Batteries lose capability over time, which is why older cellphones run out of power more quickly. This common phenomenon, nonetheless, is just not completely understood.
Now, a global team of researchers, led by an engineer on the University of Colorado Boulder, has revealed the underlying mechanism behind such battery degradation. Their discovery could help scientists to develop higher batteries, which might allow electric vehicles to run farther and last more, while also advancing energy storage technologies that may speed up the transition to wash energy.
The findings were published September 12 within the journal Science.
“We’re helping to advance lithium-ion batteries by determining the molecular level processes involved of their degradation,” said Michael Toney, the paper’s corresponding writer and a professor within the Department of Chemical and Biological Engineering. “Having a greater battery could be very necessary in shifting our energy infrastructure away from fossil fuels to more renewable energy sources.”
Engineers have been working for years on designing lithium-ion batteries — probably the most common style of rechargeable batteries — without cobalt. Cobalt is an expensive rare mineral, and its mining process has been linked to grave environmental and human rights concerns. Within the Democratic Republic of Congo, which supplies greater than half of the world’s cobalt, many miners are children.
Up to now, scientists have tried to make use of other elements comparable to nickel and magnesium to switch cobalt in lithium-ion batteries. But these batteries have even higher rates of self-discharge, which is when the battery’s internal chemical reactions reduce stored energy and degrade its capability over time. Due to self-discharge, most EV batteries have a lifespan of seven to 10 years before they should be replaced.
Toney, who can be a fellow of the Renewable and Sustainable Energy Institute, and his team set out to analyze the explanation for self-discharge. In a typical lithium-ion battery, lithium ions, which carry charges, move from one side of the battery, called the anode, to the opposite side, called the cathode, through a medium called an electrolyte. During this process, the flow of those charged ions forms an electrical current that powers electronic devices. Charging the battery reverses the flow of the charged ions and returns them to the anode.
Previously, scientists thought batteries self-discharge because not all lithium ions return to the anode when charging, reducing the variety of charged ions available to form the present and supply power.
Using the Advanced Photon Source, a strong X-ray machine, on the U.S. Department of Energy’s Argonne National Laboratory in Illinois, the research team discovered that hydrogen molecules from the battery’s electrolyte would move to cathode and take the spots that lithium ions normally bind to. Because of this, lithium ions have fewer places to bind to on the cathode, weakening the electrical current and decreasing the battery’s capability.
Transportation is the only largest source of greenhouse gases generated within the U.S, accounting for 28% of the country’s emissions in 2021. In an effort to scale back emissions, many automakers have committed to moving away from developing gasoline cars to supply more EVs as a substitute. But EV manufacturers face a bunch of challenges, including limited driving range, higher production costs and shorter battery lifespan than conventional vehicles. Within the U.S. market, a typical all-electric automobile can run about 250 miles in a single charge, about 60% that of a gasoline automobile. The brand new study has the potential to deal with all of those issues, Toney said.
“All consumers want cars with a big driving range. A few of these low cobalt-containing batteries can potentially provide a better driving range, but we also have to be certain that they do not collapse in a brief time period,” he said, noting that reducing cobalt also can reduce costs and address human rights and energy justice concerns.
With a greater understanding of the self-discharge mechanism, engineers can explore a couple of ways to forestall the method, comparable to coating the cathode with a special material to dam hydrogen molecules or using a distinct electrolyte.
“Now that we understand what’s causing batteries to degrade, we are able to inform the battery chemistry community on what must be improved when designing in batteries,” Toney said.
