Synergistic Alloying-Ferroelectric Ag-BST Layer for Enhanced Li|LATP Interface Stability and Ion Transport

Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) with a sodium superionic conductor structure has attracted significant attention in recent years owing to its excellent chemical stability and outstanding electrochemical performance. However, direct contact with lithium metal leads to severe interfacial reactions and dendrite penetration, which can be further accelerated under aggressive conditions of fast-charging, hindering its application in solid-state lithium metal batteries (SSLMBs). In this study, we propose a dual-interface engineering strategy to address these challenges. By adopting a magnetron sputtering method, a high-dielectric-constant Ba_0.5Sr_0.5TiO₃ (BST) layer deposited homogenizes the interfacial electric field distribution, while an Ag layer reacts with lithium during cycling to <i>in situ</i> form a Li-Ag alloy, reducing the lithium nucleation overpotential and guiding uniform lithium deposition. This synergistic modification effectively suppresses dendrite formation, enabling symmetric cells to achieve an ultralong cycling lifespan of over 7000 h at 0.1 mA(h) cm^-2, with high critical current densities of 2.6 mA cm^-2 (constant-time mode) and 3.0 mA cm^-2 (constant-capacity mode). Furthermore, the modified full-cells retain 63.9% of initial capacity after 1000 cycles at 0.5 C. This work provides an effective interfacial design strategy for the development of safe and durable SSLMBs.