Suppressing the P2 - O2 phase transformation and Na/vacancy ordering of high-voltage manganese-based P2-type cathode by cationic codoping.

High-voltage and low-cost manganese-based P2-type oxides show real promise as promising cathode for sodium-ion batteries (SIBs). But the P2 - O2 phase transformation and Na/vacancy ordering results in the inferior structural stability and Na diffusion coefficient, which further leads to rapid decay of capacity and poor rate capability. Herein, in consideration of the synergetic effects of dual cationic doping, electrochemically inactive Li and active Co codoping are proposed to solve the above issues. The novel two-step doping strategy, Co doping during synthesis of precursors via coprecipitation reaction followed by Li doping during solid-state reaction, are rationally developed. As anticipated, the Li/Co codoped P2-type oxide exhibits the absence of P2 - O2 phase transformation and Na/vacancy disordering, which gives rise to an outstanding cycling stability (86.7% capacity retention within 100 cycles at 0.1C) and high-rate capability (reversible capacity of 109 mAh g even at 10C). In addition, the full-cells composed of the codoped P2-type positive and hard carbon negative show high energy-density, good lifespan and high-rate property. This proposed cationic codoping provides an effective and scalable tactics for modulating the structural properties of high-voltage P2-type cathodes for advanced SIBs.