Effects of Si doping on structural and electrochemical performance of LiNi0.5Mn1.5O4 cathode materials for lithium-ion batteries

LiNi0.5Mn1.5O4 spinels were prepared by coprecipitation-hydrothermal method followed by high-temperature calcination. Si doping was achieved by acetic acid glacial-assisted sol-gel method using TEOS as Si source. The effect of Si doping contents on the structure, morphology and electrochemical performance of LiNi0.5Mn1.5O4 material was investigated. Si doping can inhibit the formation of LixNi1-xO impurity, but excessive Si doping results in the appearance of Li2SiO3 secondary phase. Si doping can reduce particle size and improve distribution. Electrochemical tests show that Si doping has a positive impact on rate and cycling performances, due to the increased structural stability resulting from stronger SiO bond, and the enhanced Li+ ion diffusion coefficient. Post-mortem analysis shows that Si doping can mitigate the transition metal dissolution and side reactions, thus leading to the enhanced electrochemical performance of Si-doped samples. Among them, LiNi0.5Mn1.5O4 with 6% Si doping exhibits the optimal electrochemical performance.