Tuning the component ratio and corresponding sodium storage properties of layer-tunnel hybrid Na0.6Mn1-xNixO2 cathode by a simple cationic Ni2+ doping strategy

Manganese (Mn)-based cathodes with advantages of low-cost, environmental benign, high energy density are crucial for the commercial process of sodium ion batteries (SIBs). Layer-tunnel hybrid cathode, which aims to integrate high capacity of P2-type layered structure with excellent cycling stability, superior rate performance of tunnel structure, deserves great research efforts. To further enhance the respective performance, the ratio of layer-tunnel component in the hybrid Na0.6Mn1-xNixO2 was adjusted by a simple cationic Ni2+ doping route. The crystal structure and electrochemical behavior of Na0.6Mn1-xNixO2 were carefully detected, compared and analyzed. The comprehensive results evidenced that the layered component ratio would rapidly increase with Ni2+ doping. The structural parameters of pure phase would also be affected by varied Ni2+ content. And 5% Ni doping could be an optimized point in terms of reversible capacity, cycling stability, rate performance and reaction kinetics. This study would reveal the dual-function of cationic doping in both macro scale component ratio and atomic scale crystal lattice parameter, and grasp new insight into the design and optimization of high performance hybrid cathode for SIBs.