Study of the Effects of Ionic Liquids as Electrolyte Addictive for Redox Flow Batteries

Abstract

Many researches on non-aqueous redox flow batteries(RFBs) show that they usually have a wider potential window and higher operating temperature than aqueous RFBs. Relatively low conductivity of solvent is a limitation of good performance. To solve this problem, several ionic liquids including 1-Butyl-3-methylimidazolium hexafluorophosphate(BMImPF6), 1-Butyl-3-methylimidazolium tetrafluoroborate were synchronized and introduced as electrolyte addictive. Cyclic voltammetry was performed and results shows that solvent containing BMImPF6 has highest diffusion coefficient, (4.94 ~ 8.00) ? 10-6 for V(II)/V(III) redox couple and (6.30 ~ 10.20) ? 10-6 for V(III)/V(IV) redox couple. A set of cells was designed to avoid corrosion by vanadium and charge-discharge test was performed. Approximate 50% coulombic efficiency was achieved using BMImPF6 as supporting electrolyte.