KR101761454B1 - Lithium cobalt oxide, process for producing same, positive active material for lithium secondary battery, and lithium secondary battery - Google Patents

Abstract

An object of the present invention is to provide lithium cobalt oxide capable of increasing the capacity retention rate and increasing the capacity of a lithium secondary battery. The present invention is a lithium cobaltate characterized by having an average particle size of 15 to 35 탆, a Li / Co molar ratio of 0.900 to 1.040, and an amount of residual alkali of 0.05 mass% or less.

Description

FIELD OF THE INVENTION The present invention relates to lithium cobalt oxide, a lithium cobalt oxide, a lithium cobalt oxide, a lithium cobalt oxide, a lithium cobalt oxide, a lithium cobalt oxide, a lithium cobalt oxide, a lithium cobalt oxide,

The present invention relates to lithium cobalt oxide, particularly lithium cobalt oxide useful as a positive electrode active material for a lithium secondary battery, a production method thereof, a positive electrode active material for a lithium secondary battery and a lithium secondary battery using the same.

Description of the Related Art [0002] Recently, with the progress of portable and cordless devices in home electric appliances, lithium ion secondary batteries have been put to practical use as power sources for small electronic devices such as laptop-type personal computers, mobile phones, video cameras and the like. Since lithium cobalt oxide (LiCoO ₂ ) has been reported to be useful as a positive electrode active material for a lithium ion secondary battery, the lithium transition metal composite oxide has been actively developed and developed. Many suggestions were made.

Examples of the lithium transition metal composite oxide include lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), lithium manganese oxide (LiMn ₂ O ₄ ) Etc. are preferably used. In particular, LiCoO ₂ is widely used in terms of safety, charge / discharge capacity, and the like.

In recent years, there has been a need for a lithium cobalt oxide complex oxide for a lithium secondary battery capable of high capacity from the demand for high capacity of a lithium secondary battery.

As a method for increasing the capacity of the lithium secondary battery, there are (1) a method of increasing the capacity per volume by increasing the charging rate of the positive electrode active material by mixing the lithium cobalt oxide of the substituent with the lithium cobalt oxide of the small particle (for example, Patent Document _{1), (2) LiNi 0} .85 _{0 .15} O _2, such as Co, by changing the composition of LiCoO _2, example of how to achieve a higher capacity by increasing the weight per dose (for example, Patent Document 2) has been conventionally performed.

Japanese Patent Application Laid-Open No. 2004-182564 (claims) Japanese Patent Application Laid-Open No. 11-060243 (claims)

However, in the above method (1), there is a problem that the small particles cause generation of gas due to reaction with the non-aqueous electrolyte which occurs when the safety of the battery is repeated, in particular, charging and discharging are repeated, and that the cycle deterioration And the capacity retention rate is low. The non-aqueous electrolyte takes place when the method of the above (2), since the lithium compound remains as a residual alkali used in the manufacture of _{LiNi 0 .85 Co 0 .15 O 2} , repeat the safety, in particular, the charge and discharge of the battery There is a problem in that the generation of gas due to the reaction with the gas is increased.

Accordingly, an object of the present invention is to provide lithium cobalt oxide capable of increasing the capacity of the lithium secondary battery and increasing the capacity retention rate.

As a result of intensive studies in view of the above circumstances, the present inventors have found that (1) when cobalt hydroxide or cobalt oxide having a specific average particle size and a specific compressive strength is used as a raw material for producing lithium cobalt oxide and reacted with a lithium compound , Even when the amount of the lithium compound used is not excessively excessive with respect to the cobalt compound, specifically, in a molar ratio of 0.900 to 1.040 with respect to the cobalt compound in terms of atomic ratio, lithium cobalt oxide having an average particle diameter of 15 to 35 μm And (2) the lithium cobalt oxide having an average particle diameter of 15 to 35 탆, a Li / Co molar ratio of 0.900 to 1.040, and a residual alkali-reduced cobalt It has been found out that lithium oxide can increase the capacity retention ratio of the lithium secondary battery and can increase the capacity, Having reached.

That is, the present invention (1) is to provide lithium cobalt oxide characterized in that the average particle diameter is 15 to 35 μm, the Li / Co molar ratio is 0.900 to 1.040, and the amount of remaining alkali is 0.05% by mass or less .

In the present invention (2), cobalt hydroxide or cobalt oxide having a secondary particle average particle diameter of 15 to 40 占 퐉 and a compressive strength of 5 to 50 MPa and a lithium compound are mixed so that the molar ratio Li / 1.040 to obtain a raw material mixture of cobalt hydroxide or cobalt oxide and a lithium compound,

And a reaction step of reacting the raw material mixture with cobalt hydroxide or cobalt oxide and a lithium compound by heating at 800 to 1150 占 폚 to obtain lithium cobalt oxide.

The present invention (3) is to provide a positive electrode active material for a lithium secondary battery, wherein the content of lithium cobalt oxide in the present invention (1) is 95.0 to 100.0% by mass.

In addition, the present invention (4) is to provide a lithium secondary battery characterized by using lithium cobalt oxide of the present invention (1) as a positive electrode active material of a lithium secondary battery.

According to the present invention, lithium cobalt oxide capable of increasing the capacity of the lithium secondary battery and increasing the capacity retention rate can be provided.

1 is a particle size distribution diagram of the cobalt hydroxide particles (secondary particle (a)) obtained by Synthesis Example 1. Fig.
2 is a particle size distribution diagram of cobalt hydroxide particles (secondary particles (b)) obtained by pulverizing cobalt hydroxide particles (secondary particles (a)) obtained in Synthesis Example 1. Fig.
3 is a particle size distribution diagram of the cobalt hydroxide particles (secondary particle (a)) obtained in Synthesis Example 5. Fig.
4 is a particle size distribution diagram of cobalt hydroxide particles (secondary particles (b)) obtained by pulverizing cobalt hydroxide particles (secondary particles (a)) obtained in Synthesis Example 5.
5 is a particle size distribution diagram of the cobalt hydroxide particles (secondary particle (a)) obtained in Synthesis Example 7. Fig.
6 is a particle size distribution diagram of cobalt hydroxide particles (secondary particles (b)) obtained by pulverizing cobalt hydroxide particles (secondary particles (a)) obtained in Synthesis Example 7. Fig.
7 is a particle size distribution diagram of the cobalt hydroxide particles (secondary particle (a)) obtained by Synthesis Example 8.
8 is a particle size distribution diagram of cobalt hydroxide particles (secondary particles (b)) obtained by pulverizing cobalt hydroxide particles (secondary particles (a)) obtained in Synthesis Example 8.
9 is a particle size distribution diagram of the cobalt hydroxide particles (secondary particle (a)) obtained in Synthesis Example 9. Fig.
10 is a particle size distribution diagram of cobalt hydroxide particles (secondary particles (b)) obtained by pulverizing cobalt hydroxide particles (secondary particles (a)) obtained in Synthesis Example 9.
11 is an SEM photograph (3000 times) of the cobalt hydroxide particles obtained by Synthesis Example 1;
12 is an SEM photograph (10,000 times) of the cobalt hydroxide particles obtained by Synthesis Example 1. Fig.
13 is an SEM photograph (3000 times) of the cobalt hydroxide particles obtained in Synthesis Example 5;
14 is an SEM photograph (10,000 times) of the cobalt hydroxide particles obtained in Synthesis Example 5;
15 is an SEM photograph (3000 times) of the cobalt hydroxide particles obtained in Synthesis Example 7;
16 is an SEM photograph (10,000 times) of the cobalt hydroxide particles obtained in Synthesis Example 7;
17 is an SEM photograph (3000 times) of the cobalt hydroxide particles obtained by Synthesis Example 8;
18 is an SEM photograph (10,000 times) of the cobalt hydroxide particles obtained by Synthesis Example 8;
19 is an SEM photograph (3000 times) of the cobalt hydroxide particles obtained in Synthesis Example 9;
20 is an SEM photograph (10,000 times) of the cobalt hydroxide particles obtained by Synthesis Example 9;
21 is an SEM photograph (3000 times) of lithium cobalt oxide obtained in Example 6. Fig.
22 is a graph showing the amounts of Mg atoms and Ti atoms in the depth direction of lithium cobalt oxide containing Mg atoms and Ti atoms obtained in Example 5. FIG.
23 is a schematic perspective view of primary particles constituting secondary particles of cobalt hydroxide.
24 is a diagram for explaining the long diameter and the short diameter of the primary particles of cobalt hydroxide.
25 is a diagram for explaining the long diameter and the short diameter of primary particles of cobalt hydroxide.

Hereinafter, the present invention will be described based on its preferred embodiments.

The lithium cobaltate of the present invention is lithium cobaltate having an average particle size of 15 to 35 μm, a Li / Co molar ratio of 0.900 to 1.040, and an amount of residual alkali of 0.05% by mass or less.

The lithium cobaltate of the present invention is represented by the following formula (1):

Li _x CoO ₂ (One)

Or lithium cobaltate represented by the above general formula (1) containing metal atoms (M).

In the general formula (1), the value of x, that is, the Li / Co molar ratio (molar ratio in terms of atom) is 0.900 to 1.040, preferably 0.950 to 1.030, and particularly preferably 0.980 to 1.020. When the Li / Co molar ratio is in the above range, the capacity retention rate is increased. On the other hand, if the Li / Co molar ratio is less than the above range, the discharge capacity per weight is liable to be low because lithium is insufficient. If the Li / Co molar ratio is out of the above range, the capacity retention rate is lowered.

