Sulfonic Acid Groups Functionalized Titanium‐Based Metal–Organic Framework Composite Separators for Lithium–Sulfur Battery Applications

Abstract Addressing the intrinsic issues of lithium–sulfur (Li–S) batteries, including the polysulphide shuttling effect and lithium dendrite growth, is essential. A functionalized membrane is designed by incorporating a titanium‐based metal–organic framework MOF functionalized with sulfonic acid groups into a polypropylene (PP) separator. This composite separator combines the significant specific surface area and the large microporosity of MOF and serves as a physical barrier for the PP separator. Meanwhile, introducing sulfonic acid groups into MOF effectively inhibits the polysulfides' shuttle effect. Moreover, it can expedite the swift transport of lithium ions, thereby inhibiting the development of lithium dendrites. The batteries assembled with sulfonation‐modified MOF composite separators have better electrochemical performance due to improved electrolyte wettability and reduced electrical resistance and retains over 50% capacity retention at 0.2 C (1 C = 1675 mAh g −1 ) at the end of 200 cycles. This methodology establishes a scalable pathway for engineering high‐performance lithium–sulfur batteries.