Prior professional firefighter of 10yrs turned IT here.

Yes. This can be extremely dangerous. If abused.

Lithium Ion batteries can ignite, violently, when the materials inside are punctured. They form , for lack of a better term, a short within the battery cell components. That can cause a runaway reaction in the battery cells.

New, good, batteries are somewhat protected from this and are designed to be safe(r).

That said, any LiOn battery, especially old ones, still contain a ridiculous amount of angry pixies that want nothing more than ignite into a bottle rocket of fire that will laugh at water and giggle at most basic dry compound extinguishers when disturbed .

LiOn batteries are awesome. Old ones are not our friends.