Revealing Performance Enhancement Mechanism for Lithium–Sulfur Battery Using In Situ Electrochemical‐Fluorescence Technology

Abstract Lithium–sulfur batteries (LSBs) as a next‐generation promising energy storage device have a great potential commercial application due to their high specific capacity and energy density. However, it is still a challenge to real‐time monitor the evolution process of polysulfides during the LSBs discharge process. Herein, an in situ electrochemical‐fluorescence technology is developed to measure the fluorescence intensity change of cadmium sulfide quantum dots (CdS QDs) during the LSBs discharge process in real‐time, which could monitor the evolution process of polysulfides. First, the real‐time fluorescent spectrum and confocal fluorescence imaging of discharge processes for LSBs with CdS QDs are integrally illustrated. Furthermore, the fluorescence spectra and imaging results show that CdS QDs could immobilize polysulfides through bonding with polysulfides to improve the LSB device performance. This in situ electrochemical‐fluorescence technology provides a new in situ and real‐time‐monitor method for better understanding the working mechanism of LSBs.