Well it certainly wouldn't be superheated steam and it's not like it would be a ton of steam in the grand scheme of things. It takes about 2500 kJ of energy to

Well it certainly wouldn't be superheated steam and it's not like it would be a ton of steam in the grand scheme of things. It takes about 2500 kJ of energy to boil a liter of room temperature water. Someone else mentioned 20 kWh of batteries which in a catastrophic failure I'm assuming the cells might release a little more than that amount of energy but for the sake of argument since I don't know exactly what percent to tack onto that we'll just look at the nominal capacity of the cells. 20 kWh is 72 MJ so that's only enough to boil a bit less than 30 liters of water. Submerging a burning lithium ion pack in something like a bathtub full of water is a great way to absorb all of that energy.