PNNL

Abstract

Operational stability of electrolytes is a persistent impediment in building redox flow battery technology. Stabilizing multiple vanadium oxidation states in aqueous solution is a primary challenge in designing reliable large-scale vanadium redox flow battery (VRB). We demonstrated that rationally selected ionic additives can stabilize the aqua vanadium solvate structures through preferential bonding and molecular interactions despite their relatively lower concentrations (=0.1M). The competing cations (NH 4 + and Mg 2+ ) and bonding anions (SO 4 2- , PO 4 3- and Cl - ) introduced by biadditives are used to tune the vanadium solvation chemistry and thereby design an optimal electrolyte for VRB technology. Such a molecular engineering of VRB electrolytes resulted in enhancement of the operational temperature window by 180% and energy density by over 30% relative to traditional electrolytes. This work demonstrates that tunable solvation chemistry is a promising pathway to engineer an optimal electrolyte for targeted electrochemical systems