METHOD FOR PREPARING SECONDARY BATTERY CATHODE MATERIAL

Abstract

A method of manufacturing a secondary battery cathode material includes preparing Li.sub.2O powder by separating CO.sub.2 from Li.sub.2CO.sub.3 powder, forming a mixed powder by mixing the Li.sub.2O powder with nickel-cobalt-manganese (NCM) precursor powder, and firing the mixed powder using a rotary kiln.

Claims

1. A method of manufacturing a secondary battery cathode material, comprising: preparing Li.sub.2O powder by separating CO.sub.2 from Li.sub.2CO.sub.3 powder; forming a mixed powder by mixing the Li.sub.2O powder with nickel-cobalt-manganese (NCM) precursor powder; and firing the mixed powder using a rotary kiln.

2. The method of claim 1, wherein: the preparing of the Li.sub.2O powder includes: charging the Li.sub.2CO.sub.3 powder into a firing furnace in a high-temperature atmosphere; and separating the CO.sub.2 from the Li.sub.2CO.sub.3 powder by supplying air or oxygen into the firing furnace.

3. The method of claim 1, wherein: the forming of the mixed powder includes: pulverizing the Li.sub.2O powder; and mixing the Li.sub.2O powder with the NCM precursor powder; and forming the mixed powder in a form of granules or briquettes.

4. The method of claim 1, wherein: the forming of the mixed powder may be performed in a closed space in a nitrogen atmosphere.

5. The method of claim 1, wherein: the firing of the mixed powder using the rotary kiln includes: charging the mixed powder into an inside of the rotary kiln in a high-temperature atmosphere in which a refractory coating layer is formed on an inner surface of the rotary kiln and a spiral baffle is installed in the rotary kiln; and firing the mixed powder inside the rotary kiln.

Description

DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is a flowchart illustrating a method of manufacturing a secondary battery cathode material according to an exemplary embodiment.

[0015] FIG. 2 is a diagram illustrating a rotary kiln used for the method of manufacturing a secondary battery cathode material.

MODE FOR INVENTION

[0016] The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

[0017] Portions unrelated to the description will be omitted in order to obviously describe the present invention, and similar components will be denoted by the same or similar reference numerals throughout the present specification.

[0018] In addition, unless explicitly described to the contrary, the word “comprise”, and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of stated elements but not the exclusion of any other elements.

[0019] Hereinafter, a method of manufacturing a secondary battery cathode material according to an exemplary embodiment will be described with reference to FIGS. 1 and 2.

[0020] FIG. 1 is a flowchart illustrating a method of manufacturing a secondary battery cathode material according to an exemplary embodiment.

[0021] Referring to FIG. 1, first, CO.sub.2 is separated from Li.sub.2CO.sub.3 powder to prepare Li.sub.2O powder (S100).

[0022] Specifically, Li.sub.2CO.sub.3 powder, which has a lower price than LiOH powder, is charged into the firing furnace in a high-temperature atmosphere, and air or oxygen (O.sub.2) gas is supplied into the firing furnace to separate CO.sub.2 gas from Li.sub.2CO.sub.3 powder to prepare Li.sub.2O powder.

[0023] Here, the firing furnace may be a rotary kiln, but is not limited thereto.

[0024] When air or oxygen gas is put into the Li.sub.2CO.sub.3 powder before firing, the Li.sub.2CO.sub.3 powder reacts with oxygen in the air or oxygen in the oxygen gas in a high-temperature atmosphere to be converted into Li.sub.2O powder, and the reactant is carbon dioxide (CO.sub.2) gas. In this case, since a reaction rate is determined by a partial pressure and temperature of carbon dioxide and oxygen, a certain amount of carbon dioxide gas may be discharged while supplying air or oxygen gas to keep the process temperature constant at 400° C. to 800° C., and to maintain a constant partial pressure.

[0025] Next, the Li.sub.2O powder is mixed with a nickel-cobalt-manganese (NCM) precursor powder to form a mixed powder (S200).

[0026] Specifically, the Li.sub.2O powder is pulverized, the Li.sub.2O powder is mixed with the NCM precursor powder, and the mixed powder is formed into the form of granules or briquettes to form the mixed powder. All steps for forming the mixed powder may be performed in a closed space in a nitrogen atmosphere to prevent the Li.sub.2O powder from being reduced to Li.sub.2CO.sub.3 due to the reaction of the Li.sub.2O powder with CO.sub.2.

[0027] Here, the NCM precursor may include, but is not limited to, nickel-cobalt-manganese hydroxide [Ni.sub.aMn.sub.bCO.sub.c] (OH).sub.2.

[0028] After preparing the Li.sub.2O powder by separating CO.sub.2 from the Li.sub.2CO.sub.3 powder, aggregation occurs in a part of the Li.sub.2O powder and becomes a lumped state. In this state, when the Li.sub.2O powder is mixed with the nickel-cobalt-manganese (NCM) precursor powder, in the firing process, since it is difficult for the LiO.sub.2 of the Li.sub.2O powder to uniformly penetrate into the NCM precursor of the NCM precursor powder, the Li.sub.2O powder is pulverized.

[0029] The Li.sub.2O powder is pulverized, and then, mixed with the NCM precursor powder in a molar ratio of 1:1 or more.

[0030] In order to prevent the Li.sub.2O powder from being reduced back to lithium carbonate (Li.sub.2CO.sub.3) by reacting with carbon dioxide in the air at a high temperature, the above-described pulverizing and mixing are performed in the closed space in the nitrogen atmosphere.

