Silicon nanowires: the new carbon nanotube!
Apparently, the use of silicon nanowires has boosted the energy density of a lithium battery in the lab. Potentially, the use of SiNW could boost the energy density by an order of magnitude.
Stumbling blocks: Using a high-power anode requires a high-power cathode, and some researchers are skeptical of the data. But if it turns out to be true, we might see a full battery EV that can finally beat liquid fuels: the cars that currently get 200 miles to a full charge could conceivably get 2000. At that point, the only part you need to worry about exhausting is the car's driver.
I may be misreading the research, but it also seems that the SiNW gives longer lifetimes as well.