Untrue. I use them for 10+ years for anything that’s possible (flashlights, powerbank and anything you can power with it) and they’re not dangerous if you follow SIMPLE rules. About as dangerous as a bottle of vinegar. And you can perfectly buy good cells for any application, Sony vtc5 or vtc6 are two examples, never buy cheap ones and NEVER buy from shady sellers. And btw: you shouldn’t put any battery to your keys in your pocket, that is called “stooo-pid” and makes little black holes in your thighs.