Coating could lead to commercial lithium-metal batteries

Scientists at Stanford University and the U.S. Department of Energy’s SLAC National Accelerator Laboratory in California have developed a coating for lithium metal batteries which they say could overcome safety and performance issues that hold back the promising technology.

Lithium metal batteries could offer far better energy density and much lower weight than current lithium-ion technology as they replace heavier graphite with lithium metal as the anode material. However, lithium metals don’t work well with conventional electrolytes, leaving scientists searching for a way to improve low efficiency and mitigate serious safety concerns to enable the technology to shine.

While other approaches have relied on engineering the electrolyte to be compatible with lithium metal, the Stanford researchers chose to focus on the lithium metal itself. They developed a coating that delivers lithium ions to the electrode uniformly, reducing the formation of dendrites and performance-damaging chemical buildup on the anode.

Solution processed coating

The coating, described in a paper published in the journal Joule, is solution processed and applied to the lithium metal anode. The anode was then combined with other commercially available components to create an operational battery. In the device, the coating was found to “simultaneously hinder electrolyte penetration, mitigate side reactions between Li [lithium] and electrolyte, maintain low interfacial impedance and allow homogenous Li deposition”, according to the summary of the paper published in Joule.

The battery maintained 85% of its initial power after 160 cycles. Though that is far lower than the figure for conventional li-ion batteries, the Stanford group noted, ‘regular’ lithium metal battery cells can only deliver around 30% after 160 cycles – the ones that haven’t exploded, that is.

“Our new coating design makes lithium metal batteries stable and promising for further development,” said Stanford Ph.D. student Zhiao Yu.

The group will now focus on refining design of the coating to further increase capacity retention and increase the number of cycles in battery testing.

“While use in electric vehicles may be the ultimate goal,” said Yi Cui, professor of materials science and engineering and of photon science at SLAC, “commercialization would likely start with consumer electronics, to demonstrate the battery’s safety.”