Recent advances in surface coating and atomic doping strategies for lithium-ion battery cathodes: implementation approaches and functional mechanisms

Lithium-ion batteries (LIBs) have become a dominant energy storage method for electronic portable devices and electric vehicles due to their fascinating properties of superior energy density, potential, and lifespan. To further improve the capability of commercial LIBs, great efforts have been continuously made to optimize the structural and electrochemical properties of cathode materials which mainly determine the performance and account for about half the cost of LIBs. By extensively summarizing the recent literature, the two most effective and robust strategies for enhancing the comprehensive performance of representative cathode materials (e.g., LiCoO₂, LiNiO₂, LiNi_xCo_yMn_zO₂ (x + y + z = 1), LiNi_xCo_yAl_zO₂ (x + y + z = 1), and LiFePO₄) are presented, that is, surface coating and atomic doping. The detailed implementation approaches and functional mechanisms of various coated materials and doped elements for the cycling and rate performance enhancement of cathode materials are systematically introduced and in depth discussed. The surface coating can primarily inhibit the interfacial oxidation of electrolyte by cathode materials, and improve the cycle life, conductivity, safety, and so on. The atomic doping can effectively enhance the lattice stability, phase conversion reversibility, electron/ion transmission rate, and electrochemical kinetics. The integrated application of the above two strategies could create synergistic effects that significantly improve the electrochemical performance of various cathodes. Finally, a perspective on the future prospect of the rational structural and componential designs of various cathode materials for next-generation high-performance and low-cost LIBs is highlighted.