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KIT researchers develop fluoride-ion batteries; potential for much higher energy densities than conventional Li-ion batteries

Setup of the fluoride-ion battery: A fluoride-containing electrolyte separates the metal anode from the metal fluoride cathode. Click to enlarge.

Researchers from the Karlsruher Institut für Technologie (KIT) have developed and demonstrated secondary (i.e., rechargeable) battery cells based on a fluoride shuttle. A paper on their work is published in the RSC Journal of Materials Chemistry. The team also presented the work at the recent 220th meeting of the Electrochemical Society (ECS) in Boston.

Metal fluorides may be applied as conversion materials in lithium-ion batteries. They also can enable lithium-free batteries comprising a fluoride-containing electrolyte; a metal anode; and metal fluoride cathode. Instead of the lithium cation (as in Li-ion batteries), the fluoride anion takes over charge transfer. The resulting fluoride-ion batteries can reach a much better storage capacity and possess improved safety properties, according to the team.

In the search for new concepts to build batteries with high energy densities it may be interesting to transfer the well-established, so-called rocking-chair principle of Li-ion batteries also to other ions so that electrochemical cells can be built which do not necessarily contain lithium but have the potential to reach theoretical energy densities which are considerably beyond the state-of-the art.

Fluoride ion batteries are capable of meeting this high energy density demands. The reaction of highly electronegative fluorine with metal leads to the formation of metal fluorides which are accompanied by large change in free energy and thus the high voltage. By choosing appropriate metal/metal fluorides, high voltage electrochemical cells can be built. Though few reports are known towards this end, such battery chemistry was largely overlooked in the past years. The recent report by Potanin et al. revised the interest in this field.

—Reddy et al., ECS 220

The fluoride anion acts as a charge transfer ion between a metal/metal fluoride pair where it will react with metal or evolve from metal fluoride depending on the flow of current—i.e. at the cathode and anode, a metal fluoride is formed or reduced, depending on whether the battery is charging or discharging. The fluoride-ion batteries could surpass the storage capacity reached by lithium-ion batteries, according to Drs. Maximilian Fichtner and Munnangi Anji Reddy.

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.

—Dr. Maximilian Fichtner

Composition of the electrodes and architecture of the samples used in the study. Credit: RSC, Reddy et al. Click to enlarge.

In the Journal of Materials Chemistry study, they prepared five different cathode composites comprising a metal fluoride, carbon, and La0.9Ba0.1F2.9 electrolyte, and paired those with the La0.9Ba0.1F2.9 electrolyte and a cesium metal (Ce) anode.

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; the researchers are looking for a liquid electrolyte that is suited for use at room temperature.




fluoride ion battery couldn't be recharged so far, and they pause serious environmental problems.


Interesting other avenue to arrive at much higher energy density future batteries. Future electrified vehicles many have more choices of battery technologies.


Im interrested to buy. Hurry-up, petrol is still flowing like mad. Leafs and volts are not selling that much


It's like clock work. Anytime a new development is announced the Spinach Party activists claim its got environmental problems.

Treehugger before making wild assertions let's see some hard scientific evidence please.


Early days, but good to have more avenues.
Where does that leave us looking for a BEV battery that is at least 2x the charge density of today's shipping batteries?

Toyota's solid state Lithium
Stanford's Silicon Nanowire and other nanosilicon geometries,
Lithium Sulfur,
Lithium Air (with water impermeable membranes),

Further out perhaps:
MIT's nanotubes coated with cyclotrimethylene trinitramine (maybe it's a fuel cell).
Cambridge's semi-solid flow cells.
MIT's carbon nanotube Lithium Air battery research.
Ionic liquids?
What else might make it big in the next 5 years?

Henry Gibson

The sodium sulphur battery is really quite energy dense and also very simple. NGK has made many cells up to this point and has had relatively few problems with the cells. It is not known how many cells have been made, but there are several installations throughout the world, including in the US.

The ZEBRA battery and the proposed GE version the DURATHON are also quite energy dense but less simple and does not contain liquid corrosive sulphur.

New versions of the lead batteries can be used for high power regeneration and acceleration along with high energy ZEBRA type batteries and a small range extender. ..HG..


Just wait, soon the naysayers will be bringing up the threat of 'peak fluoride.'


@Ai Vin,

...and the danger to dental health that the ensuing flouride shortage will have on the cost of our toothpaste!


Interesting days ahead. About 10 years ago, everybody was talking about future high performance Lithium batteries for BEVs. Today, there are 10+ variations of lithium batteries plus another 10+ new technologies being considered. What will be available in another 10 years?

One thing seems to be almost certain, in 10 years time, BEVs will have many choices with various battery technologies offering up to 1000 Wh/Kg. Extended range BEVs will travel up to 1000 Km with one single charge.

The world will evolve faster with clean e-energy generation and storage in the next 25 years than than it has in the previous 100+ years.


