Unveiling Lithium-Solid Electrolyte Interface Evolution in All-Solid-State Batteries through Operando Characterizations

All-solid-state lithium metal batteries are projected to offer one of the highest specific energy among rechargeable batteries, positioning them as a front-runner for electric vehicle applications. Lithium metal anodes outperform conventional graphite anodes in terms of cell-level energy density. However, ensuring a conformal metal–electrolyte contact is a great challenge. In this presentation, I will illustrate the use of operando tools to understand issues like void formation and contact loss at the Li–electrolyte interface in all-solid-state batteries. I will first showcase a study where the Li-Mg alloy anode suppresses void growth. Operando scanning electron microscopy reveals voids coalescing into a gap at the pure-Li–electrolyte interface, but large voids split into smaller voids and collapse to ensure contact between Li-Mg alloy anode and solid electrolyte. This behavior is further supported by density function theory calculations, emphasizing the role of strong Mg-S interaction at the electrolyte interface in repelling vacancies and mitigating void formation. In the second example, I will introduce an interlayer strategy optimizing contact between the solid electrolyte and lithium metal, which enhances stripping/plating uniformity and suppress lithium dendrite formation.