Challenges related to extending lifetime of EV batteries – 21.6.2023

As part of the TREASoURcE project, used batteries from electric vehicles (EVs) are reused as stationary energy storage in buildings with solar panels on the roof. Through implementing energy storage as part of the system, the electricity produced from the solar panels can be utilized more efficiently. Additionally, the batteries can serve as grid support and stabilise the local electricity grid.

It is, however, not so straightforward to reuse batteries from EVs. There are a number of challenges that arise, which pose both technical and economical barriers for giving batteries a second life in a new application.

SINTEF together with ECO STOR and VTT have gathered information through interviews, extensive literature search and a review of current legislation and regulations. Through this work, four different main categories were identified as particularly important: technical barriers, regulation & legislation, eco-design, and safety & reliability. Some of the main conclusions from the work can be summarized according to these categories.

Regulations & legislations
There is currently a lack of regulatory environment, testing and safety standards for repurposing EV batteries. This often leads to confusion with regards to what is safe and how batteries should be handled, resulting in many stakeholders being reluctant to implementing batteries. The upcoming EU Battery Directive will provide some guidance. However, this new directive has much more focus on the recycling of batteries than extending lifetime. This may cause industry to favor battery recycling at the expense of extending the lifetime.

Technical challenges
Li-ion batteries (LIBs) that are used in EVs have developed very quickly in the past decade, and continue to change, thus leading to a host of different electrode materials, form factors and battery pack designs. A lack of standardization makes it difficult to streamline disassembly and reuse of batteries, which also increases the cost significantly. In order for EV batteries to be reused, it is also vital to know their state of health (SoH). This depends on how batteries are used, where they have been used and so on. Historical user data is not readily accessible to anyone but the EV manufacturers. Expensive testing procedures are therefore required to establish the battery’s SoH before it can be used for further applications.

EV batteries are designed for low cost and low weight and are built to fit the specific EV. Often glue, welding and other means for fastening are used to keep the batteries in place, making them difficult to remove and disassemble. As a result, the process of reusing becomes both time-consuming and expensive.

Safety & reliability
LIBs are inherently very safe. However, due to the negative publicity around battery fires and the difficulty in extinguishing the fires, the public opinion of EV battery repurposing for energy storage is often very negative. This makes it more challenging to promote used EV batteries for stationary energy storage. Reliability of the batteries is also a concern. Although the batteries are thoroughly tested before implemented in a second life system, the chance of sudden capacity loss is always greater in a used battery. Thus, the second life batteries may appear less reliable compared to new LIBs.

Although many challenges appear in the battery second life market, there are still a number of new stakeholders utilizing this opportunity. Also, the new EU Battery Directive which is expected to be approved by the European Commission this year, will to a great extent mitigate several of the challenges pinpointed here (although it comes with some challenges, as mentioned above). And with more research and knowledge on second life battery systems, including the results from TREASoURcE, the public acceptance will hopefully increase, and implementation will accelerate with the growing need for energy storage.

20.06.2023 | Fride Vullum-Bruer (SINTEF),

A full version of the D4.1 Report on existing and upcoming challenges for 2nd life battery use will be published later on our website.