[centizen]

They aren't really that easy to weaponize, at least not any more. The earliest kinds of Lithium cells actually contained elemental lithium, and could easily cause fire or explosion under certain conditions. Think the Dell laptop fire batteries.

Lithium _Ion_ batteries produced today are newer designs which use an intercalated Lithium compound (usually with Cobalt, Iron or Manganese) which greatly improves the stability of the battery while under stress. Further to that, pressure venting is almost always incorporated into the canister enclosing the cell, allowing it to depressurize in a safe manner similar to capacitors.

That's not to say they are totally safe - all batteries require a great deal of care and not all Lithium batteries incorporate these safety features. The pouch cells used in RC aircraft, for example can catch fire fairly easily due to their lack of a strong outer shell, their extreme power density and lack of any protection circuitry. These are heavily regulated and you would not be allowed to take them in your carry-on, and all Lithium Ion batteries over a certain Wh rating are similarly controlled.

[lytfyre]

> [RC pouch cells] are heavily regulated and you would not be allowed to take them in your carry-on

Speaking at least for Canadian airlines, you're incorrect - I asked ahead, and was told that I could bring them, but _must_ have them in my carry on. (and protect the connectors, etc.)