ARGONNE, Ill.—Twenty miles southwest of Chicago, government researchers are pursuing the automotive version of Mr. Right.
He's powerful. He has endurance. He isn't too expensive to have around. And he never, ever explodes.
That's one way to think of the perfect car battery, which will have to balance many different factors to lure the American masses to the electric car.
For the moment, though, Mr. Right is just a set of equations in a notebook.
"Theoretically, it works on paper," said Don Hillebrand, who directs the Center for Transportation Research at Argonne National Laboratory.
At Argonne National Laboratory and elsewhere, researchers are just beginning to crack the basic science behind a promising technology: lithium-air batteries. If their theories are right, these batteries will have five to 10 times the energy of lithium-ion batteries, the big battery pack that's powering the first wave of electric-drive cars.
"Lithium-air is where we're going," Hillebrand said. "You can't foresee the future, but right now, that's the place where I think we see the endpoint, the end solution for ... the battery. The battery everybody's looking for."
But as engineers get closer to perfecting the lithium-ion variety, lithium-air has a long journey to replace the batteries of yesteryear.
A good idea that's still en route
"Nickel-metal hydride's an adult. Lithium-ion is a developing adolescent. And lithium-air, we're just looking at the ultrasounds," Hillebrand said.
Some say lithium-air will only carry triple the energy of lithium-ion; others project a hundredfold increase. Regardless of the estimates, all agree that lithium-ion could use a tuneup.
The reason has to do with "battery chemistry," a term that describes what makes the device go.
Batteries have an anode and a cathode, two materials that exchange ions -- in this case, lithium ions. When the ions go one way, the battery charges up; when they go the other way, the battery releases its charge.
Different materials for the anode and cathode, of course, affect this back-and-forth movement. For example, they can speed it up, move a larger number of ions, or reduce the number of times the battery can repeat the exchange -- that is, shorten the battery's life.
Lithium-ion chemistry is considered an improvement over past efforts to power electric cars. Previous options were so large and heavy that they were just barely economical to lug around. Lithium-ion packed so much more energy into less space and weight that major automakers christened it for their latest lineup of electric and hybrid cars, including Toyota's Prius, General Motors' Volt, and Nissan's Leaf.
The change came at a price, though. Today, lithium-ion batteries are commonplace and commercialized for laptops and cell phones. But the larger batteries needed for cars remain their most expensive component -- and the one deemed most essential to helping millions reach the road.
In the coming years, many expect these costs to decline. Even so, plenty in the battery field foresee the day that lithium-ion, so essential to the present day, will face retirement.
A battery that could challenge petroleum
"Let's say we want to electrify the entire fleet of vehicles in the world," said Jeffrey Chamberlain, head of Argonne's Energy Storage Major Initiative and one of the lab's leading battery chemists. "Lithium-ion batteries will get us partway there. But in reality, they're not quite high enough in energy density or quite low enough in cost."