JP2002075367A - Positive electrode active material for lithium battery, manufacturing method for the active material, and secondary battery using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode active material for lithium secondary battery having better thermal stability than any conventional positive electrode active material without deteriorating the high initial discharge capacity to any significant degree. SOLUTION: The positive electrode active material for lithium secondary battery is structured so that a surface layer containing besides Li, one or more elements selected from among a group at least including Mo and W is provided on the surface of a powder of lithium composite oxide, capable of occluding and emitting Li ions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a positive electrode active material for a lithium secondary battery, a method for producing the same, and a secondary battery using the same.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for portable devices such as mobile phones, notebook computers, and VTRs with a built-in camera. For these devices, small and lightweight secondary batteries are indispensable. Until now, secondary batteries have been mainly Ni-Cd
Batteries and Ni-hydrogen batteries have been used, but these batteries are at the limit of miniaturization and weight reduction.

On the other hand, lithium ion secondary batteries have been developed. This battery is characterized by a higher voltage and a higher energy density than conventional small secondary batteries, and can be made smaller and lighter than conventional batteries.

As a negative electrode of a lithium secondary battery, a material capable of occluding and releasing lithium metal, a lithium alloy, and lithium ions is used. As a substance capable of inserting and extracting lithium ions, a carbon material or a metal oxide having a layered structure has been proposed.

On the other hand, as an active material constituting the positive electrode, a material capable of absorbing and releasing lithium ions is used.
₂ , metal oxides such as LiNiO ₂ and LiMn ₂ O ₄ , Ti
Metal sulfides such as S _2, are mentioned specific polymer material.

Further, a polymer film such as polypropylene is used as a separator interposed between the positive electrode and the negative electrode. The polymer film is a thin porous film of 50 microns or less from the viewpoint of lithium ion conductivity and energy density.

As an electrolytic solution, a non-aqueous solvent mainly composed of a high dielectric constant solvent such as propylene carbonate is used.
_A solution obtained by dissolving a lithium salt such as ₆ as an electrolyte salt is used.

In order to further increase the capacity and the energy density of the lithium ion secondary battery, it is essential to ensure the safety of the battery. For this purpose, it is important to further enhance the thermal stability of various members of the lithium secondary battery. In addition, as the size of the battery increases, the cooling efficiency of the battery deteriorates, and thus the thermal stability of the battery member is further required.

In the positive electrode active material, the thermal stability in the charged state, that is, the state in which most of the lithium ions are released is regarded as a problem, and it is necessary to suppress the reactivity with the electrolyte in the charged state. is there.

Therefore, various improvements have been made so far. For example, in LiCoO ₂ and LiNiO ₂ , it has been proposed to partially replace Co or Ni with a different element in order to improve not only the thermal stability but also the cycle characteristics of the battery. In particular, LiNiO ₂ is LiCoO ₂
Although it exhibits a higher discharge capacity than O ₂ , thermal stability and cycle characteristics are inferior, so proposals have been made to improve this. For example, JP-A-62-90863, JP-A-62-264560, and JP-A-4-17165.
9, JP-A-5-101827, JP-A-5-101827
No. 2,830,076.

In Japanese Patent Application Laid-Open No. 62-90863, A_x
M_yN_zO_Two(However, A is an alkali metal, M is a transition metal,
N is Al, In or Sn, and 0.05 ≦ x ≦ 1.
1, 0.85 ≤ y ≤ 1, 0.001 ≤ x ≤ 0.1)
The composite oxide to be used is disclosed in JP-A-62-264560.
Then, LiNi_xCo_1-xO_Two(However, 0 <x ≦ 0.2
The composite metal oxide represented by 7) is disclosed in JP-A-4-1716.
No. 59, LiMO _z(However, part of Li is Al
Is replaced by potassium earth metal, M is Co, Fe, Ni
Lithium composite oxidation represented by 1.9 <z <2.1)
The product is disclosed in Japanese Unexamined Patent Publication No._xM_yN
i_1-yO_z(Where M is Mg, V, Cr, Cu, 0
<X <1.3, 0.02 ≦ y ≦ 0.5, 1.8 <z <
The active material represented by 2.2) is disclosed in JP-A-5-283076.
Publication contains Li_yNi_1-xMe_xO_Two(However, Me is T
i, V, Mn, Fe, 0.2 <y ≦ 1.3, Me
Is Ti, V, Fe, 0 <x <0.5, and Me is Mn.
In the case of, an active material represented by 0 <x <0.6) is proposed.
Have been.

