JP2003221234A - Lithium-cobalt composite oxide, method of manufacturing it, cathode active material for lithium secondary battery and lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium-cobalt composite oxide having excellent properties as a battery, especially as to a load, a cycling use and a safety, when used as a cathode active material for a lithium secondary battery. <P>SOLUTION: The lithium-cobalt composite oxide is prepared by dry-mixing a composite oxide represented by the general formula: Li<SB>x</SB>Co<SB>1-y</SB>Me<SB>y</SB>O<SB>2-a</SB>[wherein, Me is one or more metal elements selected from V, Cu, Zr, Zn, Mg, Al and Fe; 0.9≤x≤1.1; 0≤y≤0.01; -0.1≤a≤0.1.] and one or more metal oxides selected from Mg, Ti and Zr and heating at 200-700°C to bond the metal oxide on the surface of particles of the composite oxide. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a lithium cobalt-based composite oxide useful as a positive electrode active material for a lithium secondary battery, a method for producing the same, a lithium secondary battery positive electrode active material containing the same, and particularly load characteristics. The present invention relates to a lithium secondary battery having excellent cycle characteristics and safety.

[0002]

2. Description of the Related Art In recent years, portable electric appliances have been made portable.
With the rapid progress of cordless technology, lithium ion secondary batteries have been put to practical use as power sources for small electronic devices such as laptop computers, mobile phones, and video cameras. Regarding this lithium-ion secondary battery, since lithium cobalt oxide was reported to be useful as a positive electrode active material for a lithium-ion secondary battery by Mizushima et al. In 1980 (see Non-Patent Document 1), a lithium-based secondary battery was used. Research and development on complex oxides have been actively promoted, and many proposals have been made so far.

Conventionally, as a technique for increasing the energy density of the positive electrode active material, for example, lithium cobalt oxide is made to be rich in lithium by setting the composition of lithium cobalt oxide to Lix CoO ₂ (where 1.05 ≦ x ≦ 1.3) (Patent Document 1). 1)),
On the contrary, Lix CoO ₂ (where 0 <x ≦ 1) is cobalt-rich (see Patent Document 2),
Those doped with metal ions such as Mn, W, Ni, and La (for example, Patent Documents 3, 4, and 5).
reference. ), The residual Li ₂ CO ₃ in lithium cobalt oxide is 1
Not more than 0% by weight (see Patent Document 6), Lix
CoO ₂ (where 0 <x ≦ 1.25) and the spin concentration at g = 2.15 by an electron spin resonance device is 1 × 10 ¹⁸ spins / g or less (see Patent Document 7). Have been proposed.

Further, as a physical feature of the lithium cobalt oxide-based positive electrode active material, the particle diameter is required, for example, the average particle diameter of LiCoO ₂ is 10 to 150 μm (see Patent Document 8), the average particle of the primary particles. Diameter 0.5 μm or less (see Patent Document 9), average particle diameter 2 to 10 μm, particle size distribution D (25%) 0.5 to 10 μm, D (50%) 2
-10 μm, D (75%) 3.5-30 μm (see Patent Document 10), 10% cumulative particle diameter 3-15 μm, 50%
Cumulative particle size 8 to 35 μm, 90% cumulative particle size 30 to 80
Particle size distribution of μm (see Patent Document 11), average particle size 2
.About.9 .mu.m, of which 1 to 9 .mu.m is 60% or more of the total volume (see Patent Document 12).

Further, Patent Document 13 (Japanese Patent Laid-Open No. 8-2361)
14), a lithium-transition metal composite oxide is used as an active material.
In a lithium secondary battery provided with a positive electrode having
The surface of the positive electrode is BeO, MgO, CaO, SrO, Ba
O, ZnO, Al₂O₃, CeO ₂, As₂O₃Or these
If a coating consisting of a mixture of two or more of
A lithium secondary battery having a pole has been proposed. But
Gara, Patent Document 13 (JP-A-8-236114)
Contains a lithium-transition metal composite oxide, a conductive agent, and a binder.
The positive electrode obtained by heating the mixed positive electrode mixture is treated with the gold
The positive electrode active material itself is coated with a group oxide.
It is not coated.

Further, Patent Document 14 (Japanese Patent Laid-Open No. 11-165)
No. 66), Ti, Al, Sn, Bi, Cu, Si, Ga, W, and Z are formed by fusion around the positive electrode active material by a sputtering method, an electroless plating method, or mechanical mixing.
A battery has been proposed in which a metal containing at least one selected from r, B, and Mo and / or an intermetallic compound obtained by combining a plurality of these and / or an oxide-coated one is used as a positive electrode active material. . However, even if a lithium secondary battery using a material obtained by melting by mechanical mixing of Patent Document 14 (JP-A-11-16566) is used as a positive electrode active material, the load characteristics and cycle are still sufficiently satisfactory. It is not possible to realize characteristics and even safety.

[0007]

[Patent Document 1] Japanese Patent Laid-Open No. 3-127454

[Patent Document 2] Japanese Patent Laid-Open No. 3-134969

[Patent Document 3] Japanese Patent Laid-Open No. 3-201368

[Patent Document 4] JP-A-4-328277

[Patent Document 5] Japanese Patent Laid-Open No. 4-319259

[Patent Document 6] Japanese Unexamined Patent Publication No. 4-56064

[Patent Document 7] Japanese Patent Laid-Open No. 2000-12022

[Patent Document 8] Japanese Unexamined Patent Publication No. 1-304664

[Patent Document 9] Japanese Patent Laid-Open No. 4-33260

[Patent Document 10] Japanese Patent Laid-Open No. 5-94822

[Patent Document 11] JP-A-5-151998

[Patent Document 12] Japanese Patent Laid-Open No. 6-243897

[Patent Document 13] Japanese Unexamined Patent Publication No. 8-236114

[Patent Document 14] Japanese Patent Laid-Open No. 11-16566

[Non-Patent Document 1] Mizushima et al., "Material Research Bulletin", 1980, vol.15, p783-789.

[0008]

Therefore, an object of the present invention is to provide a lithium secondary battery having excellent load characteristics, cycle characteristics, and safety when used as a positive electrode active material of a lithium secondary battery. A lithium cobalt-based composite oxide useful as a positive electrode active material, a method for producing the same, a positive electrode active material containing the same, and a lithium secondary battery using the positive electrode active material.

[0009]

Means for Solving the Problems As a result of intensive studies for achieving the above object, the present inventors have replaced lithium cobalt oxide or a part of cobalt of lithium cobalt oxide with a specific metal element in a specific amount. The composite oxide and at least one or more kinds of metal oxides selected from Mg, Ti or Zr are dry-mixed and subjected to heat treatment in a specific temperature range to form the metal oxides on the surface of the particles of the composite oxide. Completed the present invention by discovering that a lithium secondary battery using a lithium cobalt-based composite oxide adhered with good adhesion as a positive electrode active material will be particularly excellent in load characteristics, cycle characteristics, and safety. Came to do.

