Bimetallic co-doping strategy for layered oxides in high-performance sodium-ion batteries

O3-type layered oxides have become a research hotspot in the development of sodium-ion batteries owing to their simple synthesis method and competitive theoretical capacity. However, their practical applications still face enormous challenges, especially concerning insufficient cyclic stability and poor kinetic performance. Herein, the Sb/Al co-doping NaNi 0.48 Mn 0.49 Sb 0.01 Al 0.02 O 2 (NMSA) material was produced via sol-gel process. Sodium-ion kinetics were investigated through Cyclic Voltammetry (CV) and Galvanostatic Intermittent Titration Technique (GITT), while the charge compensation mechanism was examined via ex-situ X-ray Photoelectron Spectroscopy (XPS). The successful doping of Al improves the stability of the transition metal oxide layer (TMO 2 ), thereby extending the cycle life of material. In-situ X-ray Diffraction (XRD) analysis reveals successful inhibition of the irreversible O3-P3 phase transition. In addition, Sb-doping increases the number of ions involved in charge compensation, thereby elevating the discharge specific capacity. Therefore, the NMSA material can provide a discharge specific capacity of 128.5 mAh g −1 at 0.1C and a capacity retention rate of 85 % after 100 cycles at 1C. Finally, the interface stability of the cycled material was studied to investigate the stability of the cathode/electrolytes interface (CEI) layer. This study provides new innovative views on proposing advanced cathode for high-energy sodium-ion batteries.