Just FYI. I came across this lithium battery safety video here:
This was done by a company marketing a safer type Li battery. Pretty sobering results. Admittedly, most of the time you don't expect your battery pack to take a rifle bullet. But it's impressive to me that there is a lithium chemistry (lithium ferro-phosphate) that can actually take this treatment without bursting into flame, like the lithium-cobalt cells very energetically do.
The phosphate type cells have somewhat lower energy density than Li-Co, but I believe the main barrier to adoption is some ongoing patent disputes on the technology.