Nail penetration is one of the common safety tests used to simulate some aspects of an internal short circuit event in a Li-ion cell. The test is usually performed with an ordinary steel nail, and the only data normally 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.

Dahn and his colleagues developed the “smart nail”—which incorporates a thermocouple inside a steel shaft attached to a copper tip—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.

—Hatchard et al.

Resources

• T.D. Hatchard, S. Trussler, J.R. Dahn (2014) “Building a “smart nail” for penetration tests on Li-ion cells,” Journal of Power Sources, Volume 247, Pages 821-823 doi: 10.1016/j.jpowsour.2013.09.022