One-step electrochemical controllable preparation of nickel cobalt sulfide nanosheets and its application in supercapacitors

Abstract The bimetallic sulfides hold great promise for achieving high-performance supercapacitors. A facile unipolar pulse electrodeposition (UPED) method is developed to prepare nickel cobalt sulfides/polypyrrole (PPy) nanocomposites on carbon paper as electrode for supercapacitors, in which the crystalline structure, morphology and electrochemical performance of Co-Ni sulfides can be readily manipulated by simply changing the Co/Ni molar ratio in the electrodeposition electrolyte. It is demonstrated that the optimal CNS-3 electrode delivers the highest specific capacitance (2004 F g−1 at 1 A g−1), excellent rate capability and superior cycling stability. The outstanding electrochemical capacitive behavior can be ascribed to the synergistic effect of the Co-Ni sulfides, the 3D integrated porous structure of the electrode, as well as the conductivity and adhesion of PPy. Furthermore, an asymmetric supercapacitor (ASC) fabricated by the CNS-3 as positive electrode and activated carbon as negative electrode also displays remarkable electrochemical performance with ultralong cycle life and high energy density. These results manifest the great potential of CNS-3 in the development of high-performance supercapacitor electrode materials. Theoretically, the green and efficient UPED technology could also allow preparing other bimetallic or polymetallic sulfides with controllable composition, crystal structure and morphology.