WO2011021480A1 - Process for production of positive electrode material for secondary batteries - Google Patents

Abstract

A process for producing a positive electrode material for secondary batteries, comprising the steps of: mixing a powder of a lithium compound (which is a raw material) with a powder of a metal compound to produce a mixed powder and granulating the mixed powder to produce powder granules; and burning the powder granules continuously at a predetermined temperature for a predetermined period to cause a reaction in the powder granules, thereby obtaining a composite oxide of lithium and the metal as the positive electrode material for secondary batteries.

Description

Method for producing positive electrode material for secondary battery

The present invention relates to a method for producing a positive electrode material of a secondary battery used for a power source of a portable device such as a notebook computer, a mobile phone, and a video camera, an electric vehicle, a hybrid electric vehicle, etc. The present invention relates to a method for producing a positive electrode material for a battery.

Currently, among secondary batteries, lithium ion secondary batteries have excellent energy density and output density, and are effective for miniaturization and weight reduction. Therefore, they are used as power sources for portable devices such as laptop computers, mobile phones, and video cameras. Has been. Lithium ion secondary batteries are also attracting attention as power sources for electric vehicles and power load leveling, and are also used as power sources for hybrid electric vehicles.

Examples of the positive electrode material of the lithium ion secondary battery include lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), and lithium manganate (LiMn ₂ O ₄ ).
In general, the positive electrode material of a lithium ion secondary battery is a mixture of a lithium compound, which is a raw material, and a compound such as an oxide or hydroxide, such as nickel, manganese, cobalt, etc., and the mixed powder is placed in a container. , And calcined at 700 to 1100 ° C., and then pulverized into powder. In addition to the above, various methods for producing a positive electrode material for a lithium ion secondary battery have been proposed (see Patent Document 1).

In Patent Document 1, based on the chemical formula of lithium manganese oxide, lithium hydroxide or decomposable lithium salt and manganese oxide or decomposable manganese salt are homogeneously mixed by a theoretical amount, and this homogeneous mixing is performed. The compound is fed to the reactor, the mixed compound is continuously stirred in the reactor, and a gas body rich in air or oxygen is flowed into the reactor and is in the range of about 650 ° C. to about 800 ° C. By heating the reacted product at a temperature for no more than about 4 hours, and preferably cooling the reacted product under conditions of no more than about 100 ° C. for no more than 2 hours, 0 ≦ X ≦ 0.125 A process for continuously producing a single-phase lithiated manganese oxide intercalation compound of the formula Li _{1 + x} Mn _2−x O ₄ is described.
Patent Document 1 also synthesizes a substantially single-phase lithium manganese oxide having a cubic spinel crystal structure having a chemical formula of Li _{1 + x} Mn _2−x O ₄ and 0 ≦ X ≦ 0.125. It also describes how to do it.

Japanese Patent No. 4074662

By the way, when firing a positive electrode material for a secondary battery, thermal efficiency is improved by using a continuous heating furnace such as a rotary kiln rather than a batch heating furnace such as a roller hearth kiln or a busher furnace currently used. It is considered that the firing time can be shortened. However, when a continuous heating furnace is used, adhesion and growth of raw materials occur in the heating furnace, making it difficult to industrially perform continuous firing.

An object of the present invention is to provide a method for producing a positive electrode material for a secondary battery that eliminates the problems based on the above-described conventional technology and has excellent production efficiency.

In order to achieve the above object, the present invention is a method for producing a positive electrode material for a secondary battery, and a mixed powder is obtained by mixing a raw material lithium compound powder and a metal compound powder, The step of granulating the mixed powder to obtain a granulated powder, and the granulated powder is continuously baked and reacted at a predetermined temperature and time, whereby a composite oxide of lithium and metal is recharged. And a process for obtaining a positive electrode material for a secondary battery.

The particle size composition of the granulated powder in the present invention is desirably 40% by mass or less, preferably 25% by mass or less, and more preferably 20% by mass or less when the particle size is less than 250 μm.

In the present invention, it is preferable that a rotary kiln is used in the step of continuously firing the granulated powder at a predetermined temperature.
In the present invention, the lithium compound is, for example, LiOH, Li ₂ O, or Li ₂ CO ₃ , and the metal compound is, for example, MnO, MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ , It is MnCO ₃ , CoO, CoCO ₃ , Co ₃ CO ₄ , NiO, or Ni (OH) ₃ , and the composite oxide is preferably LiMn ₂ O ₄ , LiCoO ₂ , or LiNiO ₂ , for example.

