Our findings from UV-vis and CV analyses reveal that BNC undergoes reactions with polysulfides, resulting in a product with diminished electrochemical activity compared to polysulfides themselves, thus escalating resistance and irreversibility within Li-S batteries (Figure and Figure ). To delve deeper into the exact composition of this product and its consequential impact on Li-S battery performance, we conducted XANES experiments on the product derived from BNC and various polysulfides (Figures ). Precipitates were collected from a BNC solution of higher concentration (0.11 M) mixed with Li2Sx (where x=8, 6, 4, 1) to ensure an ample supply of samples for XANES analysis. Figures showcase the microscopic appearance of the precipitates captured by the synchrotron facility detector, while . highlights the modification of the Li-ion solvation structure. The resulting kinetics improvement is further supported by activation energy comparisons through in situ EIS and spectroscopic analyses via operando Raman and operando XAS, the latter of which was deconvoluted using MCR-ALS techniques. CV with Randles-Sevcik analysis also shed light on the kinetics improvement. Moreover, BNC also acts as a polysulfide mediator to anchor the soluble polysulfides, as demonstrated by XRF mapping and XANES analyses, which is particularly evident when comparing anode and cathode surfaces exposed to varying cycle numbers. Furthermore, we investigated the optimization of BNC concentration to avoid polysulfides depletion. Nonetheless, the specific composition of this product warrants further investigation.