Dear
@Urbancowboy
There are 5 basic "ingredients" to any lithium cell: Lithium (may be mixed with other elements such as Cobalt and Oxygen, known as LCO chemistry),
Separator (made from plastic and commonly coated with ceramic),
Electrolyte (Potassium Hydroxide, KOH, is a common one used),
Graphite (used to collect electrons when discharged), &
Aluminum or Steel (used as the case material whether a pouch or hard cylindrical or prismatic shape).
Of the 5 ingredients, at least 1 or sometimes 2 of the ingredients contain oxygen. And at least one or most often 2 are flammable materials. In fire protection engineering the ability to stop a fire requires being able to remove one of 3 things: heat, oxygen, or flammable material. This is known as the fire triangle. When a lithium cell goes into thermal runaway it is generating more heat (usually as a result of a weakness in the separator resulting in positive and negative touching inside the cell, e.g. a short) then it can dissipate and since the fire triangle requires heat, oxygen, and flammable material which inside a lithium cell all of that exists, this is why it's one of the most difficult types of fires to put out. Because even if you put it out temporarily, as soon as the cell has stopped being cooled by water, the short creates heat releasing oxygen and there is still flammable material and so the fire reignites.
There are many strategies to reduce the risk and likelihood of a thermal runaway event and it requires product design starting with the lithium cell being made of high quality and 3rd party certified to safety standard(s). Then the battery pack with its electronics are also to be checked and 3rd party certified to ensure it's doing it's part to electronically protect the cells from being overcharged, overdischarged, shutting down charge or discharge when too hot, and also shutting down when in other abnormal states. Finally the end product itself needs to be checked and 3rd party certified that the way the electricity from the battery pack is being used doesn't adversely affect the safety of the lithium cells and also that the charging (whether built into end product or stand-alone charger) is compatible with the ratings and specifications that match what the lithium cell is specified to be able to handle and has been previous certified for.
Unfortunately in USA there are zero federal consumer safety laws for lithium powered products to only be offered on the market when they have been thoroughly evaluated, tested and certified with ongoing factory surveillance with surprise inspections to reduce risk of fire, electric shock, or explosion. Quite a few countries around the globe like China, Japan, Taiwan, and others do have consumer product safety laws that do required 3rd party safety certification before offering a product to the consumers in these markets.
There has been a bill written at the federal level to allow U.S. Consumer Product Safety Commission to go beyond just providing guidance to manufacturers, importers, retailers, and others about meeting safety standards and being 3rd party certified but it is hard to say what will happen with that. Unfortunately that continues to leave the risk fairly high for most lithium powered products however many older industries like personal grooming, power tools, audio/video, mobile phone, etc. have a fairly regular practice of making their products 3rd party certified. So that is positive however the newer industries that are forming and use larger battery systems like micro- & mini- mobility, consumer robots and drones, etc. have been less likely to make their products 3rd party certified. After New York City passed a law specific to e-bikes and e-scooters last year that started to make these specific types of products safer, but at federal level it's really needs to be there as well.
I've discussed the topic a couple of times on podcasts last year and this year. Happy to send those links if you want further information.
