Nitrogen and oxygen co‐doped carbon microspheres with partially graphitic structures: Integrated high volumetric capacitance, mass loadings and rate capability for supercapacitors

Abstract

AbstractSynthesis of porous carbon electrodes with high volumetric capacitance and excellent rate capability, especially for a higher mass loading of 10 mg cm–2, remains a challenge and is important for wide applications of the new generation supercapacitors. We report unprecedented volumetric capacitance of 942.9 F cm–3 in 2 M H2SO4 for partially graphitized carbon microspheres co‐doped with N and O prepared by simple hydrothermal route followed by direct cobalt catalytic pyrolysis, which is comparable to the expensive metal oxide and MnO2‐based pseudo‐capacitors. The resulted carbon also shows excellent rate capability (65.4% and 52.2% capacitance retention as the current density increases from 1 to 20 A g–1 in 2 M H2SO4 and 6 M KOH, respectively) and cyclic stability with a higher mass loading of 9.84 mg cm–2 in acidic/basic electrolytes. More importantly, the high volumetric energy density (22.39 Wh L–1) of the assembled symmetrical supercapacitors in 6 M KOH makes it possible to compete with even some Ni metal hydride batteries. This work offers a way to develop advanced porous carbon materials with ultrahigh volumetric capacitance/mass loadings and fast charge rates for supercapacitors.