JPH0950810A - Electrode active material for non-aqueous electrolytic battery and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remarkably increase the discharge capacity of a battery in an initial stage and after 50 cycles by coating the surface of a specified lithium- nickel mixed oxide with a lithium-transition metal M mixed oxide. SOLUTION: To produce an electrode active material; compounds of transition metals M (M stands for Co, Mn, and/or Fe including metals partly containing Ni) and a lithium compound are dissolved or suspended in a solvent, a lithium- nickel mixed oxide having a general formula Lix Niy Nz O2 (N stands for elements except Li, Ni, and 0; 0.8<z<1.2; 0.8<y +z<1.2; 0<=z<0.2) is further added to give a slurry, and the slurry is dried and fired. The obtained electrode active material has high standing stability and even if left in atmosphere containing moisture, the material does not lower the capacity of a battery in the case the material is dried and then the battery is assembled using the material. Moreover, without causing trouble such as heat generation, the material keeps excellent safety and can be used for both cathode and anode.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electrode active material for a non-aqueous electrolyte battery of a secondary battery.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for portable devices such as portable telephones, laptop personal computers, camera-integrated VTRs, and the like. For these devices, small and lightweight secondary batteries are indispensable. At present, as a secondary battery, Ni-C
Although d batteries and Ni hydrogen batteries are used, these batteries have reached the limit of miniaturization and weight reduction.

On the other hand, development of non-aqueous electrolyte secondary batteries using metallic lithium or a substance capable of occluding / desorbing lithium for the negative electrode has been promoted. This battery is characterized by a higher voltage and a higher energy density than conventional small secondary batteries, and can be made smaller and lighter than conventional batteries.

The electrodes of this battery are generally made of LiCoO 2.
₂ is used, but Co has a problem that it is expensive and has a small reserve. Therefore, lithium-nickel composite oxide such as LiNiO ₂ is cheaper than LiCoO ₂ and has a high charge / discharge capacity. Has attracted attention as a new electrode active material and is being researched.

A method for synthesizing a lithium-nickel composite oxide is described in J. Am. Chem. Soc. 76, 1499 (195
4), U.S. Pat. No. 4,302,518 and the like, and is generally obtained by mixing a lithium compound and a nickel compound and firing at 500 to 900 ° C. in an oxygen atmosphere.

Further, recently, LiNi _{1- t} N _t O ₂ (N is L is obtained by substituting a part of Ni of LiNiO ₂ with another element).
It has been clarified that the cell performance of elements other than i, Ni, and O, 0 <t ≦ 0.5) is excellent. For example, in the embodiment of Japanese Patent Laid-Open No. 6-215800, N is A
It is described that 1, 1, Ga, B, Sc, Fe, Cr, Mn, Ti, etc. are used, and that the battery using this electrode active material has excellent charge / discharge energy and storage characteristics.

[0007]

LiNiO ₂ is expensive,
Although it is an excellent material in terms of charge / discharge capacity, it has a problem that it is less stable in storage, particularly in stability to moisture, as compared with LiCoO ₂ . When LiNiO ₂ is used in the form of fine powder as an electrode active material, it has a large specific surface area and is particularly susceptible to moisture. For example, when a battery is assembled using LiNiO ₂ that has been placed in air with high humidity after crushing, there is a problem that the initial discharge capacity decreases, or the discharge capacity decreases significantly when charging and discharging are repeated. ,
Occasionally, a serious safety problem such as heat generation inside the battery occurred.

[0008]

In order to solve the above-mentioned problems of the present invention, as a result of extensive studies, the general formula Li _x Ni _y N
_z O ₂ (N is an element other than Li, Ni and O, 0.8 <x <
The surface of the lithium-nickel composite oxide represented by 1.2, 0.8 <y + z <1.2, 0 ≦ z <0.2) is replaced with a lithium-transition metal M composite oxide (M is Co, Mn, It was solved by coating with one or more kinds of Fe (including those containing a part of Ni).

