The purpose of this paper is to prepare a spherical modifier-modified activated carbon fiber of high specific capacitance intended for electrode materials of supercapacitor.
In this study, phenolic-based microspheres are taken as modifiers to prepare PAN-based fiber composites by electrospinning, pre-oxidation and carbonization. Pearl-chain structures appear in RFC/ACF composites, and pure polyacrylonitrile fibers show a dense network. The shape and cross-linking degree are large. After the addition of the phenolic-based microspheres, the composite material exhibits a layered pearlite chain structure with a large porosity, and the RFC/ACF composite material is derived because of the existence of a large number of bead chain structures in the composite material. The density increases, the volume declines and the mass after being assembled into a supercapacitor as a positive electrode material decreases. The specific surface area of RFC/ACF composites is increased as compared to pure fibers. The increase in specific surface area could facilitate the diffusion of electrolyte ions in the material. Owing to the large number of bead chains, plenty of pore channels are provided for the diffusion of electrolyte ions, which is conducive to enhancing the electrochemical performance of the composite and improving the RFC/ACF composite and the specific capacitance of the material. The methods of electrochemical testing on symmetric supercapacitors (as positive electrodes) are three-electrode cyclic voltammetry, alternating current impedance and cycle stability.
The specific capacitance value of the composite material was found to be 389.2 F/g, and the specific capacitance of the electrode operating at a higher current density of 20 mA/cm2 was 11.87 F/g (the amount of the microsphere modifier added was 0.3 g). Using this material as a positive electrode to assemble into asymmetrical supercapacitor, after 2,000 cycles, the specific capacitance retention rate was 87.46 per cent, indicating excellent cycle stability performance. This result can be attributed to the fact that the modifier embedded in the fiber changes the porosity between the fibers, while improving the utilization of the carbon fibers and making it easier for electrolyte ions to enter the interior of the composites, thereby increasing the capacitance of the composites.
The modified PAN-based activated carbon fibers in the study had high specific surface area and significantly high specific capacitance, which makes it applicable as an efficient and environment-friendly absorbent, as well as an advanced electrode material for supercapacitor.
The authors gratefully acknowledge the National Key Research and Development Program of China (Grant Numbers 2017YFD0500706 and 2017YFD0500603), National Natural Science Foundation of China (Grant Numbers 31570929 and 31771000), Natural Science Foundation of Heilongjiang Province (Grant Number C2017058), Innovation Foundation of Harbin (Grant Number 2017RAXXJ001), Students Innovation and Entrepreneurship Training project of China (Grant Number 201810212020), Graduate Student Innovation Research Project Funding of Heilongjiang University (Grant Number YJSCX2018-061HLJU) and Key Scientific Technological Planning Project of Harbin (Grant Number 2016AB3BN036).
Guo, L., Zhu, L., Ma, L., Zhang, J., Meng, Q., Jin, Z., Liu, M. and Zhao, K. (2019), "Bead chain structure RFC/ACF by electrospinning for supercapacitors", Pigment & Resin Technology, Vol. 48 No. 5, pp. 439-448. https://doi.org/10.1108/PRT-08-2018-0074
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