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    How Improved Batteries Will Make Electric Vehicles Competitive
 
자료번호 :    6
Category :    Application > EV
가격 :    무료 등록일  :    2012.11.10
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There are plenty of reasonswhy electric cars aren’t catching on, but one problem is certain: the batteriescost far too much.

For electric vehicles andplug-in hybrids to compete with gas-powered cars, battery prices need to dropby between 50 and 80 percent, according to recent estimates by the U.S.Department of Energy. Getting there might require inventing entirely new kindsof batteries, but there’s also a strong case that improvements to thelithium-ion batteries that power the current generation of electric vehiclesmay be enough.

The United States could have the capacity by 2015 to produce enoughbattery packs for 500,000 cars. But this year, due to high prices, plug-invehicle sales won’t even reach a tenth of that in the United States. As aresult, advanced battery makers in the United States have struggled. A123Systems went bankrupt. Dow said its battery joint venture Dow Kokam had droppedmarkedly. And an LG Chem factory meant to supply batteries for the ChevroletVolt has been built, but the factory is sitting idle, waiting for demand topick up.

Electric vehicles cost less tooperate than gas-powered ones, but that economic advantage largely disappearsin the face of expensive batteries. The battery pack for the Chevrolet Voltcosts about $8,000. The larger battery in the Nissan Leaf costs about $12,000.

The cost for the Leaf batterycould drop to under $4,000 by 2025, according to a recent studyby McKinsey, just by increasing the scale of battery production, forcing downcomponent costs through competition, and approximately doubling the energydensity of batteries, which reduces materials costs.

One startup, Envia Systems,has already built prototype lithium-ion battery cells that store about twicethat of the best conventional lithium-ion batteries and can be rechargedhundreds of times (see “A Big Jump inBattery Capacity” and “Should theGovernment Support Applied Research?”). And crucially, it’s similarenough to conventional lithium-ion batteries that it can be made on existingmanufacturing equipment. The technology still needs work, and could takeseveral years to start appearing in cars, the company says.

Jeff Dahn, a lithium-ionbattery researcher at Dalhousie University, says cars like the Leaf and Voltuse a special type of flat lithium-ion cell that is made with recentlydeveloped equipment that is still relatively slow. More conventionalcylindrical lithium-ion cells cost roughly half as much to make because theyuse much faster equipment and are made at a larger scale. Dahn also notes thatmany of the components, such as a plastic film that separates electrodes in abattery, are overpriced. “You can’t tell me separator cost can’t come down.”

Not everyone agrees thatlithium-ion batteries can reach the low costs needed for electric vehicles tocompete with gas-powered ones (see “A123’sTechnology Just Wasn’t Good Enough”). Toyota, for one, isinvestigating more dramatic changes in battery design. One type it’s developingreplaces the liquid electrolyte in a conventional lithium-ion battery with asolid material, something that allows for a number of changes in the batterydesign that could shrink the system and lower the cost. These solid-statebatteries and other technologies could cut the size of a battery pack by 80percent, according to Toyota. Sakti3, a startup with close ties to GM, is alsodeveloping solid-state batteries, and recently started shipping prototypebatteries to potential customers for testing, says CEO Ann Marie Sastry (see “Solid-StateBatteries”).

24M, an early-stage startupbased in Cambridge, Massachusetts, is taking a different approach—rather thanan all-solid battery, the company is developing a cross between a battery and afuel cell in which the battery electrodes are a sludgy liquid that can bepumped around. The energy storage material could be stored in inexpensivetanks, and then pumped into a small device to generate power (see “A Car Battery atHalf the Price”).

Despite the novel designs,solid-state batteries and 24M’s technology still operate with a familiarlithium-ion chemistry, which could make them less risky to commercialize thanmore radical approaches that move beyond the lithium-ion chemistry. Butalternatives to lithium ion batteries could be worth their added risk, sincethey have theoretical energy densities several times that of today’s electriccar batteries.

The list is long, includinglithium-sulfur, lithium-air, zinc-air, and magnesium-ion. But each seems tohave its own unique problems. For example, lithium-air batteries, which couldstore 10 times more energy than conventional lithium-ion batteries (approachingthe energy density of gasoline), use lithium metal, which can be verydangerous, and they can’t be recharged very many times.

Even if the issues for the newtechnologies can be solved in the lab, it could take decades to develop themanufacturing needed to reliably make the batteries in the large numbers neededto power cars. The process of solving these challenges will give conventionallithium-ion battery technologies a long time to improve.

 

 
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발행일 2012.11.10 발행처 IBM
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