Lithium-sulfur batteries are a type of rechargeable battery technology that has gained attention due to their high energy density and potential for lower cost compared to traditional lithium-ion batteries. However, Li-S batteries suffer from capacity fade over multiple charge-discharge cycles. This is due to the dissolution and diffusion of intermediate lithium polysulfide species, which can lead to loss of active material and reduced capacity over time. The characterization of those species and inhibition of their formation can result in improved Li-S batteries. Interference-free mass spectrometric (MS) detection of sulfur atoms may be conducted in high-resolution ICP-MS devices such as sector-field mass spectrometers. In this work, a method using liquid chromatography (LC) sector-field ICP-MS for detection and quantification of the polysulfide species was proposed.
The procedure allowed separation and quantification of polysulfide distributions Li2Sx with x ranging from 1 to 8 generated in organic solvents. As anticipated, the mixtures with high S content show higher percentage of long-chain polysulfides and also a high content of Li2S. The optimized technique was also applied to the investigation of electrolytes after cycling Li-S batteries and the polysulfide distribution change at constant voltage values was recorder. It was shown that main polysulfides species in 50%- and 100%-discharged batteries is disulfide anion, whereas the most abundant species in completely charged batteries are tri- and tetrasulfide.