UCLA researchers have developed a way to create lithium-metal batteries by depositing metal onto a surface while avoiding the layer of corrosion that usually forms.
The researchers developed a technique that prevents that corrosion and showed that, in its absence, lithium atoms assemble into an unexpected rhombic dodecahedron shape - a 12-sided figure similar to the dice used in role-playing games like Dungeons and Dragons.
The lithium-metal battery historically hasn't been developed or adopted as broadly as lithium-ion - while they can potentially generate double the energy, they also present a far greater risk of catching fire or even exploding.
Shape-shifting
"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, an assistant professor of chemical and biomolecular engineering at the UCLA Samueli School of Engineering and a member of CNSI. "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?"
A rendering of the rhombic dodecahedron shape that lithium atoms formed on a surface with the researchers' technique for avoiding corrosion
The UCLA team said that their new process for laying down the lithium coating uses electrolytes to stop microscopic branching filaments with protruding spikes called dendrites from crisscrossing and causing a short circuit that could lead to an explosion.
If dendrites bridge the gap between the anode and cathode, they can create a direct electrical connection within the battery cell, causing a short circuit. As dendrites grow and consume lithium from the anode, they can also reduce the available lithium for reversible reactions during charging and discharging cycles. This can result in decreased battery capacity and performance.
The revelation of finding the shape of lithium could be a important part of reducing 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 researchers ran current through a much smaller electrode in order to push electricity out faster — describing it as similar to how partially blocking the nozzle of a garden hose causes water to shoot out more forcefully.
Mineral impact
Should the research grow into commercial applications, it could have a major impact on the mineral supply balance for lithium batteries.
Unlike lithium-ion, lithium-metal batteries, in their most basic form, do not necessarily require cobalt, nickel, manganese, or iron as part of their anode or cathode materials.
Unlike lithium-ion batteries, which typically use these metals in various cathode compositions, lithium-metal batteries focus on the use of lithium metal as the anode material.
The challenge to the traditional dominance of lithium-ion comes after Japanese carmaker Toyota announced earlier this year that it could make a solid-state battery with several weight, cost and safety advantages over traditional lithium-ion versions.
Toyota's breakthrough in solid-state battery technology also has the potential to significantly impact the demand for various minerals used in conventional lithium-ion batteries, and therefore miners working on those projects.
Solid-state batteries typically replace a liquid electrolyte with a solid one and use lithium metal at the anode instead of graphite, the current standard in lithium-ion batteries.