However, in order to cope with higher capacity, higher energy density and larger size of the lithium ion secondary battery, there is a problem that the above-mentioned positive electrode active material has insufficient thermal stability. Had.

[Problems to be solved by the invention]

The present invention solves the above-mentioned problems, and an object of the present invention is to reduce the high initial discharge capacity without significantly deteriorating the thermal stability compared with the conventionally proposed positive electrode active material. Is to provide a good positive electrode active material.

[0014]

According to the present invention, a lithium composite oxide powder capable of inserting and extracting Li ions is provided on a surface of at least one selected from the group consisting of Mo and W.
Provided is a positive electrode active material for a lithium secondary battery having a surface layer containing a species element and Li.

The positive electrode active material for a lithium secondary battery according to the present invention, wherein the surface layer is a surface layer including a composite oxide containing at least one element selected from the group consisting of Mo and W and Li and Li. It is an aspect.

The present invention also provides a lithium composite oxide powder capable of occluding and releasing Li ions containing at least one element selected from the group consisting of Co, Ni and Mn and Li, and Mo and W. Provided is a method for producing a positive electrode active material for a lithium secondary battery, wherein a mixture of a composite oxide containing at least one element selected from the group and Li is heat-treated at a temperature of about 650 to about 950 ° C.

Further, the present invention provides a method for preparing a lithium compound, comprising Co, N
A mixture of a compound containing at least one element selected from the group consisting of i and Mn and a composite oxide containing at least one element selected from the group consisting of Mo and W and Li is prepared by mixing about 650 to about 650 Provided is a method for manufacturing a positive electrode active material for a lithium secondary battery, which is heat-treated at a temperature of 950 ° C.

The positive electrode active material for a lithium secondary battery obtained by the above method is a preferable positive electrode active material for a lithium secondary battery of the present invention.

Further, the present invention provides a lithium secondary battery using the above-mentioned positive electrode active material.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The present invention provides a positive electrode active material for a lithium battery, more specifically, a lithium secondary battery such as a lithium ion secondary battery, a method for producing the same, and a secondary battery using the same. The positive electrode active material for a lithium battery of the present invention is Li
Positive electrode active material for a lithium secondary battery having a coating layer containing at least one element selected from the group consisting of Mo and W and Li on the surface of a lithium composite oxide powder capable of occluding and releasing ions. Substance.

As the lithium composite oxide capable of occluding and releasing Li ions according to the present invention, a composite oxide containing lithium and a compound obtained by substituting these with a different element are preferably used. More preferable examples include a lithium composite oxide powder containing at least one element selected from the group consisting of Co, Ni and Mn and Li.

Preferred specific examples of the lithium composite oxide capable of occluding and releasing Li ions according to the present invention include Li
CoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O _{4 and the} like can be mentioned.

Particularly, a lithium composite oxide having a composition represented by the following formula (1) can be mentioned as a preferable compound. Li _x (Ni _1-yz Co _y M _z ) O ₂ (1) (where x, y, and z represent atomic ratios, and 0 <x <1.
1, 0.05 ≦ y ≦ 0.35, 0.01 ≦ z ≦ 0.2
0 and M represent one or more elements selected from the group consisting of Fe, Mn, Al, Ga, and Mg. )

The surface layer formed on the surface of the lithium composite oxide powder capable of inserting and extracting Li ions is made of Mo.
And W and at least one element selected from the group consisting of W and Li. Any layer containing these elements can be used without any particular limitation. However, from the viewpoint of exhibiting the characteristics of the present invention, it is preferable that at least one element selected from the group consisting of Mo and W and Li and It is a surface layer containing a composite oxide consisting of

A surface layer formed on the surface of a lithium composite oxide powder capable of inserting and extracting Li ions;
The amount of the composite oxide containing at least one element selected from the group consisting of Mo and W and Li is such that the metal element other than Li of the lithium composite oxide powder to be coated is selected from the group consisting of M, Mo and W. When at least one element selected is A, the atomic ratio A / M is preferably 0.01 to 3.0 atoms, and more preferably 0.05 to 2.0 atomic%. When the amount is within this range, the reaction with the electrolytic solution can be suppressed and the thermal stability can be improved without significantly deteriorating the electrochemical characteristics such as the discharge capacity.

