Balancing the Seesaw: Investigation of a Separator to Grasp Polysulfides with Diatomic Chemisorption.

Lithium-sulfur (Li-S) batteries are promising next-generation high-density energy storage systems due to their advantages of high theoretical specific capacity, environmental compatibility, and low cost. However, high-order polysulfides dissolve in the electrolyte and subsequently lead to the undesired polysulfide shuttle effect, which hinders the commercialization of Li-S batteries. To tackle this issue, morpholine molecules were successfully grafted onto a commercial polypropylene separator. Density functional theory (DFT) calculations were performed and revealed that morpholine side chains could equally and reversibly grasp all the high-order polysulfides. This diatomic chemisorption adjusted the transformation process among the sulfur-related compounds. The modified separator battery possessed a discharge capacity as high as 827.8 mAh·g-1 after 500 cycles at 0.5 C. The low capacity fading rate, symmetrical cyclic voltammogram, and retention of the electrode morphology all suggest that the diatomic equal adsorption approach can successfully suppress the polysulfide shuttle effect while maintaining excellent battery performance.