That is, the first invention of the present invention is represented by the general formula: L
i_xCo_1-yMe_yO_2-a(Me is V, Cu, Zr, Z
One or more selected from n, Mg, Al or Fe
Represents the metal element of. x is 0.9 ≦ x ≦ 1.1, y is 0
≦ y ≦ 0.01, a has a value of −0.1 ≦ a ≦ 0.1
It ) And a complex oxide represented by Mg, Ti or Zr
Dry blending with at least one metal oxide selected from
And heat treated at 200 to 700 ° C. to obtain the composite oxide.
The metal oxide is attached to the particle surface of
What provides a lithium-cobalt-based composite oxide
Is. Further, the amount of the metal oxide attached is 0.05 to 1
% By weight, and the lithium
Rut-based composite oxide has a BET specific surface area of 0.1 to 2.0 m.
²/ G is particularly preferable.

A second invention of the present invention provides a method for producing a lithium-cobalt complex oxide, which comprises the following first to second steps. First step; _{formula; Li x Co 1-y Me} y O 2-a (Me is
It represents one or more metal elements selected from V, Cu, Zr, Zn, Mg, Al or Fe. x is 0.9 ≦
x ≦ 1.1, y is 0 ≦ y ≦ 0.01, and a is −0.1 ≦ a
It takes a value of ≦ 0.1. ) A complex oxide represented by
a step of dry-mixing at least one metal oxide selected from g, Ti, and Zr to deposit the metal oxide particles on the surface of the composite oxide particles. Second step: a step of heat-treating the composite oxide to which the metal oxide obtained in the first step is attached at 200 to 700 ° C. to obtain a lithium cobalt-based composite oxide. Further, it is preferable to use a metal oxide having an average particle size of 1.0 μm or less as the metal oxide used in the first step.

The third invention of the present invention is to provide a positive electrode active material for a lithium secondary battery, comprising the lithium cobalt-based composite oxide.

A fourth invention of the present invention is to provide a lithium secondary battery characterized by using the positive electrode active material for the lithium secondary battery.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The lithium cobalt-based composite oxide according to the present invention has a general formula: Li _x Co _1-y Me _y O _2-a (Me is V, Cu, Z.
1 or 2 selected from r, Zn, Mg, Al or Fe
Represents one or more metal elements. x is 0.9 ≦ x ≦ 1.1,
The value of y is 0 ≦ y ≦ 0.01, and the value of a is −0.1 ≦ a ≦ 0.1. ) And a complex oxide represented by Mg, Ti or Z
dry mixing with at least one or more metal oxides selected from r, heat treatment in a specific temperature range to adhere the metal oxides to the particle surface of the composite oxide with good adhesion, The lithium-cobalt-based composite oxide according to the present invention is different from one in which the metal oxide is simply attached to the particle surface of the composite oxide by mechanically mixing the composite oxide and the metal oxide. That is, the adhesion of the metal oxide particles to the particle surface of the composite oxide by mechanical mixing is
Whereas the particle surface of the composite oxide and the metal oxide particles adhere to each other in a state where the contact area is small due to weak bonds that are brittle due to static electricity, the lithium cobalt-based composite oxide of the present invention is composed of the composite oxide and the metal. Mechanically dry mix with oxides,
Metal oxide particles are once attached to the surface of the composite oxide particles by static electricity, and this is further heat-treated in a specific temperature range to adhere fine metal oxides to the surface of the composite oxide particles with good adhesion. Therefore, the lithium secondary battery using the lithium cobalt-based composite oxide of the present invention as the positive electrode active material can obtain particularly excellent load characteristics, cycle characteristics, and safety.

In the present invention, the heat treatment temperature is 2
0 to 700 ° C, preferably 300 to 600 ° C,
In the present invention, the heat treatment in this temperature range allows the metal oxide to be more closely adhered to the surface of the particles of the composite oxide. That is, by this heat treatment, the energy of the particle surface of the metal oxide is lowered, and the particle surface of the metal oxide becomes smooth, so that the composite oxide particle and the metal oxide particle are more easily brought into close contact with each other and adhere to each other. It is thought that the nature will increase. This can be confirmed from the fact that the BET specific surface area after the heat treatment is smaller than that before the heat treatment.

In the lithium-cobalt composite oxide of the present invention, the particle surface of the composite oxide includes the surface of primary particles or aggregated particles of primary particles.

In the lithium-cobalt composite oxide of the present invention, the composite oxide is represented by the general formula: Li _x Co _1-y Me _y O _2-a . That is, general formula (1); Li _x CoO _2-a (hereinafter referred to as “composite oxide”) or general formula (2); Li _x Co _{1 -y} Me _y O
_2-a (hereinafter referred to as "composite oxide").

In the above composite oxide, the value of x in the formula showing the amount of lithium atoms is 0.9 to 1.1, preferably 0.95 to 1.05. The value of a in the formula showing the amount of oxygen atoms of the composite oxide is -0.1 to 0.1,
It is preferably −0.05 to 0.05.

The above-mentioned composite oxide is a composite oxide in which part of the cobalt atoms of the above-mentioned composite oxide is replaced with another metal element. In the present invention, the Li site may be irreversibly replaced with another metal element described below in the process of producing the composite oxide. Me in this formula is V, Cu, Zr, Zn, Mg, Al or F.
The value of y in the formula showing the amount of these metal atoms, which represents one or more metal elements selected from e, is greater than 0 and 0.01 or less, preferably 0.001 to 0.005. is there. Further, in the above composite oxide, the value of x in the formula showing the amount of lithium atoms is 0.9 to 1.1, preferably 0.95 to 1.05. The value of a in the formula showing the amount of oxygen atoms of the composite oxide is -0.1 to 0.1,
It is preferably −0.05 to 0.05.

In the present invention, by using a lithium cobalt-based composite oxide having the metal oxide adhered to the particle surface of the composite oxide as a positive electrode active material of a lithium secondary battery, The load characteristics, cycle characteristics, or safety of the lithium secondary battery can be further improved as compared with the case where the lithium cobalt-based composite oxide in which the metal oxide is attached to the particle surface is used.

The physical properties of the complex oxide and the complex oxide are not particularly limited, but the average particle size determined by the laser diffraction method is 1 to 20 μm, preferably 1 to 1.
It is 5 μm, particularly preferably 2 to 10 μm.

In addition to the average particle size being in the above range, the primary particle aggregate has an average particle size of 1.0 to 20 μm, which is an aggregate of primary particles having an average particle size of 0.1 to 2.5 μm. When the obtained lithium cobalt-based composite oxide is used as a positive electrode active material, Li is rapidly inserted and removed, which is preferable. Furthermore, 70% or more, preferably 80% or more of the total volume of the above primary aggregate has a particle size of 1 to 20 μm.
A value of m is more desirable because it allows formation of a coating film having a uniform thickness of the obtained lithium cobalt-based composite oxide. In addition, B of the above-mentioned composite oxide and
ET specific surface area is 0.1 to ² m ² / g, preferably 0.2
~1.5m ² / g, particularly preferably 0.3~1.0m ² /
It is g. When the BET specific surface area is within the range, the lithium secondary battery using the obtained lithium cobalt-based composite oxide as a positive electrode active material has good safety, which is preferable.

