Effects of discharge state on mechanical responses and failure behaviors of lithium-ion batteries under mechanical abuse conditions

To clarify the influence of the discharge state on the dynamic mechanical response and failure mode of lithium-ion batteries, an experimental analysis of the quasi-static compression characteristics and safety performance of lithium-ion batteries under different discharge states was systematically conducted. By presetting the battery to a specific discharge capacity and conducting compression tests at the time nodes of 1 and 24 h after standing during and after the discharge process, the force-displacement response characteristics, maximum load-bearing capacity and safety performance of the battery were thoroughly explored under varying electrochemical states. The experimental results show that, compared with other states, the battery in the discharge state exhibits a lower force-displacement curve, indicating that its stiffness increases after standing compared with that during the discharge process and this decrease is attributed to the electro-chemical reaction inside the battery during the discharge process. In addition, the battery in the discharge state shows a significantly higher maximum load-bearing capacity than that in the standing state after discharge, and the compression test during the discharge process is more likely to cause the battery to explode, while the battery after standing shows a significantly improved safety. The analysis using scanning electron microscope (SEM) further indicates that the damage degree of the internal electrode particles of the battery in the discharge state is more severe. The observed damage and increased risk of mechanical failure are primarily attributed to the diffusion-induced stress generated during the discharge process, which accumulate and intensify the vulnerability of the battery structure under mechanical compression. This study contributes valuable experimental evidence and theoretical insights that are crucial for advancing the understanding of the mechanical integrity and safety of lithium-ion batteries under operational stresses. The findings underscore the importance of considering discharge states in the safety design and evaluation of lithium-ion batteries, potentially leading to enhanced durability and safer application in practical scenarios.