Interface engineering of MXene-based heterostructures for lithium-sulfur batteries

High energy density and low cost make lithium-sulfur (Li-S) batteries as one of the next generation's promising energy storage systems. However, the following problems need to be solved before commercialization: (i) the shuttling effect and sluggish redox kinetics of lithium polysulfides in sulfur cathode; (ii) the formation of lithium dendrites and the crack of solid electrolyte interphase; (iii) the large volume changes during charge and discharge processes. MXenes, as newly emerging two-dimensional transition metal carbides/nitrides/carbonitrides, have attracted widespread attention due to their abundant active surface terminals, adjustable vacancies, and high electrical conductivity. Designing MXene-based heterogeneous structures is expected to solve the stacking problem induced by hydrogen bonds or Van der Waals force and to provide other charming physiochemical properties. Herein, we generalize the design principles of MXene-based heterostructures and their functions, i.e., adsorption and catalysis in advanced conversion-based Li-S batteries. Firstly, the physiochemical properties of MXene and MXene-based heterostructures are briefly introduced. Secondly, the catalytic functions of MXene-based heterostructures with the compositional constituents including carbon materials, metal compounds, organic frameworks, polymers, single atoms and special high-entropy MXenes are comprehensively summarized in sulfur cathodes and lithium anodes. Finally, the challenges of MXene-based heterostructure in current Li-S batteries are pointed out and we also provide some enlightenments for future developments in high-energy-density Li-S batteries.