Physical Inhibition and Chemical Confinement of Lithium Polysulfides by Designing a Double‐Layer Composite Separator for Lithium‐Sulfur Battery.

In this study, a novel double‐layer composite separator based on F‐doped poly‐m‐phenyleneisophthalamide (PMIA) and silicon dioxide (SiO2)−F co‐doped PMIA membrane is designed and prepared by electrospinning technology. The combination of F‐doped PMIA membrane and SiO2−F co‐doped PMIA membrane endows the functional separator with exceedingly high electrolyte uptake and retention, greatly prominent thermostability, and prevented shrinkage. Moreover, its strong physical inhibition and chemisorption can also confine polysulfides. Thus, the lithium‐sulfur (Li−S) batteries using the prepared membrane presented a high initial discharge capacity of 1274.8 mAh g−1 and maintained a reversible discharge capacity of 814.8 mAh g−1 with high Coulombic efficiency of 98.42 % after 600 cycles at 0.5 C. Meanwhile, the cell exhibited small interfacial resistance and excellent rate capacity. The excellent properties were attributed to high ionic conductivity offered by the large pore volume of unique 3D nanofiber network, excellent liquid electrolyte uptake of SiO2−F co‐doped PMIA membrane, and less "shuttle effect" suppressed by both the physical inhibition of polysulfides by the formed gel polymer electrolyte based on F‐doped PMIA membrane and chemical confinement of polysulfides by the addition of F and SiO2. The results indicated that the composite separator through the inexpensive, unsophisticated, and efficient preparation method can provide a good choice for high‐performance Li−S batteries. [ABSTRACT FROM AUTHOR]