Phosphorus and Boron Co-Doped Carbon Coating of LiNi0.5Mn1.5O4 Cathodes for Advanced Lithium-ion Batteries

A facile approach for the preparation of phosphorus and boron co-doped carbon coated LiNi0.5Mn1.5O4, which is then applied as cathode materials for lithium ion batteries has been investigated. The effect of carbon coating amounts on the battery performance has been studied systematically. The 5 wt.% carbon coated sample exhibits the most outstanding performance, including an excellent capacity retention of 96.7% after 200 cycles, superior rate capability (111 mAhg(-1) capacity at 5 C), and significantly improved cycle life under 1 C. It is believed that the phosphorus and boron co-doped carbon coating layer could suppress side-reactions between the electrolyte and LiNi0.5Mn1.5O4, and alleviate the dissolution of manganese ions into the electrolyte effectively. Moreover, electrochemical impedance spectroscopy results reveal that the phosphorus and boron co-doped carbon coating on LiNi0.5Mn1.5O4 could reduce the charge transfer resistance significantly. The composite cathode therefore provides good conductivity as well as fast Li-ion diffusion, then resulting in better rate capability and cycle life, even under a high temperature of 55 degrees C.