γ-MnO2 nanorods/graphene composite as efficient cathode for advanced rechargeable aqueous zinc-ion battery

Aqueous Zn//MnO2 batteries are emerging as promising large-scale energy storage devices owing to their cost-effectiveness, high safety, high output voltage, and energy density. However, the MnO2 cathode suffers from intrinsically poor rate performance and rapid capacity deterioration. Here, we remove the roadblock by compositing MnO2 nanorods with highly conductive graphene, which remarkably enhances the electrochemical properties of the MnO2 cathode. Benefiting from the boosted electric conductivity and ion diffusion rate as well as the structural protection of graphene, the Zn//MnO2-graphene battery presents an admirable capacity of 301 mAh g−1 at 0.5 A g−1, corresponding to a high energy density of 411.6 Wh kg−1. Even at a high current density of 10 A g−1, a decent capacity of 95.8 mAh g−1 is still obtained, manifesting its excellent rate property. Furthermore, an impressive power density of 15 kW kg−1 is achieved by the Zn//MnO2-graphene battery.