Design and Implementation of Deep Discharge Control in Lithium-ion Batteries Recycling

The growing demand for energy storage has made lithium-ion batteries (LIBs) vital to many areas of modern technology. With increasing deployment of LIBs in recent years comes increasing volumes of spent units, and efficient recycling is essential to recover critical materials like cobalt (Co) and lithium (Li) for re-use, while minimizing environmental harm. For heterogeneous LIB units - with capacities ranging from, e.g., 20 to 100 kWh and with voltages between 300 and 800 V - significant residual storage capacity can be present at the point of recycling (80% in some cases), posing significant safety risks. Residual charge in batteries during recycling operations can cause thermal runaway, fires, or explosions, mandating a pre-emptive deep discharge process. However, varying chemistries complicate this, as each demands specific methods, making standardization a major challenge. In addition, internal degradation and external wear-and-tear of electrical components and mechanical assemblies provide difficult to detect complicating factors. This paper introduces a robust control algorithm for the deep discharge of LIBs in recycling applications. The algorithm dynamically adapts discharge parameters based on real-time state-of-charge (SoC) estimation, internal resistance monitoring, and thermal profiling, ensuring a safe and efficient energy depletion process. The developed control strategy has been successfully implemented and validated, demonstrating reliable operation across different battery conditions. It effectively mitigates safety risks, prevents thermal runaway, and improves overall process efficiency. The proposed approach enhances the automation and reliability of LIB recycling operations, contributing to safer and more sustainable energy storage management.