If they are able to be used in cars for a million miles, they will still be able to be used after that at a lower performance. It's likely that a used "million

If they are able to be used in cars for a million miles, they will still be able to be used after that at a lower performance. It's likely that a used "million mile" battery will be even more valuable, since it presumably loses performance more slowly than other batteries. So at the point where it's performance drops below "useful in EVs," it will still have a ton of life left before the performance drops below "useful as part of the grid."