Use this guide to bring life back to your iPhone 6G with a new battery. If your battery is swollen, take appropriate precautions.
This guide instructs you to detach the front panel assembly; this is intended to prevent damage to the display cables. If you feel comfortable supporting the display carefully while peeling the battery out of the iPhone, you can skip the display removal and go directly to the battery removal steps.
For optimal performance, after completing this guide, calibrate your newly installed battery: Charge it to 100% and keep charging it for at least two more hours. Then use your iPhone until it shuts off due to low battery. Finally, charge it uninterrupted to 100%.
You can also use this guide to replace the battery connector bracket.