That is, the present invention has the general formula Li _x Ni _y N _z
O ₂ (N is an element other than Li, Ni and O, 0.8 <x <
The surface of the lithium-nickel composite oxide represented by 1.2, 0.8 <y + z <1.2, 0 ≦ z <0.2) is replaced with a lithium-transition metal M composite oxide (M is Co, Mn, An electrode active material for a non-aqueous electrolyte battery, a transition metal M (M is one or more of Co, Mn, and Fe), characterized by being coated with one or more of Fe, including one that partially contains Ni. And a lithium compound are dissolved or suspended in a solvent to obtain a compound represented by the general formula Li _x N
i _y N _z O ₂ (N is an element other than Li, Ni and O, 0.8
<X <1.2, 0.8 <y + z <1.2, 0 ≦ z <0.
The present invention relates to a method for producing an electrode active material for a non-aqueous electrolyte battery, which comprises adding the lithium-nickel composite oxide represented by 2) to form a slurry, and drying and firing the slurry.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The general formula Li _x Ni _y N _z O ₂ (N
Is an element other than Li, Ni, O, 0.8 <x <1.2,
The lithium-nickel composite oxide represented by 0.8 <y + z <1.2, 0 ≦ z <0.2) may be obtained by a known synthesis method, but in an atmosphere with a large amount of water. It is necessary that it sufficiently acts as an electrode active material when incorporated into a battery as an electrode active material without being exposed to. The contained element N is not particularly limited.

Examples of the lithium-nickel composite oxide used in the present invention include LiNiO ₂ and LiNi _0.9 C.
o _0.1 O ₂ , LiNi _0.9 AI _0.1 O ₂ , LiN
i _{0 . 9} Mn _0.1 O _{2 and the} like. Any shape may be used, but a shape close to a sphere is particularly preferable.

Further, it is preferable that the lithium-transition metal M composite oxide formed on the surface itself acts as an electrode active material. Specific examples thereof include a lithium-cobalt composite oxide, a lithium-manganese composite oxide, and a lithium-cobalt composite oxide partially containing nickel. Examples of the compound of the transition metal M and the lithium compound include nitrates, carbonates, acetates, hydroxides, oxides, peroxides and metals. It is preferable that these are dissolved or suspended in the solvent used. As a solvent used for the compound of the transition metal M and the lithium compound, water or an organic solvent such as alcohol or benzene, or a solvent that can be used for a lithium ion battery organic electrolyte such as propylene carbonate can be used.

The drying temperature is appropriately selected depending on the boiling point of the solvent and the like. When water is used, for example, a temperature of 90 ° C. or higher is preferable in order to completely remove water. The drying method is not particularly limited, but a spray drying method such as a spray dryer is preferably used because the compound to be surface-coated is uniformly dispersed on the lithium-nickel composite oxide particles.

The calcination temperature is preferably a calcination temperature suitable for synthesizing the coating material as an electrode active material, and a calcination temperature that does not change the basic structure of the lithium-nickel composite oxide. It is appropriately selected according to the balance. The firing atmosphere is preferably an oxygen-existing atmosphere that promotes oxidation, and further, firing is preferably performed while removing the decomposition product gas.

The average particle diameter of the electrode active material is less than 50 microns because the thickness of the electrode formed by applying the electrode active material to the current collector needs to be several hundreds of microns or less. It is preferable. Further, if the average particle size of the electrode active material is too small, it becomes difficult to coat the current collector and mix with the conductive material, so that the average particle size of the electrode active material is preferably more than 1 micron.

Although it is difficult to measure the thickness of the coating material on the surface of the lithium-nickel composite oxide,
It is preferable that the average thickness calculated from the average particle size of the nickel composite oxide, the addition amount of the coating material, the density, etc. be 0.001 micron or more and 5 micron or less. If the thickness of the coating exceeds 5 μm, it is not preferable because the battery performance of high capacity, which is a feature of the lithium-nickel composite oxide, cannot be obtained, and if the thickness of the coating is less than 0.001 μm, the function of the coating can be fulfilled. It is not preferable because the object of the present invention cannot be achieved. Although the synthesized electrode active material has stability against moisture, when a battery is made, if water enters the battery, a decomposition reaction of water or the like occurs, which causes a safety problem.
It is preferable to manufacture the battery after drying the electrode active material.

