Lithium-air batteries could improve the performance of standard lithium cells by 10 times, but they've got to do something about the lurking obesity problem.

Lithium-air batteries may require three times as many lithium-ions as standard lithium-ion batteries, according to Jeff Dahn, a professor at Dalhousie University in Halifax, Canada during a presentation at the Almaden Institute taking place this week at IBM's Almaden labs.

Quick primer: Lithium-air batteries store energy by combining lithium with oxygen. Break those two elements apart and you get spare electrons. Lithium-cobalt batteries rely on the larger element cobalt. The relative lightness of oxygen is where lithium air gets some of its potential advantages.

On a theoretical basis, lithium air (two lithiums and two oxygens) can store 3,400 watt hours of energy per liter. Lithium cobalt can store 1,450 watt hours per liter. As a result, the lithium oxide should hold more energy.

But standard lithium cobalt is incredibly efficient. Approximately 95 percent of the energy can be harvested. Lithium air only gives up 79 percent, and that's the optimistic figure. Small amounts of the active materials inside a battery also get consumed with each charge. Thus, battery makers may have to put three to four times as much lithium in a lithium-air battery.

When you look at it from a 3-times perspective, the volume of lithium air drops to 1,254 watt hours per liter, or worse than regular lithium-cobalt batteries. Lithium sulfur, another futuristic lithium chemistry, also falls beneath standard lithium cobalt under this standard.

To move into production, manufacturers will likely have to conquer the harvesting issue.

"The volume of the excess lithium is a big deal," he said. "The potential safety issues are also a big deal because there is more juice in there than there needs to be."

And for those of you who like numbers, Dahn said good things about zinc oxide batteries. Zinc oxide can hold 830 watt hours per kilogram.