The above-mentioned composite oxide and the metal oxide particles attached to the composite oxide are at least one kind of metal oxide selected from Mg, Ti or Zr, and specifically, MgO and TiO. ₂ or ZrO ₂ . The amount of the above-mentioned composite oxide and the metal oxide attached to the surface of the particles of the composite oxide is 0.05 to 1% by weight, preferably 0.1 to 0.5% by weight. The reason for this is that if the amount is less than 0.05% by weight, the relative coverage area of the metal oxide existing on the surface of the particles of the composite oxide is insufficient, so a lithium secondary battery using this as a positive electrode active material is preferable. There is a tendency that load characteristics, cycle characteristics or safety cannot be obtained. On the other hand, even if it exceeds 1% by weight, the above-mentioned effects according to the present invention are only saturated, and conversely the discharge capacity per weight decreases, which is preferable. Absent. Regarding the particle size of the above-mentioned composite oxide and the metal oxide attached to the composite oxide, the particle size obtained from an electron micrograph is 1 μm or less,
Preferably 0.005-1 μm, particularly preferably 0.0
It is 1 to 0.25 μm.

Another physical property of the lithium-cobalt composite oxide according to the present invention is that the BET specific surface area is 0.1 to 0.1.
2.0 m ² / g, preferably from 0.1~1.0m ² / g. When the BET specific surface area is within this range, safety is further improved, which is preferable.

Next, a method for producing the lithium-cobalt composite oxide having the above-mentioned physical properties according to the present invention will be described. The lithium cobalt-based composite oxide of the present invention can be manufactured by carrying out the following first to second steps. First step; at least one selected from the complex oxides or complex oxides thereof and Mg, Ti or Zr.
A step of dry-mixing one or more kinds of metal oxides and adhering the particles of the metal oxides to the surface of the particles of the composite oxides or the composite oxides thereof. Second step: The composite oxide obtained in the first step or the composite oxide particles having the metal oxide adhered to the surface thereof is heat-treated at 200 to 700 ° C. to obtain a lithium cobalt-based composite oxide. Process.

There are no particular restrictions on the physical properties of the raw material composite oxide and the composite oxide used in the first step, but the average particle size determined by the laser diffraction method is 1 to 20 μm.
m, preferably 1 to 15 μm, particularly preferably 2 to 10 μm
In addition to the average particle size of m, the average particle size is in the above range, and in addition, a primary particle aggregate having an average particle size of 1.0 to 20 μm, which is an aggregate of primary particles having an average particle size of 0.1 to 2.5 μm. It is preferable that when the obtained lithium cobalt-based composite oxide is used as a positive electrode active material, Li is rapidly inserted and removed. Furthermore, the above-mentioned primary aggregate has a total volume of 7
It is more desirable for 0% or more, preferably 80% or more, to have a particle size of 1 to 20 μm because a coating film having a uniform thickness can be formed. The raw material composite oxide has a BET specific surface area of 0.1 to ² m ² / g, preferably 0.2 to 1.5.
m ² / g, particularly preferably 0.3~1.0m ² / g. When the BET specific surface area is within the range, safety is good when the obtained lithium cobalt-based composite oxide is used as a positive electrode active material, which is preferable.

The composite oxide or the composite oxide of the raw material having the above physical properties may be obtained by any manufacturing method. As an example, the composite oxide may be a lithium compound and cobalt. The compound may be mixed and fired. Further, the composite oxide is a lithium compound, a cobalt compound and V, Cu, Zr, Zn,
It suffices to mix and fire a transition metal compound containing one or more metal elements selected from Mg, Al or Fe.

More specifically, the above composite oxide is
A lithium compound and a cobalt compound are used as C in the compound.
Molar ratio (Li / Co) of o atom and Li atom is 0.95.
To 1.1, preferably 0.98 to 1.05, and uniformly mixed using a blender or the like, and then the mixture is fired. The firing conditions may be such that the composite oxide can be produced, and the firing temperature is 600 to 1100 ° C., preferably 80.
The firing time is preferably 0 to 1050 ° C. and the firing time is 2 to 24 hours. As the lithium compound and cobalt compound as the raw materials, these oxides, hydroxides, carbonates, nitrates or organic acid salts can be used. The firing atmosphere may be, for example, in the air, an oxygen atmosphere, or an inert atmosphere, and is not particularly limited, and these firings may be performed as many times as necessary.

On the other hand, the above-mentioned composite oxide is one or more selected from the lithium compound and the cobalt compound and V, Cu, Zr, Zn, Mg, Al or Fe in the method for producing the composite oxide. And a transition metal compound of V, Cu, Zr, Zn, Mg, Al or Fe in the transition metal compound with respect to the Co atom in the cobalt compound.
A lithium compound, a cobalt compound and a transition metal compound are mixed so that the molar ratio (Me / Co) of one or more metal atoms (Me) selected from ~ 1100 ° C, preferably 80
It can be produced by performing firing at 0 to 1050 ° C. for 2 to 24 hours. The transition metal compound containing one or more kinds of metal elements selected from V, Cu, Zr, Zn, Mg, Al or Fe as the raw material of the composite oxide is an oxide of these metal elements or water. Oxides, carbonates,
Nitrate or organic acid salt can be used. The firing atmosphere may be, for example, in the air, an oxygen atmosphere, or an inert atmosphere, and is not particularly limited, and these firings may be performed as many times as necessary.

After calcination, the mixture is appropriately cooled and, if necessary, pulverized to obtain the above complex oxide or the complex oxide thereof. The pulverization that is performed as necessary in the above-described method for producing a composite oxide is appropriately performed when the composite oxide obtained by firing is a brittle block-shaped compound oxide. The particles themselves have the above specified average particle size, B
It has an ET specific surface area. That is, the obtained composite oxide or a composite oxide thereof has an average particle diameter of 1.0 to 20 μm, preferably 1.0 to 15 μm, more preferably 2.0 to 10 μm, and a BET specific surface area of 0. .1 to 2.0 m ² / g, preferably 0.2 to 1.5
m ² / g, more preferably from 0.3~1.0m ² / g.

The metal oxide selected from Mg, Ti or Zr as one of the starting materials has the general formula: MgO, TiO ₂ or Zr.
Those selected from O ₂ are preferable, and these are 1 type or 2 types.
It can be used in more than one species. In addition, it is preferable to use fine metal oxides in order to adhere the composite oxide particles or the composite oxide particles to the surface of the composite oxide particles uniformly and with good adhesion. It is 1 μm or less. The reason for this is that when the average particle size of the metal oxide exceeds 1 μm, the metal oxide is less likely to adhere to the surface of the particles of the composite oxide, and the powder tends to be a mixed powder thereof. When the particle size of the metal oxide is less than 0.005 μm, the metal oxide particles adhered on the particle surface of the composite oxide are aggregated, and the primary particles not in contact with the particle surface of the composite oxide tend to return and act as impurities. Therefore, the average particle size of the metal oxide is preferably 0.005 to 1 μm, particularly preferably 0.01 to 1 μm.
It is preferable to use those having a thickness of 0.25 μm.

