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'[TECH] Fluoride ions increasing lithium battery st'
| From Elektor weekly news.
"KIT (Karlsruhe Institute of Technology) researchers have developed a new
concept for rechargeable batteries. Based on a fluoride shuttle -- the
transfer of fluoride anions between the electrodes – it promises to enhance
the storage capacity reached by lithium-ion batteries by several factors.
Operational safety is also increased, as it can be done without lithium.
The fluoride-ion battery is presented for the first time in the “Journal of
Materials Chemistry” by Dr. Maximilian Fichtner and Dr. Munnangi Anji
"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.
M. Anji Reddy and M. Fichtner: Batteries based on fluoride shuttle. Journal
of Materials Chemistry. 2011, Advance Article. DOI: 10.1039/C1JM13535J."
> From Elektor weekly news.
Full paper may be obtained here
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Claims are, as ever, suspect and it is far from friendly so far.
Fluorine ions only known ion exchange electrolytes to date are solids.
In notes below they claim potential of 10X LiIon capacities but paper
says even theoretical capacity is lower than that.
Cell has metal electrode and metal fluoride electrode and charges or
discharges betwixt the two.
Presently has massive capacity loss per cycle due to mechanical volume
changes at electrode surface breakup
Then has all the usual problems LiIon has for same reason. Needs a
LiFePO4 type structure to save it.
p17061 bottom left.
Theoretical max capacity is 527 mAh/g of metal. That's probably one electrode.
Top capacity AA MimH is ~30g. Say 12g active material/electode to be kind.
12 gx 527 mAh/g ~= 6000 mAh in AA.
Compared to 2500 mAh real now in AA with NimH.
They then got 322 mAh /g actual on 1st cycle = 61% =~ 3600 mAh/AA and
it deteriorated rapidly from there.
Not looking good.
My per gram per electrode above may be wrong. MAY be able to double
those figures. Still not 10x LiIon.
ie 12Ah/2,5Ah = 4.8 x NimH now or 9.6x IF you can double it.
LiIon is slightly above best NimH at present.
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
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 Dr. Maximilian Fichtner.
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