Ion shielding functional separator using halloysite containing a negative functional moiety for stability improvement of Li–S batteries

Abstract Lithium–sulfur batteries are one of the attractive next-generation energy storage systems owing to their environmental friendliness, low cost, and high specific energy densities. However, the low electrical conductivity of sulfur, shuttling of soluble intermediate polysulfides between electrodes, and low capacity retention have hampered their commercial use. To address these issues, we use a halloysite-modulated (H-M) separator in a lithium–sulfur battery to mitigate the shuttling problem. The H-M separator acts as a mutual Coulombic repulsion in lithium-sulfur batteries, thereby selectively permitting Li ions and efficiently suppressing the transfer of undesired lithium polysulfides to the Li anode side. Moreover, the use of halloysite switches the surface of the separator from hydrophobic to hydrophilic, consequently improving the electrolyte wettability and adhesion between the separator and cathode. When sulfur-multi-walled carbon nanotube (S-MWCNT) composites are used as cathode active materials, a lithium–sulfur battery with an H-M separator exhibits first discharge and charge capacities of 1587 and 1527 mAh g−1, respectively. Moreover, there is a consistent capacity retention up to 100 cycles. Accordingly, our approach demonstrates an economical and easily accessible strategy for commercialization of lithium–sulfur batteries.