Fluorine functionalized MIL-101 endows polymer electrolyte with highly Li+ dissociation, Li+ transference number and stabilized SEI for high-rate lithium metal batteries

Fluorinated MOFs material F-MIL-101 simply synthesized by hydrothermal method. • A gel polymer electrolyte that can fully dissociate LiTFSI. • The t Li + $t_{{\mathit{Li}}^{+}}$ of FM-10 is 119% higher than M-10. • The FM-10 formed a LiF-rich SEI layer on the lithium anode. • LFP||Li cells achieve excellent rate and cycling characteristics. Development of an attractive inorganic filler plays a vital role in effectively enhancing the comprehensive performance of a polymer electrolyte. Herein, a fluorine-functionalized metal organic framework (fluorinated MIL-101, F-MIL-101) is intentionally designed as filler for fabricating a novel composite polymer electrolyte (FM-10). Spectroscopic analysis and density functional theory calculations reveal that F-MIL-101 exhibits high effective dissociation and transportation of Li + for LiTFSI salt. Notably, the F functional group hinders anion transport, thereby giving the FM-10 GPEs a high transfer number of 0.81 for a uniform deposition of Li + on the Li anode surface. Furthermore, the F group of F-MIL-101 is greatly favorable for the formation of a stable LiF-rich solid electrolyte interface (SEI) on the Li anode surface during cycling to hinder the uninterrupted reaction. Consequently, the FM-10 GPEs demonstrates an excellent stable Li anode with a long cycle-life of 600 h in Li||Li cell at 2 mA cm −2 . More importantly, the FM-10 GPEs assembled LiFePO 4 (LFP) || Li cell exhibited an initial discharge capacity of 120.5 mAh g −1 at a high 6C-rate and a retention of 98.68% after 300 cycles, implying that the F-MIL-101 filler shows great potential as a strategy for fast charging, long cycle life, and high safety SSLMBs.