Use a nylon spudger to disconnect the two clips holding down the battery: one on the bottom and one on the top.

There is glue holding down the battery so be careful when removing it.

Pry the battery out of the phone with a nylon spudger.

Alternatively, slide a flat plastic card underneath the battery to separate it from the frame.

Do not reuse the battery after it has been removed, as doing so is a potential safety hazard. Replace it with a new battery.