Beaver-dam-like membrane: A robust and sulphifilic MgBO₂(OH)/CNT/PP nest separator in Li-S batteries

The assembly of various low dimensional nanomaterials into hierarchical nanostructures is a central issue since it inherits the advantages of each component and even leads to the formation of advanced materials with unforeseen properties. The rational integration of nanomaterials into an effective membrane is expected to regulate the complex energy chemistry of lithium–sulfur (Li–S) batteries. In this contribution, a bio-inspired beaver-dam-like membrane was proposed as a robust and sulphifilic nest separator for advanced Li–S cells. The nest separator was integrated by a continuous polypropylene, a highly electrical conducting network of carbon nanotubes (CNTs), and lithium polysulfide (LiPS)-suppressing adsorbents of magnesium borate hydroxide (MBOH) nanofibers to enhance the redox reaction of LiPS intermediates and retard their migration in a working cell. The kinetic behavior of LiPS conversion on sulphifilic surface was well understood through direct measurements of lithium sulfide nucleation and potentiostatic discharge profiles, demonstrating the interfacial affinity between MBOH and LiPS. The smart hybridization of MBOH and CNTs in nest separators rendered the Li–S cell with long cycling stability of 785 mA h g⁻¹ after 200 cycles, high rate capability of 500 mA h g⁻¹ at 6 C, enhanced areal capacity of 2.91 mA h cm⁻², and improved thermal stability. The presented bio-inspired design sheds fresh light on a novel electrolyte system to demonstrate the superb electrochemical performances of Li–S batteries and affords new insights into understanding the interfacial interaction between LiPS and adsorbents.