Thin Polymer Electrolytes with 3D Nanofiber SkeletonsEnabling High-Performance Solid-State Lithium Metal Batteries

Polymer electrolytes are extensively utilized in solid-state batteries due to their high flexibility, excellent interfacial contact with the electrodes, and low cost. However, they suffer from issues such as large thickness, low room-temperature ionic conductivity, and poor mechanical properties. In this study, we employ an environmentally friendly and straightforward vacuum filtration method to obtain a thin poly­(ethylene oxide) (PEO)–aramid nanofiber (ANF)–LiTFSI composite electrolyte film with a small thickness of 25–42 μm. Compared with the solution-casting method, the rapid vacuum filtration process leads to the formation of a 3D interpenetrating ANF network structure and also a continuous ion conduction pathway at the PEO/ANF interfaces. Consequently, the thin composite electrolyte exhibits a high room-temperature ionic conductivity of 3.27 × 10^–5 S cm^–1 and a high strength of 5.19 MPa, which is 26 times that of the solution-casted PEO–LiTFSI electrolyte. Furthermore, the thin electrolyte shows excellent lithium dendrite suppression capability, and the thin electrolyte-containing lithium metal batteries deliver a capacity retention of 78% after 180 cycles with an average Coulombic efficiency of 99.9%. The thin electrolyte with the 3D nanofiber skeleton developed in this work possesses great potential for high-performance lithium metal batteries.