High-entropy argyrodite glass–ceramic electrolytes for all-solid-state batteries

Lithium argyrodite superionic conductors with the general formula Li₆PS₅X (X = Cl, Br, I)
have been intensively investigated in recent years and successfully adopted in the field of
solid-state batteries (SSBs). The transport properties of argyrodite solid electrolytes (SEs)
usually strongly depend on the degree of occupational disorder. Increasing disorder through
complex doping or substitution has been shown to directly affect ionic conductivity.
Herein, we explore a high-entropy lithium argyrodite of nominal composition Li$_{6.6}$[P$_{0.2}$Si$_{0.2}$
Sn$_{0.2}$Ge$_{0.2}$Sb$_{0.2}$]S₅I. This material can be readily prepared by mechanochemistry. Using
complementary diffraction techniques, nuclear magnetic resonance spectroscopy, and
charge-transport measurements, we show that upon tailoring crystallinity and defect
concentration by post-annealing at temperatures up to 220° C, a high room-temperature ionic
conductivity of about 0.9 mS cm⁻¹ (∼4.4 mS cm⁻¹ bulk conductivity) can be achieved. Both
the as-prepared and annealed (at 220° C) samples were tested in pellet-stack SSB cells. The
mechanochemically prepared glass–ceramic SE was found to exhibit superior performance,
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even outperforming commercially available Li₆PS₅Cl. Collectively, the results highlight the
importance of considering structural aspects across different length scales when optimizing the
properties of lithium argyrodites for SSB applications.