Chapter 5 - Reliable HPLC-MS method for the quantitative and qualitative analyses of dissolved polysulfide ions during the operation of Li-S batteries

Abstract

The polysulfide ions generated during the operation of Li-S batteries are generally soluble in a nonaqueous electrolyte. The dissolved polysulfide ions play a critical role in the redox reaction of Li-S batteries. For example, the dissolved polysulfide ions are responsible for the “shuttle effect,” which is the root cause of the low efficiency and high self-discharge of Li-S batteries. Due to the lack of the standard solution of individual polysulfide ions, high-performance liquid chromatography-mass spectrometry (HPLC-MS) is the only reliable analytical method for the identification of the dissolved polysulfide ions in the electrolyte. In this chapter, the advantages of HPLC-MS versus other spectroscopic techniques are discussed. The HPLC-MS essays for the polysulfide separation and determination are introduced. By means of the HPLC-MS technique, the distribution of polysulfide ions in electrolytes can be quantitatively and qualitatively determined. Coupled with an electrochemical technique, the redox mechanisms of sulfur cathode are revealed through the determination of the distribution of polysulfide ions at various stages of charge and discharge in a Li-S battery.