锂硫电池中多硫化锂结构与性质研究进展

To address the urgent demand for high-specific-energy storage technologies in electric vehicles, drones, aerospace, and related fields, lithium-sulfur (Li-S) batteries have emerged as a pivotal technology to surpass the energy density limits of conventional lithium-ion batteries, boasting a theoretical energy density of 2600 Wh kg^{- 1}. Lithium polysulfides (LiPSs), as key intermediates in Li-S batteries, critically determine the practical performance across multiple dimensions. To meet the critical requirements of high energy density, fast charge/discharge capability, long cycling life, and enhanced safety, a fundamental re-examination of the structure and properties of lithium polysulfides is imperative for their rational design and regulation. Based on the recent advances in the Li-S battery research field, this review systematically examines the structures and properties of lithium polysulfides from three key perspectives: existing forms, solvation structures, and solid-liquid reaction mechanisms. First, in terms of the existing forms, we introduce the recognition of lithium polysulfide predominantly existing as cationic species in the electrolyte, elucidating their detrimental effects on sluggish cathode kinetics and exacerbated anode side reactions. Additionally, LiPS aggregation behaviors under lean-electrolyte and low-temperature conditions are discussed. Accordingly, advanced regulation strategies targeting polysulfide cations and aggregation are reviewed, including anion coordination, covalent modification, and electrostatic balance. Second, regarding the solvation structures, we review the evolution of electrolyte design from strongly solvating to moderately solvating and weakly solvating electrolytes, analyzing their distinct polysulfide solvation structures and resultant battery performance. The encapsulated dual-layer solvation structure design is emphasized for its potential to balance cathodic reaction kinetics and anode stability. Furthermore, the influence of increased weakly-solvating-solvent proportions in such systems on electrode behavior is discussed, along with proposals to overcome the cathodic kinetic limitations via electrocatalysis or redox mediation strategies. Third, in terms of liquid-solid reactions, we introduce the novel concept of ternary phase diagrams for Li-S systems, detailing their construction methodology, analytical interpretation, and potential applications. We further elucidate how these phase diagrams revise traditional discharge capacity allocation and identify insufficient Li₂S deposition as the core issue limiting capacity retention. Moreover, we demonstrate the utility of ternary phase diagrams in deciphering Li-S reaction thermodynamics across diverse electrolyte systems. Finally, we prospectively explore the dynamic evolution mechanisms of LiPSs under practical battery operating conditions, including lean electrolyte, extreme temperature, and high-rate scenarios, based on emerging theories of lithium bond chemistry and cross-scale modeling. We further underscore the need for multidimensional synergistic strategies to optimize polysulfide solvation structures guided by artificial intelligence-driven electrolyte design, ultimately bridging molecular insights and device performance. This review aims to provide theoretical foundations for the rational development of high-energy-density Li-S batteries and inspire cross-scale thermodynamic-kinetic analyses for multi-phase and multi-intermediate electrochemical systems.