Diversifying\nIon-Transport Pathways of Composite Solid\nElectrolytes for High-Performance Solid-State Lithium-Metal Batteries

Abstract

The application of composite solid\nelectrolytes (CSEs) in solid-state\nlithium-metal batteries is limited by the unsatisfactory ionic conductivity\nunderpinned by the low concentration of free lithium ions. Herein,\nwe propose an interface design strategy where an amine silane linker\nis employed as a coupling agent to graft the Li₇La₃Zr₂O₁₂ (LLZO) ceramic nanofibers to\nthe poly(vinylidene fluoride-<i>co</i>-hexafluoropropylene)\n(PVDF-HFP) polymer matrix to enhance their interaction. The hydrogen\nbonding between amino-functionalized LLZO (NH₂@LLZO) and\nPVDF-HFP not only effectively induces a uniform incorporation of high-content\nnanofibers (50 wt %) into the polymer matrix but also furnishes sufficient\ncontinuous surfaces to weaken the complexation between PVDF-HFP and\nLi-ion carriers. Additionally, introduction of the hydrogen bond and\nLewis acid–base interplay strengthens the interfacial interactions\nbetween NH₂@LLZO and lithium salts that release more free\nlithium ions for efficient interfacial transport. The impact of the\nlinker’s structure on the dissociation capacity of lithium\nsalts is systematically studied from the steric effect perspective,\nwhich affords insights into interface design. Conclusively, the composite\nsolid electrolyte achieves a high ionic conductivity (5.8 × 10^–4 S cm^–1) by synergy of multiple\ntransport channels at ceramic, polymer, and their interface, which\neffectively regulates the lithium deposition behavior in symmetric\ncells. The excellent compatibility of the electrolyte with both LiFePO₄ and LiNi_0.8Co_0.1Mn_0.1O₂ cathodes also results in a long lifetime and a high rate\ncapability for full cells.