JP4245888B2 - Lithium cobalt based composite oxide, method for producing the same, lithium secondary battery positive electrode active material, and lithium secondary battery - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention is a lithium cobalt based composite oxide useful as a positive electrode active material of a lithium secondary battery, a method for producing the same, a lithium secondary battery positive electrode active material containing the same, and particularly excellent in load characteristics, cycle characteristics and safety. The present invention relates to a lithium secondary battery.
[0002]
[Prior art]
In recent years, as home appliances have become portable and cordless, 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. With respect to this lithium ion secondary battery, since a report that lithium cobalt oxide was useful as a positive electrode active material of a lithium ion secondary battery in 1980 by Mizushima et al. Research and development on complex oxides are actively underway, and many proposals have been made so far.
[0003]
Conventionally, as a technique for increasing the energy density of the positive electrode active material, for example, the composition of lithium cobaltate is Lix CoO. ₂ (However, 1.05 ≦ x ≦ 1.3) to make it rich in lithium (see Patent Document 1), conversely, Lix CoO ₂ (However, it is made cobalt rich by setting 0 <x ≦ 1) (refer to Patent Document 2), doped with metal ions such as Mn, W, Ni, La (for example, Patent Document 3, Patent Document 2) 4 and Patent Document 5), residual Li in lithium cobaltate ₂ CO _Three Of 10% by weight or less (see Patent Document 6), LixCoO ₂ (Where 0 <x ≦ 1.25) and the spin concentration at g = 2.15 by the electron spin resonance apparatus is 1 × 10 ¹⁸ The number of pieces / g or less (see Patent Document 7) has been proposed.
[0004]
Further, as a physical feature of the lithium cobaltate-based positive electrode active material, the particle size is a requirement, for example, LiCoO ₂ Average particle diameter of 10 to 150 μm (see Patent Document 8), average primary particle diameter of 0.5 μm or less (see Patent Document 9), average particle diameter of 2 to 10 μm, particle size distribution D (25%) 5 to 10 μm, D (50%) 2 to 10 μm, D (75%) 3.5 to 30 μm (see Patent Document 10), 10% cumulative particle diameter 3 to 15 μm, 50% cumulative particle diameter 8 to 35 μm, 90 % Cumulative particle diameter of 30 to 80 μm (see Patent Document 11), average particle diameter of 2 to 9 μm, of which 1 to 9 μm is 60% or more of the total volume (see Patent Document 12). Yes.
[0005]
Patent Document 13 (JP-A-8-236114) discloses that in a lithium secondary battery including a positive electrode using a lithium transition metal composite oxide as an active material, the surface of the positive electrode is BeO, MgO, CaO, SrO, BaO, ZnO, Al ₂ O _Three , CeO ₂ , As ₂ O _Three Alternatively, a lithium secondary battery having a positive electrode formed with a coating formed of a mixture of two or more of these has been proposed.
However, Patent Document 13 (JP-A-8-236114) discloses that a positive electrode obtained by heat-treating a positive electrode mixture in which a lithium transition metal composite oxide, a conductive agent, and a binder are mixed with the metal oxide. The coating is performed, and the cathode active material itself is not coated.
[0006]
In Patent Document 14 (Japanese Patent Laid-Open No. 11-16666), Ti, Al, Sn, Bi, Cu are fused around the positive electrode active material by sputtering, electroless plating, or mechanical mixing. , Si, Ga, W, Zr, B, and a metal containing at least one selected from Mo and / or an intermetallic compound obtained by combining a plurality of these and / or an oxide-coated one is used as the positive electrode active material Batteries have been proposed.
However, even when a lithium secondary battery using a positive electrode active material obtained by melting by mechanical mixing in Patent Document 14 (Japanese Patent Application Laid-Open No. 11-16666) is used, the load characteristics and cycle are still satisfactory. Characteristics and even safety cannot be realized.
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 3-127454
[Patent Document 2]
JP-A-3-134969
[Patent Document 3]
Japanese Patent Laid-Open No. 3-201368
[Patent Document 4]
JP-A-4-328277
[Patent Document 5]
JP-A-4-319259
[Patent Document 6]
JP-A-4-56064
[Patent Document 7]
Japanese Patent Laid-Open No. 2000-12022
[Patent Document 8]
JP-A-1-304664
[Patent Document 9]
JP-A-4-33260
[Patent Document 10]
Japanese Patent Laid-Open No. 5-94822
[Patent Document 11]
Japanese Patent Laid-Open No. 5-151998
[Patent Document 12]
JP-A-6-2443897
[Patent Document 13]
JP-A-8-236114
[Patent Document 14]
Japanese Patent Laid-Open No. 11-16666
[Non-Patent Document 1]
Mizushima et al., "Material Research Bulletin", 1980, vol.15, p783-789
[0008]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a lithium cobalt-based material useful as a positive electrode active material for a lithium secondary battery particularly excellent in load characteristics, cycle characteristics, and safety when used as a positive electrode active material for a lithium secondary battery. It is to provide a composite oxide, a production method thereof, 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 in order to achieve the above object, the present inventors have found that lithium cobaltate or a complex oxide obtained by substituting a part of cobalt of lithium cobaltate with a specific metal element, Mg, Ti or Lithium cobalt system in which at least one metal oxide selected from Zr is dry-mixed and heat-treated in a specific temperature range to adhere the metal oxide to the particle surface of the composite oxide with good adhesion. A lithium secondary battery using a composite oxide as a positive electrode active material has been found to be particularly excellent in load characteristics, cycle characteristics, and safety, and has completed the present invention.
[0010]
That is, the first invention of the present invention has the 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, and y is 0 ≦ y. ≦ 0.01, a takes a value of −0.1 ≦ a ≦ 0.1.) And at least one metal oxide selected from Mg, Ti, or Zr. 200 ~ dry mix 600 The present invention provides a lithium-cobalt-based composite oxide obtained by heat-treating at a temperature of 0 ° C. to adhere the metal oxide to the surface of the composite oxide particles. Further, the adhesion amount of the metal oxide is preferably 0.05 to 1% by weight, and the BET specific surface area of the lithium cobalt composite oxide is 0.1 to 2.0 m. ² / G is particularly preferable.
