Flower-like Ni3Sn2@Ni3S2 with core–shell nanostructure as electrode material for supercapacitors with high rate and capacitance

To enhance the specific capacitance as well as maintain satisfactory rate performance of nickel hydroxide and nickel sulfide, in this work, the ultra-fine nickel-tin nanoparticles with high conductivity are selected to synthesize Ni3Sn2@Ni(OH)2 and Ni3Sn2@Ni3S2 nanoflowers. Alloy as the core material improves the electrical conductivity of the composite, and the nanosheets prepared by electrochemical corrosion effectively avoid aggregation as well as increase the active sites of the electrode material. By adjusting the corrosion time, the Ni3Sn2@Ni(OH)2 with better morphology displays a high specific capacitance (1277.37C g-1 at 1 A g-1) and good rate performance (1028C g-1 at 20 A g-1). After sulfurization, the optimal Ni3Sn2@Ni3S2 perfectly retains the morphological characterizations of the precursor and exhibits ultra-high specific capacitance (1619.02C g-1 at 1 A g-1) as well as outstanding rate performance (1312C g-1 at 20 A g-1). The samples before and after vulcanization both have the excellent electrochemical properties, which is attributed to the rational design and construction of the alloy-based core-shell nanostructures. Besides, the all-solid-state hybrid supercapacitor (HSC) is assembled by Ni3Sn2@Ni3S2 as the positive electrode and activated carbon as the negative electrode, displaying outstanding energy density of 70.54 Wh kg-1 at 808.67 W kg-1 and excellent cycling stability (93.21 % after 10,000 cycles). This work provides a novel ingenuity for synthesizing high-performance supercapacitor electrodes.