Electrochemical Performance and Stability of Li 7 Si 2 S 7 I Solid Electrolytes in Solid-State Battery Cathode Composites

Résumé fourni par la source

The development of solid electrolytes (SEs) for high-performance solid-state batteries (SSBs) requires not only favorable electrochemical stability but also interfacial compatibility with diverse cathode chemistries. In this study, we systematically benchmark recently discovered Li 7 Si 2 S 7 I against the well-established argyrodite Li 5.5 PS 4.5 Cl 1.5 as an SE in composite cathodes. Despite exhibiting comparable oxidative stability, Li 7 Si 2 S 7 I demonstrates markedly different behaviors depending on the cathode chemistry. In composite cathodes with uncoated LiNi 0.83 Co 0.11 Mn 0.06 O 2 as the cathode active material and Li 7 Si 2 S 7 I as the electrolyte, rapid degradation occurs, with capacity retention dropping to 5% after 30 cycles, driven by fast degradation kinetics and interfacial instability toward the formation of SiO x species as a thermodynamic sink. In contrast, sulfur–carbon–Li 7 Si 2 S 7 I composite cathodes show good performance in half-cells, comparable to that of the argyrodite benchmark. The reversible oxidative redox processes of Li 7 Si 2 S 7 I in sulfur-based systems highlight its promise for Li–S and other oxygen-free battery chemistries. Overall, this work emphasizes the importance of a holistic approach to SE evaluation, integrating chemical and electrochemical stability with degradation kinetics, to inform the rational design of next-generation SSB materials.