Controllable synthesis of NiCo-LDH/Co(OH)2@PPY composite via electrodeposition at high deposition voltages for high-performance supercapacitors

Global energy crisis require facile preparation of electronic devices with high energy and power densities. Eletrodeposition is a simple way to fabricate electrode materials. Applying a voltage beyond the water decomposition potential during electrodeposition in aqueous solutions is counterintuitive. Herein, we first applied −2.0 V during electrochemical deposition process to obtain a hierarchical electrode structure. Specifically, NiCo layered double hydroxide with Co(OH)2 (NiCo-LDH/Co(OH)2) and polypyrrole (PPY) composite (NiCo-LDH/Co(OH)2@PPY) were synthesized on Ni foam via electrodeposition at room temperature. By subtle control of deposition voltage and time, the as-prepared materials exhibit a cauliflower-like nanostructure, which is beneficial for electrolyte infiltration and charge transfer. PPY coating can also improve the electric conductivity of the electrode. As a result, the NiCo-LDH/Co(OH)2@PPY electrode shows an outstanding specific capacitance of 2132 F g−1 at a current density of 11 A g−1. Additionally, an asymmetric supercapacitor (ASC) with NiCo-LDH/Co(OH)2@PPY as cathode and active carbon as anode demonstrates high energy density and long cycling stability, implying great application potential of high-voltage electrodeposition.