Improving energy density of supercapacitors using heteroatom-incorporated three-dimensional macro-porous graphene electrodes and organic electrolytes

Abstract

The synthesis of nitrogen- and sulfur-doped three-dimensional (3D) graphene architectures further treated by steam activation to increase surface area is reported in this study. Tetraethylammonium tetrafluoroborate (TEABF4) in propylene carbonate as an organic electrolyte is used to enlarge the voltage range of a supercapacitor (SC) for high energy density. The 3D nitrogen- and sulfur-doped, steam activated, reduced graphene oxides (N-SRGO and S-SRGO) contained 7.84% and 6.93% of N and S heteroatoms and feature 497 m2 g−1 and 525 m2 g−1 of surface area due to hieratical porosity of the substance. As shown in the galvanic charge/discharge curves, a range of 0–2.5 V in the 3D N-SRGO architectures showed the highest capacitance of 23.1 F g−1, delivering maximum energy and power densities of up to 20 W h kg−1 and 6190 W kg−1. The rate capability and cycle stability over 5000 cycles were evaluated to be 63% and 68%, respectively, for N-SRGO. This study provides a systematic way to improve energy density of SCs by combining heteroatom-doped 3D graphene architecture with an organic TEABF4/PC electrolyte.