https://www.theverge.com/circuitbreaker/2017/11/3/16602052/iphone-x-ifixit-teardown

iFixit teardowns have been synonymous with iPhone launches, and today’s iPhone X teardown reveals how Apple has completely revamped the phone’s innards, figuring new ways to pack more features inside its very slim body.

The teardown reveals some surprises, including two battery cells in the iPhone X (a first in any iPhone model). The combined battery has a 2,716mAh capacity, which is slightly bigger than the battery found in the 8 Plus, which is 2,691mAh. iFixit says the iPhone X’s dual-cell battery design is more about saving space rather than changing the capacity of the battery itself. The two-cell design allows for more “creative shapes and placement,” and so Apple is able to take better advantage of leftover space.