SiO2 anchored stacked-petal structure CoO-NiO/CNF as electrodes for high-rate-performance supercapacitors

The composites of transition metal oxide and carbon nanofibers (CNF) are promising electrode materials for supercapacitors in alkali solutions. However, the weak binding and unsatisfactory rate performance limit their application. To improve the weak binding, this study prepared the SiO2-modified carbon nanofibers (Si1-C) via electrospinning. Then the fully encapsulated CoO-NiO (NiCo@Si1-C) was fabricated on Si1-C by solvent-thermal and calcination. As is revealed, CNF containing SiO2 is conducive to forming a full coverage of CoO-NiO coating with a stacked petal structure. More importantly, nano-SiO2 plays the anchoring role of NiO-CoO and CNF, making the combination more firmly. The NiCo@Si1-C delivers a specific capacitance of 518.1 F g-1 at 0.5 A g-1, almost 2.25 times that of NiCo@Si0-C (229.9 F g-1 at 0.5 A g-1). When the current density increases to 50 A g-1, it is only 3.9 % lower than the capacitance (497.9 F g-1), which means a high rate performance. Moreover, asymmetric supercapacitor devices are assembled with activated carbon (NiCo@Si1-C//AC) with an energy density of 11.7 Wh kg -1, even at a high power density of 14,000.7 W kg -1.

Automated summary

SiO2-modified carbon nanofibers (Si1-C) were prepared by electrospinning, and a fully encapsulated CoO-NiO (NiCo@Si1-C) was fabricated on Si1-C. CNF with SiO2 facilitated the formation of a CoO-NiO coating with a stacked petal structure, while nano-SiO2 acted as an anchor between NiO-CoO and CNF, enhancing the binding. NiCo@Si1-C exhibited a specific capacitance of 518.1 F g-1 at 0.5 A g-1, 2.25 times that of NiCo@Si0-C. It also showed a low capacitance decrease of 3.9% at a high current density of 50 A g-1, indicating excellent rate performance. Furthermore, an asymmetric supercapacitor device (NiCo@Si1-C//AC) achieved an energy density of 11.7 Wh kg -1 and a high power density of 14,000.7 W kg -1.