AC conductivity study of mechanochemically synthesized solid electrolytes of Li_6-MPS₅Cl (M = Ca, Mg, Ba, Zn, Al, Y)

Argyrodite-type solid electrolytes of Li₆PS₅Cl doped with multivalent cations (Mg²⁺, Ba²⁺, Zn²⁺, Al³⁺, Y³⁺) were prepared via a mechanochemical synthesis method. The lattice constant (a₀), interplanar spacing (d₂₂₀, d₃₁₁, d₂₂₂), and micro-strain (ε) showed that the doping elements were incorporated into the crystal structure of Li₆PS₅Cl. The lattice constant and interplanar spacing of the doped samples were smaller than those of Li₆PS₅Cl. The prepared samples exhibited a positive lattice strain, and the substituted samples exhibited higher strains than Li₆PS₅Cl. The doped samples exhibited higher ionic conductivity than Li₆PS₅Cl at 25 °C. Li_5.94Al_0.02PS₅Cl exhibited the highest σ_DC of approximately 2.36 × 10^-3 S cm^-1 at 25 °C. The charge carrier movement at the grain boundary changing from long-range diffusion in Li₆PS₅Cl to short-range diffusion in Li_5.94Al_0.02PS₅Cl enhanced the conductivity.