Crown ether functionalized large-area graphene oxide and MXene hybridize as ion-sieving layers for high-performance lithium–sulfur batteries

Abstract

Two crucial challenges hindering the widespread application of lithium–sulfur (Li–S) batteries are the sluggish conversion of sulfur and the shuttle of lithium polysulfides (LPSs). Designing an ion-selective membrane that allows fast Li-ion transport yet restricts the migration of LPSs via the construction of well-defined structures in a scalable and cost-effective manner is a promising strategy for advancing high-energy-density lithium–sulfur batteries. Herein, a diamino crown ether (CE) molecule is grafted to the surface of large-area graphene oxide (GO) to modify the separator in Li–S batteries using a straightforward coating method without a polymer binder. The decorated GO-CE ion-sieving layer possesses high ion conductive properties and abundant supramolecular channels created by CE functional groups, which can simultaneously chemically/physically inhibit shuttling of LPSs and catalytically accelerate the diffusion/conversion of LPSs through the CE-Li⁺ interaction. The GO-CE modified separator, featuring an ultra-thin (∼100 nm) and ultra-light (∼0.06 mg cm⁻²) ion-sieving layer, enables the cell to have excellent rate performance and good cyclic stability with a low capacity decay of 0.035% per cycle over 1500 cycles at 1C. The GO-CE is prepared to hybridize with MXene nanosheets to create a cell with an electrically and thermally conductive ion-sieving layer, exhibiting not only ultra-low capacity decay of 0.025% but also excellent resistance to thermal gradients and an intelligent self-closing mechanism at elevated temperatures. This study introduces a novel strategy for enhancing the performance of Li–S batteries using ion-sieving membranes.