This Battery University website gives numerous tutorials for batteries and EVs. The following one is about grace capacity and how a lithium ion rechargeable battery gets ‘used up’.
https://batteryuniversity.com/learn/article/bu_1003a_battery_aging_in_an_electric_vehicle_ev
I started thinking about how a regular car engine gets used up in a similar way. The engine slowly wears out and as it does you change the oil and some of the worn metal comes out with the ‘sludge’ that’s in the used oil. No wonder we’re polluting the environment — used oil is partly tiny, little particles of an engine.