Lithium-ion batteries

Back in 1925, long before the X-Prize foundation even existed, an inventor by the name of Sakichi Toyoda reportedly offered a prize of 1 million yen for the invention of a battery that would produce more energy than gasoline. As you can probably guess, no one has claimed that prize yet. However, Toyota thinks this target may be possible in the future and thus created, in 2008, a research division to work on "revolutionary batteries." Three years later, this division has been giving technical presentations on batteries that have breakthrough energy density levels. This is especially intriguing coming from a company that still uses NiMH batteries in its current-gen Prius.

Current lithium-ion batteries top out at an energy density of around 620 Wh/l (Watt hours per liter) and have a theoretical limit well below the energy density of gasoline. But there's more to advanced automotive battery technology than li-ion. Toyota believes solid-state batteries will have the capacity of over 1000 Wh/l and metal air batteries would at least double that figure again. While those are amazing numbers, the energy density of gasoline is closer to 10,000 Wh/l, so we are not exactly sure how Toyota plans to get to Sakichi-level batteries. Will his prize go unclaimed for 100 years? Also, does it really need to be reached for plug-in vehicles to take off?

While setting lofty energy-density goals is great and all, what really needs to come down is cost. The main reason cars like the Nissan Leaf don't have larger batteries is money. Engineers can always design around obstacles like a heavy or large pack, but there's not much they can do if the pack costs $50,000 dollars. Not yet, anyway.

[Source: Plugin Cars | Photo: Jonas Dalidd]