Modulating the Interlayer Spacing and Na+/Vacancy Disordering of P2-Na0.67MnO2 for Fast Diffusion and High-Rate Sodium Storage

Modulating the interlayer spacing and Na⁺/vacancy disordering can significantly affect the electrochemical behavior of P2-type cathode materials. In this work, we prepare a series of P2-Na_0.67MnO₂ cathodes (Na_0.67Ni_{0.2- x}Mn_0.8Mg _xO₂) with varying doping amounts of Mg and Ni to realize the maximization of the interlayer spacing within the experimental range and optimize the Na⁺/vacancy ordering. Consequently, the as-prepared Na_0.67Ni_0.1Mn_0.8Mg_0.1O₂ illustrates an excellent rate performance of 193 mA h g^-1 discharge capacity at 0.1 C (1 C = 180 mA g^-1), and even at a high rate of 8 C, the battery can deliver a capacity of 70 mA h g^-1. The kinetics analysis indicates the raising of Na⁺ mobility, which could due to the reduced Na⁺/vacancy ordering and the enhanced Na interlayer spacing. The codoping of Ni and Mg also enhances the stability of the layered structure, leading to improved cycling performance of 74.7% capacity retention after 100 cycles.