From Low- to High-Entropy PBAs and Their Derivatives for Lithium-Sulfur Batteries.

The accelerating global demand for energy has catalyzed the pursuit of advanced, sustainable energy storage systems. Among them, lithium-sulfur (Li-S) batteries stand out for their high theoretical energy density and the abundance and low cost of sulfur. However, their practical deployment remains restricted by issues such as polysulfide dissolution, sluggish redox kinetics, and the notorious shuttle effect. Recent efforts have focused on engineering sulfur host materials and electrocatalysts to overcome these limitations, particularly through the use of polar inorganic compounds that interact strongly with lithium polysulfides (LiPSs) to improve conversion efficiency and cycle stability. In this context, new materials with configurational entropy ranging from low to high entropy have emerged as a new class of functional materials, offering unprecedented structural and compositional tunability. Among them, Prussian blue analogues (PBAs) have gained increasing attention due to their open frameworks, controllable composition, and redox-active sites. Moreover, PBAs represent highly versatile precursors for the rational design and synthesis of advanced catalytic materials, encompassing alloys, metal oxides, metal sulfides, and metal phosphides, among other functional compounds. This review provides a comprehensive and critical assessment of the progress in the application of low-, medium-, and high-entropy PBAs and their derivatives as solid catalysts in Li-S batteries. We clarify the definitions of configurational entropy in PBAs and highlight the current misuse of the term in the literature. The review also addresses synthetic strategies for multielement PBAs, evaluates their physicochemical and catalytic properties, and correlates these features with electrochemical performance. Finally, we identify emerging design trends, key challenges, and future perspectives for the rational development of entropy-tailored PBAs in next-generation Li-S batteries.