Insert the edge of a plastic opening tool between the battery and the outer case near the bottom of the iPhone.

Run the plastic opening tool along the right edge of the battery and pry up at several points to completely separate it from the adhesive securing it to the outer case.

If the adhesive is too strong, apply a few drops of high concentration (over 90%) isopropyl alcohol under the edge of the battery.

Wait about one minute for the alcohol solution to weaken the adhesive.

Use the flat end of a plastic opening tool to gently lift the battery.

Don't try to forcefully lever the battery out. If needed, apply a few more drops of alcohol to further weaken the adhesive. Never deform or puncture the battery with your pry tool.

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.