Improving electrochemical performances of Lithium-rich oxide by cooperatively doping Cr and coating Li3PO4 as cathode material for Lithium-ion batteries

Lithium-rich layered oxides exhibit one of the highest reversible discharge capacities among cathode materials for lithium-ion batteries. However, their voltage decay and poor cycle stability severely restrict their use as a commercial cathode material. In this work, a novel approach of that combines Cr doping and a Li3PO4 coating was designed to address the problems associated with lithium-rich Li1.2Mn0.54Ni0.13Co0.13O2 materials. The synergistic method not only increases the discharge capacity and cycle stability but also decreases the voltage decay. The 1.0 wt% Li3PO4 coating and 0.08 Cr doping on Li1.2Mn0.54Ni0.13Co0.13O2 cathode shows a capacity retention of 76.5% compared to the 59.0% capacity retention for the pristine electrode after 200 cycles. The initial discharge capacity is also increased from 255.8 mAh·g-1 to 265.2 mAh·g-1. In addition, the discharge voltage decay decreases from 0.84 V to 0.39 V after 200 cycles as a result of the Cr doping and Li3PO4 coating. These enhanced electrochemical properties are attributed to the fact that the Cr doping stabilized the layered structure and inhibited its phase transformation to the spinel phase, and the Li3PO4 coating confined the interfacial side reactions between the electrode and electrolyte. This work may provide a new method to solve the subsistent problems of lithium-rich cathode materials.