In-situ construction of a LiI@Li-Bi composite interlayer for stable Li|LATP interface in solid-state lithium batteries

BiI 3 drop-casting method is applied to prepare B-LATP electrolyte. • The addition of BiI 3 reduces interfacial resistance. • The addition of BiI 3 enhances the lithiophilicity of the material. • B-LATP achieves a critical current density of 3.7 mA cm −2 . NASICON-type Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) solid-state electrolyte (SSE) is considered a promising candidate for solid-state lithium metal batteries (SLMB) due to its high room-temperature, Li-ion conductivity and superior air stability. However, its practical application is hindered by electro-chemo-mechanical degradation at the Li|LATP interface, including lithium dendrite penetration and poor physical contact. Rational interfacial design from a chemical compatibility synergistic perspective is therefore imperative. Herein, we report the in-situ construction of a multifunctional LiI@Li-Bi composite interlayer at the Li|LATP interface via a conversion reaction between a BiI 3 thin film and lithium metal. This tailored interlayer consists of electronically insulating LiI and a lithiophilic Li–Bi alloy. It effectively improves interfacial contact, reduces interfacial resistance, suppresses side reactions, and homogenizes Li-ion flux, thereby inhibiting dendrite growth. The Li|B-LATP|Li symmetric cell achieves a critical current density of 3.7 mA cm −2 and maintains stable cycling for over 600 h at 0.1 mA cm −2 . Furthermore, the LiFePO 4 |B-LATP|Li solid-state full cell exhibits stable cycling performance at 0.1 C and room temperature. These results highlight the critical role of rational Li|LATP interface design and provide a facile strategy for optimizing interfacial compatibility and addressing interfacial challenges in SLMBs. This simple method utilizes a conversion reaction between a BiI 3 thin film and Li metal to in-situ form a LiI@Li-Bi composite interlayer on LATP. The resulting interlayer improves interfacial contact, enhancing cycling stability of both symmetric and full cells. Download: Download high-res image (219KB) Download: Download full-size image