Structural engineering of MXene frameworks with abundant surface functionalities for enhanced lithium–sulfur battery electrochemistry

Abstract

Two-dimensional MXene materials have garnered significant attention in lithium–sulfur battery (LSBs) research due to their inherent high electrical conductivity and exceptional catalytic activity, which help mitigate the intrinsic challenges of sluggish redox kinetics and polysulfide shuttling. However, systematic investigations into the correlation between the structural evolution of MXene-based electrodes and their electrochemical performance remain underdeveloped. In this study, Ti₃C₂T_x and Ti₂CT_x are fabricated via a top-down method, and their performance differences in LSBs are compared. Due to its unique three-layer titanium atomic structure and rich surface functional groups (–OH, –O, –F, etc.), Ti₃C₂T_x exhibits excellent conductivity and chemical stability. Electrochemical testing and in situ ultraviolet–visible spectroscopy analysis show that Ti₃C₂T_x effectively suppresses the polysulfide shuttle effect and accelerates the redox conversion of sulfur species. The cell using Ti₃C₂T_x as a separator exhibits a capacity decay rate of 0.085% at 2 C after 200 cycles, and it maintains stable cycling at 60 °C, in contrast to Ti₂CT_x, which fails after 50 cycles. This study highlights how structural differences in MXene materials influence the electrochemical behavior of LSBs, providing new insights and establishing a foundation for their application in high-performance LSBs.