Controlled WS2 crystallinity effectively dominating sodium storage performance

Abstract

WS2 exhibits tremendous potentials for Na-ions storage owing to high capacity (433 mAh g−1). Nevertheless, WS2 layered structure is often exfoliated with rapid capacity decay and sluggish reaction kinetics. In this work, WS2 nanosheets with different crystallinities are controlled by different synthesis methods. The high crystallinity WS2 exhibits high degree of interlayer order and strong interlayer force. It exhibits superior electrochemical properties, at the current density of 200 mA g−1 after 300 cycles with reversible capacity of 471 mAh g−1. Even at 5.0 A g−1, the capacities can still arrive at 240 mAh g−1 after 250 cycles, exhibiting stable cycling performance. Further electrochemical research finds that the high degree of interlayer order of layered WS2 structure can perform highly conducive Na+ insertion/extraction with greatly improved contribution of intercalation capacity. Moreover, the strong interlayer force can effectively restrain the exfoliating of the WS2 nanosheets, guaranteeing the stability of the structure. Combining the above result reveals that controlling the order and force of the interlayer is an effective way to enhance the electrochemical properties of WS2 as SIBs anode materials. This work can provide new insight for inhibiting the exfoliation of layered compounds to pursue excellent electrochemical performance in Na-ion storage systems.