The amount of the metal oxide as the raw material to be blended is preferably 0.05 to 1% by weight, more preferably 0.1 to 0.5% by weight. The reason for this is that, as described above, when the compounding amount of the metal oxide is less than 0.05% by weight, the relative coating area of the metal oxide existing on the surface of the particles of the composite oxide is insufficient. Lithium secondary batteries used as active materials tend not to have favorable load characteristics, cycle characteristics or safety, while 1% by weight
Even if it exceeds, the above effect according to the present invention is saturated, and the discharge capacity per weight is decreased, which is not preferable.

Next, the above-mentioned raw material composite oxide and metal oxide are uniformly mixed in a predetermined amount by a blender or the like, and at least one kind of fine Mg, Ti or Zr is selected on the particle surface of the composite oxide. The above metal oxide is uniformly attached.

The second step is a step of heat-treating the composite oxide to which the metal oxide obtained in the first step is attached to obtain a target lithium-cobalt-based composite oxide.

The heat treatment temperature is 200 to 700 ° C.
It is preferably 300 to 600 ° C. The reason for this is that if the heat treatment temperature is lower than 200 ° C., the adhesion between the metal oxide and the composite oxide becomes weak, while if it exceeds 700 ° C., the metal oxide forms a solid solution even inside the particles of the composite oxide. For,
A lithium secondary battery using this as a positive electrode active material is not preferable because favorable load characteristics, cycle characteristics or safety cannot be obtained.

After the completion of the second step, if necessary, pulverization and classification may be carried out on the particle surface of the complex oxide according to the present invention or on the particle surface of the complex oxide of at least one selected from Mg, Ti or Zr. A lithium-cobalt-based composite oxide having the above metal oxide adhered thereto with good adhesion is obtained. The pulverization is appropriately performed when the lithium cobalt-based composite oxide is brittle and block-shaped.

The lithium cobalt-based composite oxide of the present invention thus obtained is preferably used as a positive electrode active material of a lithium secondary battery comprising a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte containing a lithium salt. You can

As the positive electrode active material for a lithium secondary battery according to the present invention, the above lithium cobalt composite oxide is used.
The positive electrode active material is a positive electrode mixture for a lithium secondary battery described later,
That is, it is one raw material of a mixture of a positive electrode active material, a conductive agent, a binder, and optionally a filler. The lithium secondary battery positive electrode active material according to the present invention is a lithium cobalt-based composite oxide having the preferable particle size characteristics as described above, and is mixed with other raw materials to prepare a positive electrode mixture. At that time, kneading is easy, and coatability at the time of applying the obtained positive electrode mixture to the positive electrode current collector becomes easy.

The lithium secondary battery according to the present invention uses the positive electrode active material for the lithium secondary battery described above,
It is composed of a negative electrode, a separator, and a non-aqueous electrolyte containing a lithium salt. The positive electrode is formed by, for example, applying and drying a positive electrode mixture on a positive electrode current collector, and the positive electrode mixture is a positive electrode active material, a conductive agent, a binder, and a filler added as necessary. Consists of. In the lithium secondary battery according to the present invention, the positive electrode is uniformly coated with the lithium cobalt-based composite oxide as the positive electrode active material. Therefore, the lithium secondary battery according to the present invention is unlikely to cause deterioration in load characteristics, cycle characteristics, or safety.

The positive electrode current collector is not particularly limited as long as it is an electron conductor that does not cause a chemical change in the constructed battery, and examples thereof include stainless steel, nickel, aluminum, titanium, calcined carbon, aluminum and the like. Examples include stainless steel whose surface is treated with carbon, nickel, titanium, or silver. The surface of these materials may be oxidized and used, or the surface of the current collector may be made uneven by surface treatment. Examples of the form of the current collector include a foil, a film, a sheet, a net, a punched product, a lath body, a porous body, a foam body, a fiber group, and a non-woven fabric molded body. The thickness of the current collector is not particularly limited, but is preferably 1 to 500 μm.

The conductive agent is not particularly limited as long as it is an electron conductive material that does not chemically change in the constructed battery. For example, graphite such as natural graphite and artificial graphite, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, carbon black such as thermal black,
Conductive fibers such as carbon fibers and metal fibers, metal powders such as carbon fluoride, aluminum and nickel powder, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, or A conductive material such as a polyphenylene derivative may be used, and examples of natural graphite include scaly graphite, scaly graphite, and earthy graphite. These can be used alone or in combination of two or more. The compounding ratio of the conductive agent is 1 to 5 in the positive electrode mixture.
It is 0% by weight, preferably 2 to 30% by weight.

Examples of the binder include starch, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene. Enter polymer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer , Vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene - tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride - pentafluoro propylene copolymer, a propylene -
Tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, ethylene- Acrylic acid copolymer or its (Na +) ion cross-linked product,
Ethylene-methacrylic acid copolymer or its (Na +)
Ion cross-linked product, ethylene-methyl acrylate copolymer or its (Na +) ion cross-linked product, ethylene-methyl methacrylate copolymer or its (Na +) ion cross-linked product, polysaccharides such as polyethylene oxide, thermoplastic resin, rubber Examples thereof include polymers having elasticity, and these can be used alone or in combination of two or more.
When a compound containing a functional group that reacts with lithium, such as a polysaccharide, is used, it is preferable to add a compound such as an isocyanate group to deactivate the functional group. The compounding ratio of the binder is 1 to 1 in the positive electrode mixture.
It is 50% by weight, preferably 5 to 15% by weight.

The filler suppresses the volume expansion of the positive electrode in the positive electrode mixture, and is added if necessary. As the filler, any fibrous material that does not cause a chemical change in the constructed battery can be used. For example, olefin polymers such as polypropylene and polyethylene, fibers such as glass and carbon are used.
The addition amount of the filler is not particularly limited, in the positive electrode mixture,
0 to 30% by weight is preferable.

The negative electrode is formed by applying a negative electrode material on the negative electrode current collector and drying it. The negative electrode current collector is not particularly limited as long as it is an electron conductor that does not undergo a chemical change in the constructed battery, but, for example, stainless steel,
Examples thereof include nickel, copper, titanium, aluminum, calcined carbon, copper or stainless steel whose surface is treated with carbon, nickel, titanium and silver, and an aluminum-cadmium alloy. Further, the surface of these materials may be used after being oxidized, or the surface of the current collector may be made uneven by surface treatment. In addition, as the form of the current collector,
For example, foil, film, sheet, net, punched material, lath, porous body, foam, fiber group,
Examples include non-woven fabric moldings. The thickness of the current collector is not particularly limited, but is preferably 1 to 500 μm.

