Fabrication of the Li6PS5Cl–LiFSI Composite for All-Solid-State Li-Ion Batteries

The ionic conductivity of an argyrodite-type solid electrolyte Li 6 PS 5 Cl can be improved by aliovalent substitution. Although the ionic conductivity of Li 6 PS 5 Cl has been intensively studied, its electrochemical stability enhancement was rarely reported. In this study, Li 6 PS 5 Cl–LiFSI composite solid electrolytes were prepared to study the effect of LiFSI addition on the stability of Li 6 PS 5 Cl in low- and high-voltage regions. The structure of the prepared solid electrolytes was characterized using XRD, Raman spectroscopy, and SEM-EDS. Rietveld refinement was further employed to confirm their structure. The component-dependent oxidation and electrochemical compatibility of the prepared solid electrolytes were studied by linear sweep voltammetry (LSV) and cyclic voltammetry (CV). The Li–Li symmetrical cell using the 80Li 6 PS 5 Cl–20LiFSI composite was stable for about 500 h when being periodically charged–discharged at ±0.1 ∼± 0.8 mA cm –2 . The capacity and stability of solid-state cells, which employed 80Li 6 PS 5 Cl–20LiFSI and 90Li 6 PS 5 Cl–10LiFSI, were superior to the one using Li 6 PS 5 Cl when being cycled at a high voltage of about 4.0–2.4 V vs Li–In, which was about 4.6–3.0 V vs Li/Li + .