When this happens to me I usually bring the phone outside and finish prying there. I throw on a mask and goggles just in case. . I put some salt water into a disposable plastic container and drop the battery in there as soon as it comes out and leave it sitting in there for a few weeks away from anything flammable. I've read that its supposed to neutralize it. Not sure if there's a better or correct method but this always worked for me.