Grab the pull tab with your fingers and slowly pull it away from the battery, toward the bottom of the iPhone.

Repeat the previous procedure on the two remaining pull tabs.

If the adhesive breaks off underneath the battery and can't be retrieved, apply a few drops of high concentration (over 90%) isopropyl alcohol under the edge of the battery in the area of the broken adhesive strip(s).

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

Use the flat end of a spudger 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.