Why Do Lithium-Ion Batteries Explode?

While lithium-ion batteries are, on the whole, incredibly safe they do very very occasionally catch fire or explode. When it happens, like with Samsung’s Galaxy Note 7 fiasco or HP’s more recent laptop recall, it’s always big news. So what’s going on and why do batteries sometimes go out with a bang? Let’s find out.
by Harry Guinness via How-To Geek