Comprehensive Lithium Polysulfide Diffusion Insights within Solid-State Electrolytes

Lithium-sulfur (Li-S) batteries are highly attractive for next-generation energy storage applications due to their low cost, high theoretical energy density, and environmental benefits (nontoxicity, reducing reliance on rare metals, etc.). However, the implementation of Li-S batteries in the current battery manufacturing lines is hindered by the polysulfide dissolution and migration from cathode to anode through the liquid electrolyte, leading to irreversible capacity fading, poor Coulombic efficiency, and therefore limited battery lifetime. Replacing liquid electrolytes with solid-state electrolytes is the most promising approach to overcome the polysulfide migration challenge in lithium-sulfur (Li-S) batteries. Nevertheless, a fundamental understanding of the mechanisms governing polysulfide diffusion and the development of effective mitigation strategies are crucial. This perspective aims to provide a detailed overview of polysulfide diffusion mechanisms in solid-state electrolytes based on inorganic, polymer, and hybrid materials for Li-S battery applications. Examples of the challenges associated with polysulfide migration and the mitigation strategies employed in each solid electrolyte are provided. These strategies are focused on protective coatings, chemical modifications, advanced sintering techniques, material design, and computational modeling. Moreover, the relevance of advanced characterization techniques (such as XAS and XPS) to elucidate the complex polysulfide dissolution mechanisms occurring in solid electrolytes is highlighted. The insights presented here provide a critical foundation for future research development of efficient and high-performance solid-state Li-S battery devices.