As a former chemistry student I just wanted to quickly add to the discussion:
my understanding of the battery-related (lithium-ion, specifically) explosions is that it stems from the electrolyte liquid used in the battery.
These electrolytes are flammable! I can't recall the specific reason that these solutions are flammable but I do recall it being true for most (if not all) li-ion batteries.
At any rate, as you can see, there is an inherent risk with *any* li-ion battery.
Careful here, flammables start fires (like with the Galaxy cell phones) not explosions like with exploding e-cigs (although there may be fire there, too). The explosion part comes from the
package, specifically the sealed steel can. Not all Li-ions are subject to violent explosions. The case needs to be fairly strong, since modest pressures are generated under some charging conditions (top end IIRC?), but it's extreme pressures we need to worry about. If you look under the positive end of 18650s you'll see the pressure safety (usually a piercing point and pressure diaphragm). The explosion comes from
boiling not burning the electrolyte. Non flammables ones would blow up just as readily AFAIK.
The energy released in such an explosion comes from the stored energy in the battery charge, not the flammable nature I think. At the instant the case bursts and starts stuff flying, the fire (from the flammables) hasn't quite started yet since there was no Oxygen inside?
Tossing one into the campfire will probably get you the same spectacular results I'd think.
In traditional bombs, not only is there a flammable but an oxidizer inside like with Black Powder where the Carbon and Sulfur are fuels (flammables) and the Nitrates provide the necessary Oxygen. Here the rapidly burning gasses rapidly raise pressure enough to burst the housing. Firecrackers only go 'bang' with intact wrappers. Slice one open and it fizzles. In explosives like say TNT the 'flame front' is much faster, the energy coming instead from breaking chemical bonds rather than combustion. When this burn speed is faster than the speed of sound, air can't get out of the way fast enough, so no confinement is usually needed for an explosion. Many over 10,000 feet a second, while sound is about 1100.
But it's the confinement that makes an explosion here, the difference between your cell phone melting down and your e-cig blowing your teeth out and putting you in the Emergency Room. Same Chemistry, different Physics/Engineering.
That's how I understand it, anyway.
Regards to all.
OF