If you're still having trouble removing the battery, apply a few drops of high concentration (90% or higher) isopropyl alcohol under the edge of the battery in the area of the broken adhesive strip(s).

Tilt the phone up so the isopropyl alcohol can flow toward the adhesive strip.

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

Use an opening pick or 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.