Pull on the adhesive tapes slowly and continously to avoid breaking them, it a PITA removing the battery if they break as you will have to pry up the battery with risk of damaging them. Damaging the battery can cause a fire.

I broke both tapes on mine and had to pry off the battery, lucky i didn’t puncture it.

Successful replacement of iphone 6 battery today. Removing the adhesive tapes under the battery is a bit difficult, i broke both tapes off after pulling and repositioning my fingers on it. I suggest slowly pulling the tapes in continous motion making sure it is flat and not twisted while pulling.

Also, the kit i got did not come with ifixit plastic card to push under battery if adhesive tapes broke. I used the spudger instead to pry off the battery at bottom end and grab the end of the tapes underneath with tweezer. Luckily i was able to pull remaining adhesive tape without them breaking again.

So remember to pull slowly and continously.