The critical role of titanium cation for the enhanced Na-ion layer spacing of O3 layered oxide cathode materials

O3-NaNi 1/3 Fe 1/3 Mn 1/3 O 2 layered cathode material has been widely concerned by the industry for its advantages of simple preparation, low cost and high theoretical specific capacity. However, due to a series of surface side reactions, some transition metal ions are reduced, resulting in structural Jahn-Teller distortion, leading to poor structural stability . Herein, Ti element is introduced into O3-NaNi 1/3 Fe 1/3 Mn 1/3 O 2 cathode material, and the effect of Ti doping on the phase structure and electrochemical properties of the material is analyzed in detail. The results show that Ti doping can enlarge the Na layer spacing and decrease the transition metal layer spacing. Thus, the modified material has a smaller Na ion diffusion barrier and a more stable structure. These advantages give a sample with a doping rate of 2.5 wt% a rate capacity of 74.8 mAh g −1 at 10 C, a capacity retention rate of 86.2 % after 100 cycles at 1 C, and an energy density of 320.5 Wh kg −1 for a full cell structure using a hard carbon anode. This strategy provides a valuable reference for cationic doping to improve the properties of O3 layered transition metal oxides .