RESUMEN
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.
RESUMEN
Li7P3S11 doped with CaX2 (X = Cl, Br, I) and LiI solid electrolytes were successfully prepared by liquid-phase synthesis using acetonitrile as the reaction medium. Their structure was investigated using XRD, Raman spectroscopy and SEM-EDS. The data obtained from complex impedance spectroscopy was analyzed to study the ionic conductivity and relaxation dynamics in the prepared samples. The XRD results suggested that a part of CaX2 and LiI incorporated into the structure of Li7P3S11, while the remaining part existed at the grain boundary of the Li7P3S11 particle. The Raman peak positions of PS43- and P2S74- ions in samples 90Li7P3S11-5CaI2 and 90Li7P3S11-5CaI2-5LiI had shifted as compared to the Li7P3S11 sample, showing that CaI2 addition affected the vibration of PS43- and P2S74- ions. EDS results indicated that CaI2 and LiI were well dispersed in the prepared powder sample. The ionic conductivity at 25 °C of sample 90Li7P3S11-5CaI2-5LiI reached a very high value of 3.1 mS cm-1 due to the improvement of Li-ion movement at the grain boundary and structural improvement upon CaI2 and LiI doping. This study encouraged the application of Li7P3S11 in all-solid-state Li-ion batteries.