According to the present invention, by using a granulated powder of a lithium compound and a metal compound, the granulated powder does not adhere to the rotary kiln during the firing and does not clog, etc., and continuously with high production efficiency. A positive electrode material for a secondary battery can be produced.
Moreover, according to this invention, the positive electrode material for secondary batteries can be manufactured continuously more efficiently by manufacturing using a rotary kiln.

It is a schematic diagram which shows the rotary kiln used for the manufacturing method of the positive electrode material for secondary batteries of this invention. (A) is a schematic diagram which shows the granulator used for the manufacturing method of the positive electrode material for secondary batteries of this invention, (B) is used for the manufacturing method of the positive electrode material for secondary batteries of this invention. It is a top view which shows a granulator.

Hereinafter, a method for producing a positive electrode material for a secondary battery of the present invention will be described in detail based on embodiments shown in the accompanying drawings.

In the conventional method for producing a positive electrode material for a lithium ion secondary battery, a solid-phase reaction in a mixed raw material of a lithium compound and a compound such as an oxide such as nickel, manganese, cobalt, or a hydroxide is used. The reactant remained and could not be produced with high efficiency.
In addition, when a mixed powder obtained by mixing Li ₂ CO ₃ powder and MnO ₂ powder, which are raw materials for a positive electrode material for a secondary battery, is continuously fired and reacted using a rotary kiln, the mixed powder is 6 kg / hour. The theoretical recovery amount of LiMn ₂ O ₄ obtained by firing is 5.25 kg / hour, but when this mixed powder is actually fired, the yield is 17 after 20 minutes from the start of firing. After 40 minutes from the start of firing, the yield decreases to 11%, and after 60 minutes from the start of firing, the yield is 0%, that is, the fired body adheres to the rotary kiln and grows to block the rotary kiln. As a result, it was found that the fired body could not be recovered.
In this way, using a mixed powder obtained by mixing a powder of Li ₂ CO ₃ (lithium compound) and a powder of MnO ₂ (metal compound), the mixture is continuously fired and reacted using a rotary kiln, and used for a secondary battery. When LiMn ₂ O ₄ (composite oxide) was obtained as the positive electrode material, it was found that the rotary kiln was blocked and could not be continuously fired.

The present invention has been made on the basis of the above knowledge. Specifically, a lithium compound powder as a raw material and a metal compound powder are mixed to obtain a mixed powder. By using the granulated powder that has been granulated, the rotary kiln can be continuously fired with high production efficiency without clogging. Thereby, the positive electrode material for secondary batteries can be obtained.

In particular, the particle size composition of the granulated powder in the present invention is desirably 40% by mass or less, preferably 25% by mass or less, more preferably 20% by mass or less when the particle size is less than 250 μm.
On the other hand, when the particle size composition of the granulated powder exceeds 40% by mass when the particle size is less than 250 μm, the amount of fine powder increases. For example, using a rotary kiln, a lithium compound powder and a metal compound powder are mixed. When a composite oxide is obtained as a positive electrode material for a secondary battery by firing and reacting, the rotary kiln is blocked and cannot be fired continuously.
Here, the maximum particle size of the granulated powder is determined by whether or not the granulated powder is appropriately fired and reacted in the rotary kiln, but the degree of firing and reaction depends on the raw material particle size before mixing. The maximum particle size of the granulated powder cannot be generally defined because it depends on the firing temperature and the like. Therefore, using the fact that approximately 5% of the cross-sectional area of the rotary kiln is the upper limit of the layer thickness of the workpiece, 30 mm is converted into a granulated powder by converting from the cross-sectional area of the industrial rotary kiln. It is appropriate to set the maximum particle size. If the maximum particle size of the granulated powder exceeds 30 mm, the firing / reaction does not proceed properly and a desired fired product cannot be obtained.

In the present invention, a lithium compound, for example, LiOH, a _Li 2 O or _Li 2 CO _3,, metal compounds, for _{example, MnO, MnO 2, Mn 2} O 3, Mn 3 O 4, MnCO 3 , CoO, CoCO ₃ , Co ₃ CO ₄ , NiO, or Ni (OH) ₃ . Examples of the composite oxide obtained as the positive electrode material for the secondary battery include LiMn ₂ O ₄ , LiCoO ₂ , and LiNiO ₂ .

