Researchers at the U.S. Department of Energy’s (DOE) Argonne National Laboratory have reported a new way to speed up the charging of lithium-ion batteries for electric vehicles.

Basically, batteries have two kinds of electrodes: one that is positively charged (cathode), and one that is negatively charged (anode). This fast charging works by exposing the positively charged part of the battery (cathode) to a beam of concentrated light. For example, the white light from a special type of lamp called a ​“xenon lamp” speeds up the charging so that it is two times faster! If commercialized, such technology could be a game changer for electric vehicles.

Owners of electric vehicles experience ​“range anxiety”, meaning they worry that the vehicle won’t make it to its destination when the charge level runs low or the location of the closest charging station seems too distant. This is similar to how we may feel when we see our phone battery charge decreasing, and we are not near our charger. Fast charging remains a critical challenge if such vehicles are ever to capture a large part of the transportation market. Charging an electric car on empty typically takes about eight hours.

“We wanted to greatly shorten this charge reaction without damaging the electrodes from the resulting higher current flow.” — Christopher Johnson, Argonne Distinguished Fellow

Special supercharging stations now exist that achieve ultrafast charging of electric vehicles by delivering a much higher current to the battery. Passing too much current over too short a time, however, degrades battery performance.

Typically, lithium-ion batteries for vehicles are slowly charged to obtain a complete electrochemical reaction.

“We wanted to greatly shorten this charge reaction without damaging the electrodes from the resulting higher current flow,” said Christopher Johnson, Argonne Distinguished Fellow and group leader in the Chemical Sciences and Engineering division.

Today’s lithium-ion batteries get no exposure to light, with the electrodes surrounded by darkness inside the battery case. Argonne’s photo-assisted technology would use a transparent container that lets concentrated light illuminate the battery electrodes during charging.

To investigate the charge process, the research team made small lithium-ion cells (“coin cells”) with transparent quartz windows. They then tested these cells with and without white light shining through the window onto the cathode.

​“We hypothesized that, during charging, white light would interact favorably with the typical cathode material, and that proved to be the case in our cell tests,” Johnson said. The cathode material tested was a lithium manganese oxide, abbreviated as LiMn₂O₄ (LMO).

The key ingredient in this favorable reaction is the interaction of LMO with light. LMO is a semiconductor (a material that under certain conditions can enable a charge flow), and it is known to interact with light. While absorbing particles of light called photons during charging, the element manganese in the LMO changes its charge state from Mn³⁺ to Mn⁴⁺. In response, lithium ions leave the cathode faster than would happen without the interaction of LMO and light.

This condition drives the battery reaction faster. The team found that the faster reaction resulted in faster charging without damaging battery performance or cycle life. ​“Our cell tests showed a factor of two decrease in charging time with the light turned on,” Johnson said. In other words, charge time was two times faster.

The research team performed this work as part of the former Center for Electrochemical Energy Science (CEES), a DOE Energy Frontier Research Center (EFRC) led by Argonne. 

“This research is a great example of how CEES’s goal of understanding the electrode processes in lithium-ion batteries enabled pivotal advances that influence technology,” said Paul Fenter, former CEES Director and current senior physicist in the Chemical Sciences and Engineering division. ​“This is a great example of the transformational impacts that the EFRC program can achieve.”

Johnson added that, ​“This finding is the first of its kind whereby light and battery technologies are merged, and this intersection bodes well for the future of innovative charging concepts for batteries.”

The Vehicle Technologies Office of the DOE Office of Energy Efficiency and Renewable Energy has identified fast charge as a critical challenge in ensuring mass adoption of electric vehicles with a goal of 15-min. recharge times, and this research could be a key to making this possible.

This research appeared in Nature Communications, titled ​“Photo-accelerated fast charging of lithium-ion batteries.” In addition to Johnson, other Argonne contributors are Anna Lee, Márton Vörös, Wesley M. Dose, Jens Niklas, Oleg Poluektov, Richard D. Schaller, Hakim Iddir, Victor A. Maroni, Eungje Lee, Brian Ingram, and Larry A. Curtiss.

This research was funded by the DOE Office of Basic Energy Sciences and performed, in part, at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility.

Original article published on October 30, 2019

About Argonne’s Center for Nanoscale Materials
The Center for Nanoscale Materials is one of the five DOE Nanoscale Science Research Centers, premier national user facilities for interdisciplinary research at the nanoscale supported by the DOE Office of Science. Together the NSRCs comprise a suite of complementary facilities that provide researchers with state-of-the-art capabilities to fabricate, process, characterize and model nanoscale materials, and constitute the largest infrastructure investment of the National Nanotechnology Initiative. The NSRCs are located at DOE’s Argonne, Brookhaven, Lawrence Berkeley, Oak Ridge, Sandia and Los Alamos National Laboratories. For more information about the DOE NSRCs, please visit https://​sci​ence​.osti​.gov/​U​s​e​r​-​F​a​c​i​l​i​t​i​e​s​/​U​s​e​r​-​F​a​c​i​l​i​t​i​e​s​-​a​t​-​a​-​G​lance.

Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America’s scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science.

The U.S. Department of Energy’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit https://​ener​gy​.gov/​s​c​ience.