Battery technology presents the the biggest hurdle in going to electric vehicles. Current batteries don't provide the range of fossil-fuel-powered vehicles. Worse, batteries take a lot longer to recharge than the time it takes to fill a 16-gallon tank with gasoline. But this isn't the end of the story, as battery technology is still being developed. For 100 years we got along with lead-acid batteries, but research has gone into high gear to look at new battery compounds that might prove to be the breakthrough that lets electric vehicle performance equal or surpass that of gasoline-powered cars. Lithium ion is the current favored chemistry, but other, more exotic compounds are being researched, such as zinc-air and lithium-polymer. Electric car enthusiast Mike Thompson has compiled a chart of current battery and electricity storage technologies, along with various specifications. The most useful number in the chart is watt-hours per kilogram (Wh/kg), which shows the energy density of the power source. The more electricity you can pack into a battery, the better range you will get for an electric car.
According to the chart, research on lithium-polymer batteries shows that they could hit 400 Wh/kg, the highest of any other technology. Zinc-air is second at 200 Wh/kg, while nickel-metal-hydride, used in hybrid vehicles, is at 80 Wh/kg.