JPH1160243A - Nickel hydroxide, lithium nickelate, their production and lithium ion secondary battery using the lithium nickelate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a lithium ion secondary battery having improved heat characteristics during charging without lowering battery characteristics, nickel hydroxide and lithium nickelate and to provide for producing nickel hydroxide and lithium nickelate. SOLUTION: This nickel hydroxide is shown by the formula; Ni1-x Ax (OH)2 (A is cobalt or manganese; 0.10<x<0.5), comprises a laminate or a single crystal arranged in crystal orientation, has 0.5-5 μm primary particle diameter, full width at half maximum by X-diffraction by sampling to orientate most of (001)<0.3 deg., (101)<0.4 deg. and the peak intensity ratio of I(101)/I(001)<0.5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to nickel hydroxide, lithium nickelate and a method for producing the same, and a lithium ion secondary battery using lithium nickelate fired from the nickel hydroxide as a raw material. In addition, the nickel hydroxide in the present invention includes those in which a part of nickel is replaced by cobalt or manganese. Further, the lithium nickelate referred to in the present invention also includes those in which a part of nickel is replaced by cobalt or manganese.

[0002]

2. Description of the Related Art With the rapid progress of portable and cordless telephones and personal computers in recent years, a demand for a secondary battery as a power source for driving them is increasing. Among them, a lithium ion secondary battery having a small size, light weight and high energy density is particularly expected. Lithium is desorbed as a positive electrode active material (positive electrode material) for lithium ion secondary batteries satisfying the above demands,
Research on lithium composite oxides such as lithium cobalt oxide (LiCoO ₂ ) and lithium nickel oxide (LiNiO ₂ ) that can be inserted has been actively conducted. These lithium composite oxides have a potential of 4 V or more with respect to lithium, and when used as a positive electrode material, a discharge capacity of 150 mAh / g or more can be obtained. Therefore, the realization of a secondary battery having a high energy density was expected. .

In recent years, however, higher discharge capacities have been expected for lithium ion secondary batteries. In addition, inexpensive cathode materials are required from the viewpoint of economy.

[0004] As a positive electrode material that meets such demands, L
iNi _1-x Co _x O ₂ (x> 0) has been proposed. A lithium ion secondary battery using LiNi _1-x Co _x O ₂ (x> 0) has a higher capacity than a conventional lithium ion secondary battery using LiCoO ₂ , and is rich in raw materials and inexpensive. Therefore, it is promising as the next positive electrode material.

However, this LiNi_1-xCo_xO
_Two(X> 0) as a positive electrode material
Secondary batteries have poor thermal stability in the charged state, which is a major problem
It has become. This is because lithium deintercalates on charging.
As the rate increases, the structure becomes unstable and the surrounding temperature rises.
The structure collapses and reacts with the organic electrolyte, generating heat and igniting
Happens to do. Thus, LiNi_1-xCo_xO
_Two(X> 0) is LiCoO _TwoHeat generation at lower temperature
Response to the battery, there is a problem with the safety of the battery.
Good is strongly sought.

One of the improvements in the thermal characteristics is suppression of a thermal decomposition reaction due to a decrease in specific surface area. That is, an object of the present invention is to reduce the contact area between the positive electrode material and the organic electrolyte to suppress the exothermic reaction rate and increase the exothermic onset temperature. This requires an increase in primary particles, specifically Li
It is considered necessary to obtain a positive electrode material having Ni _1-x Co _x O ₂ (x> 0) primary particles of 2 μm or more.

LiNi _1-x Co _x O ₂ (x> 0) is generally Ni (OH) ₂ , Co (OH) ₂ or (Ni, Co)
Using fine or spherical powder of (OH) ₂ as a raw material, LiO
It is obtained by mixing with H powder and firing. Since these hydroxides are aggregates in which primary particles are less than 0.5 μm,
It is necessary to increase the primary particles by sintering during firing. However, in this method, the discharge capacity is greatly reduced due to aggregation of the particles, and the required powder characteristics and battery characteristics cannot be compatible. Therefore, it is necessary to sinter the positive electrode material in which the primary particles are increased without deteriorating the battery characteristics, and to improve the thermal characteristics during charging of the battery.

