Construction of Low-Crystallinity Three-Dimensional Flower-like Cobalt-Doped Nickel Hydroxide for High-Performance Nickel–Zinc Batteries

The main limitations of aqueous nickel-zinc batteries are their relatively low energy density and short cycle life, which are inextricably linked to the limitations of nickel-based cathodes. In this study, a low-crystallinity flower-like cobalt-doped nickel hydroxide (α-Ni(OH)₂-0.2Co) is constructed by hydrothermal reaction and employed as high-energy-density cathode for aqueous rechargeable nickel-zinc batteries. Cobalt doping initiates the formation of a flower-like structure and lowers the material's crystallinity, conferring it with a larger specific surface area, more redox reaction sites, and shorter ion diffusion paths. The optimized α-Ni(OH)₂-0.2Co electrode manifests a considerable specific capacity of 772 C·g^-1 at 1 A·g^-1 and remarkable rate performance, with a capacity retention of 75% at 10 A·g^-1. The α-Ni(OH)₂-0.2Co//Zn battery constructed with α-Ni(OH)₂-0.2Co as the cathode exhibits a considerable specific capacity of 198 mAh·g^-1 at 1 A·g^-1 in an alkaline electrolyte. Additionally, the battery exhibits a substantial energy density of 326.7 Wh·kg^-1 and a power density of 16.5 kW·kg^-1, exceeding the performance metrics of most previously documented aqueous nickel-zinc batteries. This research presents a viable approach for developing advanced cathode materials for nickel-zinc batteries.