When the lithium cobaltate of the present invention contains metal atoms (M), the metal atoms (M) contained in lithium cobalt oxide are preferably transition metal atoms other than Co or one or more metals One or two selected from Mg, Al, Si, Ca, Ti, V, Cr, Mn, Fe, Ni, Zn, Ga, Sr, Zr, Nb, Mo, Or more. Of these metal atoms (M), Mg and Ti are preferable from the viewpoint of improving the battery performance such as the capacity retention rate and the average operating voltage of the lithium secondary battery. Particularly, it is preferable that the metal atom (M) is a combination of at least Mg and Ti, that is, lithium cobalt oxide contains both metal atoms of Mg and Ti in terms of the capacity retention rate and average operating voltage of the lithium secondary battery The effect of improving the battery performance is further enhanced.

In the lithium cobaltate of the present invention, in the case of lithium cobalt oxide containing metal atoms (M), the content of the metal atoms (M) is preferably 0.10 to 10 parts by weight, based on the lithium cobalt oxide containing the metal atoms (M) 1.5% by mass, particularly preferably 0.20% to 0.80% by mass. When the content of the metal atom (M) is within the above range, it is possible to suppress the reduction of the discharge capacity per weight and improve the battery performance such as the capacity retention rate and the average operating voltage. When M is a combination of two or more kinds of metal atoms, the content of the metal atom (M) is calculated based on the total mole of M atoms.

When the lithium cobaltate of the present invention contains both metal atoms of Mg and Ti, the molar ratio of Ti / Mg (molar ratio in terms of atom) is preferably 0.1 to 4.0, particularly preferably 0.2 to 2.0 . When the molar ratio of Ti / Mg is in the above range, the effect of improving battery performance such as capacity retention rate and average operating voltage by containing Mg atoms and Ti atoms is more preferable.

When the lithium cobaltate of the present invention contains both metal atoms of Mg and Ti, Al, Si, Ca, V, Cr, Mn, Fe, Ni, At least one metal atom selected from Zn, Ga, Sr, Zr, Nb, Mo, W and Bi, preferably at least one metal atom selected from Sr, Zr and Al, .

In the lithium cobaltate of the present invention, in the case of lithium cobalt oxide containing the metal atom (M), the metal atom (M) may be dissolved in the lithium cobalt oxide and exist in the particle, or the lithium cobaltate May be present in the form of an oxide, a sulfate, or a lithium oxide (for example, a complex oxide of lithium and M) on the surface of the particles (primary particles or secondary particles).

The lithium cobalt oxide of the present invention may contain a halogen such as fluorine derived from the raw material in the particles of the lithium cobalt oxide and / or the particle surface in the method for producing lithium cobalt oxide of the present invention .

The lithium cobalt oxide of the present invention contains substantially no residual alkali such as, for example, lithium carbonate, lithium hydroxide and the like. That is, the amount (residual alkali amount) of the alkali remaining in lithium cobalt oxide of the present invention is 0.05 mass% or less.

Generally, lithium cobalt oxide having a large particle diameter is obtained by excessively mixing a lithium compound with a cobalt compound in an amount of 1.045 or more in terms of molar ratio (molar ratio of atomic conversion) of Li / Co and firing a uniformly mixed mixture. For this reason, excess lithium relative to cobalt inevitably remains in excess of 0.05% by weight in lithium cobalt oxide as an alkali.

On the other hand, the lithium cobaltate of the present invention has a large secondary particle diameter, a specific compressive strength, a high secondary particle particle strength (hereinafter also referred to as " cohesive strength is strong " A cobalt compound having excellent reactivity, and lithium cobalt oxide used for a raw material. Therefore, lithium cobalt oxide having an average particle diameter of 15 to 35 탆 and a large particle diameter can be obtained even when lithium and cobalt are reacted in the vicinity of a stoichiometric ratio. Therefore, the amount of alkali remaining in lithium cobalt oxide of the present invention is 0.05% Preferably 0.03 mass% or less. That is, the lithium cobalt oxide of the present invention is substantially free of alkali, suppressing the generation of a gas derived from an alkali, and improving the high-temperature storage characteristics of a lithium secondary battery using lithium cobalt oxide as a positive electrode active material have. In the present invention, the measurement of the amount of alkali remaining in lithium cobalt oxide is an acid titration method, and the details of the measurement method will be described later.

The lithium cobalt oxide of the present invention varies depending on the calcination temperature, but in many cases, it exists in the form of monodispersed primary particles. The average particle diameter of the lithium cobalt oxide of the present invention is 15 to 35 mu m, preferably 18 to 35 mu m, particularly preferably 18 to 30 mu m. When the average particle diameter of lithium cobalt oxide falls within the above range, the capacity per volume of the lithium secondary battery is increased and the capacity retention ratio is increased. On the other hand, when the average particle diameter of lithium cobalt oxide is less than the above range, the capacity per volume is lowered. When the average particle diameter exceeds the above range, the capacity retention rate is lowered. In the present invention, the average particle diameter of lithium cobalt oxide is a value measured by a laser diffraction / scattering method, and is a value measured by Microtrack MT3300EXII manufactured by Nikkiso Corporation.

The tap density of the lithium cobalt oxide of the present invention is preferably 2.4 g / ml or more, particularly preferably 2.6 to 3.2 g / ml. When the tap density of lithium cobalt oxide is within the above range, high charging becomes possible, so that the capacity per volume of the lithium secondary battery is increased.

The lithium cobaltate of the present invention is preferably produced by the process for producing lithium cobalt oxide of the present invention described below.

The method for producing lithium cobalt oxide according to the present invention is a method for producing cobalt hydroxide or lithium cobalt oxide having secondary particles having an average particle diameter of 15 to 40 mu m and a compressive strength of 5 to 50 MPa and a lithium compound in a molar ratio Li / 0.900 to 1.040 to obtain a raw material mixture of cobalt hydroxide or cobalt oxide and a lithium compound,

And heating the raw material mixture at 800 to 1150 占 폚 to react lithium cobalt hydroxide or cobalt oxide with a lithium compound to obtain lithium cobalt oxide.

The raw material mixing step is a step of mixing a cobalt hydroxide or cobalt oxide with a lithium compound to obtain a raw material mixture.

The average particle diameter of the secondary particles of the cobalt hydroxide and the average particle diameter of the secondary particles of the cobalt oxide in relation to the raw material mixing step are preferably 15 to 40 mu m, particularly preferably 18 to 35 mu m. Since the average particle diameter of the secondary particles of cobalt hydroxide or cobalt oxide is within the above range, the average particle diameter of lithium cobalt oxide obtained by reacting cobalt hydroxide or cobalt oxide with a lithium compound can be 15 to 35 mu m, The capacity per volume of the secondary battery is increased. Cobalt hydroxide and cobalt oxide are agglomerates formed by aggregation of primary particles, that is, secondary particles. In the present invention, the average particle size of the secondary particles of the cobalt hydroxide and the average particle size of the secondary particles of the cobalt oxide are values measured by laser diffraction scattering method and are values measured by Microtrack MT3300EXII manufactured by Nikkiso Co., Ltd. .

The compressive strength of the secondary particles of the cobalt hydroxide and the compressive strength of the secondary particles of the cobalt oxide in relation to the raw material mixing step are 5 to 50 MPa and preferably 8 to 30 MPa. Since the compressive strength of the secondary particles of cobalt hydroxide or cobalt oxide is in the above range, the secondary particles of cobalt hydroxide or cobalt oxide dissociate when they are mixed before the cobalt hydroxide or the cobalt oxide and the lithium compound are reacted , Secondary particles having a small particle diameter can be prevented from being formed. Thus, lithium cobalt oxide having an average particle diameter of 15 to 35 mu m can be obtained. The cobalt hydroxide and the cobalt oxide in which the compressive strength of the secondary particle is in the above range fall within the range of the particle size distribution of the secondary particles before and after the pulverizing treatment even if the pulverization treatment is carried out with a shear force as high as that of a domestic coffee mill, The average particle diameter of the secondary particles is not more than 7.0 占 퐉. Therefore, in the production of lithium cobalt oxide, since secondary particles of cobalt hydroxide or cobalt oxide are not well dissociated when cobalt hydroxide or cobalt oxide and a lithium compound are mixed, lithium cobalt oxide having a large average particle size can be obtained have. In the present invention, the compressive strength of the secondary particles is a value measured by a Shimadzu compact compression tester MTC-W.

In the process for producing lithium cobalt oxide according to the present invention, the average particle diameter and the compressive strength of the secondary particles of cobalt hydroxide or cobalt oxide are both in the above-mentioned range, whereby lithium cobalt oxide having an average particle diameter of 15 to 35 μm is obtained The capacity of the lithium secondary battery can be increased.

The cobalt hydroxide and the cobalt oxide involved in the raw material mixing process are less likely to change in the particle size distribution of the secondary particles before and after the pulverizing treatment even if the pulverization treatment is carried out with a shearing force of about the level of a domestic coffee mill, And the decrease in the average particle diameter is 7.0 占 퐉 or less.

The cobalt hydroxide and the cobalt oxide associated with the raw material mixing step have the aforementioned various physical properties (average particle diameter and compressive strength of the secondary particles), the primary particles are aggregated secondary particles, and the secondary particles It is preferable that primary particles have a primary particle of a plate-like shape, a columnar shape or a needle shape having a long diameter of 1.5 탆 or more in the image analysis of the SEM image and have a tap density of 0.8 g / ml or more Do. Hereinafter, cobalt hydroxide having such a characteristic is also referred to as "cobalt hydroxide (1)", and cobalt oxide is also referred to as "cobalt oxide (1)".

