A wrapped and infiltrated ∼20-μm-thick 3D ceramic framework composite enables fast Li+ diffusion and interfacial compatibility for lithium-metal batteries

Composite polymer electrolytes (CPEs) have shown potential for energy-dense Li-metal batteries (LMBs), but CPEs have always encountered poor ionic conductivity, low Li+ transference ability, and dendrite propagation. In our work, a mechanically robust three-dimensional porous framework (3DPF) with a thickness of ∼21 μm was successfully prepared by tape-casting and firing Li6.75La3Zr1.75Ta0.25O12 (LLZTO). After wrapping and infiltrating poly(vinylidene fluoride) (PVDF)−salt (LiTFSI)−LLZTO solution to 3DPF (3DPF-PVDF-LLZTO) for subsequent solidification, the resultant composite electrolyte (∼22 μm) shows an excellent room-temperature ionic conductivity of 1.67 × 10−4 S cm−1 and an extremely high Li+ transference number of 0.82, indicating fast Li+ diffusion. Furthermore, 3DPF-PVDF-LLZTO exhibits a mechanical strength of 37.5 MPa, and the assembled Li|3DPF-PVDF-LLZTO|Li cell ensures stable operation at 1.0 mA cm−2 and presents prolonged cycling stability at 0.2 mA cm−2 over 800 h without exhibiting dendrites, demonstrating excellent interfacial compatibility. A Li|3DPF-PVDF-LLZTO|LiFePO4 battery delivers excellent room-temperature cycle stability and rate capability, with an initial capacity of 160.7 mAh g−1 at 0.2 C and 115.3 mAh g−1 over 450 cycles at 1.0 C. This work provides a practical strategy for constructing highly conductive composite electrolytes with electrode−electrolyte compatibility for LMBs and deepens our understanding of Li+ diffusion pathways.