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Setup of the fluoride-ion battery: A fluoride-containing electrolyte separates the metal anode from the metal fluoride cathode. (Figure: KIT)
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Lithium-ion
batteries are applied widely, but their storage capacity is limited. In
the future, battery systems of enhanced energy density will be needed
for mobile applications in particular. Such batteries can store more
energy at reduced weight. For this reason, Karlsruhe Institute of
Technology researchers are also conducting research into alternative
systems. A completely new concept for secondary batteries based on metal
fluorides was developed by Dr. Maximilian Fichtner, Head of the Energy
Storage Systems Group, and Dr. Munnangi Anji Reddy at the KIT Institute
of Nanotechnology (INT).
Metal
fluorides may be applied as conversion materials in lithium-ion
batteries. They also allow for lithium-free batteries with a
fluoride-containing electrolyte, a metal anode, and metal fluoride
cathode, which reach a much better storage capacity and possess improved
safety properties. Instead of the lithium cation, the fluoride anion
takes over charge transfer. At the cathode and anode, a metal fluoride
is formed or reduced.
“As
several electrons per metal atom can be transferred, this concept
allows to reach extraordinarily high energy densities—up to ten times as
high as those of conventional lithium-ion batteries,” explains
Fichtner.
The
KIT researchers are now working on the further development of material
design and battery architecture in order to improve the initial capacity
and cyclic stability of the fluoride-ion battery. Another challenge
lies in the further development of the electrolyte: The solid
electrolyte applied so far is suited for applications at elevated
temperatures only. It is therefore aimed at finding a liquid electrolyte
that is suited for use at room temperature.
Batteries based on fluoride shuttle
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