If any of the adhesive strips broke off and the battery remains stuck to the rear case, prepare an iOpener or use a hair dryer to heat the rear case directly behind the battery.

Heat the iPhone until the rear case is slightly too hot to comfortably touch. Don't overheat the iPhone, or you may accidentally ignite the battery.

Flip the iPhone back over and thread a strong piece of string (such as dental floss or a length of thin guitar string) underneath the battery.

Wrap the ends of the string around a cloth (or wear gloves) to protect your fingers.

Pull the string from side to side in a sawing motion all along the length of the battery to separate the adhesive. This can take some time since the adhesive is slow to deform, but with patience it will come free. Do not deform or damage the battery.

If you choose to use pry tools to lift the battery out of the iPhone, use extreme caution or you may damage the ribbon cables or the wireless charging coil directly underneath the battery.