Synthesis of NiCo2O4 nanostructures with different morphologies for supercapacitor

Designing nanostructure of electrode materials for boosting their electrochemical activity is a crucial issue to further development in the renewable energy industry. Here we have synthesized three NiCo2O4 crystals with different morphologies by simply adjusting hydrothermal reaction conditions. The NiCo2O4 nanoflake array grown on Ni foam is found to possess highly ordered structure with large specific surface area, providing vast reactive sites and facilitating the transfer of electrons and electrolyte ions. As a result, NiCo2O4 nanoflake array displays an improved specific capacitance of 854.7 F g−1 at 1 A g−1 and even kept it as high as 745.1 F g−1 at 10 A g−1. Furthermore, the final capacitance remains 82.9% after 10,000 charge-discharge process at 20 A g−1. An asymmetric supercapacitor (ASC) composed of NiCo2O4 nanoflake array and active carbon enables maximum energy density of 25.7 Wh kg−1 at a power density of 765.5 W kg−1. In addition, this work will broaden our vision to improve the performance of electrodes for supercapacitor by ingeniously constructing their structure. [Display omitted] •Three NiCo2O4 crystals with different structures are made by a hydrothermal method.•NiCo2O4 nanoflake array has highly ordered structure and good conductivity.•The shape of an individual NiCo2O4 nanoflake is orthohexagonal.•NiCo2O4 nanoflake array shows excellent electrochemical performance.•The energy storage mechanism of electrode materials is discussed in detail.