Accordingly, it is an object of the present invention to provide a lithium ion secondary battery having improved thermal characteristics during charging without deteriorating battery characteristics, nickel hydroxide, nickel lithium oxide, which is a raw material for a positive electrode material of the battery, and An object is to provide these manufacturing methods.

[0009]

Means for Solving the Problems As a result of diligent studies, the present inventors have found that primary particles of nickel hydroxide used as a raw material of a positive electrode active material of a lithium ion secondary battery are increased in sintering during firing. It has been found that the above object can be achieved by achieving the above at the raw material stage.

The present invention has been made based on the above findings, and has the following compositional formula (1): Ni _1-x A _x (OH) ₂ (1) (A is cobalt or manganese, 0.10 <x <0 .5)
And has a primary particle size of 0.5 to 5 μm and a full width at half maximum by X-ray diffraction obtained by sampling which is most easily oriented (001) < 0.3 deg. , (101) <0.4d
eg. And the peak intensity ratio I (101) / I (001)
The present invention provides nickel hydroxide characterized by being <0.5.

The present invention also relates to a preferred method for producing the nickel hydroxide of the present invention, wherein a mixed aqueous solution comprising an aqueous solution of nickel nitrate, an aqueous solution of cobalt nitrate or manganese nitrate, and an aqueous solution of ammonia is used at 60 to 90 ° C. for 3 hours or more. The mixture is stirred under stirring, and then the mixture is boiled while dropping an aqueous alkaline solution to maintain the mixed aqueous solution at a pH of 6.6 to 7.5, and then aged in an aqueous alkaline solution for at least 8 hours. A method for producing nickel is provided.

Further, the present invention provides a composition of the following formula (2): LiNi _1-x A _x O ₂ (2) (A is cobalt or manganese, 0.10 <x <0.5)
Where the primary particle diameter is 0.5 to 5 μm, and the peak intensity ratio I (101) / I (001) <0.4 by X-ray diffraction obtained by sampling which is most easily oriented. A feature of the present invention is to provide lithium nickelate.

Further, the present invention provides a lithium ion secondary battery characterized in that the above-mentioned nickel hydroxide is mixed with a lithium compound, and the above-mentioned lithium nickel oxide obtained by calcining the mixture is used as a positive electrode active material. To provide.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The nickel hydroxide of the present invention is represented by the following composition formula (1): Ni _1-x A _x (OH) ₂ (1) In the above composition formula, A is cobalt or manganese, preferably cobalt. X is more than 0.10 and less than 0.5. When x is 0.1 or less, the effect of the added element is not sufficiently obtained, and when x is 0.5 or more, the capacity is remarkably reduced.

The nickel hydroxide is composed of a laminate or a single crystal having a uniform crystal orientation, and has a primary particle diameter of 0.5.
５5 μm. If the primary particle size is less than 0.5 μm, the specific surface area is too large, lacks sufficient thermal stability, and
If the ratio exceeds, it is difficult to completely react the inside of the particles at the time of firing.

Further, the full width at half maximum by X-ray diffraction obtained by sampling the most easily oriented nickel hydroxide of the present invention is (001) <0.3 deg. , (101) <
0.4 deg. And peak intensity ratio I (101) / I
It is necessary that (001) <0.5, and if it is out of this range, the orientation of the crystallographic orientation or the size of the grain boundary regarded as a single crystal becomes insufficient, which is not preferable.

FIG. 1 shows a scanning electron microscope (SEM) photograph (× 5000) of the nickel hydroxide of the present invention. Also,
For comparison, FIG. 2 shows a scanning electron micrograph (× 10000) of a conventional powdery nickel hydroxide, and FIG. 3 shows a scanning electron micrograph (× 10000) of a spherical nickel hydroxide.
Are shown below. FIG. 4 shows an X-ray diffraction diagram of the nickel hydroxide of the present invention.

As is clear from FIG. 1, the nickel hydroxide of the present invention is a laminate or a single crystal having a uniform crystal orientation. In addition, as is clear from the comparison between FIG. 1 and FIGS. 2 to 3, it is understood that the nickel hydroxide of the present invention has a larger primary particle diameter than the fine powder or spherical nickel hydroxide.

