The Android smartphone charging protocol is a bit of a mess. While Google itself has been using USB Power Delivery protocol since last year to provide fast charging on its devices, most Android devices rely on Qualcomm's Quick Charge, while others have come up with their own version, such as the DASH charging on the OnePlus 3. Unfortunately, both of these are proprietary solutions and require a specific piece of hardware on the device/charger/cable, licensing, as well as messing around with the standard USB power delivery protocols. It also makes them incompatible with desktop or notebook...
Source: http://www.gsmarena.com/google_recommends_oems_use_usbpd_could_make_it_compulsory_later-news-21584.php
