Fluorinated Ether‐Based Electrolyte for Supercapacitors with Increased Working Voltage and Suppressed Self‐discharge

Abstract

The application of supercapacitors for long-term energy storage is largely limited by their low energy density and self-discharge behavior. Finding a way to effectively increase the voltage window (and thus the energy density) and suppress the selfdischarge of supercapacitors is a huge research challenge. Herein, by introducing a fluorinated ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), in triethyl ammonium tetrafluoroborate/acetonitrile solution as the electrolyte of supercapacitors, improved electrolyte stability could be achieved. As a result, a working voltage of 3.6 V was obtained, much higher than the typical working voltage of 2.7 V for acetonitrile-based electrolytes without TTE. In addition, reduced self-discharge was attained after adding TTE in the electrolyte. When charged to 3.6 V, the supercapacitors using TTE-based electrolyte exhibited an open circuit voltage (OCV) decay of 2.03 V after 24 h, lower than that of the supercapacitors without TTE (2.60 V). Mechanistic analysis indicated that the slower self-discharge could be attributed to the suppressed activation-controlled faradaic reaction process caused by electrolyte decomposition.

Tuning of Ionic Liquid–Solvent Electrolytes for High-Voltage Electrochemical Double Layer Capacitors: A Review

“…Subsequent studies found that adding a fluorinated ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), into TEABF 4 /AN electrolyte could improve the stability of the electrolyte. As a result, a high working voltage of 3.6 V was assembled, which was much higher than the typical working voltage of 2.7 V for AN-based electrolytes without TTE [92]. In addition, the leakage current of TEABF 4 -TTE/AN was smaller than that of electrolyte without TTE at the same charging voltage, and no decomposition of electrolyte was observed at 3.6 V. When charged to 3.6 V, the open-circuit voltage of ELDC with TEABF 4 -TTE/AN decayed by 2.03 V after 24 h, which was lower than that of the EDLC without TTE (2.60 V).…”