If you weren’t already convinced that the 13″ MacBook Air of the 2010s (specifically, the form factor that started in 2010 and ended in 2017) was one of the greatest laptops ever made, allow me to heap additional praise on it now.
The process of replacing the built-in battery with a new one is very easy: Unscrew and remove the bottom cover, unplug the battery cable, unscrew and remove the old battery. Insert the new battery and secure it with screws, plug it into the motherboard, replace the bottom cover and secure it with screws. That’s it. This is only a tiny bit harder than swapping removable batteries in a Thinkpad was, back in the late 1990s when pretty much every laptop had removable batteries.
iFixit has the instructions and the replacement battery part, which can optionally be ordered with a repair kit that includes the weird pentalobe screwdriver tip and a teeny T5 torx tip, with a screwdriver body that can use them.