NiCo2O4 nanoneedle-nanosheet hybrid structure on CC substrate for high-performance flexible supercapacitors

In this paper, three different morphologies of NiCo2O4 nanoarrays, namely, nanosheet (S-NiCo2O4), nanoneedle (N-NiCo2O4) and their hybrid nanostructure (M-NiCo2O4) were successfully prepared on flexible carbon cloth (CC) by a hydrothermal method. The structures, surface morphologies and compositions of the samples were respectively characterized by XRD, SEM, EDS, and XPS, and the effect of NiCo2O4 morphologies on the electrochemical performances was systematically investigated. It is found that the M-NiCo2O4/CC electrode demonstrates the best supercapacitive performance among the three kinds of samples, typically its specific capacitance is 1347.4 F/g at 1 Aug (1509.1 F/cm(2) at 1 mA/cm(2)), much higher than that of S-NiCo2O4 (938.4 Fig at 1 Aug) and N-NiCo2O4 (1022.4 Fig at 1 Aug). Meanwhile, the M-NiCo2O4/CC sample exhibits excellent rate capability (81.6%, from 1 Aug to 15 Aug) and cycling stability (92.4% retention after 10,000 cycles). In addition, an flexible solid-state asymmetric supercapacitor (ASC) with M-NiCo2O4/CC as positive electrode manifests great capacity retention (94% after 5000 cycles) and outstanding energy density of 41.7 Wh/kg at the power density of 750 W/kg. Moreover, the charge-discharge time shows no significant change after 2000 bends, demonstrating its application potential in the field of flexible SCs. The excellent performance is attributed to the unique hybrid porous structure of one-dimensional (1D) nanoneedles and two-dimensional (2D) nanosheets, (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

In this study, three different morphologies of NiCo2O4 nanoarrays were successfully prepared on flexible carbon cloth by a hydrothermal method. The hybrid nanostructure showed the best supercapacitive performance, with high specific capacitance, excellent rate capability, cycling stability, and energy density. The flexible solid-state asymmetric supercapacitor made with the hybrid nanostructure as the positive electrode exhibited great capacity retention and outstanding energy density, indicating its potential application in flexible energy storage devices.