The Role of Electrolyte Additives on the Stability and Electrochemical Performance of Lithium-Sulfur Batteries

Abstract

Lithium-sulfur batteries (LSBs) are attractive owing to their high theoretical energy density (2600 Wh kg-1)1, low cost, and natural abundance. However, a major drawback of LSBs is an uncontrolled lithium dendrite formation during cycling leading to serious safety issue, low Coulombic efficiency and poor cycle performance. To overcome this drawback, electrolyte additives are typically used to control the lithium dendrite growth by chemically forming stable solid-electrolyte interphase (SEI) above the metallic Li anode. The SEI layers are formed via several steps with rather complex mechanisms2. To elucidate the mechanisms of SEI formation, in this work, many electrolyte additives with different anions (e.g., LiNO3, LiClO4, LiBr, LiI, LiBF4) have been investigated using computational chemistry calculations along with the experimental study to gain fundamental understanding. The different additives exhibit different reaction pathways with LiTFSI to form the decomposed products over lithium surface and directly correlate to the evolution of LiF. This affects the cell performance in terms of the coulombic efficiency and capacity retention. For example, the LiNO3 provides the highest efficiency while it gives poor capacity retention. LiClO4 can provide high capacity retention over cycling. We believe that this work will provide the understanding of the effect of the additives that can enhance overall performance and safety of lithium-sulfur batteries. REFERENCES Chen, L.; Shaw, L. L. J. Power Sources 2014, 267, 770-783.Lili, W.; Yusheng, Y.; Nan, C.; Yongxin, H.; Li, L.; Feng, W.; Renjie, C. Adv. Funct. Mater. 2018, 0 (0), 1800919. Figure 1