Electrochemical Properties of Al/Vanadium Chloride Batteries with AlCl 3 -1-Ethyl-3-methylimidazolium Chloride Electrolyte

Abstract

We have studied the electrochemical properties of vanadium chloride in molten salt containing AlCl3 and 1-ethyl-3-methylimmidazolium chloride (EMIC) with a molar ratio of 1.5/1.0 at an ambient temperature using cyclic voltammetry and the X-ray absorption near-edge structure (XANES). Cyclic voltammograms (CVs) of VCl3 contain a pair of oxidation peak at about 1.5 V vs. Al/Al3+ and reduction peak at about 0.9 V vs. Al/Al3+ assigned to the V(3) reversible arrow V(2) reaction and a pair of oxidation peak at about 0.9 V vs. Al/Al3+ and reduction peak at about 0.4 V vs. Al/Al3+ assigned to the V(2) reversible arrow V(0) reaction. The former remains in the CV after reduction and oxidation cycling. On the other hand, the latter disappears from the CV after a couple of cycles. We also investigate the effect of adding fluorobenzene (FB) to the AlCl3-EMIC salts on the solubility and electrochemical properties of VCl3. FB greatly reduces the VCl3 dissolution in the salts and improves capacity retention with reduction and oxidation cycling without change in the reaction process. (C) The Author(s) 2016. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.