Formation of multi-shelled nickel-based sulfide hollow spheres for rechargeable alkaline batteries

Metal sulfides with multi-shelled hollow structures are promising electrode materials for rechargeable alkaline batteries due to their abundant redox centers and electrochemically active sites. We designed and synthesized a high-performance electrode material of sulfide-rich metal sulfides with nanostructured multi-shelled hollow spheres. Using multi-shelled NiO hollow spheres as precursors, three types of nickel sulfide (Ni₃S₂, NiS, NiS₂) with controlled valence were obtained by controlling the sulfurization conditions. When applied as electrode materials for rechargeable alkaline batteries, multi-shelled nickel sulfide hollow spheres exhibit excellent electrochemical performance. Interestingly, the hollow spheres with more shells deliver better performance than those hollow spheres with fewer shells, owing to their greater number of faradaic active sites, shorter diffusion path and better electrochemical stability. The quadruple-shelled NiS₂ hollow spheres show a high specific capacity (216 mA h g⁻¹ at 5 A g⁻¹) and outstanding cycling performance (89.96% retention after 5000 cycles).