Let's take a deep dive into Apple's battery origami:

Since 2015 when the 12" MacBook was announced with a terraced battery, Apple has increasingly sought to take advantage of every bit of space in the chassis of their devices using contoured batteries.

These patents show solutions they have found to get around tricky problems like thermal expansion, using different layer sizes and precisely folding electrode sheets cut into complex shapes to fit those contours.

The extra corners and edges of the single-cell battery in the XS will be prone to extra stress—it will be interesting to see how this new battery performs as it ages.