In situ self-assembly of Ni 3 S 2 /MnS/CuS/reduced graphene composite on nickel foam for high power supercapacitors.
Wenbo LiWeiming SongHaihua WangYong-Mook KangPublished in: RSC advances (2019)
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.