Lithium-sulfur (Li-S) batteries, characterized by an ultrahigh theoretical energy density of 2600 W·h·kg^-1, have emerged as promising candidates to replace conventional lithium-ion batteries. The abundance and low-cost accessibility of sulfur resources further reinforce their potential for scalable applications. Within the critical components of Li-S batteries, electrolyte research has drawn substantial attention, particularly polymer electrolytes due to their merits of low-cost fabrication, lightweight nature, and tunable structural design. While the introduction of solid polymer electrolytes (SPE) and gel polymer electrolytes (GPE) markedly enhances battery safety by mitigating flammable liquid leakage, persistent dissolution of lithium polysulfides (Li₂S_x, 4≤x≤8) during cycling remains unresolved. This dissolution phenomenon inevitably triggers the "shuttle effect", where soluble polysulfides migrate between electrodes, leading to irreversible active material loss and rapid capacity decay. Such challenges position the "shuttle effect" as a pivotal barrier impeding the commercialization of Li-S batteries. Therefore, in-depth exploration of the generation mechanism of the "shuttle effect" is of crucial significance for effectively suppressing this effect through the design and optimization of polymer electrolytes.

The working principle of lithium-sulfur batteries is based on the redox reaction between sulfur and lithium, involving a complex "solid-liquid-solid" transformation process. During charging and discharging, the generation and diffusion of soluble lithium polysulfides lead to the "shuttle effect", which in turn causes self-discharge and capacity decay. Traditional liquid electrolytes are prone to leakage and cannot effectively suppress the shuttle of polysulfides. Therefore, researchers have turned to solid or quasi-solid electrolytes, especially polymer electrolytes. However, the molecular structure of polyethylene oxide (PEO) is similar to that of traditional polyether-based liquid electrolytes, and its ethylene oxide (EO) units have a high Gutmann donor number (DN), showing significant solvation ability. This characteristic enables polysulfides to dissolve in the PEO matrix through complexation, thereby triggering the "shuttle effect" and exacerbating capacity decay. In other polymer electrolytes, the solubility of polysulfides in the polymer electrolyte limits their complete suppression of the "shuttle effect".

To effectively suppress the "shuttle effect", researchers have proposed various strategies, including the preparation of composite polymer electrolytes by combining polymer matrices with inorganic fillers, ionic liquids, or other functional materials to synergistically enhance the performance of the electrolyte, such as physical adsorption, chemical adsorption, physical-chemical synergy, and catalytic conversion. Physical adsorption mainly restricts the diffusion of polysulfides by constructing physical barriers or utilizing electrostatic interactions. For example, introducing nano-ceramic particles or constructing micro-porous structures in the electrolyte can effectively block the migration of polysulfides. Chemical adsorption fixes polysulfides by introducing functional groups or utilizing Lewis acid-base interactions in the polymer electrolyte. For instance, polymer electrolytes containing ester groups, amino groups, etc., can form chemical bonds with polysulfides, thereby inhibiting their diffusion. Physical-chemical synergy combines the advantages of physical confinement and chemical adsorption. For example, metal-organic frameworks (MOFs) materials achieve dual restrictions on polysulfides through their micro-porous structures and surface functional groups. The catalytic conversion strategy introduces catalysts to rapidly convert polysulfides into insoluble Li₂S, fundamentally suppressing the "shuttle effect".