Chain-segment ferry engineering from anchoring anion of the composite solid electrolyte enables fast lithium ion transport

The composite solid electrolyte (CSE) is an ideal material for high-energy density solid-state lithium metal batteries. However, incompatibility between interfaces, and the free movement of anions in the polymer matrix result in severe concentration polarization, resulting in slow interfacial transport of Li⁺. Herein, a composite solid electrolyte (PEO/LiTFSI/Al₂O₃@PDA) was prepared by coating PDA on Al₂O₃ surface as a functional filler. Li⁺ travel the elaborately built polymer matrix, of which PDA as transport channel pulls Li⁺ migration, Al₂O₃ as ferry position regulate the Li⁺ flow. At the same time, PDA bifunctional surface coating can anchor anions, promote the decomposition of lithium salts, form more free lithium ions, weaken the complexation of PEO and Li⁺, and improve the transmission of Li⁺ at the ceramic/polymer interface. This work provides a reasonable design strategy for breaking through the limitations of composite solid-state electrolytes, which are also applicable to other composite solid-state electrolyte systems.