o-UiO-66-F4 modified poly(1,3-dioxolane)-based quasi-solid-state composite electrolyte for stable interfaces and safer sodium metal batteries.

Sodium metal batteries are promising candidates for next-generation energy storage, while their practical deployment is limited by unstable electrode/electrolyte interfaces and fire-safety risks. Herein, a composite electrolyte (denoted as UFQSE) featuring multi-channel Na+ transport pathways and interfacial stability is fabricated via in situ polymerization. The thermally activated o-UiO-66-F4 triggers the ring-opening polymerization of 1,3-dioxolane through its coordinatively unsaturated Zr4+ sites and induces the uniform formation of NaF-rich solid electrolyte interphase. Moreover, the abundant Na+ transport channels and TFSI- anchoring sites in o-UiO-66- F4 facilitate Na+ migration and suppress dendrite growth by mitigating anion polarization. Additionally, the Lewis acid-base interaction between o-UiO-66- F4 and poly(1,3-dioxolane) chains weakens Na+ coordination, enhancing salt dissociation and ionic mobility. Benefiting from this synergistic solvation-structure regulation, UFQSE achieves an ionic conductivity of 7.28 mS cm-1, a Na+ transference number of 0.76, and an electrochemical stability window of 5.08 V at room temperature. The Na|Na symmetric cells exhibit stable cycling over 3600 h, and the Na|Na3V2(PO4)3 cells deliver durable performance for 450 cycles at a high mass loading of 10 mg cm-2 and remain stable over 515 cycles at 5C. Notably, the UFQSE-based pouch cells operate reliably under both mechanical and thermal abuse. This work provides a practical and effective strategy for developing high-safety and high-performance sodium metal batteries.