Nonaqueous, Redox‐Active Gel Polymer Electrolyte for High‐Performance Supercapacitor

Abstract

Redox‐active liquid or polymer‐based aqueous electrolytes are widely reported in carbon‐based supercapacitors, enhancing their performance substantially due to the involvement of fast redox reaction(s) at the electrode–electrolyte interface. Here, a nonaqueous, ionic liquid (IL)‐based redox‐active gel polymer electrolyte (GPE) as a potential supercapacitor electrolyte is demonstrated. This electrolyte, comprising IL 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide added with redox agent NaI, immobilized in poly(vinylidenefluoride‐co‐hexafluoropropylene), offers excellent thermal, mechanical, and electrochemical stability with high ionic conductivity of ≈3.81 × 10−3 S cm−1 at room temperature. The redox‐additive NaI not only increases the ionic conductivity of electrolyte but also introduces redox behavior at the interfaces of porous activated carbon supercapacitor resulting in high specific capacitance (≈334 F g−1) and high specific energy and power (≈26.1 and ≈18 kw kg−1, respectively). The capacitor with redox‐active nonaqueous GPE offers stable performance up to 10 000 charge–discharge cycles with ≈5% initial fading only. This study opens a novel approach to prepare highly stable redox‐active GPEs for high‐performance supercapacitors.

Facile In Situ Synthesis of Co(OH)2–Ni3S2 Nanowires on Ni Foam for Use in High-Energy-Density Supercapacitors

“…The response current density increases linearly with increasing scan rate and the cathodic and cathodic current peaks are shifted more positively and negatively, respectively. However, as the scan rates increase, clear redox peaks are observed, indicating the slow electron or ion transfer kinetics of the interfacial redox reactions [ 61 ]. Conversely, the voltammograms of Co 0.5 –Ni 3 S 2 at scan rates of ≤20 mV s −1 retain their original shapes, and the currents are higher than that of Ni 3 S 2 , indicating the rapid kinetics of electron or ion transfer in the interfacial redox reactions [ 62 ].…”

Performance of ionic liquid–based quasi‐solid‐state hybrid battery supercapacitor fabricated with porous carbon capacitive cathode and proton battery anode

“…Figure 3C,D shows the variation of ionic conductivity ( σ ) of PVdF‐HFP/EMIMTF (ILGPE#1) and PVdF‐HFP/EMIMTF/NH 4 Tf (ILGPE#2) with temperature ( σ vs 1/ T plot). The curved nature of temperature‐dependent conductivity can be explained by Vogel‐Tammen‐Fulcher (VTF) type thermally activated behavior 39 and is well described by the equation: where is A the pre‐exponential factor, T 0 is equilibrium glass transition temperature (K), and B is pseudo activation energy (eV) which is associated with the rate at which viscosity of the system changes with temperature. The value of A , B , and T 0 for both polymeric film has been estimated from nonlinear least square fitting and listed in Table 1.…”

Highly Flexible and Tailorable Cobalt‐Doped Cross‐Linked Polyacrylamide‐Based Electrolytes for Use in High‐Performance Supercapacitors

“…Gel polymer electrolytes (GPEs), merging the advantages of both solid and liquid electrolytes, [21] have demonstrated superior electrochemical performances, wide thermal operating ranges, excellent flexibilities, and minimal leakage issues. [22][23][24][25] Polyacrylamide (PAM) is a highly water-absorbing polymer and forms a soft gel when hydrated. The pure form of PAM is not quite stretchable.…”

“…Redox additives or mediators have recently been incorporated into the polymer networks to enhance the capacitance, power density, energy density, cyclic, and charge-discharge characteristics of SC systems by providing fast redox reactions between the electrolyte and electrode interface. [31][32][33] More recently, supercapacitive properties of SCs have been remarkably advanced by incorporation of redox-active additives such as sodium iodide (NaI), [22] potassium iodide (KI), [34] 1-butyl-3methylimidazolium iodide (BMIMI), [23] potassium bromide (KBr), [35] potassium ferricyanide (K 3 [Fe(CN) 6 ]), [36,37] ammonium molybdate ((NH 4 ) 2 MoO 4 ), [33] sodium molybdate (Na 2 MoO 4 ), [38] iron(III) bromide (FeBr 3 ), [39] p-phenylenediamine (PPD), [40] and methylene blue (MB). [41] In this context, the application of PAMbased polyelectrolytes, incorporated with Co as a redox additive, in SC systems may lead to promising outcomes, which have not been reported yet to the best of our knowledge.…”

“…Solid, aqueous, gel polymer, organic, and redox type electrolytes and ionic liquids have been widely studied for EDLCs applications. Gel polymer electrolytes (GPEs), merging the advantages of both solid and liquid electrolytes, [21] have demonstrated superior electrochemical performances, wide thermal operating ranges, excellent flexibilities, and minimal leakage issues [22–25] …”