The method for producing the positive electrode active material for a lithium battery of the present invention may be any method that produces the positive electrode active material having the above characteristics, and a method for achieving the object can be appropriately selected.

For forming a coating layer containing Li and at least one element selected from the group consisting of Mo and W on the surface of the lithium composite oxide powder capable of occluding and releasing Li ions according to the present invention. As a preferred method, Co,
A lithium composite oxide powder capable of inserting and extracting Li ions containing at least one element selected from the group consisting of Ni and Mn and Li, and at least one element selected from the group consisting of Mo and W; A method of heat-treating a mixture with a composite oxide containing Li can be given.

A preferred example of the composite oxide containing at least one element selected from the group consisting of Mo and W and Li is a composite oxide containing at least one element selected from the group consisting of Mo and W and Li. It is an oxide.

The temperature of the heat treatment is preferably from about 650 to about 950.degree. C., more preferably from 700 to 900.degree.

The lithium composite oxide powder, at least one element selected from the group consisting of Mo and W, and L
The mixture with the composite oxide containing i is not particularly limited as long as the lithium composite oxide powder and the composite oxide are substantially present, and the method for preparing the mixture is not particularly limited. The simplest method is to mix the lithium composite oxide powder with the composite oxide prior to heat treatment.

In the mixture, the lithium composite oxide powder and at least one selected from the group consisting of Mo and W
The amount ratio of the complex oxide containing the seed element and Li is determined by setting the metal elements other than Li in the lithium composite oxide powder to M, M
Assuming that at least one element selected from the group consisting of o and W is A, the atomic ratio A / M is 0.01 to 3.0 atomic%, preferably 0.05 to 2.0 atomic%, more preferably Desirably, it is 0.1 to 1.5 atomic%.

Selected from the group consisting of Mo and W
Composite oxide containing at least one element and Li
At least selected from the group consisting of Mo and W
A composite oxide composed of one kind of element and Li is preferable.
Physically Li_TwoMoO_Four, Li _TwoWO_FourAre preferred.

The substance thus obtained is suitable for a positive electrode active material for a lithium secondary battery.

In this way, Mo is deposited on the surface of the lithium composite oxide powder capable of inserting and extracting Li ions.
And a positive electrode active material for a lithium ion secondary battery having a surface layer containing a composite oxide containing at least one element selected from the group consisting of and W and Li.
The amount of the composite oxide forming the surface layer is determined by defining the metal element other than Li in the lithium composite oxide powder as A and at least one element selected from the group consisting of M, Mo, and W as an atomic ratio A / M is 0.01 to 3.0 atomic%, preferably 0.05 to 2.0 atomic%, more preferably 0.1 to 2.0 atomic%.
Preferably, it is 1.5 atomic%.

As another method for producing the positive electrode active material for a lithium battery of the present invention, a Li compound, Co, Ni
And a method of heat-treating a mixture of a compound containing at least one element selected from the group consisting of Mn and Mn and a composite oxide consisting of Li and at least one element selected from the group consisting of Mo and W and Li. Can be mentioned. The temperature of the heat treatment is about 650 to about 950 ° C. as described above.
The temperature is more preferably 700 to 900 ° C.

There is no particular limitation on the preparation of the mixture as described above. The order of mixing the components can be arbitrarily selected, but the components can be mixed and heated at the same time, or Li
After mixing and heating the compound and a compound containing at least one element selected from the group consisting of Co, Ni and Mn, at least one compound selected from the group consisting of Mo and W
It is also possible to mix and heat a composite oxide containing at least one or more elements and Li.

As the Li compound, LiOH, L
iOH.H ₂ O, LiNO ₃ , Li ₂ CO _{3 and the} like are preferably used.

Examples of the compound containing at least one element selected from the group consisting of Co, Ni and Mn include hydroxides, oxyhydroxides, oxides, and nitrates. In addition, this compound is Ti, V,
It may be a solid solution containing elements such as Cr, Fe, Mg, Ca, B, Al, and Ga, or a mixture containing a compound containing these elements.

The Li compound, Co, Ni in the mixture
And the compound oxide containing at least one element selected from the group consisting of Mo and W, and the compound oxide containing at least one element selected from the group consisting of Mo and W and Li, the proportion of Co, The metal element of the compound containing at least one element selected from the group consisting of Ni and Mn is M, and at least one element selected from the group consisting of Mo and W is A, and the atomic ratio is Li: M:
When A = a: 100 atomic%: b, a is 100 to 1
15 atomic%, preferably 100 to 110 atomic%;
b is 0.01 to 3.0 atomic%, preferably 0.05 to
Desirably, it is 2.0 atomic%.

