Enhanced cycling stability and storage performance of Na0.67Ni0.33Mn0.67-xTixO1.9F0.1 cathode materials by Mn-rich shells and Ti doping

We propose a synergistic strategy of titanium doping and surface coating with a Mn-rich shell to modify the Na-rich manganese-oxide-based cathode material Na(0.67)Ni(0.33)Mn(0.67-x)TixO(1.9)F(0.1) in sodium-ion batter-ies and elucidate the underlying mechanism for enhanced material performance. First, it is found that the electrochemical performance of the proposed cathode material can be effectively improved when the Ti doping amount is x = 0.3. In addition to doping, the cathode material coated with a manganese-rich shell was prepared by a liquid coating method. The as-prepared Mn@Ti-doped-Na(0.67)Ni(0.33)Mn(0.67-x)TixO(1.9)F(0.1) exhibited excellent electrochemical performance, delivering 169 mAh/g discharge capacity. The charge-discharge cycle test was carried out at a current density of 2C, and the sample not only provides a rever-sible capacity of 119 mAh/g but also has a capacity retention rate of 71 % after 500 charge discharge cycles. The Ti doping and surface coating with a Mn-rich shell are shown to improve the specific discharge capacity, cycling stability and rate capability of the cathode material and mitigate voltage decay. These results validate our design principle and provide a novel approach to enhance the performance of cathode materials in sodium-ion batteries.

Automated summary

We propose a synergistic strategy of titanium doping and surface coating with a Mn-rich shell to improve the performance of the Na-rich manganese-oxide-based cathode material in sodium-ion batteries. The Ti-doped and Mn-coated cathode material exhibited excellent electrochemical performance, delivering a discharge capacity of 169 mAh/g and a capacity retention rate of 71% after 500 charge discharge cycles. These results validate our design principle and provide a novel approach to enhance the performance of cathode materials in sodium-ion batteries.