JPH09265985A - Positive electrodeactive material for non-aqueous electrolyte secondary battery, its manufacture and non-aqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the non-aqueous electrolyte secondary battery which is inexpensive, but high in charging/discharging capacity. SOLUTION: The positive electrode active material contains powder particles holding lithium nickel oxides represented by a formula LiNiO2 as an effective constituent, the whole or a part of the powder particles is made out of nickel oxides or nickel hydroxides as raw material, in the production process of which cobalt or manganese is coated over the surfaces of nickel oxide or nickel hydroxide particles.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Lithium ion secondary batteries are said to have a higher energy density (workload that can be taken out from a charged battery per battery volume) than conventional mainstream Ni-Cd or Ni-MH secondary batteries. Due to the demands for downsizing and weight saving of today's portable electronic devices, the features of this lithium-ion secondary battery are drawing attention and vigorous development.

In the so-called lithium ion secondary battery which is currently on the market, a lithium cobalt composite oxide represented by LiCoO ₂ is used as a positive electrode active material. However, LiCoO ₂
Has a drawback in that the raw material of the cobalt mineral is small, and as a result, it is expensive.

Therefore, a lithium nickel composite oxide represented by the formula LiNiO ₂ and a lithium manganese composite oxide represented by the formula LiMn ₂ O ₄ have been studied as positive electrode active materials substituting for LiCoO ₂ . In particular, the lithium-nickel composite oxide is considered to be the most suitable positive electrode active material for the above purpose because the charge potential is slightly lower than that of LiCoO ₂ , but the charge-discharge capacity is rather larger than that of LiCoO ₂ .

[0005]

However, in order to synthesize LiNiO ₂ having a large charge / discharge capacity, it is preferable that the firing atmosphere during production is not an air atmosphere but an oxygen atmosphere. However, there is a drawback that the manufacturing cost increases.

An attempt to use a firing condition in an air atmosphere for the synthesis of a lithium nickel composite oxide has been conducted, for example, in a system in which 10 mol% of cobalt is added to nickel (Aoki et al.
35th Battery Symposium, Nagoya (1994)), or a system in which 10 to 20 mol% of manganese was added to nickel (Yamato et al.,
It has been reported that a compound oxide having sufficient charge / discharge characteristics can be obtained by the synthesis at the 35th battery discussion meeting, Nagoya (1994). In these systems, the synthesis reaction of the lithium-nickel composite oxide can be efficiently progressed even in the air atmosphere because the added nickel or manganese acts as an oxidation-reduction catalyst, and the nickel oxidation reaction is It is considered that this is the result of being promptly performed even in the atmosphere.

On the other hand, however, the addition of cobalt or manganese to the lithium nickel oxide gives unfavorable results as a secondary battery positive electrode active material. That is, adding cobalt to nickel would significantly increase the cost of the raw material. Further, addition of cobalt causes a decrease in charge / discharge capacity, and the original charge / discharge capacity of the lithium nickel composite oxide cannot be obtained. On the other hand, in the case of manganese deposition, the cost of the raw material is not so much affected, but the charge / discharge capacity is considerably reduced.

As described above, addition of cobalt or manganese is effective for synthesizing the lithium nickel composite oxide in the air atmosphere, but on the other hand, addition of cobalt or manganese has a negative aspect in electrode characteristics. It is desired that the effect be obtained with a minimum addition amount of cobalt or manganese.

[0009]

As a result of earnest research, the inventors of the present invention have deposited cobalt or manganese on the surface of nickel hydroxide or nickel oxide particles, and then added lithium by reaction in an air atmosphere. By doing so, it was found that the production reaction of lithium nickel oxide in air proceeds efficiently, and as a result, it is possible to reduce the amount of cobalt or manganese used with respect to nickel, and to complete the present invention. I arrived.

That is, the present invention includes powder particles containing lithium nickel oxide represented by the formula LiNiO ₂ as an active ingredient, and all or part of the powder particles contain nickel oxide or nickel hydroxide. A positive electrode active material for a non-aqueous electrolyte secondary battery, which is manufactured as a raw material, and includes a step of depositing cobalt or manganese on the surface of the nickel oxide or nickel hydroxide particles in the manufacturing process, and manufacturing thereof. Regarding the method.

The present invention also provides at least a positive electrode active material,
A non-aqueous electrolyte secondary battery comprising a separator and a cathode active material, wherein the positive electrode active material is the above-described positive electrode active material for a non-aqueous electrolyte secondary battery.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the metal element deposited on the surface of nickel oxide or nickel hydroxide in the process of synthesizing a lithium nickel based composite oxide positive electrode material is cobalt or manganese.