In the method for producing a positive electrode material for a secondary battery containing lithium according to this embodiment, the rotary kiln 10 shown in FIG. 1 can be used, for example, firing under conditions of a firing temperature of 800 ° C. and a firing time of 60 minutes. It is preferable that the temperature raising time up to 800 ° C. is 40 minutes and the holding time at 800 ° C. is 20 minutes.

A rotary kiln 10 shown in FIG. 1 includes a ceramic cylindrical portion 12 that is fired in an interior 12a thereof, a heating element 14 that is provided so as to cover the outer surface 12b of the cylindrical portion 12 with a predetermined distance, and a cylinder. A driving unit (not shown) that rotates the unit 12 around the axis thereof as a rotation axis, and a control unit that controls heating of the cylindrical part 12 by the heating element 14 and rotation by the driving part of the cylindrical part 12.

The cylindrical part 12 is heated by the heating element 14, heated to a predetermined temperature, for example, 800 ° C., and the granulated powder 16 to be fired is supplied to the inside 12 a of the cylindrical part 12. Then, the cylinder unit 12 is rotated by the drive unit, and the granulated powder 16 is moved from the supply port 13a to the discharge port 13b of the cylinder unit 12 over a predetermined time, while MnO ₂ powder and Li Firing and reacting with ₂ CO ₃ powder. Thereby, a sintered body of LiMn ₂ O ₄ is obtained as a positive electrode material for a secondary battery. The obtained LiMn ₂ O ₄ fired body is discharged from the discharge port 13b.
In addition, the movement time from the supply port 13a of the cylinder part 12 of the granulated powder 16 to the discharge port 13b is baking time.

Next, the fired body of LiMn ₂ O ₄ is pulverized using a pulverizer such as a super jet mill (manufactured by Nisshin Engineering Co., Ltd.), and further, a classifier such as a turbo classifier (manufactured by Nisshin Engineering Co., Ltd.). ) Or aero fine classifier (manufactured by Nissin Engineering Co., Ltd.). Thereby, the positive electrode material for secondary batteries provided with a predetermined particle diameter can be obtained.

In the present embodiment, the granulated powder 16 is obtained as follows. First, for example, by using a granulator 20 shown in FIGS. 2A and 2B, a mixed powder 26 obtained by mixing MnO ₂ powder and Li ₂ CO ₃ powder is granulated and granulated. Processed into granules 28. Here, when the particle size composition of the granulated product 28 is 40% by mass or less, preferably 25% by mass or less, more preferably 20% by mass or less, that having a particle size of less than 250 μm, the granulated product 28 is granulated as it is. The powder 16 is supplied to the inside 12 a of the cylindrical portion 12 of the rotary kiln 10. Further, when a granulated product having a predetermined particle size cannot be obtained only by the granulating operation, the granulated product 28 is pulverized using a pulverizer (not shown) or a granulator (see FIG. The granulated powder 16 adjusted to have a desired particle size configuration can be obtained by sizing the particles by a not-shown method. This granulated powder 16 is supplied to the inside 12 a of the cylindrical portion 12 of the rotary kiln 10.

The granulator 20 shown in FIGS. 2A and 2B includes a roll pair 22 and a rotation drive unit (not shown) that rotates the rolls 22 a and 22 b of the roll pair 22. In the roll pair 22, a gap 24 is provided between the rolls 22a and 22b, and the roll 22a is pressed in the direction of the roll 22b. A plurality of grooves (lateral grooves) extending in the axial direction are formed in parallel on the surface of each roll 22a, 22b. Each roll 22a, 22b is rotated so as to move the mixed powder 26 from above the gap 24 to below. Accordingly, when a mixed powder 26 of MnO ₂ powder and Li ₂ CO ₃ powder is supplied from above the roll pair 22, the mixture is granulated through the gap 24 to form a granulated product 28.

Thus, in this embodiment, by using the granulated powder 16, for example, even if a rotary kiln is used, the positive electrode material for a secondary battery can be obtained with high production efficiency without being blocked. Can do.
In addition, it may replace with the granulator 20 shown to FIG. 2 (A), (B), and may use a grinder, a granulator, or a dry-type compression granulator (not shown).

