A
team of battery researchers led by the University of California San Diego and
University of Chicago has developed a new methodology to produce the
potentially game-changing thin-film solid-state electrolyte called lithium
phosphorus oxynitride (LiPON). The team went on to implement their
free-standing version of LiPON film in functional battery tests and found that
it promotes a uniformly dense lithium metal electrochemical deposition under
zero external pressure, with the aid of internal compressive stress and a gold
seeding layer. This work, performed by a team of battery researchers led by the
University of California San Diego and University of Chicago, was published in
the journal Nature Nanotechnology on
August 03, 2023.
The research team is led by battery
researcher and professor Ying Shirley Meng, who is affiliated with both the
University of Chicago and UC San Diego. The first author is Diyi Cheng, a
recently graduated Ph.D. in the Materials Science and Engineering Program at
the UC San Diego Jacobs School of Engineering who is continuing his research
efforts at Lawrence Berkeley National Laboratory. The team also includes
researchers from Lawrence Livermore National Laboratory and UC Berkeley.
LiPON is a thin-film solid-state
electrolyte that conducts lithium ions and shows strong promise for pairing with a
broad range of electrode materials for the lithium battery industry of the
future. However, existing methods for producing LiPON have prevented
researchers from fully understanding the material. Now, the team found a way to
produce this promising solid-state electrolyte in a free-standing form that
allows LiPON to be studied more comprehensively. The new approach to making
LiPON has also opened the door to using this solid-state electrolyte to enable lithium
metal solid-state batteries that could work under minimal external pressure.
Video of the new transparent, thin-film FS-LiPON
material developed at UC San Diego which promotes a uniformly dense lithium
metal electrochemical deposition under zero external pressure, with the aid of
internal compressive stress and a gold seeding layer. The team also reports
that this new stand-alone thin-film version of LiPON enables fundamental
research (ss-NMR and Cryo-EM) of ion conduction and electrochemical performance.
Credit: UC San Diego Laboratory for Energy Storage and Conversion / Diyi Cheng
The LiPON Challenge
LiPON was originally developed by a
group of scientists at Oak Ridge National Laboratory in 1992. Despite
continuous research efforts over the last three decades, there remains a
substantial lack of thorough understanding of LiPON's intrinsic properties and
its associated interfaces, holding back the promise and advancement of LiPON
materials. Several
factors leading to this dilemma include:
- LiPON is an amorphous
material that gives little structural information by regular
diffraction-based techniques.
- LiPON is sensitive to
ambient air and electron beams, which further confines the available tools
for study.
- Traditional LiPON
synthesis is conducted on solid substrates. This approach is inadequate
for generating conclusive signals for spectroscopic measurements.
New approach to LiPON production leads to new insights
Given the known challenges to
studying LiPON, the team developed a new methodology for producing LiPON film in a free-standing
form. The result is a flexible and transparent free-standing LiPON (FS-LiPON) film
that is compatible with a broad range of spectroscopic techniques that have
greater chances of unraveling the unique properties of LiPON over the
diffraction-based techniques. This advance yielded fresh insights, described in
the new Nature Nanotechnology paper on LiPON's interfacial
chemistry, thermal properties and mechanical properties. Insights include:
- Solid-state nuclear
magnetic resonance measurement uncoverd a quantitative view of interface
formation between lithium metal and LiPON
- Differential scanning
calorimetry measurements showed a well-defined glass-transition
temperature of LiPON around 207 degrees Celsius
- Nanoindentation measurement gave a Young's modulus of LiPON around 33 GPa
Photograph
of the new transparent, thin-film FS-LiPON material which promotes a uniformly
dense lithium metal electrochemical deposition under zero external pressure,
with the aid of internal compressive stress and a gold seeding layer. The team
also reports that this new stand-alone thin-film version of LiPON enables
fundamental research (ss-NMR and Cryo-EM) of ion conduction and electrochemical
performance. Credit: UC San Diego Laboratory for Energy Storage and Conversion
/ Diyi Cheng
Uniformly dense lithium metal deposition under zero external pressure
In addition to gleaning new
fundamental insights on LiPON, the research team also implemented the new
free-standing version of the solid-state electrolyte in functional battery
tests. The team reports that the thin-film FS-LiPON promotes a uniformly dense
lithium metal electrochemical deposition under zero external pressure, with the
aid of internal compressive stress and a gold seeding layer. This finding gives
valuable hints regarding interface engineering in bulk solid-state batteries.
LiPON-based thin film batteries
have shown great potential for wearables and other compact electronic devices
with a gigantic market. The FS-LiPON film produced in this work described by
Diyi Cheng et al. in Nature Nanotechnology enabled in-depth
discussions on interfacial chemistry, ion diffusion and interface engineering,
which shed light on both the fundamentals and applications of LiPON materials,
and could benefit the lithium solid-state battery development in many ways.
"A free-standing lithium phosphorus oxynitride thin film electrolyte promotes uniformly dense lithium metal deposition with no external pressure," is published in Nature Nanotechnology.
by Daniel Kane, University of
California - San Diego
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