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

Abstract 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. BiLi 3 /LiCl 3 interlayer with a double‐layer structure is constructed by modulating the cooling rate. The LiCl 3 enriched on the electrolyte side exhibits extremely low electronic conductivity, effectively blocking electrons and preventing electrolyte attack. On the anode side, the BiLi 3 ‐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 .