Particle characteristics such as particle shape and surface state of cobalt hydroxide (1) and cobalt oxide (1) are observed by a scanning electron microscope (SEM). Then, image analysis is carried out on the SEM image of the secondary particles of the cobalt hydroxide (1) or the cobalt oxide (1), and when the secondary particles are projected in two dimensions, Find the length. The length of the long diameter and the length of the short diameter of the primary particles will be described with reference to FIG. 23 (A) is a schematic perspective view of a primary particle in a plate form constituting secondary particles, and 23 (B) is a schematic perspective view of secondary particles constituting secondary particles. Fig. 23 is a schematic perspective view of primary particles constituting secondary particles, 23 (C) is a schematic perspective view of a needle-shaped primary particle constituting secondary particles. FIG. 23 (A) is a schematic perspective view of primary particles of each column constituting the secondary particles.

The primary particles on the plate shown in Fig. 23 (A) have a surface 1a on the surface side of the secondary particle and a surface 2a that crosses the surface 1a on the surface side. The surface 1a on the surface side of the secondary particle is represented by an SEM image of the secondary particle on the whole surface while the surface 2a intersecting the surface 1a on the surface side is a surface Since it is present inside the secondary particle, only a part of the surface appears as an SEM image of the secondary particle. In the present invention, the length of the major axis of the primary particles is the diameter (x) of the surface of the primary particles on the surface side of the secondary particles among the surfaces of the primary particles represented by the SEM image. In the present invention, the length of the minor axis of the primary particle is the diameter (y) of the short side of the surface 1a on the surface side of the secondary particle among the surfaces of the primary particles represented by the SEM image.

In the SEM image 24 (A) of the surface of the secondary particles in which the primary particles are aggregated on the plate shown in Fig. 24, the portion surrounded by the frame is the outline of the surface 1a on the surface side of the secondary particles, ) Represents only the portion surrounded by the frame. The length denoted by symbol x in FIG. 24 (B) is the length of the long diameter of the primary particles, and the length denoted by symbol y is the length of the short diameter of the primary particles. In the SEM image 25 (A) of the surface of the secondary particles in which the primary particles of the plate form shown in FIG. 25 are aggregated, the portion surrounded by the frame is the outline of the surface 1a on the surface side of the secondary particles, (B) shows only the portion surrounded by the frame. The length denoted by symbol x in Fig. 25 (B) is the length of the long diameter of the primary particles, and the length denoted by symbol y is the length of the short diameter of the primary particles.

The shape of the primary particles on the plate shown in Fig. 23 (A) is not limited to this, and the shape in the plane direction is not limited as long as it has a spread in the plane direction, and it may be curved.

The primary primary particles shown in Fig. 23 (B) include a surface 1b on the surface side of the secondary particle and a surface 2b intersecting the surface 1b on the surface side. The surface 1b on the surface side of the secondary particle is represented by the SEM image of the secondary particle as a whole but the surface 2b intersecting the surface 1b on the surface side is the surface most of the surface 2b Since it is present inside the secondary particle, only a part of the surface appears as an SEM image of the secondary particle. In the present invention, the length of the major axis of the primary particles is the diameter (x) of the longer side of the surface 1b on the surface side of the secondary particles among the surfaces of the primary particles represented by the SEM image. In the present invention, the length of the minor axis of the primary particle is the diameter (y) of the short side of the surface 1b on the surface side of the secondary particle among the surfaces of the primary particles represented by the SEM image.

The shape of the primary-phase primary particles shown in Fig. 23 (B) is a quadratic columnar phase, but the present invention is not limited to this, and it may be a columnar column, a columnar column other than a quadrangular columnar column, or a curved column.

In the SEM image of the needle-shaped primary particles shown in Fig. 23 (C), the surface 1c on the surface side of the secondary particle and the surface 2c crossing the surface 1c on the surface side appear. In the present invention, the length of the major axis of the primary particles is the diameter (x) of the long side of the surface 1c on the surface side of the secondary particles represented by the SEM image. In the present invention, the length of the minor axis of the primary particles is the diameter (y) of the short side of the surface 1c on the surface side of the secondary particles represented by the SEM image.

In the present invention, since the lengths of the long diameter and the short diameter of the primary particles are determined by image analysis of the SEM image, the long diameter and the short diameter of the primary particles mean that the surface of the secondary particles, Long diameter and short diameter measured based on the shape of the particles.

Cobalt hydroxide (1) and cobalt oxide (1) are secondary particles in which primary particles are aggregated. As the primary particles constituting the secondary particles of the cobalt hydroxide of the present invention, primary particles of a plate-like, columnar or needle-like shape having a long diameter of not less than 1.5 탆 in the SEM image analysis and primary particles other than the primary particles, Spherical or irregular primary particles, and primary particles of a plate-like, columnar or needle-like shape having a long diameter of less than 1.5 탆 in SEM image analysis. The cobalt hydroxide (1) and the cobalt oxide (1) are preferably primary particles constituting the secondary particles, and the primary particles of the plate-like, columnar or needle-like shape having the long diameter of 1.5 m or more in the SEM image analysis . That is, the cobalt hydroxide 1 and the cobalt oxide 1 are preferably (I) secondary particles in which a primary particle of a plate-like, columnar or needle-shaped primary particle having a long diameter of 1.5 m or more in the SEM image analysis is aggregated, ) Primary particles of a plate-like, columnar or acicular shape having a long diameter of not less than 1.5 탆 in SEM image analysis and spherical, irregular and primary particles of a plate-like, columnar or acicular shape having a long diameter of less than 1.5 탆 in SEM image analysis The particles are aggregated secondary particles. The presence of primary particles of a plate-like, columnar or needle-like shape is confirmed by the shape of a part of the primary particles appearing on the surface of the secondary particles in the SEM image of the secondary particles.

The ratio of the primary particles of the plate-like, columnar and needle-shaped primary particles having a major axis length of 1.5 m or more in the SEM image of the secondary particles is preferably 40% or more, more preferably 80% or more, , And even more preferably 100%. The presence of the primary particles of the plate-like, columnar and needle-shaped primary particles having a length of the long diameter of 1.5 m or more in the SEM image is in the above range, so that the compressive strength of the cobalt hydroxide (1) or the cobalt oxide (1) is increased. In the present invention, the abundance ratio of the primary particles of the plate-like, columnar and needle-shaped primary particles having a length of the major axis of 1.5 mu m or more in the SEM image of the secondary particles means that the surface of the secondary particles in the SEM image Refers to the ratio of the area of the primary particles of the platelike, the main phase and the needle-like phase having the length of the long diameter to the area of the secondary particles of 1.5 m or more in the plan view. First, image analysis is performed on an SEM image of secondary particles to project secondary particles in two dimensions, and arbitrarily extracts 100 secondary particles. Then, the area of the extracted secondary particles and the area of the primary particles having the long diameter of 1.5 mu m or more in the secondary particles are measured. Next, the ratio of the total area of the primary particles having the length of the long diameter of 1.5 mu m or more to the total area of the extracted 100 pieces of secondary particles is obtained as a percentage.

The average value of the major diameters of the primary particles of the plate-like, columnar or needle-shaped primary particles constituting the secondary particles of cobalt hydroxide (1) and cobalt oxide (1) is 1.5 μm or more, preferably 2.0 to 5.0 μm, particularly preferably 2.5 To 4.5 m. When the average value of the major diameters of the primary particles of the plate-like, columnar or needle-shaped particles is in the above range, the compressive strength and the tap density of the cobalt hydroxide (1) or the cobalt oxide (1) are increased.

First, an image analysis is performed on an SEM image of secondary particles to project secondary particles in two dimensions, and arbitrarily extracts 100 primary particles. Then, the length of the long diameter is measured for each of the extracted primary particles. Then, the lengths of the long diameters of the 100 extracted primary particles are averaged, and the average value is taken as an average value of the long diameters of the primary particles constituting the secondary particles.

As far as the present inventors have known, it has been known that as cobalt-containing hydroxides, primary particles having a particle shape of platelike or columnar form of complex hydroxide containing cobalt and nickel are aggregated to form secondary particles Bulletin 10-29820), and the maximum value of the long diameter of the primary particles of the composite oxide is less than 0.5 占 퐉. On the other hand, in the cobalt hydroxide (1), primary particles having aggregated primary particles and primary particles having a major diameter of 1.5 mu m or more of primary particles of a plate-like, columnar or needle- And the average value of the major diameters of the primary particles of the plate-like, columnar or needle-shaped particles in the secondary particles is preferably at least 1.5 μm, particularly preferably at least 2.0 μm and more preferably at most 2.5 μm and at most about 4.5 μm.

The average value of the minor axis of the primary particles of the plate-like, columnar or needle-shaped primary particles constituting the secondary particles of cobalt hydroxide (1) or cobalt oxide (1) is preferably 0.1 탆 or more, particularly preferably 0.2 to 1.5 탆 And preferably 0.3 to 1.2 mu m. When the average value of the minor axis of primary particles is in the above range, the compressive strength and the tap density of cobalt hydroxide (1) or cobalt oxide (1) are increased. The average value of the short diameters of the primary particles can be obtained by a method of obtaining the average value of the long diameters of the primary particles except that the measurement target is the length of the short diameter of the primary particles instead of the length of the long diameter of the primary particles .

When cobalt hydroxide or cobalt oxide in which a primary particle of a plate-like, columnar or needle-shaped primary particle having an average value of a long diameter of 1.5 m or more, preferably 2.0 to 5.0 m, is aggregated to form secondary particles, the lithium secondary battery has excellent cell performance From the viewpoint of obtaining lithium cobalt oxide that can be imparted.

