Overdischarge process of lithium-ion batteries for the recovery of low-damaged cathodes

An overdischarge process as a step of battery recycling was investigated using a spent battery. The procedure aims to obtain clean materials while ensuring safety during the disassembly of battery cells. Two overdischarge methods were compared. One method (Method A) overdischarged the DOD to 120 %, reaching −0.431 V. The other method (Method B) was to overdischarged the DOD to 0 V and then maintain the voltage for a day. The cleanness and the structure of the cathodes were analyzed by photographs, SEM, BET, ICP, XPS, and XRD. Sample 1 (S1), overdischarged by the Method A, was contaminated by Cu. In contrast, Sample 2 (S2), overdischarged by the Method B, was contaminant-free. A relatively ordered structure was also confirmed. Method B was implemented using 10-cells connected in series. As soon as the module began to discharge, the voltage of all cells was simultaneously reduced. While the module voltage was held at 0 V, the maximum and minimum cell voltages were 0.064 and 0.033 V, respectively, indicating cell balancing was maintained. Therefore, Method B provides a simple overdischarge process for a battery module or pack without a high-specification discharger.