The most specific information I could find about this is from
http://safetravel.dot.gov/whats_new_batteries.html.
The TSA annoucement is a bit confusing. The photo shows lithium ion batteries on the home page but the the text really seems to only be describing non-rechargeable "lithium" batteries like Energizer e2's.
The new rules affect both Lithium Metal “primary” batteries (i.e. Lithium AAs and 123s)
and Lithium-Ion rechargeable batteries.
The way each type of battery is regulated depends on its “equivalent lithium content” in grams. The chart at the bottom of the
Safe Travel site shows all the technical details about the battery types and quantities of “equivalent lithium content”. It’s too bad that many of the TSA employees don’t understand technical.
From what it looks like, the main Lithium Metal “primary” (AA and 123) batteries are only allowed in your checked luggage if they are installed in their respective device. Any loose Lithium Metal “primaries” must be in your carry-on.
As far as Lithium-Ion rechargeable batteries, any battery that is under 8 grams of lithium (~100 watt-hour battery) is only allowed in your checked luggage if it is installed in its respective device. Any loose Lithium-Ion batteries must be in your carry-on.
Large Lithium-Ion batteries (greater than 8 grams of lithium/100 watt-hours) are a special case. Check the chart for details.