Research progress on transition metal sulfide-based materials as cathode materials for zinc-ion batteries

Zinc-ion batteries (ZIBs) have recently attracted great interest and have been deemed to a prospective energy storage technology considering their cost-effective, environmental friendliness, and superior safety. However, ZIBs development is challenged by the limited material options that can display acceptable Zn2+ storage. Transition metal sulfides (TMSs) are extensively used in the energy field due to their distinct physical and chemical characteristics. A wide interlayer spacing is attractive as a viable Zn2+ storage site for these TMSs. Despite the applicability of TMSs in ZIBs, they have not been extensively studied because of the limited reports in this field. In this review, we first briefly introduce the structural characteristics of TMSs, especially MoS2, and then the key challenges of their use as cathodes for ZIBs. Next, we provide a review of the strategies to improve the Zn storage capacity of TMSs-based (MoS2, VS2, VS4 and Ni3S2) cathodes by changing the interlayer spacing, doping, introducing defects, adjusting the crystal phase, and composition. Finally, we summarize and prospect the application of TMSs in ZIBs cathodes.