A Sodium Ion battery would be great for cellphones.
So, Sodium has less energy density, about 50~70% that of lithium, but it can be run 100% to 0% every day for several thousands of cycles instead of lithium losing 20% after 300-500 cycles. That'll likely outlast the phone. Never need to open it up for a replacement due to a weak or dying battery.
It can be charged 0~100% in 5~6 minutes, with no ill effects. That's 240W for a typical 20Wh battery. If you're away from home, use any laptop charger, that'll be 65w+ instead of the 5~45w. Doesn't slow down half way either, like lithium phones must, full speed the whole time.
Runs 90% capacity at -40 ℃, can handle 80 ℃ so no thermal throttling needed for battery health,
If you take the advice of running your lithium battery under 80% down to 20%… you've effectively got the same capacity as the sodium battery without the benefits.