An intelligent nail design for lithium ion battery penetration test

Internal short-circuiting is the most dangerous abuse scenario for lithium ion batteries. A nail penetration test simulates the internal short circuit process by penetrating a test cell/pack with an electrically conductive nail. Pass or failure of the cell and/or chemistry is determined by the presence of smoke or flame following penetration. To understand and eliminate the safety concerns arising from the internal shorts, it is important to fully understand the cell/pack dynamics during the shorting process. Gathering useful data at the point of penetration during nail penetration tests is very challenging due to the inherent destructive nature of the test. This paper presents an intelligent nail (iNail) design consisting of four parts where multiple sensors (thermocouples, strain gauges, etc.) can be conveniently placed for reliable and efficient data collection. The time history of temperature distributions through the cell/pack thickness can be recorded with the iNail without position control of the nail penetration tester, greatly simplifying the test. A prototype stainless steel iNail is manufactured with three embedded thermocouples. Nail penetration tests are conducted on fully charged 4 Ah gr/NCM pouch cells. The iNail successfully recorded the temperature time history at the penetration point during the tests. Pack level nail penetration tests (three pouch cells in parallel) were also performed with iNail temperature measurements.