Self-Supported Sisal-like CuCo₂O₄@Ni(OH)₂ Core–Shell Composites Grown on Ni Foam\nfor High-Performance All-Solid State Supercapacitors

Abstract

Construction of reasonable nanostructures\nfor electrode materials\nis regarded as one critical strategy for improving capacitance and\ncycle life of supercapacitors (SCs). Here, self-supported, sisal-like\nCuCo₂O₄@Ni­(OH)₂ composites were successfully\nsynthesized on Ni foam using a hydrothermal treatment followed by\nthe electrochemical deposition reaction. Scanning electron microscopy\ncharacterization of the composites verified that the sisal-like CuCo₂O₄@Ni­(OH)₂ core–shell nanostructure\ncomprising coating CuCo₂O₄ nanoneedles with\nNi­(OH)₂ nanoflakes. This novel structure afforded the CuCo₂O₄@Ni­(OH)₂ composites a markedly enhanced\nspecific capacitance of 1902 F g^–1 at 2 A g^–1 and an ultralong cycle life with a captaincy retention\nof 87.6% after 50 000 cycles at 10 A g^–1.\nFurthermore, an asymmetric solid-state supercapacitor comprising CuCo₂O₄@Ni­(OH)₂//activated carbon was assembled\nand it exhibited a high energy density of 38.6 W h kg^–1 at 800 W kg^–1. These performances strongly suggest\nthat the self-supported sisal-like CuCo₂O₄@Ni­(OH)₂ electrode is a very promising positive material for use in\nSCs.