10-minute EV charging? There’s a battery for that

Source: By Carlos Anchondo, E&E News reporter • Posted: Thursday, October 31, 2019

A new battery design could make it possible for electric vehicle drivers to eventually charge their cars and get back on the road in as little as 10 minutes, according to study from Pennsylvania State University engineers.

Published this week in Joule, the research supported by the Department of Energy said the new model gives drivers up to 300 miles on a 10-minute charge, a fraction of the time it now takes EV owners to repower.

Researchers found that if they heated batteries up to 140 degrees Fahrenheit for 10 minutes, then rapidly cooled them to ambient temperatures, they could avoid performance loss usually created from the buildup of lithium deposits, also known as lithium plating.

The method aims to circumvent battery degradation that happens from long periods of high heat. Chao-Yang Wang, a mechanical engineering professor at Penn State and paper co-author, said the rapid cooling of the battery would be accomplished using the cooling system designed into a car.

“Fast charging is the key to enabling wide spread introduction of electric vehicles,” said Wang, pointing to the chilling effect range anxiety has on the greater adoption of EVs, in a release.

Electric vehicles will only be “truly competitive” with traditional vehicles when they can be charged as fast as refilling a gas tank, according to the study. The researchers’ approach to battery charging uses industrially available battery materials to retain nearly 92% capacity after 2,500 extreme, fast-charging cycles.

That exceeds a target set by the Department of Energy of 500 cycles at a 20% loss, the paper noted.

Xiao-Guang Yang, co-author and assistant research professor at Penn State, said cars would require their self-heating lithium-ion battery (SHLB) structure. The battery uses a thin nickel foil inside the battery cell to act as an internal heater. The addition of the foil only increases the cell weight by 1.3%, Yang said.

“This SHLB has already been commercialized and demonstrated to be viable for mass production,” Yang said via email.

Yang said charging a battery at a high temperature is a benefit as long as the time of exposure is limited to 60 degrees Celsius, or 140 degrees Fahrenheit. Yang said their approach only operates the battery at that temperature for seven days out of 14.8 years, or 0.1%, of the lifetime of an EV.

“We believe that this is a revolutionary approach and completely changed the conventional wisdom regarding the optimal temperature for lithium-ion battery operation,” Yang said.

For the first time, he said, their research approach makes the charging of EVs “truly weather- and region-independent.”

A viable idea?

As with any technology, uncertainty remains about whether it can be viable outside of a lab and at a larger scale. When designs are scaled up, inefficiencies and higher costs can emerge.

Zach Needell, an engineer at the Lawrence Berkeley National Laboratory who has previously written about the potential for widespread electrification of personal vehicles across the United States, said our intuition as to what factors make a car a “good investment” are often driven by past experiences with conventional vehicles.

Those factors don’t necessarily carry over to newer technology like EVs, he said.

“Factors like battery durability in different weather conditions aren’t all captured in high line statistics like battery capacity, vehicle range, and expected fuel economy, but they can have a big impact on how useful and cost effective EVs are to real people,” Needell said via email.

He said work like the Penn State research is an “important step” to making EV technology more accessible and cost effective to a wider market of car owners.

“Understanding (and solving) EV-specific challenges like this is an important step in bringing EV technology from a niche segment of the market to more widespread use,” Needell said.

Marc Geller, media relations director at the Electric Auto Association, said he welcomes any effort to make electric vehicle charging faster and more secure. However, the end goal should not be to replicate the gas station model for 100% of individuals with plug-in cars, he said, as that would ignore the benefits of charging at homes or workplaces.

“The electric grid benefits from electric cars charging at relatively slow rates,” Geller said. “It’s much less disruptive to the grid.”

Geller said that for people who don’t have the ability to charge at home, such as those who live in apartments without electricity access in their garage, they would benefit from a gas station model for charging. But it would be less convenient and more expensive for those with the ability to charge their car at home, even with faster refueling.

Extreme fast charging could be more important for heavy-duty trucks or battery-based electric buses, he said, which potentially have 24-hour duty cycles. The ability to rapidly recharge without battery degradation or other problems associated with direct current charging would be “really great” for those kinds of vehicles, Geller said.

Joel Levin, executive director of Plug In America, also said that the majority of EV charging happens at home overnight or at work during the day. Levin said the charging technology that exists today should be sufficient for most EV drivers.

“That said, if XFC [extreme fast charging] can be done safely, it would be a benefit for EV drivers, particularly for those who do not have access to charging at home or work or on long road trips,” Levin said via email.

Genevieve Cullen, president of the Electric Drive Transportation Association, said while her organization had not seen this particular research, technology advances in battery and charging systems are absolutely speeding up the adoption of electric transportation.

“Public and private investment in electric mobility research and development are of critical importance to ensure that the U.S. continues to lead in the global technology race,” Cullen said, “and that U.S. consumers have increasing choice for driving electric.”