Abstract
In this work, the stability of ether-based electrolytes for Li-S batteries is investigated with particular regard to the effect of dissolved oxygen. Specifically, the performance of two different electrolyte solvents, i.e., 1,2-dimethoxyethane and its mixture with 1,3-dioxolane (DME:DOL, 1:1 v/v), is characterized in cells assembled in dry air environment, which would substantially lower production costs with respect to inert atmosphere (Ar). Although stability of all the components would suggest that Li-S batteries built in both the environments should behave similarly, it is found that cells containing the DME:DOL-based electrolyte are rather unstable in the presence of O2 in contrast to those employing DME-based electrolyte, which show a relatively good performance. The different sensitivity toward O2 of these electrolytes is associated to the ring-opening reaction of DOL, which happens to a greater extent when O2 is present, but occurs also in its absence. Based on these results a mechanism for electrolyte degradation in Li-S cells, and its reaction with dissolved polysulfides is proposed, which rationally explain for the first time the behavior already reported in literature for these kind of batteries. These findings are also relevant to the field of Li-O2 batteries, where these ether-based electrolytes are also used.
Highlights
Sulfur has been extensively investigated as a new cathode material for secondary batteries, in order to replace metal oxides normally used in lithium-ion batteries (LIBs)
The choice of ethers as solvent comes from their stability toward polysulfides
To Lithium-Sulfur batteries (LSB), Li-O2 batteries rely on a conversion cathode, which forms highly reactive intermediates that readily react with conventional carbonate-based electrolytes, leading to their
Summary
Sulfur has been extensively investigated as a new cathode material for secondary batteries, in order to replace metal oxides normally used in lithium-ion batteries (LIBs). The superior chemical stability of ethers was shown to be relevant for Li-O2 batteries, for instance.[11] to LSBs, Li-O2 batteries rely on a conversion cathode (i.e., oxygen), which forms highly reactive intermediates that readily react with conventional carbonate-based electrolytes, leading to their. Taking this in consideration, the electrochemistry of Li-S cells in a dry air environment is assessed. Electrochemical and post mortem analysis allowed to develop a more detailed model of the chemical and electrochemical reactions that take place inside a LSB, as well as to determine which classes of solvents are less sensitive to the presence of air and could, enable the electrolyte filling step to be performed in non-inert (but still dry) environment
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