Reduced graphene oxide-nickel oxide composites with high electrochemical capacitive performance

► Different mass ratio of RGO-NiO composites were prepared by a solvothermal route. ► It was found that the mass ratio in composites is a key for morphology and specific capacitance. ► The composite with mass ratio 79:21 (NiO:RGO) exhibits the highest specific capacitance of 576 F g−1. ► The composite with mass ratio 79:21 exhibits good cycling stability with no decay over 1100 cycles.