The above-described nickel hydroxide of the present invention is produced by the following method. First, using an aqueous solution of nickel nitrate, an aqueous solution of cobalt nitrate or manganese nitrate, and an aqueous solution containing ammonia, the mixed aqueous solution
C., preferably at 75-85.degree. C., with stirring for 3 hours or more. In this case, the molar ratio of ammonia / (nickel + cobalt or manganese) is 3 to 4. The concentration of nickel nitrate + cobalt nitrate or manganese nitrate aqueous solution is
It is 0.5 to 2.0 mol / l. The ammonia-containing aqueous solution is an aqueous solution that can supply ammonium ions, and examples thereof include an aqueous ammonia solution, ammonium nitrate, ammonium carbonate, ammonium chloride, and urea.

When the mixing temperature is lower than 60 ° C. or higher than 90 ° C.,
If the desired particle size cannot be obtained, and if the mixing time is less than 3 hours, fine powder having a particle size of 0.5 μm or less is generated, which is not preferable.

Next, an aqueous alkaline solution, for example, sodium hydroxide is dropped into the aqueous mixed solution while boiling,
Remove the ammonia. At this time, the mixed aqueous solution is p
It is necessary to maintain H between 6.6 and 7.5,
Is out of this range, a fine powder having a particle size of 0.5 μm or less is generated, which is not desirable.

Then, in an alkaline aqueous solution at 60 to 90 ° C.
For at least 8 hours to remove impurities. If the aging temperature exceeds the above range, it is difficult to maintain the amount of the solution, and if the aging temperature is below the above range, it takes a long time to remove impurities. If the aging time is less than 8 hours, the removal of impurities will be insufficient. It is desirable that the concentration of the alkaline aqueous solution is around 1.0 mol / l.

Finally, washing with pure water, filtration and drying are carried out under ordinary conditions and methods to obtain nickel hydroxide having the above-mentioned properties and properties. The conditions of washing with pure water, filtration, and drying are, for example, washing with pure water in an amount of 5 times, suction filtration, and vacuum drying at 60 to 100 ° C for 8 hours or more.

The nickel hydroxide of the present invention is mixed with a lithium compound serving as a lithium source such as lithium carbonate, lithium hydroxide and lithium oxide, and calcined to form lithium nickel oxide. As the lithium compound serving as the lithium source, lithium hydroxide monohydrate is suitably used. At this time, the mixing ratio (molar ratio) between nickel hydroxide and, for example, lithium hydroxide needs to be 1: 1.0 to 1: 1.1. The firing conditions are as follows:
700-850 ° C, 12-40 hours.

The nickel lithium oxide of the present invention has the following composition formula (2) LiNi _1-x A _x O ₂ (2) (A is cobalt or manganese, 0.10 <x <0.5)
Where the primary particle diameter is 0.5 to 5 μm, and the peak intensity ratio I (101) / I (001) <0.4 by X-ray diffraction obtained by sampling which is most easily oriented. Features.

The lithium nickelate of the present invention has a primary particle size of 0.5 to 5 μm. 0.5μ primary particle size
When the particle size is less than m, the aggregation of the particles becomes too large to be neglected and the powder characteristics are deteriorated.

The lithium nickelate has a peak intensity ratio I (101) / I (001) <0.4 according to an X-ray diffraction diagram obtained by sampling which is most easily oriented. If the ratio is out of this range, the orientation of the crystal orientation of the stacked body or the size of the grain boundary regarded as a single crystal becomes insufficient, which is not preferable.

The lithium nickelate of the present invention (LiNi
_1-x Co _x O ₂ (x> 0)) scanning electron microscope (SE
M) A photograph (× 5000) is shown in FIG. For comparison, FIG. 6 shows a scanning electron micrograph (× 10000) of lithium nickelate (LiNi _1-x Co _x O ₂ (x> 0)) obtained by using conventional finely powdered nickel hydroxide. FIG. 7 shows scanning electron micrographs (× 10000) of lithium nickelate (LiNi _1-x Co _x O ₂ (x> 0)) obtained using spherical nickel hydroxide. FIG. 8 shows an X-ray diffraction diagram of the lithium nickelate of the present invention.

