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

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.