TU Graz – A second life for batteries.
Discarded lithium-ion cells from electric cars could be reused as stationary power storage devices. Researchers at Graz University of Technology have identified the first indicators for reliable condition assessment.
In 2030, around 1.2 million batteries in electrically powered cars, buses and construction machinery will be retired worldwide because they are reaching the end of their planned service life, their warranty is expiring or because the vehicles are being scrapped. There will be around 14 million old batteries by 2040. Recycling the materials makes sense, but it is also expensive and technically demanding . Therefore, continued use of the batteries, for example as stationary electricity storage, would be better and more sustainable. This requires a well-founded assessment of the remaining performance and security. At Graz University of Technology, researchers from the Institute for Vehicle Safety have now determined the first parameters that can be used to reliably assess the condition of discarded batteries.
13 indicators characterize the aging process
To date, the reduced charging capacity and the increase in internal resistance have served as an indication of the condition of a used battery. However, this is not sufficient to make a decision about possible second-life use. The researchers therefore carefully examined lithium-ion cells that were used in vehicles under real conditions and identical, new examples in the laboratory: They recorded 31 different measured values during reproducible charging and discharging cycles and then checked how well they performed Represent the aging condition of the batteries. 13 of these indicators turned out to be meaningful – these include, for example, the charging and discharging capacity, the temperature difference between the poles during the charging process or the relaxation behavior of the battery cell after charging.
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Jörg Moser, head of the Battery Safety Center Graz from the Institute for Vehicle Safety at Graz University of Technology, said:
Using these indicators, we can draw conclusions about the aging status of lithium-ion batteries and draw initial conclusions about different usage profiles without having to rely on data protection-critical information about the usage history of the batteries.
“On this basis, we can decide whether a battery is in principle suitable for continued use in a specific area of application.”
Security assessment as the next step
However, the safety status of the batteries is still missing to ensure low-risk continued use. During their first life, chemical changes occur in the materials, which can affect their safe use.
Christian Ellersdorfer, said:
It is crucial to understand battery cells and the processes, reactions and changes that occur in them in detail in order to be able to qualify them with regard to their safety behavior.
He leads the COMET project SafeLIB at the Institute for Vehicle Safety, in which a consortium of research institutions and automotive and technology companies works on the safety-relevant assessment of new and used lithium-ion batteries. The first results are expected by the end of the year.
It will probably be a few years before used batteries are used on a broad basis in subsequent applications and electromobility becomes even more sustainable over the entire life cycle. New storage materials, the safety of different battery technologies, the economic viability of second-life applications and legal questions about data protection, warranty or liability must also be taken into account.
Christian Ellersdorfer, said:
“This results in an interdisciplinary research field that we at TU Graz want to work on together with national and international partners in further research projects.”
This research project is anchored in the Field of Expertise “ Advanced Materials Science ” , one of five strategic focus areas at TU Graz.
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