Another good discussion on battery design, Boeing vs. Tesla.
The battery in Tesla's Roadster used thousands of small cobalt cathode lithium cells - same chemistry used in the Boeing battery. Tesla delivered 2,418 Roadsters beginning in 2008, that contained 16,517,358 of these lithium cells. There are roughly 800 lithium cells total in all the 787s Boeing has delivered. No Tesla customer has ever had a burned up battery. Two customer 787 batteries have fried.
The Boeing battery contains eight GS Yuasa, LVP-65 lithium cells, each weighing 2.75kg (6 lbs). The much larger Tesla Roadster battery uses 6,831 cells similar to the Panasonic CGR18650HG [page 25], each weighing 42g (1.5oz).
The big cells in the Boeing battery are flat, allowing them to be packed tightly against each other. If one of these big cells experiences thermal runaway, a lot of heat is released, and because the cells are touching, adjacent cells will fry, too. Since the eight cells in the Boeing battery are connected in series, there is no practical way to disconnect a faulty cell and still have a working battery. If one cell goes, the whole battery goes - at least it's simple.
Because the cells of the Tesla battery are small, if one cell suffers thermal runaway, relatively little energy is released. And since these cells are round, they are not packed as closely together making it much harder for a failed cell to heat up other cells nearby. With many cells making up the Tesla battery, the battery control system is able to disconnect and isolate a faulty cell and the battery will continue working. Complicated, but it doesn't burn-up.
EV Investors Can Learn From Boeing's Battery - Seeking Alpha