Read this: https://batteryuniversity.com/learn/article/safety_concerns_with_li_ion

Nowadays, the only cells with metallic lithium inside are primaries, such as the Energiser AAs, CR123s etc, and if you try taking one apart you may quickly learn what a metal fire is like, and no, water only makes it worse. It is pretty close to sodium and potassium in reactivity, if you remember chemistry demonstrations. Fun though.

LiIon are quite different, and not so scary. Nevertheless I wouldn’t want to be travelling in a ’plane with a few tonnes of them in the cargo hold.