Apparently, Oppo found a way to safely implement "air-charging" into smartphones using a new FreeVOOC coil and an electromagnetic emitter that has a 10-meter range. This allows the batteries to constantly charge at 5-10 W while in the range of said emitter, so the phone supposedly never runs out of juice.
https://www.notebookcheck.net/Oppo-Reno-Ace-Infinity-to-include-FreeVOOC-air-charging-tech-that-keeps-batteries-charged-forever.459650.0.html