JPH10152327A - Production of lithium-containing multiple oxide and kiln therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the renewing frequency of a vessel or lining material thereof and to improve the purity of the product by forming, using silver, the surface of a vessel in a kiln with which a cobalt stock compound and/or nickel stock compound and a lithium stock compound contact and by investigating a material of the vessel for a stationary furnace or a turnnel kiln and a lining material of the kiln for a rotary kiln, etc. SOLUTION: This method for producing a lithium-containing multiple oxide of the general formula LiCOXNi1- XO2 (0<=(x)<=1) used as an anodic active material of a nonaqueous electrolyte lithium battery comprises firing a stock mixture held in a vessel such as a case or a tray for a stationary furnace or a tunnel kiln. The vessel is made of silver, or of alumina refractory ceramic or heat- resisting stainless steel alloy with the inner surface coated with silver, or another vessel made of silver foil is laded inside the vessel. In the case of a rotary kiln, the surface of its lining material is coated with silver. The firing temperature is 600-900 deg.C and examples of stock compounds include lithium oxide, lithium carbonate, cobalt oxide, cobalt hydroxide, nickel oxide and nickel carbonate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a lithium-containing composite oxide, in particular, a composite oxide of lithium and cobalt and / or nickel, and a firing furnace used for the production.

[0002]

2. Description of the Related Art A non-aqueous electrolyte lithium secondary battery using lithium ion-doped or undoped carbonaceous material, lithium metal or lithium compound as a negative electrode has a high voltage,
Numerous studies have been conducted because of the high energy density. As a positive electrode active material used for a nonaqueous electrolyte lithium secondary battery, LiCoO ₂ has already been put to practical use, but as a next-generation positive electrode active material, LiCo _x Ni _1-x O _{2 is used.}
(0 <x ≦ 1) (Japanese Unexamined Patent Publication No. 63-299056,
1-294364), LiAl _0.25 Ni _0.75 O
₂ (J. Electrochem. Soc., 142
(1995), 4033-9) and the like.

[0003] These positive electrode active materials are prepared by mixing raw materials and putting them in a container and firing them in an oxygen atmosphere in a fixed furnace or a tunnel furnace, or putting the raw material mixture directly in a rotary furnace without putting them in a container. It is manufactured by firing.

For example, in the case of producing LiNiO ₂ , a mixture of lithium hydroxide or lithium nitrate and nickel oxide, nickel hydroxide or nickel carbonate as raw materials is used.
It is put in a container and fired in a fixed furnace or a tunnel furnace, or directly put in a rotary furnace and fired. This firing is performed at a temperature of 600 to 1000 ° C. in an oxygen atmosphere.

The container for the raw material and the lining material of the rotary furnace are in direct contact with the raw material. The material is generally alumina, mullite, cordierite which is usually used in industrial refractory furnaces. Heat-resistant ceramic materials such as
Alternatively, a heat-resistant alloy material such as SUS304 or SUS310S may be used.

However, when LiCo _x Ni _1-x O ₂ (0 <x ≦ 1) is manufactured using a heat-resistant ceramic material,
During the firing, the lithium compound is melted and penetrates into the above-mentioned container or the like which comes into direct contact with the raw material. As a result, repeated use causes cracks or peeling at the portion of the container or the like that comes into contact with the lithium compound, and eventually the container or the like becomes unusable and requires frequent renewal.

When the alloy material is used as the above-mentioned container or the like, for example, when LiNiO ₂ is manufactured under the sintering conditions of 700 ° C. for 12 hours, 80 mg / dm.
^2. 85 mg / dm ² is corroded by SUS310S and cannot be used in actual production. The product Li
NiO ₂ itself also causes problems such as mixing of impurities and a change in composition. For example, when NiO ₂ is used as a positive electrode active material of a battery, it causes deterioration of battery characteristics. For this reason, when LiNiO ₂ is manufactured as a positive electrode active material of a battery, a container made of pure nickel or the like is currently used.

However, even in a container made of pure nickel or the like, the surface is oxidized by prolonged exposure to an oxygen atmosphere, and nickel oxide starts to peel off from the surface by repeated use. Therefore, it is necessary to frequently update containers and the like.
In particular, in a rotary furnace in which raw materials are directly charged, it is necessary to renew the lining material of the furnace, and the ratio of the renewal to the production cost of the positive electrode active material is also unacceptable.

