Li-Ion batteries are completely different than NiMH when flying. There have been instances of TSA or airline personnel throwing your battery away due to not understanding the rules. Currently, TSA regs say primary Li-Ion batteries are not allowed on flights (non-rechargeable ones), at least for non-personal use (which means they'll throw them out no matter who you are.) Secondary (or rechargeable) Li-Ion batteries are allowed ot be checked, but you run the risk of some Bubba deciding it shouldn't be on the flight and tossing it on you.
I personnlay hate diving a handheld now that I've played with a can, so I will be attempting to take my can with me on my trip. I will be wrapping my battery in the most current TSA regulations and putting it in my clothing suitcase (alone, without any other scuba gear in it) with the appropriate regulation highlighted, so that hopefully I'll not have to buy a new $100 battery before I get back, and so they don't destroy the rest of my gear when they see the little thing that looks like a stick of dyamite in the x-rays