MIT researchers are developing a capacitor based on carbon nanotubes that potentially could be useful for all-electric cars. Of course, this is still very early stage research, but according to a Boston Globe article, the capacitor could be filled "in about the same time it takes to fill up a gas tank" and could be recharged hundreds of thousands of times, unlike most of today's rechargeable batteries. From the Boston globe:
Electronics professor Joel Schindall drives a Toyota hybrid car, which uses an electric battery to reduce gasoline consumption. But Schindall would prefer an all-electric car, and he thinks his team's research could finally make such vehicles practical…
"It's one thing to postulate it, but that's a long way from being commercially viable and competitive in price." Schindall says he hopes to have a finished example by the fall.
Andrew Burke, research engineer at the Institute of Transportation Studies at the University of California at Davis, said that the new capacitors would have to be many times more powerful than any previously created. "I have a lot of respect for those guys, but I have not seen any data," Burke said. "Until I see the data, I'm inclined to be skeptical."