High ionic conductivity Li₇P₂S₈I solid electrolyte has been the subject of much attention among sulfide-based solid electrolytes as it has been known so far. Among them, oxygen-doped Li₇P₂S₈I solid electrolyte was fabricated by a high-capacity energy milling process. Their crystal structures and the role of doping in controlling the crystal structure were analyzed by partial X-ray diffraction techniques and laser-assisted spectroscopy. The structural analysis results showed that oxygen doping greatly influenced the electrochemical performance as a central crystal on the left and right sides. Among all oxygen-doped solid electrolytes, Li₇P₂S₈I_0.8O_0.1 solid electrolyte showed the highest ionic conductivity of 4.5 mS/cm at room temperature. Cyclic voltammetry and DC polarization analysis were performed to study the stability of the solid electrolyte on lithium metal anode. The fabricated solid electrolyte showed high stability on lithium metal anode. Li₇P₂S₈I_0.8O_0.1 solid electrolyte showed high critical current density and long DC cycle stability. The calculated critical current density of the fabricated Li₇P₂S₈I_0.8O_0.1 solid electrolyte was 0.75 mA/cm². It was stable up to 350 cycles at a constant current density of 0.1 mA/cm². The fabricated Li₇P₂S₈I_0.8O_0.1 solid electrolyte-based ASSB exhibited a high specific capacity of 170.9 mAh/g, Coulombic efficiency of 72.9%, and charge–discharge cycling stability retention of 93.8% after 100 cycles. The charge–discharge analysis results demonstrated that the oxygen-doped Li₇P₂S₈I solid electrolyte exhibited better electrochemical performances than the bare Li₇P₂S₈I solid electrolyte.

Rajesh Rajagopal

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