The negative electrode material is not particularly limited, but for example, carbonaceous materials, metal composite oxides, lithium metal, lithium alloys, silicon alloys, tin alloys, metal oxides, conductive polymers. , Chalcogen compounds, Li-C
Examples include o-Ni-based materials. As a carbonaceous material,
For example, a non-graphitizable carbon material, a graphite-based carbon material and the like can be mentioned. As the metal complex oxide, for example, Snp M ¹ 1
-PM ² q Or (In the formula, M ¹ represents one or more elements selected from Mn, Fe, Pb and Ge, M ² represents Al,
B, P, Si, one or more kinds of elements selected from Group 1, Group 2 and Group 3 of the periodic table and a halogen element, and 0 <p
≦ 1, 1 ≦ q ≦ 3, 1 ≦ r ≦ 8 are shown. ), LixFe
Examples thereof include compounds such as ₂ O ₃ (0 ≦ x ≦ 1) and LixWO ₂ (0 ≦ x ≦ 1). As the metal oxide, GeO, G
eO ₂ , SnO, SnO ₂ , PbO, PbO ₂ , Pb
₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , Bi
_{2 O 3, Bi 2 O 4} , Bi 2 O 5 and the like. Examples of the conductive polymer include polyacetylene and poly-p-phenylene.

As the separator, an insulating thin film having a large ion permeability and a predetermined mechanical strength is used. A sheet or non-woven fabric made of an olefin polymer such as polypropylene or glass fiber or polyethylene is used because of its resistance to organic solvents and hydrophobicity. The pore size of the separator may be in a range generally useful for batteries, and for example, 0.01 to 10
μm. The thickness of the separator may be in the range for general batteries, and is, for example, 5 to 300 μm. When a solid electrolyte such as a polymer is used as the electrolyte described below, the solid electrolyte may also serve as the separator.

The non-aqueous electrolyte containing a lithium salt is composed of a non-aqueous electrolyte and a lithium salt. As the non-aqueous electrolyte, a non-aqueous electrolytic solution, an organic solid electrolyte, or an inorganic solid electrolyte is used. Examples of the non-aqueous electrolytic solution include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran and 2-methyl. Tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivative, sulfolane, methylsulfolane, 3-methyl -2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone,
Propylene carbonate derivative, tetrahydrofuran derivative, diethyl ether, 1,3-propane sultone,
An aprotic organic solvent such as methyl propionate or ethyl propionate may be used, or a mixture of two or more aprotic organic solvents may be mentioned.

Examples of the organic solid electrolyte include polyethylene derivatives, polyethylene oxide derivatives or polymers containing them, polypropylene oxide derivatives or polymers containing them, phosphoric ester polymers, polyphosphazenes, polyaziridines, polyethylene sulfides, polyvinyl alcohols, polyfluorides. Examples thereof include polymers containing an ionic dissociative group such as vinylidene chloride and polyhexafluoropropylene, and a mixture of the polymer containing an ionic dissociative group and the above non-aqueous electrolyte.

As the inorganic solid electrolyte, Li nitride,
Can be used a halide, salt oxygen acid, for _{example, Li 3 N, LiI, Li} 5 NI 2, Li 3 N-LiI-
LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiO
_{H, Li 2 SiS 3, Li} 4 SiO 4, Li 4 SiO 4 -Li
_{I-LiOH, Li 3 PO 4} -Li 2 S-SiS 2, and the like phosphorus sulfide compound.

As the lithium salt, one which is soluble in the above non-aqueous electrolyte is used, and examples thereof include LiCl, LiBr,
LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ ,
LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , L
iAsF ₆ , LiSbF ₆ , LiB ₁₀ Cl ₁₀ , LiAl
Cl ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, (CF ₃ S
O ₂ ) ₂ NLi, lithium chloroborane, lower aliphatic lithium carboxylate, lithium tetraphenylborate, imides, and the like, and salts of one kind or a mixture of two or more kinds thereof may be mentioned.

Further, the non-aqueous electrolyte contains the discharge, charge characteristics,
The following compounds can be added for the purpose of improving flame retardancy. For example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivative, sulfur, quinoneimine dye, N-substituted oxazolidinone and N, N-substituted imidazolidine, ethylene glycol dialkyl ether. , Ammonium salt, polyethylene glycol, pyrrole, 2-methoxyethanol, aluminum trichloride, conductive polymer electrode active material monomer, triethylenephosphonamide, trialkylphosphine, morpholine, aryl compound having carbonyl group, hexamethylphosphine Holic triamide and 4-alkylmorpholine, bicyclic tertiary amine,
Examples thereof include oils, phosphonium salts and tertiary sulfonium salts, phosphazenes, carbonates and the like. Further, in order to make the electrolytic solution nonflammable, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride can be contained in the electrolytic solution. Further, the electrolytic solution may contain carbon dioxide gas in order to have suitability for high temperature storage.

The lithium secondary battery according to the present invention is a lithium secondary battery having excellent battery performance, particularly load characteristics and cycle characteristics. The shape of the battery may be any shape such as a button, a sheet, a cylinder, a corner, or a coin shape.

[0053] Conventional lithium secondary battery using LiCoO ₂ is the time of charging and discharging, the electrolytic solution or decomposed by LiCoO ₂ surface, it is known that the film is produced, the result cycle characteristic, load characteristic And it is said that safety will be reduced. On the other hand, the lithium-cobalt composite oxide of the present invention adheres at least one metal oxide selected from Mg, Ti or Zr to the surface of the composite oxide or the particle surface of the composite oxide. By adhering well, the surface of the complex oxide crystal is stabilized, the decomposition of the electrolytic solution in contact is suppressed, the formation of a surface coating is suppressed, and the particle surface of the complex oxide is appropriately exposed. Therefore, the insertion and removal of Li from the surface of the composite oxide crystal is made smoother. Therefore, it is considered that the lithium secondary battery using the lithium-cobalt composite oxide of the present invention as the positive electrode active material has excellent battery performance, particularly load characteristics, cycle characteristics, and safety.

The use of the lithium secondary battery according to the present invention is as follows.
For example, a laptop computer, a laptop computer, a pocket word processor, a mobile phone, a cordless handset, a portable CD player, a radio, an LCD TV, a backup power supply, an electric shaver, a memory card, an electronic device such as a video movie, an automobile, etc. , Electric vehicles, game machines, and other consumer electronic devices.

[0055]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited thereto.

Table 1 shows the physical properties of the raw material metal oxides used in the examples of the present invention.

[Table 1] Note) MgO; Ube Materials Co., Ltd., ZrO ₂ ; Daiichi Rare Element Chemical Industry Co., Ltd., TiO ₂ ; Showa Titanium Co., Ltd.,
ZnO; manufactured by Shodo Kagaku

<Preparation of Lithium Cobaltate> Co ₃ O
₄ (average particle size 2 μm) 40 g and Li ₂ CO ₃ (average particle size 7
(μm) 19 g is weighed and thoroughly mixed in a dry system, and then 100
It was baked at 0 ° C. for 5 hours. The fired product was crushed and classified to obtain Li
CoO ₂ was obtained. The physical properties of this product are shown in Table 2.

