Abstract Title   Blunt Nail Crush (BNC) Internal Short Circuit Lithium-ion Cell Test Method Abstract Author(s)   Alvin Wu Abstract Presenter   TBD Abstract   A number of reported incidents involving a wide range of small format lithium-ion cells have led to the conclusion that one of the principal safety issues involving the risk of fire is caused by internal short circuits. Many signs point to manufacturing-related defects, but there are still other incidents that result from design characteristics, mechanical abuse or electrical misuse. A test method is needed to simulate failure modes and to determine if cells exhibit a “fail-safe” mode whenever an internal short circuit occurs. Critical behavior and characteristics of the cell failure mode are studied. In a typical case, the internal short circuit failure occurred in a localized area with only single layer or few layers of 18650-type electrodes involved in the energetic electrochemistry reactions. The heat generated from the chemical reactions as well as the thermal energy from internal circuits accumulate quickly and the cell temperature will rise dramatically. Then the cell reaction will escalate to thermal runaway, if the cell is not safely designed to mitigate the effects of an internal short circuit. The “Blunt Nail Crush (BNC)” test has found to be an effective way to simulate the localized internal short-circuit for lithium-ion cells. It was developed and proposed as a viable test method to simulate internal short circuits. A number of cylindrical, prismatic and pouch cells with different chemistries and designs were investigated by this test method. The properties of the test samples and observed failure modes were also analyzed in order to correlate the cell designs and the resulting cell behavior.