High‐Energy Aqueous Asymmetric Supercapacitors via Synergistic Design of Electrodes Derived from Hierarchical Vanadium Dioxide Nanocomposites

Abstract The energy density of aqueous asymmetric supercapacitors (ASCs) is confined by the narrow voltage and the mismatching between cathode and anode. Vanadium dioxide (VO 2 ) can contemporaneously operate in both negative and positive potential windows for efficient aqueous ASCs. Nonetheless, their intrinsically inferior cycling stability and capacity seriously restrain the overall capacitive properties. Herein, a novel manganese dioxide (MnO 2 ) coated VO 2 (VO 2 @MnO 2 ) with hierarchical structure is firstly fabricated as cathode with enlarged potential (0 to 1.2 V) and superb specific capacitance (608.9 F g −1 at 1.0 A g −1 ). Subsequently, VO 2 coated by a thin layer of carbon (VO 2 @C) owning high electric conductivity and superb structure stability is designed to match with VO 2 @MnO 2 cathode. Eventually, the VO 2 @C//VO 2 @MnO 2 aqueous ASCs exhibit stable voltage (2.2 V), maximal energy density (77.1 Wh kg −1 ) and favourable cycling stability. This research inspires the design and preparation of matchable electrode materials, providing a feasible method for the development of aqueous ASCs with broad voltage.