This sounds more like a hardware problem than software. The charger it was plugged into overnight, is it an Apple Original brick and Lightning cable? Cheap chargers and cables can cause the charge circuit in the phone to blow.
I would suggest that you start by taking it to a reputable repair shop in your area to have it looked at. It could just be the battery but it may also require a micro-soldering repair. Not every repair shop offers micro-soldering repairs so you would have to search for one locally or mail it in to a specialist in that event.