1D hierarchical MnCo₂O₄ nanowire@MnO₂ sheet core–shell arrays on graphite paper as superior electrodes for asymmetric supercapacitors

Heterostructured metal oxide core–shell architectures have attracted considerable attention owing to their superior electrochemical performance in supercapacitors compared to a single structure. Here, we report a simple and effective synthesis of hierarchical MnCo₂O₄ nanowire@MnO₂ sheet core–shell nanostructures anchored on graphite paper for use in supercapacitors. The proposed electrode exhibits a specific capacitance of 2262 F g⁻¹ at 1 A g⁻¹. In addition, good rate capability and excellent cycling performance are observed. An asymmetric supercapacitor with operating potential at 1.6 V is demonstrated using MnCo₂O₄@MnO₂ as cathode and graphene/nickel foam (NF) as anode. The MnCo₂O₄@MnO₂//graphene/NF asymmetric device shows a high energy density of 85.7 Wh kg⁻¹ at a power density of 800 W kg⁻¹ while maintaining a high energy density of 34.7 Wh kg⁻¹ at 24 kW kg⁻¹. Moreover, the device demonstrates a long-term cycling stability of 81.6 % retention of its initial specific capacitance.