Crystal structures of the new Na2FeS2 positive electrode material. (IMAGE)
Caption
Top left: an iron atom sits at the center of a tetrahedron (brown), surrounded by four sulfur atoms (yellow). Top right: multiple tetrahedra can be combined to form long chains, which can lie parallel to one another. Bottom: sodium atoms (green) enter or leave the tetrahedra, during oxidation and reduction, in a highly reversible way to charge or discharge the battery, while keeping the structure intact.
Credit
Atsushi Sakuda, OMU
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