After a little surfing I found this page:
which states that we can bring 2 spare lithium batteries on a plane. They recommend packing them in the original container and/or a plastic bag.
On the same subject I want to recommend the Igo power extender. It's relatively cheap and uses 2 replaceable alkaline AA batteries. I have used it charge my Kindle using the A00 tip, which is also the one used for Sprint cel phones. Other Igo tips can be used to power low power gadgets such as cel phones and Bluetooth headsets, in addition to the Kindle.
I'll probably buy and extra Igo charger and tips for my phone and Kindle to keep in the car for a just-in-case scenario. I'd hate to lose phone service or Kindle capability due to run down batteries.
You can peruse the Igo charger at:
The tip for an Iphone is A61. Just about any small gadget (not a notebook) can be charged with the Xtender if you have the right tip.