Building a “smart nail” for penetration tests on Li-ion cells

Abstract

Nail penetration is one safety test that Li-ion cells experience in order to simulate some aspects of an internal short circuit event. To our knowledge, nail penetration is usually performed with an ordinary steel nail. Normally, the only data gathered has been a simple pass/fail result depending on whether or not the cell emitted smoke or flame, along with a thermocouple on the surface of the cell. A “smart nail” has been developed to allow the collection of temperature versus time data at the point of nail penetration. This nail, in conjunction with a thermocouple on the cell surface and tabs on the ends to measure voltage, should provide some new insights into the behavior of cells during this type of abuse testing as well as aid in the developing of safer Li-ion cell chemistries.