Designing a P2-type cathode material with Li in both Na and transition metal layers for Na-ion batteries

P2-type layered oxides have been considered as promising cathode materials for Na-ion batteries, but the capacity decay resulting from the Na⁺/vacancy ordering and phase transformation limits their future large-scale applications. Herein, the impact of Li-doping in different layers on the structure and electrochemical performance of P2-type Na_0.7Ni_0.35Mn_0.65O₂ is investigated. It can be found that Li ions successfully enter both the Na and transition metal layers. The strategy of Li-doping can improve the cycling stability and rate capability of P2-type layered oxides, which promotes the development of high-performance Na-ion batteries.