Why is my AirTag battery different from CR2032

Your tag then appears to be defective.

That white plastic component on the left (the battery holder) is NOT designed to ever be detached from the “body” on the right.

The battery is on the “other side” of the battery holder, under the silver cover.

The silver cover is what is designed to rotate — and then detach — from the battery holder.

As the primary electrical connection from the battery has been severed [IMO irreparably] this particular AirTag is best consigned to the electronics recycling system.

That does not appear to be an Apple AirTag.

How to replace the battery in your AirTag - Apple Support

See https://m.youtube.com/watch?v=Jylbd-SF28k

You’ve opened the entire case (the internals look similar to, but may not be an AirTag)

+1

Unless that’s possibly the bottom of the battery compartment on the left. 🤔

And the “electronics compartment” has been intentionally accessed for some — possibly nefarious — reason.

You’re most welcome.

These are the fun (i.e. technically interesting) sorts of questions.

I actually opened-up an AirTag (non-destructively) to compare it’s innards to your images.