Its all explained here;

http://en.wikipedia.org/wiki/Rechargeable_battery

The Table of rechargeable battery types shows all the different Battery chemistries with their pros and cons.

I still even have a C-cell Maglite with a high efficiency 3W Cree LED using Everyready 1600 mAhr NiCd's which are about 15 years old, which must have spent the last 10-12 years sitting in the back of a cupboard drawer. They just needed to be recharged. Something I suspect might be a little tricky to do with all these lightweight high technology Lithium ion technology batteries.

Even NiCds have their place even for spacecraft and satellite power requirements.

http://en.wikipedia.org/wiki/RazakSAT