Superior and safer lithium sulfur batteries realized by robust polysulfides-retarding dam with high flame retardance

Abstract

The unparalleled energy density has granted lithium-sulfur batteries (LSBs) with attractive usages. Unfortunately, LSBs still face some unsurpassed challenges in industrialization, with polysulfides shuttling, dendrite growth and thermal hazard as the major problems triggering the cycling instability and low safety. With the merit of convenience, the method of designing functional separator has been adapted. Concretely, the carbon aerogel confined with CoS₂ (CoS₂-NCA) is constructed and coated on Celgard separator surface, acquiring CoS₂-NCA modified separator (CoS₂-NCA@C), which holds the promoted electrolyte affinity and flame retardance. As revealed, CoS₂-NCA@C cell gives a high discharge capacity 1536.9 mAh/g at 1st cycle, much higher than that of Celgard cell (987.1 mAh/g). Moreover, the thermal runaway triggering time is dramatically prolonged by 777.4 min, corroborating the promoted thermal safety of cell. Noticeably, the higher coulombic efficiency stability and lower overpotential jointly confirm the efficacy of CoS₂-NCA@C in suppressing the lithium dendrite growth. Overall, this work can provide useful inspirations for designing functional separator, coping with the vexing issues of LSBs.