The mechanism of operation of the anode in sodium-ion batteries

Раскрыт механизм работы анода натрий-ионных аккумуляторов

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Researchers from MSU and SKOLKOVO Institute of science and technology found out what happens when you work the anode material in sodium-ion batteries. The results of the study will bring the output on the mass market safe current sources. The work of scientists published in the journal Electrochimica Acta.

Li-ion batteries are today the most commonly used and represent the mass of the chemical current source. The need for them and the average size is growing, however this growth is linked to certain problems: the high cost of lithium salts, the limited world reserves of the metal and the heterogeneity of the distribution containing minerals on Earth. To overcome these difficulties, researchers try to create an alternative technology to sodium-ion batteries. It is assumed that it will be able to press not only Li-ion, but lead-acid batteries.

Sodium is the sixth most abundant substance in the crust of the earth element, the price of salt is approximately 100 times lower than lithium. These items are located in the same group of alkali metals and their properties in a similar way. However, because of certain differences in chemical properties it is necessary to look for special approaches for the replacement of lithium by sodium.

The main problem in sodium ion batteries is the anode. If the lithium analogs has been successfully used in graphite, for sodium it is not suitable due to the fact that the size of the carbon hexagons and sodium cations do not match each other and intercalating ions in the lattice of graphite does not occur. In such a system may find application “solid carbon”. This disordered structure of curved graphite-like layers, which is able to store a sufficiently large amount of sodium. But how exactly this happens is still was not entirely clear.

“There are a number of hypotheses about possible mechanisms of introduction of sodium in “hard carbon,” says supervisor, senior researcher, Center for energy science and technology Skoltech and the Moscow state University Oleg Drozhzhin. We have proved the validity of one of them, slightly further expanding it. We found that the main charge of “hard carbon” is gaining in intercalation mechanism, which is great news. Intercalation is necessary for the battery, and surface processes associated with “pseudoelastic” — a lot of supercapacitors, that is a very narrow niche of chemical current sources”.

According to the researchers, their work is interesting not only for experimental confirmation of one hypothesis of intercalation of sodium. One of the main achievements of researchers — creation of “hard carbon” with a capacity more than 300 mAh/g — about as in graphite in lithium-ion batteries.

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