With intelligent charging practices (which often come at the expense of stored energy) and temperature control, modern lithium cells asymptote to ~20% capacity

With intelligent charging practices (which often come at the expense of stored energy) and temperature control, modern lithium cells asymptote to ~20% capacity loss and stay there for, well at least since the model S came out, still counting. Or that was the case a couple years ago when I looked into it. The difference in the battery life in a leaf vs a tesla is qualitative not quantitative. The motivation to make phone batteries last longer wasn't there at first until it provided negative press, now intelligent charging is fairly common in phones. Thermal management is harder.