The deposition of the elemental cobalt or manganese onto nickel oxide or nickel hydroxide, which is carried out in the present invention, is particularly necessary for the synthesis reaction of the lithium nickel-based composite oxide, and during the reaction process, the particle surface The cobalt or manganese element may be diffused into the nickel oxide or nickel hydroxide particles. Furthermore, it is preferable that the cobalt or manganese element is near the surface of the particle to catalyze the redox reaction of oxygen and nickel at the synthesis stage of the lithium-nickel composite oxide, and at the stage where the reaction proceeds, cobalt or manganese is It is preferable that the particles diffuse into the inside of the particles. This is because cobalt or manganese is dispersed inside the lithium-nickel-based composite oxide particles, for example, Arai et al. (Battery Technology, 7,98-106 (199
This is because 5)) has the effect of improving the charge / discharge cycle durability of the lithium nickel-based composite oxide.

The present invention will be described below by taking the case of cobalt deposition as an example, but the same applies to the case of manganese deposition. In the present invention, cobalt and manganese can be used together.

The particle size of the lithium nickel composite oxide used in the present invention can be applied to a wide particle size range of 0.2 to 40 μm, but the particle production conditions (synthesis temperature, reaction time, etc.) and battery system can be used. From the viewpoint of ease of application to
0.3 to 30 μm is preferable.

The production of the lithium-nickel composite oxide according to the present invention is carried out, for example, by the following procedure.

Nickel oxide obtained by heating nickel carbonate to, for example, 650 ° C. or commercially available nickel hydroxide for nickel-hydrogen battery (for example, one having a particle size of 5 to 20 μm) is added to cobalt chloride (cobalt-coated). If) Suspend in aqueous solution. While blowing air or oxygen (or in the presence of hydrogen peroxide), an alkaline aqueous solution is dropped to reach neutralization. Stirring is continued as it is to deposit cobalt oxyhydroxide on the surface of nickel oxide (or nickel hydroxide). The precipitate obtained is washed with water and dried (for example 120 ° C).
/ 12 hours) or calcination (for example, 400 ℃ / 1 hour), and then mix with lithium hydroxide (or lithium salt represented by lithium carbonate) in an air atmosphere at 500-1000 ℃, preferably 600- Heat to a temperature of 800 ° C. The electrode active material of the present invention is obtained by the reaction for 24 to 72 hours.

According to the production method of the present invention, cobalt more effectively acts as a catalyst, and as a result, a lithium nickel oxide having better charge / discharge characteristics can be obtained. At the same time, this also makes it possible to reduce the amount of cobalt added.

According to Aoki et al., In order to synthesize lithium nickel oxide in an air atmosphere, when cobalt is added as an example, it is necessary to add 10 mol% to nickel ( Aoki et al., 35th Battery Symposium, Nagoya
(1994)). However, this is the required amount when the powder raw materials of nickel and cobalt are simply mixed and the synthetic reaction is performed. On the other hand, according to the method of the present invention, the amount of cobalt added can be 20 mol% or less with respect to nickel, preferably 10 mol% or less, and 10 mol% or less with respect to nickel. In addition, cobalt has a sufficient catalytic effect on the synthesis reaction of lithium nickel oxide, and a lithium nickel composite oxide having a large charge / discharge capacity may be obtained (usually, the addition amount is 10 mol% or more in the case of cobalt,
About 20 mol% for manganese).

[0020]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following examples, when simply expressed as “part” and “%”, “part by weight” is used.
And "% by weight".

Example 1 46 parts by weight of spherical nickel hydroxide (particle diameter of about 5 μm) mainly used in nickel-hydrogen batteries was mixed with 6 parts of cobalt chloride hexahydrate.
Parts are suspended in a solution of 400 parts of water and stirred while passing air through. The suspension is kept at 80 ° C., and a 2% aqueous sodium hydroxide solution is added dropwise thereto to reach neutralization. After the dropping is completed, the stirring is continued for 4 hours. The powder is filtered off, washed with water and dried at 120 ° C. 8 parts of powder obtained by calcination at 400 ° C for 1 hour (cobalt deposition amount is 5 mol% with respect to nickel), lithium hydroxide (LiOH · H ₂ O) 4.5
Parts and press-molding into tablets, then in air atmosphere 750
Hold at 48 ° C. for 48 hours to obtain a lithium-nickel-based composite oxide. The characteristic evaluation as an electrode active material is based on the following procedure. 15 parts of active material, 1 part of graphite, 1 part of acetylene black, 1.5 parts of polyvinylidene fluoride and 35 parts of N-methylpyrrolidone are mixed and dispersed by a ball mill. This is applied on aluminum foil and dried. Cut the obtained coating film to make an anode, and use a lithium counter electrode to measure the voltage range 3.1-
The charge / discharge characteristics at 4.3 V were measured. A polyethylene porous film is used as the separator between the electrodes, a dimethyl carbonate / ethylene carbonate (1/1 (weight ratio)) mixture is used as the electrolyte, and hexafluorophosphoric lithium (1 is used as the electrolyte.
Mol / l).

