Modulating the Interlayer Spacing and Na + /Vacancy Disordering of P2-Na 0.67 MnO 2 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 _0.67 MnO ₂ cathodes (Na _0.67 Ni _{0.2- x} Mn _0.8 Mg _x O ₂ ) 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 _0.67 Ni _0.1 Mn _0.8 Mg _0.1 O ₂ 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.