How improved batteries will make electric vehicles competitive
November 9, 2012
For electric vehicles and plug-in hybrids to compete with gas-powered cars, battery prices need to drop by between 50 and 80 percent, according to recent estimates by the U.S. Department of Energy.
Improvements to the lithium-ion batteries that power the current generation of electric vehicles may be enough, MIT Technology Review reports.
Electric vehicles cost less to operate than gas-powered ones, but that economic advantage largely disappears in the face of expensive batteries. The battery pack for the Chevrolet Volt costs about $8,000. The larger battery in the Nissan Leaf costs about $12,000.
But the cost for the Leaf battery could drop to under $4,000 by 2025, according to a recent study by McKinsey, just by increasing the scale of battery production, forcing down component costs through competition, and approximately doubling the energy density of batteries, which reduces materials costs.
One startup, Envia Systems, has already built prototype lithium-ion battery cells that store about twice that of the best conventional lithium-ion batteries and can be recharged hundreds of times (see “A Big Jump in Battery Capacity” and “Should the Government Support Applied Research?”). And crucially, it’s similar enough to conventional lithium-ion batteries that it can be made on existing manufacturing equipment. The technology still needs work, and could take several years to start appearing in cars, the company says.
Not everyone agrees that lithium-ion batteries can reach the low costs needed for electric vehicles to compete with gas-powered ones (see “A123’s Technology Just Wasn’t Good Enough”). Toyota, for one, is investigating more dramatic changes in battery design. One type it’s developing replaces the liquid electrolyte in a conventional lithium-ion battery with a solid material, something that allows for a number of changes in the battery design that could shrink the system and lower the cost. These solid-state batteries and other technologies could cut the size of a battery pack by 80 percent, according to Toyota. Sakti3, a startup with close ties to GM, is also developing solid-state batteries, and recently started shipping prototype batteries to potential customers for testing, says CEO Ann Marie Sastry (see “Solid-State Batteries”).
24M, an early-stage startup based in Cambridge, Massachusetts, is taking a different approach — rather than an all-solid battery, the company is developing a cross between a battery and a fuel cell in which the battery electrodes are a sludgy liquid that can be pumped around. The energy storage material could be stored in inexpensive tanks, and then pumped into a small device to generate power (see “A Car Battery at Half the Price”).
Despite the novel designs, solid-state batteries and 24M’s technology still operate with a familiar lithium-ion chemistry, which could make them less risky to commercialize than more radical approaches that move beyond the lithium-ion chemistry. But these new batteries have theoretical energy densities several times that of today’s electric car batteries.