Constructing hierarchical CuS hollow spheres as efficient anode for aqueous zinc-ion batteries

In recent years, aqueous zinc-ion batteries (ZIBs) have emerged as a prominent research topic due to their inherent safety attributes, relatively low cost, and comparatively higher energy density. However, the challenges associated with the zinc metal anode in the form of dendrite formation, hydrogen evolution, and severe side reactions have proven to be particularly vexing. Thus, it is imperative to investigate novel intercalation-type anode materials for ZIBs that exhibit exceptional structural properties and appropriate redox potentials based on conversion mechanisms. In this work, through adding polyvinylpyrrolidone (PVP) surfactant to precursors and tailoring reaction time, hierarchical CuS hollow spheres are successfully constructed by a facile one-step hydrothermal process. When applied as an anode in ZIBs, the hollow hierarchical CuS with large surface area can effectively reduce the transport distance of electrons and Zn²⁺ and alleviate volume expansion during the insertion/extraction of Zn²⁺. The hierarchical CuS hollow spheres prepared over 8 h (CuS-8) exhibit a specific capacity of 126 mAh/g and long-term cycle life (1500 cycles) at a current density of 3 A/g. In addition, CuS-8//MnO₂@CNTs full-cell shows a capacity retention of 117 mAh/g after 300 cycles at 1 A/g current density, which proves the advantage of hierarchical CuS hollow spheres in serving as an efficient and durable anode material for ZIBs.