MOF-derived Co/C nanocomposites encapsulated by Ni(OH)2 ultrathin nanosheets shell for high performance supercapacitors

It is a challenge to obtain high specific capacitance and high energy density for carbon materials applied in energy storage. In this work, a metal-organic framework (MOF) with high surface area (1149 m2 g−1) is used for the design of Co/C nanocomposites. Ni(OH)2@Co/C nanocomposites with core/shell structure are synthesized by carbonizing MOF nanoparticles to form the cores of Co/C and growing 2-dimensional Ni(OH)2 nanosheets on the surfaces, as the shells. The Ni(OH)2@Co/C nanocomposites exhibit excellent electrochemical properties, including high specific capacitance (952 F g−1, 0.5 A g−1), high-rate dischargeability (692 F g−1, 20 A g−1), and good cycle stability (84%, 10000th cycles), being ascribed to the combined effect of the components and the structure characteristics, i.e., Ni(OH)2 ultrathin nanosheets for high capacitance, Co nanoparticles for high rate dischargeability and nanoporous carbon for excellent cycle life. The asymmetric supercapacitor assembled with the Ni(OH)2@Co/C materials and active carbon presents a higher energy density of 33.6 Wh kg−1 at 516.3 W kg−1. The simple but powerful design routine will be beneficial to the application of MOF in such energy storage filed as battery and supercapacitor.