Scientists have revealed that the new generation of batteries could get higher lifespan with the help of their new imaging technique. Developed by researchers from UCLA, the technique allows for high-resolution imaging of lithium-metal batteries while they charge.
They underlined that measuring a corrosion layer that forms on lithium offered clues for better battery design, and the imaging technique may have uses in other fields, such as biology.
Researchers also pointed out that lithium-metal batteries could hold double the energy compared to today’s lithium-ion batteries, but they currently have a much shorter lifespan.
The technique captures a lithium-metal battery as it charges, at a level of detail smaller than the wavelength of light.
Called electrified cryogenic electron microscopy, or eCryoEM for short, the method yielded insights that may help guide the design of better lithium-metal batteries.
Researchers revealed that cryoEM tools for physical sciences are no different from the ones in biology. For batteries, they’re basically postmortem techniques.
“We can only capture electrochemical reactions in their initial and final states. There’s a blind spot for what’s happening under reaction conditions,” said researchers.
“In this technique we’ve been developing over the last four years, we said: let’s throw a battery in liquid nitrogen while it’s charging. In order to do that, we had to engineer a very thin battery, and we had to plunge freeze it directly so that it freezes very fast, on the order of milliseconds. We had to ensure that there were no side reactions during that process.”
They froze batteries at various time points.
“When we bring together many of these measurements in sequence, it becomes a bit like a flipbook animation where we watch that corrosion film grow over time. And if we understand that, it’ll help us engineer better batteries,” added researchers.
Key to boost battery life
Using eCryoEM, researchers plotted the thickness of the corrosion layer over time. At early stages, the growth rate is only limited by how fast the lithium can react. Once the corrosion film gets thick enough, growth is limited by how quickly the electrons diffuse through it.
It turns out that during the diffusion-limited stage, the corrosion film does grow slower with the high-performing electrolyte, but only by about 10%. During the early, reaction-limited stage, there’s a much larger difference, by a factor of three. That was a bit of a surprise, revealed researchers in a press release.
Lithium metal could give the United States some potential to leapfrog lithium-ion batteries. Compared to lithium-ion, lithium metal essentially doubles battery’s energy density. However, the cycling stability of lithium metal is just not there yet.
Researchers have been focusing on engineering the properties of the corrosion layer to limit diffusion. But the major difference doesn’t seem to be how fast electrons go through; it’s how reactive the electrolyte is.
The findings suggest we should dedicate some engineering to making the liquid electrolyte as inert as possible. This is not a novel concept, but the study quantifies just how large a difference that could make and highlights this is a potentially promising approach, according to researchers.
