Novel silicon-based solid-state electrolytes Li2SiI4O based on theoretical calculation prediction

All-solid-state batteries (ASSBs) require solid electrolytes with both high ionic conductivity and favorable mechanical properties to maintain intimate interfacial contact with electrode particles during cycling. Herein, we report a new silicon-based solid electrolyte, Li 2 SiI 4 O, designed through theoretical calculations and subsequently synthesized experimentally. For an ideal amorphous deep-eutectic Li 2 SiI 4 O system, theoretical calculations predict a Young’s modulus below 5 GPa, suggesting excellent mechanical compliance and potential plasticity. Indeed, the experimentally synthesized Li 2 SiI 4 O exhibits a Young’s modulus of 19.8 GPa, lower than that of typical sulfide solid electrolytes with Young’s modulus of approximately 23 GPa. This relatively low modulus is expected to improve interfacial contact between the active electrode materials and the solid electrolyte, resembling the conformal contact commonly observed at solid–liquid interfaces. Electrochemical impedance spectroscopy measurements show that Li 2 SiI 4 O exhibits an ionic conductivity of 1.23 × 10 –4 S/cm at room temperature. When employed as the solid electrolyte in ASSBs, the assembled cells deliver stable cycling performance with 80% capacity retention after 800 cycles. These results demonstrate that Li 2 SiI 4 O is a promising solid electrolyte candidate for practical ASSBs by combining favorable mechanical compliance with stable electrochemical performance.