Polyaniline/carbon nanotube core–shell hybrid and redox active electrolyte for high-performance flexible supercapacitor

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

“…The energy density and power density of energy storage devices are very important for their practical application. As can be seen in Figure 4D, the 0.4 M Fe 2+ /PANI symmetric SC with 1 M H 2 SO 4 + 0.5 M Fe 2+ /Fe 3+ electrolyte processed an energy density as high as 218.1 Wh kg −1 at a power density of 1854.4 W kg −1 , which was not only better than that of the other samples, such as PANI in a 1 M H 2 SO 4 electrolyte (24.9 Wh kg −1 at 4437.6 W kg −1 ), 0.4 M Fe 2+ /PANI in a 1 M H 2 SO 4 electrolyte (27.35 Wh kg −1 at 4318.4 W kg −1 ) (Figure 3D), and PANI in a 1 M H 2 SO 4 + 0.5 M Fe 2+ /Fe 3+ electrolyte (196 Wh kg −1 at 1834.6 W kg −1 ) (Figure 4D), but also higher than those of other reports on PANI-based electrode materials tested in a H 2 SO 4 + Fe 2+ /Fe 3+ electrolyte, including PANI (22.1 Wh kg −1 at 774.0 W kg −1 ) [42] and PANI/CNT (22.9 Wh kg −1 at 700.1 W kg −1 ) [43].…”

“…Also, both the Rs of PANI in the 1 M H 2 SO 4 (Figure 6C) and the 1 M H 2 SO 4 + 0.5 M Fe 2+ /Fe 3+ (Figure 6B) electrolyte was less than that of 0.4 M Fe 2+ /PANI, which can be attributed to the amorphous configuration of PANI with lower charge delocalization and a thinner polymer nanofiber structure formed in the presence of Fe 2+ . The pseudocapacitance contributed by both Fe 2+ /PANI electrodes and the Fe 2+ /Fe 3+ redox additive in the electrolyte resulted in the oblique line deviating from a perfect vertical line in the low-frequency region, the diffusion-controlled doping/undoping of PANI, and the Fe 2+ /Fe 3+ redox reaction leading to the Warburg behaviors as shown in the plots [43,61].…”

“…The total capacitance of the SC (C total , F g −1 ), the specific capacitance of a single electrode (C s , F g −1 ), the energy density (E, W h Kg −1 ), and the power density (P, W Kg −1 ) were calculated according to these equations:Ctotal=I×ΔnormaltnormalV×m Cs=4×Ctotal E=I×∫Vdtm normalP=3600EΔnormaltwhere I is the charge/discharge current (A), Δt is the discharge time (s), V is the potential drop in the discharge progress, ∫Vdt is the galvanostatic discharge current area, and m denotes the total mass of the PANI electrodeposited for both electrodes [42,43,46].…”

“…These redox media can afford additional capacitive contributions through their reversible electrochemical reactions and can improve the electrochemical performance of assembled symmetric/asymmetric SCs. Electrolytes with a variety of redox-active additions have been studied, such as H 2 SO 4 + FeBr 3 and KCl + VOSO 4 [36,37], H 2 SO 4 + KI, H 2 SO 4 + VO 2+ /VO 2 + and KOH + K 3 Fe(CN) 6 [38,39,40], H 2 SO 4 + hydroquinone [41], and H 2 SO 4 + Fe 2+ /Fe 3+ [42,43,44]. Among these, active electrolytes containing Fe 3+ /Fe 2+ redox couples are easily available and cost effective, and they have been shown to be promising electrolytes in SCs, where PANI has been found to exhibit an enhanced C s of 1062 F g −1 at a current density of 2 A g −1 [42].…”

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

“…Therefore, an asymmetric super-capacitor was developed and assembled by matching different anode and cathode materials in order to realize a wider working voltage range [ 3 , 4 , 5 ]. Moreover, transition metal oxides or conductive polymers that theoretically possessed remarkable pseudo-capacitance were usually studied as electrode materials in the capacitors [ 6 , 7 ]. The electrochemical capacitive performance of the transition metal oxides, such as manganese dioxide (MnO 2 ), ruthenium oxide (RuO 2) , cobalt oxide (Co 3 O 4 ), and molybdenum oxide (MoO 3 ), have been extensively investigated [ 8 , 9 , 10 , 11 ].…”