Mapping Polysulfides in Sodium–Sulfur Batteries
Year: 2025
Type: article
Abstract: High Resolution Image Download MS PowerPoint Slide Sodium–sulfur (Na–S) batteries provide lithium-free alternatives to lithium–sulfur (Li–S) batteries. Na–S chemistry has been less studied. Thus, the types of polysulfides (PS) and their evolution during charge–discharge of Na–S batteries are not as well understood as those in the Li–S system. We, therefore, study the formation of different PS in tetraethylene glycol dimethyl ether-based electrolyte during battery operation using in situ Raman and ex situ ultraviolet–visible (UV–vis) spectroscopies. We start by making reference solutions with different ratios of sodium sulfide (Na 2 S) to sulfur, ranging from pure Na 2 S to Na 2 S:7S, with the sulfur ratio increasing by one integer per solution. We then correlate the UV–vis and Raman peaks to PS species. Our galvanostatic charge–discharge (GCD) and cyclic voltammetry measurements show a total of ten features. Using ex situ UV–vis on aliquots and in situ Raman spectra from PS solutions at GCD voltage plateaus, we map out sodium polysulfide (NaPS) species at key stages of the charge–discharge cycle. We identify Na 2 S 8, Na 2 S 4, and Na 2 S 2 as intermediates and Na 2 S as the final product. We find that intermediate Na 2 S 6 forms from disproportionation of Na 2 S 8 and Na 2 S 4 . We also observe that intermediate PS can also dissociate into S 3 •– radical species, which contributes to loss of active material. Our results provide detailed insights into Na–S chemistry that will be helpful for the development of high performance and stable batteries.
Source: ACS Nano
Institution: University of Cambridge
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,500
OpenAlex ID: W4408077473