JPH11162466A - Manufacture of positive electrode active material for lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a positive electrode active material capable of obtaining a high-capacity and high-voltage lithium secondary battery. SOLUTION: A mixture of first oxide powder expressed by the composition formula LiANiPCoQMnRO2 , (where 0.9<=A<=1.1, 0.5<P<=1.0, 0<=Q<0.5. 0<=R<=0.3, P+Q+R=1), and second oxide powder expressed by the composition formula LiBNiSCoTMnUO2 , (where 0.9<=B<=1.1, 0<=S<0.5, 0.5<T<=1.0, 0<=U<=0.3, S+T+U=1), is baked to manufacture a sintered body. The sintered body is pulverized to manufacture a positive electrode active material constituted of first active material powder and second active material powder stuck with a third oxide expressed by the composition formula LiCNiXCoYMnZO2 , (where 0.9<=C<=1.1, S<X<P, Q<Y<T, 0<=Z<=0.3, X+Y+Z=1), to the grain surfaces of the first oxide powder and the second oxide powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a positive electrode active material for a lithium secondary battery.

[0002]

2. Description of the Related Art In recent years,
Since lithium secondary batteries do not need to consider the decomposition voltage of water, it is possible to increase the voltage and capacity by appropriately selecting the positive electrode active material. , Is attracting attention as its driving power supply.

[0003] As a positive electrode active material for a lithium secondary battery,
Although LiCoO ₂ is well known, a lithium secondary battery using LiCoO ₂ has a large decrease in capacity in a charge / discharge cycle. As an improvement over this disadvantage of LiCoO ₂ , Li _x (Co _1-y Ni _y ) O ₂ (x is 0 to 1,
It is known that y is 0.1 to 0.4.
No. 11565). However, the present inventors have studied and found that when this positive electrode active material is used, the charge / discharge cycle characteristics are improved, but the discharge capacity is significantly reduced.

Further, a lithium secondary battery using LiCoO ₂ has a small capacity when charged and discharged in a voltage range of 4 V or less where decomposition of an electrolyte does not easily occur. As an improvement over this disadvantage of LiCoO ₂ , Li _x (Co _1-y N
i _y ) O ₂ (x is 0 to 1 and y is 0.5 to 0.9) is known (see JP-A-1-294364). However, when this positive electrode active material is used, the capacity is increased, but the discharge voltage is greatly reduced.

Accordingly, an object of the present invention is to provide a method for producing a positive electrode active material which enables to obtain a high capacity and high voltage lithium secondary battery.

[0006]

Production method (the method of the present invention) of the positive electrode active material for a lithium secondary battery according to SUMMARY OF THE INVENTION The present invention is a composition formula _{Li A Ni P Co Q Mn R} O 2 (0.9 ≦ A ≦ 1.
1, 0.5 <P ≦ 1.0, 0 ≦ Q <0.5, 0 ≦ R ≦
0.3, P + Q + R = 1) and a composition formula of Li _B Ni _S Co _T Mn _U O ₂ (0.9 ≦ B)
≦ 1.1, 0 ≦ S <0.5, 0.5 <T ≦ 1.0, 0 ≦
Step 1 of sintering a mixture with the second oxide powder represented by U ≦ 0.3, S + T + U = 1) to produce a sintered body
And the sintered body is pulverized, and the composition formula Li _C Ni _X Co _Y Mn _Z O is applied to the surface of each of the first oxide powder and the second oxide powder.
₂ (0.9 ≦ C ≦ 1.1, S <X <P, Q <Y <T, 0
≦ Z ≦ 0.3, X + Y + Z = 1) a step 2 of preparing a positive electrode active material comprising a first active material powder and a second active material powder to which a third oxide is attached.

In order to obtain a positive electrode active material capable of obtaining a high capacity and high voltage lithium secondary battery, step 1
As for the mixture of the first oxide powder and the second oxide powder in the above, it is preferable to use a mixture having a weight ratio of 10:90 to 90:10, and the second oxide powder has an average particle diameter of the first oxide. It is preferable to use a powder having an average particle diameter of 1/10 to 1/2 of the average particle diameter.

According to the method of the present invention, a positive electrode active material capable of obtaining a high capacity and high voltage lithium secondary battery can be manufactured. It is presumed that the third oxide (sintered portion) adhered to each particle surface of the first oxide powder and the second oxide powder contributes to higher capacity and higher voltage.

[0009]

EXAMPLES The present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples and can be carried out by appropriately changing the scope of the invention without changing its gist. It is something.

(Example 1) Composition formula L having an average particle size of 50 µm
a first oxide powder represented by iNi _0.8 Co _0.15 Mn _0.05 O ₂ and a composition formula LiNi _0.3 Co having an average particle size of 50 μm
_A second oxide powder represented by _0.6 Mn _0.1 O ₂ is mixed at a weight ratio of 1: 1 and fired in air at 800 ° C. for 8 hours to produce a sintered body, which is mechanically pulverized. Then, the composition formula LiNi _0.5 Co _0.4 Mn _0.1 O is added to the surface of the particles of the first oxide powder.
_A first active material powder to which a third oxide represented by ₂ adheres;
A positive electrode active material comprising the second active material powder having the third oxide adhered to the particle surface of the second oxide powder was produced.

