Lanthanide Orbital Modulation Coupled With Entropy Increase Effect for Synergistically Enhanced Interfacial Stability and Ion Transport Kinetics in Halide Electrolytes

The development of solid‐state electrolytes (SSEs) integrating high ionic conductivity and a wide electrochemical window constitutes a critical challenge for all‐solid‐state lithium batteries (ASSLBs). Herein, we propose a multication mixing strategy of lanthanide elements, which introduces configurational entropy increase effect and electronic structure regulation into the Li 3 YCl 6 , achieving simultaneous enhancement of ion transport and oxidation resistance. Combined theoretical and experimental analyses verify that the entropy increase–driven local structural distortions effectively reduce the energy barrier for Li + migration and optimize ion‐transport pathways. Concurrently, the unique electronic structure regulation of rare earth elements stabilizes the chemical environment of Cl − , significantly improving the intrinsic oxidation resistance. The full battery employing this optimized electrolyte demonstrates remarkable stability at 4.5 V, maintaining a capacity retention ratio of 74.3% after 800 cycles at 1 C rate. This research provides innovative insights into designing advanced SSEs through entropy increase effect and electronic structure design.