Carbon-encapsulated tungsten oxide nanowires as a stable and high-rate anode material for flexible asymmetric supercapacitors

Abstract

An effective strategy for carbon encapsulation was developed to increase the capacitive performance of WO3−x nanowires as a high-energy and stable anode material for flexible asymmetric supercapacitors.

Enhancing the Capacitive Storage Performance of Carbon Fiber Textile by Surface and Structural Modulation for Advanced Flexible Asymmetric Supercapacitors

“…While at a discharge current density of 4 mA cm −2 , a remarkable areal capacitance up to 1200 mF cm −2 (Figure c) was achieved by APCFT electrode, which is as ≈3750, ≈343, and ≈2.8 times large as the CFT (0.32 mF cm −2 ), PCFT (3.50 mF cm −2 ), and ACFT (425 mF cm −2 ) electrodes, respectively. The presented areal capacitance of APCFT electrode is also superior to those of the recently reported carbon‐based and some metal oxides anodes, such as chemical activated carbon cloth (90 mF cm −2 at 0.5 mA cm −2 ), electrochemically activated carbon cloth (756 mF cm −2 at 6 mA cm −2 ), WO 3− x /MoO 3− x core/shell nanowires (480 mF cm −2 at 2 mA cm −2 ), and C@WO 3 nanowires (1080 mF cm −2 at 1 mA cm −2 ) . Even at high discharge current densities of 20 and 80 mA cm −2 , more than 80.5% and 59.5% capacitance retention could be maintained by the APCFT electrode, presenting its fast energy storage capability.…”

“…c) Areal capacitance–current density relation of PCFT, ACFT, and APCFT electrodes. Add with specific capacitances of other previously reported electrodes for comparison . d) Cyclic stability of the APCFT electrode collected at 100 mV s −1 for 25 000 cycles.…”

Anchoring carbon layers and oxygen vacancies endow WO3−x/C electrode with high specific capacity and rate performance for supercapacitors

“…However, the binding energy was lower than that for the corresponding ne spectra of W4f 7/2 and W4f 5/2 in the WO 3Àx /C nanowires by 0.17 eV. 10,14,24,25 The shis in the binding energies can provide valuable information. As previously reported, this evidences the introduction of oxygen vacancies and the perturbation of the electronic environment aer incorporating a small amount of N anions with different electronegativities.…”

“…These results are considerably superior to that for previously reported WO 3 -based symmetric supercapacitors. 10,12,24,29 The prominent electrochemical performance of the developed SSC device implied that the hierarchical carbon layer-anchored WO 3Àx /C nanowire electrode is a promising candidate for practical applications in next-generation energy storage devices, presenting a new solution of carbon layers and oxygen vacancies integrated into metal oxides in the process of material preparation.…”

“…[21][22][23] Recently, Gong et al reported the growth of carbon-encapsulated WO 3Àx nanowires via a facile hydrothermal and annealing treatment, achieving areal specic capacitance of 786.8 mF cm À2 at the current density of 20 mA cm À2 , but their rate properties were not satisfactory. 24 Tian et al reported the production of W 18 O 49 nanobers by the addition of ethanol and electrodeposition of a polyaniline lm, displaying specic capacitance of 440 F g À1 at the current density of 1 A g À1 . However, they could not display a long cycling life.…”