[0011]
Moreover, 2nd invention of this invention provides the manufacturing method of the lithium cobalt type complex oxide characterized by including the following 1st-2nd processes.
First step; 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, and y is 0 ≦ y. ≦ 0.01 , A takes a value of −0.1 ≦ a ≦ 0.1. ) And at least one metal oxide selected from Mg, Ti, or Zr are dry-mixed to adhere the metal oxide particles to the surface of the composite oxide particles.
2nd process; The process of obtaining the lithium cobalt type complex oxide by heat-processing at 200-600 degreeC the complex oxide to which the metal oxide obtained by the 1st process was made to adhere. The metal oxide used in the first step is preferably one having an average particle size of 1.0 μm or less.
[0012]
A third invention of the present invention provides a positive electrode active material for a lithium secondary battery, characterized in that it contains the lithium cobalt complex oxide.
[0013]
According to a fourth aspect of the present invention, there is provided a lithium secondary battery using the lithium secondary battery positive electrode active material.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The lithium cobalt complex oxide according to the present invention has 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, and y is 0 ≦ y. ≦ 0.01, a takes a value of −0.1 ≦ a ≦ 0.1.) And at least one metal oxide selected from Mg, Ti, or Zr. The mixture is dry-mixed and heat-treated in a specific temperature range to adhere the metal oxide to the surface of the composite oxide particles with good adhesion. The lithium cobalt composite oxide according to the present invention is the composite This is different from the case where the metal oxide is simply adhered to the particle surface of the composite oxide by mechanically mixing the oxide and the metal oxide.
That is, the metal oxide particles adhere to the surface of the composite oxide particles by mechanical mixing. The composite oxide particle surfaces 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. In contrast, the lithium-cobalt composite oxide of the present invention mechanically dry-mixes the composite oxide and metal oxide, and temporarily attaches the metal oxide particles to the composite oxide particle surface by static electricity. Furthermore, this was heat-treated in a specific temperature range, and a fine metal oxide was adhered to the surface of the composite oxide particles with good adhesion. A lithium secondary battery using a product as a positive electrode active material can obtain particularly excellent load characteristics, cycle characteristics, and safety.
[0015]
In this invention, the said heat processing temperature is 200-700 degreeC, Preferably it is 300-600 degreeC, and makes a metal oxide adhere more closely to the particle | grain surface of complex oxide by heat-processing in this temperature range in this invention. Can be attached. That is, by this heat treatment, the energy of the metal oxide particle surface is reduced, and the surface of the metal oxide particle becomes smooth, so that the composite oxide particle and the metal oxide particle are more easily brought into close contact with each other. It is thought that the nature increases.
This can also be confirmed from the fact that the BET specific surface area is reduced after heat treatment compared to before heat treatment.
[0016]
In the lithium cobalt composite oxide of the present invention, the particle surface of the composite oxide includes primary particles or the surface of aggregated particles in which primary particles are aggregated.
[0017]
In the lithium cobalt composite oxide of the present invention, the composite oxide has the general formula: Li _x Co _1-y Me _y O _2-a It is represented by That is, the general formula (1); Li _x CoO _2-a (Hereinafter referred to as “1) complex oxide”) or general formula (2); Li _x Co _1-y Me _y O _2-a (Hereinafter referred to as “mixed oxide of (2)”).
[0018]
In the composite oxide of (1), the value of x in the formula indicating the amount of lithium atoms is 0.9 to 1.1, preferably 0.95 to 1.05. The value of a in the formula indicating the amount of oxygen atoms in the composite oxide is −0.1 to 0.1, preferably −0.05 to 0.05.
[0019]
The complex oxide (2) is a complex oxide obtained by substituting a part of cobalt atoms of the complex oxide (1) with another metal element. In the present invention, the following other metal element may be irreversibly substituted at the Li site in the production process of the composite oxide of (2). Me in this formula represents one or more metal elements selected from V, Cu, Zr, Zn, Mg, Al or Fe, and the value of y in the formula indicating the amount of these metal atoms is , More than 0 and 0.01 or less, preferably 0.001 to 0.005. In the composite oxide of (2), the value of x in the formula indicating the amount of lithium atoms is 0.9 to 1.1, preferably 0.95 to 1.05. The value of a in the formula indicating the amount of oxygen atoms in the composite oxide is −0.1 to 0.1, preferably −0.05 to 0.05.
[0020]
In the present invention, the lithium cobalt based composite oxide in which the metal oxide is adhered to the particle surface of the composite oxide of (2) is used as a positive electrode active material of a lithium secondary battery, whereby the composite of (1) is used. The load characteristics, cycle characteristics, or safety of the lithium secondary battery can be further improved as compared with those using the lithium cobalt composite oxide in which the metal oxide is attached to the oxide particle surface.
[0021]
The physical properties of the composite oxide (1) and the composite oxide (2) are not particularly limited, but the average particle size determined by the laser diffraction method is 1 to 20 μm, preferably 1 to 15 μm, particularly preferably 2 -10 μm.
[0022]
In addition to the average particle size being in the above range, it is further obtained that the primary particle aggregate is an average particle size of 1.0 to 20 μm formed by aggregation of primary particles having an average particle size of 0.1 to 2.5 μm. When the lithium cobalt based composite oxide is used as the positive electrode active material, Li is preferably desorbed and inserted quickly. Furthermore, when the primary aggregate is 70% or more of the total volume, and preferably 80% or more has a particle size of 1 to 20 μm, it is possible to form a coating film having a uniform thickness of the obtained lithium cobalt composite oxide. This is more desirable. The BET specific surface area of the composite oxide (1) and the composite oxide (2) is 0.1-2 m. ² / G, preferably 0.2 to 1.5 m ² / G, particularly preferably 0.3 to 1.0 m ² / G. It is preferable that the BET specific surface area is within the above range because the lithium secondary battery using the obtained lithium cobalt composite oxide as the positive electrode active material has good safety.
[0023]
The metal oxide particles attached to the composite oxide of (1) and the composite oxide of (2) are at least one metal oxide selected from Mg, Ti, or Zr. Specifically, MgO, TiO ₂ Or ZrO ₂ It is.