Henry - you forgot to mention the CANDU reactor in your post.... just sayin'.

Henry Gibson

A few weeks ago in the US Listeria killed off at least 25 people and several thousand people were very ill.

No one is dead from the radiation released when a tsunami destroyed nuclear reactors by cutting off the emergency power for their cooling systems.

Not one of the countries which now have claimed to have terminated the use of nuclear power because of the imagined, but not real, danger of death have stopped the sale of tobacco products within their borders. Tobacco products expose more people to death and illness than nuclear reactors do. The products are also a direct link to deliver radioactive materials directly into the human body. Navajo uranium miners in the US who smoked had far more death and illness from lung disease than those who did not. Yes Tobacco contains radio-active atoms in addition to the far more deadly chemical molecules produced by the tobacco fire.

The knee jerk reactions of turning off non damaged nuclear reactors in Japan has resulted in more deaths and illness due to lack of heat and lighting.

This is in addition to the stress cause by the false fears promulgated by the media which has ignored the deaths and suffering of the people from the earthquake and tsunami to concentrate their effort and space on the relatively low level of radiation released. Ordinary firemen are exposed to more immediate death every day than the emergency workers at the failed reactors in Japan.

CANDU reactors have fuel elements that release only one tenth of the heat after the shut down of the reactors than the old boiling water reactors in Japan and have much more cooling water in reserve. The operation of the CANDU reactor depends upon the fuel elements being separated from each other by several inches of water and there is much more additional water held in reserve.

Merkel wishes to get re-elected by subjecting her economy to failure by the expense of very expensive fossil carbon energy. There are many places in Germany where an earthquake of 9.0 would not destroy a CANDU reactor, and the pebble bed reactor that was once in service there and partially copied by the Chinese cannot get its fuel cladding melted nor its fuel itself melted. The new under sea pipe that delivers natural gas from Russia to Germany is easily fractured by earthquakes.

In the US, children must be in special car seats to reduce deaths and injuries in addition to all the other special features done to reduce deaths and injuries in automobiles since the failed Japanese reactors were built with a 1966 design.

Human life cannot be made perfectly safe. Almost all, if not all, of the articles about the failed nuclear plants failed to mention that Humans have, from nature, built in radio-activity from natural potassium as do all live things since life began on the earth.

Tokyo Electric Company spent a great deal of money supporting the development of NGK's sodium sulphur batteries, but large installations of them were made at a wind farm instead of at a nuclear power plant where their electricity could have kept billions of yen of reactors cool for days.

Tokyo Electric Company also did some research that a reactor pumping and cooling system could be operated directly by steam alone similar to how water was pumped into locomotive boilers in the UK by steam injectors. Steam operated eductors are well known in the nuclear industry, and they could be operated for cooling at low pressures. The very low pressure ten psi. steam from locomotive piston exhaust was used to pump water into 250 psi. lokomotive boilers in the UK.



...and the danger to dental health that the ensuing flouride shortage will have on the cost of our toothpaste!

Hey, as long as they get it out of our water supply I'll be happy. 'cause you know that's all a communist plot to control our minds!

Just thank GOD we have the John Birch Society to warn us of stuff like this.


Perhaps the fluorine shuttle can be replaced with a chlorine shuttle. There's plenty of chlorine in NaCl.

HarveyD are probably correct but changing peoples perception, attitude and acquired behavior is a major long term task that most successful politicians will not dare to touch.

Look at what is happening with our acquired love of over sized gas guzzlers. The majority will not let go of those monsters so easily.

With the exception of France, most EU countries (and USA) are still scared of nuclear power plants. China may be one of the few countries to build new nuclear power plants in large numbers in the current decade.


While supporting nuclear is general I would say for now it is dificult making decision on nuclear development due to extremly high investment cost due to redundant safty regulations which in the end are not regulating but making obstruction to the process. The investment cost in case not current nuclear regulations would be few times less. That makes major impact (90%) on bulk sales price which is about $80/MWh for new nucler facilities. That is on the level of natural gas and bigger than coal power on US bulk power market.
Another real issue intimidating investors - potential damages which are not covered by any inssurance and not reflected on power price. In Fukushima case claimed damages are $74bn.


Wasn't nuclear power suppose to be "too cheap to meter?"



Hmmmm... lanthanum and cerium. Even though those are the most common rare-earth elements, I wonder how long the easy-to-mine deposits would last. The ore in the Mountain Pass mine in California also contains significant amounts of radium and thorium, which were spilled and carelessly dumped by the previous owner, Unocal. I sure hope the current owner, Molycorp, does a better job of managing that stuff. I have no doubt the mess is much worse in China, where most rare earth metals are mined today.

Jerry John

The products are also a direct link to deliver radioactive materials directly into the human body. Navajo uranium miners in the US who smoked had far more death and illness from lung disease than those who did not. Yes Tobacco contains radio-active atoms in addition to the far more deadly chemical molecules produced by the tobacco fire.

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