I've been watching some videos where people show lithium ion batteries burning/exploding. What usually happens is someone punctures the battery, and a jet of gas comes out the puncture hole, followed by the gas catching fire and the entire thing going up in flames.
I often hear that the energy for this reaction comes from the chemical energy stored in the battery. Thing is; i'm pretty sure that there wouldn't be enough chemical energy in the battery to cause such an intense reaction. I'm thinking that it's probably the lithium inside the battery reacting with the air in an exothermic manner.
So what exactly causes the reaction that we see? Does it have anything to do with the electric energy stored in the battery or is it just a lithium/oxygen reaction?
Edit: It was suggested I actually do the math. So here goes; typical energy density of a lithium ion battery would be around 200 watt-hours per kg of battery mass. Therefore a 1kg battery would have about 720 kJ of chemical energy. Proceeding from here we would need to know at the very least a.) the mass of the substance we see being 'exploded', b.) the specific heat capacity of said substance.
For example; if I assume that from a 1kg battery we'd have 300 grams of material being heated up and expelled from the battery, and that said material has a specific heat capacity of 2 kJ/(kg K) , and that said material starts at 293 kelvin, then I'd know that it would take .6 kJ of energy to heat said material up by 1 degree Kelvin. 720 kJ would be enough to heat it up to 1493 Kelvin, assuming 100% of the energy went into heating up just that 300 grams of material and not the other 700 grams. With a specific heat capacity of 3kj/(kg*kelvin) we'd get a temperature of 1013 Kelvin.
I suppose it'd really come down to what the substance we see shooting out of the battery is, and how much is shooting out of the battery, and what it's heat capacity is (and whether it's approximately constant across the temperature range of interest).