The above-mentioned method for producing an electrode active material for a non-aqueous electrolyte battery comprises a compound of a transition metal M (M is one or more of Co, Mn and Fe, including a portion of Ni), and A lithium compound is dissolved or suspended in a solvent to obtain a compound represented by the general formula: Li _x Ni _y N _z O ₂ (N is an element other than Li, Ni and O, 0.8 <x <1.2, 0.8 <y + z < 1.2, 0
A lithium-nickel composite oxide represented by ≦ z <0.2) is added to form a slurry, and the slurry is dried and calcined.

The lithium-transition metal M composite oxide can also be manufactured by a method of coating by directly mixing fine powder of the lithium-transition metal M composite oxide with powder of the lithium-nickel compound and firing the mixture. -Since it is not uniformly dispersed on the surface of the nickel composite oxide particles, the stability may not be improved in some cases, which is not preferable.

The electrode active material obtained by the above method is
Even if the battery is excellent in storage stability and placed in an atmosphere containing water, if the battery is assembled after drying, the capacity of the assembled battery will not be reduced. Furthermore, a product having excellent safety can be obtained without causing a problem such as heat generation. Further, the electrode active material of the non-aqueous electrolyte battery of the present invention may be used for either the positive electrode or the negative electrode.

[0020]

EXAMPLES The present invention will be described in more detail below with reference to examples. Example 1 83.9 g of lithium hydroxide monohydrate and 1 of nickel hydroxide
85.4 g (atomic ratio of lithium to nickel Li / Ni
(Mole ratio) = 1.0), weighed and mixed well with a ball mill, and dried at 150 ° C for 12 hours. After firing the dried product in an oxygen atmosphere at 750 ° C. for 5 hours,
Grind for 1 hour in a ball mill in a nitrogen atmosphere, average particle size 7
A micron lithium-nickel composite oxide was obtained. The coating process was performed by the following method. Ethanol 300
Lithium nitrate 3.4 g and cobalt nitrate hexahydrate 1 g
4.6 g (Li / Co (molar ratio) = 1.0) was dissolved,
The lithium-nickel composite oxide 92.
7 g (Co / Ni (molar ratio) = 0.05) was added and dispersed. The dispersion was dried under the condition that the outlet temperature of the spray dryer was about 100 ° C., and then baked at 700 ° C. for 1 hour in an oxygen atmosphere using an electric furnace to obtain a coated electrode active material. In order to investigate the stability of the electrode active material, the following treatment and battery performance test were performed. First, the obtained electrode active material was allowed to stand in an atmosphere having a temperature of 60 ° C. and a relative humidity of 90% for 1 hour, and then dried at 120 ° C. for 1 hour. Next, an electrode active material, acetylene black which is a conductive material, and polyfluoroethylene which is a binder are kneaded at a predetermined weight ratio,
The electrode was formed into a pellet. Metallic lithium is used for the negative electrode, and the electrolyte is 1 mol of lithium hexafluorophosphate.
A button-type battery was assembled using a mixed solution of propylene carbonate / diethyl carbonate dissolved in / L. In order to investigate the performance of this battery, charge and discharge were performed at a constant current of 0.5 mA / cm ² in a voltage range of 4.2 to 3.0 V, and the discharge capacities at the initial stage and after 50 cycles were measured. The results are shown in Table 1.

Example 2 137.9 g of lithium nitrate and nickel hydroxide 185.4
After weighing g (the atomic ratio of lithium and nickel is Li / Ni (molar ratio) = 1.0), it is well crushed with a ball mill.
Mix and dry at 150 ° C. for 12 hours. The dried product was fired in an oxygen atmosphere at 700 ° C. for 10 hours and then crushed in a nitrogen atmosphere with a ball mill for 1 hour to obtain an average particle size of 12
A micron lithium-nickel composite oxide was obtained. The coating process was performed by the following method. Ethanol 300
2.1 g of lithium hydroxide monohydrate and 14.6 g of cobalt nitrate hexahydrate (Li / Co (molar ratio) = 1.0) were dissolved in g, and the lithium-nickel composite oxide obtained above was dissolved in this. 92.7 g (Co / Ni (molar ratio) = 0.05) of the product was added and dispersed. This dispersion was dried under the conditions that the outlet temperature of the spray dryer was about 100 ° C., and then, Example 1
Similarly to the above, the electrode active material coated was obtained by firing at 700 ° C. for 1 hour in an oxygen atmosphere. To investigate the stability of this electrode active material, the same treatment and battery performance test as in Example 1 were performed. The discharge capacity results are shown in Table 1.

