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

Abstract

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 Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ 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 Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ 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.

Keywords: Cr doping; Cycle stability; Li(3)PO(4) coating; Lithium-rich cathodes; Voltage decay.