By having one big battery instead of two conjoined, you can ditch a little bit of packaging and eliminate the small gap between them, maximizing your capacity. Picture two small train cars in a row. Next to those, put another car that’s as long as both small cars combined. You can fit more into the single, because you’re eliminating two walls and some in-between space. The same principle applies.
We all tease Apple about all of its products getting thinner, but it takes incredible feats of engineering to actually do that. Featured image credit goes to iFixit.
Check It Out: How Apple Engineered the iPhone XS Battery