Thermal Safety and Electrochemical Responses of LFP, NCM, and SIB Batteries during Low-Temperature Recycling Crushing

With the rapid expansion of electric vehicles and electrochemical energy storage systems, retired batteries are entering a phase of large-scale recycling. Developing efficient and environmentally friendly recycling processes urgently requires a clear understanding of the electrochemical instability and thermal diffusion behaviour of different battery chemistries under low-temperature pretreatment conditions. In this study, the open-circuit voltage (OCV) evolution, mechanical failure behaviour under compression, and post-failure thermal diffusion characteristics of lithium iron phosphate (LFP), nickel cobalt manganese (NCM), and sodium-ion batteries (SIB) are systematically investigated at 0 °C, -10 °C, and -20 °C under varying states of charge (SOC). The results show that the displacement range over which OCV evolves from stability to fluctuation and eventual collapse depends strongly on SOC, revealing a coupling between stored energy and structural integrity. At 50% SOC, LFP and NCM batteries exhibit greater ductility and delayed load-bearing limits, whereas SIB batteries display pronounced brittle instability, characterized by severe post-peak load fluctuations associated with staged fragmentation, which are further intensified at high SOC. Thermal analysis indicates that decreasing temperature significantly lowers peak failure temperatures. Under identical conditions, NCM batteries exhibit higher peak temperatures and recurrent minor explosion-like sound, indicating elevated thermal risks during crushing operations. In contrast, SIB batteries show relatively stable thermal responses with low temperature sensitivity. These findings provide quantitative guidance for low-temperature pretreatment strategies, crushing process optimization, and safety window definition in end-of-life battery recycling.