Multifunctional Ion-Sieve Constructed by 2D Materials as an Interlayer for Li–S Batteries

For Li–S batteries, the interlayer between the separator and sulfur cathode preventing lithium polysulfide (LiPS) travel across the membrane is a research hotspot. The good blocking ability for LiPSs indicates that these interlayers can promote the electrochemistry performance with high S loading. However, most of these interlayers are just used as a simple blocking wall. Such a blocking wall, for example, the lower Li+ ion conductivity, would often reduce the electrochemical performance, especially under large current density. Here, we report a multifunctional ion-sieve made by three two-dimensional (2D) sheets, graphitic carbon nitride (g-C3N4), boron nitride (BN), and graphene. A g-C3N4 sheet which possesses orderly channels with a size of 3 A in the crystalline structure can effectively prevent polysulfides from passing through but allow lithium ions to pass freely, whereas a BN sheet acts as an excellent catalyst for sulfur redox, and graphene acts as an extended collector, which can promote the cond...