In-situ regulated competitive proton intercalation and deposition/dissolution reaction of MnO2 for high-performance flexible zinc-manganese batteries

Abstract

Due to the limitation of energy density caused by the one-electron reaction and capacity loss caused by the Mn(Ⅲ) disproportionation reaction, it is difficult to realize the synchronous improvement of energy density and cycle performance of Zn//MnO2 secondary batteries. Here, a competition mechanism is designed for the zinc-manganese battery to achieve both improved energy density and cycling stability by coupling a high crosslinking density hydrogel electrolyte (HCH) with MnO2 deposition and dissolution reaction. Compared to conventional aqueous electrolytes (2 M ZnSO4, 0.2 M MnSO4), the ultrathin HCH (101 μm) widens the battery's voltage window to 2.4 V without significantly increasing the weight of the electrolyte. HCH not only broadens the voltage window but also effectively delays the proton shuttle from cathode to anode, providing a favorable environment for MnO2/Mn2+ reversible cyclic reaction. The Zn//MnO2 battery achieved an energy density of 858 Wh/kgα-MnO2 and a stable cycle of 7000 cycles due to the limitation of disproportionated reactants by the in situ deposition and dissolution of MnO2 at the cathode.