Polysulfide chemistry in metal–sulfur batteries

Renowned for their high theoretical energy density and cost-effectiveness, metal–sulfur (M–S) batteries are pivotal in overcoming the current energy storage bottlenecks and accelerating the transition toward a cleaner society. Polysulfides (PSs) serve as essential intermediates in M–S batteries and bridge the electrochemical redox processes of sulfur, playing a decisive role in controlling the electrode behaviors and regulating the battery performances. Understanding PS chemistry across diverse battery environments is key to advancing M–S batteries. This review aims to provide a comprehensive overview of the PS chemistry in high-energy-density battery systems and outline future research directions. The compositions, properties, and characterization methods of PSs are introduced to facilitate a fundamental understanding of the PS chemistry in working batteries. Following this, a thorough examination of the chemical and electrochemical behaviors of PSs and their impacts on electrode performances is conducted to deepen the insights into the PS reactions in batteries. Building on this foundation, representative PS regulation strategies are discussed, focusing on molecular modification, solvation optimization, and interfacial regulation, to achieve superior M–S battery performances. Challenges of PSs in practical M–S batteries are finally analyzed, and perspectives on the future research trends of PS chemistry are presented.