Boosted Electrochemical Performance of Honeycomb-Like\nNiCu–LDH Nanosheets Anchoring on NiCo₂S₄ Nanotube Arrays for Flexible Solid-State Hybrid Supercapacitors

Abstract

Nickel-based layered\nhydroxides (LDHs) have aroused much interest\nas promising battery-type electrodes for hybrid supercapacitors (HSCs)\nbecause of their high theoretical capacity, good safety, and abundant\nnatural resources; however, the electrochemical performances are still\nnotoriously limited owing to their intrinsically poor electrical conductivity\nand severe agglomeration features. Herein, an elaborate hierarchical\nNiCo₂S₄@NiCu–LDH nanotube/nanosheet hybrid\nelectrode is designed and fabricated directly on carbon cloth by a\nfacile multistep solution-based strategy. Through the rational engineering\nof nanostructures and atomic substitution of nickel by copper, the\noptimized NiCo₂S₄@NiCu–LDH hybrid electrode\ncan yield a high areal capacity of 632.0 μAh/cm² at\na current density of 2 mA/cm² and a good rate capability.\nFurthermore, the assembled flexible solid-state HSC device employing\nthe NiCo₂S₄@NiCu–LDH exhibits a maximum\nvolumetric energy density of 2.7 mWh/cm³ at a power density\nof 21.3 mW/cm³ with a robust long-term cycling stability\nover 2000 cycles and outstanding flexibility under repeated bending\ntests. Our work demonstrates the possibility of designing and fabricating\nnickel-based LDHs as superior battery-type electrodes towards highly\ndurable and efficient flexible energy storage devices.