Enhanced Sodium Storage Performance of Floral Spherical Vanadium Disulfide by Ether-Based Electrolyte and Copper...

Vanadium disulfide (VS₂) emerges as a great potential anode material for sodium-ion batteries (SIBs) owing to its large layer spacing and high specific capacity. However, the severe capacity decay and ambiguous sodium storage mechanism severely impair its merits. Herein, the nano-micro floral spherical VS₂ is designed and its performance enhancement mechanism in ether-based electrolyte is deciphered. The VS₂ anode in ether-based electrolyte undergoes multiple sodium storage mechanisms, involving a traditional reaction of VS₂↔NaVS₂↔Na₂S and a unique reaction of Na₂S↔Na₂S_x (2 < x <8) ↔S₈ facilitated by the Cu collector. Meanwhile, multiple reactions trigger decomposition-reassembly of the original structure to form the hierarchical porous framework that mitigates the stress generated by volume changes. Notably, molecular dynamics simulations and electrochemical measurements indicate that the ether-based electrolyte not only facilitates Na⁺ de-solvation and diffusion, but also endows the VS₂ electrode with speedy Na⁺ diffusion kinetics. Consequently, the VS₂ electrode in ether-based electrolyte demonstrates an outstanding reversible capacity of 655.8 mAh g^-1 after 900 cycles at ultra-high 20 A g^-1. In addition, the assembled Na₃V₂(PO₄)₃//VS₂ full battery achieves superior cycling stability with an average capacity decayed rate of only 0.069% per cycle. This work can provide precious insights into the development of advanced metal-sulfide anode materials.