The substance thus obtained is suitable for a positive electrode active material for a lithium ion secondary battery.

The coating layer of the present invention obtained by the above-mentioned method can be observed by X-ray diffraction measurement, but has a very small diffraction peak compared to a lithium composite oxide powder capable of occluding and releasing Li ions. It is.

The electrode for a lithium secondary battery containing the positive electrode active material of the present invention or the lithium secondary battery using the positive electrode active material is a preferred embodiment of the present invention.

As an example of a lithium secondary battery using the above-mentioned positive electrode active material, a lithium secondary battery basically includes a negative electrode, a positive electrode, and a non-aqueous electrolyte. Is provided with a separator.

As the positive electrode active material constituting the positive electrode, the above-mentioned positive electrode active material is suitably used. Further, as the positive electrode active material, in addition to the positive electrode active material, other composite oxides of lithium and a transition metal can be used as a mixture.

The negative electrode active material constituting the negative electrode includes metallic lithium, a lithium alloy, a carbon material capable of doping and undoping lithium ions, tin oxide capable of doping and undoping lithium ions, and oxides of lithium and lithium. Any of niobium, vanadium oxide, titanium oxide capable of doping and undoping lithium ions, and silicon capable of doping and undoping lithium ions can be used. Among these, a carbon material capable of doving / de-doping lithium ions is preferable. Such a carbon material may be graphite or amorphous carbon, and activated carbon, carbon fiber, carbon black, mesocarbon microbeads, natural graphite and the like are used.

The negative electrode active material was measured by X-ray analysis from the viewpoint of increasing the energy density of the battery (0
02) A carbon material having a plane spacing (d002) of 0.340 nm or less is preferable, and graphite having a density of 1.70 g / cm ³ or more or a highly crystalline carbon material having properties close thereto is recommended. .

As the non-aqueous electrolyte, LiBF ₄ , LiPF ₆ , LiClO 2 are usually added to a non-aqueous solvent such as propylene carbonate or a carbonate compound containing ethylene carbonate.
₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LI ₂ SiF ₆ , LiC ₈ F
A solution in which an electrolyte such as ₁₇ SO ₃ is mixed is used. As the non-aqueous solvent, a mixture of various non-aqueous solvents and a compound containing an additive have been proposed, but any of the conventionally proposed non-aqueous solvents can be appropriately selected and used.

As the electrolyte, the above-mentioned LiBF ₄ ,
LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , Li
_{In addition to 2} SiF ₆ and LiC ₈ F ₁₇ SO ₃ , lithium salts represented by the following general formula can also be used. LiOSO
₂ R ⁸ , LiN (SO ₂ R ⁹ ) (SO ₂ R ¹⁰ ), LiC (SO ₂ R
R ¹¹ ) (SO ₂ R ¹² ) (SO ₂ R ¹³ ), LiN (SO ₂ OR
¹⁴ ) (SO ₂ OR ¹⁵ ) (where R ^{8 to} R ¹⁵ may be the same or different and are perfluoroalkyl groups having 1 to 6 carbon atoms). These lithium salts can be used alone or in combination of two or more.

The separator is a film that electrically insulates the positive electrode and the negative electrode and allows lithium ions to pass therethrough, and examples thereof include a porous film and a polymer electrolyte. A microporous polymer film is suitably used as the porous film, and examples of the material include polyolefin, polyimide, and polyvinylidene fluoride. In particular, a porous polyolefin film is preferable, and specific examples thereof include a porous polyethylene film, a porous polypropylene film, and a multilayer film of a porous polyethylene film and polypropylene. Examples of the polymer electrolyte include a polymer in which a lithium salt is dissolved, a polymer swelled with an electrolytic solution, and the like. The electrolyte of the present invention may be used for the purpose of obtaining a polymer electrolyte by swelling a polymer.

Such a lithium secondary battery has a cylindrical shape,
It can be formed in a coin shape, a square shape, or any other shape. However, the basic structure of the battery is the same regardless of the shape, and the design can be changed according to the purpose. next,
The structure of the cylindrical and coin type batteries will be described.
As the negative electrode active material, the positive electrode active material, and the separator constituting each battery, those described above are commonly used.

