Hit two birds with one stone: A bi-functional selenium-substituted organosulfur polymer additive for high-performance lithium-sulfur batteries

Sluggish reaction kinetics of sulfur cathode and high reactivity of lithium anode hinder the commercialization of Li-S batteries. Employing the electrolyte additive to regulate the states of active material is a facile and effective way to solve the above issues. Herein, the bifunctional selenium substituted lithium polythioctic acid (PTA-Se) was prepared as an additive of electrolyte via in-situ polymerization and substitution method. Such additives can promote the conversion of polysulfides and facilitate the homogenization of Li-ion flux. The active selenium sites provide a kinetically favorable pathway for polysulfide conversion. The introduction of additives also facilitates the formation of elastic and uniform solid electrolyte phase interface (SEI) film on the surface of lithium anode. As results, Li-S batteries assembled with PTA-Se additive demonstrates a high initial capacity of 1319 mAh g-1 at 0.2C with 1000 mAh g-1 remaining after 150 cycles, corresponding to a 0.16 % capacity decay per cycle. At a high rate of 5C, the cell still achieves a reversible capacity of 517 mAh g-1. This work opens a new avenue for designing effective electrolyte additive and achieving high-performance Li-S batteries.