Material characterization of Li-ion battery segments subjected to lateral compression and an in-plane tension loads

Abstract

In the last two decades, Lithium-ion (Li-ion) batteries have become an inherent part of day-to-day life thanks to their widespread use in many consumer products and electric vehicles. While these batteries possess great advantages, they also carry an inherent safety liability: In case of a crash event, short-circuit failure of the battery may develop, leading to thermal runaway, fires and even explosions. Hence, a comprehensive study is required, aimed to modulate these batteries and optimize their testing standard. The objective of this research was to characterize the effect of lateral compression on the in-plane tensile failure load of Li-ion battery segments. A new experimental system was developed, which allows fine control of the compression load, and decouples the out-of-plain compression load and the in-plain tension load. Then, measurements were conducted with single-layer, 4-layers and 11-layers specimens, producing characterizing graphs of the tensile load versus displacement. For all types of specimens, results show an observable decrease in the failure load for increasing pre-compression load, as expected. Furthermore, measurements confirmed that the relation between the tensile load and the displacement does not change for different compression loads. For the multi-layer specimens (4 layers), the failure sequence was studied. It was found that the sequence may alter for different pre-compression loads. Nevertheless, on all cases, the cathode failed first, and the anode failed second. Throughout all experiments, failures were located on the edge of the compression area of the specimen. Several methods were used to encourage emergence of failure at the center, but with no success. A hypothesis to explain the development of this mode of failure is suggested at the end of this work.