The argyrodite solid electrolyte has been actively studied
due
to its high ionic conductivity and good physical properties. However,
it has various problems due to low air stability characteristics and
low critical current density. In this study, the air stability and
electrochemical performance of the solid electrolyte were improved
by introducing a method to improve the performance of the solid electrolyte
by adding excess iodine based on a thioantimonate-based argyrodite
solid electrolyte with excellent air stability. I-rich glass-ceramic
argyrodite Li6–x
SbS5–x
I
x
was prepared through
high-energy ball milling. The structural properties were confirmed
using powder X-ray diffraction (XRD). The synthesized Li5.6SbS4.6I1.4 electrolyte showed a higher ionic
conductivity of 0.66 mS/cm and a lower activation energy of 0.32 eV
compared to pristine Li6SbS5I (0.17 mS/cm, 0.33
eV) at 25 °C. In addition, the high lithium compatibility of
the Li5.6SbS4.6I1.4 solid electrolyte
was confirmed through DC cycling and cyclic voltammetry, and it showed
a high ion conductivity retention rate of 61% after exposure to the
atmosphere for 30 min. Finally, the optimized cell with Li6PS5Cl–Li5.6SbS4.6I1.4 solid electrolyte showed a higher initial discharge capacity of
154 mAh/g and Coulombic efficiency of 70%. In particular, it was confirmed
that the performance at a high C rate was greatly improved compared
to the cell made with Li6PS5Cl.