The mechanism of Li-ion transport in the garnet Li₅La₃Nb₂O₁₂

Abstract

We present a detailed study on the exact location and dynamics of Li ions in the garnet-type material Li(5)La(3)Nb(2)O(12) employing advanced solid state NMR strategies. Applying temperature-dependent (7)Li-NMR, (6)Li-MAS-NMR, (6)Li-{(7)Li}-CPMAS-NMR, (6)Li-{(7)Li}-CPMAS-REDOR-NMR as well as 2D-(6)Li-{(7)Li}-CPMAS-Exchange-NMR spectroscopy, we were able to quantify the distribution of the Li cations among the various possible sites within the garnet-type structure and to identify intrinsic details of Li migration. The results indicate a sensitive dependence of the distribution of Li cations among the tetrahedral and octahedral sites on the temperature of the final annealing process. This distribution profoundly affects the mobility of the Li cations within the garnet-type framework structure. Extended Li mobility at ambient temperature is only possible if the majority of the Li cations is accommodated in the octahedral sites, as observed for the sample annealed at 900 degrees C. Octahedrally-coordinated Li cations could be identified as the mobile Li species, whereas the tetrahedral sites seem to act as a trap for the Li cations, rendering the tetrahedrally-coordinated Li cations immobile on the time scale of the NMR experiments.

Structural limitations for optimizing garnet-type solid electrolytes: a perspective

“…The mechanism involves immobile tetrahedrally coordinated Li sites (Wyckoff 24d) with the Li-ions hopping between the octahedral sites, bypassing these tetrahedral sites. 18,[21][22][23][24][25] Further experimental results corroborate the octahedral pathway mechanism with static Li cations on the tetrahedral sites. It was found that in Li 7 La 3 Zr 2 O 12 impurity ions like Al 3+ , which are necessary to stabilize the cubic garnet, are located on the tetrahedral 24d site.…”

Li Ion Dynamics in Al-Doped Garnet-Type Li7La3Zr2O12 Crystallizing with Cubic Symmetry

“…At room temperature the corresponding 6 Li NMR spin-lattice relaxation time is in the order of 1000 s whereas that of the main component is less than 10 s. Li 2 CO 3 might either stem from the preparation route chosen or from the reaction with ambient air as also found in the case of lithium lanthanum titanate (LLT) [20]. Note that the replacement of Li + by H + , which is the key reaction for the formation of Li 2 CO 3 in the case of LLT, was reported at least for the related garnet-type electrolytes Li 5 [21]. IR spectra in the mentioned work revealed the characteristic bands of carbonate ions.…”

“…In recent years, Li containing garnets have attracted large interest due to their potential usage as electrolytes in all-solid-state Li secondary batteries [1][2][3][4][5][6][7][8]. The high lithium-ion conductivity of such ceramics showing good electrochemical stability to lithium metal makes them promising candidates to be used, for example, in thin-film batteries [9].…”

First and Second Universalities: Expeditions Towards and Beyond

“…This includes friends and colleagues both inside and outside SFB 458, as well as KF's past coworkers. To name just a few, in alphabetical order, we would especially like to thank A. Bunde Besides thanking our friends at SFB 458 for an atmosphere of intense engagement and healthy exchange of views, we also would like to cite a few relevant results of theirs [110][111][112][113][114][115][116][117][118][119][120][121][122][123][124][125][126] which have added new insights while addressing issues complementary to those treated in this overview.…”