Technology

Yes, but to increase longevity energy density goes down substantially. Manufacturers (and many users including myself) would not make this decision for something as weight and size sensitive as a phone. The lithium ion batteries currently used already last for 2 years after all and are relatively small. A single model S battery contains 7104 individual cells for comparison. Further, lithium battery recycling has made substantial progress over the last year and will already need to be done at scale when higher volumes of EV batteries have reached their end of life. The impact of the of life phone batteries even from the entire world will be dwarfed by that of the 26 million EVs already on the roads today with thousands of cells each (or equivalent if using prismatic cells).

Some cars use LiFePO4 batteries for the superior longevity. But the range is reduced to somewhere between 1/2 and 2/3 their lithium ion counterparts. The industry is moving away from this trend in recent years in favor of traditional lithium ion with a software limited charge/discharge range.