Wood‐Derived High‐Mass‐Loading MnO2 Composite Carbon Electrode Enabling High Energy Density and High‐Rate Supercapacitor

Abstract The simple design of a high‐energy‐density device with high‐mass‐loading electrode has attracted much attention but is challenging. Manganese oxide (MnO 2 ) with its low cost and excellent electrochemical performance shows high potential for practical application in this regard. Hence, the high‐mass‐loading of the MnO 2 electrode with wood‐derived carbon (WC) as the current collector is reported through a convenient hydrothermal reaction for high‐energy‐density devices. Benefiting from the high‐mass‐loading of the MnO 2 electrode (WC@MnO 2 ‐20, ≈14.1 mg cm –2 ) and abundant active sites on the surface of the WC hierarchically porous structure, the WC@MnO 2 ‐20 electrode shows remarkable high‐rate performance of areal/specific capacitance ≈1.56 F cm –2 /45 F g –1 , compared to the WC electrode even at the high density of 20 mA cm –2 . Furthermore, the obtained symmetric supercapacitor exhibits high areal/specific capacitances of 3.62 F cm –2 and 87 F g –1 at 1.0 mA cm –2 and high energy densities of 0.502 mWh cm –2 /12.2 Wh kg –1 with capacitance retention of 75.2% after 10 000 long‐term cycles at 20 mA cm –2 . This result sheds light on a feasible design strategy for high‐energy‐density supercapacitors with the appropriate mass loading of active materials and low‐tortuosity structural design while also encouraging further investigation into electrochemical storage.