Electrification is occurring in large sectors across the world, from electric vehicles to grid energy storage. As a result, battery safety is of paramount concern with electric vehicle fires quickly finding their way to media outlets worldwide. This is especially true when battery fires occur near a home or structure. For this reason, advanced warning of an off normal event is crucial for mitigation or intervention. That is, advanced warning so that we may potentially stop the occurrence of thermal runaway, and thus a battery fire, and/or advanced warning to allow movement of individuals away from a dangerous situation.

This work utilized rapid electrochemical impedance spectroscopy (EIS) and a commercial gas sensing tool to quantify key metrics in early detection of off normal events for battery cells in the pouch format. The time between detection of an off normal event, via EIS response or gas detection, and thermal runaway was determined in a controlled environment, under abusive conditions. The importance of gas sensor proximity to the time between detection and thermal runaway was evaluated. This testing used an array of sensors positioned throughout an abuse testing bay, along with in-operando rapid EIS. Batteries with LFP or NMC cathodes were subjected to two abuse modes, overtemperature and overcharge. The gas composition was verified by FTIR to rule out the possibility of a false positive by some other substance, aside from vented gases, such as adhesive heating. This work gives insight into the ability of EIS and gas sensing to give advanced warning with different battery chemistries and failure modes.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.