Affiliation:
1. Fujian Key Laboratory of Surface and Interface Engineering for High Performance Materials Xiamen University Xiamen 361005 P. R. China
2. Xiamen Key Laboratory of High Performance Metals and Materials Xiamen University Xiamen 361005 P. R. China
3. State Key Laboratory of Advanced Welding and Joining Harbin Institute of Technology Harbin 150001 P. R. China
4. Institute of Materials Genome and Big Data Harbin Institute of Technology Shenzhen 518055 P. R. China
Abstract
AbstractVanadate materials are promising for sodium‐ion batteries (SIBs) due to their low cost, high capacity, and high power characteristics enabled by vanadium's multiple oxidation states. However, their development is hindered by poor conductivity, suboptimal high‐rate performance, and limited cycle life. In this work, a layered structure modification strategy involving Ca/F co‐doping in sodium vanadate Na2CaV2O6F (CVF) is proposed to address these issues. Through a combination of experiments and density functional theory calculations, it is demonstrated that Ca/F synergies enhance the Na layer spacing in CVF, resulting in reduced crystal water content and volume shrinkage compared to Na2V2O6 (NVO). Additionally, Ca/F incorporation significantly mitigates the diffusion potential of Na+ within the material framework. The unmodified CVF sample exhibits a high reversible capacity of 220 mAh g−1 at 10 mA g−1 and an excellent rate capacity of 65.78 mAh g−1 at 400 mA g−1. Furthermore, the cathode material maintains a capacity of up to 138 mAh g−1 at 200 mA g−1 and retains 104.88 mAh g−1 after 100 cycles within the voltage range of 1.5−4.0 V. These findings enhance the understanding of the crystal structure of NVO cathode materials and pave the way for the rational design of high‐quality vanadate cathodes for SIBs.
Funder
National Natural Science Foundation of China
Fundamental Research Funds for the Central Universities