The early Leafs had carp batteries with a massive degradation in capacity over time, which are now coming into the second hand market. The pace of innovation and increases in energy density of batteries is astounding. We're probably only 2 years away from a 400 mile range electric vehicle on a single charge. Tesla batteries are pretty good. They heat their batteries when it's cold and cool them when they're hot, so they're always at the optimum temperature to prolong their life. The batteries in the Model S are replaceable, but in the latest Model 3 they're integrated into the car, so Tesla have decided they aren't worried about having to replace them. A lot of people's preconceptions with electric vehicles are being thrown out because of the pace of innovation. 5 years ago is like the stone age. Permanently installed batteries are probably here to stay.
I'll be interested to know if they launch the new Defender with a full electric version or it'll be a hybrid and we'll have to wait.