The tap density of cobalt hydroxide (1) or cobalt oxide (1) is 0.80 g / ml or more, preferably 1.00 to 2.50 g / ml, particularly preferably 1.50 to 2.50 g / ml. When the tap density of the cobalt hydroxide (1) or the cobalt oxide (1) is in the above range, the productivity of lithium cobalt oxide can be improved and the capacity per volume of the lithium secondary battery can be increased. In addition, in the present invention, the higher the tap density, the higher the number of primary particles of the plate-like, columnar or needle-shaped primary particles having a long diameter of 1.5 탆 or more.

The method for producing cobalt hydroxide related to the raw material mixing step is not particularly limited, but it is preferable to use, for example, an example of a production method of cobalt hydroxide shown below (hereinafter also referred to as a production method (1) of cobalt hydroxide) .

A method (1) for producing cobalt hydroxide is a cobalt aqueous solution containing glycine, wherein a cobalt aqueous solution (liquid A) and an alkaline aqueous solution (liquid B) having a glycine content of 0.010 to 0.300 moles relative to 1 mol of cobalt in terms of atom, Is added to an aqueous glycine solution (liquid C), and a neutralization reaction is carried out at 55 to 75 ° C to obtain cobalt hydroxide, which is a process for producing cobalt hydroxide.

The neutralization process related to the production method (1) of cobalt hydroxide is a step of reacting the cobalt salt in solution A and the alkali in solution B in solution C by adding solution A and solution B to solution C.

Solution A is a cobalt aqueous solution containing glycine (NH ₂ CH ₂ COOH). Solution A is prepared by dissolving glycine and cobalt salts in water.

The cobalt salt related to the solution A is not particularly limited, and examples thereof include chloride, nitrate and sulfate of cobalt. Among them, a sulfate which does not contain impurities by chlorine is preferable. If necessary, a small amount of another metal salt may be coexistent.

The concentration of the cobalt ions in the liquid A is not particularly limited, but is preferably 1.0 to 2.2 mol / l, and particularly preferably 1.5 to 2.0 mol / l, in terms of atom. When the cobalt ion concentration in the liquid A is in the above range, the productivity is improved and the precipitation of the cobalt salt from the liquid A does not occur well. On the other hand, if the concentration of the cobalt ions in the solution A is less than the above range, the productivity tends to be lowered. If the concentration exceeds the above range, the cobalt salt precipitates well from the solution A.

The content of glycine relative to cobalt in solution A is 0.010 to 0.300 mol, preferably 0.050 to 0.200 mol, based on 1 mol of cobalt in atomic conversion. When the content of glycine relative to cobalt in the liquid A is in the above range, the coagulation property of the secondary particles of the cobalt hydroxide can be strengthened. Therefore, when mixing with the lithium compound in the production process of lithium cobalt oxide, Is not dissociated and the particle size can be maintained, lithium cobalt oxide having an average particle diameter of 15 to 35 mu m and a large particle diameter can be obtained. On the other hand, if the content of glycine in the liquid A is less than the above range, the coagulation property of the secondary particles of the cobalt hydroxide becomes weak. If the content exceeds the above range, unreacted cobalt salt remains in some reaction liquid, .

Solution B is an aqueous alkali solution. The liquid B is prepared by dissolving the alkali in water.

The alkali associated with the solution B is not particularly limited and includes hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide. Of these, sodium hydroxide is preferable in view of industrially low cost.

The concentration of the liquid B and the total amount of the alkali added to the liquid C are appropriately selected according to the concentration and total amount of the cobalt ions in the liquid A.

The concentration of the liquid B is preferably 5 to 15 mol / l, particularly preferably 5 to 10 mol / l.

Solution C is a glycine aqueous solution. The solution C is prepared by dissolving glycine in water.

In the neutralization step, the glycine concentration in the reaction liquid (liquid C) while adding the liquid A and the liquid B to the liquid C is preferably 0.010 to 0.250 mol / l, particularly preferably 0.030 to 0.170 mol / l to be. That is, in the neutralization step, the glycine concentration in the liquid C before the reaction and the glycine concentration of the reaction liquid (liquid C) in the neutralization reaction are preferably 0.010 to 0.250 mol / l, particularly preferably 0.030 to 0.170 mol / The glycine concentration in the C solution and the glycine concentration in the A solution before the reaction are adjusted so as to be as possible. When the concentration of glycine in the reaction liquid (liquid C) during the addition of the liquid A and liquid B to the liquid C is in the above range, the average particle size of the secondary particles of the cobalt hydroxide tends to become large. On the other hand, when the concentration of glycine in the reaction liquid (liquid C) while adding the liquid A and the liquid B to the liquid C is less than the above range, the average particle size of the secondary particles of the cobalt hydroxide tends to be small, If the amount exceeds the above range, the unreacted cobalt salt remains in some of the reaction liquid, so that productivity tends to be lowered.

The addition amount of Solution A and Solution B to Solution C is the ratio of the total number of moles of hydroxide ions in Solution B to the total number of moles of cobalt ions in Solution A in terms of atom in Solution A (the total number of OH ions in Solution B / The number of moles of the Co ion in terms of atomic conversion) is preferably 1.8 to 2.1, particularly preferably 1.9 to 2.0. The ratio of the total number of moles of hydroxide ions in the liquid B to the total number of moles of the cobalt ions in the liquid A in the liquid A is in the above range, unreacted cobalt ions do not remain in the reaction liquid (liquid C) Cobalt is easily obtained.

In the neutralization step, a glycine aqueous solution (liquid C) is put in advance in a reaction vessel, and liquid A and liquid B are added to the liquid C.

In the neutralization step, the reaction temperature of the neutralization reaction is 55 to 75 占 폚, preferably 60 to 75 占 폚, particularly preferably 65 to 75 占 폚. That is, in the neutralization step, the temperature of the reaction liquid (liquid C) when the liquids A and B are added to the liquid C, that is, the temperature of the liquid C before the reaction and the temperature of the reaction liquid , 55 to 75 캜, preferably 60 to 75 캜, particularly preferably 65 to 75 캜. The average particle diameter of the secondary particles of cobalt hydroxide is increased by the temperature of the reaction liquid (liquid C) when the liquids A and B are added to the liquid C within the above range. On the other hand, when the temperature of the reaction liquid (liquid C) when the liquids A and B are added to the liquid C is less than the above range, the average particle diameter of the secondary particles of the cobalt hydroxide is small, Further, even when the temperature of the reaction liquid (liquid C) when the liquid A and the liquid B are added to the liquid C exceeds the above range, the average particle size of the secondary particles of the cobalt hydroxide becomes small.

In the neutralization step, the pH of the reaction liquid (liquid C), that is, the pH of the liquid C before the reaction and the pH of the reaction liquid (liquid C) during the neutralization reaction when the liquids A and B are added to the liquid C is 9.0 To 11.0, preferably from 9.5 to 10.5, particularly preferably from 9.8 to 10.2. When the pH of the reaction liquid (liquid C) when adding the liquid A and the liquid B to the liquid C is in the above range, it is possible to obtain cobalt hydroxide having a large average particle diameter of secondary particles and high cohesion.

On the other hand, if the pH of the reaction liquid (liquid C) when the liquids A and B are added to the liquid C is lower than the above range, unreacted cobalt ions remain in some of the reaction liquids, , The obtained cobalt hydroxide tends to contain salts such as sulfuric acid and the like as impurities. When the pH of the reaction liquid (liquid C) when the liquid A and the liquid B are added to the liquid C is higher than the above range, the average particle size of the secondary particles of the cobalt hydroxide tends to be small. Further, in the neutralization step, the pH of the reaction liquid (liquid C) when the liquid A and the liquid B are added to the liquid C is, for example, the pH of the hydroxide ion in the liquid B and the concentration of the cobalt ion in the liquid A The ratio of the concentration of the hydroxide ion in the liquid B, and the ratio of the addition rate of the liquid B to the liquid C with respect to the liquid A.

In the neutralization step, the ratio of the addition rate of hydroxide ions in liquid B (liquid B / liquid A) to the addition rate of cobalt ions in liquid A when liquid A and liquid B are added to liquid C is preferably 1.8 to 2.1, particularly preferably 1.9 to 2.0. The ratio of the addition rate of the hydroxide ions in the liquid B to the addition rate of the cobalt ions in the liquid A is the same as the addition rate of the cobalt ions in the liquid A added to the reaction vessel (mol / (Mol / min) of the addition amount of the hydroxide ion in the solution.

In the neutralization step, the addition time from the start of addition of the solution A and the solution B to the solution C when adding the solution A and the solution B to the solution C is not particularly limited, , Preferably 0.5 to 10 hours, and particularly preferably 1 to 5 hours.

In the neutralization step, the stirring speed of the reaction liquid (liquid C) at the time of mixing the liquid A and the liquid B, that is, the stirring speed of the liquid C immediately before the reaction and the stirring speed of the reaction liquid (liquid C) But it is preferably selected depending on the size of the reaction vessel, the diameter of the stirring blade, the amount of the reaction liquid, etc., but is preferably 0.5 to 4.0 m / sec at the stirring blade and 0.5 to 2.0 m / sec at the stirring blade. In the neutralization step, the agitation speed in the time zone on the start side, preferably in the time zone from immediately after the start of the addition to one hour after the addition of the solution A and the solution B to the solution C is made gradually, It is preferable that the speed is made strong in that the average particle diameter of the secondary particles of the cobalt hydroxide can easily be increased and the high charging can be achieved.

