Qi is an wireless power transfer system, and according to wikipedia, OOK 2kbps communication between charging station and receiver is established in order to detect non-receiver object on charging station. So I guess some circuit inside it, and dis-assembled...

This is the inside of Qi-receiver. These two sides are simply attached by adhesive thin tape. The grey part of left part is some thin magnetic material, which will have high permeability to produce high magnetic flux density. The right side (circuit side) has a coil and circuitry.

The coil is wounded by 5-in-one (not bifilar but pentafilar ?) 5-lines are consisting this coil so the number of turn is not so much. During operation, this part produces some temperature increase. This thin coil is simply fixed by adhesive sheet, and the structure is simple so may be I would make some different form.