For example, in the case of a cylindrical lithium secondary battery, a negative electrode obtained by applying a negative electrode active material to a negative electrode current collector and a positive electrode obtained by applying a positive electrode active material to a positive electrode current collector are connected to each other. It is wound through a separator into which an aqueous electrolyte has been injected, and is housed in a battery can in a state where insulating plates are placed above and below the wound body.

The secondary battery according to the present invention can be applied to a coin-type lithium secondary battery. In a coin-type battery, a disc-shaped negative electrode, a separator, a disc-shaped positive electrode, and a stainless steel or aluminum plate are housed in a coin-shaped battery can in a state of being stacked in this order.

[0053]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention.

Example 1 Lithium hydroxide, Ni, C
o Co-containing β-type nickel hydroxide and aluminum hydroxide having an atomic ratio of 80:20 were mixed with an atomic ratio of Li: (Ni + C
o): Al = 1.03: 0.9: 0.1,
Mix well in an agate mortar in nitrogen. This powder was placed in a tubular furnace at 780 ° C. in an oxygen stream at a flow rate of 0.5 l / min.
For 8 hours. After being allowed to cool and taken out into a glove box in an N ₂ atmosphere, the mixture was pulverized in a mortar to obtain a lithium composite oxide powder. X of the above lithium composite oxide powder
X-ray diffraction measurement was performed, and as a result of qualitative analysis of the X-ray diffraction pattern, the crystal structure was a layered rock salt type belonging to the space group R-3m.

The above-mentioned lithium composite oxide and 1.0 mol% of Li ₂ MoO ₄ powder were mixed with the lithium composite oxide, and mixed at 714 ° C. in an oxygen stream at a flow rate of 0.5 l / min.
Heat treatment was performed for a time to perform a coating treatment with a compound containing Li and Mo.

A battery charge / discharge test using the above-mentioned coated lithium composite oxide was carried out as follows. First, the obtained powder, acetylene black, and a Teflon (registered trademark) binder were mixed at a weight ratio of 67:22:11, and 24 mg of the mixed powder was sampled and placed on a 10 mmφ SUS304 mesh (100 mesh). 5t /
After pressure bonding at cm ² , vacuum drying at 140 ° C. was used as a positive electrode.

For the negative electrode, metal Li foil and for the separator, P
Using a mixed solution of ethylene carbonate and diethyl carbonate (volume ratio 1: 1) in which lmo1 / l of LiPF ₆ was dissolved as an E porous film and an electrolyte, a coin battery was produced in a glove box in an argon atmosphere. . This battery was supplied to the positive electrode active material at a constant current of 20 mA / g at 4.3 V.
And discharged to 3.0 V at a constant current of 20 mA / g. The first discharge capacity was determined from the measurement data.

Further, a thermal stability test was conducted as follows. A battery was prepared in the same manner as in the charge / discharge test, and the positive electrode active material was charged at a constant current of 20 mA / g to 4.3 V, and then charged at a constant voltage. The charged battery is disassembled in an argon atmosphere, and after taking out the positive electrode plate, 1.5 mg of an electrode containing an electrolyte solution, a positive electrode active material, etc. is collected, sealed in a 15 μl SUS sealed container and subjected to thermal analysis. Sample.

The thermal analysis was carried out by using a DSC device (D
SC220), and the temperature was raised at a rate of 5 ° C./min. age,
250 ml / min. The measurement was performed by flowing Ar gas at a flow rate of. The measured data was subjected to a process of subtracting the data obtained by measuring the empty container under the same measurement conditions as a background, and the temperature showing the largest heat generation was determined as the heat generation peak temperature.

Example 2 A lithium composite oxide powder coated in the same manner as in Example 1 except that Li ₂ MoO ₄ was changed to Li ₂ WO ₄ and the heat treatment temperature was changed to 752 ° C., was synthesized.
A charge / discharge test and a thermal stability test were performed.

Example 3 Lithium hydroxide, Ni and Co
Of Co-containing β-type nickel hydroxide, aluminum hydroxide and Li ₂ MoO ₄ having an atomic ratio of 80:20, respectively: Li: (Ni + Co): Al: Mo = 1.0
The mixture was thoroughly mixed in an agate mortar in nitrogen so as to be 3: 0.9: 0.1: 0.01. This powder was heat-treated in a tubular furnace at 780 ° C. for 8 hours in an oxygen stream at a flow rate of 0.5 l / min. After leaving to be cooled and taken out into a glove box in an N ₂ atmosphere, it was pulverized with a mortar to obtain a lithium composite oxide powder coated with a compound containing Li and Mo.