In the production method (1) of cobalt hydroxide, cobalt hydroxide (secondary particles) is obtained by performing the neutralization process in this way.

After the neutralization step, the cobalt hydroxide (secondary particles) produced in the reaction solution is separated from the reaction solution by cobalt hydroxide (filtration, centrifugation, etc.) and washed and dried if necessary.

The cobalt hydroxide obtained by the production method (1) of cobalt hydroxide has an average particle diameter of secondary particles of preferably 15 to 40 탆, particularly preferably 18 to 35 탆, which is larger than that of the conventional ones, 5 to 50 MPa, preferably 8 to 30 MPa. In addition, cobalt hydroxide obtained by carrying out the production method (1) of cobalt hydroxide is a secondary particle in which primary particles are aggregated, and as primary particles constituting secondary particles, in the image analysis of an SEM image Has a specific particle size of not less than 1.5 탆, preferably 2.0 to 5.0 탆, particularly preferably 2.5 to 4.5 탆, and the cobalt hydroxide having such a specific particle shape has a high compressive strength .

Therefore, the cobalt hydroxide obtained by carrying out the production method (1) of cobalt hydroxide has a problem that the secondary particles are not well dissociated when mixed with the lithium compound in the raw material mixing step, so that even after mixing with the lithium compound, And has a large average particle diameter of 15 to 40 mu m. Even when the cobalt hydroxide obtained by carrying out the production process (1) of cobalt hydroxide, that is, the cobalt hydroxide (1), is subjected to the pulverization treatment with a shear force as high as that of a domestic coffee mill, the decrease in the average particle size of the secondary particles is small Of the average particle diameter of the secondary particles by the pulverization treatment is not more than 7.0 mu m and the change of the particle size distribution before and after the pulverization mixing is small.

Therefore, according to the cobalt hydroxide obtained by the method (1) for producing cobalt hydroxide, it is not necessary to use a large amount of lithium compound for the particle growth when reacting with the lithium compound. Therefore, Lithium cobalt oxide having an excess lithium amount smaller than that of conventional lithium cobalt oxide can be obtained at a molar ratio (Li / Co) of lithium to atomic conversion of cobalt to lithium in the range of 0.900 to 1.040.

The method for producing cobalt oxide associated with the raw material mixing step is not particularly limited, but can be suitably selected, for example, by a method for producing cobalt oxide shown below (hereinafter also referred to as a method (1) for producing cobalt oxide) .

The production method (1) for producing cobalt oxide is characterized in that cobalt hydroxide obtained by carrying out the production method (1) of cobalt hydroxide is calcined at 200 to 700 ° C, preferably 300 to 500 ° C, And a process for producing cobalt oxide. The firing time is 2 to 20 hours, preferably 2 to 10 hours. The firing atmosphere is an oxidizing atmosphere such as in air or oxygen gas.

The cobalt oxide obtained by carrying out the production process (1) of cobalt hydroxide and cobalt oxide obtained by the production process (1) of cobalt hydroxide has an average particle diameter of the secondary particles of preferably 15 to 40 m, Is 18 to 35 占 퐉, which is larger than that of the conventional one and has a high compressive strength of 5 to 50 MPa, preferably 8 to 30 MPa,

The cobalt hydroxide obtained by carrying out the production process (1) of the cobalt hydroxide and the cobalt oxide obtained by carrying out the production process (1) of cobalt hydroxide has a cobalt content of 2 The change in the particle size distribution of the tea particles is small, and the decrease in the average particle size of the secondary particles by the pulverization treatment is preferably not more than 7.0 mu m. Therefore, when cobalt hydroxide or lithium cobalt oxide and lithium compound are mixed in the production of lithium cobalt oxide, secondary particles of cobalt hydroxide or cobalt oxide are not dissociated well and lithium cobalt oxide having a large average particle size is obtained .

From the above, the cobalt oxide obtained by carrying out the production method (1) of the cobalt hydroxide and the cobalt oxide obtained by the production method (1) of the cobalt hydroxide is not limited to the raw material mixing process Is used preferably as cobalt hydroxide or cobalt oxide as a raw material and secondary particles are not well dissociated when mixed with a lithium compound in the raw material mixing step so that even after mixing with a lithium compound, And a large average particle diameter of 40 mu m is maintained.

The cobalt hydroxide and the cobalt oxide used in the raw material mixing step in the method for producing lithium cobalt oxide of the present invention may be either one or both of them.

In the method for producing lithium cobalt oxide of the present invention, the lithium compound related to the raw material mixing step is not particularly limited as long as it is a lithium compound generally used as a raw material for the production of lithium cobalt oxide, and oxides, hydroxides, Nitrate, organic acid salts and the like. Of these, lithium carbonate which is industrially cheap is preferable.

The average particle diameter of the lithium compound is particularly preferably 0.1 to 200 占 퐉, preferably 2 to 50 占 퐉 because of good reactivity.

(Li / Co mixed mole ratio) of 0.9 to 1.040, preferably 1: 1 to 1: 2, in the raw material mixing step when the cobalt hydroxide or the cobalt oxide and the lithium compound are mixed, Is in the range of 0.950 to 1.030, particularly preferably 0.980 to 1.020. In the calculation of the molar ratio, when both cobalt hydroxide and cobalt oxide are used as the cobalt source, the number of moles of Co is the total number of moles, and when two or more kinds of lithium compounds are used as the lithium source , The number of moles of Li is the total number of moles of Li. When the ratio of the number of moles of lithium in atomic conversion to the number of moles of cobalt in terms of atom is within the above range, the capacity retention rate of the lithium secondary battery is increased. On the other hand, when the ratio of the number of moles of lithium in atomic conversion to the moles of cobalt in terms of atomic ratio is less than the above range, there is a tendency that unreacted cobalt exists because lithium is insufficient and the discharge capacity per weight is remarkably decreased , And if it exceeds the above range, the capacity retention rate of the lithium secondary battery is lowered.

In the raw material mixing step, for example, a mixing method using a ribbon mixer, a Henschel mixer, a super mixer, a Nauter mixer, or the like can be given as a method of mixing cobalt hydroxide or cobalt oxide with a lithium compound.

Further, in the raw material mixing step, a compound having a metal atom (M) in addition to cobalt hydroxide or cobalt oxide and a lithium compound may be added and mixed. The compound having an M metal atom is a compound having at least one metal atom (M) selected from a transition metal atom other than Co described above or a metal atom with an atomic number of 9 or more, specifically, an oxide of a metal atom (M) , Hydroxides, sulfates, carbonates, halides, organic acid salts and the like. The compound having a metal atom (M) may be a composite oxide containing both a titanium atom and a M atom, such as a titanate having a metal atom (M), and may be a single compound Alternatively, two or more different kinds of compounds may be used in combination.

The average particle diameter of the compound having the metal atom (M) is preferably 0.1 to 15 占 퐉, particularly preferably 0.1 to 10 占 퐉 in that the reactivity becomes good.

As the compound having a metal atom (M), a compound having a magnesium atom and a compound having a titanium atom are preferable, and in particular, magnesium fluoride and titanium oxide are preferred from the viewpoint of obtaining a lithium secondary battery having excellent cell performance Do. By using magnesium fluoride as a compound having a metal atom (M), the capacity retention rate can be improved by the synergistic effect of the Mg atom and the F atom. By using titanium oxide (TiO ₂ ) as a compound having metal atoms (M), the average operating voltage can be improved by the action of Ti atoms.

In the case of mixing a compound having a metal atom (M) in a raw material mixing process, the mixing amount of the compound having a metal atom (M) is preferably such that the amount of the metal atom (M) M) is preferably from 0.10 to 1.50% by mass, and particularly preferably from 0.20 to 0.80% by mass. The mixing amount of the compound having the metal atom (M) in the above range is preferable from the viewpoint of suppressing the reduction of the discharge capacity per weight and improving the battery performance such as the capacity retention rate and the average operation voltage.

The reaction process relating to the production method of lithium cobalt oxide of the present invention is characterized in that a raw material mixture of a compound containing metal atoms (M), which is obtained by mixing a cobalt hydroxide or a cobalt oxide with a lithium compound and if necessary, Thereby reacting cobalt hydroxide or cobalt oxide with a lithium compound and a compound having metal atoms (M), if necessary, to obtain lithium cobalt oxide.

In the reaction step, when the raw material mixture is heated to react the cobalt hydroxide or the cobalt oxide with the lithium compound and the compound having the metal atom (M) optionally mixed, the reaction temperature is preferably 800 to 1150 ° C, Is 900 to 1100 ° C. The reaction time is 1 to 30 hours, preferably 5 to 20 hours. The reaction atmosphere is an oxidizing atmosphere such as in air or oxygen gas. Further, in the present invention, when a compound having a titanium atom is mixed as a raw material, it is preferable to actively circulate air, oxygen gas or the like into the atmosphere during the reaction in order to produce Li ₂ TiO ₃ well .

After the reaction step, lithium cobalt oxide is obtained by subjecting the resulting lithium cobalt oxide to a crushing or classification as necessary.

According to the method for producing lithium cobalt oxide of the present invention, when a compound having cobalt hydroxide or cobalt oxide, a lithium compound and a metal atom (M) to be mixed as required is reacted, a large amount of lithium compound is mixed It is possible to obtain lithium cobalt oxide having an excessively small amount of lithium at a molar ratio of Li / Co of 0.900 to 1.040 while being lithium cobalt oxide having an average particle size of 15 to 35 mu m and having a large average particle diameter of 15 to 35 mu m.

