Enhancing Rate Capability and Interfacial Durability of Graphite Anodes in Sulfide-Based All-Solid-State Batteries via Atomic Layer Deposition

The practical application of graphite anodes in sulfide-based all-solid-state lithium-ion batteries is hindered by their poor charging rate capability and interfacial instability caused by the reductive decomposition of solid electrolytes. To address this, we systematically investigated the impact of ultra-thin surface modifications on graphite using atomic layer deposition. Four materials with distinct electronic and lithium-ion conductivities, LiF, Al2O3, TiO2, and Li3PO4, were deposited on graphite powder. While all the modifying materials effectively reduced the initial irreversible capacity by suppressing solid electrolyte reduction, TiO2 and Li3PO4 significantly improved the charging rate capability owing to their high lithium-ion conductivities. Furthermore, extended floating tests revealed that the Li3PO4 modification uniquely maintained its enhanced rate capability, whereas the TiO2-modified graphite suffered from kinetic degradation. Because Li3PO4 is an electronic insulator, it effectively restricts the continuous reduction of the solid electrolyte compared to TiO2, which becomes electronically conductive upon lithiation. This study demonstrates that surface modification with a material that is simultaneously an electronic insulator and lithium-ion conductor is crucial for achieving high rate capability and interfacial durability in all-solid-state batteries.