Shape-controlled growth of three-dimensional flower-like ZnO@Ag composite and its outstanding electrochemical performance for Ni-Zn secondary batteries.

A novel three-dimensional (3D) flower-like ZnO@Ag composite is successfully synthesized through a simple and facile process, which is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).When evaluated as an anodic material for nickel-zinc alkaline secondary batteries, the 3D flower-like ZnO@Ag composite exhibits the high discharge capacity (627 mAh g-1) and long cycle life (830 cycles). The outstanding electrochemical performance is ascribed to the Ag nanoparticles enhancing electron conductivity and the uniform flower-like structure providing enough electrochemical reaction sites, so as to reduce electrode polarization and improve cell efficiency. Furthermore, the possible growth mechanism of 3D flower-like ZnO@Ag composite has been proposed. The effect of silver content on formation of ZnO@Ag composites was also investigated in detail, indicating the appropriate silver content plays a key role in forming a defined 3 D flower-like structure for the ZnO@Ag composite.