Controllable crystal growth of a NiCo-LDH nanostructure anchored onto KCu7S4 nanowires via a facile solvothermal method for supercapacitor application

Abstract

The application of NiCo-LDHs as electrode materials for supercapacitors has attracted widespread attention. However, pristine NiCo-LDHs always suffer from low conductivity and instability that limit their electrochemical performance in supercapacitors. Herein, we rationally engineered a novel KCu₇S₄@NiCo-LDH core–shell structure with good capacitive performance using a simple one-step solvothermal method and applied this structure as an electrode material for supercapacitors. KCu₇S₄ nanowires act as a dependable “skeleton” for supporting the NiCo-LDH nanosheets, thus preventing the aggregation of NiCo-LDHs and improving their conductivity. By controlling the reaction time and the ratio of Ni/Co in the precursor solution, according to the results of electrochemical testing, an optimal composite was obtained with Ni/Co = 2/1 and the reaction time of 8 h; the final KCu₇S₄@Ni₂Co₁-LDH composite possessed the high specific capacitance of 1104.5 F g⁻¹ (122.7 mA h g⁻¹) at 2 A g⁻¹, good rate capability of 65.9% when the current density reached up to 10 A g⁻¹, and a long-term stability (an 83.5% capacitance retention after 1000 cycles).