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

Abstract 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 m 2  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%, 10000 th 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.