The amount of the metal oxide attached to the particle surface of the composite oxide (1) and the composite oxide (2) is 0.05 to 1% by weight, preferably 0.1 to 0.5% by weight. It is preferable. The reason for this is that if the amount is less than 0.05% by weight, the relative coverage area of the metal oxide present on the surface of the composite oxide particles 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 tends not to be obtained. Absent.
The particle size of the metal oxide adhering to the composite oxide (1) and the composite oxide (2) is 1 μm or less, preferably 0.005 to 1 μm, particularly preferably from the electron micrograph. 0.01 to 0.25 μm.
[0024]
Other physical properties of the lithium cobalt composite oxide according to the present invention include a BET specific surface area of 0.1 to 2.0 m. ² / G, preferably 0.1 to 1.0 m ² / G. It is preferable that the BET specific surface area be within this range because safety is further improved.
[0025]
Subsequently, the manufacturing method of the lithium cobalt type complex oxide which has the said physical property concerning this invention is demonstrated.
The lithium cobalt composite oxide of the present invention can be produced by carrying out the following first to second steps.
First step: The composite oxide of (1) or the composite oxide of (2) and at least one metal oxide selected from Mg, Ti, or Zr are dry-mixed and the composite oxidation of (1) above A step of adhering the metal oxide particles to the surface of the product or the composite oxide particles of (2).
Second step: Lithium cobalt obtained by heat-treating the surface of the composite oxide (1) or the composite oxide particle (2) obtained in the first step on the surface of the composite oxide, at 200 to 700 ° C. A step of obtaining a composite oxide.
[0026]
The physical properties of the composite oxide (1) and the composite oxide (2) used in the first step are not particularly limited, but the average particle size determined by the laser diffraction method is 1 to 20 μm, preferably 1 to 15 μm, and particularly preferably 2 to 10 μm. In addition to the average particle size being in the above range, the average particle size of 1.0 to 2.5 μm is obtained by collecting primary particles having an average particle size of 0.1 to 2.5 μm. A primary particle aggregate of 20 μm is preferable because Li can be desorbed and inserted quickly when the obtained lithium cobalt composite oxide is used as a positive electrode active material. Furthermore, it is more desirable that the primary aggregate has a particle size of 1 to 20 μm, with 70% or more, preferably 80% or more of the total volume, being able to form a uniform thickness coating film. The composite oxide of the raw material 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 to 1.0 m ² / G. It is preferable that the BET specific surface area be within the above range because the resulting lithium cobalt composite oxide has good safety when used as the positive electrode active material.
[0027]
The composite oxide of (1) or the composite oxide of (2) as the raw material having the above physical properties may be obtained by any production method. For example, the composite oxide of (1) is used. What is necessary is just to mix and bake a lithium compound and a cobalt compound. The composite oxide of (2) is a lithium compound, a cobalt compound, and a transition metal compound containing one or more metal elements selected from V, Cu, Zr, Zn, Mg, Al or Fe. What is necessary is just to mix and bake.
[0028]
More specifically, in the composite oxide of (1), the lithium compound and the cobalt compound are 0.95 to 1.1 in terms of the molar ratio of Co atom to Li atom (Li / Co) in the compound. Preferably, it is set to 0.98 to 1.05, and is uniformly mixed using a blender or the like, and then the mixture is fired. The firing conditions may be a temperature at which the composite oxide can be produced. The firing temperature is 600 to 1100 ° C., preferably 800 to 1050 ° C., and the firing time is preferably 2 to 24 hours. As the raw material lithium compound and cobalt compound, these oxides, hydroxides, carbonates, nitrates or organic acid salts can be used. The firing atmosphere may be performed, for example, in the air, in an oxygen atmosphere, or in an inert atmosphere, and is not particularly limited, and these firings may be performed as many times as necessary.
[0029]
On the other hand, the composite oxide of (2) is one type selected from a lithium compound and a cobalt compound and V, Cu, Zr, Zn, Mg, Al or Fe in the method of producing a composite oxide of (1) or Two or more transition metal compounds are combined with one or two or more metal atoms (Me) selected from V, Cu, Zr, Zn, Mg, Al, or Fe in the transition metal compound with respect to the Co atom in the cobalt compound. ) And a lithium compound, a cobalt compound, and a transition metal compound are mixed so that the molar ratio (Me / Co) is greater than 0 and 0.01 or less, and is 600 to 1100 ° C., preferably 800 to 1050 ° C. It can manufacture by baking for 24 hours. The transition metal compound containing one or more metal elements selected from V, Cu, Zr, Zn, Mg, Al or Fe as a raw material of the composite oxide of (2) is an oxidation of these metal elements. Substances, hydroxides, carbonates, nitrates or organic acid salts can be used. The firing atmosphere may be performed, for example, in the air, in an oxygen atmosphere, or in an inert atmosphere, and is not particularly limited, and these firings may be performed as many times as necessary.
[0030]
After firing, the mixture is appropriately cooled and pulverized as necessary to obtain the composite oxide (1) or the composite oxide (2).
The pulverization performed as necessary in the composite oxide production methods (1) and (2) is appropriately performed when the composite oxide obtained by firing is in a brittle and bonded block form. However, the composite oxide particles themselves have the above-described specific average particle diameter and BET specific surface area. That is, the obtained composite oxide of (1) or (2) has an average particle size of 1.0 to 20 μm, preferably 1.0 to 15 μm, more preferably 2.0 to 10 μm. , BET specific surface area is 0.1-2.0m ² / G, preferably 0.2 to 1.5 m ² / G, more preferably 0.3 to 1.0 m ² / G.
[0031]
The metal oxide selected from Mg, Ti or Zr as one raw material has a general formula; MgO, TiO ₂ Or ZrO ₂ What is chosen from these is preferable, and these can be used by 1 type (s) or 2 or more types.
