Synergistic enhancement: Dual role of protonated metal-organic frameworks in ion transport and interfacial stability within polymer electrolyte

Developing solid-state polymer electrolytes (SPEs) with fast Li + transport and stable electrode interfaces is essential for high-performance lithium metal batteries. Herein, a protonated amino-functionalized metal-organic framework (pro-UiO66) is incorporated into a PEO-LiTFSI matrix to construct composite SPEs. Protonation introduces abundant TFSI − adsorption sites(-NH 3 + ), while the three-dimensional porous framework disrupts PEO crystallinity and provides angstrom-scale pathways for Li + migration. Various characterization confirms that pro-UiO66 maintains crystallinity and uniform dispersion in the polymer matrix. The optimized electrolyte containing 10 wt% pro-UiO66 exhibits reduced crystallinity (29.57%), a high Li + transference number (0.55), and an ionic conductivity of 4.65 × 10 −4  S cm −1 at 60 °C, together with an electrochemical stability window of 5.3 V. Li||Li symmetric cells cycle stably for over 3200 h, while LFP||Li cells deliver 142 mAh g −1 with 92.2% capacity retention after 300 cycles. Mechanistic analysis indicates that the synergistic effects of the porous framework and -NH 3 + functional groups promote LiTFSI dissociation, regulate Li + deposition, and enable the formation of a stable solid electrolyte interphase, thereby suppressing dendrite growth. This work provides insight into protonation-engineered MOFs fillers for designing SPEs toward safe and high-performance solid-state lithium metal batteries.