FAA Regulatinos on Li-Ion Batteries
Not quite right, according to these documents:
FAA: "Except for spare (uninstalled) lithium metal and lithium-ion batteries, all the batteries allowed in carry-on baggage are also allowed in checked baggage [...]"
"Lithium ion batteries (a.k.a.: rechargeable lithium, lithium polymer, LIPO, secondary lithium). Passengers may carry all consumer-sized lithium ion batteries (up to 100 watt hours per battery)."
[From: https://www.faa.gov/about/office_org/headquarters_offices/ash/ash_programs/hazmat/passenger_info/media/Airline_passengers_and_batteries.pdf; referenced by: https://www.tsa.gov/travel/security-screening/prohibited-items]
In short; devices with lithium ion battteries up to 100 W/h are allowed in checked baggage.