UCLA researchers developed a way to deposit lithium metal onto a surface while avoiding a layer of corrosion that usually forms. Without that corrosion, the metal takes a previously unseen form, a tiny 12-sided figure. Credit: Li Lab/UCLA
Key points:
- In tests, researchers have revealed the true shape of lithium for the first time.
- With their new technique, lithium formed miniscule dodecahedrons.
- The discovery suggests the explosion risk for lithium-metal batteries can be abated, and leads to the possibility of better, safer rechargeable batteries.
A study by researchers at the California NanoSystems Institute at UCLA has revealed a fundamental discovery that could lead to safer lithium-metal batteries that outperform today’s lithium-ion batteries.
Metallic lithium reacts so easily with chemicals that, under normal conditions, corrosion forms almost immediately while the metal is being laid down on a surface such as an electrode. But the UCLA investigators developed a technique that prevents that corrosion and showed that, in its absence, lithium atoms assemble into a surprising shape—the rhombic dodecahedron, a 12-sided figure similar to the dice used in role-playing games like Dungeons and Dragons.
The new technique deposits lithium faster than corrosion can form. In their study, the scientists ran current through a smaller-than-usual electrode in order to push electricity out faster. A balance was required, however, because speeding up the process too much would lead to the same spiky structures that cause short circuits; so the researchers adjusted the shape of their tiny electrode.
They then laid down lithium on surfaces using four different electrolytes, comparing results between a standard technique and their new method. With corrosion, the lithium formed four distinct microscopic shapes. However, with the corrosion-free process, the team found that the lithium formed miniscule dodecahedrons—no bigger than 2 millionths of a meter, or about the average length of a single bacterium—in all four cases.
The revelation of the true shape of lithium—that is, in the absence of corrosion—suggests that the explosion risk for lithium-metal batteries can be abated, because the atoms accumulate in an orderly form instead of one that can crisscross. The discovery could also have substantial implications for high-performance energy technology.
“Scientists and engineers have produced over two decades’ worth of research into synthesizing metals including gold, platinum and silver into shapes such as nanocubes, nanospheres and nanorods,” said Yuzhang Li, the study’s corresponding author and assistant professor of chemical and biomolecular engineering at UCLA. “Now that we know the shape of lithium, the question is, ‘can we tune it so that it forms cubes, which can be packed in densely to increase both the safety and performance of batteries?’”