As the energy transition continues, interest in and demand for lithium-ion batteries has significantly increased. Global sales of electric vehicles have experienced substantial growth in recent years. Recycling of these batteries is vital, not only from an economic standpoint, as it reduces production costs and addresses resource scarcity concerns, but also because recycling contributes to the reduction of greenhouse gas emissions, conserves energy, and minimizes waste. Recycling has also been enshrined in law, as both recycling and a minimum percentage of recycled material will be mandatory from 2027. However, the recycling process may introduce impurities that can potentially affect the performance of lithium-ion batteries.

Oxalic acid serves as a leaching agent in some recycling processes. Therefore, this research seeks to understand the impact on battery performance of various metal oxalates, expected to be formed during recycling and are subsequently to be introduced into batterys made from recycled material. To assess this, small-format battery cells are intentionally contaminated with metal oxalates and subjected to testing at their end of line. The aging behavior is examined through cyclic and calendrical aging tests, with evaluations based on measurements of internal resistance and state of health. The Li-ion-batteries’ performance is dependent on the oxalate introduced cation. Our method gives the opportunity to distinguish between cyclic and calendar aging.