Spartina anglica-Derived Carbon-Coated PE Separator for Physically Restraining Polysulfide Migration in Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) have received substantial interest because their theoretical energy density is considerably higher than that of conventional lithium-ion batteries. However, the difficulty in confining the soluble intermediate polysulfide (PS) species of LSBs hinders the prolonged cycling of the cell. In this study, a Spartina anglica-derived carbon-coated polyethylene (PE) separator (SC-coated PE separator), which can confine the PS species on the cathode side, is developed to improve the cycling retention of LSBs. Spartina anglica, which is considered a predominant marine waste, is converted to task-specific carbon materials via size-controlled milling and carbonization, and is embedded on a PE separator through a simple casting process. The SC-coated PE separator improves the electrolyte affinity, which is characterized by measuring the contact angle, electrolyte uptake, and transference number of Li+; consequently, the migration of Li+ is undisturbed in the cell, even if an additional layer is formed on the PE separator. Based on the electrochemical performance, the SC-coated PE separator exhibits a higher initial specific capacity than the PE separator, in addition to a remarkably increased cycling retention (65.3% vs. 27.7%) after 100 cycles. The SC-coated PE separator effectively inhibits the PS species through physical absorption, thereby increasing the utilization of the active sulfur species. Moreover, the SC-coated PE separator presents a relatively stable interfacial morphology of the cycled Li anode, revealing that the comprehensive interfacial stability of the Li-S cell is enhanced by effectively confining the PS species in the cell. [GRAPHICS] .