A two dimensional numerical model of the membrane-divided soluble lead flow battery

Dividing the soluble lead flow battery (SLFB) is known to improve the cycle life of the SLFB by preventing failure mechanisms such as short-circuiting and by allowing electrode specific electrolyte additives. Modelling (SLFB) is a complex multiphysics problem due to the electrolyte flow, composition changes and reaction environment geometry variations associated with the deposition and dissolution of the active material as a function of state of charge. Here we studied the membrane divided SLFB using a two-dimensional, transient, numerical model, built in COMSOL Multiphysics. Divided cells using cationic and anionic ion-exchange membranes and simple, porous separators are compared with the undivided SLFB. The model successfully predicts the complex, non-linear relationship between Pb2+ ion concentration and conductivity of the electrolyte as a function of free acid concentration. There is a deviation of less than 22 mS cm-1 between the simulated electrolyte conductivity and the experimental data. We show the conductivity of the Nafion-115 membrane in the SLFB dominated the potential drop across the membrane. However, at higher current densities, the Donnan potential becomes more dominant