Example 2 Formula L having an average particle size of 50 μm
a first oxide powder represented by iNi _0.7 Co _0.3 O ₂ ,
Composition formula LiNi _0.1 Co _0.7 Mn with an average particle size of 50 μm
_A second oxide powder represented by _0.2 O ₂ and a weight ratio of 1: 1
And sintered in air at 800 ° C. for 8 hours to produce a sintered body, mechanically pulverized, and a composition formula LiNi _0.4 Co _0.5 Mn _0.1 O _{2 on the} surface of the particles of the first oxide powder. A positive electrode active material composed of the first active material powder having the third oxide adhered thereto and the second active material powder having the third oxide adhered to the particle surface of the second oxide powder was produced.

Example 3 Formula L having an average particle size of 50 μm
a first oxide powder represented by iNi _0.7 Co _0.25 Mn _0.05 O ₂ and a composition formula LiCo _0.9 Mn having an average particle size of 50 μm
_A second oxide powder represented by _0.1 O ₂ with a weight ratio of 1: 1
And sintered in air at 800 ° C. for 8 hours to produce a sintered body, mechanically pulverized, and the composition formula LiNi _0.4 Co _0.55 Mn _0.05 O _{2 on the} surface of the particles of the first oxide powder. A positive electrode active material composed of the first active material powder having the third oxide adhered thereto and the second active material powder having the third oxide adhered to the particle surface of the second oxide powder was produced.

Example 4 Formula L having an average particle size of 50 μm
a first oxide powder represented by iNi _0.75 Co _0.2 Mn _0.05 O ₂ and a composition formula LiNi _0.3 Co having an average particle size of 50 μm
_A second oxide powder represented by _0.7 O ₂ was mixed with a weight ratio of 1: 1.
And sintered in air at 800 ° C. for 8 hours to produce a sintered body, mechanically pulverized, and a composition formula LiNi _0.5 Co _0.45 Mn _0.05 O _{2 on the} surface of the particles of the first oxide powder. A positive electrode active material composed of the first active material powder having the third oxide adhered thereto and the second active material powder having the third oxide adhered to the particle surface of the second oxide powder was produced.

(Example 5) Composition formula L having an average particle size of 50 μm
a first oxide powder represented by iNi _0.8 Mn _0.2 O ₂ ,
Composition formula LiNi _0.1 Co _0.8 Mn with an average particle size of 50 μm
_A second oxide powder represented by _0.1 O ₂ with a weight ratio of 1: 1
And sintered in air at 800 ° C. for 8 hours to produce a sintered body, mechanically pulverized, and the composition formula LiNi _0.45 Co _0.4 Mn _0.15 O _{2 on the} surface of the particles of the first oxide powder. A positive electrode active material composed of the first active material powder having the third oxide adhered thereto and the second active material powder having the third oxide adhered to the particle surface of the second oxide powder was produced.

NMP (N-methyl-2-pyrrolidone) solution of 90 parts by weight of each positive electrode active material, 5 parts by weight of artificial graphite as a conductive agent, and 5 parts by weight of polyvinylidene fluoride as a binder was used. A slurry was prepared by kneading, and this slurry was applied to both surfaces of an aluminum foil as a positive electrode current collector by a doctor blade method, and dried at 150 ° C. for 2 hours to produce a positive electrode. Also, 95 parts by weight of natural graphite,
NMP of 5 parts by weight of polyvinylidene fluoride as a binder
The solution was kneaded to prepare a slurry, and this slurry was applied to both surfaces of a copper foil as a negative electrode current collector by a doctor blade method, and dried at 150 ° C. for 2 hours to prepare a negative electrode. Further, LiPF ₆ was added to a mixed solvent of ethylene carbonate and diethyl carbonate at a volume ratio of 1: 1 with 1 mol / mol.
One liter was dissolved to prepare an electrolytic solution. Using the positive electrode, the negative electrode, and the electrolytic solution, lithium secondary batteries A1 to A5 of AA size were produced. Batteries A1 to A5 are batteries using the respective positive electrode active materials prepared in Examples 1 to 5 in order.
For comparison, Examples 1 to 5 were used as positive electrode active materials.
A mixture of the first oxide powder and the second oxide powder used in
The first oxide powder used in Example 1 (LiNi _0.8 Co
_0.15 Mn _0.05 O ₂ ) or the second oxide powder (LiNi _0.3 Co _0.6 Mn _0.1 O ₂ ) used in Example 1 was used in the same manner as above, except that the lithium secondary battery B was used.
Nos. 1 to B7 were prepared.

<Discharge capacity and discharge voltage of each battery> After charging each battery to 4.2 V at 200 mA,
Six cycles of charging / discharging at 0 mA to 2.75 V were performed, and the discharge capacity (mAh) at the sixth cycle of each battery was determined. Further, the discharge voltage (V) of each battery was determined from the discharge curve at the sixth cycle. Table 1 shows the results.

