JPH11139829A - Production of positive electrode material for lithium ion secondary cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide this production of the positive electrode material consisting of a lithium-containing multiple metal oxide which is subjected to sufficient crystal growth and capable of exhibiting high performance. SOLUTION: In this production that comprises firing a precursor material of a lithium-containing multiple metal oxide to produce the positive electrode material consisting of the lithium-containing multiple metal oxide, the precursor material is fired while supplying an oxygen-containing gas, with a rotary kiln provided with a rotary block which has at least three blades and at least two of these three blades of which are placed so as to be in contact with the inner wall of the rotary kiln.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a positive electrode material for a lithium ion secondary battery comprising a composite oxide such as lithium cobaltate, lithium nickelate or lithium manganate.

[0002]

2. Description of the Related Art Composite oxides such as lithium cobaltate, lithium nickelate or lithium manganate used as a cathode material for lithium ion secondary batteries are composed of oxides, carbonates or hydroxides of the respective metals. It is manufactured by firing a precursor material that is a mixture in an atmosphere of an oxygen-containing gas such as air.

[0003] As a firing method, there is a method in which a powder of a precursor substance is filled in a heat-resistant container such as a magnetic board, and this is fired in a firing furnace such as a tunnel furnace or a muffle furnace in an oxygen-containing gas atmosphere. Have been. However, these conventional firing methods may not provide a composite oxide having satisfactory performance as a positive electrode material for a lithium ion secondary battery. In particular, when obtaining a nickel-based composite oxide such as lithium nickelate, the positive electrode for a lithium ion secondary battery is insufficient in crystal growth even when calcined by a conventional method, and is satisfactory in terms of battery performance such as storage capacity. A composite oxide as a material cannot be obtained. This is considered to be due to insufficient contact between the raw material powder and the oxygen-containing gas.

As a method for firing the raw material powder, there is a method using a rotary kiln other than the above method. According to this method, the contact between the raw material powder and the oxygen-containing gas is somewhat better than the above method, but in order to obtain a composite oxide as a cathode material for a lithium ion secondary battery having the desired battery performance, In addition, it is necessary to take measures such as reducing the amount of raw material supplied or extending the firing time.

[0005]

SUMMARY OF THE INVENTION The present invention relates to an improvement in a conventional rotary kiln sintering method, in which a lithium-containing composite metal oxide is oxidized by using a rotary kiln which makes better contact with an oxygen-containing gas such as air. It is an object of the present invention to provide a method for producing a positive electrode material for a lithium ion secondary battery comprising a lithium-containing composite metal oxide exhibiting high performance in which crystals are sufficiently grown by firing a precursor substance.

[0006]

According to the present invention, there is provided a method for producing a positive electrode material for a lithium ion secondary battery, comprising the steps of: firing a lithium-containing composite metal oxide precursor material; In a method of manufacturing a positive electrode material for a secondary battery, the precursor material is loaded such that a rotating block having at least three blades is such that two of the at least three blades are in contact with an inner wall of a rotary kiln. The sintering is performed by using the obtained rotary kiln while supplying an oxygen-containing gas.

[0007] The lithium-containing composite metal oxide precursor is
It is a mixture of compounds of the respective metals that becomes a composite metal oxide by firing. There is no particular limitation on these preparation methods, and a method of mixing a conventionally used oxide or carbonate such as cobalt, nickel or manganese with lithium carbonate or lithium hydroxide to form a uniform mixture is used. is there. For example, Japanese Patent Application Laid-Open
A mixture is prepared by the methods disclosed in Japanese Patent Application Nos. 9-156931, 8-284380 and 8-336687.

[0008] The precursor mixture obtained by the above-described method is then calcined in a rotary kiln while supplying an oxygen-containing gas. In the present invention, a rotating block having at least three blades has at least three blades. A rotary kiln is used in which two of the blades are in contact with the inner wall of the rotary kiln. The rotary block intermittently rotates in the same direction as the rotary kiln with the rotation of the rotary kiln. As a rotary kiln, a batch method in which a predetermined amount of raw material is filled at a time and fired at a predetermined temperature for a predetermined time, or a continuous method in which raw material is continuously supplied from one port of the kiln and continuously discharged from the other port, is used. There is, but any may be.

