Is your battery not maintaining a desired lifespan? Is it acting up sporadically causing your phone to turn off on its own? It might be worth it to replace it. Follow these steps for the removal and installation of a new battery.
Locate the small slit on the bottom edge of the device between the back and front cases.
Pop the back case off by inserting your finger and pulling the case away from the phone.
Remove the battery by pushing the bottom edge of the battery up and away from the phone