Multifunctional Double Layer Based on Regional Segregation for Stabilized and Dendrite-Free Solid-State Li Batteries

The Li dendrite problem triggered by the inhomogeneous deposition of Li and the reduction of Li⁺ in the electrolyte has seriously hindered the practical application of garnet-based solid-state batteries. To address this issue, a multifunctional double layer (MDL) based on the phenomenon of segregation during welding is introduced between the garnet and the Li anode. BiLi₃/LiCl₃ interlayer with a double-layer structure is constructed by modulating the cooling rate. The LiCl₃ enriched on the electrolyte side exhibits extremely low electronic conductivity, effectively blocking electrons and preventing electrolyte attack. On the anode side, the BiLi₃-enriched layer regulates local current distribution, ensuring uniform deposition/exfoliation of Li and preventing dendrite formation at the interface. Furthermore, this welding-based preparation method achieves a strong and secure connection between the metal electrode and the ceramic electrolyte. Hence, this Li|LLZTO-MDL|Li battery with double-layer special structural interfacial modification can realize a high critical current density of 2.9 mA cm⁻² and can be stably cycled for more than 10 000 h at 0.3 mA cm⁻².