I’ve been wondering how safe these things are even when they aren’t ‘chewed’.
What can make them start a fire, like the ones we’ve heard about on airplanes lately?
Puncturing them. I've done it accidentally to a really small (fortunately) lithium-ion cell and it started crackling and sparking a little. Got it outside quickly before it got worse. It burned itself out in a few minutes but an EV cell or a power pack will burn a house or could take a plane down.