Improving energy storage technology is widely recognized as essential to the viability of battery electric vehicles (BEVs), therefore a core technology for dramatically reducing transportation greenhouse gas emissions. But the impact of charging technology on developing a better battery is often overlooked. Senior Editor for MIT Technology Review Kevin Bullis put this in perspective, noting that “fast-charging still takes far longer than it does to fill up a tank of gas.”
The ITIF report Shifting Gears: Transcending Conventional Economic Doctrines to Develop Better Electric Vehicle Batteries summarizes the conventional state of BEV charging technology:
While Level 1 charging is available for all BEV vehicles, it can take up to 20 hours to fully recharge a vehicle. Level 2, meanwhile, charges in around 8 hours, making it ideal for overnight charging… Level 3 charging can almost fully replenish a BEV’s battery in half an hour, but the high-voltage process can shorten its lifespan due to its low density.
Unfortunately, even the relatively fast – by BEV standards – half an hour-level 3 charging offers a poor alternative to gas cars, which can be refueled in less than five minutes, at a much higher cost.
The underlying problem is technological and linked to the nature of the conventional lithium-ion BEV batteries used today. As Yale Environment 360 reports:
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Lithium-ion batteries are charged by moving charged particles from a cathode to an anode; pushing those ions into the anode takes time, and forcing them in faster heats up the battery and causes efficiency losses. And if you push too hard, lithium ions may build up in metallic form on the surface of the anode, a phenomenon known as plating, which can drastically shorten a battery’s lifespan. Even without plating, the effects of rapid charging might drop a battery’s life from thousands of cycles down into the hundreds.
It’s unsurprising then that the Advanced Research Projects Agency-Energy (ARPA-E), the Department of Energy’s far-reaching high-risk energy research arm, recently invested in a number of BEV battery projects with an eye towards better charging capabilities. On November 28, ARPA-E unveiled the recipients of $130 million in funding for their “OPEN 2012” program. The 66 awardees cover a wide array of technology areas and including out-of-the-box ideas like energy-dense beets and carbon-dioxide fuel conversion. And 3 of the grants are specifically for projects that could reduce BEV-charging times.
One of the ARPA-E grant recipients, Vorbeck Materials, is working to develop a lithium-sulfur battery for electric vehicles, in lieu of the conventional lithium-ion battery. The unusual battery chemistry promises to reduce internal resistance to ion flow. “If successful,” Business Wire observes, “the system has the potential to shorten recharge times by factor of three [emphasis added], maintain high battery capacity and increase the efficiency of hybrid vehicles by up to 20% while also reducing cost and emissions.”
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Two other OPEN 2012 awardees are foregoing experimenting with lithium-based batteries altogether. Researchers at the Georgia Institute of Technology and the University of California at Santa Barbara, respectively, received ARPA-E grants to develop high-performance capacitors. “Capacitors,” the Santa Barbara Independent notes, “are superior to traditional batteries in recharge time and frequency; they also are better suited to deliver a sudden surge of power. But the big downside of capacitors is that they can’t store nearly as much electricity as lithium ion batteries. What limits the energy volume of a capacitor — as opposed to a battery — is surface area.” If researchers are able to increase capacitor energy density and successfully adapt them for use as an energy storage device in electric vehicles, the article goes on to say, they could reduce BEV charge time “down to a few minutes”.
Of course, work also continues on enabling standard lithium-ion batteries to be charged faster as well. For example, a round of ARPA-E funding earlier this year geared specifically towards energy storage projects awarded a consortium led by UC San Diego and Bosch Research and Technology Center more than $3 million to develop estimation algorithms technology for electric vehicle batteries. Engineers affiliated with the project, UC San Diego reported, had previously created estimation algorithms “that allow lithium-ion batteries to run more efficiently, potentially reducing their cost by 25 percent and potentially allowing the batteries to charge twice as fast as is currently possible. In one instance, electric batteries could be charged in just 15 minutes.”
Ultimately, it is hard to predict where the breakthroughs in electric vehicle-charging and batteries will come from, but it’s an area of aggressive and active research. If any of the aforementioned ARPA-E awardees are successful, at least one obstacle to BEV parity with gas cars would be erased and the world will be one step closer to a carbon free vehicle that consumers will actually want to buy and drive.
By. Matthew Stepp