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-Na0.67MnO2 cathodes (Na0.67Ni0.2- xMn0.8Mg 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 Na0.67Ni0.1Mn0.8Mg0.1O2 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.