A review of research progress on the modification of nickel-rich NCM cathode materials
A review of research progress on the modification of nickel-rich NCM cathode materials
Nickel-rich NCM materials are currently one of the cathode materials for high-energy density lithium-ion batteries. Nickel-rich NCM cathode materials include nickel-rich lithium nickel cobalt manganese (LiNixCoyMnzO2) and lithium nickel cobalt aluminate (LiNixCoyAlzO2) materials, and their nickel content is generally greater than 50%.
Unstable surface and interface properties, structural defects, irreversible phase transitions and the thermodynamic instability caused by them have always been problems to be solved in nickel-rich NCM cathode materials.
Figure 1: Phosphate and manganese ion co-doped nickel-rich NCM cathode material
This article summarizes some advanced modification strategies:
1) By adjusting the precipitation rate of the coating material, the thickness and uniformity of the coating layer can be precisely controlled, and the uniform coating of the nickel-rich NCM material on the primary particles can be realized.
2) The introduction of high-valent metal ions, such as Nb5+, Zr4+, Ti4+, Mo6+, W6+, etc., the structure has a composite structure of rock salt phase or spinel phase and layered phase.
3)Increase the ratio of trivalent nickel ions in nickel-cobalt-aluminum or nickel-cobalt-manganese materials by surface oxidation or doping with low-valent metal ions, and then study the relationship between the ratio of Ni3+/Ni2+ and the crystal structure and electrical properties .
In addition, it is also necessary to further study and understand the changes in the surface composition, microstructure and electrochemical behavior of materials during the electrochemical process, and to select and design dopants and doping sites reasonably.
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