Synthesis and Sodium Storage Performance of Highly Stable Vanadium Sulfide Microsphere Anodes

VS₄ has an one-dimensional chain structure with the chain spacing of 0.583 nm, which is greater than Na⁺ ion radius of 0.102 nm. Moreover, its theoretical sodium storage capacity is 1196 mA·h/g, making it one of the most promising anode materials for sodium storage. However, the volume of the electrode material expands and contracts dramatically during repeated cycling, resulting in collapse of the structure, poor cycling stability and capacity decay, and severely affecting the practical application of VS₄. In this paper, VS₄ microspheres (approximately 1 μm in diameter) with a high stability were constructed for the unique three-dimensional microsphere structure to alleviate the volume expansion, improve the cycling stability and the electrochemical reaction kinetics. This microsphere structured material as an anode material for sodium ion batteries exhibits a superior rate performance (i.e., 372 mA·h/g@2.0 A/g and 297 mA·h/g@5.0 A/g) and a long-cycle life (i.e., stable cycling for 100 times at 5.0 A/g).