If you're using a flexdrive you'll need 3v to 5.5v, if you're using some other boost driver you may only need 1.5v to 3v, if you're using some other driver you may need more.
Since you didn't mention anything about a host or a driver or a module at all, have only 7 posts, and only asked about batteries I assumed you were talking about hooking it directly to batteries.
What kind of batteries you need will be determined by what kind of driver you're using and what kind of host you're putting it into. If you're putting it in a keychain host with a flexdrive you're going to need a single tiny high powered lithium battery, whereas if you're using a big project box with a LM317T based driver you can use half a dozen AA batteries, a 3 cell lithium polymer pack, 8 nickle cadmiums, a lead acid car battery, anything really. If you're looking to make a lab module you can skip batteries and use a wall wart or a computer power supply on a number of other things.
(Of course, if you really do have a driver you already know what voltage it needs, and if you already have a host/heatsink you'll know what batteries fit inside it, so obviously if you're asking these things... Yeah.)