Better batteries for electric vehicles
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Energy Quarterly
Better batteries for electric vehicles Corinna Wu Improved battery technology, innovative recharging strategies, and generous financial incentives are making electric vehicles more attractive to consumers than ever before.
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n 1996, General Motors unveiled the EV1, an all-electric car powered by a heavy lead-acid battery. The EV1 was enthusiastically received, but a host of economic, regulatory, and technical concerns prompted GM to discontinue the car’s leasing program in 2002. Instead of ushering in an era of electric cars, the EV1 was widely seen as a disappointment. But now, thanks, in part, to major improvements in battery technology, electric vehicles are having their day in the sun. Later this year, GM will begin selling the Chevrolet Volt, a plug-in hybrid, and Nissan will begin selling the Leaf, an allelectric passenger car with a 100-mile range. In May, Tesla Motors purchased a former Toyota plant in Fremont, Calif., to begin manufacturing its all-electric Model S sedans. Many countries are looking toward electric vehicles for the benefits they offer in terms of energy security and the environment. Cutting the demand for gasoline would help reduce dependence on imported oil, shifting that demand to domestic electricity production. Whether electric vehicles will help reduce greenhouse gases depends on where their electric power comes from—fossil fuels or renewable sources—a mix that varies from one country to another. What will it take to get widespread adoption of plug-in hybrids and all-electric cars? For consumers, battery-powered cars need to have a range long enough to accommodate the average commute, reasonable recharging time, and affordable cost. Continued improvements in battery technology, as well as development of an infrastructure of recharging stations, are crucial to satisfy all these demands. Specific energy
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Specific energy Specific power
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Today’s hybrids, such as the Toyota Prius, use nickel-metal hydride batteries, but the cars now emerging feature lithiumion ones. The transition to lithium-ion has been driven by the differences in power needs between hybrids and plug-in hybrids. Hybrid electric vehicles (HEVs) are propelled by both an internal combustion engine and a battery that is used as a power assist; it kicks in when the engine is least efficient, such as during idling or acceleration and deceleration. Because the battery gets recharged by regenerative braking, the driver only needs to refill the gas tank, just as with a traditional car. In a plug-in hybrid (PHEV), such as the Chevrolet Volt, the battery powers the drive train, while the internal combustion engine serves as a backup in case the battery gets depleted on the road. The driver plugs in the car to recharge the battery, a process that can take several hours. All-electric vehicles, also known as battery electric vehicles (BEVs), such as the Nissan Leaf, operate purely on a battery charge. Lithium-ion batteries, now ubiquitous in po
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