Synthesis of a Low-Cost V<sup>3.5+</sup> Electrolyte for Vanadium Redox Flow Batteries through the Catalytic Reduction of V<sub>2</sub>O<sub>5</sub>
Hansol Choi, Debasish Mandal, Hansung Kim
Abstract
In this study, a cost-effective method for preparing a V3.5+ electrolyte for a vanadium redox flow battery (VRFB) was developed using the cheapest vanadium precursor, V2O5, through the catalytic reduction method. It is revealed that VRFBs do not operate properly with a V3.5+ electrolyte prepared by the catalytic reduction method using V2O5 salts because of the significant H+ ion consumption during the catalytic reduction reaction, contributing to a decrease in the solution’s viscosity. As a result, more vanadium ions could permeate through the membrane, increasing the imbalance between the negative and positive electrolytes. To solve this problem, the H+ ions corresponding to the amount consumed during the catalytic reduction reaction were replenished using a H+ ion-supplemented electrolyte. This electrolyte exhibited an excellent VRFB performance, comparable to that of standard V3.5+ electrolytes prepared by the expensive and time-consuming electrolysis of VOSO4 salts. Thus, this study offers a simple strategy for the cost-efficient production of the V3.5+ electrolyte.