Abstract
Developing safe and high‐energy solid‐state lithium metal batteries (LMBs) remains challenging due to the need to simultaneously achieve ultrathin electrolyte membranes, fast ion transport, and mechanical robustness. Herein, we report a scalable 19 μm composite electrolyte based on a porous PTFE scaffold, a PEO/LiTFSI matrix, and LiClO
4
‐associated UiO‐66‐NH
2
as a functional filler. In this metal–organic framework (MOF)‐assisted dual‐salt regulation strategy, LiTFSI is dispersed in the polymer matrix, while LiClO
4
is pre‐associated with the amino‐functionalized UiO‐66 to regulate the local Li
+
environment. The synergistic effects of the MOF filler and dual salts reduce PEO crystallinity and promote more efficient Li
+
transport. The porous PTFE scaffold further enables membrane thinning and mechanical reinforcement. As a result, the electrolyte exhibits an ionic conductivity of 2.19 × 10
−4
S cm
−1
at 60 °C, an electrochemical stability window of 4.6 V, a Li
+
transference number () of 0.69, and a tensile strength of 70 MPa. LiFePO
4
cells deliver stable cycling with 97% capacity retention after 160 cycles, and good rate capability and compatibility with high‐voltage NCM523 cathodes are also demonstrated. This work provides a practical MOF‐assisted ion‐regulation strategy for designing ultrathin and mechanically robust polymer electrolytes for advanced solid‐state batteries.