The rotary kiln used in the present invention will be described in more detail. As shown in FIG. 1, a rotating block 2 having (at least) three blades 2A, 2B and 2C is composed of (at least) three blades. The two blades 2 </ b> A and 2 </ b> B are mounted so as to come into contact with the inner wall of the rotary kiln 1. When the rotary kiln rotates in the direction of arrow A, the rotating block moves the two blades 2 in the same direction as the rotary kiln rotates.
A and 2B move while contacting the inner wall of the rotary kiln. At this time, the material to be fired in the kiln is scraped up to the upper part of the kiln. When the rotating block moves to the side of the kiln to some extent, the balance of the rotating block is lost and arrow B
In the direction of (1), the two blades 2B and 2C come into contact with the inner wall of the rotary kiln. At this time, the object to be fired is dropped to the lower part of the kiln, and the object to be fired attached to the surface of the blade or the inner wall of the kiln is wiped off by the impact when the rotating block rotates by one blade. In this way, the mixing of the raw materials and the contact with the oxygen-containing gas are sufficiently performed. The number of blades may be three or more, but even when the number of blades is large, the number of blades that come into contact with the inner wall of the kiln is two. Although there is no particular upper limit on the number of blades, providing too many blades is not preferable because the impact during rotation of one blade and the amount of powder scraped up become small. A practical upper limit for the number of blades will be about six, depending on the kiln inner diameter. In the present invention, assuming that the inner diameter of the kiln is D and the rotation diameter of the rotating block is d, d / D = 0.
It is preferably in the range of 6 to 0.8. If it is less than 0.6, the rotation of the rotating block is not smooth, and if it exceeds 0.8, the impact force of the kiln by the blade becomes weak.

At this time, air, oxygen-enriched air or oxygen gas is continuously supplied into the kiln by appropriate means. At the same time, water vapor, carbon dioxide gas and the like generated during firing are discharged. In the case of the continuous type, it is preferable that the oxygen-containing gas flow in the opposite direction to the flow of the raw material for firing. That is,
It is preferable to supply the oxygen-containing gas from the fired material discharge side and discharge the oxygen-containing gas from the fired raw material supply side together with the generated steam and carbon dioxide gas. According to this method, the crystallization of the composite oxide is further promoted because the precursor mixture comes into contact with the oxygen-rich gas at the final stage of the firing.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The firing temperature in a rotary kiln is not particularly limited as long as it is within a temperature range sufficient for a mixture of precursor materials to be a sufficiently grown composite oxide. For example, in the batch method, after filling the raw material in the kiln, 650
Baking at a temperature of 850 ° C., preferably 700-800 ° C. for a predetermined time. Alternatively, a two-stage firing method is employed in which firing is first performed at a temperature of 400 to 650 ° C., preferably 400 to 600 ° C. for a predetermined time, followed by firing at a temperature of 650 to 850 ° C., preferably 700 to 800 ° C. for a predetermined time. In the continuous method, the temperature is supplied to the kiln set so that the temperature gradient is gradually increased toward the discharge side of the material to be fired, and the material is fired while moving in the kiln. At this time, the raw material mixture stays in a range of 400 to 650 ° C., preferably 400 to 600 ° C. for a predetermined time, and finally reaches 650 to 85 ° C.
It is preferable to set the temperature so as to stay in a range of 0 ° C., preferably 700 to 800 ° C. for a predetermined time, fire and discharge the kiln.

The amount of the oxygen-containing gas to be supplied is not particularly limited. However, the partial pressure of steam or carbon dioxide gas generated during the calcination in the kiln is made as low as possible to facilitate the formation of the composite oxide by the calcination. In order to do so, it is desirable to supply an oxygen-containing gas at least 5 times, preferably at least 10 times, the amount of gas (steam and / or carbon dioxide) generated by firing. The oxygen-containing gas discharged from the kiln may be recycled at least after a portion of the oxygen-containing gas has been removed from the gas, for example.

[0013]

Example 1 494 parts by weight of nickel nitrate (hexahydrate) and 89 parts by weight of cobalt nitrate (hexahydrate) were dissolved in pure water to obtain a solution.
000 parts by weight of a mixed aqueous solution (solution A) was prepared. In addition, 318 parts by weight of sodium carbonate was dissolved in pure water to prepare an aqueous solution (solution B) of 1800 parts by weight of sodium carbonate. 80
While maintaining this temperature in 1000 parts by weight of hot water of
Liquid A and liquid B were simultaneously added. After maintaining the temperature for another 60 minutes after completion of the pouring, the resulting precipitate was filtered, washed,
By drying, a mixture of basic carbonates of nickel and cobalt was obtained. Next, the mixture was pulverized by adding water with a wet pulverizer, and the obtained slurry was dried with a spray drier and then calcined at 400 ° C. for about 2 hours to obtain fine powder of nickel and cobalt oxides.
By sufficiently pulverizing and mixing 500 parts by weight of the oxide fine powder prepared by the above method and 271 parts by weight of lithium hydroxide, 771 parts by weight of a cobalt-containing lithium nickel oxide precursor powder was obtained. This cobalt-containing lithium nickelate precursor powder was charged into a kiln with 10 rotating blocks each having 3 blades (length 4 m, height 0.8 m from the center to the tip of the blade), 40 m in length, and 40 m in diameter. 1.5m continuous rotary kiln (rotation speed: 20 times /
Min). The feed rate of the precursor powder is 17K
g / hr. The temperature in the kiln was set higher from the powder supply side to the discharge side, and the temperature on the powder discharge side was 750 ° C. 400 in the kiln
The residence time of the powder in the 600 ° C. region is 0.5 hours,
The residence time in the 750 ° C. region was 1 hour. Oxygen gas was supplied at 0.4 m ³ / hr from the powder discharge side. The obtained cobalt-containing lithium nickelate (LiCo _0.15 Ni _0.85 O ₂ )
Were spherical fine particles having an average particle diameter of 10 μm (Sample A).

