One-step synthesis of oxygen-deficient manganese dioxides sponge-like 3D architecture for high-performance supercapacitors

With the renaissance of oxygen vacancy strategy, MnO 2 has attracted renewed attention as one promising candidate of electrode materials for high energy density supercapacitors (SCs). However, the rational synthesis of such oxygen-deficient MnO 2 with controllable vacancy content and structure is the main challenge for high-performance SCs. Herein, we developed a one-step and template-free method to synthesize oxygen-deficient MnO 2 via the redox reaction between KMnO 4 and glucose. Glucose functions as both the reductant and the structure-directing agent. Synthetic temperature was manipulated to control the morphology and the oxygen vacancy content of the products. The sponge-like 3D architecture constructed by the interconnected tiny nanosheets can be realized at low temperature (<100 °C ), which can exhibit the large specific surface area up to 197.41 m 2  g −1 . The as-prepared active material at 60 °C exhibits high specific capacitance 358.8 F g −1 @ 2 A g −1 and high-rate capability 280.9 F g −1 @ 15 A g −1 . An asymmetric supercapacitor (ASC) is assembled by using our MnO 2 as the cathode and activated carbon (AC) as the anode. The obtained ASC can deliver the energy density up to 98.01 Wh kg −1 , the power density up to 59.43 kW kg −1 . After 15000 cycles, the capacitance retention rate still can keep 94.5%. This result indicates the promising prospective of oxygen-deficient MnO 2 in ACSs.