Material characterization of lithium ion batteries for crash safety

Abstract

The safety of lithium-ion batteries is extremely important due to their widespread use in consumer products such as laptops and cell phones. Several cases of thermal runaway in lithium ion batteries that resulted in fires have been reported recently. And in the case of vehicle batteries, deformation during a crash event could cause an internal short circuit, leading to thermal runaway, fires, or toxic gas release. While much is understood about lithium-ion batteries, no comprehensive computational models exist to test and optimize these batteries before manufacture. The objective of this research was to characterize the mechanical properties of three types of lithium-ion batteries through cell and interior component mechanical testing. Prismatic, elliptic, and pouch cells were tested using hemispherical punches to obtain load-displacement curves. Elliptic and pouch cells were also compression tested. Uniaxial, biaxial, and compression tests were performed on the interior components of elliptic and pouch cells. The test results were then used by Impact and Crashworthiness Laboratory team members to create, validate, and refine computational models. This research resulted in many conclusions involving the lithium-ion cells, their interior components, and efforts to model the failure of cells. At the cell level, the effect of liquid presence, strain rate, separator type, and test location was studied. The level of experience in sample preparation and testing methods was an important result for interior component material characterization, as was the varied force-displacement results for different cell types. But most importantly, this work demonstrated that the material characterization of lithium-ion battery cells through mechanical testing could be used to create, calibrate, and validate cell numerical simulation models.