Mesoporous nickel hydroxides Ni(OH)(2)/graphene nanohybrids were fabricated via heteroassembly of oppositely charged exfoliated Ni(OH)(2) and graphite oxide (GO) nanosheets in formamide. The resulting hybrids exhibited a hierarchically porous networks composed of Ni(OH)(2) and reduced graphite oxide (rGO) nanosheets. When the atomic ratio of Ni to C in hybrids was optimized to be 0.63, the resulting hybrids exhibited a specific capacitance of 1488 F/g at a scan rate of 1 mV/s with an excellent cycling stability. Originating from their heterogeneous compositions and hierarchically porous structures, almost all of their Faradic capacitance and non-Faradic capacitance could be employed. The rationally designed Ni(OH)(2)/rGO nanohybrids with completely engineered interface were used as cathode for asymmetric supercapacitors (ASCs). Optimized Ni(OH)(2)/rGOI/AC ASC exhibited a high capacitance of 102.3 Fig. Therefore, a high energy density of 36.7 Wh/Kg and power density of 7.98 KW/Kg have been realized. Hence the present Ni(OH)(2)/rGO hybrids should be promising candidates as high-performance supercapacitors for energy storage and conversion. (C) 2017 Elsevier B.V. All rights reserved.