Newly comprehensive understanding of Li_2S_8 as additive in liquid electrolyte for lithium-sulfur battery through reconstructing the cathode and SEI

摘要

Adding Li2S8 as additive in liquid electrolyte (LE) for lithium-sulfur battery (LSB) is one of the most effective strategies which not only suppresses the shuffle effect of lithium polysulfide (LPS) through concentration difference but also maintains the excellent properties of ether-based electrolyte. However, previous researches on this strategy mostly focus on low-concentration Li2S8 additive (no more than 0.2 mol/L), which cannot provide comprehensive understanding of the special role of Li2S8. In this study, high-concentration Li2S8 is selected as the LE additive which is demonstrated inducing two marvelous reconstruction effects that have not been reported both for the cathode and solid electrolyte interphase (SEI). Through these two effects, the cathode and SEI are reconstructed to form denser and more stable structures, ensuring the battery to possess much higher discharge specific capacity and excellent cycle stability, with a Coulombic efficiency (CE) fade of only 0.091% per cycle. This exploration of Li2S8 additive helps to better understand the role of electrolyte additive and how the concentration of it influences the whole battery system.