Example 3 83.9 g of lithium hydroxide monohydrate, 166.9 g of nickel hydroxide and 15.6 g of aluminum hydroxide were used as starting materials.
(The mixing ratio is Li / Ni / Al (molar ratio) = 1.0 / 0.
A lithium-nickel composite oxide was obtained in the same manner as in Example 1 except that the ratio was changed to 9 / 0.1). Coating was performed in the same manner as in Example 1, and the same treatment and battery performance test as in Example 1 were performed in order to investigate the stability of the obtained electrode active material. The discharge capacity results are shown in Table 1.

Example 4 Starting materials were 83.9 g of lithium hydroxide monohydrate, 166.9 g of nickel hydroxide and 137.0 of basic cobalt carbonate.
g (mixing ratio Li / Ni / Co (molar ratio) = 1.0 /
A lithium-nickel composite oxide was obtained in the same manner as in Example 1 except that the ratio was changed to 0.9 / 0.1). Coating was performed in the same manner as in Example 1, and the same treatment and battery performance test as in Example 1 were performed in order to investigate the stability of the obtained electrode active material. The discharge capacity results are shown in Table 1.

Example 5 A lithium-nickel composite oxide was obtained in the same manner as in Example 1. The coating was performed in the same manner as in Example 1 except that the solvent used for coating was changed to water. To investigate the stability of this electrode active material, the same treatment and battery performance test as in Example 1 were performed. The discharge capacity results are shown in Table 1.

Comparative Example 1 The same treatment and battery performance test as in Example 1 were carried out except that the lithium-nickel composite oxide obtained in Example 1 was not used for coating. The discharge capacity results are shown in Table 1.
Shown in

Comparative Example 2 The same treatment and battery performance test as in Example 1 were performed except that the lithium-nickel composite oxide obtained in Example 2 was not used for coating. The discharge capacity results are shown in Table 1.
Shown in

Comparative Example 3 The same treatment and battery performance test as in Example 1 were carried out except that the lithium-nickel composite oxide obtained in Example 3 was not used for coating. The discharge capacity results are shown in Table 1.
Shown in

Comparative Example 4 The same treatment and battery performance test as in Example 1 were carried out except that the lithium-nickel composite oxide obtained in Example 4 was not used for coating. The discharge capacity results are shown in Table 1.
Shown in

[0029]

[Table 1] Battery characteristics of electrode active material after 1 hour treatment at 60 ° C and 90% relative humidity

[0030]

The electrode active material of the non-aqueous electrolyte battery of the present invention is coated with a lithium-transition metal M composite oxide as compared with the conventional lithium-nickel composite oxide, so that the initial and 50 cycles of the battery can be improved. The subsequent discharge capacity can be dramatically increased. Further, it is possible to obtain a safe secondary battery having excellent storage stability and stability against moisture, which cannot be obtained by the conventional technique.

Claims (3)

[Claims] 1. The general formula Li _x Ni _y N _z O ₂ (N is L
i, Ni, elements other than O, 0.8 <x <1.2, 0.8
<Y + z <1.2, 0 ≦ z <0.2), the surface of the lithium-nickel composite oxide is a lithium-transition metal M composite oxide (M is one or more of Co, Mn, and Fe, N
and an electrode active material for a non-aqueous electrolyte battery. 2. A compound of a transition metal M (M is one or more of Co, Mn, and Fe, including a part of Ni) and a lithium compound are dissolved or suspended in a solvent to obtain a compound represented by the general formula Li _x Ni. _{yN z} O ₂ (N is an element other than Li, Ni, and O, 0.8 <x <1.2, 0.8 <y + z <1.2, 0
A method for producing an electrode active material for a non-aqueous electrolyte battery, comprising adding a lithium-nickel composite oxide represented by ≦ z <0.2) to form a slurry, and drying and firing the slurry. 3. A non-aqueous electrolyte battery using the electrode active material of the non-aqueous electrolyte battery according to claim 1 for a positive electrode or a negative electrode.