iPhone 6 battery stuck on red logo and wont go into recovery mode
Hi, I am having issues with partners iPhone 6. At first the battery was continuously stuck at 100%. Apple store couldn't find any issues with the phone and just needed to reset the phone. But before we could even do that, the phone was plugged in on charge over night, and now only shows a black screen with red battery logo. The phone has been on charge for hours. We have even tried to heat the phone up and nothing, I have tried to get into recovery mode and nothing. I have plugged the phone on to my mac to try and get iTunes logo to appear and nothing. Seems to be a lost cause. So hoping someone might be able help, or would a new battery by the answer?
iPhone 6, iOS 10.2.1