The Effect of Contact Resistance during Nail Penetration of Commercial Automotive Lithium-Ion Cells

Nail penetration is an abuse test that is part of most automotive safety test standards, e.g. the Society of Automotive Engineers’ SAE J2464. The main purpose of nail penetration is to test how batteries can withstand two failure mechanisms; internal short circuits and physical damage such as in the case of road accidents. In this research, nails with varying diameters and materials were used to carry out penetration tests on commercial 15 Ah automotive Lithium-ion pouch cells. The voltage and temperature profiles of the cells during penetration were recorded. The data shows significant variability between tests with the same experimental conditions (nail properties, ambient temperature and cell type). It is proposed that the variability is due to the varying way the nail interacts with the penetrated layers of the cell. Therefore, the contact resistance between the bilayers of the cell and the nail varies between each test. Contact resistance cannot be readily measured in nail penetration tests. In order to understand if the contact resistance is indeed the source of variability, an external short-circuit experiment has been conducted. Different shunt resistors were used to model and represent the contact resistance and this is presented.