Studies on Fe/Fe Redox Flow Batteries with Recombination Cell

Different Fe/Fe redox flow batteries were constructed and investigated. The aim of the work was to assess the feasibility of Fe/Fe redox flow batteries as potentially inexpensive candidates for stationary energy storage for renewable energy. A recombination cell was developed and integrated into the battery. The recombination cell should prevent irreversible loss of capacity caused by hydrogen generation. Furthermore, electrolyte regeneration experiments with external hydrogen were conducted to reverse irreversible losses. With the battery and recombination cell up to 100 two-hour charge and discharge cycles were carried out and different materials were investigated. Different substrate materials for iron deposition were compared and different microporous and ion exchange membranes were used. A kynol fabric achieved the best performance and all membranes investigated showed potential applications. An optimized battery achieved up to 70% energy efficiency at 12.5 mA cm−2 and max. 47 mW cm−2 power density at 75 mA cm−2.