Layered Sodium-Rich Cathode Material NaNiMnO with a High Rate and a Long Cycle Life.

This study successfully designed and synthesized a sodium-rich layered material, P2-NaNiMnO (referred to as NNMO), via a straightforward sol-gel method. Analysis confirms that NNMO possesses a P2 phase (63/) layered structure, featuring a significantly enlarged interlayer spacing, which is conducive to the rapid diffusion of sodium ions. Further investigations revealed that the introduction of nickel (Ni) effectively reduced the manganese (Mn) content, thereby mitigating the Jahn-Teller effect and enhancing the material's electrochemical stability. Electrochemical performance tests demonstrated that the NNMO electrode exhibited superior performance within a 2-4.0 V voltage range. At a current density of 0.2 C, the initial cycle reversible capacity reached 127.4 mAh g, and after 100 cycles, the electrode maintained a high specific capacity of 114.9 mAh g, indicating a 90.2% capacity retention rate. Notably, after cycling at a high current density of 1 C for 500 cycles, the NNMO material still achieved a capacity retention rate of 90.0%, showcasing its exceptional cycle stability. These results suggest that the developed NNMO material, due to its excellent electrochemical performance and stability, holds great promise as a potent candidate for next-generation sodium-ion batteries.