| Summary: | Aqueous rechargeable zinc-manganese dioxide batteries have attracted extensive attention due to their high energy density, low cost, and environmental friendliness. However, the crystalline MnO2 polymorphs suffer from substantial phase changes upon cycling, leading to structural collapse and poor long-term cycling performance. Here, a highly reversible amorphous manganese dioxide with structural defects is reported as the cathode for aqueous rechargeable zinc-ion batteries (ARZIBs). Because of the existence of the abundant structural defects and intrinsic isotropic nature, the A-MnO2-δ exhibits significant pseudocapacitive contribution and facilitated reaction kinetics. As expected, the A-MnO2-δ delivers a high specific capacity of 301 mAh g−1 at 100 mA g−1 and long cycle-life with a capacity retention of 78% over 1000 cycles at 1 A g−1, which is better than its crystalline counterparts. In addition, a reversible H+ and Zn2+ two-step insertion storage mechanism of the A-MnO2-δ electrode is demonstrated. This study not only suggests that amorphous manganese dioxide can serve as a stable cathode for ARZIBs but also provides significant guidance to realize other high-capacity and long-lifespan aqueous batteries by using the amorphous materials.
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