There are standards being developed for the secondary-use cycle. Mr. Breton is correct on how they can be used afterwards. Really, most people don't know that there is a lot of life left in the battery—it's 80%. Once that battery depletes below 80%, it's no longer useful as a car battery but has a number of years left for use as a secondary source.
On November 25th, 2020. See this statement in context.