A high-performance asymmetric supercapacitor achieved by surface-regulated MnO2 and organic-framework–derived N-doped carbon cloth

Abstract

It is possible to achieve high energy density and power density simultaneously for asymmetric supercapacitors by using pseudocapacitive materials with abundant ion intercalation/de-intercalation sites on the surface. Herein, a positive electrode based on feather-like MnO2 anchored on the activated carbon cloth is prepared, in which oxygen-enriched MnO2 nanorods with a radial sheet-like structure (OMO@AC) further form via electrochemical oxidation. Because of the large contact area with electrolyte and abundant oxidation functional groups on its surface, the OMO@AC displays excellent capacitance of 3,160 mF/cm2 at 1 mA/cm2. For the nitrogen-doped active carbon negative electrode, the capacitance is up to 1,875 mF/cm2 at 4 mA/cm2 due to the increase in disorder and defect on the carbon surface by N-doping. Furthermore, we verify the good electrochemical activity on the OMO@AC electrode surface by first-principles calculations and confirm the good matching degree between the positive and negative electrodes by CV testes. The aqueous oxygen-enriched MnO2// nitrogen-doped active carbon asymmetric supercapacitor exhibits an ultrahigh energy density of 8.723 mWh/cm3 at a power density of 14.248 mW/cm3 and display excellent cycle stability maintaining 95.5% after 10,000 cycles. The facile synthesis method and excellent performance provide a feasible way for the preparation of high-performance electrode materials for energy storage devices.