Cornell researchers have uncovered the source of a persistent problem
limiting the durability of sodium-ion batteries, providing manufacturers
with new strategies for powering the 21st century.
Sodium-ion batteries are a promising technology for electric vehicles, the
energy grid and other applications because they are made from abundant
materials that are energy dense, nonflammable and operate well in colder
temperatures. But engineers have yet to perfect the chemistry. While the
lithium-ion batteries found in modern electronics can recharge thousands of
times, most variations of sodium-ion batteries can only cycle a small
fraction of that.
The poor durability stems from a specific atomic reshuffling in the
battery's operation—the P2-O2 phase transition—as ions traveling through the
battery disorder crystal structures and eventually break them. While the
phase transition has been of interest to researchers, the mechanisms behind
it have been difficult to study, especially during battery operation.
Key aspects of that mechanism have been revealed by a Cornell team from the
lab of Andrej Singer, assistant professor of materials science and
engineering, and were published Feb. 1 in the journal Advanced Energy
Materials. Doctoral student Jason Huang is the lead author.
The team found that as sodium ions move through the battery, the
misorientation of crystal layers inside individual particles increases
before the layers suddenly align just prior to the P2-O2 phase transition.
"We've discovered a new critical mechanism," Singer said. "During battery
charge, the atoms suddenly realign and facilitate that flawed phase
transformation."
The team was able to observe the phenomenon after developing a new X-ray
imaging technique using the Cornell High Energy Synchrotron Source, which
allowed them to observe, in real time and in mass scale, the behavior of
single particles within their battery sample.
"The unexpected atomic alignment is invisible in conventional powder X-ray
diffraction measurements as it requires seeing inside individual cathode
nanoparticles," Singer said. "Our unprecedented high-throughput data allowed
us to reveal the subtle, yet critical, mechanism."
The finding led the team to propose new design options for the type of
sodium-ion battery they were using, which they plan to investigate in future
research projects. One solution is to modify the battery chemistry to
introduce a strategic disorder to the particles just before the flawed
transition phase, according to Huang.
"By changing the ratios of our transition metals, in this case, nickel and
manganese," Huang said, "we can introduce a bit of disorder and potentially
reduce the ordering effect we observed."
Huang said the new characterization technique can be used to reveal complex
phase behaviors in other nanoparticle systems, but its best application may
remain in next-generation energy storage technologies.
"We're pushing the frontiers of sodium-ion batteries and what we know about
them," said Huang, "and using this knowledge to design better batteries will
help to unlock the technology for practical applications in the future."
Reference:
Jason J. Huang et al, Disorder Dynamics in Battery Nanoparticles During
Phase Transitions Revealed by Operando Single‐Particle Diffraction, Advanced
Energy Materials (2022).
DOI: 10.1002/aenm.202103521
Tags:
Electronics