Ni Foam-Ni3S2@Ni(OH)2-Graphene Sandwich Structure Electrode Materials: Facile Synthesis and High Supercapacitor Performance

A novel Ni foam-Ni3S2@Ni(OH)2-graphene sandwich-structured electrode (NF-NN-G) with high areal mass loading (8.33 mg cm−2) has been developed by sulfidation and hydrolysis reactions. The conductivity of Ni3S2 and Ni(OH)2 were both improved. The upper layer of Ni(OH)2, covered with a thin graphene film, is formed in situ from the surface of the lower layer of Ni3S2, whereas the Ni3S2 grown on Ni foam substrate mainly acts as a rough support bridging the Ni(OH)2 and Ni foam. The graphene stabilized the Ni(OH)2 and the electrochemical properties were effectively enhanced. The as-synthesized NF-NN-G-5mg electrode shows a high specific capacitance (2258 F g−1 at 1 A g−1 or 18.81 F cm−2 at 8.33 mA cm−2) and an outstanding rate property (1010 F g−1 at 20 Ag−1 or 8.413 F cm−2 at 166.6 mA cm−2). This result is around double the capacitance achieved in previous research on Ni3S2@Ni(OH)2/3DGN composites (3DGN=three-dimensional graphene network). In addition, the as-fabricated NF-NN-G-5mg composite electrode has an excellent cycle life with no capacitance loss after 3000 cycles, indicating a potential application as an efficient electrode.