[Table 2]

Examples 1 and 2 and Comparative Examples 1 and 2 <First Step> The amount of the metal oxide sample 1 (MgO) shown in Table 3 was 0.2% by weight in the LiCoO ₂ prepared above. In addition, MgO was adhered to the surface of the LiCoO ₂ particles by thoroughly mixing for 60 seconds using a household mixer. In addition, the BET specific surface area after the first step is measured,
The results are shown in Table 3. <Second Step> Next, the LiCoO ₂ to which the MgO obtained in the first step is attached is divided into four, and each sample is heat-treated at the temperature shown in Table 3 for 5 hours and classified to obtain various types of lithium. A cobalt-based composite oxide was obtained. In addition, Table 3 shows the physical properties of the obtained lithium cobalt-based composite oxide.

[Table 3]

From the results in Table 3, comparing the BET specific surface areas of the lithium cobalt-based composite oxides of Example 1 after the first step and after the second step, Example 2 and Comparative Example 1,
No. 2 has a larger decrease rate of the BET specific surface area (m ² / g) after the second step. From this, it can be seen that MgO adheres to the surface of the particles of the composite oxide with good adhesiveness as compared with that of Comparative Example 1. Further, the sample treated at 900 ° C. of Comparative Example 2 has a larger reduction rate of this specific surface area than the lithium cobalt-based composite oxides of Examples 1 and 2. This is MgO
It is considered that this is because part of the solid solution was formed inside the LiCoO ₂ particles. Further, an electron micrograph of the lithium-cobalt composite oxide obtained in Example 1 is shown in FIG. 1, and an enlarged one thereof is shown in FIG.

Examples 3 to 4 and Comparative Example 3 <First Step> Using LiCoO ₂ prepared above, the metal oxides shown in Table 4 were mixed at 0.2% by weight using a household mixer. By mixing thoroughly for 60 seconds, Li
A metal oxide was attached to the surface of the CoO ₂ particles. <Second Step> Next, the composite oxide obtained by adhering various metal oxides obtained in the first step is heat-treated at a temperature shown in Table 4 for 5 hours, and classified to obtain various lithium cobalt-based composites. An oxide was obtained. In addition, various physical properties of the obtained lithium cobalt-based composite oxide are shown in Table 4.

[Table 4]

Example 5 <Preparation of V-substituted complex oxide> Co₃O_Four(Average particle size 2μ
m) 40g and LiCO₃(Average particle size 7μm) 19.5g
And V₂O_Five(Average particle size 8μm) Weigh 0.05g and dry
After being thoroughly mixed with, the mixture was baked at 1000 ° C. for 5 hours. The grill
Grind and classify the product into LiCo_0.999V_0.001O ₂Got
It was Various physical properties of this product are shown in Table 5.

[Table 5] <First Step> V-substituted complex oxide particles are prepared by thoroughly mixing the V-substituted complex oxide prepared above with a metal oxide in an amount of 0.2% by weight using a household mixer for 60 seconds. A metal oxide was attached to the surface. The BET specific surface area after the first step was measured, and the results are shown in Table 10. <Second Step> Next, the composite oxide to which the metal oxide obtained in the first step was attached was heated at 300 ° C. for 5 hours and classified to obtain a lithium cobalt-based composite oxide. In addition, Table 10 shows the main physical properties of the obtained lithium cobalt-based composite oxide.
It was shown to.

Example 6 <Preparation of Cu-substituted complex oxide> Co ₃ O ₄ (average particle size 2 μm
m) 40 g and Li ₂ CO ₃ (average particle size 7 μm) 19.5 g
And 0.06 g of CuCO ₃ (average particle size 7 μm) were weighed, sufficiently mixed in a dry system, and then calcined at 1000 ° C. for 5 hours. The fired product was crushed and classified to obtain LiCo _0.999 Cu _0.001
O ₂ was obtained. Table 6 shows the physical properties of this product.

[Table 6] <First Step> Cu-substituted composite oxide particles are prepared by sufficiently mixing the Cu-substituted composite oxide prepared above with a metal oxide in an amount of 0.2% by weight using a household mixer for 60 seconds. A metal oxide was attached to the surface. In addition, the BET specific surface area after the first step was measured, and the result is shown in Table 10.
It was shown to. <Second Step> Next, the composite oxide to which the metal oxide obtained in the first step was attached was heated at 300 ° C. for 5 hours and classified to obtain a lithium cobalt-based composite oxide. In addition, various physical properties of the obtained lithium cobalt-based composite oxide are shown in Table 10.
It was shown to.

Example 7 <Preparation of Fe-substituted composite oxide> Co ₃ O ₄ (average particle size 2 μ
m) 40 g and Li ₂ CO ₃ (average particle size 7 μm) 19.5 g
And Fe ₃ O ₄ (average particle size 5 μm) 0.04 g are weighed,
After thoroughly dry-mixed, the mixture was baked at 1000 ° C. for 5 hours.
Calcination was pulverized and classified LiCo _0.999 Fe _{0 .001} O ₂
Got Various physical properties of this product are shown in Table 7.

[Table 7] <First Step> Fe-substituted composite oxide particles are prepared by thoroughly mixing the Fe-substituted composite oxide prepared above with a metal oxide in an amount of 0.2% by weight for 60 seconds using a domestic mixer. A metal oxide was attached to the surface. In addition, the BET specific surface area after the first step was measured, and the result is shown in Table 10.
It was shown to. <Second Step> Next, the composite oxide to which the metal oxide obtained in the first step is attached is heat-treated at 300 ° C. for 5 hours,
Classification was performed to obtain a lithium cobalt-based composite oxide. Also,
Table 1 shows the physical properties of the obtained lithium cobalt-based composite oxide.
It was shown at 0.

Example 8 <Preparation of Zn-substituted composite oxide> Co ₃ O ₄ (average particle size 2 μm)
m) 40 g and Li ₂ CO ₃ (average particle size 7 μm) 19.5 g
And ZnO (average particle size 5 μm) 0.04 g were weighed, sufficiently mixed in a dry system, and then baked at 1000 ° C. for 5 hours. The calcined product was crushed and classified to obtain LiCo _0.999 Zn _{0.0 01} O ₂ . Various physical properties of this product are shown in Table 8.

[Table 8] <First Step> Particles of the Zn-substituted composite oxide prepared by thoroughly mixing the Zn-substituted composite oxide prepared above with a metal oxide in an amount of 0.2% by weight for 60 seconds using a domestic mixer. A metal oxide was attached to the surface. In addition, the BET specific surface area after the first step was measured, and the result is shown in Table 10.
It was shown to. <Second Step> Next, the composite oxide to which the metal oxide obtained in the first step is attached is heat-treated at 300 ° C. for 5 hours,
Classification was performed to obtain a lithium cobalt-based composite oxide. Also,
Table 1 shows the physical properties of the obtained lithium cobalt-based composite oxide.
It was shown at 0.

