One of the most crucial materials in current electric vehicles could be getting a major upgrade. Researchers at Stanford University and SLAC National Accelerator Laboratory have developed a coating that could make a long-held idea, the rechargeable lithium metal battery, a reality.
A lithium metal battery has potential to surpass the commonly known lithium ion battery in any number of ways. If a battery uses lightweight lithium instead of heavier graphite, it could hold at least a third more power per pound than a lithium-ion battery and would be significantly lighter.
Lithium metal batteries would have a number of uses, from smartphones to electric cars, if they could just stop doing one thing during lab testing: exploding into a fiery blaze.
“The capacity of conventional lithium ion batteries has been developed almost as far as it can go,” says Stanford Ph.D. student David Mackanic, the study’s coauthor, in a press statement. “So, it’s crucial to develop new kinds of batteries to fulfill the aggressive energy density requirements of modern electronic devices.”
That means putting a stop to the explosions.
The Stanford/SLAC team has addressed that issue through limiting what are known as dendrites. In a car battery, these are “tiny needlelike structures” that pierce the separator, which isolates the battery’s cathode and anode and resides between its positive and negative sides. When these dendrites form, they’re a problem in lithium metal batteries. Namely, they can short circuit within a battery’s flammable liquid.
Limiting dendrites is a huge step forward, the team says.
“We’re addressing the holy grail of lithium metal batteries,” says Zhenan Bao, a professor of chemical engineering, who is senior author of the paper along with Yi Cui, professor of materials science and engineering and photon science at SLAC.
The team tested its coating on a lithium metal battery’s anode, or its positively charged end, which is where the troublesome dendrites form.
“After 160 cycles, their lithium metal cells still delivered 85 percent of the power that they did in their first cycle,” reads the press statement. “Regular lithium metal cells deliver about 30 percent after that many cycles, rendering them nearly useless even if they don’t explode.”
The coating prevents dendrites from even forming in the first place by preventing unwanted chemical reactions and reducing chemical buildup on the anode.
“Our new coating design makes lithium metal batteries stable and promising for further development,” says the study’s other coauthor, Stanford Ph.D. student Zhiao Yu.
Many are starting to look past lithium ion batteries, in hopes of finding battery materials that would be less wasteful and more environmentally conscious. Some scientists, in fact, are looking past the material entirely and building batteries with iron.
