Lithium substitution modulation of P2-type manganese-rich oxide toward high-stable and high-voltage cathode for sodium-ion batteries

P2-type manganese-rich layered oxide have attracted much attention as cathodes of sodium-ion batteries owing to the low cost, high capacity and fast sodium ion diffusion kinetics. However, the Jahn-Teller effect of Mn ³⁺, P2-O2 phase transition and anionic redox on charging to the high-voltage, resulted in a severe capacity delay. Herein, an effective Li substitution strategy is proposed to suppress the Jahn-Teller effect of Mn ³⁺, the harmful phase transition of P2-O2 and the anionic redox. As a result, the as-prepared sample Na _0.67(Ni _0.25Mn _0.75) _0.9Li _0.1O ₂ (67L10) displays a discharge specific capacity of 168.6 mA h g ⁻¹ at 0.1 C, enhanced average working voltage, and improved cycling stability at 1 C after 200 cycles within 1.5–4.5 V voltage window (capacity retention of 83.3 %, specific capacity of 106.8 mA h g ⁻¹) compared with that of pristine Na _0.67Ni _0.25Mn _0.75O ₂(capacity retention of 34.2 %, specific capacity of 51.3 mA h g ⁻¹). This work demonstrates the favorable effect of Li doping in P2-type layered materials to suppress the phase transition and inhibit the redox activity of Mn and O ions, and it provides an effective approach for the development of cathodes for sodium-ion batteries with high specific energy and long life.