[0031] After mixing the Li.sub.2O powder and the NCM precursor powder, the mixed powder in the form of granules or briquettes having a size of 1 mm to 100 mm is formed before being put into the rotary kiln. Unlike the conventional firing furnace, which is a roller hearth kiln (RHK) furnace using saggar, since a method of manufacturing a secondary battery cathode material according to an exemplary embodiment uses a firing furnace of a rotary kiln to fire a cathode material, the mixed powder is formed in the form of granules or briquettes, first-in and first-out are implemented inside the rotary kiln as the firing furnace, to minimize a deviation in firing time, prevent contamination by generation of a reactant inside the rotary kiln, and suppress a clinker from occurring inside the rotary kiln.

[0032] Next, the mixed powder is fired using the rotary kiln (S300).

[0033] FIG. 2 is a diagram illustrating the rotary kiln used for the method of manufacturing a secondary battery cathode material. FIG. 2A is a diagram illustrating the rotary kiln (RK) used for the method of manufacturing a secondary battery cathode material, FIG. 2B is a cross-sectional view illustrating a refractory coating layer (CL) formed on an inner surface (IW) of the rotary kiln (RK), and FIG. 2C is a photograph illustrating a spiral baffle (SB) provided inside the rotary kiln (RK).

[0034] Referring to FIG. 2, specifically, the mixed powder is charged into the rotary kiln (RK) in the high-temperature atmosphere in which the refractory coating layer (CL) is formed on the inner surface (IW) and the spiral baffle (SB) is provided inside the rotary kiln (RK), and the mixed powder is fired into the secondary battery cathode material, which is a cathode active material, inside the rotary kiln (RK).

[0035] The rotary kiln (RK) includes a raw material charging unit, a raw material discharge unit, a heating unit, and a cooling unit.

[0036] The mixed powder is charged into the inside of the rotary kiln (RK) through the raw material charging unit of the rotary kiln (RK), and the mixed powder charged into the rotary kiln (RK) is fired in the heating unit and cooled in the cooling unit, and is discharged to the outside through the raw material discharge unit of the rotary kiln (RK). The secondary battery cathode material, which is the cathode active material fired from the mixed powder inside the rotary kiln (RK), is discharged to the outside through the raw material discharge unit.

[0037] The mixed powder formed in the form of the briquettes or granules is put into the firing furnace, which is the rotary kiln (RK) having the spiral baffle (SB) provided inside thereof and the refractory coating layer (CL) without the saggar used in the conventional RHK furnace, in the nitrogen atmosphere. The rotary kiln (RK) rotates at a low speed and fires the mixed powder while maintaining a target firing temperature between 400° C. and 1000° C.

[0038] The inside of the heating unit of the rotary kiln (RK) may be controlled by being divided into a sequentially communicating temperature increase section, temperature maintenance section, and cooling section. The reason that the cooling section is required may be to prevent a secondary reaction and generation of residual lithium due to a sudden temperature change.

[0039] In the next step, the secondary battery cathode material, which is the cathode active material in the form of the briquettes or granules fired in the firing furnace which is the rotary kiln (RK), is pulverized, the pulverized cathode active material is classified, and the de-iron process is performed on the classified cathode active material. Thereafter, when there is a lot of residual lithium in the cathode active material, a washing and drying process is performed, and when the residual lithium in the cathode active material is within a standard value, finally, a process of packaging the cathode active material through coating and heat treatment without the washing and drying process may be performed.

[0040] The secondary battery cathode material, which is the cathode active material fired in the rotary kiln (RK), is a nickel-cobalt-manganese (NCM) cathode material of LiNi.sub.xMn.sub.yCO.sub.(1-x-y)O.sub.2, and a high nickel NCM cathode material having a nickel content of 70% or more.

[0041] In the conventional method of manufacturing a secondary battery cathode material, when manufacturing the high nickel NCM cathode material having a nickel content of 70% or more, in the case where the Li.sub.2CO.sub.3 is mixed with the NCM precursor, in order to solve the deterioration in properties of the cathode material due to the high firing temperature for reacting with O.sub.2, the LiOH was mixed with the NCM precursor and reacts with O.sub.2 at a low firing temperature.

[0042] However, the conventional method of manufacturing a secondary battery cathode material has a problem in that the manufacturing cost of the secondary battery cathode material increases because the price of LiOH is higher than that of Li.sub.2CO.sub.3.

[0043] To solve this problem, the method of manufacturing a secondary battery cathode material according to an exemplary embodiment manufactures the high nickel NCM cathode material having a nickel content of 70% or more while solving the deterioration in properties of the cathode material by not using LiOH and O.sub.2, converting Li.sub.2CO.sub.3 into Li.sub.2O and mixing the Li.sub.2O with the NCM precursor, and firing the mixture in the rotary kiln (RK) at a low firing temperature.

[0044] That is, the method of manufacturing a secondary battery cathode material capable of reducing manufacturing cost of the secondary battery cathode material by manufacturing a high nickel NCM cathode material having a nickel content of 70% or more even if Li.sub.2CO.sub.3 is used without using LiOH is provided.

[0045] In addition, the method of manufacturing a secondary battery cathode material capable of mass-producing the secondary battery cathode material by manufacturing the secondary battery cathode material using the rotary kiln (RK) is provided.

[0046] Although the exemplary embodiment of the present invention has been described in detail hereinabove, the scope of the present invention is not limited thereto. That is, several modifications and alterations made by a person of ordinary skill in the art using a basic concept of the present invention as defined in the claims fall within the scope of the present invention.

DESCRIPTION OF SYMBOLS

[0047] Rotary Kiln (RK), Refractory coating layer (CL), Spiral baffle (SB)