Tuning of Li-argyrodites ionic conductivity through silicon substitution (Li6+xP1-xSixS5Cl0.5Br0.5) and their electrochemical performance in lithium solid state batteries

AC conductivity study of mechanochemically synthesized solid electrolytes of Li6-aMa/nnPS5Cl (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. Li5.94Al0.02PS5Cl exhibited the highest σDC 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 Li5.94Al0.02PS5Cl enhanced the conductivity.