Commercialization and deployment of redox flow batteries is limited by the low Energy density of these devices compared to the Energy density of conventional batteries, i.e. without electrolyte recirculation, particularly Li-ion batteries.
In the last years, different strategies to increase the Energy density of redox flow batteries have been investigated. For instance, by increasing the concentration of active species dissolved, by using molecules able to exchange multiple electrons, by substituting liquid electrolytes by stable suspensions of active materials from Li-ion batteries. Unfortunately, none of them has reached satisfactory results so far.
The Electrochemical Processes Unit has investigated a new concept to increase the energy density of certain flow battery electrolytes. It consists of a hybrid design combining a flow battery and active materials from conventional batteries. The solid active material is confined within the electrolyte tank and the electrolyte is tailored to behave as redox mediator between the active material and the battery electrodes, acting like a “chemical wire”. In this way, we have demonstrated a 5-fold increase over the theoretical energy of the electrolyte alone.
This novel concept has been protected in a European patent application (EP18382971) later extended to an international patent (PCT/EP2019/086203) and is available to any organization interested in its commercial exploitation.