[0014]

COMPARATIVE EXAMPLE 1 A cobalt-containing lithium nickelate precursor powder obtained in the same manner as in Example 1 was subjected to the same conditions using a continuous rotary kiln as used in Example 1 without a rotating block. Was fired. The obtained cobalt-containing lithium nickelate (LiCo _0.15 Ni _0.85 O ₂ )
Were spherical fine particles having an average particle diameter of 10 μm (Sample B).

[0015]

Example 2 Electrolytic manganese dioxide powder (γ-MnO ₂ , purity 92%) was ground to an average particle size of about 0.5 μm. The atomic ratio of lithium to manganese is Li / Mn = 0.5
An aqueous solution of lithium hydroxide was added to the mixture to obtain a slurry having a solid concentration of about 25% by weight. This slurry was dried with a spray drier. Drying conditions are hot air inlet temperature 300-310 ° C and outlet temperature 110-110.
The temperature was set to 150 ° C. 5 kg of the dried lithium manganate precursor powder was fired in a rotary kiln equipped with the same rotary block as in Example 1. The obtained lithium manganate was spherical fine particles having an average particle size of 10 μm (Sample C).

[0016]

Comparative Example 2 Lithium manganate precursor powder obtained in the same manner as in Example 2 was used under the same conditions using the same continuous rotary kiln as used in Example 1 without a rotating block. Fired. The obtained lithium manganate was spherical fine particles having an average particle size of 10 μm (Sample D).

[0017]

Example 3 Samples A to D obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were mixed with acetylene black and polytetrafluoroethylene powder in a weight ratio of 75: 20: 5. After sufficient kneading, thickness 0.1 mm, diameter 1
It was molded to 6 mm and dried at 110 ° C. to obtain a positive electrode for testing. A separator (trade name: Celgard) obtained by impregnating an electrolyte solution obtained by dissolving 1 mol / L LiClO ₄ in a mixed solvent of propylene carbonate and dimethoxyethane at a volume ratio of 1: 1 and a thickness of 0.2 μm A battery for evaluation was prepared by laminating a metal lithium foil in a cell for a button-type battery. These batteries were subjected to a charge / discharge test. The charge and discharge conditions were a constant current and a current density of 0.5 mA / cm ² , the charge potential was up to 4.3 V, and the discharge potential was 3.
Potential regulation up to 0 V was performed. Table 1 shows the results.

[0018]

[Table 1]

As can be seen from the above results, the precursor material was loaded with a rotating block having at least three blades such that two of the at least three blades were in contact with the inner wall of the rotary kiln. The product fired by the rotary kiln) has both a large charge capacity and a large discharge capacity and a high charge / discharge efficiency, as compared with a product fired by a rotary kiln without a rotating block.

[0020]

As described above, the contact between the precursor powder and oxygen is improved, and water vapor, carbon dioxide, and the like generated during firing are easily removed. As a result, it is possible to obtain a composite metal oxide which has sufficiently grown crystals as compared with the conventional firing method using a rotary kiln and has good performance as a positive electrode material for a lithium ion secondary battery.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a rotary kiln loaded with a rotating block.

[Explanation of symbols]

 Reference Signs List 1 rotary kiln 2 rotating block 2A rotating block blade A 2B rotating block blade B 2C rotating block blade C

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masayoshi Watanabe 1-26 Takiya Honmachi Niigata Niigata Pref.JGC Chemicals Research & Development Laboratory (72) Inventor Masami Sakaguchi 1-26 Takitani Honmachi Niigata Niigata Nikko Chemical Co., Ltd. Inside the development laboratory

Claims (1)

[Claims] 1. A method for producing a positive electrode material for a lithium ion secondary battery comprising a lithium-containing composite metal oxide by calcining a lithium-containing composite metal oxide precursor material, wherein the precursor material comprises at least three sheets. The rotating block having the blades is fired while supplying an oxygen-containing gas by using a rotary kiln in which at least two of the at least three blades are in contact with the inner wall of the rotary kiln. A method for producing a positive electrode material for a lithium ion secondary battery.