The current automobile production is over 70 million/year. The battery capacity for a single car ranges from 30-100 kWh. The current middle class is offering 60kWh (Model3, Bolt, Leaf 2019). So if we assume only 30 kWh/car at the end of the useful battery life, we get about 2 TWh of used battery capacity every year - though that point of time is quite in the future, as batteries are expected to last at least 10 years, if not more. As a comparison, the daily energy usage of Germany is about 1.6 TWh.