There are already lithium-ion batteries in some Toyota vehicles (the Prius Plug-in Hybrid ... Toyota is also working on future battery technologies, like solid state packs.

When the next-gen Prius bows in 2009, Popular Mechanics says, it "will almost certainly use a plug-in system. The car may launch as a normal hybrid and later, once the lithium ion battery ...

Lithium battery packs reaching ... failure of one to bork the entire battery. One of the most interesting examples we’ve heard of this is in the Toyota Prius, but that’s a story for another ...