I did something similar. Start by looping dental floss under the bottom of the battery. Then put a wet (but not dripping) washcloth in a ceramic microwave safe bowl and heated it for about three minutes. Covered the cloth with plastic food wrap and set the phone on it. Once phone’s hot, I worked the floss towards the top of the phone. Repeated many times until it stalled halfway up the battery. Then I did the same process starting at the top of the battery. After a lot of time the floss came all the way top to bottom. Be patient. Keep at it. It’ll work. And take care never to bend or brake battery.