Transition Metal Chalcogenide Anodes for Sodium-Ion Batteries: Reaction Mechanisms, Structural Engineering, and Performance Optimization

As a promising alternative to lithium-ion batteries (LIBs), sodium-ion batteries (SIBs) have attracted considerable attention over the past decades due to their similar working principles to LIBs and the natural abundance of sodium resources. Extensive efforts have been devoted to understanding sodium-storage mechanisms and promoting the large-scale commercialization of SIBs. Among various anode candidates for SIBs, transition metal chalcogenides (TMCs) based on conversion and alloying reactions have been widely investigated owing to their higher theoretical capacities compared with conventional carbonaceous materials. However, their practical applications are still hindered by intrinsic limitations, including large volume variations, poor electrical conductivity, and shuttle effects, which severely deteriorate their cycling stability and rate capabilities. Inspired by the development of LIBs, various strategies have been proposed to address these crucial issues, such as nanostructure engineering, heterostructure design, and high-entropy configuration. In this review, recent progress in TMC anodes for SIBs is systematically classified and summarized based on these representative optimization strategies. Finally, the remaining challenges, potential solutions, and future perspectives for the rational design of advanced TMC anodes are highlighted.