A high energy density asymmetric all-solid-state supercapacitor based on cobalt carbonate hydroxide nanowire covered N-doped graphene and porous graphene electrodes

Abstract

In order to achieve high energy densities, an asymmetric all-solid-state supercapacitor is developed by synthesizing a novel composite of cobalt carbonate hydroxide (CCH) nanowire covered N-doped graphene (NG) as positive and porous NG as negative electrodes. The CCH–NG composite is obtained from a one-step hydrothermal method, where optimization of the CCH content triples the specific capacitance of porous NG, reaching 1690 F g⁻¹ at 1.0 A g⁻¹. The optimal composite exhibits a remarkable cycling stability retaining 94.2% of the initial capacitance after 10 000 cycles, and good rate capability (still 1358 F g⁻¹ at 10 A g⁻¹). The assembled asymmetric supercapacitor based on the optimal composite has a high discharge areal capacitance of 153.5 mF cm⁻² (at 1.0 mA cm⁻²), can cycle reversibly in the high-voltage region of 0–1.9 V, and thus provide superior energy and power densities (0.77 W h m⁻² and 25.3 W m⁻²).