High-Performance Aqueous Zinc-Manganese Battery with Reversible Mn2+/Mn4+ Double Redox Achieved by Carbon Coated MnOx Nanoparticles

There is an urgent need for low-cost, high-energy-density, environmentally friendly energy storage devices to fulfill the rapidly increasing need for electrical energy storage. Multi-electron redox is considerably crucial for the development of high-energy-density cathodes. Here we present high-performance aqueous zinc-manganese batteries with reversible Mn2+/Mn4+ double redox. The active Mn4+ is generated in situ from the Mn2+-containing MnOx nanoparticles and electrolyte. Benefitting from the low crystallinity of the birnessite-type MnO2 as well as the electrolyte with Mn2+ additive, the MnOx cathode achieves an ultrahigh energy density with a peak of 845.1 Wh kg(-1) and an ultralong lifespan of 1500 cycles. The combination of electrochemical measurements and material characterization reveals the reversible Mn2+/Mn4+ double redox (birnessite-type MnO2 <-> monoclinic MnOOH and spinel ZnMn2O4 <-> Mn2+ ions). The reversible Mn2+/Mn4+ double redox electrode reaction mechanism offers new opportunities for the design of low-cost, high-energy-density cathodes for advanced rechargeable aqueous batteries.