Layered Structure Modification of Sodium Vanadate through Ca/F Co-Doping for Enhanced Energy Storage Performance

Vanadate 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. This research investigates the benefits of co-doping Ca and F into Na2V2O6 (NVO) cathode materials for improved sodium-ion battery performance. Density functional theory (DFT) calculations and experimental results show enhanced specific capacity, rate capability, and cycling stability. The co-doping reduces charge transfer and diffusion impedance, increases conductivity, and improves structural stability. This approach offers a promising strategy for developing high-performance sodium storage materials. image