Crushing behaviors and failure of packed batteries

Abstract

The mechanical and failure behaviors of individual 18,650 cylindrical battery have been studied in many papers recently, showing that the internal short-circuit of the battery can be induced by the mechanical load. In practice, the cylindrical batteries mostly work in a packed way and there is little research on the packed batteries. In the present paper, failure behaviors of packed batteries under both quasi-static compression and dynamic collision are investigated by tests. It is shown that the deformation of the packed batteries is very different from those of the individual ones. The failure of the packed batteries is caused by the nonuniform deformation within each battery, which creates vulnerable areas near the gap among batteries. Besides, it is found that the packed batteries under impact collision undergo distinguishing behaviors from those under quasi-static compression. Under quasi-static situations, the packed batteries deform uniformly and the failure batteries distribute randomly. However, under dynamic impact, the packed batteries are crushed row by row with force concentrating at some certain rows, which results in the heavier damage of the batteries under the same crushing displacement, meaning a higher failure risk. Then numerical simulations are employed to deeply investigate the dynamic mechanism of the packed batteries. Four types of failure behaviors are discovered for the packed batteries under dynamic collision, which are related to the stress wave propagation and give a good explanation on the complex dependence of the failure displacement of the packed batteries on the crushing speed. The results indicate that the crushing velocity dominates the failure behavior of the packed batteries rather than the crushing energy. The failure displacement of the battery pack will dramatically decrease once the crushing velocity larger than 20 m/s. More attention should be drawn on the dynamic safety of the packed batteries and the related safety standards also need to consider the complex dynamic collision. All the investigations may provide a basic foundation for the safety protection research of the packed batteries, which are helpful for electric vehicle industry and other structures with packed batteries.