According to the lithium cobalt oxide of the present invention, a lithium secondary battery having a high capacity and a high capacity retention rate can be provided.

In addition, in the raw material mixing step, lithium cobalt oxide containing metal atoms (M) obtained by mixing a compound having metal atoms (M) and performing a reaction step can improve various battery performance. By using a compound having a magnesium atom and / or a compound having a titanium atom as a compound containing a metal atom (M), battery performance such as capacity retention rate and average operating voltage can be increased. In particular, by using magnesium fluoride as a compound containing a metal atom (M), a magnesium atom can be contained in the particles of lithium cobalt oxide by solid solution, and at this time, preference is given to the surface of lithium cobalt oxide And the fluorine atom can also be contained in the lithium cobalt oxide. Therefore, the capacity retention rate can be increased by the synergistic effect of the Mg atom and the F atom.

Also, by using titanium oxide (TiO ₂ ) as a compound having a metal atom (M), a titanium atom can be allowed to exist in the depth direction from the particle surface of the lithium cobalt oxide, and at this time, The concentration gradient becomes maximum at the surface, so that the average operation voltage can be increased by the action of Ti atoms. It is also preferable that the Ti atom existing at a high concentration on the particle surface of the lithium cobalt oxide is Li ₂ TiO ₃ , because the battery performance such as the rate characteristic becomes higher. By using a compound having a Mg atom and a compound having a Ti atom as a compound having a metal atom (M), a lithium secondary battery having a higher capacity retention rate and an average operating voltage can be obtained.

The lithium cobalt oxide of the present invention exhibits excellent performance as a positive electrode active material of a lithium secondary battery and is thus used as a positive electrode active material for a lithium secondary battery.

The positive electrode active material for a lithium secondary battery of the present invention contains lithium cobalt oxide of the present invention. The content of lithium cobalt oxide in the positive electrode active material for a lithium secondary battery of the present invention is 95.0 to 100.0% by mass, preferably 97.0 to 99.5% by mass.

The lithium secondary battery of the present invention is a lithium secondary battery using the lithium cobalt oxide of the present invention as a positive electrode active material for a lithium secondary battery. The lithium secondary battery includes a positive electrode, a negative electrode (negative electrode), a separator, Electrolyte.

When the lithium cobalt oxide of the present invention is used as a positive electrode active material for a lithium secondary battery, the content of lithium cobalt oxide in the positive electrode active material for a total lithium secondary battery is 95.0 to 100.0% by mass, preferably 97.0 to 99.5% to be.

The positive electrode related to the lithium secondary battery of the present invention is formed, for example, by applying and drying the positive electrode mixture on the positive electrode collector. The positive electrode material mixture is composed of a positive electrode active material, a conductive agent, a binder, and a filler added as needed. In the lithium secondary battery of the present invention, the positive electrode active material for a lithium secondary battery of the present invention is uniformly coated on the positive electrode. Therefore, the lithium secondary battery of the present invention has high battery performance, particularly high load characteristics and cycle characteristics.

The content of the positive electrode active material contained in the positive electrode material mixture related to the lithium secondary battery of the present invention is preferably 70 to 100% by weight, and more preferably 90 to 98% by weight.

The positive electrode current collector related to the lithium secondary battery of the present invention is not particularly limited as long as it is an electron conductor that does not cause a chemical change in the battery constituted. Examples of the positive electrode current collector include stainless steel, nickel, aluminum, titanium, Nickel, titanium, and silver on the surface of stainless steel, and the like.

The surface of these materials may be oxidized and used. Alternatively, surface irregularities may be formed on the surface of the current collector by surface treatment. Examples of the form of the current collector include a foil, a film, a sheet, a net, a punched product, a ras body, a porous body, a foam, a fiber group, and a molded product of a nonwoven fabric. The thickness of the current collector is not particularly limited, but is preferably 1 to 500 탆.

The conductive agent relating to the lithium secondary battery of the present invention is not particularly limited as long as it is an electron conductive material which does not cause chemical change in the battery constituted. For example, graphite such as natural graphite and artificial graphite, carbon black such as carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black, conductive fibers such as carbon fiber and metal fiber, 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. As natural graphite, Examples thereof include scaly graphite, scaly graphite, and earth graphite. These may be used alone or in combination of two or more. The mixing ratio of the conductive agent is 1 to 50% by weight, preferably 2 to 30% by weight, in the positive electrode material mixture.

Examples of the binder relating to the lithium secondary battery of the present invention include starch, polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, regenerated cellulose, diacetylcellulose, polyvinylpyrrolidone, (EPDM), sulfonated EPDM, styrene butadiene rubber, fluorine rubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexa < RTI ID = 0.0 > Perfluoroalkyl vinyl ether copolymers, vinylidene fluoride-hexafluoropropylene copolymers, vinylidene fluoride-chlorotrifluoroethylene copolymers, ethylene-tetrafluoroethylene copolymers, ethylene-tetrafluoroethylene copolymers, Polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, polyvinylidene fluoride- Propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer (Na ⁺ ) ion crosslinked product, an ethylene-methacrylic acid copolymer or its (Na ⁺ ) ion crosslinked product, an ethylene-acrylic acid methyl copolymer or a (Na ⁺ ) ion crosslinked product thereof , Ethylene-methyl methacrylate copolymer or its (Na ⁺ ) ion crosslinked substance, polysaccharide such as polyethylene oxide, thermoplastic resin, rubber elastic polymer and the like, and they can be used singly or in combination of two or more kinds. have. When a compound containing a functional group reactive with lithium such as a polysaccharide is used, it is preferable to add a compound such as an isocyanate group to inactivate the functional group. The blending ratio of the binder is 1 to 50% by weight, preferably 5 to 15% by weight, in the positive electrode material mixture.

The filler related to the lithium secondary battery of the present invention suppresses the volume expansion of the positive electrode in the positive electrode mixture, and is added as needed. As the filler, any fibrous material which does not cause a chemical change in the battery constituted can be used. For example, fibers such as olefin-based polymers such as polypropylene and polyethylene, glass, and carbon are used. The amount of the filler to be added is not particularly limited, but it is preferably 0 to 30% by weight in the positive electrode material mixture.

The negative electrode related to the lithium secondary battery of the present invention is formed by applying and drying the negative electrode material on the negative electrode collector. The negative electrode current collector related to the lithium secondary battery of the present invention is not particularly limited as long as it is an electron conductor that does not cause a chemical change in the battery constituted. Examples of the current collector include stainless steel, nickel, copper, titanium, aluminum, Or stainless steel surface treated with carbon, nickel, titanium or silver, and aluminum-cadmium alloy. The surface of these materials may be oxidized and used. Alternatively, surface irregularities may be formed on the surface of the current collector by surface treatment. Examples of the form of the current collector include a foil, a film, a sheet, a net, a punched product, a ras body, a porous body, a foam, a fiber group, and a molded product of a nonwoven fabric. The thickness of the current collector is not particularly limited, but is preferably 1 to 500 탆.

The negative electrode material related to the lithium secondary battery of the present invention is not particularly limited, and examples thereof include carbonaceous materials, metal complex oxides, lithium metals, lithium alloys, silicon-based alloys, tin-based alloys, metal oxides, Chalcogen compounds, Li-Co-Ni-based materials, and Li ₄ Ti ₅ O ₁₂ . Examples of the carbonaceous material include a non-graphitized carbon material, a graphite carbon material, and the like. As the metal composite oxide, for ^{_{example, Sn p (M 1) 1}} -p (M 2) q O r ( wherein, M ¹ represents at least one element selected from Mn, Fe, Pb, and Ge, M ² represents at least one element selected from the group consisting of Al, B, P, Si, Group 1, Group 2, Group 3 and Halogen elements of the periodic table and 0 <p≤1, 1≤q≤3, ? 8), Li _t Fe ₂ O ₃ (0? _T ? 1), and Li _t WO ₂ (0? _T ? 1). Examples of the metal oxide include GeO ₂ , SnO ₂ , 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 related to the lithium secondary battery of the present invention, an insulating thin film having a high ion permeability and a predetermined mechanical strength is used. A sheet or a nonwoven fabric made of an olefin-based polymer such as polypropylene, glass fiber, polyethylene or the like is used because of its organic solvent and hydrophobicity. The pore diameter of the separator is generally in a range useful for a battery, and is, for example, 0.01 to 10 mu m. The thickness of the separator may be in a range for general batteries, and is, for example, 5 to 300 占 퐉. When a solid electrolyte such as a polymer is used as an electrolyte to be described later, the solid electrolyte may also serve as a separator.

The nonaqueous electrolyte containing a lithium salt related to the lithium secondary battery of the present invention is composed of a nonaqueous electrolyte and a lithium salt. As the non-aqueous electrolyte relating to the lithium secondary battery of the present invention, a non-aqueous electrolyte, an organic solid electrolyte, and an inorganic solid electrolyte are used. Examples of the non-aqueous electrolyte include, for example, N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylenecarbonate, dimethylcarbonate, diethylcarbonate,? -Butyrolactone, But are not limited to, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, phosphoric acid triester, phosphoric acid triester, Methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, di And organic solvents such as ethyl ether, 1,3-propane sultone, methyl propionate, ethyl propionate and the like, or a mixture of two or more of these solvents.

The organic solid electrolyte relating to the lithium secondary battery of the present invention includes, for example, 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, a polyphosphazene, A polymer containing an ionic dissociation group such as polyvinylidene chloride, polyvinyl alcohol, polyvinyl alcohol, polyvinylidene fluoride and polyhexafluoropropylene; a mixture of a polymer containing an ionic dissociation group and the nonaqueous electrolyte; and the like.

