TOTAL teardown of a lithium phone battery.

Primary, non-rechargeable lithium batteries typically contain metal lithium [0], and are actually more likely to catch fire when mishandled, compared to Li-ion stuff. Specifically, most common Li-ion fires start when overcharged (especially with high current and in cold), and from short-circuits (e.g. when pierced). But only have a very small chance of spontaneously igniting from just disassembly alone [1]. Still non-zero chance, don't open them! Primary/metal lithium batteries, on the other hand, are much more likely to burst into flames when opened. Notably, lithium-iron disulfide (AA/AAA "alkaline replacement") cells are notorious to do that just from air exposure, even if one is very careful to not short/pierce anything. [0] link [1] ▶ this video

EgyptAir is investigating if a phone or tablet may have led to a crash of one of their jets: link There have been many devices that have come under scrutiny for their Li-Ion cells. At least few devices explode, and I'm not aware of any killing people, but many have had these meltdowns. Big Clive successfully took one apart without it going boomb if anyone is interested in what's inside of them: ▶ this video

Big Clive does a really amazing (and dangerous) tear down of what's inside a Lithium Ion cell, in case anyone wants to see what the parts in the diagram physically look like: ▶ this video

> The thinner the battery, the closer the positive and negative terminals are. Absolutely false. All lithium ion batteries are made of 4 paper thin layers: two electrodes and two separators. These are cut in narrow strips and folded on themselves many times over, even in a thin battery. A thinner battery will simply have fewer folds. The distance between the two electrodes is given by the thickness of the separators and it has nothing to do with the thickness of the cell. Here's a teardown: ▶ this video (possibly NSFW-ish language).