This question already has an answer here:
The wife’s laptop is an older Macbook with a dead battery (i.e. it wouldn’t charge, but used to run fine when connected to an outlet). With the wife in hospital the thing wasn’t used for a while now (and not connected to power). Today I noticed that the bottom plate was deformed. When I removed it I saw that the battery was bulging. While I was watching the battery case cracked open (either because the bulging was still in progress or because the pressure from the backplate was removed). I live in a fourth floor apartment without emergency exits, so I am a bit more than usual concerned about fire hazards. Also I'm clueless about electricity, thus I called the local fire brigade for advice. They recommended that I should throw the battery into a bucket of water to cool it down.
So my first question is, is this the proper thing to do? The internet is in two minds about this, one half saying NOOOO! because lithium (which is what I would have thought) and the other half saying there is no metallic lithium in a lithium ion battery, so that’s not a problem.
In the end I did not do it, amongst other things because there is still a computer attached to the battery - despite using the proper screwdriver the screwheads had sheared off when I had tried to remove it. At the moment the whole thing is sitting in a ceramic pot, wrapped in a watertight bag, in the middle of the back yard, which has a concrete floor.
So my real question is, how dangerous is a depleted lithium-ion battery (I have no idea if the danger depends in any way on the electric charge)? In the unlikely event that the thing will not be stolen overnight I want to remove the battery and salvage the rest of the computer. The only way to get it out will be to break off the latches for the screws, which means I have to hack away a few millimeters away from the bulging battery cells. Is that even remotely safe ? Do I need protection (I should have plastic goggles and gloves lying somewhere)? Or do I worry unduly, and this im completely harmless?
There is a rather similar question, but since I specifically need to break the case of an already damaged (and cracked open) battery this does not quite help (
also I’m really curious about the „cool batteries in water“ thing found an answer to that). Also I hope somebody can recommend sensible precautions.