They can short out without being on charge. There are growth shorts from stable voltage too. They grow little stalactites, that once long enough connect cathode to anode. Once O2 gets involved, it gets ugly from there.

I was head of R+D at a military diver propulsion company (farallon) when about the only devices using lithium batteries were orbital satellites.A french company (saft) provided us with some, at the time, edgy Li batteries. We burned, exploded, and destroyed tons of stuff with them. Good times lol.