Applying adhesive remover or high concentration (over 90%) isopropyl alcohol to the battery will make the battery removal significantly easier.

If you are using adhesive remover, follow these preparation steps first.

Apply a 1-2 drops of adhesive remover or isopropyl alcohol in each battery corner.

Be careful not to apply more than a few drops of liquid at a time, as liquid can seep into the frame cutout (under the battery) and damage the exposed display.

Wait for a minute to allow the liquid to weaken the adhesive.

Alternatively, heat an iOpener and apply it to the right side of the front of the phone for two minutes or until the battery is warm to the touch (from the transferred heat).

Do not heat the battery directly. Only heat the front side of the display, underneath which the battery resides, to avoid overheating the battery and risking a fire.