XSp.

Here’s a very interesting demonstration of what could happen with your laptop in certain conditions (faulty battery, extreme heat or intense physical damage/puncturing), given it uses a Lithium-ion battery:

This was a controlled experiment where the battery was “prepared”… probably overheated.
If you follow the news, you probably already heard of at least a couple of cases where laptops suddenly caught fire and exploded. And this is why.
The contents of a Li-ON battery, a common type of battery for mobile devices, are extremebly flammable and can ignite (start a fire) or even explode if they are violated or overheated.
But don’t panic… you don’t need to throw your laptop and cellphone off… it’s still a very very rare occurance. I myself only heard of about 5 cases involving laptops and cellphones, which is nothing if you consider how many of them are out there.
Still, if you wanna play it safe, just DON’T buy cheap chinese pirate batteries, and if some weird accident happens with your mobile device… like it being punctured by some sharp pointy thing or you dropping it in a fireplace, keep your distance for a while… just to make shure it won’t explode.

Source: YouTube Browsage!