for each distinct electrolyte. The spectroscopy cell utilized mirrored the configuration of the operando Raman experiments, except that the optical window was substituted with Mylar ® polyester film to minimize absorption of X-ray through the window. The schematic depiction of this setup is presented in Figure . However, deciphering operando XAS spectra of sulfur during discharge poses a formidable challenge owing to the intricate blend of diverse polysulfides and the interference from LiTFSI, the electrolyte salt. To overcome this complexity, we employ a specialized technique known as multivariate curve resolution-alternating least squares (MCR-ALS) to unveil the "pure component(s)" within the unresolved mixture, as elaborated in detail in the SI. This method aids in recovering the most representative spectrum/spectra from the operando spectra, referred to as the "pure component(s)". It is essential to note that the term "pure component(s)" does not necessarily imply compositional purity; rather, it signifies that the associated spectrum/spectra may still represent a mixture of different compounds, such as polysulfides in this case. in Figure and compared with standard references. This ratio peaks at a DoD of 15%, surpassing the baseline (green lines in Figure ), suggests an accelerated conversion of longchain polysulfides. In contrast, the composition ratio of pure component #2 remains below 30% throughout the discharge process in the 0.11 M BNC-containing electrolyte (green lines in Figure ), indicative of extensive reactions between the elevated BNC concentration and middle-chain polysulfides. Additionally, the composition ratio of pure component #3 surpasses that of both the baseline and 0.11 M BNC-containing electrolytes, underscoring a complete SRR in this 16electron transfer reaction, attributed to enhanced kinetics.