KR-102965077-B1 - CATHODE ACTIVE MATERIAL MIXING METHOD

Abstract

A method for mixing a positive electrode active material is introduced, characterized by comprising: a preparation step of preparing a lithium compound removal solution by mixing PAA (Poly acrylic acid) in a solvent in the process of manufacturing a positive electrode of a lithium secondary battery; a removal step of removing a lithium compound present on the surface of a positive electrode active material by reacting the lithium compound removal solution with the positive electrode active material present on the surface of the positive electrode active material; and a mixing step of mixing the positive electrode active material mixed with the lithium compound removal solution with a conductive material and a binder.

Inventors

• 박상목
• 오승민
• 진우영
• 이지은
• 이상훈
• 김고은
• 이준기
• 이윤성

Assignees

• 현대자동차주식회사
• 기아 주식회사

Dates

Publication Date

20260513

Application Date

20201112

Claims (9)

1. In the process of manufacturing the positive electrode of a lithium secondary battery, A preparation step for preparing a lithium compound removal solution by mixing PAA (Poly acrylic acid) with a solvent; A removal step of removing a lithium compound present on the surface of a positive electrode active material by reacting the above lithium compound removal solution with the positive electrode active material present on the surface of the lithium compound; A reaction maintenance step of maintaining the reaction for at least 20 minutes so that LiOH present in the cathode active material and PAA can react to produce Li-PAA; A drying step for drying the solution to remove H2O generated by the reaction of LiOH and PAA in the above removal step and above reaction maintenance step; and A method for mixing a positive electrode active material, characterized by including a mixing step of mixing the positive electrode active material mixed with the above lithium compound removal solution with a conductive material and a binder.
2. In claim 1, A method for mixing a positive electrode active material characterized in that the lithium compound in the above preparation step is LiOH.
3. delete
4. delete
5. In claim 1, A method for mixing a cathode active material , characterized in that the solvent comprises one or more of CH₃OH , CH₃CH₂OHH , CH₃CH (OH) CH₃ , H₂O , NMP, DMSO, DMF, Hexane, and THF.
6. In claim 1, A method for mixing cathode active materials characterized by the average molecular weight of the PAA used in the above removal step being 100,000 to 4,000,000.
7. In claim 2, A method for mixing a positive electrode active material, characterized in that the content of LiOH present on the surface of the positive electrode active material mixed with the lithium compound removal solution in the above removal step is 0.05 to 1.5 wt% of the mass of the positive electrode active material.
8. In claim 1, A method for mixing a positive electrode active material, characterized in that, in the above preparation step, the PAA is 20 to 300 wt% of the mass of LiOH in the positive electrode active material.
9. A cathode comprising a cathode active material manufactured through the cathode active material mixing method according to claim 1; cathode; A separator interposed between the anode and the cathode; and A lithium secondary battery characterized by including an electrolyte.

Description

Cathode Active Material Mixing Method The present invention relates to a mixing process of a positive electrode active material in an electrode manufacturing process during the manufacturing process of a lithium secondary battery. The manufacturing process of lithium secondary batteries can be broadly divided into three stages: the electrode process, the assembly process, and the formation process. The electrode process involves making electrodes, while the assembly process involves attaching tabs to the made electrodes, inserting separators to produce jelly rolls, and injecting electrolyte. The formation process involves activating the battery and inspecting and sorting for defects in the manufactured secondary batteries. In the battery activation process, the assembled batteries are charged, discharged, and aged to stabilize the battery structure and make them ready for use. The present invention relates to a method for mixing a positive electrode active material performed in the electrode process during the above process. In response to the demand for higher energy and lower cost of battery cells, it is necessary to increase the proportion of Ni in the components of the cathode active material. Generally, when the proportion of Ni in the cathode active material increases, the amount of residual Li on the surface of the active material increases depending on the synthesis conditions and raw material composition. If the residual lithium exceeds a certain level, there are problems such as difficulty in proceeding with the process due to changes in the physical properties of the slurry during the electrode mixing process, or increased gas generation after battery manufacturing, which prevent the battery from performing properly. To solve these problems, methods such as adding washing and heat treatment processes during active material manufacturing or controlling moisture during the mixing process are being used, but this leads to problems such as increased production costs of active materials and increased costs of the electrode manufacturing process. The matters described above as background technology are intended only to enhance understanding of the background of the present invention and should not be construed as an acknowledgment that they constitute prior art already known to those skilled in the art. Figure 1 shows a flowchart of a method for mixing a positive electrode active material according to one embodiment of the present invention. FIG. 2a is a graph showing the change in slurry properties according to an embodiment and a comparative example of the present invention. FIG. 2b is a photograph for comparing the fluidity of slurries according to an embodiment and a comparative example of the present invention after being left for 10 days. Figure 3 is a graph showing the cycle characteristics of a battery with a positive electrode active material according to an embodiment and a comparative example of the present invention. Hereinafter, embodiments of the present invention will be described in more detail with reference to the attached drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms, and these embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention. FIG. 1 is a flowchart of a method for mixing a positive electrode active material according to an embodiment of the present invention, FIG. 2a is a graph showing changes in slurry physical properties according to an embodiment and a comparative example of the present invention, FIG. 2b is a photograph for comparing fluidity after leaving the slurry according to an embodiment and a comparative example of the present invention for 10 days, and FIG. 3 is a graph showing the cycle characteristics of a battery to which the positive electrode active material according to an embodiment and a comparative example of the present invention is applied. The manufacturing process of a lithium secondary battery can be broadly classified into electrode, assembly, and formation processes, and the electrode process can be further divided into mixing, coating, pressing, slitting, and drying processes. The mixing process is a process of preparing a slurry by mixing an active material, a binder, and a conductive material. Specifically, a solution is prepared by dissolving the binder in a solvent, and the active material and conductive material are mixed with the solution to prepare a slurry. After preparing the slurry, storage and transfer of the slurry take place, and the prepared slurry is stored in a slurry storage tank until it is coated. In the above mixing process, Pvdf (polyvinylidene fluoride) is mainly used as the binder, and NMP (N-methyl pyrrolidone) is mainly used as the solvent. The structure of Pvdf is as follows. Pvdf has a problem in that when an alk