An effective and cleaner discharge method of spent lithium batteries

Abstract

The rapid development of new energy vehicles has exponentially increased the output of spent lithium-ion batteries (LIBs). The extraction and recovery of valuable metals from spent LIBs are expected to alleviate the shortage of battery materials. However, the spent LIBs to be recycled may still have certain amount of usable output power. If the battery is disassembled and crushed directly, the residual electricity may be hazardous. Therefore, discharge pretreatment should be carried out before disassembling and crushing spent LIBs. To date, electrochemical discharge in conducting solutions has been widely investigated and applied to discharge pretreatment, but there is no convincing evidence of its effectiveness. At the same time, non-electrochemical discharge in conducting powders has been investigated as a possible cleaner and more effective discharge method. Therefore, our current article reports the results of a series of experiments performed with spent LIBs to explore electrochemical discharge in conducting solutions and non-electrochemical discharge in conducting powders. We also systematically discuss the advantages and disadvantages of different discharge media in terms of their discharge efficiency, the potential existence of solid/liquid/gas phase contaminants, and their effectiveness. The experimental results obtained showed that battery discharge reached the safe voltage of 2 V and that the voltage rebound behavior occurs after 48 h standing. This is called the voltage relaxation phenomenon in an electrical field, which could cause certain safety risks during battery disassembly and crushing. Therefore, the effect of voltage rebound was also studied, and the obtained results showed that the voltage was over-discharged after flake-graphite discharge, which would cause irreversible damage to the anode material of the batteries and lead to battery failure. This is of great significance for the discharge pretreatment of spent LIBs. Therefore, flake-graphite discharge is an cleaner and effective discharge method for spent LIBs.