Remove ten Phillips #0 screws that secure the plastic bottom cover to the chassis.
Six 9.6 mm screws
Four 4.6 mm screws
Throughout this guide, keep careful track of your screws so that each one goes back where it came from during reassembly. Installing a screw in the wrong place can cause permanent damage.
Use a spudger to push the battery connection straight up.
If you pry too hard, or attempt to disconnect the battery with the metal bracket still in place, you risk pulling the connector off of the motherboard.
Make sure the computer is powered off before removing the battery.