The Effect of Monomers of Conducting Polymer in the Electrolytes on the Electrochemical Behavior of Lithium-Sulfur Batteries

摘要

The recent demand for the energy storage system with a higher energy density has turned the attention to the lithium-sulfur (Li-S) batteries due to its higher gravimetric/volumetric capacities (1672 mAh g~(-1) and 3467 mAh cm~(-3), respectively) than the metal oxide-based cathodes (e.g., 148 mAh g~(-1) and 1363 mAh cm~(-3) for LiCoO_2) However, in the Li-S batteries the intermediate lithium-polysulfides (LiPS) dissolve into the electrolyte followed by their shuttle between Li metal anode and S cathode, which is called the shuttle effect, has led to the performance degradation of Li-S batteries. Thus, the strategies that reduce the dissolution of the LiPS from the cathode side, for example forming a chemical/physical protective layer on S cathode, have been mainly studied. Among them, adding an additive into the electrolytes that can form a protective layer on S cathode during charge/discharge or pre-treatment has been considered as an effective way because it has achieved the improvement of electrochemical performance by more facile and cost-effective method compared to the ex-situ methods. However, the effect of electrolyte additives and their chemical/physical change during electrochemical treatment (or cycling) on the electrochemical behavior of Li-S batteries have been rarely studied. In particular, the effect of electrochemical variables (current or voltage), which determines the electrochemical behavior of Li-S batteries and consequent electrochemical performance, has been not fully understood, therefore is needed to be delineated in detail.