Nor do AirTags contain lithium ion batteries, they use standard non-rechargable CR2032 cells.

CR2032 batteries are lithium batteries, so they do fall under the rules for "Spares" (no to checked baggage). They are permitted "In Equipment" for checked baggage. They are on the "Lithium Metal" row as one of the three example photos.

For the curious: https://en.wikipedia.org/wiki/Lithium_ion_manganese_oxide_ba...