Not saying it's entirely unrelevant, but when looking at energy consumption by production and by usage of smartphones, the usage basically consumes no energy at all (https://imgur.com/VHpJ5et).

That is probably because batteries can hold a very limited amount of energy and therefore mobile software is developed to use very little electricity.

But on the other hand, less energy efficient chargers wont help this. I just mean it's not the big problem about our smartphones energy consumption.