edit: after 20 comments, i’m adding a post description here, since most of the commenters so far appear not to be reading the article:
This is about how surprisingly cheap it is (eg $15,000) to buy a complete production line to be able to manufacture batteries with a layer of nearly-undetectable explosives inside of them, which can be triggered by off-the-shelf devices with only their firmware modified.
It depends on the explosive, C-4, and I think all plastic explosives, will burn in a fire.