Defect engineering in Co-doped Ni3S2 nanosheets as cathode for high-performance aqueous zinc ion battery

With the merits of low cost, environmental benignity, and high safety, aqueous zinc ion batteries (AZIBs) have great potential in the field of energy storage. In this paper, we craft a Co-doped Ni3S2 with abundant sulfur vacancies as effective cathode materials (Co-Ni3S2–x) for AZIBs by hydrothermal and chemical reduction method. Notably, cobalt doping and abundant sulfur vacancies can effectively increase the conductivity and the number of active sites for electrochemical reactions, which gives the Co-Ni3S2–x electrode the outstanding capability to energy storage. By coupling Co-Ni3S2–x cathode with Zn anodes to assemble alkaline AZIBs, the Co-Ni3S2–x//Zn full battery exhibits excellent specific capacity (183.9 mAh g–1 at 1 A g–1, based on cathode mass) and extraordinary cycling durability (72.9% capacity retention after 6000 cycles). First-principles calculations based on density functional theory (DFT) confirm that the Co-Ni3S2–x electrode has strong energy storage capacity and electrochemical stability. The results provide an extremely significant reference in designs of self-supported bimetallic sulfide nanosheets, which have promising applications in high-performance energy storage devices.