Dynamics of Polysulfide Dissolution for Various Electrolytes in Working Li-S Battery By in-Operando Technology

The lithium-sulfur (Li-S) battery is a promising electrochemical system as a high-energy storage device. However, the performance of Li-S battery is strongly limited by the S insulation, dissolution of lithium polysulfide (PS) and high self-discharge rate. These problems can lead to short cycle life and poor efficiency for application. Therefore, the LiNO₃ mixed in the electrolyte or used high lithium salt concentration electrolyte was studied, the results showed that coulombic efficiency was enhanced substantially when this additive was used, indicating that the PS/lithium reaction and PS shuttling were decreased.

In this study, we examined the interplay between PS diffusion and cycle processes. Moreover, we was designed to test PS migration in electrolytes featuring distinct salt concentrations, and in-operando TXM (Transmission X-Ray Microscopy) analysis (Fig. 1) was used to study the dynamics of PS dissolution. These findings demonstrated that using the lithium salt at a high concentration in the electrolyte enhanced the electrochemical performance of the battery. The S particle did not dissolve completely until the middle of the 2^nd plateau of the lithiation process at high lithium salt concentration, indicating that the dissolution that occurs during lithiation was delayed.

The results presented here demonstrate that using electrolytes containing a lithium salt at a high concentration can not only inhibit the dissolution of lithium PS but also effectively retard the migration of the lithium PS in the electrolyte, which substantially enhances the electrochemical performance of the battery. We believed that the strategy of developing a hybrid electrolyte by incorporating lithium salt and liquid PS is a very promising electrolyte for long cycling Li-S battery.