A NiCo2S4 nanoparticles composite, in-situ grown on rice husk hierarchical porous carbon, is synthesized through a facile one-step hydrothermal method for energy storage. The NiCo2S4 nanoparticles with a size of 20 +/- 10 nm are homogeneously distributed on the carbon matrix, leading to a high material utilization and high capacity, significantly outperformed the pure NiCo2S4. The chemical bonds of C-O-Co and C-O-Ni between the NiCo2S4 nanoparticles and the carbon matrix not only result in a superior power density, but also improve the cycling stability. An asymmetrical supercapacitor is assembled using the composite material and commercial YP-50 activated carbon and shows high energy density, high power density and excellent cycling stability. The hydrothermal method can be extended to synthesize other composite materials for energy storage devices.