In the present invention, this lithium nickelate is used as a positive electrode active material of a lithium ion secondary battery. The thus obtained lithium ion secondary battery can improve the thermal characteristics during charging without deteriorating the battery characteristics.

[0030]

EXAMPLES Hereinafter, the present invention will be specifically described based on examples and the like.

Example 1 An aqueous solution of 85% nickel nitrate, 15% cobalt nitrate and an aqueous ammonia solution were mixed with stirring at 80 ° C. for 3 hours or more.
At this time, the molar ratio of ammonia / (nickel + cobalt) is 3. The concentration of the aqueous solution of nickel nitrate + the aqueous solution of cobalt nitrate was 1.7 mol / l.

Next, 1.0 mol / l sodium hydroxide was added dropwise to the mixed aqueous solution and the mixture was boiled to remove ammonia. In this case, the pH of the mixed aqueous solution is 6.
It was maintained in the range of 9-7.2. Then, a concentration of 1 mol /
The solution was aged at 80 ° C. for 8 hours or more in 1 l of an aqueous sodium hydroxide solution to remove impurities.

Finally, washing with pure water, filtration, and drying
_A nickel hydroxide having a composition of _0.85 Co _0.15 (OH) ₂ was obtained. The conditions of washing with pure water, filtration, and drying were as follows: washing with 5 times the amount of pure water, suction filtration, and vacuum drying at 70 ° C. for 12 hours. The nickel hydroxide thus obtained had a particle structure as shown in FIG. The primary particle diameter was 2 μm, full width at half maximum (001) = 0.18 deg. ,
(101) = 0.32 deg. , Peak intensity ratio I (10
1) / I (001) = 0.39.

A mixture of nickel hydroxide having the above composition and lithium hydroxide monohydrate was mixed in an oxygen atmosphere at 750.
C. for 20 hours to obtain lithium nickelate having a composition of Li (Ni _0.85 Co _0.15 ) O ₂ . At this time, the mixing ratio (molar ratio) of nickel hydroxide and lithium hydroxide monohydrate was 1: 1.05. The thus obtained lithium nickelate had a particle structure as shown in FIG. The primary particle diameter was 2 μm, and the peak intensity ratio I (101) / I (001) = 0.198.

Using this lithium nickelate as a positive electrode material (positive electrode active material), a positive electrode material: acetylene black:
The mixture was mixed so as to have a weight ratio of Teflon binder = 0.85: 0.1: 0.03, and preliminarily dried at 120 ° C. for 2 hours. From this, 0.05 g was weighed and molded into a disk having a diameter of 1 cm by applying a uniaxial pressure of 3 t.
After drying for a time, pellets for the positive electrode were obtained.

The pellet was assembled in a model cell as shown in FIG. For the negative electrode, metallic lithium with a diameter of 1 cm,
As the electrolytic solution, a 1 mol / l solution of lithium boron tetrafluoride (LiBF ₄ ) using a 1: 1 mixture of propylene carbonate and dimethyl ether as a solvent was used. In the figure, 1 is a negative electrode terminal, 2 is an insulator (Teflon material),
3 is a negative electrode current collector plate, 4 is a negative electrode material, 5 is a separator, 6
Denotes a positive electrode pellet, and 7 denotes a positive electrode terminal. The battery test was charged at 0.441 mA to 4.3 V and 0.882
Discharged to 3.0 V at mA. The opening time was 10 minutes.

Differential thermal analysis of the positive electrode in the charged state was performed on this test cell, and the results are shown in FIG. This differential thermal analysis was performed using a sample which was charged to a positive voltage of 4.3 V and washed with dimethyl ether. FIG. 11 shows the charge / discharge characteristics of this cell.

(Comparative Example 1) Except that a fine powdered nickel hydroxide as shown in FIG. 2 was used as the nickel hydroxide,
In the same manner as in Example 1, Li (N
A lithium nickelate having a composition of i _0.85 Co _0.15 ) O ₂ was obtained. This lithium nickelate was used as a positive electrode material (positive electrode active material), and was incorporated in a Sest Tecell in the same manner as in Example 1. This test cell was subjected to differential thermal analysis of the positive electrode in the charged state in the same manner as in Example 1, and the results are shown in FIG. FIG. 12 shows the charge / discharge characteristics of this cell.

