A nest-like Ni@Ni1.4Co1.6S2 electrode for flexible high-performance rolling supercapacitor device design

Abstract

Herein we fabricated a series of flexible electrode materials with nickel foam as a partly self-sacrificial template by an in situ growth solvent thermal method. We synthesized a nest-like Ni@Ni₃S₂ electrode material with building blocks of ∼80 nm diameter nanowires. The growth mechanism of nest-like Ni@Ni₃S₂ electrode materials was studied through time-dependent experiments, in which the control of material morphology was realized. Residual metal nickel in the framework bestows the as-obtained electrode materials with excellent flexibility. The nest-like Ni@Ni_1.4Co_1.6S₂ electrode material with a similar morphology and structure to Ni@Ni₃S₂ was fabricated using the Ni@Ni₃S₂ material as the template by a Co-exchange method. Continuous transition from Ni₃S₂ to Co₉S₈ was achieved depending on different replacement times. The synergistic and complementary advantageous effects of Co and Ni ions enhanced the specific capacitances from 89 F g⁻¹ (Ni@Ni₃S₂) to 122 F g⁻¹ (Ni@Ni_1.4Co_1.6S₂) at a current density of 1 A g⁻¹ at a high loading level of ∼20 mg cm⁻². Moreover, the cycle stability and coulombic efficiency of the Ni@Ni₃S₂ electrode material were also increased by the introduction of Co ions. All the as-assembled Ni@Ni₃S₂ and Ni@Ni_1.4Co_1.6S₂//activated carbon supercapacitor devices possessed high energy and power density, suggesting their potential application in high-performance flexible asymmetric rolling supercapacitor devices.