Safety challenges and discharge pretreatment strategies for spent lithium-ion batteries: A critical review

Due to the global energy structure transformation, lithium-ion battery market continues to expand, and a wave of battery retirement is incoming, leading to a continuous increase in the number of spent lithium-ion batteries (LIBs). These discarded batteries are not only highly polluting but also an important secondary resource, making the green processing and recycling of spent LIBs has become a widely concerned issue. In recent years, safety accidents caused by spent LIBs have occurred frequently, resulting in significant property damage and casualties. Due to the variety of failure modes, the complete discharge pre-treatment of waste batteries is an essential condition to ensure the safety of spent LIBs storage, transportation, and processing. This study reviews and summarizes the safety issues caused by spent LIBs recently, and provides a detailed classification and discussion of discharge technologies. It is worth mentioning that the mechanisms involved in the discharge process and the pollutants of spent LIBs that may be generated are finely differentiated and discussed, and the spent battery discharge technology is summarized and outlooked in terms of economy, environment as well as efficiency.