Facile synthesis of CoNi2S4/graphene nanocomposites as a high-performance electrode for supercapacitors

CoNi2S4/graphene nanocomposites were synthesized by a simple solvothermal method and used as supercapacitor electrodes. CoNi2S4 nanoparticles were doped in graphene layers, which is favorable for improving electrochemical performances of the as-prepared materials. The resulting electrochemical performance of CoNi2S4/graphene nanocomposite electrodes possessed pseudocapacitive behavior with high specific capacitance (1621 F g−1 at 0.5 A g–1), good rate capability (76.7% capacitance retention when reaching 10 A g–1) and outstanding cycling stability (no capacitance loss after 2500 charge–discharge cycles at 5 A g–1). In addition, as the positive electrode of an asymmetric supercapacitor, the material also shows a high specific capacitance of 126.6 F g–1 at 0.5 A g–1, good cycle stability with capacitance retention of 87.4% after 5000 cycles and the highest energy density of 39.56 W h kg–1 at the power density of 374.8 W kg–1.