Further, it is preferable to use fine metal oxides for the purpose of adhering to the surface of the composite oxide particles of the above (1) or the composite oxide particles of the above (2) uniformly and with good adhesion. The required average particle size 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 difficult to adhere to the particle surface of the composite oxide, and tends to be a mixed powder of these, whereas the metal oxide If the particle size of the particles is less than 0.005 μm, the metal oxide particles adhering to the surface of the composite oxide are aggregated, and the primary particles not in contact with the surface of the composite oxide tend to act as impurities in return. Therefore, the average particle diameter of the metal oxide is preferably 0.005 to 1 μm, and particularly preferably 0.01 to 0.25 μm.
[0032]
The blending amount of the metal oxides of these raw materials is 0.05 to 1% by weight, preferably 0.1 to 0.5% by weight. This is because, as described above, if the amount of the metal oxide is less than 0.05% by weight, the relative coverage area of the metal oxide present on the particle surface of the composite oxide is insufficient. The lithium secondary battery used as the active material tends to fail to obtain preferable load characteristics, cycle characteristics or safety. On the other hand, exceeding 1% by weight only saturates the above effect according to the present invention. In addition, the discharge capacity per weight is not preferable.
[0033]
Next, a predetermined amount of the composite oxide and metal oxide as described above are uniformly mixed by a blender or the like, and at least one metal selected from fine Mg, Ti, or Zr on the particle surface of the composite oxide. Deposit oxide uniformly.
[0034]
The second step is a step of obtaining a target lithium cobalt composite oxide by heat-treating the composite oxide to which the metal oxide obtained in the first step is attached.
[0035]
The temperature for the heat treatment is 200 to 700 ° C, preferably 300 to 600 ° C. The reason for this is that when the heat treatment temperature is less than 200 ° C., the adhesion between the metal oxide and the composite oxide becomes weak, whereas when it exceeds 700 ° C., the metal oxide dissolves into the inside of the composite oxide particles. Therefore, a lithium secondary battery using this as a positive electrode active material is not preferable because preferable load characteristics, cycle characteristics, or safety cannot be obtained.
[0036]
After completion of the second step, if necessary, pulverized and classified, and at least selected from Mg, Ti, or Zr on the surface of the composite oxide (1) or the composite oxide (2) according to the present invention. A lithium cobalt composite oxide having one or more metal oxides adhered thereto with good adhesion is obtained. The pulverization is appropriately performed when the lithium cobalt composite oxide is brittle and in a block shape.
[0037]
The lithium cobalt composite oxide of the present invention thus obtained can be suitably used as a positive electrode active material for a lithium secondary battery comprising a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte containing a lithium salt.
[0038]
The lithium cobalt based composite oxide is used for the positive electrode active material of the lithium secondary battery according to the present invention. The positive electrode active material is a raw material of a mixture of a positive electrode mixture of a lithium secondary battery, which will be described later, that is, a positive electrode active material, a conductive agent, a binder, and, if necessary, a filler. The lithium secondary battery positive electrode active material according to the present invention is a lithium cobalt composite oxide having the above-mentioned preferable particle size characteristics, and is mixed with other raw materials to prepare a positive electrode mixture. At this time, kneading is easy, and the coating property when the obtained positive electrode mixture is applied to the positive electrode current collector becomes easy.
[0039]
The lithium secondary battery according to the present invention uses the above-described lithium secondary battery positive electrode active material, and includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte containing a lithium salt. The positive electrode is formed, for example, by applying and drying a positive electrode mixture on a positive electrode current collector, and the positive electrode mixture includes 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 lithium cobalt composite oxide, which is a positive electrode active material, is uniformly applied to the positive electrode.
For this reason, especially the lithium secondary battery which concerns on this invention does not produce the fall of a load characteristic, cycling characteristics, or safety | security.
[0040]
The positive electrode current collector is not particularly limited as long as it is an electronic conductor that does not cause a chemical change in the constituted battery. For example, stainless steel, nickel, aluminum, titanium, calcined carbon, aluminum, and stainless steel Examples of the surface include carbon, nickel, titanium, and silver surface-treated. The surface of these materials may be oxidized and used, or the current collector surface may be provided with irregularities by surface treatment. Examples of the current collector include foils, films, sheets, nets, punched ones, lath bodies, porous bodies, foam bodies, fiber groups, nonwoven fabric molded bodies, and the like. The thickness of the current collector is not particularly limited, but is preferably 1 to 500 μm.
[0041]
The conductive agent is not particularly limited as long as it is an electron conductive material that does not cause a chemical 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 fiber and metal fiber, Examples include 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, and conductive materials such as polyphenylene derivatives. Examples of graphite include scaly graphite, scaly graphite, and earthy graphite. These can be used alone or in combination of two or more. The blending ratio of the conductive agent is 1 to 50% by weight, preferably 2 to 30% by weight in the positive electrode mixture.
[0042]
Examples of the binder include starch, polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, regenerated cellulose, diacetylcellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer ( EPDM), sulfonated EPDM, styrene butadiene rubber, fluoro rubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, fluorinated Vinylidene-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene Oroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetra Fluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, ethylene-acrylic acid copolymer or its (Na +) ionic crosslinked product, ethylene-methacrylic acid copolymer or its (Na + ) Ionic crosslinked body, ethylene-methyl acrylate copolymer or its (Na +) ionic crosslinked body, ethylene-methyl methacrylate copolymer or its (Na +) ionic crosslinked body, polysaccharide such as polyethylene oxide, thermoplastic resin Polymers having rubber elasticity, and these may be used individually or in combination. In addition, when using the compound containing a functional group which reacts with lithium like a polysaccharide, it is preferable to add the compound like an isocyanate group and to deactivate the functional group, for example. The blending ratio of the binder is 1 to 50% by weight, preferably 5 to 15% by weight in the positive electrode mixture.
[0043]
The filler suppresses the volume expansion of the positive electrode in the positive electrode mixture, and is added as necessary. As the filler, any fibrous material can be used as long as it does not cause a chemical change in the constructed battery. For example, olefinic polymers such as polypropylene and polyethylene, and fibers such as glass and carbon are used. Although the addition amount of a filler is not specifically limited, 0-30 weight% is preferable in a positive mix.
