Enhancement in ionic conductivity of Dysprosium doped Li7La3Zr2O12 solid electrolyte applied in Li-ion batteries
Salimkhani, Hamed (2020) Enhancement in ionic conductivity of Dysprosium doped Li7La3Zr2O12 solid electrolyte applied in Li-ion batteries. [Thesis]
In this investigation, a novel Li-stuffed garnet type solid electrolyte with enhanced properties was fabricated. For this purpose, different concentrations of Dy ranging from 0.1 to o.8 atoms per formula unit (pfu) were doped into the Li7La3Zr2O12 to stabilize the cubic structure and, therefore, tailor the ionic conductivity. Furthermore, fundamental studies were performed through X-ray diffraction and Rietveld refinement to develop crystal structure of the Dy doped LLZO and determine the site preference of Dy. On another attempt in this study, Density Functional (DFT) total energy computations were applied to investigate the convergence of Dy at different Wyckoff sites energetically and to further validate the results of experiments. Additionally, 7 Li and 6 Li solidstate MAS NMR was performed to reveal the chemical coordination of Li at different sites. The results of this thesis project indicated that Dy ions probably substitute for Zr site and Li ions prefer tetrahedral (24d) and octahedral (48g) atomic sites. Additionally, our novel solid electrolyte demonstrated the highest ionic conductivity (2.03×10-3 S.cm-1 ) reported for LLZOs.
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