Optimization of structural stability of cathode materials by volume phase regulation

The rapid capacity decay of high-nickel (Ni≥90%) layered oxides during long cycling limits their commercial application. Doping has been widely studied as a method to improve the electrochemical properties of cathode materials. This study explored the position-specific introduction of magnesium ions (Mg²⁺) to improve the structural stability of LiNi_0.9Co_0.05Mn_0.05O₂ cathode materials. Experimental results showed that, in coin-type lithium-ion half-cells, Mg-doped cathode materials exhibited superior electrochemical performance compared to undoped materials. Notably, after 100 cycles at a rate of 0.5 C, the 0.3% Mg²⁺-doped LiNi_0.9Co_0.05Mn_0.05O₂ cathode material retained 74.06% of its initial specific capacity. Physical characterization and analysis revealed that the doping treatment changes the exposure and lattice structure of the active crystal surfaces of the materials, effectively suppressing cation mixing and unfavorable phase transitions, thereby enhancing the cycling stability of the material. These changes contribute to improved long-term cycling performance of the battery. The doping method proposed in this study effectively improves the performance of high-nickel cathode materials and provides guidelines for the development of higher energy density lithium-ion batteries (LIBs).