Hollow-structured materials for lithium–sulfur batteries: Design principles, mechanistic insights, and practical limitations

Lithium–sulfur batteries (LSBs) are regarded as promising next-generation energy storage systems owing to their exceptionally high theoretical energy density, sulfur's high theoretical specific capacity, and the natural abundance of sulfur. However, their practical deployment remains hindered by intrinsic challenges, including severe polysulfide shuttling, sluggish redox kinetics, poor electronic conductivity, and large volumetric changes. Hollow-structured materials have emerged as versatile sulfur hosts and functional components capable of simultaneously addressing several of these issues through integrated physical confinement, chemical adsorption, and electrocatalytic conversion. This review examines recent progress in the design and application of hollow-structured materials for LSBs, including carbon-based architectures, polar metal oxides and sulfides, and composite or yolk–shell heterostructures. Rather than cataloging materials, we focus on the underlying design principles that govern performance, emphasizing the interplay between cavity geometry, shell composition, hierarchical porosity, and interfacial chemistry. Key mechanistic roles—polysulfide confinement, adsorption strength regulation, and catalytic conversion kinetics—are systematically discussed alongside their inherent trade-offs. Finally, we highlight unresolved challenges that limit practical implementation, such as excessive adsorption-induced polarization, electrolyte consumption under lean conditions, structural degradation, and scalability of synthesis. By distilling structure–function relationships and identifying critical performance bottlenecks, this review aims to provide design guidelines for the rational development of high-performance LSBs.