[beefield]

Sorry, you seem to be quoting a bit selectively. From the same article:

> These are batteries that NASA is using, but they’re not batteries that we’d use if we were going to try and make it economical to fly today, because they’re very low in watt-hours per kilogram

[semi-extrinsic]

On the other hand, it's not like NASA was trying to get the lowest energy density possible. They were trying to get a li-ion battery pack with acceptable safety margin. And for this I understand one of the biggest factors is to have sufficient space between cells that a thermal runaway in one cell cannot spread.