Mechanochemical Synthesis of Potassium–Ion Conductor K<sub>3</sub>SbS<sub>4</sub>

Antimony-based sulfide solid electrolytes exhibit high conductivity for alkaline cations.In this study, we synthesized K3SbS4 potassium-ion conductors using the mechanochemical method for the nominal compositions with x mol% excess K2S (x = 0, 5, 10, and 15) to compensate for the chemical impurities in the K2S reagent.The mechanochemically prepared samples showed X-ray diffraction patterns similar to -K3SbS4 in all the compositions.Raman bands attributed to the SbS4 3-unit were observed in all the samples.The ionic conductivities at 25 C showed a positive correlation with increasing x, reaching a maximum ionic conductivity of 3.6 10 -6 S cm -1 at 10 mol% excess K2S.Subsequent heat-treatment further enhanced the ionic conductivity, achieving 1.2 10 -5 S cm -1 at 25 C.This improvement is attributed to the nominal composition being close to that of K3SbS4 by adjusting the excess amount of K2S and the increased crystallinity of -K3SbS4.