MFI Zeolite Nanosheet Composite Membranes with Both High Lithium Ion Transport and Sulfur Fixation for Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are considered the most promising next-generation power batteries. However, their wide application is restricted by the poor cycling stability resulting from the lithium polysulfide (LiPS) shuttle. Herein, composite membranes based on two-dimensional (2D) MFI-type molecular sieve nanosheets are first designed and synthesized to solve the problem. The MFI-type molecular sieves with a specific pore channel (∼0.56 nm) can effectively suppress the LiPS shuttling via size screening. Meanwhile, the molecular sieves with a 2D structure and porous properties can significantly increase electrolyte wettability to guarantee high Li⁺ conductivity. In addition, comparing the composite membranes of pure silicon molecular sieve and silicon aluminum molecular sieve (ZSM-5), it can be found that ZSM-5 composite membranes with strong adsorption and high electronegativity can further suppress polysulfide shuttle. As a result, Li-S batteries with ZSM-5 nanosheet composite membranes achieve a high capacity of up to 763 mAh g^-1 at 2 C and the retention rate is 46.4% after 400 cycles. This work demonstrates the potential of 2D material permselective membranes in improving the overall Li-S battery performance.