Example 9 <Preparation of Zr-substituted composite oxide> Co ₃ O ₄ (average particle diameter 2 μm)
m) 40 g and Li ₂ CO ₃ (average particle size 7 μm) 19.5 g
And 0.06 g of ZrO ₂ (average particle size 1 μm) are weighed,
After thoroughly dry-mixed, the mixture was baked at 1000 ° C. for 5 hours.
Calcination was pulverized and classified LiCo _0.999 Zr _{0 .001} O ₂
Got Various physical properties of this product are shown in Table 9.

[Table 9] <First step> Zr-substituted composite oxide particles are prepared by thoroughly mixing the Zr-substituted composite oxide prepared above with a metal oxide in an amount of 0.2% by weight using a household mixer for 60 seconds. A metal oxide was attached to the surface. In addition, the BET specific surface area after the first step was measured, and the result is shown in Table 10.
It was shown to. <Second Step> Next, the composite oxide to which the metal oxide obtained in the first step is attached is heat-treated at 300 ° C. for 5 hours,
Classification was performed to obtain a lithium cobalt-based composite oxide. Also,
Table 1 shows the main physical properties of the obtained lithium cobalt-based composite oxide.
It was shown at 0.

[Table 10]

<Battery Performance Test> (I) Preparation of Lithium Secondary Battery; In the lithium cobalt-based composite oxides obtained in Examples 1 to 9 and Comparative Examples 1 to 3 and Example 1 as described above. 91 wt% of the used LiCoO ₂ (Comparative Example 4), 6 wt% of graphite powder, and 3 wt% of polyvinylidene fluoride were mixed as a positive electrode agent, which was dispersed in N-methyl-2-pyrrolidinone to prepare a kneading paste. did. The kneading paste was applied to an aluminum foil, dried, pressed and punched into a disk having a diameter of 15 mm to obtain a positive electrode plate. Using this positive electrode plate, a lithium secondary battery was manufactured by using each member such as a separator, a negative electrode, a positive electrode, a current collector plate, a fitting, an external terminal, and an electrolytic solution. this house,
Metallic lithium foil was used for the negative electrode, and 1: 1 kneading liquid 1 of ethylene carbonate and methyl ethyl carbonate was used as the electrolytic solution.
Using a solution obtained by dissolving LiPF ₆ 1 mol liter.

(1) Evaluation of Battery Performance The prepared lithium secondary battery was operated at room temperature and the following battery performance was evaluated.・ Measurement of capacity retention rate and energy retention rate Constant current voltage (CCCV) 0.5C to the positive electrode at room temperature
The discharge capacity and the energy density were measured with one cycle of charging / discharging in which the battery was charged to 4.3 V and then discharged to 0.2 V at 0.2 C. Next, 20 cycles of charge and discharge in the measurement of the discharge capacity and energy density were performed, the capacity retention rate was calculated by the following equation (1), and the energy retention rate was calculated by the following equation (2). The results are shown in Tables 11 and 12. In addition, under the conditions of the lithium secondary battery using the lithium cobalt-based composite oxide prepared in Example 1, Example 3, Example 4, Comparative Example 1, Comparative Example 3 and Comparative Example 4 as the positive electrode active material. The discharge characteristic diagrams of are shown in FIGS.

[Equation 1]

[Equation 2]

Evaluation of load characteristics First, the positive electrode was charged by constant current voltage (CCCV) charging at 0.5C for 5 hours to 4.3V, and then the discharge rate was 0.2C, 0.5C, 1 Charging / discharging was performed to discharge to 2.7 V at 0.0 C, and these operations were set as one cycle, and the discharge capacity and energy density were measured for each cycle. This cycle was repeated 3 times, and the discharge capacity and energy density of the 3rd cycle were obtained. The results are shown in Table 1.
1 and Table 12. Further, the above operation was discharged for a lithium secondary battery using the lithium-cobalt-based composite oxide prepared in Example 1, Example 3, Example 4, Comparative Example 1, Comparative Example 3 and Comparative Example 4 as a positive electrode active material. Rate 0.2C
However, the same procedure was performed, and discharge characteristic diagrams at 0.2 C, 0.5 C and 1 C are shown in FIGS. 9 to 14, respectively. It should be noted that a higher energy density value indicates that more energy can be used even during high load discharge, and that discharge with a higher voltage is possible when the discharge capacity is the same, that is, the load characteristics are Show that you are excellent.

[Table 11]

[Table 12] From the results of Table 11 and Table 12, the lithium secondary battery using the lithium cobalt-based composite oxide of the present invention as the positive electrode active material has a higher capacity retention rate than the one using the comparative example as the positive electrode active material. It can be seen that the load characteristics are excellent. Further, from the results of FIGS. 2 to 13, a clear shoulder is seen at the end of the discharge curve and a high voltage is maintained until the end of discharge, as compared with the case where Comparative Example 4 is used as the positive electrode active material. I understand.

・ Safety evaluation Koshiishi, Kita, Wada (held from November 21 to 23, 2001, No. 42)
Proceedings of the 42nd Battery Symposium, 462-463), Ota, Oiwa, Ishigaki, et al. (The 42nd Battery Symposium, Proceedings of November 21-23, 2001, pages 470-471) and JP Based on the battery thermal stability evaluation method of Japanese Patent Laid-Open No. 2002-158008, a lithium secondary battery using the lithium cobalt-based composite oxide prepared in Example 2 and Comparative Example 4 as a positive electrode active material was used for a positive electrode at room temperature. Constant current voltage (CC
CV) A positive electrode plate containing a positive electrode active material obtained by decomposing and deintercalating lithium after decomposing a lithium secondary battery in an argon atmosphere after charging to 4.3 V for 5 hours at 0.5 C by charging. Took out. Next, 5.0 m of each positive electrode active material was taken out from the taken out positive plate.
Differential scanning calorimetry (DS) together with 5.0 ml of 1 liter of 1: 1 mixture of ethylene carbonate and methyl ethyl carbonate dissolved in 1 liter of LiPF ₆
Enclosed in a closed cell (SUS cell) for C), heating rate 2 ° C /
The differential calorimetric change was measured with a differential scanning calorimeter (model DSC6200, manufactured by SII Epoll Service) at min. The result of the change in the differential calorific value is shown in FIG. As the heat quantity on the vertical axis of FIG. 15, a value divided by the measured weight of the positive electrode active material was used. It should be noted that in FIG. 15, the temperature is high when the height of the exothermic peak is maximum and the gradient of the calorific value from the start of exothermicity is gentle, that is, the thermal stability, that is, the battery safety is excellent. Indicates. From the result of FIG. 15, Li
In the case of CoO ₂ (Comparative Example 4), the temperature at which the height of the exothermic peak becomes maximum is 196 ° C., whereas in the lithium cobalt-based composite oxide of the present invention (Example 2), the exothermic peak is shown. The temperature at the maximum height of 235 ° C. is 235 ° C., and in comparison with that of LiCoO ₂ (Comparative Example 4), the lithium cobalt-based composite oxide of the present invention has a higher exothermic peak from the exothermic onset temperature. It can be seen that the safety of the battery is excellent because the gradient of the calorific value up to the temperature at which the maximum value is maximum is gentle.

