FWIW, the Wiki articles on the 787 talks about the battery issues quite a bit.
Key takeaways:
- 787 uses (used?) lithium cobalt oxide (LiCoO2) batteries because they were the only ones certified for flight at the time (late 200xs)
- after the battery incidents and fires Boeing put them in a big-ass containment box (which neutralised any size weight savings gained from using Li-ion…)
- LiFePO4 batteries have since become available, and are considerably safer as they aren’t susceptible to thermal runaway caused by the cobalt in the other batteries.
tl;dr: not all Li-ion batteries are created equal. Not all applications of Li-ion batteries are created equal.
