From the iFixIt teardown of the new Air, it looks like there's 2 li-ion batteries, one on each side.
When I look at the Apple technical specs, it states:
Battery and Power
- Up to 15 hours wireless web
- Up to 18 hours Apple TV app movie playback
- Built-in 49.9‑watt‑hour lithium‑polymer battery
- 30W USB-C Power Adapter
I take this mean there's a single battery as it's written 'battery' and not 'batteries'. Maybe this is just one battery that's split in two, I don't know. Maybe others here who are more knowledgeable on this can edit this answer to add that info. Either way, I'm sure these are built in such a way as to be shippable to South Korea by major carriers.
I can't find any info on a battery in the power adapter. My guess is that there isn't a battery in there.