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

With the renaissance of oxygen vacancy strategy, MnO2 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 MnO2 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 MnO2 via the redox reaction between KMnO4 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 m2 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 MnO2 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 MnO2 in ACSs.