Redox-Active Gel Electrolyte Combined with Branched Polyaniline Nanofibers Doped with Ferrous Ions for Ultra-High-Performance Flexible Supercapacitors

Abstract

In this work, the effects of utilizing an Fe2+/Fe3+ redox-active electrolyte and Fe2+-doped polyaniline (PANI) electrode material on the performance of an assembled supercapacitor (SC) were studied. The concentration of the redox couple additive in the electrolyte of the SC was optimized to be 0.5 M. With the optimized concentration of 0.4 M Fe2+, the doped PANI branched nanofibers electropolymerized onto titanium mesh were much thinner, cleaner, and more branched than normal PANI. A specific capacitance (Cs) of 8468 F g−1 for the 0.4 M Fe2+/PANI electrode in the 1 M H2SO4 + 0.5 M Fe2+/Fe3+ gel electrolyte and an energy density of 218.1 Wh kg−1 at a power density of 1854.4 W kg−1 for the resultant SC were achieved, which were much higher than those of the conventional PANI electrode tested in a normal H2SO4 electrolyte (404 F g−1 and 24.9 Wh kg−1). These results are among the highest reported for PANI-based SCs in the literature so far and demonstrate the potential effectiveness of this strategy to improve the electrochemical performance of flexible SCs by modifying both the electrode and electrolyte.

Electrodeposited Polyaniline Nanofibers and MoO3 Nanobelts for High-Performance Asymmetric Supercapacitor with Redox Active Electrolyte

“…The cyclic stability of the ASC was also studied. The capacitance of the ASC was even increased to 109% after 1000 cyclic tests, as shown in Figure 5 c. This is in contrast with our recently reported result of PANI symmetric capacitors with the similar redox active electrolyte, which was so unstable that only ~50% capacitance was retained after 1000 cycles [ 18 ]. Moreover, the coulombic efficiency was increased from 84% for the first cycle and remained stable at a high level of nearly 90% after 100 cycles, indicating a good reversibility of the ASC [ 33 ].…”

“…The above oxidative p-doping reaction takes place in conducting PANI with both cations and anions being involved in the electrochemical redox processes of PANI [ 31 ]. The synergistic effect between PANI nanofibers and redox Fe 2+/3+ ion pair promotes the capacitance and cycling stability of the electrode, which has also been demonstrated recently [ 17 , 18 ]. To further study the electrochemical performance of PANI/Ti electrode in the redox active electrolyte, more CV and GCD tests were conducted.…”

“…Ren et al reported that the specific capacitance of PANI in its symmetric capacitor was promoted to be 1062 F g −1 at 2 A g −1 by utilizing the redox active electrolyte of 1 M H 2 SO 4 + 0.8 M Fe 3+ /Fe 2+ [ 17 ]. By doping PANI electrode materials with iron ions, an even higher specific capacitance of this conductive polymer was achieved in the electrochemically active electrolyte in previous work [ 18 ]. Senthilkumar et al reported a nearly two-fold improved specific capacitance of 912 F g −1 and energy density of 19.04 Wh kg −1 by adding 0.08 M KI to 1 M H 2 SO 4 electrolyte [ 16 ].…”

Flexible and stretchable polyaniline supercapacitor with a high rate capability

“…Huang and colleagues designed a monolithic integrated supercapacitor with PANI, which showed cycling retention of 92.8% after 6500 cycles 9 . Additionally, modifications of electrodes or electrolyte were also carried out to further improve the performance of PANI supercapacitors 10–12 . Typically, flexible supercapacitor fabrication based on conducting polymers has been combined with serpentine and wavy structures or an elastomer substrate, 13–20 such as carbon nanotubes, graphene/graphene oxide or carbon cloth.…”

A Polyaniline‐Based Redox‐Active Composite Gel Electrolyte with Photo‐Electric and Electrochromic Properties

“…[11] In addition to the applications of the gels as the electrode material, due to their low volatility, high thermal stability, and safety, gels are one of the most promising candidate materials as the electrolyte in various electrochemical devices. [13,[18][19][20][21][22] Deka et al have found a significant enhancement of the ionic conductivity and interfacial stability in a composite gel electrolyte by incorporating dedoped (insulating form) PANI nanofibers to the gel. [7] Nath et al have reported a solid-state DSSC with 2.18 % efficiency using a composite hydrogel electrolyte containing PANI, PVA, and carbon nanotubes.…”