As the inorganic solid electrolyte related to the lithium secondary battery of the present invention, a nitride, a halide, an oxygen acid salt, a sulfide or the like of Li can be used. For example, Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N- _{LiI-LiOH, LiSiO 4, LiSiO} 4 -LiI-LiOH, Li 2 SiS 3, Li 4 SiO 4, Li 4 SiO 4 -LiI-LiOH, P 2 S 5, Li 2 S or Li ₂ SP ₂ S _5, Li _{2 S-SiS 2, Li 2} S-GeS 2, Li 2 S-Ga 2 S 3, Li 2 SB 2 S 3, Li 2 SP 2 S 5 -X, Li 2 S-SiS 2 -X, Li 2 S -GeS ₂ -X, Li ₂ S-Ga ₂ S ₃ -X, Li ₂ SB ₂ S ₃ -X, wherein X is at least one selected from LiI, B ₂ S ₃ or Al ₂ S ₃ Or more).

When the inorganic solid electrolyte is amorphous (free), lithium phosphate (Li ₃ PO ₄ ), lithium oxide (Li ₂ O), lithium sulfate (Li ₂ SO ₄ ), phosphorus oxide (P ₂ O ₅ ) lithium (Li ₃ BO ₃₎ compounds containing oxygen, such _{as, Li 3 PO 4 - u N} 2u / 3 (u is 0 <u <4), Li 4 SiO 4 - u N 2u / 3 (u are 0 < containing a nitrogen such as Li ₄ GeO _{4 -u} N _{2u / 3} (u is 0 <u <4), Li ₃ BO _{3 - u} N _{2u / 3} (u is 0 <u <3) The compound can be contained in the inorganic solid electrolyte. By adding the oxygen-containing compound or the nitrogen-containing compound, the gap between the amorphous framework to be formed can be enlarged so as to alleviate disturbance of lithium ion migration and further improve the ion conductivity.

As the lithium salt related to the lithium secondary battery of the present invention, it is used to dissolve the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO _4, LiBF _4, LiB ₁₀ Cl _10, LiPF _6, LiCF ₃ SO _{3, LiCF 3 CO 2, LiAsF} 6, LiSbF 6, LiB 10 Cl 10, LiAlCl 4, CH 3 SO 3 Li, CF 3 SO 3 Li, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic And lithium salts, lithium salts, lithium lithium salts, lithium tetraphenylborate, imides, and the like.

The following compounds may be added to the nonaqueous electrolyte for the purpose of improving discharge, charging characteristics, and flame retardancy. For example, there may be mentioned pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexamphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, A monomer of a conductive polymer electrode active material, a triethylene phosphonamide, a trialkylphosphine, a monoalkylphosphine, a trialkoxyphosphine, an alkylpolysiloxane, An aryl compound having a carbonyl group, a 4-alkyl morpholine, a bicyclic tertiary amine, an oil, a phosphonium salt and a tertiary sulfonium salt, a phosphazene, a carbonic ester, and the like. In order to make the electrolyte nonflammable, a halogenated solvent such as carbon tetrachloride and ethylene trifluoride may be contained in the electrolytic solution. Further, carbon dioxide gas may be contained in the electrolytic solution in order to make it suitable for high-temperature preservation.

The lithium secondary battery of the present invention is a lithium secondary battery excellent in cycle characteristics and average operating voltage, and the shape of the battery may be any shape such as a button, a sheet, a cylinder, an angle, and a coin.

The use of the lithium secondary battery of the present invention is not particularly limited, but examples thereof include a notebook PC, a laptop PC, a pocket word processor, a cellular phone, a cordless magnet, a portable CD player, a radio, a liquid crystal television, Electronic devices such as a shaver, a memory card, and a video movie, electronic devices for consumer use such as automobiles, electric vehicles, game devices, and power tools.

Example

Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited to these examples.

&Lt; Preparation of raw material aqueous solution for cobalt hydroxide production &gt;

(1) Cobalt aqueous solution 1

425.5 g of industrial cobalt sulfate heptahydrate and 5.7 g of glycine were dissolved in water and further water was added to make a total amount of 1 liter to prepare a cobalt aqueous solution 1. At this time, the cobalt ion concentration in the cobalt aqueous solution 1 was 1.5 mol / l in terms of the atom, the glycine concentration was 0.075 mol / l, and glycine was 0.050 mol relative to 1 mol of cobalt in terms of atom.

(2) Cobalt aqueous solution 2

425.5 g of industrial cobalt sulfate heptahydrate and 1.1 g of glycine were dissolved in water and further water was added to make a total amount of 1 liter to prepare a cobalt aqueous solution 2. At this time, the cobalt ion concentration in the cobalt aqueous solution 2 was 1.5 mol / l in terms of atom, the glycine concentration was 0.015 mol / l, and glycine was 0.010 mol based on 1 mol of cobalt in terms of atom.

(3) Cobalt aqueous solution 3

425.5 g of industrial cobalt sulfate heptahydrate was dissolved in water and further water was added to make a total amount of 1 liter to prepare a cobalt aqueous solution 3. At this time, the cobalt ion concentration in the cobalt aqueous solution 3 was 1.5 mol / l in atomic conversion.

(4) Cobalt aqueous solution 4

425.5 g of industrial cobalt sulfate heptahydrate and 0.9 g of glycine were dissolved in water and further water was added to make a total amount of 1 liter to prepare a cobalt aqueous solution 4. At this time, the cobalt ion concentration in the cobalt aqueous solution 4 was 1.5 mol / l in terms of the atom, the glycine concentration was 0.012 mol / l, and glycine was 0.008 mol relative to 1 mol of cobalt in atomic conversion.

(5) Alkali aqueous solution 1

Sodium hydroxide was dissolved in water so as to be an aqueous solution of sodium hydroxide of 25 mass%, and 0.5 liter of the aqueous alkaline solution 1 was prepared. At this time, the concentration of the aqueous alkaline solution was 7.9 mol / l.

(6) Initial charge amount 1

1.4 g of glycine was dissolved in water and further water was added thereto to make the total amount to 0.35 L to prepare an initial charge liquid 1. [ At this time, the glycine concentration in the initial charging liquid 1 was 0.054 mol / l.

(7) Initial charge 2

0.3 g of glycine was dissolved in water, and further water was added to make the total amount to 0.35 L to prepare an initial charging liquid 2. [ At this time, the glycine concentration in the initial charging liquid 2 was 0.011 mol / l.

(8) Initial charge amount 3

0.35 L of water was used as the initial charging liquid 3. In short, the initial charging liquid 3 does not contain glycine.

(9) Initial charge 4

0.2 g of glycine was dissolved in water, and water was further added to make the total amount to 0.35 L to prepare an initial charge liquid 4. [ At this time, the glycine concentration in the initial charging liquid 4 was 0.008 mol / l.

(Synthesis Examples 1 to 9)

&Lt; Preparation of cobalt hydroxide &gt;

In a 2 L reaction vessel, 0.35 L of the initial charging liquid was charged and heated to the reaction temperature shown in Table 1.

Subsequently, while the reaction liquid (initial charge liquid) in the reaction vessel was stirred at the stirring rate shown in Table 1, a cobalt aqueous solution and an aqueous alkaline solution were added to the reaction vessel so that the pH of the reaction liquid became the pH described in Table 1, The reaction was carried out at a reaction temperature and dropping time shown in Fig. 1, and neutralization reaction was carried out.

After the neutralization reaction, the reaction solution was cooled, and then the product was filtered and washed with water, and then dried at 70 ° C to obtain cobalt hydroxide.

Table 2 shows the average particle diameter, compressive strength, grindability and tap density of the secondary particles of the obtained cobalt hydroxide.

1) The stirring main axis "1.0 to 2.0" means stirring at 1.0 m / sec for one hour after the start of mixing and then at 2.0 m / sec thereafter.

* In Table 2, the average particle diameter of the secondary particles (a) represents the average particle diameter of the secondary particles (b) before the pulverization treatment by the household mixer, and the average particle diameter of the secondary particles Indicates the particle diameter.

** In Table 2, the abundance ratio is the ratio of the total area of the primary particles having a major diameter of 1.5 탆 or more to the total area of the secondary particles.

&Lt; Sample A having a magnesium atom &gt;

As a compound having a magnesium atom, MgF ₂ (manufactured by Stellar Company) having an average particle size of 6.0 탆 was used.

<Compound B having a titanium atom>

TiO ₂ (trade name: F1 manufactured by Showa Denko K.K.) having an average particle size of 0.3 탆 was used as a compound having a titanium atom.

(Examples 1 to 3 and Comparative Examples 1 to 4)

<Preparation of Lithium Cobaltate>

The cobalt hydroxide thus obtained and lithium carbonate were mixed at a Li / Co molar ratio shown in Table 3, and then heated at the reaction temperature shown in Table 3 to prepare lithium cobalt oxide.

Table 3 shows the average particle size and the residual alkali amount of the obtained lithium cobalt oxide.

(Examples 4 to 10 and Comparative Examples 5 to 11)

<Preparation of Lithium Cobaltate>

The obtained cobalt hydroxide and lithium carbonate were weighed in a molar ratio of Li / Co shown in Table 4, and further, a compound sample A having a magnesium atom and a compound sample B having a titanium atom were weighed so that the Mg atom And the content of the Ti atoms were determined so as to be the mass% of the Mg atoms and the Ti atoms shown in Table 4, and these were mixed and then heated at the reaction temperature shown in Table 4 to obtain cobalt Lithium was produced.

