Structural characteristics, electrochemical performance, and environmental stability of NaxNi0.33Fe0.33Mn0.33O2 cathodes with different sodium content for sodium ion batteries

Layered oxides have been regarded prospective cathodes for sodium ion batteries (SIBs) owing to their noteworthy capacity and low cost. Nevertheless, this material still faces many challenges in practical applications. Especially, the environmental adaptability of layered oxide cathodes is one of the most momentous considerations for the practical applications. Although many methods have been reported to improve the environmental stability, the effect of sodium content in the cathode material on its environmental stability has always been neglected. In this work, a series of Na x Ni 0.33 Fe 0.33 Mn 0.33 O 2 (NaxNFM, x=0.78, 0.89, 1) cathode materials are synthesized, and the effect of varying sodium contents on the structural characteristics, electrochemical performance, and environmental stability of oxide cathode materials is analyzed. The results explain that all three samples are O3 phase, but the electrochemical performance and environmental stability of cathode materials with different sodium contents have significant differences. Among them, Na0.89NFM cathode exhibits a high initial discharge capacity (134.2mAh g⁻ 1 at 0.1C), excellent cycling stability. Furthermore, after the polepiece exposure for 5 days in an environment of 40% RH and 30°C, Na0.89NFM is less affected and still exhibits excellent electrochemical performances. This work provid es an alternative for the preparation of excellent performance oxide cathode materials with environmental stability for SIBs.