Hierarchical nanosheet-nanowire heterostructures of NiCo-LDH@NiCo₂S₄ for high-performance asymmetric supercapacitors

Developing electrode materials with enhanced specific capacitance and exploring their structural-property relationships are essential for optimizing the overall performance of supercapacitors. In this study, a novel binder-free electrode material comprised of NiCo-LDH and NiCo₂S₄ was successfully synthesized on a nickel foam substrate through a hydrothermal method combined with a high-temperature gas-phase sulfidation process. After partial sulfidation treatment, NiCo-LDH@NiCo₂S₄ composite presents a special structure composed of the nanosheet-like NiCo-LDH and the nanowire-like NiCo₂S₄ assemblies. It has a significant specific capacitance of 3400 F g−1 at 1 A g−1, the specific capacitance retention remained at 44.7% even at a high current density of 10 A g−1. Additionally, a NiCo-LDH@NiCo₂S₄//AC asymmetric supercapacitor (ASC) device was constructed using the NiCo-LDH@NiCo₂S₄ as the positive electrode, activated carbon (AC) as the negative electrode and 1 M KOH as the electrolyte. This device achieved an energy density of 82.6 Wh kg−1 at a power density of 700 W kg−1 and retains 90.1% capacitance after 10,000 cycles at a current density of 10 A g−1. More importantly, DFT calculations reveal that NiCo-LDH@NiCo₂S₄ facilitates charge transfer and increases specific capacitance. This work presents a viable strategy for the design of electrode materials, facilitating the development of high-performance supercapacitors.