A mechanically assisted solid-state reaction method is employed to prepare graphene/Ni(OH)(2) nanocomposites for supercapacitor electrode materials. Morphological analyses reveal that, at a loading 50 wt % Ni(OH)(2), nanoparticles with an average size of similar to 10 nm are formed and uniformly dispersed on the surface of reduced graphene oxide sheets functionalized with benzenesulfonate. Electrochemical measurements of the composite material show a high specific capacitance of 1568 F (based on nickel hydroxide) at a current density of 4 A g(-1), significantly higher than that of bare Ni(OH), nanoparticles prepared without the use of graphene. This much improved electrochemical performance is enabled by both the well-dispersed Ni(OH)(2) nanoparticles that offer large accessible surface area and the hydrophilic functional groups on graphene surface that facilitate electrolyte transport. The scalable solid-state synthesis developed in this work is promising for a green chemical approach to the preparation of supercapacitor electrode materials with high performance.