Structural stability and redox activity modulation of O3-type layered transition metal oxides by lithium-ion doping for high-performance sodium-ion batteries

The exploration of cathode materials with stable sodium storage capacity is an important step toward commercializing sodium-ion batteries. Layered oxides are considered ideal cathode materials for sodium-ion batteries due to their high theoretical capacity and low cost. However, harmful phase transitions during charging/discharging and transition metal ion dissolution in layered oxides lead to poor cycling stability and rate performance. To address the problems of layered oxides as electrode materials, in this paper, Na_1.0Cu_0.20Fe_0.30Mn_0.5-xLi_xO₂ (x = 0, 0.025, 0.05, 0.075) materials were prepared by using the lithium-ion doping strategy using a solid-phase heating method, which could effectively prevent the Jahn–Teller effect and transition metal ion dissolution. The Li-ion doped modified material exhibits a higher capacity of 110 mAh g⁻¹ at 0.5 C and excellent cycling stability with about 85% capacity retention after 400 cycles at 0.5 C. This work proposes a strategy of design of O3-type layered transition metal oxide cathodes with a high energy efficiency.