Enhanced Li-Ion Transport in Ceramic/Polymer Electrolytes via Interfacial Molecular Bridging

The widespread adoption of composite solid electrolytes (CSEs) in solid-state lithium metal batteries has been significantly impeded by insufficient room-temperature ionic conductivity, primarily due to high energy barriers for Li-ion transport across ceramic/polymer interfaces. While interfacial modification has emerged as a key strategy, the structural and mechanistic principles governing efficient ion transport remain poorly understood. Here, we address this challenge through an innovative interface engineering approach, constructing a molecular bridge between Li7La3Zr2O12 nanofibers (LLZO NFs) and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) using a 3-(methacryloyloxy)propyltrimethoxysilane (MPS) linker. This design achieves multiple synergistic effects: (1) robust chemical bonding enables uniform dispersion of ceramic nanofibers even at high loadings (60 wt %); (2) polar MPS moieties effectively adsorb and reorganize solvated species at the ceramic/polymer interface; and (3) optimized Li+ coordination via dual bonding configurations (Li···O═C with MPS and Li···F–C with PVDF-HFP) drastically reduces the interfacial energy barrier (−0.456 eV), creating continuous ion transport highways across the interface. Systematic investigation of the linker’s structure–property relationship reveals key design principles for interfacial chemistry. The resulting composite electrolyte (CLPH–OH) with 60 wt % of functionalized LLZO NFs delivers an exceptional ionic conductivity of 8.3 × 10–4 S cm–1 at room temperature. Remarkably, Li//CLPH–OH//Li symmetric cells achieve stable cycling for 2000 h at 0.1 mA cm–2, and LiFePO4 full cells retain 93.6% capacity after 300 cycles at 0.5 C. This study provides both fundamental insights into interfacial ion transport mechanisms and a strategy for designing high-performance solid-state electrolytes through precise molecular-level interface engineering.