Predicting Viscosity of Electrolytes for Redox Flow Batteries

Redox flow batteries represent an evolving technology with significant potential for large-scale energy storage solutions. Despite their advantages, achieving higher energy densities through increased active-material concentrations has led to increased electrolyte viscosities, impeding their practical applications. We conducted combined experimental and comprehensive atomistic molecular dynamics simulations to understand the viscosity changes at a molecular level. Our study focused on both the oxidized and reduced states of the highly stable vanadium bis-hydroxyiminodiacetate complex, involving a variety of alkylammonium cations at different temperatures. The simulations closely match experimental viscosities for concentrations up to 0.5 M, revealing critical insights into solvation dynamics, ion-pairing, and fundamental chemical interactions. These insights would enable the tailored development of electrolyte blends with improved transport properties.