It took a while to catch on, of course, but we were all well on our way to taking our freedom from the cord for granted ever since the first legitimate battery stored electricity through a chemical reaction in 1800. By the time most of us grew up, we were familiar with batteries as the mundane devices that allowed us to take our music and games with us (though they were never included!). Now, they allow us to do everything from vacuum our floors and manicure our lawns to drive ourselves to work. As tech has evolved, instead of being chained to a cord, we have become chained to chargers and replacement batteries.
Those shortcomings – charging times and durability – are often seen as barriers to wider adoption of fully electric tech. As someone who lives in the Colorado mountains, where there’s at least a 30-minute drive to nearly any activity, plus the strong likelihood of cold weather, driving an electric car on longer trips seems sketchy at best. But scientists are looking to improve both shortcomings with new and innovative coatings on battery electrodes.
Current lithium-ion (Li) EV batteries store and release power by moving lithium ions back and forth between electrodes via a liquid electrolyte. In cold temperatures, this movement slows, reducing battery power and charging rate. Automakers have increased the thickness of the electrodes they use in battery cells to extend the range, and while it’s worked for that purpose, it also makes some of the lithium hard to access, resulting in slower charging and less power for a given battery weight.
Stronger, Better, Faster
Researchers at the University of Michigan have learned how to charge electric vehicles five times faster in subfreezing temperatures. Their first solution to the problem included drilling channels through an anode, the electrode that receives lithium ions during charging. When I read it, I thought, “that sounds an awful lot like fracturing.”
University of Michigan Associate Professor of Mechanical Engineering and Materials Science and Engineering Neil Dasgupta and his team improved battery charging capability by creating pathways – roughly 40 microns in size – in the anode. Drilling through the graphite by blasting it with lasers (see the fracturing connection here?) enabled the lithium ions to find places to lodge faster, even deep within the electrode, ensuring more uniform charging.
Cold charging was still inefficient, and the team identified the problem as the chemical layer that forms on the surface of the electrode from reacting with the electrolyte.
“Charging 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,” Dasgupta said. The team prevented this layer from forming by coating the battery with lithium borate-carbonate, approximately 20 nanometers thick. Adding this coating sped up cold charging significantly, and when combined with the channels, the team’s test cells charged 500-percent faster in subfreezing temperatures than a normal battery.
While this research addresses charging, it doesn’t quite get at durability. EV batteries undergo constant charge and discharge cycles to power vehicles efficiently, and the charging and discharging process causes the battery’s positive active materials to expand and contract repeatedly, leading to microscopic cracks that degrade efficiency.
Researchers from the Graduate Institute of Ferrous & Eco Materials Technology, Department of Materials Science and Engineering, POSTECH, teamed up with Samsung SDI, Northwestern University and Chung-Ang University to develop a more effective solution in the form of a nano-spring coating technology.
The coating essentially creates elastic structures. By absorbing strain energy during charging and discharging, this technology prevents cracks and other wear and tear, ensuring stronger, more resilient batteries while simultaneously improving lifespan and performance. According to the researchers, the technology minimizes resistance from material volume changes using just 0.5 weight percentage of conductive material.
Additionally, it achieves a high energy density of more than 570 Watt-hours per kilogram and demonstrates exceptional longevity, retaining 78 percent of its initial capacity after 1,000 charge-discharge cycles. Kyu-Young Park, assistant professor at the Graduate Institute of Ferrous & Eco Materials Technology, Department of Materials Science and Engineering, POSTECH, believes the innovation could play a great role in accelerating the global shift toward reliable, high-performance electric mobility, as the demand for sustainable energy solutions continues to grow.