Lithium-ion batteries hate two things: extreme cold and extreme heat. With cold, repeatedly charging a smartphone in sub-freezing temps can create a permanent “plating of metallic Lithium” on the battery anode, according to BatteryUniversity. You can’t fix that problem, and doing it too much is only going kill the battery faster.
The battery is not alone in hating heat: all the internals of any smartphone don’t like it. It’s a computer in there, and computers and hot air are enemies going back decades. Leave your black iPhone sitting in the sun as you laze by the pool someday, and don’t be surprised when it throws a warning at you that it needs to cool off. In the summer, keep it off the dash of the car, preferably in the shade.
Apple specifically says charging iPhones over 35 degrees C/95 degrees F will do permanent damage to the battery; expect the same with any modern smartphone.
Best thing to NEVER do: Don’t let it get too cold or hot when charging. And don’t put the phone in the freezer. That’s dumb.