In addition, in this embodiment, if the granulated powder 16 can be obtained, it is not limited to using the granulator 20 shown to FIG. 2 (A) and (B). For example, the granulated powder 16 may be obtained using a rolling granulator or a spray dryer.
Furthermore, a binder may be added to the MnO ₂ powder and the Li ₂ CO ₃ powder to facilitate granulation.

As mentioned above, although the manufacturing method of the positive electrode material for secondary batteries of this invention was demonstrated in detail, this invention is not limited to the said embodiment, In the range which does not deviate from the main point of this invention, various improvement or a change is carried out. Of course it is also good.

Hereinafter, the Example of the manufacturing method of the positive electrode material for secondary batteries of this invention is described concretely.
In the present embodiment, by using the average particle diameter _{D 50} of 4μm of _Li 2 CO ₃ powder, and an average particle diameter _{D 50} of MnO ₂ of 27μm powder, granulated by a granulator, Table create a granulated powder of the granulated powders and experiment 3 of experimental example 2 shown in 1, likewise, the mean particle size _{D 50} average particle diameter _{D 50} of the powder of 4μm of _Li 2 CO ₃ is 4μm of Using the mixed powder with MnO ₂ , granulated powder of Experimental Example 1 shown in Table 1 below was prepared. The granulation conditions are as follows.

Granulation conditions Granulator: Roller compactor WP type (Turbo Kogyo Co., Ltd.)
Roll gap: 0.5mm (during initial idle operation)
Roll diameter: 160 mm x 2 roll surface condition: lateral groove + twill groove Roll linear pressure: 0.4 to 2.0 tons / cm
Roll rotation speed: 12rpm
Powder supply rate: 60-90kg / hour

Using each granulated powder as a raw material, a rotary kiln shown in FIG. 1 was used to produce a sintered body of LiMn ₂ O ₄ as a positive electrode material for a secondary battery.
In addition, in the particle size distribution shown in Table 1 below, four types of sieves having openings of 2 mm, 1 mm, 0.5 mm, and 0.25 mm were laminated in the order of openings of 2 mm, 1 mm, 0.5 mm, and 0.25 mm. It is obtained by measuring the mass of the powder on each sieve when the granulated product is sieved in order from above.

During firing, the case where the rotary kiln was not blocked was evaluated as “◯”, and the case where the rotary kiln was blocked was evaluated as “x”. The results are shown in the “continuity” column of Table 1 below.
The firing conditions were a firing temperature of 800 ° C. and a residence time in the rotary kiln of 20 minutes.

As shown in Table 1 above, Experimental Example 1 and Experimental Example 2 in which the content of less than 0.25 mm (250 μm) is less than 21% by mass are continuously used for secondary batteries without the rotary kiln being blocked. A positive electrode material could be obtained.
On the other hand, in Experimental Example 3 in which the content of less than 0.25 mm (250 μm) exceeds 40% by mass, the rotary kiln is blocked during firing, and a positive electrode material for a secondary battery cannot be obtained continuously. It was.

DESCRIPTION OF SYMBOLS 10 Rotary kiln 12 Cylinder 14 Heating body 16 Granulated powder 20 Granulator 22 Roll pair 22a, 22b Roll 24 Crevice 26 Mixed powder 28 Granulated product

Claims (4)

A method for producing a positive electrode material for a secondary battery, comprising:
Mixing a lithium compound powder as a raw material and a metal compound powder to obtain a mixed powder, and granulating the mixed powder to obtain a granulated powder;
A step of obtaining a composite oxide of lithium and metal as a positive electrode material for a secondary battery by continuously firing and reacting the granulated powder at a predetermined temperature and time. For producing a positive electrode material. The method for producing a positive electrode material for a secondary battery according to claim 1, wherein the granulated powder has a particle size composition of 40% by mass or less when the particle size is less than 250 µm. The method for producing a positive electrode material for a secondary battery according to claim 1 or 2, wherein a rotary kiln is used in the step of continuously firing the granulated powder at a predetermined temperature. The lithium compound is LiOH, Li ₂ O, or Li ₂ CO ₃ , and the metal compound is MnO, MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ , MnCO ₃ , CoO, CoCO ₃ , Co ₃ CO _4, NiO is or Ni _{(OH) 3,,} the composite oxide, the positive electrode material for a secondary battery according to any one of claims 1 to 3, which is _{LiMn 2 O 4, LiCoO 2,} LiNiO 2 Manufacturing method.

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