[0044]
The negative electrode is formed by applying and drying a negative electrode material on the negative electrode current collector. The negative electrode current collector is not particularly limited as long as it is an electronic conductor that does not cause a chemical change in the constructed battery. For example, stainless steel, nickel, copper, titanium, aluminum, calcined carbon, copper or stainless steel Examples of the steel surface include carbon, nickel, titanium, silver surface-treated, 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 used with surface roughness by surface treatment. Examples of the current collector include foils, films, sheets, nets, punched ones, lath bodies, porous bodies, foam bodies, fiber groups, nonwoven fabric molded bodies, and the like. The thickness of the current collector is not particularly limited, but is preferably 1 to 500 μm.
[0045]
The negative electrode material is not particularly limited, and examples thereof include carbonaceous materials, metal composite oxides, lithium metals, lithium alloys, silicon-based alloys, tin-based alloys, metal oxides, conductive polymers, and chalcogen compounds. And Li—Co—Ni-based materials. Examples of the carbonaceous material include non-graphitizable carbon materials and graphite-based carbon materials. Examples of the metal composite oxide include Snp M ¹ 1-pM ² q Or (wherein M ¹ Represents one or more elements selected from Mn, Fe, Pb and Ge; ² Represents one or more elements selected from Al, B, P, Si, Periodic Table Group 1, Group 2, Group 3 and halogen elements, and 0 <p ≦ 1, 1 ≦ q ≦ 3, 1 <= R <= 8 is shown. ), LixFe ₂ O _Three (0 ≦ x ≦ 1), LixWO ₂ And compounds such as (0 ≦ x ≦ 1). As the metal oxide, GeO, GeO ₂ , SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O _Three , Pb _Three O _Four , Sb ₂ O _Three , Sb ₂ O _Four , Sb ₂ O _Five , Bi ₂ O _Three , Bi ₂ O _Four , Bi ₂ O _Five Etc. Examples of the conductive polymer include polyacetylene and poly-p-funylene.
[0046]
As the separator, an insulating thin film having a large ion permeability and a predetermined mechanical strength is used. Sheets and non-woven fabrics made of olefin polymers such as polypropylene, glass fibers or polyethylene are used because of their organic solvent resistance and hydrophobicity. The pore diameter of the separator may be in a range generally useful for batteries, for example, 0.01 to 10 μm. The thickness of the separator may be in a range for a general battery, for example, 5 to 300 μm. When a solid electrolyte such as a polymer is used as the electrolyte described later, the solid electrolyte may also serve as a separator.
[0047]
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 electrolyte, an organic solid electrolyte, or an inorganic solid electrolyte is used. Examples of the non-aqueous electrolyte 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 derivatives, sulfolane, methylsulfolane, 3-methyl -2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, diethyl ether, 1,3- Ropansaruton, methyl propionate, and a solvent obtained by mixing one or more aprotic organic solvents such as ethyl propionate.
[0048]
Examples of the organic solid electrolyte include a polyethylene derivative, a polyethylene oxide derivative or a polymer containing the same, a polypropylene oxide derivative or a polymer containing the same, a phosphate ester polymer, polyphosphazene, polyaziridine, polyethylene sulfide, polyvinyl alcohol, polyvinylidene fluoride, Examples thereof include a polymer containing an ionic dissociation group such as polyhexafluoropropylene, and a mixture of a polymer containing an ionic dissociation group and the above non-aqueous electrolyte.
[0049]
As the inorganic solid electrolyte, a nitride, halide, oxyacid salt or the like of Li can be used. For example, Li _Three N, LiI, Li _Five NI ₂ , Li _Three N-LiI-LiOH, LiSiO _Four LiSiO _Four -LiI-LiOH, Li ₂ SiS _Three , Li _Four SiO _Four , Li _Four SiO _Four -LiI-LiOH, Li _Three PO _Four -Li ₂ S-SiS ₂ And phosphorus sulfide compounds.
[0050]
As the lithium salt, one that dissolves in the non-aqueous electrolyte is used, for example, LiCl, LiBr, LiI, LiClO. _Four , LiBF _Four , LiB _Ten Cl _Ten , LiPF ₆ , LiCF _Three SO _Three , LiCF _Three CO ₂ , LiAsF ₆ , LiSbF ₆ , LiB _Ten Cl _Ten LiAlCl _Four , CH _Three SO _Three Li, CF _Three SO _Three Li, (CF _Three SO ₂ ) ₂ Examples thereof include salts obtained by mixing one or more of NLi, lithium chloroborane, lower aliphatic lithium carboxylate, lithium tetraphenylborate, imides and the like.
[0051]
Moreover, the compound shown below can be added to a nonaqueous electrolyte for the purpose of improving discharge, a charge characteristic, and a flame retardance. For example, pyridine, triethyl phosphite, 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 compounds with carbonyl group, hexamethylphosphine Examples include hollic triamide and 4-alkylmorpholine, bicyclic tertiary amines, oils, phosphonium salts and tertiary sulfonium salts, phosphazenes, and carbonates. That. In order to make the electrolyte nonflammable, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride can be included in the electrolyte. In addition, carbon dioxide gas can be included in the electrolytic solution in order to make it suitable for high-temperature storage.
[0052]
The lithium secondary battery according to the present invention is a lithium secondary battery excellent in 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 LiCoO ₂ Lithium secondary batteries using LiCoO ₂ It is known that the electrolytic solution decomposes on the surface and a film is formed. As a result, it is said that the cycle characteristics, load characteristics and safety are lowered.
On the other hand, in the lithium cobalt based composite oxide of the present invention, the particle surface of the composite oxide of (1) or the composite oxide of (2) is at least one selected from Mg, Ti, or Zr. By adhering the metal oxide with good adhesion, the surface of the composite oxide crystal is stabilized, the decomposition of the electrolytic solution in contact with it is suppressed, the formation of a surface film is suppressed, and the particle surface of the composite oxide is reduced. Since it is exposed moderately, Li insertion and removal from the surface of the composite oxide crystal is made smoother. For this reason, the lithium secondary battery using the lithium cobalt composite oxide of the present invention as the positive electrode active material is considered to have excellent battery performance, particularly load characteristics, cycle characteristics, and safety.
