Batteries, especially redox flow batteries (RFBs) play a major role in our future energy system to decarbonize our society as they provide back-up storage capacity for regenerative energy sources. Basically, the two core components of a flow battery comprise the electrochemically active electrolytes and a proton-conductive membrane. Currently used commercial systems for both components rely on materials which are not- renewable, non- sustainable, potentially toxic and which accumulate in the environment. Furthermore, both components (e.g. Vanadium, NafionTM) are expensive, which negatively impact the cost per installed kWh and represents a barrier for a further use of the technology in other applications. As there are constantly new and interesting develeopments in the field of sustainable electrolytes (e.g., vanillin-based systems), research on sustainable membranes in RFB technology is still in its infancy.
In the FFG funded IonFlow project, TU Graz and proionic explore a novel type of RFB membrane technology, which is scalable, based on sustainable renewable resources and which fulfills all requirements of an RFB membrane (e.g., ion conductivity and selectivity, prevention of cross-diffusion through membrane). The core element is the use of renewable substrates which are treated with tailor made ionic liquids provided by proionic to give stable and high performing membrane materials. The process which is currently under patenting, can be easily scaled up and does not use any organic solvents. We estimate that the use of this type of membranes will lead to a cost reduction by a factor of 5 to 10 compared to currently used NafionTM membranes, with a much better ecological footprint. In addition, the know-how of proionic on tailoring ionic liquids enables a steady further development of the technology, finally broadening the expertise as well as approaching new emerging markets in battery technology and fuel cell technology.