Fraunhofer UMSICHT spin-off Volterion has developed a new class of redox flow batteries that costs the same as li-ion batteries, but lasts almost twice as long as them.
Redox flow batteries have been touted as the future of renewable energy. They not only offer superior cycle durability but are also non-flammable, recyclable and easily modified for both capacity and performance.
There is however one major factor holding back their wide-scale adoption – the prohibitively high costs associated with producing them.
Fraunhofer spin-off Volterion has now come up with a solution it believes could make redox flow batteries as ubiquitous as li-ion batteries both in terms of cost and efficiency.
Redox flow batteries consist of stacks, which in turn consist of electrochemical cells to convert the electrical energy into chemical energy, and electrolyte fluid tanks to store that chemical energy. This stack structure is the main reason why redox flow batteries are so expensive.
Dr. Thorsten Seipp, managing director at Volterion and former research scientist at Fraunhofer, explains that they have managed to reduce the cell weight to ten percent of the stack, and this has in turn brought down costs.
“Whereas, in conventional stacks, the thickness of each cell was often as high as eight to ten millimeters, we’ve succeeded in cutting that down to two to three millimeters,” notes Seipp.
The breakthrough was achieved by improving the battery material. Stacks are generally made out of a graphite-polymer composite. During processing, however, such materials lose their polymer properties.
Moreover, inter-cell connections cannot be welded; instead cells must be joined using threaded sealing rings.
“What we did at Fraunhofer UMSICHT was to modify the material and the manufacturing process in such a way that the material retains its polymer properties,” explains Seipp.
“As a result, the material remains stable and flexible and can be made significantly thinner, allowing the stacks to be welded together, and doing away completely with fast-wearing sealing rings.” explains Seipp.
According to the scientists, this not only makes the production of the stacks much more cost-effective, but also more robust than ever.
Image and content: Fraunhofer UMSICHT