A Sub‐1 Nm Cluster Chains‐enhanced Poly(ethylene oxide) Electrolyte for an All‐solid‐State Lithium Metal Battery with a Long Cycling Lifespan

Abstract Flexible composite polymer electrolytes (CPEs) are promising candidates for high‐energy all‐solid‐state lithium metal batteries, owing to their superior processability, excellent electrochemical performance, and enhanced safety. Nevertheless, conventional CPEs face challenges such as lithium‐ion blocking and aggregation from inert fillers, hindering ion transport. To address these issues, highly dispersed materials need optimization in polymer matrices. In this study, a new strategy is introduced to introduce sub‐1 nm inorganic cluster chains into poly(ethylene oxide) based electrolytes. These ultra‐thin highly dispersed cluster chains eliminated the Li blocking region and aggregation‐induced barrier, formed a 3D network, and realized the efficient conductivity of Li + . By engineering La vacancies into the cluster chains of Ta‐doped LaOOH crystals, low‐energy migration pathways are created. This optimized electrolyte achieves the ionic conductivity of 0.65 mS cm − 1 at 60 °C and the lithium transference number of 0.47. Electrochemical testing shows outstanding stability: Li||LTPE||Li symmetric cells maintain stable Li plating and stripping for 2000 h, and LiFePO 4 ||LTPE||Li cells achieve 138.5 mAh g −1 with 93.4% capacity retention after 2000 cycles at 2C. Furthermore, the pioneering application of in situ conductive atomic force microscopy enables unprecedented characterization of temperature‐dependent morphological evolution and heterogeneous ion transport dynamics in solid electrolytes.