Obviously ICE are powered by cobalt mine the gasoline you buy when you fill up at a gas station. The electric motor/generator is powered by a large (and by large, I mean large and heavy) battery pack. Most hybrids on the road today have large Nickel-Metal Hydride (NiMH) battery packs somewhere near the trunk, or under the seats. (Read about the Lexus Hybrid battery pack).
Nonetheless, the Volt is not something in GM's immediate plans. The idea for the Volt would require that a cost efficient 400-lb lithium-ion battery be found. lithium facts-ion batteries of this size are not currently available. Further advances in battery technology would be required to allow GM to consider making the Volt a production car. These are enhancements that could occur in as little as a year, or as many as 20 years. GM has stated that they feel the technology is almost there, yet a vehicle like this is probably about a decade away.
ONickel Cadmium (NiCd) - The oldest battery type used in cell phones. They are the heaviest and lowest capacity battery type. These can be somewhat hard to find.
Avoid using replacement that has been on lithium bettery stock for a while. During storage the battery can lose much of its capacity through internal resistance, which damages it and lowers the maximum capacity.
All power tool batteries degrade over time and lithium ion batteries degrade more rapidly over periods of un-use. Accordingly, use them often and when you're not in the trenches of a project, try to use them at least once each month.
The thing to realize about any battery is it does have a measurable lifespan and efforts to extend it will help but not stop the eventual demise. So the number one thing that you can do to extend the life of any of the newer lithium batteries is always take it out if you are running on DC power to lessen the heat impact. Whenever buying any replacement battery, always check the manufacture date and try to find the newest one available.