Core-sheath heterostructure of MnCo₂O₄ nanowires wrapped by NiCo-layered double hydroxide as cathode material for high-performance quasi-solid-state asymmetric supercapacitors

Core-sheath heterostructures composed of MnCo₂O₄ nanowires wrapped by nanosheets of NiCo-layered double hydroxide (NiCo-LDH) have been obtained on nickel foam (NF) substrate (MnCo₂O₄@NiCo-LDH/NF). In which, the MnCo₂O₄ nanowires play role as core structure, while interconnected NiCo-LDH nanosheets acts as the sheath material. The fabrication is achieved by coupling hydrothermal preparation with electrochemical deposition. This heterostructure combines the advantages of interconnection among NiCo-LDH nanosheets, the high conductivity of MnCo₂O₄, with excellent mechanical strength and 3D open structure of NF. Benefiting from the core-sheath heterostructures and the interaction among these multi-component, when the MnCo₂O₄@NiCo-LDH/NF composite is utilized as cathode material for supercapacitors, it delivers a superior specific capacitance of 4555.0 F g⁻¹ at a current density of 1 A g⁻¹ and maintains a capacitance of 78.7% after 5000 successive charging-discharging cycles using 6M KOH aqueous as electrolyte. In addition, the composite has been used as electrode for assembling the MnCo₂O₄@NiCo-LDH/NF//AC quasi-solid-state asymmetric supercapacitor (ASC) using active carbon (AC) as counter electrode. Such an ASC exhibits an outstanding energy density of 21.3 W h kg⁻¹ at a power density of 160.0 W kg⁻¹ and can light up the green LED indicator for more than 30 min, showing promising prospect for practical applications.