Coordination chemistry in key components of Mg-S batteries: regulating polysulfide shuttle from cathode to electrolyte

Magnesium‑sulfur (Mg-S) batteries are emerging as highly promising candidates for next-generation high-safety, low-cost energy storage systems. This promise stems from their high theoretical energy density (1684 Wh kg −1 ), the abundance of sulfur, the generally dendrite-free plating behavior and high volumetric capacity of the magnesium anode. However, their practical development is hindered by several challenges, including sluggish Mg 2+ diffusion in solid-phase materials due to the high charge density of Mg 2+ , facile formation of passivation layers at the magnesium anode interface, and the polysulfide shuttle effect at the sulfur cathode during cycling. This review elucidates the electrochemical reaction mechanisms and the polysulfide shuttle effect in Mg-S battery systems, emphasizing the critical role of polysulfide conversion behavior and interfacial stability in determining battery performance. Based on the migration pathways and dissolution stages of polysulfides, this review systematically summarizes strategies including sulfur cathode structural optimization, advanced separator design, and the development of non-nucleophilic electrolytes, with particular focus on non-nucleophilic electrolytes highly compatible with magnesium anodes. Finally, future research directions for high-performance Mg-S batteries are discussed. This review aims to provide a systematic reference for the rational design and performance enhancement of Mg-S batteries, while also offering insights that may inform the development of other magnesium-based and sulfur-based batteries.