It seems a bit strange that just as electronics manufacturers are looking for things like fuel cells to replace lithium ion batteries, car makers are moving towards lithium ion batteries for hybrids.
Currently, hybrid vehicles use NiMH batteries, but Subaru, Toyota and Nissan are choosing Li-ion batteries instead. Subaru will be putting the batteries into production vehicles next year and Toyota will put them in their Prius starting in 2008 or 2009.
The advantage of these batteries is in the lighter weight, the higher energy density and greater power that they offer over their NiMH counterparts. With those advantages, you would think that Li-ion batteries would already be the norm. The problems, though are that the Li-ion batteries raise some safety concerns which need to be accommodated and they are more expensive and have a shorter lifespan. To overcome these problems, car makers are partnering with battery companies to improve the technology. Toyota, for example, owns 60% of Panasonic EV Energy.