3D meso/macroporous Ni3S2@Ni composite electrode for high-performance supercapacitor

Ni3S2@Ni composite electrode for supercapacitor is synthesized via a one-step solvothermal treatment of Ni foam at 120 degrees C, exhibiting a 3D meso/macroporous network structure. The structure contains Ni3S2 nanosheets with 15-20 nm in thickness and meso/macropores with an average pore size of 24.69 nm, and its formation is regulated through the slow release of S2- ions and the solid/liquid interfacial reactions in absolute ethanol. At a current density of 17.15 A g(-1), the composite electrode demonstrates a high specific capacitance of 945.71 F g(-1), and at various current densities below 17.15 A g(-1), it retains capacitance retention ratios above 100% after 2000 charge/discharge cycles. A two-step oxidation and three-step reverse reduction process occurs during the reversible Faradaic reaction of Ni3S2 in KOH aqueous solution, which is due to the valence transitions of Ni-0 in Ni3S2 between Ni-0 and Ni3+. The homogeneous cracking in Ni3S2 layer is a critical factor for achieving its long-term cycling stability, however, the cycling results in its amorphization. An asymmetric supercapacitor is assembled using Ni3S2@Ni composite electrode as the positive electrode and Ni foam as the negative electrode, which delivers an energy density of 55.79 Wh kg(-1) at the power density of 938.98 W kg(-1). (c) 2018 Elsevier Ltd. All rights reserved.