Effect of chemical reactivity of polysulfide toward carbonate-based electrolyte on the electrochemical performance of Li-S batteries

A chemical stability between polysulfides and electrolyte is considered to be crucial to achieving good electrochemical performance of lithium-sulfur (Li-S) batteries since long-chain polysulfides which dissolve easily into common electrolyte can trigger substantial electrolyte decomposition due to their nucleophilic nature. In this work, we investigated the chemical reactivity of polysulfides toward carbonate-based electrolytes through a simple probing experimental method and found that the polysulfides react with carbonate-based electrolytes via a nucleophilic addition or substitution reaction leading to a sudden capacity fading of lithium sulfur cells by loss of active sulfur. This study strongly suggests that electrolytes for Li-S system should not possess an electrophilic functionality to avoid undesired chemical reaction with polysulfides. In addition, we show that the methodology developed in this work for the verification of chemical stability between polysulfides and electrolyte can be widely applicable to screening other potential electrolyte candidates.