If you have a spare 5 minutes, an informative video to watch on LiIo battery runaway is here:
PC fire due to unstable Lithium-Ion Battery
The video is hyperlinked in this story, which is worth the read:
Boeing Battery Quick Fix May Be Elusive | National Legal and Policy Center
Reading the story makes me (not particularly cautious) re-evaluate my optimism for the 787 with LiIo batteries.