[0054]
The use of the lithium secondary battery according to the present invention is not particularly limited. And electronic devices such as memory cards and video movies, and consumer electronic devices such as automobiles, electric vehicles, and game machines.
[0055]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.
[0056]
Table 1 shows the physical properties of the raw material metal oxide used in the examples of the present invention.
[Table 1]
Note) MgO; ZrO, manufactured by Ube Materials ₂ ; TiO, manufactured by Daiichi Elemental Chemical Co., Ltd. ₂ ; Showa Titanium Co., ZnO; Shodo Chemical Co., Ltd.
[0057]
<Preparation of lithium cobaltate>
Co _Three O _Four (Average particle size 2 μm) 40 g and Li ₂ CO _Three 19 g (average particle diameter: 7 μm) was weighed, thoroughly mixed in a dry process, and then fired at 1000 ° C. for 5 hours. The fired product is pulverized and classified to obtain LiCoO. ₂ Got. Various physical properties of this product are shown in Table 2.
[Table 2]
[0058]
Examples 1-2 and Comparative Examples 1-2
<First step>
LiCoO prepared above ₂ In addition, the amount of metal oxide sample 1 (MgO) shown in Table 3 was added to 0.2% by weight, and the mixture was mixed thoroughly for 60 seconds using a home mixer. ₂ MgO was adhered to the particle surface.
Further, the BET specific surface area after the first step was measured, and the results are shown in Table 3.
<Second step>
Next, LiCoO on which MgO obtained in the first step is adhered ₂ Were divided into four, and each sample was heat-treated at the temperature shown in Table 3 for 5 hours and classified to obtain various lithium cobalt based composite oxides. In addition, Table 3 shows properties of the obtained lithium cobalt composite oxide.
[Table 3]
[0059]
From the results in Table 3, comparing the BET specific surface areas of the lithium cobalt-based composite oxides of Example 1, Example 2 and Comparative Example 1 after the first step and after the second step, Examples 1 and 2 are the same. BET specific surface area after the second step (m ² / G) is large. From this, it can be seen that MgO adheres to the surface of the composite oxide particles with better adhesion than that of Comparative Example 1. Moreover, what was processed at 900 degreeC of the comparative example 2 has a large decreasing rate of this specific surface area compared with the lithium cobalt type complex oxide of Examples 1-2. This is because MgO is partly LiCoO ₂ This is thought to be due to the solid solution up to the inside of the particles. Moreover, the electron micrograph of the lithium cobalt composite oxide obtained in Example 1 is shown in FIG. 1, and an enlarged view thereof is shown in FIG.
[0060]
Examples 3 to 4 and Comparative Example 3
<First step>
LiCoO prepared above ₂ In addition, the metal oxides shown in Table 4 were mixed thoroughly for 60 seconds using a home mixer so as to be 0.2% by weight. ₂ A metal oxide was adhered to the particle surface.
<Second step>
Next, the composite oxide obtained by attaching the various metal oxides obtained in the first step was heat-treated at the temperature shown in Table 4 for 5 hours and classified to obtain various lithium cobalt composite oxides. . In addition, Table 4 shows properties of the obtained lithium cobalt composite oxide.
[Table 4]
[0061]
Example 5
<Preparation of V-substituted composite oxide>
Co _Three O _Four (Average particle size 2 μm) 40 g and LiCO _Three (Average particle size 7 μm) 19.5 g and V ₂ O _Five 0.05 g (average particle size 8 μm) was weighed and thoroughly mixed in a dry process, followed by baking at 1000 ° C. for 5 hours. The fired product is pulverized and classified to obtain LiCo. _0.999 V _0.001 O ₂ Got. Various physical properties of this product are shown in Table 5.
[Table 5]
<First step>
The V-substituted composite oxide prepared above was sufficiently mixed for 60 seconds with a household mixer so that the metal oxide would be 0.2 wt%, thereby forming a metal oxide on the surface of the V-substituted composite oxide particles. Was attached.
Further, the BET specific surface area after the first step was measured, and the result is shown in Table 10.
<Second step>
Next, the composite oxide to which the metal oxide obtained in the first step was attached was heat-treated at 300 ° C. for 5 hours and classified to obtain a lithium cobalt composite oxide. In addition, Table 10 shows the main physical properties of the obtained lithium cobalt composite oxide.
[0062]
Example 6
<Preparation of Cu-substituted composite oxide>
Co _Three O _Four (Average particle size 2 μm) 40 g and Li ₂ CO _Three (Average particle size 7 μm) 19.5 g and CuCO _Three 0.06 g (average particle size: 7 μm) was weighed, thoroughly mixed in a dry process, and then fired at 1000 ° C. for 5 hours. The fired product is pulverized and classified to obtain LiCo. _0.999 Cu _0.001 O ₂ Got. Various physical properties of this product are shown in Table 6.
[Table 6]
<First step>
The Cu-substituted composite oxide prepared above was sufficiently mixed for 60 seconds with a household mixer so that the metal oxide would be 0.2% by weight. Was attached.
Further, the BET specific surface area after the first step was measured, and the result is shown in Table 10.
<Second step>
Next, the composite oxide to which the metal oxide obtained in the first step was attached was heat-treated at 300 ° C. for 5 hours and classified to obtain a lithium cobalt composite oxide. In addition, Table 10 shows properties of the obtained lithium cobalt composite oxide.
[0063]
Example 7
<Preparation of Fe-substituted composite oxide>
Co _Three O _Four (Average particle size 2 μm) 40 g and Li ₂ CO _Three (Average particle size 7 μm) 19.5 g and Fe _Three O _Four 0.04 g (average particle size 5 μm) was weighed, thoroughly mixed in a dry process, and then fired at 1000 ° C. for 5 hours. The fired product is pulverized and classified to obtain LiCo. _0.999 Fe _0.001 O ₂ Got. Various physical properties of this product are shown in Table 7.
[Table 7]
<First step>
The Fe-substituted composite oxide was prepared by mixing the Fe-substituted composite oxide with the above-described Fe-substituted composite oxide for 60 seconds using a home mixer so that the metal oxide would be 0.2% by weight. Was attached.
Further, the BET specific surface area after the first step was measured, and the result is shown in Table 10.
