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In the area of sustainable energy storage, batteries based on multivalent ions such as magnesium have been attracting considerable attention due to their potential for high energy densities. Furthermore, they are typically also more abundant than, e.g., lithium. However, as a challenge their low ion mobility in electrode materials remains. This stu...

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Context 1
... order to further assess the ion mobility in these spinels structures, the energies along the Mg migration paths for MgSc 2 (S/Se) 4 and MgY 2 (S/Se) 4 in the high and low concentration of Mg-ion are plotted in Fig. 5. Note that in the high Mg-ion concentration limit, there are 7 Mg ions in the 2×2×2 supercell located in the tetrahedral sites one of which is migrating, whereas in the high Mg-ion concentration limit, there is only one Mg ion in the supercell that is also the migrating ion. The Mg-ion migration barriers of MgY 2 S 4 (∼ 360 meV), MgY 2 ...
Context 2
... the low Mg concentration limit, the Mg-ion migrations barriers in the S-and Se-spinels are increased compared to the high concentration limit, as shown in Fig. 5. Furthermore, in This varying site preference, which is not the case for the Y cation, might be detrimental for the performance of the Sc-containing cathodes upon charge/discharge. In addition, the MgY 2 (S/Se) 4 compounds exhibit smaller relative volume changes upon the addition of Mg atoms than the MgSc 2 (S/Se) 4 compounds, which ...

Citations

... 29 However, we could recently show that the stability of ions in chalcogenide spinels can only be understood if deviations from a purely ionic interaction are taken into account. 48 It is essential to realize that the considered binary materials span the whole range of interaction characteristics between metallic and ionic bonding. Such bonding characteristics can in fact been classified in so-called Van Arkel-Ketelaar triangles 49 in which compounds are placed according to the mean electronegativity χ mean (x-axis) and the electronegativity difference ∆χ (y-axis) of the constituting elements. ...
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Ion mobility is a critical performance parameter in electrochemical energy storage and conversion, but also in other electrochemical devices. Based on first-principles electronic structure calculations, we have derived a descriptor for the ion mobility in battery electrodes and solid electrolytes. This descriptor is entirely composed of observables that are easily accessible: ionic radii, oxidation states and the Pauling electronegativities of the involved species. Within a particular class of materials, the migration barriers are connected to this descriptor through linear scaling relations upon the variation of either the cation chemistry of the charge carriers or the anion chemistry of the host lattice. The validity of these scaling relations indicates that a purely ionic view falls short of capturing all factors influencing ion mobility in solids.The identification of these scaling relations has the potential to significantly accelerate the discovery of materials with desired mobility properties.