Hierarchical MnO 2 nanosheets coated on MnCo 2 O 4.5 nanoneedles as advanced electrode for high-efficient hybrid supercapacitor

The MnCo 2 O 4.5 @MnO 2 composite nanomaterial was successfully designed and synthesized via successive hydrothermal and subsequent calcination methods, in which MnO 2 nanosheets coated on MnCo 2 O 4.5 nanoneedle arrays were directly grown on Ni foam. Compared with pristine MnCo 2 O 4.5 nanoneedle electrode, MnCo 2 O 4.5 @MnO 2 composite electrode exhibits a high specific discharge capacitance of 1155 F g -1 at a current density of 1.43 A g -1 , the capacitance retention of 93.4% after 5000 cycles, and low initial internal resistance of 1.9 Ω. The results reveal that the rational design of MnCo 2 O 4.5 @MnO 2 electrode with such structure and composition is an effective strategy to improve electrochemical performances of MnCo 2 O 4.5 . Due to unique nanostructure and brilliant electrochemical properties of MnCo 2 O 4.5 @MnO 2 electrode, the fabricated hybrid supercapacitor based on MnCo 2 O 4.5 @MnO 2 positive electrode and activated carbon negative electrode delivers the wide operating voltage window of 1.6 V, a capacitance retention of 87.8% after 8000 continuous charge-discharge cycles at a current density of 1.33 A g -1 , the maximum energy density of 40.8 Wh kg -1 at a power density of 263.9 W kg -1 , and highest power density of 1336.6 W kg -1 to achieve an energy density of 24.4 Wh kg -1 . Herein, the designed MnCo 2 O 4.5 @MnO 2 composite is a distinguished candidate material for hybrid supercapacitor.