In situ-fabricated quasi-solid polymer electrolytes incorporating an ionic liquid for flexible supercapacitors

In this study, quasi-solid polymer electrolytes incorporating an ionic liquid (ILQSEs) fabricated in different organic solvents via a thermally-initiated polymerization strategy were investigated for flexible supercapacitors (SCs). It was found that low-viscous acetonitrile (AN) with a strongly-polar nitrile group was remained in the polymer matrix, which favored a higher ionic conductivity, wider electrochemical window, and better thermal stability of the ILQSE compared to its propylene carbonate (PC) counterpart. Moreover, the in situ polymerized quasi-solid electrolyte achieved close contact with the porous carbon electrode, accompanied by the favorable permeation of the IL into the electrode for enhancing the ion-transport kinetics and interface stability. Consequently, the as-assembled SC with the AN-based ILQSE delivered a high specific energy and specific power, excellent cycle stability, and reliable safety.