Remove the battery.

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

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

During reassembly, follow this guide if you're using a pre-cut adhesive card.

If there's any alcohol solution remaining in the phone, carefully wipe it off or allow it to air dry before installing your new battery.

During reassembly, temporarily reconnect the battery to the motherboard to help align it correctly. Disconnect the battery after it is seated.