iPhone fast charging is possible with the 2017 models, but it’s a seriously underutilized feature because the devices don’t come with the right adapters. But Apple is reportedly going to ship the 2018 iPhone models with the adapter and cable needed to get a 100% charge much quicker.
It’s one of the puzzles of last year’s devices. They support USB-C fast charging, but come with USB-A adapters that take much longer.