Lithium-ion batteries are ubiquitous today, but our future, especially our automotive future, will need a different battery, one that has greater energy density, lower cost and is less prone to overheating.
In the worldwide scramble to find an alternative to the lithium-ion battery, one group of researchers at the Lawrence Berkeley National Laboratory, a division of the U.S. Department of Energy (DOE), has focused on magnesium.
The Berkeley Labs scientists believe magnesium is promising alternative because it’s based on what’s known as a “multivalent ion.” Lithium-ion (Li-ion) has a charge of +1, meaning it has only a single electron for an electrical current. Magnesium-ion (Mg-ion) has a charge of +2.
In theory, at least, that means Mg-ions can provide twice as much electrical current as Li-ions when used in the same density. The use of Mg-ion batteries also would be less expensive and safer than Li-ion batteries because magnesium is more plentiful than lithium and is less prone to overheating.
Still, the Mg-ion batteries, with their multivalent ions, have drawbacks that so far have stalled their development. The key term here, though, is “so far.” Scientists at a Berkeley Lab research center have run computer simulations that have clarified science’s understanding about the Mg-ions in the electrolyte that conducts the ions between the electrodes of the battery.
Their research was published in the Journal of the American Chemical Society.
According to one of the scientists involved in the research, David Prendergast, it was believed that an increased charge causes Mg-ions to be surrounded by oppositely charged ions and other matter that can slow their conductivity and reduce a battery’s efficiency. “However,” Prendergast tells the Berkeley Lab’s News Center, we found the problem may be less dire than is widely believed.”
What is widely believed is that a Mg-ion would be surrounded by a cluster of its six nearest neighbors including the oppositely charged ions, or “counter ions,” or by solvent molecules. This cluster of matter around the Mg-ion, called a “coordination sphere,” would make the Mg-ion too bulky to be conducted efficiently.
But Prendergast and a colleague, Liwen Wan, ran simulations of Mg-ion conductivity on two supercomputers and found that only four neighboring particles cluster around the Mg-ion. Prendergast says this makes conductivity more efficient because the coordination sphere is one-third smaller.
“Our findings also suggest that the performance bottlenecks experienced with Mg-ion batteries to date may not be so much related to the electrolyte itself, but to what happens at the interface between the electrolyte and electrodes as the Mg-ions shed their coordination spheres.”
Now that Prendergast and Wan have cleared away the underbrush, the next step is to move beyond computer simulations to real-world testing. If that holds up, cars powered by powerful, safe and inexpensive Mg-ion batteries can’t be far behind.
By Andy Tully of Oilprice.com
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Andy Tully is a veteran news reporter who is now the news editor for Oilprice.com