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

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 LiFePO₄||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.