Argyrodite-type Li6PS5X (X = Cl, Br, I) was prepared using mechanical milling followed by annealing. X-ray diffraction characterization reveals the formation and growth of crystalline Li6PS5X in all cases. Ionic conductivity of the order of 7  x  10−4S/cm in Li6PS5Cl and Li6PS5Br renders these phases suitable for AS-LIBs. Joint structure refinements using high-resolution neutron and laboratory X-ray diffraction provide insight into the influence of disorder on the fast ionic conductivity. Besides the disorder in the lithium distribution, it was the disorder in the S2−/Cl− or S2−/Br− distribution that was found to promote ion mobility, whereas the large I− could not be exchanged for S2− and the resulting more ordered Li6PS5I exhibits only a moderate conductivity. Li+ ion migration pathways in the crystalline compounds were modelled using the bond valence approach to interpret the differences between argyrodites containing different halide ions.

Variation in Structure and Li+-Ion Migration in Argyrodite-Type Li6PS5X (X = Cl, Br, I) Solid Electrolytes. P.R.Rayavarapu, N.Sharma, V.K.Peterson, S.Adams: Journal of Solid State Electrochemistry, 2012, 16[5], 1807-13