Large-scale synthesis of hybrid metal oxides through metal redox mechanism for high-performance pseudocapacitors

Electrochemical performance and production cost are the main concerns for the practical application of supercapacitors. Here we report a simple and universally applicable method to prepare hybrid metal oxides by metal redox reaction utilizing the inherent reducibility of metals and oxidbility of [Image: see text] for the first time. As an example, Ni(OH)(2)/MnO(2) hybrid nanosheets (NMNSs) are grown for supercapacitor application by self-reaction of Ni foam substrates in KMnO(4) solution at room temperature. The obtained hybrid nanosheets exhibit high specific capacitance (2,937 F g(−1)). The assembled solid-state asymmetric pseudocapacitors possess ultrahigh energy density of 91.13 Wh kg(−1) (at the power density of 750 W kg(−1)) and extraordinary cycling stability with 92.28% capacitance retention after 25,000 cycles. Co(OH)(2)/MnO(2) and Fe(2)O(3)/MnO(2) hybrid oxides are also synthesized through this metal redox mechanism. This green and low-cost method is capable of large-scale production and one-step preparation of the electrodes, holding promise for practical application of high-performance pseudocapacitors.