Stabilizing Effect of Polysulfides on Lithium Metal Anodes in Sparingly Solvating Solvents

Abstract

Electrolytes with sparingly polysulfide solubility such as 1.5 M LiTFSI in tetramethylene sulfone (TMS) and 1,1,2,2‐tetrafluoroethyl‐2,2,3,3‐tetrafluoropropyl ether (TTE) are beneficial for the cycle stability of Li−S pouch cells. In this work, this specific electrolyte system and the role of dissolved polysulfides (PS) in symmetrical Li/Li cells is investigated. By studying varying TMS/TTE volume ratios and polysulfide addition aided by both ex situ and operando spectroscopic as well as microscopic techniques, the positive impact of PS on the lithium plating/stripping behavior is evaluated. The composition of the solid‐electrolyte interphase (SEI) as well as the microscopic morphology differs for electrolytes with PS from those without PS addition. These findings are crucial for the development of electrolytes for cycle‐stable Li−S prototype cells.

Adaptively Reforming Natural Enzyme to Activate Catalytic Microenvironment for Polysulfide Conversion in Lithium–Sulfur Batteries

“…The catalytic process of LiPSs includes two critical steps: i.e., adsorption and conversion. − The static LiPS adsorption experiments (Figure S8) convincingly demonstrate that DHcs have stronger adsorptivity toward LiPSs and substantial remediation of LiPS shuttling, which can be correlated to more available adsorbing sites on DHcs. To reveal the possible interaction mechanism between LiPSs and DHcs, XPS analyses were further performed using the spent samples after visual adsorption.…”

Operando Radiography and Multimodal Analysis of Lithium–Sulfur Pouch Cells—Electrolyte Dependent Morphology Evolution at the Cathode

“…Here, we present an operando study on Li/S monolayer pouch cells with different sulfur loadings in a carbon nanotube-based cathode scaffold and two different electrolyte systems, the standard DOL/DME (DD) electrolyte and the sparingly solvating TMS/TTE (TT) electrolyte. [22,29] The limitation to single electrode layers allows the most lucid distinction of electrolyte and active materials distribution separately with minimal interference. Observation of inhomogeneous electrolyte distribution and edge effects herein provide the basis for analysis of multilayer cells, where such effects are present as well, albeit complexed by the overlap of several stack layers in transmission images.…”

“…For example, releasing more significant amounts of polysulfides in ether‐based electrolytes with simultaneously small electrolyte volumes can cause an enormous increase in viscosity, which drastically decreases the ionic conductivity in the battery cell. [ 22 ] This process significantly reduces the energy as well as the power density.…”

Impact of Carbon Porosity on Sulfur Conversion in Li−S Battery Cathodes in a Sparingly Polysulfide Solvating Electrolyte

“…[22][23][24][25][26][27][28][29][30] One promising electrolyte system is the combination of the hydrofluoroether 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetraflurorpropyl ether (TTE) with sulfolane (tetramethylene sulfone, TMS). [31,32] Using the TMS/TTE electrolyte stable cycling performance on pouch cell level (3.7 Ah) has been already demonstrated at very low electrolyte amount of 2.6 μl mg S À 1 . [31] By developing new electrolyte formulations with reduced LiPS solubility often a standard sulfur cathode containing commercial carbon black or self-developed carbon material is used.…”

“…Hence, non‐solvating hydrofluorinated ethers (HFE) as “diluent” have been introduced to create sparingly solvating electrolytes [22–30] . One promising electrolyte system is the combination of the hydrofluoroether 1,1,2,2‐tetrafluoroethyl‐2,2,3,3‐tetraflurorpropyl ether (TTE) with sulfolane (tetramethylene sulfone, TMS) [31,32] . Using the TMS/TTE electrolyte stable cycling performance on pouch cell level (3.7 Ah) has been already demonstrated at very low electrolyte amount of 2.6 μl mg S −1 [31] …”