Impact of electrolyte composition on the mitigation of electrolyte imbalance in a vanadium redox flow battery: A 3D multiphysics model

In this work an all-vanadium redox flow battery 3D model is developed to study the crossover phenomena causing electrolyte imbalance in an perpendicularly assembled battery. Fluid flow is fully modeled including transition from porous media to non-porous zones coupling the Navier–Stokes equations with the Brinkman corrections. General conservation laws are applied to model the electrochemistry in the electrolyte and electrochemical equilibrium is used to model Donnan effect at the membrane-electrolyte interface. Exclusion of the co-ions in the membrane is carefully modeled leading to a novel treatment of the sulfuric acid dissociated species in this domain. The impact of different proton and vanadium concentrations in the battery half-cells is studied in detail showing a potential way to reduce electrolyte imbalance. • The impact of different proton and vanadium concentration in a VRFB half-cells is studied in detail showing a potential way to reduce electrolyte imbalance. • The full 3D model of the VRFB includes all forms of crossover phenomena (diffusion, migration and convection). • A new treatment of the sulfuric acid dissociated species is presented in order to effectively exclude sulfate ions in the membrane domain in a VRFB. • Accumulation of vanadium in the positive half-cell in a VRFB can be reduced by the readjustment of asymmetrical electrolyte concentration, which comes with a trade off between battery capacity and energy efficiency/power density.