Battery & Electrification Technology - November/December 2024 - 23

In contrast, the Chen team's cathode contains only iron (Fe)
and chlorine (Cl) - abundant, affordable, widely used elements
found in steel and table salt.
In their initial tests, FeCl3
was found to perform as well as
or better than the other, much more expensive cathodes. For
example, it has a higher operational voltage than the popularly
used cathode LiFePO4
(lithium iron phosphate, or LFP.
This technology may be less than five years from commercial
viability in EVs. For now, the team will continue investigating
FeCl3
and related materials, according to Chen. The work was led
by Chen and postdoc Zhantao Liu (the lead author of the study).
" We want to make the materials as perfect as possible in the
lab and understand the underlying functioning mechanisms, "
Chen said. " But we are open to opportunities to scale up the technology
and push it toward commercial applications. "
For more information, contact Jerry Grillo at jerry.grillo@
ibb.gatech.edu.
Dormant Capacity
Reserve in Lithium-Ion
Batteries Detected
Batteries undercut their theoretical capacity in practice,
sometimes significantly. In a lithium iron phosphate
cathode, researchers have now been able to
observe exactly where the capacity loss occurs.
Graz University of Technology, Graz, Austria
L
ithium iron phosphate is one of the most important materials for
batteries in electric cars, stationary energy storage systems, and
tools. It has a long service life, is comparatively inexpensive and
does not tend to spontaneously combust. Energy density is also
making progress. However, experts are still puzzled as to why lithium
iron phosphate batteries undercut their theoretical electricity storage
capacity by up to 25 percent in practice. To utilize this dormant
capacity reserve, it would be crucial to know exactly where and how
lithium ions are stored in and released from the battery material
during the charging and discharging cycles. Researchers at Graz
University of Technology (TU Graz) have now taken a significant step
in this direction. Using transmission electron microscopes, they were
able to systematically track the lithium ions as they traveled through
the battery material, map their arrangement in the crystal lattice of
an iron phosphate cathode with unprecedented resolution, and precisely
quantify their distribution in the crystal.
" Our investigations have shown that even when the test battery
cells are fully charged, lithium ions remain in the crystal lattice of
the cathode instead of migrating to the anode. These immobile ions
incur a cost in capacity, " said Daniel Knez from the Institute of
Electron Microscopy and Nanoanalysis at TU Graz. The immobile
lithium ions are unevenly distributed in the cathode. The researchers
have succeeded in precisely determining these areas of different
levels of lithium enrichment and separating them from each other
down to a few nanometers. Distortions and deformations were
Battery & Electrification Technology, November/December 2024
23
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