Elucidating effects of component materials and flow fields on Sn–Fe hybrid flow battery performance

Component materials and flow fields are key design parameters that influence the advection-diffusion-reaction process and thereby the performance of a Sn–Fe hybrid flow battery . In this work, various electrode configurations (empty chamber and porous carbon-based electrodes), membranes (cation and anion conducting) and flow fields (serpentine and interdigitated) are systematically investigated to elucidate their effects on the unique charge/discharge behaviors of the Sn–Fe flow battery with tin metal plating/striping. It is found that the battery capacity roughly increases linearly with the porosity of the porous electrode especially at low current densities , and a highly porous electrode (graphite felt) is more desirable than an empty chamber configuration in terms of capacity and power density. In addition, as compared to cation exchange membrane (Nafion 212), the anion exchange membrane (Fumasep FAP-450) exhibits improved capacities and columbic efficiencies in sulfuric acid-based electrolytes at low current densities due to the reduction of cation crossover. Interestingly, it is showed that although a serpentine flow field and a low flow rate generally lead to poor battery performance, they tend to ameliorate the maldistribution of plated tin at the negative electrode owing to the restricted mass transfer of reactants.