Porous interconnected NiCo2O4 nanosheets and nitrogen- and sulfur-codoped reduced graphene oxides for high-performance hybrid supercapacitors

Abstract

We demonstrate a facile hydrothermal synthesis of the interconnected porous NiCo2O4 nanosheets for hybrid supercapacitor applications. The as-synthesized NiCo2O4 nanosheets show a high specific capacitance of 3137 F g−1 at a current density of 2 A g−1, which is much greater than 1916 and 1251 F g−1 of Co3O4 and NiO, respectively. Interestingly, the total specific capacitance of the NiCo2O4 is almost close to the sum of the specific capacitance of the NiO and Co3O4. Furthermore, a hybrid supercapacitor is configured with the NiCo2O4 nanosheets and the nitrogen- and sulfur-codoped reduced graphene oxide as the positive and negative electrodes, respectively. This hybrid supercapacitor delivers a maximum energy density of 33.64 W h kg−1 at a power density of 1196 W kg−1 and excellent long-term cyclic stability over 12,000 charge/discharge cycles at the enlarged voltage window of 1.5 V. The remarkable supercapacitive performances of the hybrid device are attributed to the interconnected porous structure of NiCo2O4 nanosheets and three-dimensional continuous macropores of codoped reduced graphene oxides.