Super‐Ionic Conductivity in ω‐Li₉TrP₄ (Tr = Al, Ga, In) and Lithium Diffusion Pathways in Li₉AlP₄ Polymorphs

Abstract

Phosphide-based compounds are promising materials for solid electrolytes. In recent times, a multiplicity of compounds featuring isolated MP 4 (M = Si,Ge,Sn,Al,Ga) tetrahedra as structural building units in different arrangements with superionic lithium conductivity have been discovered. ω-Li 9 AlP 4 , ω-Li 9 GaP 4 , and ω-Li 9 InP 4 are presented as new high-temperature modifications with superionic lithium conductivity reaching 4.5 mS cm −1 at room temperature. Impedance spectroscopy and static temperature-dependent 7 Li NMR experiments reveal conductivity values in the range of 0.2 to 4.5 mS cm −1 at room temperature and low activation energies for the title compounds. X-ray and neutron diffraction methods disclose that the phosphorus atoms form a cubicclose packing. The triel element and Li atoms are located in tetrahedral voids, further Li atoms partially fill the octahedral voids. Temperature-dependent neutron diffraction shows for Li 9 AlP 4 a phase transition at 573 K that influences the occupation of voids with Li and significantly affects the Li-ion mobility. The evaluation of nuclear scattering densities by the maximum-entropy approach and application of the one-particle-potential formalism reveal 3D lithium diffusion with a low activation energy preferentially on paths of adjacent tetrahedral and octahedral voids. The investigation of different polymorphs suggests that the equilibrated filling of tetrahedral and octahedral voids is a crucial parameter for the enhancement of superionic lithium conductivity.

Unraveling Sodium-Ion Dynamics in Honeycomb-Layered Na2MgxZn2–xTeO6 Solid Electrolytes with Solid-State NMR

“…The metal sleeve of the setup causes an internal capacitance on the order of 10 –10 F, which is the observed capacitance during the measurements. This so-called stray capacitance is not affecting the measured resistance and thus also does not influence the determined conductivities or activation energies and can be neglected for this work . Variable-temperature Nyquist plots for the other samples can be found in Figure S12.…”

“…This so-called stray capacitance is not affecting the measured resistance and thus also does not influence the determined conductivities or activation energies and can be neglected for this work. 128 Variable-temperature Nyquist plots for the other samples can be found in Figure S12. The obtained total resistances (R) were used to determine the total conductivity (σ) of the samples using Ohm's law…”

Trendbericht Festkörperchemie 2023

“…2) Fässler, van Wüllen und Mitarbeitende berichteten über drei neue Hochtemperaturmodifikatio-nen der Lithiumphosphidotrielate ω-Li 9 [TrP 4 ] (Tr Al, Ga, In), die Li + -Ionenleitfähigkeiten von bis zu 4,5 mS • cm -1 bei Raumtemperatur zeigen (Abbildung 1). 3) Durch Experimente und quantenchemische Methoden erklären sie diese Beobachtung und korrelieren die Leitfähigkeit mit der Struktur.…”

The cubic structure of Li3As stabilized by substitution – Li8TtAs4 (Tt = Si, Ge) and Li14TtAs6 (Tt = Si, Ge, Sn) and their lithium ion conductivity

“…Lithium phosphidotetrelates have become an interesting and intensely discussed family of compounds over the last years, because of their interesting structural diversity and high ionic conductivity. [1][2][3] First mentioned in the 1950s by Juza, the nitridosilicates, phosphidosilicates and arsenidosilicates received little attention. 4,5 In 2016, the compounds Li 2 SiP 2 and LiSi 2 P 3 were synthesized and characterized independently by Johrendt et al and by Fässler et al who also discovered Li 8 SiP 4 in the same year.…”