That being said they're astronomically more efficient than even an ideal carnot engine.
An easier to recycle battery that had very slightly fewer charge cycles could be a net win. For scale this depot has enough lithium for ~10 billion of EV’s using Tesla’s battery chemistry and pack size as a benchmark. How expensive it is to extract is however unknown.
Fun!
That was not what I was trying to say.
The math is something like:
MTBF cycles * capacity of battery = usable "life" of the battery
usage of lithium by mass in the battery * best recycling technology recovery rate = recoverable lithium per battery
((mass of lithium in battery - recoverable lithium per battery) / usable "life" of the battery) = lithium effectively used up per joule of energy used from that battery
It may be that that number is zero grams, or a few picograms, so it doesn't matter. But I don't think with current recovery rates on battery recycling that's true. So, while a failed battery has the same mass of lithium as a new battery, effectively every charge-discharge cycle "uses up" some lithium, which ultimately ends up wasted as recycling byproducts or unusable salts.