High-Performance Aqueous Zinc–Manganese Battery with Reversible Mn(2+)/Mn(4+) Double Redox Achieved by Carbon Coated MnO(x) 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 Mn(2+)/Mn(4+) double redox. The active Mn(4+) is generated in situ from the Mn(2+)-containing MnO(x) nanoparticles and electrolyte. Benefitting from the low crystallinity of the birnessite-type MnO(2) as well as the electrolyte with Mn(2+) additive, the MnO(x) 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 Mn(2+)/Mn(4+) double redox (birnessite-type MnO(2 )↔ monoclinic MnOOH and spinel ZnMn(2)O(4) ↔ Mn(2+) ions). The reversible Mn(2+)/Mn(4+) double redox electrode reaction mechanism offers new opportunities for the design of low-cost, high-energy-density cathodes for advanced rechargeable aqueous batteries. [Image: see text] ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s40820-020-00445-x) contains supplementary material, which is available to authorized users.