Lithium ion diffusion in Li β-alumina single crystals measured by pulsed field gradient NMR spectroscopy

Abstract

Lithium ion micrometer diffusion in a garnet-type cubic Li 7 La 3 Zr 2 O 12 (LLZO) studied using 7 Li NMR spectroscopy The Journal of Chemical Physics 146, 024701 (2017) The lithium ion diffusion coefficient of a 93% Li β-alumina single crystal was measured for the first time using pulsed field gradient (PFG) NMR spectroscopy with two different crystal orientations. The diffusion coefficient was found to be 1.2 × 10 −11 m 2 /s in the direction perpendicular to the c axis at room temperature. The Li ion diffusion coefficient along the c axis direction was found to be very small (6.4 × 10 −13 m 2 /s at 333 K), which suggests that the macroscopic diffusion of the Li ion in the β-alumina crystal is mainly two-dimensional. The diffusion coefficient for the same sample was also estimated using NMR line narrowing data and impedance measurements. The impedance data show reasonable agreement with PFG-NMR data, while the line narrowing measurements provided a lower value for the diffusion coefficient. Line narrowing measurements also provided a relatively low value for the activation energy and pre-exponential factor. The temperature dependent diffusion coefficient was obtained in the temperature range 297-333 K by PFG-NMR, from which the activation energy for diffusion of the Li ion was estimated. The activation energy obtained by PFG-NMR was smaller than that obtained by impedance measurements, which suggests that thermally activated defect formation energy exists for 93% Li β-alumina single crystals. The diffusion time dependence of the diffusion coefficient was observed for the Li ion in the 93% Li β-alumina single crystal by means of PFG-NMR experiments. Motion of Li ion in fractal dimension might be a possible explanation for the observed diffusion time dependence of the diffusion coefficient in the 93% Li β-alumina system.

Li10GeP2S12‐Type Superionic Conductors: Synthesis, Structure, and Ionic Transportation

“…It can also be directly measured by neutron radiography, [ 97,98 ] or pulsed‐field gradient nuclear magnetic resonance (PFG‐NMR). [ 99–101 ] Bron et al. and Kuhn et al.…”

Lithium-ion conductivity and crystal structure of garnet-type solid electrolyte Li₇₋<i>_x</i>La₃Zr₂₋<i>_x</i>Ta<i>_x</i>O₁₂ using single-crystal

“…Oxide-base solid electrolytes are also classified into glass-type, glass-ceramics-type and crystalline-type. Among crystalline solid electrolytes, NASICON-type Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 , 6) perovskite-type La 2/3¹x Li 3x TiO 3 , 7) ¢-alumina with Na+/Li+ ion-exchange type, 8) garnettype Li 7 La 3 Zr 2 O 12 and the like are also reported. 9)27) A garnet-type lithium solid electrolyte possesses, as the name implies, a very similar crystal structure as garnet used as a precious stone, or yttrium-aluminum-gallium (YAG) garnet used as optical crystals, 28) or yttrium-Iron-Gallium garnet used as magnetic materials.…”

High Ionic Conductor Member of Garnet‐Type Oxide Li6.5La3Zr1.5Ta0.5O12

“…Oxide solid electrolytes are further classified into glass, glass‐ceramic, and crystalline types. Crystalline solid electrolytes include LISICON, perovskite, β‐alumina with Na + /Li + ion exchange, and garnet types . Li 7– x La 3 Zr 2– x Nb x O 12 , and Li 7– x La 3 Zr 2– x Ta x O 12 ,,,, in which part of Li 7 La 3 Zr 2 O 12 ,, is substituted with niobium or tantalum, has high lithium ion conductivity and a wide potential window.…”