Recently our electric vehicle testing sister brand CamMotive did some testing on thermal runaway in lithium ion batteries. They induced thermal runaway in a single LiPo pouch cell (which are combined to make a lithium ion battery) by electrically "backdriving" it until it overheated and eventually caught fire. We measured the gas and particle emissions using Cambustion fast response analysers (FID50 for hydrocarbons, NDIR50 for CO and CO₂, DMS500 for nanoparticles, including the real-time size distribution from 5 - 1000 nm), as well as instrumenting the cell for temperature. The video below shows the results.
Well before the cell actually catches fire, hydrocarbons and small "nucleation mode" particles are seen — these could be symptomatic of volatile compounds being driven off by the rising temperature. As soon as combustion begins, large amounts of CO, CO₂, hydrocarbons and much larger sized particles are emitted. Cambustion fast-response analysers uniquely allow capture of these rapid events as they happen and the complex processes at work evolve.