[0017]

[Table 1]

As shown in Table 1, batteries A1 to A5 have a large discharge capacity and a high discharge voltage, while battery B6 has a large discharge capacity but a low discharge voltage, and battery B7 has a high discharge capacity. The discharge voltage is high, but the discharge capacity is small. Also,
Batteries B1 to B5 are compared with batteries A1 to A5, respectively.
Low discharge capacity and low discharge voltage.

[Relationship between weight ratio of first oxide powder and second oxide powder, discharge capacity and discharge voltage] First oxide powder (LiNi _0.8 Co _0.15 Mn _0.05 O ₂ ) and second oxide powder (LiNi _0.8 Co _0.15 Mn _0.05 O ₂ ) LiNi _0.3 Co _0.6 Mn _0.1 O ₂ ) in a weight ratio of 95: 5, 90:10, 70:30, 30:70, 1
Except for mixing at 0:90 or 5:95, six kinds of positive electrode active materials were prepared in the same manner as in Example 1, and lithium secondary batteries C1 to C6 were sequentially formed using these positive electrode active materials. The batteries were manufactured and subjected to the same test as above to determine the discharge capacity and discharge voltage at the sixth cycle of each battery. Table 2 shows the results.
Table 2 shows the batteries A1, B6, B7 for convenience of comparison.
Are also transcribed from Table 1.

[0020]

[Table 2]

From Table 2, it can be seen that a mixture of the first oxide powder and the second oxide powder in Step 1 was used to produce a positive electrode active material capable of obtaining a high capacity and high voltage lithium secondary battery. It can be seen that it is preferable to use a mixture having a weight ratio of 10:90 to 90:10.

[Relationship between average particle diameter of first oxide powder and second oxide powder, discharge capacity and discharge voltage] Average particle diameter 50
μm of the first oxide powder (LiNi _0.8 Co _0.15 Mn _0.05
O ₂ ) and a second oxide powder (LiNi _0.3 Co)
_0.6 Mn _0.1 O ₂ ), each having an average particle size of 25 μm.
m, 20 μm, 10 μm, 5 μm, and 2 μm, except that five types of positive electrode active materials were prepared in the same manner as in Example 1, and these positive electrode active materials were used to sequentially form a lithium secondary battery. D1 to D5 were prepared, and the same test was performed to determine the discharge capacity and discharge voltage at the sixth cycle of each battery. Table 3 shows the results. In Table 3, the results of Battery A1 are also transcribed from Table 1 for convenience of comparison.

[0023]

[Table 3]

From Table 3, it can be seen that a mixture of the first oxide powder and the second oxide powder in Step 1 was used to produce a positive electrode active material capable of obtaining a high capacity and high voltage lithium secondary battery. It can be seen that it is preferable to use a mixture in which the average particle size of the second oxide powder is 1/10 to 1/2 of the average particle size of the first oxide powder.

[0025]

According to the present invention, there is provided a method for producing a positive electrode active material which enables a high capacity and high voltage lithium secondary battery to be obtained.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiyuki Noma 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Koji Nishio 2-chome, Keihanhondori, Moriguchi-shi, Osaka No. 5-5 in Sanyo Electric Co., Ltd.

Claims (3)

[Claims] 1. A composition formula _{Li A Ni P Co Q Mn R} O
₂ (0.9 ≦ A ≦ 1.1, 0.5 <P ≦ 1.0, 0 ≦ Q
<0.5, 0 ≦ R ≦ 0.3, P + Q + R = 1) and a composition formula of Li _B Ni _S Co _T Mn _U
O ₂ (0.9 ≦ B ≦ 1.1, 0 ≦ S <0.5, 0.5 <
T ≦ 1.0, 0 ≦ U ≦ 0.3, S + T + U = 1) Step 1 of baking a mixture with the second oxide powder to produce a sintered body, and pulverizing the sintered body The surface of each particle of the first oxide powder and the second oxide powder has the composition formula Li _C Ni _X
Co _Y Mn _Z O ₂ (0.9 ≦ C ≦ 1.1, S <X <P,
Step 2 of preparing a positive electrode active material comprising a first active material powder and a second active material powder to which a third oxide represented by Q <Y <T, 0 ≦ Z ≦ 0.3, X + Y + Z = 1) is attached. A method for producing a positive electrode active material for a lithium secondary battery, comprising: 2. A mixture in step 1 wherein the weight ratio of the first oxide powder to the second oxide powder is from 10:90 to 9: 9.
The method for producing a positive electrode active material for a lithium secondary battery according to claim 1, wherein the positive electrode active material is used at 0:10. 3. The mixture in Step 1 wherein the average particle size of the second oxide powder is 1/1 / the average particle size of the first oxide powder.
The method for producing a positive electrode active material for a lithium secondary battery according to claim 1, wherein the positive electrode active material is 10 to 1/2.