<Second step>
Next, the composite oxide to which the metal oxide obtained in the first step was attached was heat-treated at 300 ° C. for 5 hours and classified to obtain a lithium cobalt composite oxide. In addition, Table 10 shows properties of the obtained lithium cobalt composite oxide.
[0064]
Example 8
<Preparation of Zn-substituted composite oxide>
Co _Three O _Four (Average particle size 2 μm) 40 g and Li ₂ CO _Three 19.5 g (average particle size: 7 μm) and 0.04 g of ZnO (average particle size: 5 μm) were weighed, thoroughly mixed in a dry process, and calcined at 1000 ° C. for 5 hours. The fired product is pulverized and classified to obtain LiCo. _0.999 Zn _0.001 O ₂ Got. Various physical properties of this product are shown in Table 8.
[Table 8]
<First step>
The Zn-substituted composite oxide prepared above was mixed with the metal oxide on the particle surface of the Zn-substituted composite oxide by thoroughly mixing for 60 seconds using a household mixer so that the metal oxide would be 0.2% by weight. Was attached.
Further, the BET specific surface area after the first step was measured, and the result is shown in Table 10.
<Second step>
Next, the composite oxide to which the metal oxide obtained in the first step was attached was heat-treated at 300 ° C. for 5 hours and classified to obtain a lithium cobalt composite oxide. In addition, Table 10 shows properties of the obtained lithium cobalt composite oxide.
[0065]
Example 9
<Preparation of Zr-substituted composite oxide>
Co _Three O _Four (Average particle size 2 μm) 40 g and Li ₂ CO _Three (Average particle size 7 μm) 19.5 g and ZrO ₂ 0.06 g (average particle size 1 μm) was weighed, thoroughly mixed in a dry process, and then fired at 1000 ° C. for 5 hours. The fired product is pulverized and classified to obtain LiCo. _0.999 Zr _0.001 O ₂ Got. Various physical properties of this product are shown in Table 9.
[Table 9]
<First step>
The Zr-substituted composite oxide prepared above was sufficiently mixed for 60 seconds with a household mixer so that the metal oxide would be 0.2% by weight. Was attached.
Further, the BET specific surface area after the first step was measured, and the result is shown in Table 10.
<Second step>
Next, the composite oxide to which the metal oxide obtained in the first step was attached was heat-treated at 300 ° C. for 5 hours and classified to obtain a lithium cobalt composite oxide. In addition, Table 10 shows the main physical properties of the obtained lithium cobalt composite oxide.
[Table 10]
[0066]
<Battery performance test>
(I) Production of lithium secondary battery;
Lithium cobalt-based composite oxides obtained in Examples 1 to 9 and Comparative Examples 1 to 3 produced as described above and LiCoO used in Example 1 ₂ (Comparative Example 4) 91% by weight, 6% by weight of graphite powder and 3% by weight of polyvinylidene fluoride were mixed to prepare a positive electrode agent, which was dispersed in N-methyl-2-pyrrolidinone to prepare a kneaded paste. The kneaded paste was applied to an aluminum foil, dried, pressed and punched into a disk with a diameter of 15 mm to obtain a positive electrode plate.
Using this positive electrode plate, a lithium secondary battery was manufactured using each member such as a separator, a negative electrode, a positive electrode, a current collector plate, a mounting bracket, an external terminal, and an electrolytic solution. Among these, the negative electrode uses a metal lithium foil, and the electrolyte solution is 1 liter of a 1: 1 kneading solution of ethylene carbonate and methyl ethyl carbonate. ₆ What melt | dissolved 1 mol was used.
[0067]
(1) Battery performance evaluation
The produced lithium secondary battery was operated at room temperature, and the following battery performance was evaluated.
・ Measurement of capacity maintenance rate and energy maintenance rate
The discharge capacity and energy density were measured by charging and discharging to the positive electrode at a constant current voltage (CCCV) of 0.5 C to 4.3 V at room temperature and then discharging to 0.2 V at 0.2 C as one cycle. .
Next, 20 cycles of charge / discharge in the measurement of the discharge capacity and energy density were performed, the capacity maintenance rate was calculated by the following formula (1), and the energy maintenance rate was calculated by the following formula (2). The results are shown in Tables 11 and 12. Moreover, under this condition of the lithium secondary battery using the lithium cobalt 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 are shown in FIGS.
[Expression 1]
[Expression 2]
[0068]
・ Evaluation of load characteristics
First, the positive electrode was charged to 4.3V over 5 hours at 0.5C by constant current voltage (CCCV) charge, and then discharged to 2.7V at discharge rates of 0.2C, 0.5C and 1.0C. Charging / discharging was performed, and these operations were taken as one cycle, and the discharge capacity and energy density were measured for each cycle. This cycle was repeated three times, and the discharge capacity and energy density at the third cycle were determined. The results are shown in Tables 11 and 12. In addition, the above operation was performed for a lithium secondary battery using the lithium cobalt 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 characteristics at 0.2C, 0.5C, and 1C are shown in FIGS. 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 with the same discharge capacity. It shows that it is excellent.
[Table 11]
[Table 12]
From the results of Tables 11 and 12, the lithium secondary battery using the lithium cobalt composite oxide of the present invention as the positive electrode active material has a higher capacity retention rate than that using the comparative example as the positive electrode active material. It can be seen that the load characteristics are excellent. In addition, the figure 3 ~ Figure 14 From these results, it can be seen that a clear shoulder is seen at the end of the discharge curve as compared with the case of using Comparative Example 4 as the positive electrode active material, and the high voltage is maintained until the end of the discharge.
