High-Entropy Sulfides in Electrochemical Energy Storage: Evolution, Advanced Applications, and Future Prospects

High-entropy sulfides (HESs) integrate the high ionic conductivity of sulfide materials with the structural tunability of high-entropy design, demonstrating immense potential in advanced energy storage. This review systematically traces the development trajectories of HESs across four key domains: solid-state electrolytes, lithium-sulfur batteries, lithium/sodium-ion batteries, and supercapacitors. By critically examining the evolving "composition-structure-performance" relationships, we highlight breakthroughs in key metrics, including ionic conductivity, cycle life, rate capability, and specific capacitance. Crucially, insights reveal that crystal structure primarily determines the attainable performance window, whereas configurational entropy mainly improves structural stability and transport homogeneity. Therefore, the most effective design strategy avoids simply maximizing entropy. Instead, it combines favorable structural frameworks with moderate high-entropy engineering, often reinforced by nanoscale architectures. Ultimately, this work provides a clear historical framework and forward-looking guidance, emphasizing the need for rigorous validation in practical full cells to verify the intrinsic contributions of high-entropy effects.