20 years is a very long perspective and the car graveyards will be overloaded by lithium bombs. Remember if your electric car are involved in a crash(regardless of the damage in the car) is not allowed to use anymore before the battery is replaced by a new. The cost to repair it is almost similar to a new car. This is the insurance company policy, and cars with minor damages are not repaired because of the fear the lithium battery is damaged and can cause fires.
I did not know the danger about those batteries before I read this story. Next time by phone falls on the floor I might pick up a fire bomb. Quite scaring, right? Some sellers have missed informing us somewhere.