An Organo-Fluorine Compound Mixed Electrolyte for Ultrafast Electric Double Layer Supercapacitors

Fluorine chemistry has gained tremendous attention in the area of electrochemical energy devices such as lithium ion batteries, fuel cells and solar cells. With the advent of novel fluorinating systems, it is interesting to study the effect of fluorine on the electrochemical characteristics of such energy devices. In this study, an organo-fluorine compound, SelectfluorTM (F-TEDA) is used as a co-electrolyte with organic electrolyte, tetrabutyl ammonium tetrafluoroborate (TBABF4) to facilitate the formation of electrostatic double layer. F-TEDA is a commercially available N−F fluorinating agent existing as ion-pair resembling conventional electrolytes. The ionic conductivity of 0.5 M F-TEDA/TBABF4 is found to be 5.10 mS/cm that increases on introduction of ppm level of water indicating its sensitivity towards water. Symmetric Swagelok-type cells in two electrode geometry are fabricated using carbon cloth as electrodes and F-TEDA/TBABF4 as electrolyte. F-TEDA/TBABF4 in inert condition (Device C) exhibits superior supercapacitive behaviour in terms of high rate capability and capacitance retention. The devices are assembled in ambient and inert conditions to examine the influence of moisture on supercapacitor performance. Interestingly, device based on F-TEDA assembled in ambient condition despite of decrease in voltage window exhibits a remarkable increase in specific capacitance by 102 % with respect to control electrolyte.