[Matrix Leader]

And another source:

"For alkaline batteries (the most common kind of household battery), putting them in the freezer will extend their shelf life by less than 5%. And cold batteries can't be used immediately -- you have to wait until they've warmed up to room temperature first. If you need those batteries for a flashlight in an emergency, this could prove problematic. When stored at room temperature, alkaline batteries retain 90% of their power, and the average shelf life of alkaline batteries is five to seven years.

For NiMH and Nicad batteries (often used for electronics), storing them in the freezer might be more practical. These kinds of batteries lose their charge after a few days when kept at room temperature. But they'll retain a 90% charge for months if you store them in the freezer. Just like alkaline batteries, you'll need to wait until they've warmed up before using them. However, this isn't a problem when you need new batteries for your digital camera or other electronic gadget.
"