Suppressing the self-discharge of redox-enhanced electrochemical capacitors by incorporating redox-active molecules into deep eutectic solvent (DES)

Abstract

Redox-enhanced electrochemical capacitors (Redox ECs) are being developed as a system that combines the high energy of the battery and the high power of the capacitor. In redox ECs, the selection of an electrolyte is important because soluble redox-active molecules in the electrolyte improves energy by using faradaic redox reactions at the electrode/electrolyte interface on high-surface-area electrodes. . In this thesis, redox-active DES (deep eutectic solvent) is developed as high-performance electrolyte by adding redox-active molecules into deep eutectic solvent. The utilization of DES as electrolyte has several advantages compared to conventional electrolytes: (1) wide electrochemical stability window. (2) non-flammability. (3) environment friendliness. Here, redox-active DES was prepared using ethaline as DES and ethyl viologen dibromide as redox-active electrolyte. As a result of using redox-active DES as an electrolyte, our system showed coulombic efficiency of over 90% and specific energy of 49 Wh/kg. In addition, the self-discharge problem was greatly suppressed by using the hopping transport mechanism and hole effect of DES.