Novel core–shell nanoclusters composed of multiple nickel–cobalt-oxyselenide nanowires wrapped with NiCo-LDH nanosheets for high energy density supercapacitors

Abstract

Transition metal selenides are widely used in supercapacitors because of their high theoretical capacity but their poor electron or ion accessibility in electrochemical tests leads to low conductivity and weak energy density. Herein, a novel nanocluster made up of a nickel–cobalt-oxyselenide (NiCoO₄Se₃, denoted as NCOSe) nanowire core and a Ni_xCo_y-LDH nanosheet shell on carbon fiber (CF@NCOSe/Ni_xCo_y-LDH) is synthesized for the first time. Nanosheets encapsulated with multiple active nanowires have a multitude of active sites and high electrical conductivity simultaneously. This core–shell structure can enhance material stability and also further stimulate the redox reaction activity of the internal core nanowires. Due to the synergistic effect of NCOSe and Ni₂Co₁-LDH, the nanocluster CF@NCOSe/Ni₂Co₁-LDH exhibits an outstanding capacity of 3270 F g⁻¹ (454.17 mA h g⁻¹) at 1 A g⁻¹. Significantly, the prepared hybrid supercapacitor (HSC) with CF@NCOSe/Ni₂Co₁-LDH//AC shows a particularly high energy density of 89.7 W h kg⁻¹ at a power density of 800 W kg⁻¹. In addition, the HSC exhibits an outstanding cycling performance of 95.6% capacitance retention after 10 000 charge/discharge cycles. Therefore, constructing core–shell nanoclusters with an effective electrolyte buffer space can obtain high capacitance electrode materials, which is an effective strategy to build high energy density HSCs.