10.20.6 Secondary Lithium-ion (Rechargeable) Cells and Batteries
Small consumer-type lithium-ion cells and batteries like those used to power cell phones and laptop computers are mailable with the following restrictions. Each cell must contain no more than 1.5 g of equivalent lithium content per cell. Each battery must contain no more than 8.0 g aggregate quantity of equivalent lithium content per battery. Additionally, each cell or battery must meet the requirements of each test in the UN Manual of Tests and Criteria, Part III, and subsection 38.3 as referenced in the DOT's hazardous materials regulation at 49 CFR 171.7. All secondary lithium-ion cells and batteries must be mailed in a firmly sealed package separated and cushioned to prevent short circuit, movement, or damage. Except for batteries installed in equipment, they must be in a strong outer package. All outer packages must have a complete delivery and return address. These cells and batteries are mailable as follows:
a. Via surface or air transportation when individual cells or batteries are mailed or when properly packed with or properly installed in the equipment they operate. Cells or batteries properly installed in the device they operate must be protected from damage and short circuit, and the device must be equipped with an effective means of preventing accidental activation. The outside of the package must be marked on the address side "Package Contains Lithium-ion Batteries (no lithium metal)."
b. The mailpiece must not contain more than 3 batteries.
So it looks to me as if they can be airmailed, but you can only put 3 batteries in each package.
Gee, I guess those 5 batteries I received from China must not contain any lithium.