A leaf-like Al₂O₃-based quasi-solid electrolyte with a fast Li⁺ conductive interface for stable lithium metal anodes

Poor interfacial contact and Li dendritic growth severely restrict practical applications of Li metal anodes. Herein, we report a novel biomimetic solid-state electrolyte based on injection of 1 M LiTFSI-Py13TFSI ionic liquid electrolyte into a leaf-like Al₂O₃ skeleton through an in situ sol-gel method. This structure is intended to address the poor contact at the interface and protect the Li metal anode. A large amount of ionic liquid electrolyte was absorbed by the leaf-like Al₂O₃ skeleton owing to its high specific surface area. This system improved the ionic conductivity and promoted migration of Li⁺ both in the bulk and at the interface. The lithiophilic Al₂O₃ skeleton was in close contact with metallic Li and formed a fast Li⁺ conductive layer (Li-Al-O composition), which facilitated uniform deposition of Li and thus inhibited Li dendrite formation during long-term cycling. Moreover, density functional theory calculations indicated spontaneous generation of a Li-Al-O layer and [Py13]⁺ in the ionic liquid facilitates this process. Symmetric Li cells assembled with this electrolyte exhibited an extremely long cycle lifetime of 1100 h at a high constant current density. This strategy of a biomimetic leaf-structured electrolyte with a Li-Al-O conductive layer at the interface addresses problems of solid-state Li metal batteries and provides an alternative system for practical applications.