The opto-ionic effect: Light may increase performance of fuel cells and lithium-ion batteries
Light can be used to increase the ionic conductivity of energy materials
Date:
March 22, 2022
Source:
Technical University of Munich (TUM)
Summary:
Lithium-ion batteries, fuel cells and many other devices depend on
the high mobility of ions in order to work properly. But there a
large number of obstacles to such mobility. Researchers have now
shown that light can be used to increase the mobility of ions and
improve the performance of such devices.
FULL STORY ========================================================================== Lithium-ion batteries, fuel cells and many other devices depend on the
high mobility of ions in order to work properly. But there a large number
of obstacles to such mobility. A research team led by Jennifer L. M. Rupp
of the Technical University of Munich (TUM) and Harry L. Tuller of the Massachusetts Institute of Technology (MIT) have now shown for the first
time that light can be used to increase the mobility of ions and improve
the performance of such devices.
==========================================================================
A charge can be transported by a material in a number of different
ways. The most familiar is the electrical conductivity of metals, where
the charge is borne by electrons. In many devices, however, ions transport
the charge. One example is lithium-ion batteries in which lithium ions
move during charging and discharging. Similarly, fuel cells rely on the transport of hydrogen and oxygen ions in order to conduct electricity.
Ceramics are currently being investigated as solid electrolytes
for transporting oxygen ions. But: "What we find is that the ionic
conductivity - - the rate at which the ions can move and, therefore, how efficient the resulting device can be -- is often markedly degraded by
the fact that the ions get blocked at grain boundaries," says Prof. Harry
L. Tuller of the Massachusetts Institute of Technology.
Light puts ions on the go In their current publication Tuller and his
colleague Jennifer L. M. Rupp, Professor for solid-state electrolyte
chemistry at the Technical University of Munich, show how light can
be used to reduce the barriers encountered by ions at ceramic grain
boundaries.
Many devices based on ion conductivity, such as solid-oxide fuel cells,
have to operate at very high temperatures in order for the ions to be
able to overcome the grain boundary barriers. Operating temperatures of
up to 700DEG Celsius, however, present their own challenges: Materials
age faster and the infrastructure for maintaining these high temperatures
is costly.
==========================================================================
"Our dream was to see if we could overcome the barriers using something
that doesn't require heat. Could we get the same conductivities with
another tool?" says lead author and PhD student Thomas Defferriere. This
tool turned out to be light, which had never been investigated in this
context before.
Higher efficiency levels in energy conversion and storage "Our research
shows that illumination of ceramic materials for fuel cells and possibly
for batteries in the future can significantly increase ion mobility," says Rupp. "In gadolinium-doped cerium oxide, a ceramic used as a solid-state electrolyte in fuel cells, illumination increased conductivity at the
grain boundaries by a factor of 3.5." This newly discovered "opto-ionic effect" could find a wide range of applications in the future. For
example, it could improve the performance of solid-state electrolytes
in tomorrow's lithium-ion batteries and thus facilitate higher charging
speeds, or could pave the way to the development of new electrochemical
storage and conversion technologies that work at lower temperatures and
achieve higher efficiency levels.
Light can also be precisely focused, making it possible to spatially
control the ion flow at exactly defined points or to switch conductivity
in ceramic materials.
The research was supported by the US Department of Energy as a part
of the Basic Energy Services program, the National Science Foundation
of the USA, the Japan Society for the Promotion of Science as a part
of the Core-to-Core program, the Swiss National Science Foundation,
two Kakenhi Grants-In-Aid for young scientists and Equinor ASA.
Part of the research was conducted at the Massachusetts Institute
of Technology's Materials Research Science and Engineering Center,
and another part at the Center for Nanoscale Systems, which belongs to
the National Science Foundation's National Nanotechnology Coordinated Infrastructure Network.
========================================================================== Story Source: Materials provided by
Technical_University_of_Munich_(TUM). Note: Content may be edited for
style and length.
========================================================================== Journal Reference:
1. Thomas Defferriere, Dino Klotz, Juan Carlos Gonzalez-Rosillo,
Jennifer L.
M. Rupp, Harry L. Tuller. Photo-enhanced ionic conductivity across
grain boundaries in polycrystalline ceramics. Nature Materials,
2022; DOI: 10.1038/s41563-021-01181-2 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/03/220322130035.htm
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