Improving the Electrochemical Performance of Co-Free Li-Rich Layered Oxides via a Dual Modification of Nb5+ Doping and Oxygen Vacancy Regulation

With the advantages of low cost and high energy density, Co-free Li-rich layered oxides (LROs) are a potential next-generation lithium-ion battery cathode material for energy vehicles. However, LROs suffer from the defects of irreversible O-redox and low conductivity, producing poor cycling stability and rate performance and low initial Coulombic efficiency (ICE). In this work, the ammonium niobium oxalate (C4H4NNbO9·nH2O) treatment strategy is proposed to realize oxygen vacancy construction and Nb5+ doping on the surface of the LRO material. The results show that the optimized sample LRO-Nb-0.5 presents satisfactory electrochemical performance; for example, at 1C, the specific discharge capacity is 209.77 mAh g–1 and a capacity retention rate is 93.22% after 300 cycles. In addition, the high-rate capability is distinctly enhanced; a specific discharge capacity of 178.70 mAh g–1 can be achieved at 5C for LRO-Nb-0.5. Therefore, Nb5+ doping and oxygen vacancy regulation can be significant explorations for the promotion of the electrochemical performance of Co-free Li-rich materials.