If you mean the '5mW pen' 405's.. It really depends on what you mean by 'lithium batteries'.. There are a lot of lithium batteries on the market.
If you mean normal 1.5v energizer lithium AAA's you can get at the drug store.. these are fine. 3v lithiums and and 3.7V li-ion's should work, BUT.. you only use one battery and a spacer instead of two.
No it wont kill em , i still use one of the pens with 2 10440's. Even though it works , i would recommend using one and a spacer. lithium -ions that is
Yes I should have been clear as to the type of lithium battery. What I had in mind were Energizer 1.7v. That's good to know that little bit of extra voltage won't kill this laser pointer.