Pry up the battery with tweezers. Apply some alcohol while prying.

Get a new AirPods Pro battery. It can be seen that AirPods Pro uses button battery which is distinct from the cylindrical battery in AirPods 1 and AirPods 2. The button battery is a lithium-ion cell with a steel shell and better explosion-proof performance.

Other than that, there are two kinds of AirPods Pro battery. We need to distinguish between left and right for replacement.

Measure the new battery voltage ahead of replacement. It can be seen that the battery is good with normal voltage.