In this contribution, we report a facile preparation method of nickel cobalt oxide–reduced graphite oxide (NiCo₂O₄–rGO) composite material. A fast Faradic process has been realized by sodium dodecyl sulfate (SDS)-induced ultrasmall NiCo₂O₄ nanocrystals on rGO. As a result, this composite material gives a high specific capacitance of 1222 F g⁻¹ at 0.5 A g⁻¹ and 768 F g⁻¹ at 40 A g⁻¹, showing an outstanding rate capability. An asymmetric supercapacitor device with high energy and power densities has been successfully assembled based on NiCo₂O₄–rGO composite material and activated carbon. The optimized device shows a high energy density of 23.32 Wh kg⁻¹ at a power density of 324.9 W kg⁻¹. In addition, this asymmetric device shows good stability towards multistage current charge–discharge cycles.