Hi de hi happy campers

just got a galaxy s7 and found out you can have a fast charger that uses 9v
now i have searched google and youtube for fast charger etc etc and got loads of useless videos of how these chargers work sooo, if someone can enlighten me how they work please...
are they a 9v psu and the phone is happy with it but a none supported phone will fry?
are these chargers output normally 5v with a communication line to make the dc-dc converter push more voltage so any other 5v device will be safe unless it communicates?
inevitably my idea is if i can is make one into my battery bank box for high speed charging, currently im using a 4s10p 18650's going to a 5a buck converter which sits at 5.2v feeding usb sockets and the center data pins are shorted for 1amp charging on normal phones
many thanks for your ideas and help