I let you think about it.
For starters, the value of these batteries is tens of thousands of dollars. Do you think that this means they will simply be discarded?
The batteries are not a fuel that is consumed, but materials that can be recycled.
However, before they are recycled, old EV batteries can be re-purposed as household batteries - i.e. to store energy from rooftop solar cells or to arbitrage electricity tariffs.
https://www.tesla.com/en_AU/support/sustainability-recycling
In the launch event for their ID3 electric vehicle, VW noted that they consider spent batteries from their EVs a "an asset of the future" rather than a liability of the future. Your specific question is raised at 56:10min into the presentation:
https://www.youtube.com/watch?v=vNlTfgxUQY0
They already currently recycle 53% of materials. A new pilot plant in Salzgitter will increase that to 73% with the aim to extract 97% of materials in future:
https://www.volkswagenag.com/en/news/stories/2019/02/lithium-to-lithium-manganese-to-manganese.html
Around the world, there are companies gearing up to commence recycling of old EV batteries.
Just one example of a company looking to recycle EV batteries:
https://www.redwoodmaterials.com
https://www.forbes.com/sites/alanohnsman/2021/06/14/redwood-materials-spending-hundreds-of-millions-to-speed-recycling-for-ev-batteries/?sh=7eee962b7b64
I think we need to remember that this is a nascent industry that is going to be big in future. No doubt there will be many bumps on the path to improved sustainability. At least with batteries charged with renewable power, there is a basis for recycling. By burning fossil fuels there is none.
