Two Birds with One Stone: Interfacial Engineering of Multifunctional Janus Separator for Lithium-Sulfur Batteries

Li dendrite growth and unsatisfactory sulfur cathode performance are two core problems that greatly restrict the practical applications of lithium-sulfur batteries (LSBs). Here, an all-in-one design concept for Janus separator enabled by the interfacial engineering strategy is proposed to improve the performance of LSBs. At the interface of anode/separator, the thin functionalized composite layer contains the high-elastic-modulus and high-thermal-conductivity boron nitride nanosheets and oxygen group-grafted cellulose nanofibers (BNNs@CNFs), which can effectively avoid the formation of "hot spot", homogenize Li-ion flux, and suppress dendrite growth. Meanwhile, at the interface between separator and cathode, the high-density homogenously exposed Ru single atoms on the surface of reduced graphene oxide (rGO@Ru SAs) can "trap" the polysulfides and considerably reduce the activation energy to boost their conversion kinetics. Consequently, the LSBs show a high capacity of 460 mAh g-1 at 5 C and ultrastable cycling performance with an ultralow capacity decay rate of 0.046% per cycle over 800 cycles. To further demonstrate the practical prospect of our Janus separator, an assembled Li-S pouch cell using our Janus separator delivers a cell-level energy density of 310.2 Wh kg-1 . This study provides a promising strategy to simultaneously tackle the challenges facing metallic Li anode and sulfur cathode in LSBs. This article is protected by copyright. All rights reserved.