Optimization of the Electrochemical Discharge of Spent Li-Ion Batteries from Electric Vehicles for Direct Recycling

Abstract

Numerous studies have been conducted on spent lithium-ion batteries (LIBs) recycled from electric vehicles. Research on pre-processing techniques to safely disassemble spent LIB packs has mainly focused on water-based discharge methods, such as salt-water discharge. However, salt-water discharge corrodes the electrodes and case, causing internal contamination. Therefore, we propose an electrical discharge process that is suitable for the direct recycling and safe disassembly of spent Li-ion batteries. Spent LIBs from electric vehicles (EV) that were scrapped after EV operation were recovered and electrochemically discharged to voltages of 0, 1, 2, and 2.5 V. These discharged spent LIBs were analyzed through X-ray diffraction, scanning electron microscopy, and electrochemical impedance spectroscopy. The spent LIB with a state-of-health (SoH) of 66.8% exhibited significantly increased swelling and bulging when over-discharged. Notably, the discharging of the spent battery to 0 V increased the thickness of the cell by 115%, which could result in a fire and/or explosion. After being discharged to 0 V, the voltage was able to recover to 2.689 V. The appropriate voltage for the discharge process was estimated to be 2.5 V. The proposed electrical discharge process will be suitable for the direct recycling of spent LIBs in the form of pouch cells.