Amorphous manganese dioxide with the enhanced pseudocapacitive performance for aqueous rechargeable zinc-ion battery

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-MnO_2-δ exhibits significant pseudocapacitive contribution and facilitated reaction kinetics. As expected, the A-MnO_2-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-MnO_2-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.