[0009] In addition, in terms of productivity, the rotary furnace can be continuously produced in large quantities, but frequent replacement of the lining material results in a large loss of production time, so that it is difficult to actually use it as a production system. It is. Therefore, it is important to improve containers such as saggers and trays for holding raw materials in fixed furnaces and tunnel furnaces and to improve furnace lining materials in rotary furnaces.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a method for producing a lithium-containing composite oxide, in which when a container is fired in a firing furnace such as a fixed furnace or a tunnel furnace, the material of the container is changed to a rotary furnace. When raw materials are directly put into the firing furnace without using a container, as in the case of, etc., by examining the material of the lining material of the firing furnace, the frequency of renewal of those containers and lining materials can be reduced, and high purity An object of the present invention is to provide a method for producing a lithium-containing composite oxide.

[0011]

SUMMARY OF THE INVENTION The present invention provides a method for producing a lithium-containing composite oxide, comprising firing a raw material mixture containing a cobalt raw material compound and / or a nickel raw material compound and a lithium raw material compound in a firing furnace in an oxygen atmosphere. In the method,
A method for producing a lithium-containing composite oxide, characterized in that at least the surface of a furnace material in a firing furnace or a container in a firing furnace containing the raw material mixture is made of silver, wherein the raw material mixture is contacted during firing, and A firing furnace for performing is provided.

The present inventors have proposed a lithium-containing composite oxide which has been widely used as a positive electrode active material of a non-aqueous electrolyte lithium battery, particularly a general formula LiCo _x Ni _{1 -x} O ₂ (0 ≦ 0).
In the production of the composite oxide represented by x ≦ 1), as a material of a lining material such as a container or a rotary furnace in which the raw material comes into direct contact with the raw material during firing, a material with little cracking or peeling after firing is used. I searched a lot. As a result, it has been found that when a material in which the surface of the portion in contact with the raw material is made of at least silver is used, the amount of corrosion is significantly smaller than that of the above alloy materials.

In the present invention, when a fixed furnace or a tunnel furnace is used, the raw material mixture is placed in a container such as a sagger or a tray and fired. According to the invention, this container is made of silver or is coated on the surface with silver. The container whose surface is covered with silver is made of alumina refractory ceramics or heat-resistant SUS
Use an alloy container. In the present invention, the inner surfaces of these containers may be directly coated with silver, or a container made of silver foil may be loaded inside the containers to form a double container.

Considering that the melting point of silver is 960 ° C. (vacuum), when the temperature is raised to a temperature close to the temperature, a container made of a heat-resistant SUS alloy coated with silver on the inside is placed inside the ceramic container. It can be loaded and the container can be doubled. Considering the advantage of easy manufacture and replacement, it is preferable to use a double container.

When a rotary furnace is used, the lining material of the furnace comes into direct contact with the raw material in order to put the raw material directly into the furnace. Therefore, in the present invention, the surface of the lining material is coated with silver. As the lining material, specifically, for example, heat-resistant SU
A material in which the surface of the S alloy is coated with silver can be used.

The silver used in the present invention may contain impurities, but preferably has a purity of 95% or more.
More preferably, it is 99.5% or more.

In the present invention, considering the melting point of silver,
The firing temperature of the lithium-containing composite oxide is preferably 900 ° C. or lower.

Generally, 800 to 1000 ° C. is used for the production of a lithium cobalt composite oxide, and 600 to 800 ° C. is used for the production of a lithium cobalt nickel composite oxide.
In the production of lithium nickel composite oxide, 600 to
Since the calcination temperature of 800 ° C. is required, the production method of the present invention is particularly preferable for producing a lithium cobalt nickel composite oxide and a lithium nickel composite oxide which can be calcined at a relatively low temperature. If so, optimization of the firing temperature is required.

In the present invention, the raw material lithium compound is lithium oxide, lithium hydroxide, lithium nitrate, lithium carbonate or the like, and the cobalt compound is cobalt oxide;
It is preferable to use nickel oxide, nickel hydroxide, nickel carbonate and the like as the nickel compound such as cobalt hydroxide and cobalt carbonate.

The composite oxide of lithium and cobalt and / or nickel produced by the production method of the present invention comprises:
It can be represented by the general formula LiCo _x Ni _1-x O ₂ (0 ≦ x ≦ 1), but Ca, Mg, Fe, Cr, Mn, B, A
It is also possible to include components such as l.

