Hetero-structure arrays of MnCo2O4 nanoflakes@nanowires grown on Ni foam: Design, fabrication and applications in electrochemical energy storage

Abstract

In this work, we report a two-step synthesis of hierarchical heterostrtuture based MnCo2O4 nanoflakes@PPy nanowires arrays on Ni foam using facile hydrothermal method and subsequent annealing process. The physico-chemical and surface properties of the MnCo2O4 electrodes were investigated through XRD, FESEM, Raman, BET and XPS analysis. Owing to the exclusive hetero-structure arrays and the synergetic effect of MnCo2O4@PPy electrode displays higher specific capacitance of 2933 Fg-1 than bare MnCo2O4 (2144 Fg-1). Moreover, the heterostructure MnCo2O4@PPy electrode exhibits 86.7% capacitance retention after 5000 cycles at 20Ag-1, whereas the bare MnCo2O4 electrode is only 80%. This can be attributed to the surface of MnCo2O4 offers a conductive network for rapid electron transfer by coupling of PPy matrix, which support the transport of electrons from PPy to MnCo2O4, benefiting for improving the electrochemical performance. Further, the asymmetric supercapacitor cell (ASC) is fabricated using MnCo2O4/NF@PPy and Activated carbon (acetylene black: carbon black: PVDF) as the positive and negative electrodes. The devices showed high energy density (78.5 Whkg−1 at 1121 Wkg-1), and superior stability (94.3% capacitance retention after 5000 cycles at 20 Ag-1).