and the undesired soluble LiPSs migrate through the porous commercial separators to the metallic Li anode, causing corrosion and passivation. [8] In terms of the metallic Li anode, the Li-dendrite growth triggered by the nonuniform Li dissolution/deposition will induce an internal short circuit. [9] To counteract these negative consequences, researchers have developed hosts for sulfur encapsulation in cathode, [10][11][12][13] lithium anode protection, [14] and separator modification to prevent lithium polysulfides (LiPSs) from shuttling. [15][16][17] Proposing a rational design strategy for simultaneous enhancement of both metallic Li anode and sulfur cathode is of great significance. The separator, one of the most indispensable components, contacts both the cathode and anode directly. It is considered to be a facile and effective approach to functionalizing separators to confine LiPSs and synchronously regulate the Li dissolution/deposition in LSBs. [18][19][20] The commercial polyolefin separator with a low melting point and nonpolar characteristics results in poor electrolyte affinity and difficulty in modification. [21,22] In addition, most of the functionalization strategies have not paid attention to the thickness and weight, which would apparently reduce the energy density of LSBs.What's worse, the stripping of the coated layer from the separator extensively exists in traditional separator modification methods, which would significantly diminish practical performance and even raise serious safety concerns about Li-metal batteries. [23,24] Especially for high energy-density batteries used in electric vehicles (Tesla, 4680), a large amount of binder (polyvinylidene fluoride; PVDF) would be coated on the separator to improve cycle stability, preventing the powder from falling off during cycling, but this is still ineffective. [25,26] Magnetron sputtering, an effective approach for fiber functionalization, could be a solution to the aforementioned issues. [27] During the sputtering process, the functional target material would deposit on the substrate in the form of atoms or molecules, enhancing the adhesion to overcome stripping defects.Meanwhile, research has demonstrated that electrospun nanofibrous separators with high porosity and polar groups were easily modified to improve the electrolyte affinity and suppress the shuttle effect of LiPSs. [28,29] Polyacrylonitrile (PAN) Exploring a scalable strategy to fabricate a multifunctional separator is of great significance to overcome the challenges of lithium polysulfides (LiPSs) and dendritic growth in lithium-sulfur batteries (LSBs). Herein, a binder-free Janus separator is constructed by interfacial engineering. At the cathode interface, an ultra-thin covalent triazine piperazine film containing tailorable micropores and adsorption sites is decorated on polyacrylonitrile (PAN) membrane by in situ interfacial polymerization, building a triple barrier for LiPSs. The combination of steric hindrance and chemical adsorption reduces LiPS's migration by 81.85%. Me...