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　　The latest research progress of nickel-cobalt-manganese ternary materials for lithium batteries

　　Nickel-cobalt-manganese ternary materials are a new type of lithium-ion battery cathode materials developed in recent years. They have important advantages such as high capacity, good cycle stability, and moderate cost. Because this type of material can effectively overcome the high cost of lithium cobalt oxide materials at the same time , low stability of lithium manganese oxide material, low capacity of lithium iron phosphate, etc., have been successfully applied in batteries, and the application scale has been developed rapidly.

　　Nickel-cobalt-manganese ternary materials are a new type of lithium-ion battery cathode materials developed in recent years. They have important advantages such as high capacity, good cycle stability, and moderate cost. Because this type of material can effectively overcome the high cost of lithium cobalt oxide materials at the same time , low stability of lithium manganese oxide material, low capacity of lithium iron phosphate, etc., have been successfully applied in batteries, and the application scale has been developed rapidly.

　　According to the disclosure, in 2014, the output value of China's lithium-ion battery cathode materials reached 9.575 billion yuan, of which ternary materials were 2.74 billion yuan, accounting for 28.6%; in the field of power batteries, ternary materials are rising strongly, and the BAIC EV200 launched in 2014 , Chery eQ, JAC iEV4, Zotye Cloud 100, etc. all use ternary power batteries.

　　At the 2015 Shanghai International Auto Show, in new energy vehicles, the share of ternary lithium batteries surpassed that of lithium iron phosphate batteries and became a highlight. Most domestic mainstream car companies, including Geely, Chery, Changan, Zotye, and Zhonghua, launched their products one after another. A new energy model using a ternary power battery. Many experts predict that ternary materials are expected to replace expensive lithium cobalt oxide materials in the near future due to their excellent performance and reasonable manufacturing costs.

　　It has been found that the ratio of nickel-cobalt-manganese in the nickel-cobalt-manganese ternary cathode material can be adjusted within a certain range, and its performance varies with the ratio of nickel-cobalt-manganese. Therefore, in order to further reduce high-cost transition metals such as cobalt and nickel content, and the purpose of further improving the performance of positive electrode materials; countries all over the world have done a lot of work in the research and development of ternary materials with different nickel-cobalt-manganese compositions, and have proposed multiple compositions with different nickel-cobalt-manganese ratios. Ternary material system. Including 333, 523, 811 systems, etc. Some systems have been successfully industrialized and applied.

　　This article will systematically introduce the latest research progress and achievements of several major nickel-cobalt-manganese ternary materials in recent years, as well as some research progress in doping and coating to improve the performance of these materials.

　　1 Structural characteristics of nickel-cobalt-manganese ternary cathode materials

　　Nickel-cobalt-manganese ternary materials can usually be expressed as: LiNixCoyMnzO2, where x+y+z=1; they are called different systems according to the molar ratio (x:y:z ratio) of the three elements, such as A ternary material with a nickel-cobalt-manganese molar ratio (x:y:z) of 1:1:1 in the composition is referred to as type 333. A system with a molar ratio of 5:2:3 is called the 523 system, etc.

　　Ternary materials such as Type 333, Type 523 and Type 811 all belong to the hexagonal α-NaFeO2 layered rock salt structure, as shown in Figure 1.

　　In nickel-cobalt-manganese ternary materials, the main valence states of the three elements are +2, +3 and +4 respectively, and Ni is the main active element. The reaction and charge transfer during charging are shown in Figure 2.

　　Generally speaking, the higher the content of active metal components, the greater the capacity of the material, but when the content of nickel is too high, it will cause Ni2+ to occupy the Li+ site, which intensifies the cation mixing, resulting in a decrease in capacity. Co can just inhibit cation mixing and stabilize the layered structure of the material; Mn4+ does not participate in electrochemical reactions, which can provide safety and stability while reducing costs.