Examining the Chemical Stability of Battery Components with Polysulfide Species by High-Performance Liquid Chromatography and X-ray Photoelectron Spectroscopy

The polysulfides formed in a lithium-sulfur (Li-S) battery during charge/discharge are highly reactive and soluble in a nonaqueous electrolyte. Consequently, to utilize the high energy density of a Li-S battery, it is required that the battery components must be chemically stable against polysulfides. In this work, based on the established high-performance liquid chromatography method for polysulfide analysis, the chemical stabilities of eight kinds of battery components against polysulfides were investigated, including five current collectors, one separator, and two binders. To correlate the chromatographic observations, spectroscopic analyses, X-ray photoelectron spectroscopy and scanning electron microscopy/energy-dispersive spectroscopy, were also performed. It was found that three current collectors (Al, stainless-steel 304, and Ti), a Celgard polypropylene separator (Celgard 2400), and two binders (carboxymethyl cellulose and polyvinylidene fluoride) were stable with polysulfides up to 180 days at room temperature. Both Cu and Ni current collectors were not stable with polysulfides, although the Cu current collector was more reactive with polysulfide than the Ni current collector.