I had the same problem. Tried out a few lighting to female 3.5mm adapters and got a ton of hissing noise. I ended up with a lighting to male 3.5mm cable and a wireless charging pad I can clip into the air vent that also works with magnetic cases. Now I can use my phone for nav, audio and keep it charged.
Here's the charger:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
I got a coiled lightning to 3.5mm cable and wrapped it around the power cable for the charger so I don't have cables running all over the place. Unforunately it's out of stock.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1