Enhanced cycling stability and rate capability of Na0.75Ni0.33Mn0.67O2 cathode material by Zn/F co-doping for sodium-ion batteries

P2-type layered transition metal oxides with high theoretical specific capacity and operating voltage are considered as one of the highly promising cathode materials for sodium-ion batteries, but the poor cycling stability attributed to the P2-O2 phase transition and Na + /vacancy ordering limits their practical applications. In this paper, a hydrothermal method is used to investigate the improvement of the electrochemical properties of Na 0.75 Ni 0.33 Mn 0.67 O 2 by Zn/F synergistic doping. The synergistic modification of Zn/F not only adjusts the valence distribution of Mn and improves the specific capacity, but also suppresses the phase transition under high voltage and the dissolution of transition metal ions. In particular, Na 0.75 Ni 0.23 Mn 0.67 Zn 0.1 O 1.95 F 0.05 (ZF-5) has excellent cycling performance (82.1% capacity retention after 100 cycles at 1C), compared to just 11.6% for the Na 0.75 Ni 0.33 Mn 0.67 O 2 (ZF-0). Above that, the rate performance is also significantly improved, with the specific capacity reaching 94.7 mAh g −1 even at a high current density of 5 C. Therefore, the Zn/F double doping modification strategy provides a simple and effective method for designing high-performance layered oxide cathode materials.