In Situ Formed Lithiated Iron Chloride Nanoanchors for Reinforcing Cathode/Electrolyte Interfaces in All‐Solid‐State Batteries

Abstract A critical challenge for chloride‐based all‐solid‐state batteries (ASSBs) is the limited lithium‐ion transport at the cathode/electrolyte interface, driven by stress‐induced cracks from cathode material volume changes, poor spatial distribution of active materials and solid electrolyte (SE) particles, and low stack pressure. In this study, an innovative design of island‐like nanoanchors on the high‐nickel cathode (NCM) surface is proposed to mechanically suppress the interfacial crack formation and propagation and electrochemically enhance Li + transport. These nanoanchors, formed via in situ lithiation of iron chloride (LFC), possess a low elastic modulus, Li + conductivity, and electrochemical activity and are prepared using a simple physical vapor deposition method. The multifunctional LFC nanoanchors not only improve SE coverage on the NCM surface from mixing to pressing but also maintain stable physical contact throughout cycling, thereby reinforcing lithium‐ion transport and lithiation‐delithiation interactions at the NCM/SE interface. As a result, the LFC‐coated NCM (F@NCM)‐based battery demonstrates excellent rate performance and capacity retention (90.2% after 200 cycles) under low stack pressure (≈5 MPa). This scalable and practical strategy provides a promising solution for optimizing cathode interfaces, marking a significant advancement in the development of high‐performance ASSBs.