Lithium-sulfur (Li-S) batteries promise high energy density but suffer from low conductivity, polysulfide shuttling, and sluggish conversion kinetics. The construction of heterointerfaces is an effective strategy for enhancing both polysulfide adsorption and conversion; however, the poor lattice compatibility in the heterointerface formed by different materials hinders interfacial charge transfer. In response to these challenges, herein, a biphasic homojunction of TiO₂ enriched with oxygen vacancies and decorated with nitrogen-doped carbon nanotubes (B-TiO_2−x@NCNT) was designed to simultaneously enhance adsorption ability and catalytic activity. This homojunction interface composed of rutile (1 1 0) and anatase (1 0 1) plane exhibits excellent compatibility, and density functional theory (DFT) calculations reveal that this biphasic interface possesses a much higher binding energy to polysulfides compared to single-phase TiO₂. Additionally, NCNTs are in situ grown on both interior and exterior surfaces of the hollow TiO₂ nanospheres, facilitating rapid electron transfer for the encapsulated sulfur. The homojunction interface synergistically leverages the oxygen vacancies and highly conductive NCNTs to enhance the bidirectional catalytic activity for polysulfide conversion. Therefore, in this multifunctional sulfur-host, polysulfides are first strongly adsorbed at the homojunction interfaces and subsequently undergo smooth conversion, nucleation, and decomposition, completing a rapid sulfur redox cycle. The assembled Li-S battery delivered a high specific capacity of 1234.3 mAh g⁻¹ at 0.2 C, long cycling stability for over 1000 cycles at 5 C with a low decay rate of 0.035%, and exciting areal capacity at a high sulfur loading of 5.6 mg cm⁻² for 200 cycles.

MXenes, a thriving class of two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides, demonstrate considerable potential in diverse electrochemical energy storage applications. To leverage MXenes for high-performance sulfur-based batteries, researchers have employed various strategies to modify their properties, aiming to tackle challenges such as the notorious shuttle effect induced by soluble polysulfides, sluggish redox reaction kinetics, and substantial volume expansion during the lithiation process. This review article offers an overview of MXene modification strategies, emphasizing their significant potential in adjusting the composition, surface chemistry, and morphology to address one or more challenges specially in sulfur cathodes. We first discuss internal regulation methods of MXene, including surface group engineering, heteroatom doping, and high-entropy MXene synthesis, which have been demonstrated to enhance MXene-polysulfide interactions and facilitate polysulfide conversion. Subsequently, we provide a summary of the recent design methods and advancements made in MXene-derived and MXene-based composites, with a particular emphasis on electronic structure reconstruction at the heterointerface and their synergistic roles in Li-S batteries. Following this, we outline the utilization of MXenes to address the challenges encountered in metal-sulfur batteries beyond Li-S batteries. Concluding the review, we offer prospects for the future development of utilizing MXenes in practical sulfur-based batteries.