中国有色金属学报(英文版)
Transactions of Nonferrous Metals Society of China
| Vol. 35 No. 1 January 2025 |
（1. State Key Laboratory for Manufacturing System Engineering, Xi’an Jiaotong University, Xi’an 710049, China;
2. School of Mechanical Engineering, Xi’an Jiaotong University, Xi’an 710049, China;
3. Shaanxi Key Laboratory of Intelligent Robots, Xi’an Jiaotong University, Xi’an 710049, China;
4. School of Chemical Engineering and Technology, Xi’an Jiaotong University, Xi’an 710049, China）
Abstract:Ti at the oxidation states of Ti3+ and Ti4+, was used to enhance the performance of Na3V2(PO4)2F2O by partially substituting vanadium. After doping Ti, the crystallographic volume is decreased due to the less radii of Ti3+/4+, and the valence of Ti is demonstrated identical to V. During sodium insertion in Ti-doped Na3V2(PO4)2F2O, the two discharge plateaus split into three because of the rearrangement of local redox environment. Consequently, the optimized Na3V0.96Ti0.04(PO4)2F2O shows a specific capacity of 123 and 63 mA·h/g at 0.1C and 20C, respectively. After 350 cycles at 0.5C, the capacity is gradually reduced corresponding to a retention of 71.05%. The significantly improved performance is attributed to the rapid electrochemical kinetics, and showcases the strategy of replacing V3+/4+ with Ti3+/4+ for high-performance vanadium-based oxyfluorophosphates.
Key words: sodium vanadium oxyfluorophosphate; titanium doping; cathode; sodium battery; energy storage
