A comprehensive investigation of solvation structure and cathode-electrolytes interface for sodium-sulfur batteries...

The solvation structure and cathode-electrolytes interface (CEI) formation in high-concentration carbonate-based electrolytes were systematically investigated to resolve compatibility and sluggish kinetics issues between polysulfides and electrolytes in carbonate-based sodium-sulfur batteries. By adopting a high surface area nitrogen-doped microporous carbon as a sulfur host and innovatively introducing high-concentration electrolytes into carbonate-based electrolytes, we successfully optimized the solvation structure, significantly suppressed irreversible reactions between polysulfides and electrolytes, improved sodium ion transport kinetics, and facilitated the formation of a stable CEI film. By employing Correlation spectroscopy, Raman, and infrared spectroscopy, as well as molecular dynamics simulations, we have revealed a significant impact of anions on the solvation structure of Na⁺ ions in high-concentration electrolytes. This finding can effectively reduce the irreversible reaction between solvent molecules and polysulfides. Furthermore, in-situ X-ray diffraction and argon ion sputtering X-ray photoelectron spectroscopy measurements corroborated the significantly enhanced sodium ion transport kinetics and the formation of a more stable CEI, respectively. Experimental results demonstrate that the battery exhibits an outstanding cycling performance with a capacity retention rate of 752.7 mAh/g after 200 cycles. These findings not only deepen our understanding of the relationship between salt concentration and battery performance but also provide valuable guidance for the development of high-performance and long-life sodium-sulfur batteries.