There are batteries called "protected" but that means something a little different to what you are thinking. Let me quote
@prof beard (yes, a real professor too!)
"Most protected batteries are only protected against under/over charge, some are also protected against short-circuit. Used PROPERLY in an e-cig and charged in a PROPER charger (which has protection built in), problems with unprotected batteries should be VERY rare indeed - many reported problems (I'm not saying all) are caused by "misuse/mischarging".
Further info; what you have in your iStick is (I believe) is a standard Lithium-ion 18650 battery. That is what Eleaf put in there. If you go out and buy a new mod and a new battery, you still have a Li-ion battery in an e-cig mod.
You have the 20w, which has very, very few problems. The 50w had a rocky start.
BUT, if you are sure you want to move on, then tell us a little more.
(Sorry, I should be helping rather than convince you it's basically a safe mod)