Recent progress on the modification of high nickel content NCM: Coating, doping, and single crystallization

Abstract

Abstract High nickel content layered cathodes, represented by NCM (LiNixCoyMnzO2, x + y + z = 1), are now widely employed in the market of electric vehicles, owing to their high energy density. With the gradual increase of nickel content and capacity, the issues on cycling life and safety become more serious. In this review, various strategies for improving the performance of high nickel NCM are summarized on the aspects of surface coating, ionic doping, and single‐crystal NCM. The coating strategy was separately described according to the physical property of coating species, including inert material coating, Li+‐conductor coating, electronic conductor coating, and mixed conductor coating. These coating species help to suppress the interfacial oxidation of electrolytes by NCM, improving the cycling life and safety. The elemental doping in the crystal lattice of NCM is then presented in the aspects of cation, anion, and mixed‐ion doping, which are beneficial to stabilize the layered structure during charge–discharge and so promote the electrochemical performance. In quite recent years, the strategy of single‐crystal NCM was demonstrated to be a promising pathway, owing to the dramatically reduced surface area and grain boundary. Finally, the remaining unsolved challenges and future strategies for further development of NCM cathode materials are outlined.

Keywords

• coating
• doping
• high nickel NCM
• layered cathode
• lithium‐ion batteries