What is the Importance of Metal–Sulfur Batteries?

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Battery analysis is a growing field in spectroscopy. Because scientists are focused on developing more sustainable forms of energy, batteries are looked at to power important tools, devices, and products while reducing the need to deplete natural resources, such as coal and petroleum. As a result, scientists have examined how to better improve the performance of batteries.

A recent study, published in the journal ACS Electrochemistry, explored how ultraviolet–visible (UV-vis) spectroscopy can be used to learn more about the redox reaction behavior in lithium–sulfur (Li–S) and sodium–sulfur (Na–S) batteries (1).

What are Metal–Sulfur Batteries?

Metal–sulfur batteries are rechargeable batteries known for having high specific energy (2). These energy storage technologies are considered to be the next-generation storage technologies because of their high theoretical energy density and relatively low material costs (1). Despite these advantages, widespread commercialization has been hindered by complex multistep redox reactions and the dissolution of intermediate polysulfides into ether-based electrolytes, which results in severe capacity fading and limited cycle life (1,2).

What did the researchers do in their study?

In their study, the researchers combined operando UV–visible (UV–vis) spectroscopy with rotating ring-disk electrode (RRDE) voltammetry to investigate sulfur redox behavior in Li–S and Na–S batteries using 1 M LiTFSI and 1 M NaPF₆ in DOL/DME (1:1) electrolytes. Although UV–vis spectroscopy has previously been used to monitor lithium polysulfide intermediates during cycling, this work expands the technique to sodium–sulfur systems and, for the first time, couples it with RRDE to provide direct detection and quantification of soluble intermediates (1). The integrated method enables calculation of the number of electrons involved in sulfur reduction processes in both battery types (1).

Ultimately, the researchers believe that their approach helps provide scientists with a better understanding of polysulfide formation and dissolution, offering new insights that can potentially guide improved electrolyte and electrode designs for more durable M–S batteries (1).

References

1. Bhardwaj, R. K.; Mandal, S. Insight into Metal–Sulfur (Li/Na) Redox Reactions through Operando UV–Vis and RRDE Studies. ACS Electrochem. 2025, ASAP. DOI: 10.1021/acselectrochem.5c00374
2. Zhang, S. S. Liquid Electrolyte Lithium/Sulfur Battery: Fundamental Chemistry, Problems, and Solutions. J. Pow. Sour. 2013, 231, 153–162. DOI: 10.1016/j.jpowsour.2012.12.102