example, a form of a cylindrical battery in which a separator is wound in a roll shape or the like can be given.

[0023]

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

[0024]

Examples 1 to 5 and Comparative Examples 1 to 4 Mixing cobalt oxide, stannic oxide and lithium carbonate having various particle sizes shown in Tables 1 and 2 and firing under the firing temperature conditions shown in Table 1. Thus, a Li, Co, Sn mixed metal oxide was obtained. Li _1.03
After mixing 100 parts by weight of Li and Co mixed 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 were mixed with ethyl acetate / ethyl acetate. Cellsolve 1: 1
(Weight ratio) A liquid dissolved in 60 parts by weight of a mixed solvent was mixed to obtain a slurry coating liquid.

Using a coating machine having a doctor blade coater head, the above coating solution was applied to both sides of an Al foil having a width of 600 mm and a thickness of 15 μm. Coating thickness after double-sided coating 29
It was 0 μ. A solution prepared by dissolving 100 parts by weight of crushed needle coke 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 coating liquid. ..

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

After pressing the above-mentioned two kinds of coated products with a calender roll, both were slit to a width of 41 mm using a slitter. Li _1.03 Co _0.92 Sn _0.02 O ₂ coated product was used as a positive electrode, needle coke coated product was used as a negative electrode, and a polyethylene microporous film (Hypore 4030) was used as a separator.
U Asahi Kasei Kogyo Co., Ltd., using a winding machine, outer diameter 1
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 mixture of propylene carbonate / γ-butyrolactone (1: 1: 2 (weight ratio)) containing LiBF ₄ dissolved at a concentration of 1 M was impregnated as an electrolytic solution. After that, it is sealed and the height A shown in FIG.
A prototype battery can of size was manufactured. This battery was charged at a constant voltage of 4.2 V and the battery performance was evaluated. The results are shown in Tables 1-2.
Shown in.

[0028]

[Table 1]

[0029]

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

[0030]

INDUSTRIAL APPLICABILITY The battery of the present invention is small and lightweight, and particularly excellent in battery efficiency and other cycle characteristics and self-discharge characteristics, and is extremely useful as a power source for small electronic devices, electric vehicles, electric power storage and the like.

[Brief description of drawings]

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 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 (3)

[Claims] 1. A secondary battery comprising a composite metal oxide containing Li and Co as a main component as a positive electrode active material.
Average particle size D (50%) of mixed metal oxides containing
Is in the range of 2 to 10 μ, a secondary battery. 2. The particle size distribution of the composite metal oxide containing Li and Co as main components is D (25%) = 0.5 to 3.0 μ, D
(50%) = 2 to 10 μ, D (75%) = 3.5 to 30
The secondary battery according to claim 1, wherein the secondary battery is in the range of μ. 3. A composite metal oxide containing Li and Co as a main component is obtained by using cobalt oxide having an average particle diameter D (50%) = 0.5 to 1.5 μ as a raw material. The secondary battery according to claim 1 or 2, characterized in that.