In situ self-assembly of Ni(3)S(2)/MnS/CuS/reduced graphene composite on nickel foam for high power supercapacitors

Transition metal sulfides (TMS), as promising electroactive materials for asymmetric supercapacitors, have been limited due to their relatively poor conductivity and cycle stability. Here ternary Ni(3)S(2)/MnS/CuS composites were assembled in situ on nickel foam (NF) using a hydrothermal method via electrostatic adsorption of Ni(+), Mn(2+) and Cu(2+) ions on a reduced graphene (rGO) nanosheet template. The chemical structure was characterized by various analytic methods. Ni(3)S(2)/MnS/CuS has spherical morphology assembled from closely packed nanosheets, while Ni(3)S(2)/MnS/CuS@rGO has a three-dimensional porous spherical structure with much lower diameter because rGO nanosheets can play the role of a template to induce the growth of Ni(3)S(2)/MnS/CuS. At a current density of 1 A g(−1), the specific capacitance was obtained to be 1028 F g(−1) for Ni(3)S(2)/MnS/CuS, 628.6 F g(−1) for Ni(3)S(2)/MnS@rGO, and 2042 F g(−1) for Ni(3)S(2)/MnS/CuS@rGO, respectively. Charge transfer resistance (R(ct)) of Ni(3)S(2)/MnS/CuS@rGO (0.001 Ω) was much lower than that of Ni(3)S(2)/MnS@rGO by 0.02 Ω, and lower than that of Ni(3)S(2)/MnS/CuS by 0.017 Ω. After 5000 cycles, the Ni(3)S(2)–MnS–CuS@RGO electrode maintains 78.3% of the initial capacity at 20 A g(−1). An asymmetric supercapacitor was subsequently assembled using Ni(3)S(2)/MnS/CuS@rGO as the positive electrode and rGO as the negative electrode. The specific capacitance of asymmetric batteries was maintained at 90.8% of the initial state after 5000 GCD.