How Interfacial Chemo-Mechanical Properties Govern Lithium Transport and Lifetime of Cathode Particles in All-Solid-State Batteries

All-solid-state batteries differ from conventional liquid-electrolyte secondary batteries in that they form uneven solid-solid interfaces between the solid electrolyte and electrode particles. At these interfaces, chemical side reactions can occur, and the physical contact area is irregular. Lithium ions insert through the active surface area at the interface, and when localized expansion or contraction of electrode particles occurs, the solid electrolyte—due to its mechanical rigidity—imposes stress on the solid electrode particles. This stress, combined with chemical side reactions at the interface, alters the internal chemical potential, impacting both the active surface and lithium transport.

In this study, we observed lithium transport within single-crystal and polycrystalline particles in real time in all-solid-state batteries, visualizing the strain fields within particles in three dimensions. By systematically tuning the mechanical properties and chemical stability of the solid electrolyte, we investigated how these factors influence lithium transport and strain. This approach enabled us to decouple and independently examine the chemical reactions and mechanical properties within the all-solid-state battery system. Additionally, we explored the implications of these interface phenomena on the lifespan and performance of secondary batteries, providing insights that are crucial for advancing all-solid-state battery technology