Table 5 shows the average particle diameter, tap density and residual alkali amount of the lithium cobalt oxide containing the metal atom (M) thus obtained. An SEM photograph of lithium cobalt oxide containing the metal atom (M) obtained in Example 6 is shown in Fig.

Further, the surface of the lithium cobalt oxide containing Mg atoms and Ti atoms obtained in Example 5 was analyzed by X-ray photoelectron spectroscopy (XPS) to measure the Mg peak and the Ti peak in the depth direction Respectively. The results are shown in Fig.

The conditions of the X-ray spectroscopic electron spectroscopy are as follows.

Etching rate: 7.7 nm / min (surface etching at Ar)

Etching time: 10 seconds × 2 times, 20 seconds × 2 times, 1 minute × 2 times, 2 minutes × 2 times, 3 minutes × 2 times

From the results shown in Fig. 22, it can be seen that Ti atoms exist from the inside of the particles of lithium cobalt oxide to the surface of the particles, and the concentration of Ti atoms has a concentration gradient that becomes the maximum concentration at the surface of the particles.

The particles of lithium cobalt oxide containing the Mg atom and the Ti atom obtained in Example 5 were cut and the particle cross section was measured with a field emission electron probe microanalyzer (FE-EPMA) (apparatus name: JXA8500F Nippon Denshi measurement condition: acceleration voltage 15 KV, magnification of 3000, irradiation current of 4.861 e - 08 A). As a result of the mapping analysis of FE-EPMA, it was confirmed that Ti atoms exist in the inside of the particle and on the surface of the particle, and particularly exist at a high concentration on the particle surface.

In addition, FE-EPMA analysis was carried out in the same manner as in Example 7, but it was confirmed that Ti atoms exist in the inside of the particle and on the surface of the particle, and particularly exist at a high concentration on the particle surface.

Therefore, in lithium cobalt oxide containing Mg atoms and Ti atoms in Examples 5 and 7, the Ti atoms exist in the depth direction from the particle surface of the lithium cobalt oxide, and the concentration of the Ti atoms is maximum As shown in Fig.

Further, X-ray diffraction (XRD) analysis of lithium cobalt oxide containing Mg atoms and Ti atoms in Examples 5 and 7 using a CuK? Ray as a source of light showed that the diffraction peaks of Li ₂ TiO ₃ at ₂ ? = 20.5 Was confirmed. As a result, the diffraction peaks of Li ₂ TiO ₃ were confirmed in Examples 5 and 7.

A battery performance test was conducted as follows.

&Lt; Preparation of lithium secondary battery &gt;

91% by weight of lithium cobalt oxide or lithium cobaltate containing M atoms obtained in Examples 1 to 11 and Comparative Examples 1 to 11, 6% by weight of graphite powder and 3% by weight of polyvinylidene fluoride were mixed to prepare a positive electrode, And dispersed in N-methyl-2-pyrrolidinone to prepare a kneading paste. The kneading paste was applied to an aluminum foil, followed by drying and pressing to obtain a negative electrode plate having a diameter of 15 mm.

Using this positive electrode plate, a coin-type lithium secondary battery was produced by using respective members such as a separator, a negative electrode, a positive electrode, a current collecting plate, a mounting bracket, an external terminal, and an electrolyte. Of these, a metallic lithium foil was used as the negative electrode, and 1 liter of a 1: 1 kneading solution of ethylene carbonate and methyl ethyl carbonate dissolved in 1 mole of LiPF ₆ was used as the electrolytic solution.

Then, the performance of the obtained lithium secondary battery was evaluated. The results are shown in Table 6.

&Lt; Evaluation of physical properties &

(1) average particle diameter of secondary particles of cobalt hydroxide, average particle diameter of lithium cobalt oxide

Was measured by a laser diffraction / scattering method. For the measurement, Microtrack MT3300EXII manufactured by Nikkiso Co., Ltd. was used.

(2) Compressive strength of secondary particles of cobalt hydroxide

And measured by a Shimadzu compact compression tester MTC-W.

(3) Grinding characteristics

The secondary particles (a) of cobalt hydroxide were pulverized for 10 seconds by a domestic mixer (IFM-660DG, manufactured by Iwatani), and the average particle diameter of the secondary particles (b) after the pulverization treatment was measured. Figs. 1 to 10 show the particle size distribution before and after the pulverization treatment of the secondary particles.

(4) Tap density

30 g of a sample was placed in a 50 ml measuring cylinder on the basis of the method of external appearance density or appearance cost (specific volume) described in JIS-K-5101, set in a DUAL AUTOTAP apparatus manufactured by Yuasa Ionics Co., The capacitance was read and the apparent density was calculated to obtain the tap density.

(5) Measurement of long diameter and short diameter of primary particles

100 primary particles were arbitrarily extracted and subjected to image analysis on an SEM image to measure the long diameter and the short diameter of each primary particle observed on the SEM image. Then, the average value of the long diameter and the average value of the short diameter of the 100 extracted primary particles were calculated. SEM photographs of the cobalt hydroxide obtained in Synthesis Example 1, Synthesis Example 5, Synthesis Example 7, Synthesis Example 8 and Synthesis Example 9 are shown in FIGS. 11 to 20.

(6) Measurement of the existence ratio of primary particles having a long diameter of 1.5 m or more

100 secondary particles were arbitrarily extracted, and the total area of the extracted secondary particles and the total area of the plate-like, columnar or needle-shaped particles having the long diameter of 1.5 m or more in the secondary particles were determined on the SEM image, The ratio of the total area of the primary particles of the plate-like, columnar or acicular shape having the long diameter of 1.5 탆 or more was calculated.

(7) Amount of residual alkali

30 g of sample is weighed to 10 mg unit and placed in a beaker. Weigh 100 ml of deionized water with a measuring cylinder, add to the beaker, and stir with a magnetic stirrer for 5 minutes. After completion of the stirring, the suspension is filtered with a filter paper, and the filtrate is recovered. Separately, 60 ml of the filtrate is collected with a measuring cylinder, titrated with N / 10 hydrochloric acid solution with an automatic titrator, and the second end point in the neutralization reaction of Li ₂ CO ₃ is read. Each measured value was substituted into the following equation to determine the residual alkali amount.

Residual alkali amount = {N _HCl x f _HCl x A / 1000 x M _{Li 2 CO 3} / B x C / D} / 2 x 100

N _HCl : molar concentration of hydrochloric acid solution used for titration

f _HCl : Potency of the hydrochloric acid solution used for titration

A: The dropping amount (ml) of the hydrochloric acid solution required until neutralization

M _Li2CO3: Li ₂ CO ₃ Molecular Weight

B: Amount of sample used (g)

C: Amount of deionized water (ml) used for extraction of excess Li powder

D: Amount (ml) of the filtrate used in one titration)

&Lt; Performance evaluation of battery &

The produced coin-type lithium secondary battery was operated at room temperature under the following test conditions, and the following battery performance was evaluated.

(1) Test conditions for cycle characteristic evaluation

First, charging was performed from 0.5 C to 4.5 V over 2 hours, and then constant current / constant voltage charging (CCCV charging) was performed to maintain the voltage at 4.5 V for 3 hours. Thereafter, charging and discharging were carried out at a constant current discharge (CC discharge) from 0.2 C to 2.7 V, and the discharging capacity was measured every cycle by performing these operations in one cycle. This cycle was repeated for 20 cycles.

2) Initial discharge capacity (per weight)

The discharge capacity at the first cycle in the cycle characteristic evaluation was regarded as the initial discharge capacity.

(3) Initial discharge capacity (per volume)

Was calculated by multiplying the electrode density measured at the time of manufacturing the positive electrode plate by the initial discharge capacity (per weight).

(4) Capacity retention rate

From the discharge capacity (per weight) of each of the first cycle and the 20th cycle in the cycle characteristics evaluation, the capacity retention ratio was calculated by the following formula.

Capacity Retention Rate (%) = (Discharge Capacity at the 20th Cycle / Discharge Capacity at the First Cycle) × 100

(5) Average operating voltage

The average operation voltage at the 20th cycle in the cycle characteristic evaluation was regarded as an average operation voltage.

Industrial availability

According to the present invention, a lithium secondary battery having a high capacity and a high capacity retention rate can be produced.

Claims (13)

The cobalt hydroxide or the cobalt oxide and the lithium compound having an average particle diameter of the secondary particles of 15 to 40 mu m and a compressive strength of 5 to 50 MPa are mixed so that the Li / Co molar ratio in terms of atomic ratio is 0.900 to 1.040, A raw material mixing step of obtaining a raw material mixture of cobalt oxide and a lithium compound,
Wherein the raw material mixture is heated at 800 to 1150 占 폚 to react lithium cobalt hydroxide or cobalt oxide with a lithium compound to obtain lithium cobaltate and the average primary particle diameter of the cobalt hydroxide or cobalt oxide is 1.5 Wherein the lithium cobaltate is in the form of a plate, a column, The method according to claim 1,
(M) (one or more metal atoms selected from transition metal atoms other than Co and atoms having an atomic number of 9 or more) in the raw material mixing step By weight based on the total weight of the lithium cobalt oxide. 3. The method of claim 2,
Wherein the compound having the metal atom (M) is at least one selected from a compound having at least a magnesium atom and a compound having a titanium atom. The method of claim 3,
Wherein the compound having a magnesium atom is magnesium fluoride. The method of claim 3,
Wherein the compound having a titanium atom is titanium oxide (TiO ₂ ). delete delete delete delete delete delete delete delete

Images