[0070]

As described above, the lithium cobalt-based composite oxide of the present invention has the general formula: Li _x Co _1-y Me _y O _2-a.
(Me is V, Cu, Zr, Zn, Mg, Al or Fe
Represents one or more metal elements selected from x
Is 0.9 ≦ x ≦ 1.1, y is 0 ≦ y ≦ 0.01, and a is −0.1 ≦ a ≦ 0.1. ) Is a lithium-cobalt-based composite oxide in which at least one metal oxide selected from Mg, Ti or Zr is adhered to the particle surface of the composite-oxide represented by the formula (3) with good adhesion. When the product is used as a positive electrode active material of a lithium secondary battery, the lithium secondary battery has excellent load characteristics, cycle characteristics, and safety.

[Brief description of drawings]

FIG. 1 is an electron micrograph showing a state of a particle surface of a lithium cobalt-based composite oxide obtained in Example 1.

FIG. 2 is an electron micrograph showing the state of the particle surface of the lithium-cobalt-based composite oxide obtained in Example 1.

FIG. 3 is a diagram showing cycle characteristics of a lithium secondary battery using the lithium cobalt-based composite oxide obtained in Example 1 as a positive electrode active material.

FIG. 4 is a diagram showing cycle characteristics of a lithium secondary battery in which the lithium cobalt-based composite oxide obtained in Example 3 is used as a positive electrode active material.

FIG. 5 is a diagram showing cycle characteristics of a lithium secondary battery in which the lithium cobalt-based composite oxide obtained in Example 4 is used as a positive electrode active material.

FIG. 6 is a diagram showing cycle characteristics of a lithium secondary battery using the lithium cobalt-based composite oxide obtained in Comparative Example 1 as a positive electrode active material.

FIG. 7 is a diagram showing cycle characteristics of a lithium secondary battery using the lithium cobalt-based composite oxide obtained in Comparative Example 3 as a positive electrode active material.

FIG. 8 is a diagram showing cycle characteristics of a lithium secondary battery using LiCoO _{2 of} Comparative Example 4 as a positive electrode active material.

9 is a graph of 0.2 of a lithium secondary battery using the lithium-cobalt composite oxide obtained in Example 1 as a positive electrode active material.
The figure which shows the load characteristic in C, 0.5C, and 1C.

FIG. 10 is a graph of 0.2 of a lithium secondary battery using the lithium-cobalt-based composite oxide obtained in Example 3 as a positive electrode active material.
The figure which shows the load characteristic in C, 0.5C, and 1C.

11 is a graph showing 0.2 of a lithium secondary battery using the lithium-cobalt-based composite oxide obtained in Example 4 as a positive electrode active material.
The figure which shows the load characteristic in C, 0.5C, and 1C.

FIG. 12 is a graph of 0.2 of a lithium secondary battery using the lithium cobalt-based composite oxide obtained in Comparative Example 1 as a positive electrode active material.
The figure which shows the load characteristic in C, 0.5C, and 1C.

13 is a graph showing 0.2 of a lithium secondary battery using the lithium-cobalt-based composite oxide obtained in Comparative Example 3 as a positive electrode active material.
The figure which shows the load characteristic in C, 0.5C, and 1C.

FIG. 14 is a diagram showing load characteristics at 0.2C, 0.5C, and 1C of a lithium secondary battery using LiCoO _{2 of} Comparative Example 4 as a positive electrode active material.

FIG. 15 is a diagram showing a change in differential calorific value of the positive electrode active material obtained by deintercalating lithium from the lithium cobalt-based composite oxides obtained in Example 2 and Comparative Example 4.

Continued front page    F-term (reference) 4G048 AA04 AB01 AB04 AB06 AC06                       AD03 AD06 AE05                 5H029 AJ02 AJ05 AJ12 AK03 AL02                       AL03 AL04 AL06 AL07 AL11                       AL12 AL16 AM02 AM03 AM04                       AM05 AM07 AM16 CJ02 CJ08                       CJ22 DJ16 EJ04 EJ12 HJ01                       HJ02 HJ05 HJ07 HJ14                 5H050 AA02 AA07 AA15 BA16 BA17                       CA07 CA08 CA09 CB02 CB03                       CB05 CB07 CB08 CB11 CB12                       CB20 CB22 EA09 EA24 FA17                       GA02 GA10 GA22 HA01 HA02                       HA05 HA07 HA14

Claims (7)

[Claims] 1. A general formula; Li _x Co _1-y Me _y O _2-a (Me
Represents one or more metal elements selected from V, Cu, Zr, Zn, Mg, Al or Fe. x is 0.
9 ≦ x ≦ 1.1, y is 0 ≦ y ≦ 0.01, and a is −0.1
It takes a value of ≦ a ≦ 0.1. ) A complex oxide represented by
At least one metal oxide selected from Mg, Ti, or Zr is dry-mixed, and heat-treated at 200 to 700 ° C. to deposit the metal oxide on the particle surface of the composite oxide. Characteristic lithium-cobalt type composite oxide. 2. The adhesion amount of the metal oxide is 0.05 to 1
The lithium cobalt-based composite oxide according to claim 1, which is contained in a weight percentage. 3. A BET specific surface area of 0.1 to 2.0 m ² /
The lithium cobalt-based composite oxide according to claim 1, which is g. 4. A method for producing a lithium-cobalt-based composite oxide, which comprises the following first to second steps. First step; _{formula; Li x Co 1-y Me} y O 2-a (Me is
It represents one or more metal elements selected from V, Cu, Zr, Zn, Mg, Al or Fe. x is 0.9 ≦
x ≦ 1.1, y is 0 ≦ y ≦ 0.1, a is −0.1 ≦ a ≦
It takes a value of 0.1. ) And a composite oxide represented by
A step of dry-mixing with at least one metal oxide selected from Ti or Zr and adhering the particles of the metal oxide to the surface of the particles of the composite oxide. Second step: a step of heat-treating the composite oxide to which the metal oxide obtained in the first step is attached at 200 to 700 ° C. to obtain a lithium cobalt-based composite oxide. 5. The method for producing a lithium-cobalt composite oxide according to claim 4, wherein the metal oxide used in the first step has an average particle size of 1.0 μm or less. 6. A positive electrode active material for a lithium secondary battery, comprising the lithium-cobalt composite oxide according to any one of claims 1 to 3. 7. A lithium secondary battery comprising the positive electrode active material of the lithium secondary battery according to claim 6.