(455c) Multiscale Modeling of Microemulsion Electrolytes for Redox Flow Batteries

Microemulsions have emerged as a promising class of electrolytes for redox flow batteries, offering the unique capability to decouple the electrical conductivity of aqueous salt solutions from the energy density of redox-active molecules confined within the oil phase. These systems are thermodynamically stable, homogeneous mixtures of oil and water, stabilized by surfactants that dictate their structural and dynamic behavior. Therefore, a fundamental understanding of the impact of surfactant molecular architecture on microemulsion behavior is critical for optimizing their performance as electrolytes.

In this study, we investigate the effect of surfactant chemistry on microemulsion organization, focusing on two widely-available nonionic surfactants—polyoxyethylene lauryl ether (Brij-35) and polyethylene glycol sorbitan monolaurate (Tween 20). Using detailed atomistic simulations, we compare the interfacial structural characteristics and dynamics between the aqueous and non-aqueous domains in model biphasic systems. We investigate the effect of co-surfactants and salt commonly added in electrolyte formulations. Subsequently, we assemble simpler, coarse-grained descriptions to address mesoscopic phase behavior and contrast our computational predictions with experimental scattering data, providing key insights into their structural organization.