Remove the battery.

Do not reinstall a damaged or deformed battery, as doing so is a potential safety hazard. Replace it with a new battery.

Before installing a new battery remove any remaining adhesive from the phone, and clean the glued areas with isopropyl alcohol and a lint-free cloth.

Secure the new battery with pre-cut adhesive or double-sided adhesive tape. In order to position it correctly, apply the new adhesive into the phone at the places where the old adhesive was located, not directly onto the battery. Press the new battery firmly into place for 5-10 seconds.