According to Apple's own support page, modern Macs do not have user-removable batteries, and attempting to remove the battery yourself may cause damage not covered by warranty. MacBook, MacBook Air, and MacBook Pro models with built-in batteries should only have their batteries replaced and/or serviced by an Apple Authorized Service Provider or at an Apple Store. If you own an older Mac and are not sure whether or not your battery is user-replaceable, contact an Apple Authorized Service Provider or an Apple Store to verify.