Warning: Be careful not to puncture the battery, as doing so could cause it to explode.

Insert an iFixit opening tool beneath the battery and gently pry it up.

If you're having trouble removing the adhesive, use 91% or higher isopropyl alcohol. Apply it in small quantities with a syringe, if possible, to avoid damaging any electrical components.

After removing the battery, clean the area where the adhesive was, so it's ready for the new battery.