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.