Iron-doped nanoflakes of layered double hydroxide of nickel for high-performance hybrid zinc batteries

Hybrid Zn–air and Zn–M (M represents transition metal oxide/hydroxide) batteries combined at the cell level take the advantages of Zn–air high-capacity and Zn–M high cell voltage. However, the performance of a Zn–air/M battery relies on finding a dual-functional cathode material, which can effectively serve both battery's chemistries. Here, we demonstrate the superior performance of a hybrid battery cathode based on Fe-doped Ni double hydroxide nanoflakes and activated carbon material. Fe doping transforms the disordered crystal structure of Ni hydroxide to a stable hydrotalcite-type structure with significantly enhanced redox conversion capacity, improved electric conductivity, and superior oxygen evolution reaction activity. Therefore, the hybrid battery exhibits a high total energy density, unprecedented energy conversion efficiency (87% at 4 mA/cm ²), and superior power density (100 mW/cm ² at 60 mA/cm ²) that outperform reported hybrid batteries of other cathode materials. Moreover, the hybrid Zn–air/Ni _1−xFe _x–layered double hydroxide battery is featured with the capability of high-rate charging owing to the rapid kinetics of the redox reactions and the excellent catalytic activity of the cathode materials.