Investigation of zinc storage capacity of WS2 nanosheets for rechargeable aqueous Zn-ion batteries

Abstract

Rechargeable aqueous zinc ion batteries (ZIBs) are highly desired for future energy storage due to their low cost and high safety, yet the development of suitable cathode materials for ZIBs is still a main challenge. Herein, for the first time, we demonstrate 1T-WS2 nanosheets can be a promising cathode candidate for rechargeable ZIBs. Benefiting from the large inter-layer spacing and high conductivity of 1T phase, the as-synthesized WS-200 delivers reversible discharge capacities of 233.26, 206.25 and 179.99 mAh/g at the current densities of 50, 100 and 200 mA/g, respectively, while the discharge capacity of commercial WS2 is only ~ 22 mAh/g (current density: 200 mA/g). Even at a high current density of 1000 mA/g, WS2-200 still exhibits the initial discharge capacity of 85.11 mAh/g. Moreover, the zinc ion’s storage mechanism was analyzed by electrochemical impedance spectra (EIS) and cyclic voltammetry (CV) measurements. On the one hand, WS2-200 with 1T phase displays the improved ion diffusion. On the other hand, the small diameter of nanosheets and expanded inter-layer spacing increases the capacitive capacity of WS2. This work lays the foundation for the research of WS2, which is expected to become one of the competitive cathode materials for zinc-ion batteries.