Recycling A Second Life for Used Lithium-Ion Batteries?

Related Vendors

Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF

FAULHABER Drive Systems

Wuxi InfiMotion Technology Co., Ltd.

What happens to old, used lithium-ion batteries? This question was addressed by researchers at Fraunhofer LBF in the Circulus project: they converted used traction batteries into a stationary storage system and developed a recyclable lightweight battery case

Lithium-ion batteries from electric vehicles lose their charging capacity over the course of their use. From a capacity loss of 20 percent, they are no longer suitable for vehicle operation, as the range and fast charging ability decrease. However, the remaining 80 percent capacity could be sufficient for a stationary storage application. From the perspective of the cells, which are expensive to purchase new and thus make the economic viability of the stationary storage difficult, this is a very sustainable approach. However, from a system perspective, this approach presents a challenge.

It is fundamentally important to consider three key points when reusing lithium-ion cells or lithium-ion battery systems:

• Lithium-ion cell is not equal to lithium-ion cell, because the cells differ significantly in their aging behavior depending on the composition of the electrolyte used, the material used for anode and cathode, and the physical structure of the cell. This means that for each use or second use, the aging behavior of the cells installed must be tested and evaluated. The existing cell state indicates whether the cell can still be operated economically and safely in further use.

• Evaluating ongoing safety in the aged state involves monitoring and regulation during secondary use in stationary storage. It is necessary to appropriately adjust the battery management. This is also the second key point that needs to be taken into account in secondary usage.

• The third focus is on the design and construction of the battery system as a whole. The current state of the art does not consider the possibility of second use. This leads to high temporal and economic efforts, for example through necessary renovation measures, up to complete exclusion for second use. The design and structure of the battery system itself also play a, if not the decisive, role in the subsequent and necessary recycling of lithium-ion battery systems.

Lightweight and recyclable battery housings for electric mobility

In the Circulus project, scientists at the Fraunhofer Institute for Structural Durability and System Reliability LBF are developing a battery system that is directly designed for a first and second usage phase. A major focus of work are reversible and yet light and operationally safe joining connections at the cell level, over the module attachment, to the system housing. Additional tasks concern a practical method for cell assessment and the realization of efficient and fast conversion concepts from mobile to stationary applications.

Gallery

Additionally, they are developing as light and recyclable battery housings as possible, made from materials such as plastics for e-mobility. For a successful circular economy of structural components, easy and material-flow-appropriate dismantling is essential in order to make sorting as efficient as possible. The extracted material flows should be used as efficiently as possible and processed into high-quality recyclates. Through comprehensive analytics, researchers at the Fraunhofer LBF can capture the quality and possible batch differences of the materials. This serves as a starting point for targeted material adjustment in the context of R-strategies for use in demanding and highly stressed applications. Quality improvement can be achieved along the entire value chain through adapted additive.

"Thus, we achieve a circular use of the materials used and enable, among other things, a sustainable use of resource-intensive battery cells," says Eva-Maria Stelter, scientist at Fraunhofer LBF and project leader of Circulus.

Sustainable development thanks to interdisciplinary approach

The use of already used battery cells from former traction storage systems in 2nd-life applications is a complex transformation process. "To manage this, a transdisciplinary approach is needed to discuss the relevant challenges and questions in their complexity. The various perspectives of different scientific disciplines regarding economic, ecological and social aspects must be taken into account," explains Dr. rer. sust. Dominik Spancken, the first doctor of sustainability sciences in Germany.