The key to advancing lithium-ion battery technology requires a better
understanding of the dynamic processes in functioning materials under
realistic conditions. Imaging of lithium-ion dynamics during battery
operation requires sophisticated synchrotron X-ray or electron microscopy
techniques.
However, these techniques lend themselves to high-throughput material
screening. This limits rapid and rational materials improvements.
To study what’s happening inside a battery, the Cambridge team developed an
optical microscopy technique called interferometric scattering microscopy to
observe these processes at work. The technique help scientists determine the
speed-limiting processes, which, if addressed, could enable the batteries in
most smartphones and laptops to charge in as little as five minutes.
In addition, the technique could accelerate the development of
next-generation batteries.
Using the technique, scientists observed the charge-discharge cycle of
individual particles of lithium cobalt oxide. They did so by measuring the
amount of scattered light.
They were able to see the LCO going through a series of phase transitions in
the charge-discharge cycle. The phase boundaries within the LCO particles
move and change as lithium ions go in and out.
Scientists found that the mechanism of the moving boundary is different
depending on whether the battery is charging or discharging.
Dr. Akshay Rao from the Cavendish Laboratory, who led the research, said,
“We found that there are different speed limits for lithium-ion batteries,
depending on whether it’s charging or discharging. When charging, the speed
depends on how fast the lithium ions can pass through active material
particles. When discharging, the speed depends on how fast the ions are
inserted at the edges. So if we can control these two mechanisms, it would
enable lithium-ion batteries to charge much faster.”
“Given that lithium-ion batteries have been in use for decades, you’d think
we know everything there is to know about them, but that’s not the case.
This technique lets us see just how fast it might be able to go through a
charge-discharge cycle. What we’re looking forward to is using the technique
to study next-generation battery materials – we can use what we learned
about LCO to develop new materials.”
Professor Clare Grey, from Cambridge’s Yusuf Hamied Department of Chemistry,
who co-led the research, said, “The technique is a quite general way of
looking at ion dynamics in solid-state materials so that you can use it on
almost any type of battery material.”
“The high throughput nature of the methodology allows many particles to be
sampled across the entire electrode and, moving forward, will enable further
exploration of what happens when batteries fail and how to prevent it.”
“This lab-based technique we’ve developed offers a huge change in technology
speed so that we can keep up with the fast-moving inner workings of a
battery. The fact that we can see these phase boundaries changing in real
time was really surprising. This technique could be an important piece of
the puzzle in the development of next-generation batteries.”
Reference:
Alice J. Merryweather et al. ‘Operando optical tracking of single-particle
ion dynamics in batteries.’ Nature (2021). DOI:
10.1038/s41586-021-03584-2