Argyrodite, as defined by Wikipedia, is a silver germanium sulfide. The quest for all solid state batteries has led to an argyrodite definition of Li6PS5X (X = Cl, Br, I). One reason Hanghofer and coauthors (2019) cite for this redefinition is the expense of Ge. These authors compared chloride, bromide, and iodide salts of this material. Ampcera sells the chloride salt as well a a proprietary blend in which halides have been replace with silicon.

  • Li6PS5Cl (fine) Ionic Conductivity: >3 × 10−3S/cm (>3 mS/cm) at room temperature (RT)

  • Li6PS5Cl (course) Ionic Conductivity: > 2 × 10−3 S/cm (>2 mS/cm) at RT

  • LixPxSxSix (fine) Ionic Conductivity: > 2 × 10−3 S/cm (> 2 mS/cm) at RT

  • LixPxSxSix (course) Ionic Conductivity: > 4 × 10−3 S/cm (> 4 mS/cm) at RT

From Hanghofer (2019) The argyrodite structures. Their positions on the periodic table of elements is shown. Ampcera sells an innovative, halogen free alternative.

Hanghofer and coworkers (2019) discussed sources of capacitative elements in the electrical impedance of argyrodite. Not only is the bulk grain a source of impedance, but also the grain boundary.

Top Left.  A single crystal may be composed of multiple grains, the boundaries of which are a source of impedance. Bottom Left, Nyguist plot for Ampcera’s halide free argyrodite. Right, Nyquist plot from Hanghofer (2019).

While room temperature conductivities of  coarse vs. fine  Ampcera  Li6PS5Cl are different, the Nyquist plots appear to be about the same.

Arrhenius plots of fine and course Li6PS5Cl.  Insets are photos of the crystals.

X-ray diffraction patterns of course versus fine Ampcera  Li6PS5Cl   are also quite similar despite differences in room temperature conductivity.

X-ray diffraction data for course versus fine Li6PS5Cl

Similarities in Nyquist plots and X-ray diffraction data of course and fine Li6PS5Cl suggest that differences in conductivity may arise from _______.


Substitutional disorder: structure and ion dynamics of the argyrodites Li6PS5Cl, Li6PS5Br and Li6PS5I

I. Hanghofer, M. Brinek, S. L. Eisbacher,a B. Bitschnau,b M. Volk V. Hennige I. Hanzu D. Rettenwandera and H. M. R. Wilkening Phys. Chem. Chem. Phys.,2019, 21, 8489 link

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