[0069]
・ Evaluation of safety
Soseki, Kita, Wada (November 21-23, 2001, 42nd Battery Symposium, Abstracts, 462-463), Ota, Oiwa, Ishigaki et al. (November 21-23, 2001) 42nd Battery Symposium Abstracts, pages 470-471) and lithium-cobalt composites prepared in Example 2 and Comparative Example 4 based on the battery thermal stability evaluation method disclosed in Japanese Patent Application Laid-Open No. 2002-158008. A lithium secondary battery using an oxide as a positive electrode active material was charged at a constant current voltage (CCCV) charge at a constant current voltage (CCCV) at room temperature to 4.3 V for 5 hours, and then in an argon atmosphere. The lithium secondary battery was disassembled, lithium was extracted, and the positive electrode plate containing the positive electrode active material deintercalated was taken out. Next, 5.0 mg each of the positive electrode active material is scraped from the taken out positive electrode plate, and LiPF is added to 1 liter of a 1: 1 kneaded solution of ethylene carbonate and methyl ethyl carbonate. ₆ A differential scanning calorimeter (SII Eporide Service) is enclosed in a closed cell (SUS cell) for differential scanning calorimetry (DSC) together with 5.0 ml of 1 mol dissolved solution at a heating rate of 2 ° C / min. The change in the differential calorific value was measured with a model DSC6200). The result of the differential calorific value change is shown in FIG. As the amount of heat on the vertical axis in FIG. 15, a value divided by the weight of the measured positive electrode active material was used.
In FIG. 15, the higher the heat generation peak height, the higher the temperature, and the gentler the amount of heat generation from the start of heat generation, the better the thermal stability, that is, the battery safety. Indicates.
From the result of FIG. 15, LiCoO ₂ In Comparative Example 4, the temperature at which the height of the exothermic peak becomes maximum is 196 ° C., whereas in the lithium cobalt composite oxide of the present invention (Example 2), the temperature of the exothermic peak is high. The temperature when the maximum value is 235 ° C., and LiCoO ₂ Compared to that of (Comparative Example 4), the lithium cobalt based composite oxide of the present invention has a gentler calorific value gradient from the heat generation start temperature to the temperature at which the height of the heat generation peak becomes maximum. It turns out that the safety of the battery is excellent.
[0070]
【The invention's effect】
As described above, the lithium cobalt composite oxide of the present invention has the 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, and y is 0 ≦ y. ≦ 0.01, a takes a value of −0.1 ≦ a ≦ 0.1.) At least one metal oxide selected from Mg, Ti, or Zr on the surface of the composite oxide particles represented by Is a lithium-cobalt composite oxide with good adhesion, and when this lithium-cobalt composite oxide is used as a positive electrode active material of a lithium secondary battery, it is particularly excellent in load characteristics, cycle characteristics and safety. It becomes a lithium secondary battery.
[Brief description of the drawings]
1 is an electron micrograph showing the state of the particle surface of a lithium cobalt composite oxide obtained in Example 1. FIG.
2 is an electron micrograph showing the state of the particle surface of the lithium cobalt composite oxide obtained in Example 1. FIG.
3 is a graph showing cycle characteristics of a lithium secondary battery in which the lithium cobalt-based composite oxide obtained in Example 1 is used as a positive electrode active material. FIG.
4 is a graph 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 graph showing cycle characteristics of a lithium secondary battery using the lithium cobalt-based composite oxide obtained in Example 4 as a positive electrode active material. FIG.
6 is a graph 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 graph 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.
FIG. 8 shows LiCoO of Comparative Example 4 ₂ The figure which shows the cycling characteristics of the lithium secondary battery which uses as a positive electrode active material.
9 is a graph showing load characteristics at 0.2 C, 0.5 C, and 1 C of a lithium secondary battery that uses the lithium cobalt composite oxide obtained in Example 1 as a positive electrode active material. FIG.
10 is a graph showing load characteristics at 0.2 C, 0.5 C, and 1 C of a lithium secondary battery using the lithium cobalt based composite oxide obtained in Example 3 as a positive electrode active material. FIG.
11 is a graph showing load characteristics at 0.2 C, 0.5 C, and 1 C of a lithium secondary battery using the lithium cobalt based composite oxide obtained in Example 4 as a positive electrode active material. FIG.
12 is a graph showing load characteristics at 0.2 C, 0.5 C, and 1 C of a lithium secondary battery using the lithium cobalt-based composite oxide obtained in Comparative Example 1 as a positive electrode active material. FIG.
13 is a graph showing load characteristics at 0.2 C, 0.5 C, and 1 C of a lithium secondary battery using the lithium cobalt-based composite oxide obtained in Comparative Example 3 as a positive electrode active material. FIG.
14 shows LiCoO of Comparative Example 4. FIG. ₂ The load characteristic in 0.2C, 0.5C, 1C of the lithium secondary battery which uses as a positive electrode active material.
15 is a graph showing a change in differential calorific value of a positive electrode active material in which lithium is extracted from the lithium cobalt composite oxide obtained in Example 2 and Comparative Example 4 and deintercalated. FIG.

Claims (7)

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 represents 0.9 ≦ x ≦ 1.1, y is 0 ≦ y ≦ 0.01, and a is −0.1 ≦ a ≦ 0.1.), Mg, Ti Or at least one metal oxide selected from Zr is dry-mixed and heat-treated at 200 to 600 ° C. to adhere the metal oxide to the particle surface of the composite oxide. Lithium cobalt complex oxide.  The lithium cobalt-based composite oxide according to claim 1, wherein the metal oxide is attached in an amount of 0.05 to 1% by weight. The lithium cobalt-based composite oxide according to claim 1 or 2, wherein the BET specific surface area is 0.1 to 2.0 m ² / g. The manufacturing method of the lithium cobalt type complex oxide characterized by including the following 1st-2nd processes.
First step; _{formula; Li x Co 1-y Me} y O 2-a (Me represents V, Cu, Zr, Zn, Mg, one or more metal elements selected from Al or Fe X is 0.9 ≦ x ≦ 1.1, y is 0 ≦ y ≦ 0.01 , and a is −0.1 ≦ a ≦ 0.1.) A step of dry-mixing with at least one metal oxide selected from Mg, Ti, or Zr to adhere the metal oxide particles to the surface of the composite oxide particles.
2nd process; The process of obtaining the lithium cobalt type complex oxide by heat-processing at 200-600 degreeC the complex oxide to which the metal oxide obtained by the 1st process was made to adhere.  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.  A lithium secondary battery positive electrode active material comprising the lithium cobalt-based composite oxide according to any one of claims 1 to 3.  A lithium secondary battery comprising the lithium secondary battery positive electrode active material according to claim 6.