According to this article Lithium Ion batteries will take over from the current Nickle Hydride for hybrid cars within the next five to eight years because it has better characteristics (saying GM. Toyota, and Ford agree on this point). Toyota already has a Lithium Ion battery in a car sold in Japan (not a hybrid, but used for start/stop ICE operations). A high executive in Toyota implies they may use it sooner. Article states that the Prius will be updated in 2008.
Here is the article==> http://www.carlist.com/autonews/2005/autonews_188.html
Other articles (not this one) indicate that more energy can be captured by Lithium Ion from regenerative braking and that it makes plug-in capability more possible.
Lithium Ion Battery- In a future 2008 Prius?
Discussion in 'Prius, Hybrid, EV and Alt-Fuel News' started by Eric Nothman, Oct 30, 2005.