Solvent-Free Approach for Interweaving Freestanding and Ultrathin Inorganic Solid Electrolyte Membranes

Abstract

All-solid-state batteries (ASSBs) have gained considerable attention due to their inherent safety and high energy density. However, fabricating ultrathin and freestanding solid electrolyte membranes for practical all-solid-state pouch cells remains challenging. In this work, polytetrafluoroethylene (PTFE) fibrilization was utilized to interweave inorganic solid electrolytes (SEs) into freestanding membranes. Representative SE membranes, including Li₆PS₅Cl, Li₃InCl₆, and Li_6.5La₃Zr_1.5Ta_0.5O₁₂, demonstrate not only a thickness of 15–20 μm but also high room-temperature ionic conductivity (>1 mS cm^–1). All-solid-state pouch cells with bilayer Li₆PS₅Cl and Li₃InCl₆ membranes deliver a high capacity of 124.3 mAh g^–1 at 0.1 C and an initial Coulombic efficiency of 89.4%. Furthermore, using a 20 μm LLZTO membrane as a ceramic separator, a solid-state pouch cell with a high-capacity LiNi_0.8Mn_0.1Co_0.1O₂ electrode (>3 mAh cm^–2) displays both exceptional cycling stability and unprecedented safety. We believe that this solvent-free technology would be a feasible and cost-effective means of transferring ASSB technology from the laboratory to the factory.