When I played with such a battery a while back, it didn’t generate much excitement. I peeled off the covering, to get past the battery’s charge controller (little processor chip that controls current flow), and shorted the terminals together. Turns out that battery had another layer of safety, a strip of some funny kind of metal that became non-conductive when it warmed up a little bit. Nothing exciting happened at all. It barely got warm. Of course, you could take a knife to the cell itself. That might be exciting.
You can get more excitement from a couple of 9v electronics batteries, though. When you change the ones in your smoke detector, try plugging a couple of them together, mating the snaps. When I did this, they got hot so quickly that I didn’t have time to unplug them. They’d probably get hotter if you use new batteries, maybe hot enough to start a fire.
