Stabilities of flexible electrochemical capacitors based on polypyrrole/carbon fibers in different gel electrolytes
Chinese Journal of Polymer Science(2017)
Abstract
Flexible electrochemical capacitors (ECs) are vitally important as the emerging flexible electronics. We have prepared polypyrrole doped with counter ion of Cl − on carbon fibers (PPy-Cl/CFs) via the simple electrochemical deposition method. The flexible ECs based on PPy-Cl/CFs electrodes have been assembled by using H 3 PO 4 /poly(vinyl alcohol) (PVA), H 2 SO 4 /PVA, LiClO 4 /PVA, KCl/PVA and LiCl/PVA as gel electrolytes. The capacitive properties of ECs have been systematically evaluated with electrochemical methods. The results show that the cells with H3PO4/PVA electrolyte exhibit good cyclic stability (91.5% retention after 15000 cycles) although PPy-Cl/CFs has moderate specific capacitance in H 3 PO 4 /PVA (41.6 mF·cm −1 or 52.0 F·cm −3 ). However, the ECs in other electrolytes have poor cyclic stability. Further electrochemical analysis reveals that the doping/dedoping processes of PPy-Cl/CFs are different in the five electrolytes, and X-ray photoelectron spectra demonstrate that the ratios of counter anions in PPy’s oxidized states to those in reduced states are obviously different when PPy-Cl/CFs are kept in reduced or oxidized states in the five electrolytes. The results also illustrate why the capacitors using H 3 PO 4 /PVA as electrolyte exhibit good cyclic stability. Furthermore, a light emitting diode (LED) with a threshold voltage of 2.5 V can be lighted by three ECs connected in series.
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Key words
Polypyrrole,Electrochemical capacitors,Stability,Gel electrolytes
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