Surface Engineering of Carbon via Coupled Porosity Tuning and Heteroatom‐Doping for High‐Performance Flexible Fibrous Supercapacitors

Abstract

Flexible fibrous supercapacitors (FFS) are considered the next-generation wearable energy storage devices because they provide reliable safety, ecofriendliness, and high power density. In particular, the FFS is desirable for application to wearable electronics because it can overcome disadvantages of the lithium-ion battery (LIB), such as the hazard of explosion and the complex manufacturing process. Nevertheless, the practical application of the FFS continues to be inhibited by the poor energy storage performance due to the limited specific surface area, poor electrical properties, and low wettability of the carbon fiber electrode. Herein, for the first time, the surface engineering of an FFS using nitrogen and fluorine codoped mesoporous carbon fibers (FFS-NFMCF) is described, and the synergistic effect of porosity tuning and heteroatom codoping upon the electrochemical performance is demonstrated. The resultant supercapacitor shows a high specific capacitance of 243.9 mF cm −2 at a current density of 10.0 µA cm −2 and good ultrafast cycling stability with capacitance retention of 91.3% for up to 10 000 cycles at a current density of 250.0 µA cm −2 . More interestingly, the FFS-NFMCF exhibits good mechanical properties and remarkable safety in practical application, thus demonstrating its feasibility for use in wearable electronic textiles.

Zinc‐ion battery based on heteroatom‐doped improved‐quality graphene film as a functional current collector

“…The C 1s signal of the GF, IQGF, and FN‐IQGF presented in Figure 4A‐C, respectively. Peaks were observed in the signal of the samples at ~284.5, 286.5, and 288.3 eV (C–C, C–O, and C═O bonds, respectively) 15,16 . Moreover, the ratio of oxygen‐containing groups in the various samples was verified, and shown in Figure 4D.…”

“…Peaks were observed in the signal of the samples at $284.5, 286.5, and 288.3 eV (C-C, C-O, and C═O bonds, respectively). 15,16 Moreover, the ratio of oxygen-containing groups in the various samples was verified, and shown in Figure 4D. Compared to those of the GF, the C 1s signals of the IQGF and FN-IQGF can be deconvoluted into oxygencontaining groups on their surfaces, indicating that the reduction process improved the quality of GF, which is anticipated to enhance the electrical properties and, therefore, lead an improved rate capability in the ZIBs.…”

“…In contrast, peaks corresponding to semi‐ionic C–F (~684.6 eV) and covalent C–F (~687.9 eV; Figure 4G), and pyridinic N (~398.3 eV), pyrrolic N (~399.9 eV), graphitic N (~401.1 eV), and oxidized N (~402.9 eV) were observed in the signal of FN‐IQGF, which could be attributed to the successful codoping of F and N (Figure 4J). 15 In addition, the fluorine and nitrogen codoping structure of the FN‐IQGF can increase the electrochemical performance of ZIBs owing to the electronegativities of nitrogen (3.04) and fluorine (3.98) atoms compared to that of C atom (2.55) 16 . Furthermore, C–F bonding can enhance the overall energy storage performance via the efficient use of the interface between the current collector and electrode material owing to the easy access of the ions during cycling 17 .…”

“…Furthermore, the effect of NH 4 F as a fluorine or nitrogen‐doping source on the thermal decomposition of the carbon structure was demonstrated using DSC curve (Figure 5C). Endothermic peaks were observed in the DSC curve at ~157°C and 270°C correspond to the melting point of NH 4 F and the decomposition point of residual NH 4 F, respectively 15 . To investigate the graphitic carbon and lattice defects of all the samples, their Raman spectra were obtained.…”

“…Endothermic peaks were observed in the DSC curve at $157 C and 270 C correspond to the melting point of NH 4 F and the decomposition point of residual NH 4 F, respectively. 15 To investigate the graphitic carbon and lattice defects of all the samples, their Raman spectra were obtained. Peaks were observed 5D.…”