Oriented design of three-dimensional flower-like spherical zinc oxide as negative material for dendrite-free and superior stable nickel-zinc secondary batteries

Nickel-zinc batteries are emerging as the potential alternative to lithium-ion and lead-acid batteries owing to the high open-circuit voltage, affordability, and eco-friendliness. Nevertheless, the problems of zinc dendrite growth, hydrogen evolution and dissolution passivation in the zinc electrode seriously hinder the commercial application of nickel-zinc batteries. To address these issues, three-dimensional flower-like spherical zinc oxide with exceptional electrochemical performance is successfully synthesized by using a facial solvothermal and calcination method. The three-dimensional flower-like structure provides more reactive sites for the negative active materials, reducing local current density and inhibiting zinc dendrite formation. As a result, three-dimensional flower-like spherical ZnO demonstrates superior electrochemical performance compared to pure ZnO and other spherical ZnO. Even after 1200 cycles, the discharge capacity still remains 500 mAh g^-1 at 12C, representing 87% of the initial capacity (570 mAh g^-1). Furthermore, the material maintains a relatively flat surface throughout the cycle, preventing the formation of dendrite.