Insights Into Electrolyte Effects on Interfacial Kinetics and Transport in Porous Redox Flow Battery Electrodes: A Multiparadigm Modeling Study

Redox flow batteries (RFBs) have emerged as promising candidates for large-scale energy storage owing to their decoupled energy and power densities. Electrolyte formulation plays a key role in determining the electrochemical performance of RFBs, influencing interfacial kinetics and transport within porous electrodes. Herein, we develop a multiscale modelling framework to investigate the coupled effects of the electrolyte concentration (Methyl Viologen (MV) and NaCl) and the fibrous 3D microstructure on the porous transport and electrochemical kinetics in organic RFBs using a kinetic Monte Carlo model. We link this interfacial kinetics to the advection-diffusion transport in stochastically generated carbon felt electrode microstructures through Lattice Boltzmann Method simulations via an interpolation-based coupling. We use two performance descriptors, the fibre-averaged rate of potential loss and convective area fraction, to quantify the kinetics and transport effects, along with their interplay. While increasing MV concentration enhances the interfacial kinetics, it limits the transport within the electrode microstructure. The interfacial kinetics shows to be nontrivially governed by the supporting electrolyte. A surface area-permeability trade-off appears across microstructures with different electrolyte concentrations. This multiparadigm modelling workflow provides mechanistic insights between porous transport and interfacial electrochemical kinetics, enabling the coupled optimization of microstructures and electrolytes in RFBs.