[0021]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples (Examples 1 to 3) and Comparative Examples (Example 4), but the present invention is not limited to these.

[Example 1] A high-purity alumina sagger having a bottom surface of 90 mm x 90 mm and a height of 50 mm was placed 50 mm in the center of the bottom.
× 50 mm, thickness of 1 mm, weighs 27.6104 g of a silver test piece, and flatly spreads thereon 100 g of a mixture of lithium hydroxide and nickel hydroxide in a molar ratio of 1: 1. After firing at 700 ° C. for 12 hours in an electric furnace in an oxygen atmosphere, the product was allowed to cool to room temperature, and the fired product was taken out. The same synthesis was repeated 10 times. When examined by X-ray diffraction,
The fired product was LiNiO ₂ . Next, the silver test piece was taken out, washed sequentially with diluted hydrochloric acid and pure water, dried and weighed precisely. As a result, the weight loss of the silver test piece was 5.4 mg.

Example 2 Cobalt nickel hydroxide (Co / Ni = 0.25) was used instead of nickel hydroxide,
Li was prepared in the same manner as in Example 1 except that the firing temperature was set to 750 ° C.
Co _0.2 Ni _0.8 O ₂ was fired. After repeating this baking ten times, the silver test piece was taken out, washed as in Example 1,
When dried and weighed accurately, the weight loss of the silver test piece was 6.5.
mg.

[Example 3] Instead of nickel hydroxide, cobalt nickel hydroxide (Co / Ni = 0.33) was used.
Li was prepared in the same manner as in Example 1 except that the firing temperature was set to 750 ° C.
Co _0.25 Ni _0.75 O ₂ was fired. After repeating this baking ten times, the silver test piece was taken out, washed as in Example 1,
When dried and weighed precisely, the weight loss of the silver specimen was 6.4.
mg.

[Example 4] Instead of a silver test piece, 30 mm x
Calcination was carried out in the same manner as in Example 1 except that a 10 mm pure nickel test piece was used. The peak of the X-ray diffraction of the fired product is Li
Although it was NiO ₂ , when the nickel test piece was taken out, the surface was blackened. The nickel test piece was washed with an ultrasonic cleaner and dried, but the blackening of the surface did not disappear, suggesting that an oxide was formed. When the calcining was repeated 5 times in the same manner and then precisely weighed, the weight of the test piece increased by 414 mg as compared with the first time. When the surface black matter was further scraped off and weighed again, the weight was reduced by 2.0541 g from the initial level.

[0026]

According to the present invention, in the production of a lithium-containing composite oxide, it is possible to suppress the corrosion of equipment materials that are in direct contact with the raw material during firing, such as a container for storing the raw material and an inner furnace material of a rotary furnace, and reduce the frequency of renewal. Can be significantly reduced. In addition, a lithium-containing composite oxide having a small amount of impurities and excellent characteristics as a positive electrode active material of a lithium secondary battery and having a stable composition, particularly a composite oxide of lithium and nickel and / or cobalt is produced.

Claims (5)

[Claims] 1. A method for producing a lithium-containing composite oxide, comprising firing a raw material mixture containing a cobalt raw material compound and / or a nickel raw material compound and a lithium raw material compound in an oxygen atmosphere in a firing furnace. A method for producing a lithium-containing composite oxide, wherein at least the surface of a furnace material in a firing furnace or a container in a firing furnace for containing the raw material mixture, which is brought into contact with, is made of silver. 2. A lithium-containing composite oxide having the general formula LiC
method for producing _{o x Ni 1-x O 2} (0 ≦ x ≦ 1) lithium-containing complex oxide according to claim 1, which is represented by. 3. The method for producing a lithium-containing composite oxide according to claim 1, wherein the firing temperature is 600 to 900 ° C. 4. A lining material coated with silver for producing a lithium-containing composite oxide by firing a raw material mixture containing a cobalt raw material compound and / or a nickel raw material compound and a lithium raw material compound. Firing furnace. 5. A raw material mixture containing a cobalt raw material compound and / or a nickel raw material compound and a lithium raw material compound to be fired to produce a lithium-containing composite oxide, at least the surface into which the raw material mixture is put is made of silver. A firing furnace having a container.