Core-shell Ni1.5Sn@Ni(OH)2 nanoflowers as battery-type supercapacitor electrodes with high rate and capacitance.

Poor conductivity and aggregation of two-dimensional Ni(OH)2 nanosheets hinder their extensive applications in supercapacitors. In the current study, a core-shell nanoflower composite is successfully synthesized using a high conductivity Ni1.5Sn alloy and Ni(OH)2 nanosheets via a facile two-step hydrothermal reaction. The alloy material enhances the conductivity of the sample and promotes electron transport for Ni(OH)2. The as-prepared core-shell structure effectively restrains the clustering of nanosheets and improves the specific surface area of active materials. The optimized NS@NL-3 displays an outstanding specific capacitance (1002.2C g-1 at 1 A g-1) and satisfactory capacitance retention rate (80.63% at 20 A g-1) by adjusting the coating amount of Ni(OH)2 nanosheets, which is significantly higher compared with the performance of pure Ni(OH)2 (609.6C g-1 at 1 A g-1 and 55.64% at 20 A g-1). The all-solid-state hybrid supercapacitor (HSC) is fabricated with activated carbon (AC) as the negative electrode and NS@NL-3 as the positive electrode, which shows a high energy density of 57.4 Wh kg-1 at 803.6 W kg-1 as well as a superior cycling stability (88.45 % after 10,000 cycles). Experiment shows that 42 LEDs are effortlessly lit by two series-wound solid-state HSC devices, which indicates its high potential for practical applications.