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.