Investigating the Electro-Kinetics and Long-Term Solubility of Vanadium Electrolyte in the Presence of Inorganic Additives

Abstract

With the ever-growing energy storage demands for electrical grids, vanadium redox flow batteries (VRFB), a stellar candidate, need continuous cost, cyclability, and energy density improvement. The VRFB tend to lose vanadium from electrolyte solutions due to the precipitation of V2O5 during charging, resulting in a significant loss of energy density. We monitored the solubility and electrochemical characteristics of vanadium electrolyte solutions with V2O5 as the starting material in the presence of different additives, namely HCl and MSA (methanesulfonic acid), for over three months. On average, the ionic conductivity of solutions with additives was 50 mS higher than that of without additives. Additives also improved the electrochemical performance and lowered charge transfer resistance. UV/Vis and Raman spectroscopy were utilized, and a reaction mechanism responsible for improved conductivity and kinetics was proposed.

Effect of phosphoric acid additive on the electrolyte of all-vanadium flow batteries

“…, are rich in –OH, O, –NH 2 , or –SH functional groups, which can be used as vanadium-ion stabilizers. 9,15–17 However, most organic compounds can be slowly oxidized in strongly oxidizing pentavalent vanadium solutions. Inorganic additives mainly include amino compounds, phosphoric acid and its salts, polyphosphates, etc.…”