Design of Functionalized Separators Based on Fluorinated Metal-Organic Framework and Their Application in Lithium Metal Batteries
The development of high-energy density lithium secondary batteries is key to meeting the increasing demand for advanced energy storage systems.Lithium metal batteries have attracted attention due to their high theoretical specific capacity,but issues such as uneven lithium ion flux and lithium dendrite formation have limited their further application.Herein,we report a new strategy of modifying polypropylene(PP)separator with fluorinated metal-organic framework(MOF)to overcome these challenges.By synthesizing fluorinated MOF and coating them on the surface of the PP separator,we successfully prepared a functionalized separator based on fluorinated MOF(MOF-4F@PP).The electronegative nanochannels and uniform porous structure in MOF-4F restrict the movement of anions and accelerate the transport of Li+.Experimental results show that compared to the unmodified PP separator,the MOF-4F@PP separator exhibits excellent electrolyte wettability,high ionic conductivity(0.96 mS cm-1),and Li+transference number(0.62).Therefore,the MOF-4F@PP separator can achieve a more uniform lithium ion flux,form a more stable interface layer,and effectively suppress the growth of lithium dendrites.Further studies indicate that the use of the MOF-4F@PP separator significantly improves the cycle life of Li//Cu and Li//Li batteries,achieving over 1 000 h of cycling.The MOF-4F@PP separator demonstrates excellent stability during lithium deposition/stripping processes,providing reliable protection for the long-term operation of lithium metal batteries.Additionally,Li//LiFePO4 batteries assembled with the MOF-4F@PP separator exhibit outstanding rate capability and cycling performance,with a discharge capacity of 125 mAh·g-1 after 200 cycles at 1 C rate.These results suggest that fluorinated metal-organic frameworks play a crucial role in regulating ion transport,offering new pathways and possibilities for enhancing the performance of lithium metal batteries.
fluorinated metal-organic frameworkspolypropylenefunctional separatorsdendriteslithium metal anodeslithium metal batteriesporous structuresion transports
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