As shown in FIG. 10, the peak value of the differential thermal analysis of Example 1 is higher than that of Comparative Example 1, indicating that the thermal characteristics are superior. Also, from a comparison between FIG. 11 and FIG. 12, it can be seen that Example 1 has better charge / discharge characteristics than Comparative Example 1 and is superior in battery performance.

【The invention's effect】

As described above, by using the nickel hydroxide of the present invention as a raw material for the positive electrode active material, a lithium ion secondary battery having improved thermal characteristics during charging without lowering battery characteristics can be obtained. . In addition, the production method of the present invention allows the above-mentioned nickel hydroxide to be obtained simply and in high yield.

[Brief description of the drawings]

FIG. 1 is a scanning electron micrograph (× 5000) showing the particle structure of nickel hydroxide of the present invention.

FIG. 2 is a scanning electron micrograph (× 10000) showing the particle structure of finely divided nickel hydroxide.

FIG. 3 is a scanning electron micrograph (× 10000) showing the particle structure of spherical nickel hydroxide.

FIG. 4 shows the nickel hydroxide (Ni _1-x Co _x (O
H) X-ray diffraction diagram of ₂ ).

FIG. 5 shows a lithium nickelate (LiNi _1-x C) of the present invention.
_{o x O 2 (x> 0} )) scanning electron microscope photograph showing the particle structure of the (× 5000).

FIG. 6 Lithium nickelate (LiNi _{1 -x} Co _x O ₂ (x> 0)) obtained using finely divided nickel hydroxide
Scanning electron micrograph (× 1000) showing the particle structure of
0).

FIG. 7 is a scanning electron micrograph (× 1000) showing the particle structure of lithium nickelate (LiNi _1-x Co _x O ₂ (x> 0)) obtained using spherical nickel hydroxide.
0).

FIG. 8 shows a lithium nickelate (LiNi _1-x C) of the present invention.
o _x O _{2 X-ray} diffraction pattern of the (x> 0)).

FIG. 9 is a schematic sectional view of a test cell used in Examples and Comparative Examples.

FIG. 10 is a differential thermal analysis diagram of a positive electrode in a charged state of Example 1 and Comparative Example 1.

FIG. 11 is a charge / discharge graph of the cell of Example 1.

FIG. 12 is a charge / discharge graph of the cell of Comparative Example 1.

[Explanation of symbols]

1: negative electrode terminal, 2: insulator (Teflon material), 3: negative electrode current collector plate, 4: negative electrode material, 5: separator, 6: positive electrode pellet, 7: positive electrode terminal.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01M 10/40 H01M 10/40 Z

Claims (5)

[Claims] 1. The following composition formula (1): Ni _1-x A _x (OH) ₂ (1) (A is cobalt or manganese, 0.10 <x <0.5)
And has a primary particle size of 0.5 to 5 μm and a full width at half maximum by X-ray diffraction obtained by sampling which is most easily oriented (001) < 0.3 deg. , (101) <0.4d
eg. And the peak intensity ratio I (101) / I (001)
Nickel hydroxide characterized by being <0.5. 2. A mixed aqueous solution composed of an aqueous solution of nickel nitrate, an aqueous solution of cobalt nitrate or manganese nitrate, and an aqueous solution of ammonia are mixed under stirring at 60 to 90 ° C. for 3 hours or more, and then the aqueous solution is boiled while adding an aqueous alkaline solution dropwise. A method for producing nickel hydroxide, comprising maintaining the mixed aqueous solution at a pH of 6.6 to 7.5 and then aging the aqueous solution in an alkaline aqueous solution for 8 hours or more. 3. The following composition formula (2): LiNi _1-x A _x O ₂ (2) (A is cobalt or manganese, 0.10 <x <0.5)
Where the primary particle diameter is 0.5 to 5 μm, and the peak intensity ratio I (101) / I (001) <0.4 by X-ray diffraction obtained by sampling which is most easily oriented. Features lithium nickelate. 4. A method for producing lithium nickel oxide, comprising firing a mixture of the nickel hydroxide according to claim 1 and a lithium compound. 5. A lithium ion secondary battery using the lithium nickelate according to claim 3 as a positive electrode active material.