The synergy of dis-/ordering ensures the superior comprehensive performance of P2-type Na-based layered oxide cathodes

Abstract

Two kinds of crystal orderings in layered oxides typically exhibit opposite influences on performances: Na⁺/vacancy ordering in alkali metal layers with an unfavorable effect on electrochemical performance and the cation ordering in transition metal layers with a positive effect on air stability. However, because the two kinds of orderings are associated with each other and often occur at the same time, it is difficult to achieve an excellent comprehensive performance. Herein, we propose a strategy of introducing a new cation ordering to construct the coexistence of Na⁺ disordering and transition metal ordering. An absolute solid-solution reaction mechanism is realized in the Na⁺ disordered system, resulting in a superior cycling stability of 90.4% retention after 150 cycles and a rate performance of 82.7 mAh g⁻¹ capacity at 10C, much higher than the original 81.3% and 66.4 mAh g⁻¹. Simultaneously, the cation ordering strengthens the interlayer interaction and inhibits the insertion of water molecules from the air, ensuring stable lattice stability and thermostability after air exposure. The synergy of dis-/ordering configuration provides new insights to design high-performance layered oxide cathode materials for secondary-ion batteries.