Plasma-induced ε-MnO2 based aqueous zinc-ion batteries and their dissolution-deposition mechanism

MnO2 has attracted great interest in working as the cathode of zinc ion batteries. However, the development of high-capacity, high-energy-density, and durable manganese-based cathodes with an easy synthesis strategy and proper energy storage mechanism remains an ongoing challenge. Herein, a facile plasma-induced strategy was demonstrated to introduce oxygen vacancies into the ε-MnO2, and the obtained oxygen vacancies-rich ε-MnO2 nanosheets (ε-MnO2–x) show satisfactory electrochemical performances. Furthermore, an appropriate energy storage mechanism for dissolution/deposition was proposed. Thanks to a synergistic effect of the oxygen vacancies in ε-MnO2 nanosheets and the exposed free-standing collector for Mn2+ dissolution/deposition, the ε-MnO2–x nanosheets electrode delivers a remarkable capacity (337 mAh g–1 at 0.1 A g–1) and exhibits an ultrahigh energy density of 462 Wh kg–1 (based on the weights of the cathode active material). Furthermore, impressive durability with 85.9% capacity retention after 1000 cycles was obtained. The superior electrochemical performance makes the plasma-induced strategy promising for designing advanced metal oxide electrode materials for high-performance aqueous zinc ion batteries.