Beating Lithium-Ion Batteries Flat

Common elements such as sodium and iron could replace rare-earth metals in batteries of the future.

AsianScientist (Aug. 28, 2014) – Scientists have developed a new material for batteries that can perform just as well as existing lithium-ion batteries but does not require rare-earth metals. This research has been published in Nature Communications.

Rechargeable batteries are one of the key technologies required to bring about the future energy savings, enabling smart grids and electric cars. Lithium (Li) ion batteries offer the most advanced rechargeable energy-storage system, but ever-increasing demand has led to calls for much cheaper alternatives using more common elements. One candidate is the sodium (Na) ion battery, which uses naturally abundant sodium in place of rare lithium.

Much research to date, however, has focused on screening compounds already used in lithium ion batteries and replacing lithium with sodium, but the poor performance of these materials means they are of limited practical use. Researchers have also tried to combine sodium with other cheap and plentiful elements such as iron (Fe), but experience has shown that creating practical iron-based compounds is extremely difficult.

Professor Atsuo Yamada’s research group at the University of Tokyo’s Graduate School of Engineering has explored Na-Fe based compounds with entirely novel compositions and structures. Now, the group has discovered a new “earth-abundant” cathode material and determined its crystal structure. This new material does not contain any rare metals and can be easily synthesized, enabling the development of sodium-ion batteries with superior performance to lithium-ion batteries.

The new material includes a large number of Na+ ions, which can be inserted/extracted along with electrons located around Fe ions during the discharge/charge processes. The present discovery goes against conventional belief that this reaction was impossible in Na-Fe compounds.

Using the novel material as cathode, it is possible to create a battery that generates a high voltage of 3.8 V versus sodium, far exceeding that of current materials. In addition, the extremely fast diffusion of sodium ions can offer quick charge-discharge in just a few minutes.

The article can be found at: Barpanda et al. (2014) A 3.8-V Earth-Abundant Sodium Battery Electrode.

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Source: University of Tokyo.
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