Sorry for the late reply, but you might be interested in this report from the California Lithium-ion Car Battery Recycling Advisory Group [1].

I'll quote a brief section:

> In general, batteries will be retired from use in an EV when the range and performance is no longer acceptable to the driver. The remaining capacity of the battery at the time of retirement will vary depending on consumer preference, but it is generally assumed to be between 70- 80%.

> Given the large capacity and high performance of modern vehicle batteries, retired batteries could still offer significant value in lower-power, secondary applications, such as storing energy from solar panels to be used in off-grid or peak demand-shaving applications.37

> A growing body of research has examined the environmental impacts and technical and economic feasibility of repurposing batteries for use in second-life applications.38–42 Since repurposed batteries are a relatively new phenomenon, data about their performance is uncertain, particularly because of the uneven degradation of battery cells over time. However, it is estimated that battery lifespan can be extended by 10 years or longer depending on the application.38,43,44

[1] https://calepa.ca.gov/wp-content/uploads/sites/6/2021/12/Fin...