Ultrathin CoFe-layered double hydroxide nanosheets embedded in high conductance Cu3N nanowire arrays with a 3D core–shell architecture for ultrahigh capacitance supercapacitors

Abstract

Ultrathin layered double hydroxide (LDH) nanosheets are a promising candidate as the electrode material for energy storage due to the ultrafast mass diffusion and greater specific surface area. As a kind of emerging electrode material, metal nitride plays a vital role in improving the poor conductivity of most supercapacitors. Herein, we design a novel three-dimensional (3D) embedded hierarchical core–shell nanostructure by combining ultrathin CoFe-LDH nanosheets (∼2.5 nm) with porous Cu₃N nanowire arrays (NWAs), in which the ultrathin CoFe-LDH nanosheets are grown from the interior of Cu₃N nanowire cores supported on Cu foam (denoted as Cu₃N@CoFe-LDH). The prepared Cu₃N@CoFe-LDH NWA electrode exhibits a high areal capacitance of 3078 mF cm⁻² at a current density of 1 mA cm⁻², excellent rate capacity (85.8% capacity retention at 20 mA cm⁻²) and superior cycling stability (93.9% retention after 10 000 cycles), making it significantly superior to the related CuO@CoFe-LDH NWA electrodes. Additionally, the constructed asymmetric supercapacitor (ASC) devices deliver an ultrahigh energy density of 2.474 mWh cm⁻³ and a robust cycling stability (92.6% retention after 10 000 cycles). The outstanding electrochemical performance can be credited to the significant enhancement of the specific surface area, charge transport, and mechanical stability by the ultrathin LDH shell, the highly conductive Cu₃N core, and the distinctive embedded core–shell nanostructure.