so many threads on this...
here is an interesting piece by Elon Musk...
An aerospace-capable version of Tesla's battery has been developed for use in SpaceX's Falcon 9 space launch vehicle. SpaceX, also owned by Musk, competes with Boeing/Lockheed Martin joint venture United Launch Alliance for customers. Boeing has thus far declined offers of assistance from Tesla and SpaceX, says Musk.
"They [Boeing] believe they have this under control, although I think there is a fundamental safety issue with the architecture of a pack with large cells," writes Musk in an email. "It is much harder to maintain an even temperature in a large cell, as the distance from the center of the cell to the edge is much greater, which increases the risk of thermal runaway."
"He's engineered [Tesla's battery] to prevent the domino effect, while Boeing evidently doesn't have that engineering," adds Sadoway.
Elon Musk: Boeing 787 battery fundamentally unsafe