University of Michigan engineers developed a modified manufacturing process for electric vehicle batteries\u2014using a stabilizing electrode coating and microscale channels\u2014that could enable high ranges and fast charging in cold weather, solving problems that are turning potential EV buyers away.<\/p>\n
\u201cWe envision this approach as something that EV battery manufacturers could adopt without major changes to existing factories,\u201d said Neil Dasgupta, U-M associate professor of mechanical engineering and materials science and engineering, and corresponding author of the study published in Joule<\/em>.<\/p>\n \u201cFor the first time, we\u2019ve shown a pathway to simultaneously achieve extreme fast charging at low temperatures, without sacrificing the energy density of the lithium-ion battery.\u201d<\/p>\n Lithium-ion EV batteries made this way can charge 500% faster at temperatures as low as 14 F (-10 C). The structure and coating demonstrated by the team prevented the formation of performance-hindering lithium plating on the battery\u2019s electrodes. As a result, batteries with these modifications keep 97% of their capacity even after being fast-charged 100 times at very cold temperatures.<\/p>\n Current EV batteries store and release power through the movement of lithium ions back and forth between electrodes via a liquid electrolyte. In cold temperatures, this movement of the ions slows, reducing both battery power as well as the charging rate.<\/p>\n To extend range, automakers have increased the thickness of the electrodes they use in battery cells. While that has allowed them to promise longer drives between charges, it makes some of the lithium hard to access, resulting in slower charging and less power for a given battery weight.<\/p>\n Previously, Dasgupta\u2019s team improved battery charging capability by creating pathways\u2014roughly 40 microns in size\u2014in the anode, the electrode that receives lithium ions during charging. Drilling through the graphite by blasting it with lasers enabled the lithium ions to find places to lodge faster, even deep within the electrode, ensuring more uniform charging.<\/p>\n This sped up room-temperature charging significantly, but cold charging was still inefficient. The team identified the problem: the chemical layer that forms on the surface of the electrode from reacting with the electrolyte. Dasgupta compares this behavior to butter: you can get a knife through it whether it\u2019s warm or cold, but it\u2019s a lot harder when it\u2019s cold. If you try to fast charge through that layer, lithium metal will build up on the anode like a traffic jam.<\/p>\n That plating prevents the entire electrode from being charged, once again reducing the battery\u2019s energy capacity. To prevent this surface layer from forming, they team coated the battery with a glassy material made of lithium borate-carbonate, approximately 20 nanometers thick. Adding this coating sped up cold charging significantly, and when combined with the channels, the team\u2019s test cells were 500% faster to charge in subfreezing temperatures.<\/p>\n \u201cBy the synergy between the 3-D architectures and artificial interface, this work can simultaneously address the trilemma of fast charging at low temperature for long-range driving,\u201d said Tae Cho, a recent Ph.D. graduate in mechanical engineering and first author of the study.<\/p>\n In the past two decades, EVs have become more commonplace on roadways as consumers look for better environmental options, but AAA survey results showed that the momentum is hard to maintain. From 2023 to 2024, the number of U.S. adults who would be \u201clikely\u201d or \u201cvery likely\u201d to buy a new or used EV dropped from 23% to 18%.<\/p>\n And 63% said they would be \u201cunlikely\u201d or \u201cvery unlikely\u201d to make an EV their next vehicle purchase. Part of the concerns are range drops over the winter, combined with slower charging, which was widely reported during the January 2024 cold snap.<\/p>\n \u201cCharging an EV battery takes 30 to 40 minutes even for aggressive fast charging, and that time increases to over an hour in the winter. This is the pain point we want to address,\u201d Dasgupta said.<\/p>\n <\/p>\n For more information:<\/p>\n University of Michigan<\/p>\n