Metal fluorides: ingredients of the battery of the XXIst century

energy efficiency, lithium-ion battery, Metal fluorides, electric carsUntil recently, lithium batteries were the state of the art. They are used in domestic appliances of our daily life (computers, cell phones…), as well as under the hood of some electric cars. But research has accelerated and could soon give birth to a brand new kind of battery: safer, lighter and more compact, metal fluoride batteries are above all able to store much more energy.

German researchers at the Karlsruher Institut für Technologie (KIT) are about to develop a new kind of battery[1] which could store up to six times more energy than conventional models. The stakes are high since increased energy efficiency in future batteries must enable mobile devices and electric vehicles to be lighter, smaller and more efficient.

As far as electric car batteries are concerned, electrochemical lithium-ion batteries still represent the best technology. Each battery includes separate cells, which in turn consist of two electrodes made out of thin metal layers, one covered with graphite, the other with a lithium compound, between which a conductive liquid is introduced to allow electrons to flow. The efficiency of such a battery depends on its chemical composition, and the lithium-ion battery’s limits are already becoming apparent. Used in an electric car, it yields, at the best, a 160 km range.

It is therefore necessary to develop new materials. The team led by Maximilian Fichtner at the KIT has already tested materials that are twice more efficient than those used by the industry to produce the best car batteries on the market. Instead of lithium and graphite, researchers bet on metal fluorides.

The idea is not new: as Maximilian Fichtner explains, “this solution has been envisioned since the 1970s, but we are the first to have proven that the principle actually works.” In his battery, fluoride ions travel from one electrode to the other and transport electric current. The improvement from a traditional lithium battery is that “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., says the researcher. Moreover, since lithium is rare, expensive and dangerous, the advantage of lithium-free batteries is their increased operational safety. As a consequence, on top of being more efficient, new batteries could end up being not only cheaper but also safer.

Potential applications of metal fluoride batteries are as broad as the field of electronics itself: their increased range and density could work wonders in cell phones, as well as in the engine of tomorrow’s electric car. In a couple of years, Fichtner plans to experiment his batteries on an electric vehicle, with an expected range of 500km.

[1] http://www.dw.de/dw/episode/0,,15659685,00.html

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