fig8

Figure 8. (A) (left) The crystal structure of Li₆PS₅I. (right) A face-shared S₃I₂ double tetrahedron with two distinct lithium-ion equivalent sites^[23]. Reproduced with permission^[23]. Copyright 2008, Wiley-VCH GmBH; (B) A simplified tetrahedron type in the argyrodite structure, where light gray represents PS₄ groups (type 0) and dark gray indicates lithium-containing tetrahedron types (types 1-5)^[131]. Reproduced with permission^[131]. Copyright 2010, Wiley-VCH GmBH; (C) (upper left) Lattice parameters of Li_6-xPS_5-xCl_1+x as a function of x. (upper right) Impedance plots at room temperature of Li₆PS₅Cl, Li_5.75PS_4.75Cl_1.25, Li_5.5PS_4.5Cl_1.5, and a sintered Li_5.5PS_4.5Cl_1.5. (lower left) Nyquist and Arrhenius plots for Li_5.5PS_4.5Cl_1.5. (lower right) Ionic conductivity and activation energy for Li_6-xPS_5-xCl_1+x (x = 0, 0.25, 0.375, 0.5)^[77]. Reproduced with permission^[77]. Copyright 2019, Wiley-VCH GmBH; (D) (upper left) Crystal structure of Li_6.7Si_0.7Sb_0.3S₅I. (lower left) Three distinct lithium ion diffusion pathways: the doublet jump (blue arrow), the intra-cage jump (red arrow), and the inter-cage jump (orange arrow). (upper right and lower left) The crystal structure of Li₆PS₅I is shown for comparison, with no additional lithium ions in the structure^[24]. Reproduced with permission^[24]. Copyright 2019, American Chemical Society; (E) (left) Two distinct lithium-ion cages, defined by their radius from isolated S^2- ions, are influenced by the Br^-/S^2-site disorder, and corresponding (right) lithium-ion diffusion pathways^[133]. Reproduced with permission^[133]. Copyright 2021, Wiley-VCH GmBH; (F) (left) The activation energy and Arrhenius prefactor as functions of X in Li₆PS₅X (X = Cl, Br, I). (right) The ionic conductivity as a function of X in Li₆PS₅X (X = Cl, Br, I)^[36]. Reproduced with permission^[36]. Copyright 2017, American Chemical Society.