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| Hauptseite > Publikationsdatenbank > High ionic conductivity in the system Na3+xSc2(SiO4)x(PO4)3-x |
| Hauptseite > Publikationsdatenbank > High ionic conductivity in the system Na3+xSc2(SiO4)x(PO4)3-x |
| Conference Presentation (After Call) | FZJ-2015-04569 |
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2015
Abstract: The abundance of sodium and the similarities between lithium and sodium intercalation processes make it an attractive alternative as a charge carrier in alkali ion-batteries. Therefore, interest in high sodium ion-conductive materials is increasing, especially in the widely studied class of NASICON solid electrolytes [1]. A literature survey concluded that the partial substitution of phosphorus with silicon in the NASICON materials of general formula Na1+2w+x-y+zM(II)wM(III)xM(V)yM(IV)2-w-x-y(SiO4)z(PO4)3-z enhances the ionic conductivity [2].The aim of this work is to elucidate the impact of introducing silicon ions in the highly conductive material Na3Sc2(PO4)3 [3] (sigmaNa=3.8*10-5 S∙cm-1 at 30 °C) and to obtain an even better ionic conductor suitable as electrolyte in a solid state sodium battery. Various compositions of the solid solution Na3+xSc2(SiO4)x(PO4)3-x with 0.1≤x≤0.8 were synthesized by solid state reaction and crystallographic data were gathered, correlated with results of ionic conductivity measurements and compared simulation models. As a result, one of the 10 best ion-conductive NASICON materials to date was obtained for x=0.4 (sigmaNa=8.3*10-4 S∙cm-1 at 30 °C). Furthermore, the ionic conductivity data were correlated with the structural bottleneck along the conduction pathway of the sodium ions and agrees well with the conductivity-structure-relationship established for the series Na1+x+yZr2-xScx(SiO4)y(PO4)3-y [2,4]. Besides, different ionic pathways of the sodium ions in the structure were studied with density functional theory (DFT) [5] and the nudged elastic band (NEB) method [6] and the resulting activation energies were compared with the experimental values. [1] H.Y.P. Hong, Mat. Res. Bull. 11 (1976) 173-182[2] M. Guin, F. Tietz, J.Power Sources 273 (2015) 1056-1064.[3] J.M. Winaud, A. Rulmont, P. Tarte, J.Mater. Sci. 25 (1990) 4008-4013[4] M.A. Subramanian, P.R. Rudolf, A. Clearfield, J.Solid State Chem. 60 (1985) 172-181.[5] P.E. Blöchl, Phys. Rev. B 50 (1994) 17953-17979[6] G. Henkelman, B.P. Uberuaga, H. Jónsson, J.Chem. Phys. 113 (2000) 9901-9904
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