Dual-role magnesium aluminate ceramic film as an advanced separator and polysulfide trapper in a Li–S battery: experimental and DFT investigations

Abstract

Developing an advanced separator that can stop polysulfide shuttling remains a work-in-progress in the Li–S battery domain. Most of the work reported so far concentrates on functionalizing the commercial Celgard® separator such that it can trap polysulfides, preventing their shuttling to Li anode. In this study, we have developed a flexible MgAl₂O₄ (MAO) separator, which plays a dual role as separator and polysulfide adsorber. To effectively utilize the adsorbed polysulfide on MAO, multiwalled carbon nanotubes (MWCNTs) were coated on MAO, which slows down the capacity decay of the Li–S battery. As a result, the Li–S cell with MAO/MWCNT separator delivers a stable capacity of ∼500 mA h g⁻¹ for 250 cycles, higher than the capacity delivered by the Li–S cell with Celgard® separator. Furthermore, UV-Visible spectroscopy of the polysulfide solution exposed to MAO demonstrates polysulfide's binding ability with MAO. Furthermore, our density functional theory (DFT) calculations reveal the adsorption of polysulfides on the MAO.