Asymmetric supercapacitor based on nano-flower Ni-Co-O/C electrodes

Ni-Co-O material is the most representative polymetallic compound and has exhibited excellent energy storage properties. However, the high cost of composite restricts the practical application of Ni-Co-O material. In this paper, a simple and low-cost method is used to grow Ni-Co-O/C nanoarrays directly on a conductive matrix. The results show that the three-dimensional nanoflower-like Ni-Co-O/C composite has better electrochemical performance than that of the nanosheet Co-O/C binary composite. This microstructure provides a shorter path for electron transport, making the material high electron transport efficiency. The specific capacitance of Ni-Co-O/ C/AC asymmetric supercapacitor can reach 128.75 mF cm-2 at 2 mA cm-2. Under the condition of 20 mA cm-2, after 4000 cycles of charge and discharge, the capacitance retention rate is maintained at 99.8 %. This 3D flower-like structure not only helps provide an open framework and rapid ion diffusion, but also exposes more active sites and enhances charge storage performance. Ni-Co-O/C calcined in nitrogen shows more abundant defect structure and larger specific surface area, which is further conducive to Ni-Co-O/C electrodes to expose more active sites and enhance the rapid diffusion and reaction of electrolyte ions.