A trilayer carbon nanotube/Al2O3/polypropylene separator for lithium-sulfur batteries

A trilayer carbon nanotube (CNT)/Al₂O₃/polypropylene (PP) separator is prepared by means of simple tape casting of Al₂O₃ and CNT layers onto a commercial PP separator, respectively. The electrochemical performance of the trilayer separator in the lithium-sulfur batteries is compared with those of the PP and the Al₂O₃/PP separator. The CNT/Al₂O₃/PP separator exhibits the best electrochemical performance, including the cycling performance and rate capability. The CNT component in the trilayer separator acts as a matrix for capturing the polysulfide species and suppressing the migration of polysulfides to the lithium anode side and also reduces the charge transfer resistance of sulfur cathodes significantly. Meanwhile, the Al₂O₃ layer in the trilayer separator not only has the advantages on thermal stability and electrolyte intake but also can provide the strong shield for CNT from penetrating the separator.