The above-mentioned lithium composite oxide powder was subjected to X-ray diffraction measurement. As a result of qualitative analysis of the X-ray diffraction pattern, the crystal structure was presumed to be Li ₄ MoO ₅ although the main phase was a layered rock salt type belonging to the space group R-3m, which was a very small and broad X-ray diffraction peak. Phase was detected.

The coated lithium composite oxide powder was subjected to a charge / discharge test and a thermal stability test in the same manner as in Example 1.

Comparative Example 1 A lithium composite oxide powder was synthesized in the same manner as in Example 1 except that the coating treatment was omitted, and a charge / discharge test and a thermal stability test were performed.

Table 1 summarizes the results of X-ray diffraction measurement of the positive electrode active materials prepared in Examples 1 to 3 and Comparative Example 1. As a result of the qualitative analysis, each of the main phases was a layered rock salt type belonging to the space group R-3m. Qualitative analysis of the X-ray diffraction pattern of the compound phase associated with the overlying layer indicated putative compounds that seemed valid. With the coating treatment, the presence of the Li ₄ MoO ₅ phase in Examples 1 and 3 and the presence of Li ₄ Mo in Example 2
The presence of ₄ WO ₅ was suggested. The lattice constant of the lithium composite oxide having the layered rock salt type structure did not show any significant change in Examples 1 to 3 and Comparative Example 1.

From the qualitative analysis of the X-ray diffraction peaks, it is estimated that the coating layer of the present invention is mainly composed of Li ₄ AO ₅ (A represents Mo or W) or a compound similar thereto.

[0067]

[Table 1]

Table 2 summarizes the results of the charge / discharge test and the thermal stability test of the positive electrode active materials prepared in Examples 1 to 3 and Comparative Example 1. From Table 2, the discharge capacity of the coated positive electrode active material is almost the same as that of the untreated product, but the heat generation peak temperature in the case of the coating treatment is higher than that of the untreated product, and the thermal capacity in the charged state is higher. It can be seen that the stability has been improved.

[0069]

[Table 2]

[0070]

According to the present invention, it is possible to obtain a positive electrode active material having improved thermal stability in a charged state as compared with a conventional positive electrode active material while maintaining a high initial discharge capacity,
A high energy density lithium secondary battery with improved safety can be obtained.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G048 AA04 AB01 AB04 AC06 AD03 AD06 AE05 5H029 AJ04 AK03 AL06 AM03 AM05 AM07 DJ12 DJ16 HJ14 5H050 AA05 AA09 BA17 CA08 FA12 FA18 GA02 HA14

Claims (7)

[Claims] 1. A lithium secondary battery having a surface layer containing at least one element selected from the group consisting of Mo and W and Li on a surface of a lithium composite oxide powder capable of inserting and extracting Li ions. For positive electrode active material. 2. The positive electrode for a lithium secondary battery according to claim 1, wherein the surface layer is a surface layer containing a composite oxide containing at least one element selected from the group consisting of Mo and W and Li. Active material. 3. The lithium composite oxide capable of occluding and releasing Li ions is a lithium composite oxide containing at least one element selected from the group consisting of Co, Ni and Mn and Li. The positive electrode active material for a lithium secondary battery according to claim 1, wherein: 4. A lithium composite oxide powder capable of inserting and extracting Li ions containing at least one element selected from the group consisting of Co, Ni and Mn and Li;
a mixture of at least one element selected from the group consisting of o and W and a composite oxide containing Li,
A method for producing a positive electrode active material for a lithium secondary battery, comprising performing heat treatment at a temperature of about 950 ° C. 5. A Li compound, a compound containing at least one element selected from the group consisting of Co, Ni and Mn, and at least one compound selected from the group consisting of Mo and W.
The mixture of the complex oxide containing the seed element and Li is mixed with about 6
A method for producing a positive electrode active material for a lithium secondary battery, comprising performing heat treatment at a temperature of 50 to about 950C. 6. A positive electrode active material for a lithium secondary battery obtained by the method according to claim 4. 7. A lithium secondary battery using the positive electrode active material according to claim 1.