Example 2 46 parts by weight of spherical nickel hydroxide (particle size: about 5 μm) mainly used in nickel-hydrogen batteries was mixed with 12 parts of cobalt chloride hexahydrate.
Parts are suspended in a solution of 400 parts of water and stirred while passing air through. The suspension is kept at 80 ° C., and a 2% aqueous sodium hydroxide solution is added dropwise thereto to reach neutralization. After the dropping is completed, the stirring is continued for 4 hours. The powder is filtered off, washed with water and dried at 120 ° C. 8 parts of powder obtained by calcining this at 400 ° C for 1 hour (cobalt deposition amount relative to nickel
Lithium hydroxide (LiOH ・ H ₂ O) 4.5 against 10 mol%)
Parts and press-molding into tablets, then in air atmosphere 750
Hold at 48 ° C. for 48 hours to obtain a lithium-nickel-based composite oxide. The characteristic evaluation as the electrode active material was performed in the same manner as in Example 1.

Example 3 46 parts by weight of the same spherical nickel hydroxide as in Example 1 was suspended in a solution in which 10 parts of cobalt chloride tetrahydrate was dissolved in 400 parts of water, and the mixture was stirred while passing air. Keep the suspension at 80 ° C,
A 2% aqueous sodium hydroxide solution is added dropwise to reach neutralization. After the dropping is completed, the stirring is continued for 4 hours. The powder is filtered off, washed with water and dried at 120 ° C. 400 ° C
The mixture was mixed with 4.5 parts of lithium hydroxide (LiOH.H ₂ O) to 8 parts of powder obtained by calcination for 1 hour (the amount of manganese deposited was 10 mol% with respect to nickel), and tablets were formed. After pressure molding,
Hold at 750 ° C for 48 hours in an air atmosphere to obtain a lithium-nickel-based composite oxide. The characteristic evaluation as the electrode active material was performed in the same manner as in Example 1.

Comparative Example 1 The same nickel hydroxide as in Example 1 was calcined at 400 ° C. for 1 hour, and 8 parts of the obtained powder was mixed with lithium hydroxide (LiOH
-H ₂ O) (4.5 parts) is mixed, and the mixture is press-molded into tablets, and then kept at 750 ° C for 48 hours in an air atmosphere to obtain a lithium-nickel-based composite oxide. The characteristic evaluation as the electrode active material was performed in the same manner as in Example 1.

Comparative Example 2 Wako Pure Chemical Industries, Ltd. nickel carbonate (nickel content 47%) 8
Part and 0.76 part of cobalt carbonate are mixed and calcined at 500 ° C. for 2 hours. This is crushed and lithium hydroxide (LiOH ・ H ₂ O) 3.1
Parts and press-molding into tablets, then in air atmosphere 750
Hold at 48 ° C. for 48 hours to obtain a lithium-nickel-based composite oxide. The characteristic evaluation as the electrode active material was performed in the same manner as in Example 1.

Comparative Example 3 Wako Pure Chemical Industries, Ltd. nickel carbonate 8 (nickel content 47%) 8
Part and 1.5 parts of manganese carbonate are mixed and calcined at 500 ° C. for 2 hours. This is crushed, and lithium hydroxide (LiOH ・ H ₂ O) 3.3
Parts and press-molding into tablets, then in air atmosphere 750
The temperature is kept at 48 ° C. for 48 hours to obtain a lithium nickel complex oxide (the amount of manganese added is 20 mol% with respect to nickel). The characteristic evaluation as the electrode active material was performed in the same manner as in Example 1.

The above results are shown in Table 1.

[0028]

[Table 1]

Claims (5)

[Claims] 1. A powder particle containing lithium nickel oxide represented by the formula LiNiO ₂ as an active ingredient, wherein all or part of the powder particle is produced from nickel oxide or nickel hydroxide as a raw material. And a step of depositing cobalt or manganese on the surface of the nickel oxide or nickel hydroxide particles in the manufacturing process thereof, the positive electrode active material for a non-aqueous electrolyte secondary battery. 2. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the content of cobalt or manganese in the lithium nickel oxide is 20 mol% or less with respect to nickel. 3. A non-aqueous electrolyte secondary battery containing at least a positive electrode active material, a separator and a negative electrode active material, wherein the positive electrode active material is the positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1. A non-aqueous electrolyte secondary battery characterized by the above. 4. A step of suspending a powder containing nickel oxide or nickel hydroxide as a main component in an aqueous solution containing a cobalt salt or a manganese salt, and applying an alkali to the surface of the powder particles A powder obtained by depositing an oxide, a hydroxide or an oxyhydroxide, and lithium hydroxide or a salt containing lithium are mixed,
A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, which is characterized by holding at a temperature of up to 1000 ° C. 5. A powder containing nickel oxide or nickel hydroxide as a main component is suspended in an aqueous solution containing a cobalt salt or a manganese salt, and further reacted with air, oxygen or hydrogen peroxide when an alkali acts. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 4, wherein.