The synergetic interaction between LiNO₃ and lithium polysulfides for suppressing shuttle effect of lithium-sulfur batteries

LiNO₃ has been widely used as an effective electrolyte additive in lithium-sulfur (Li-S) batteries to suppress the polysulfide shuttle effect. To better understand the mechanism of suppressed shuttle effect by LiNO₃, herein we report a comprehensive investigation of the influence of LiNO₃ additive on the formation process of the solid electrolyte interphase (SEI) layer on lithium anode of Li-S batteries by operando X-ray absorption spectroscopy (XAS). We observed that a compact and stable SEI layer composed of Li₂SO₃ and Li₂SO₄ on top of lithium anode is formed during the initial discharge process due to the synergetic effect of shuttled polysulfides and LiNO₃, which can effectively suppress the subsequent reaction between polysulfides in electrolyte and lithium metal and thus result in the alleviation of polysulfide shuttle effect. In contrast, when using electrolyte without LiNO₃, the shuttled polysulfides continuously react with lithium metal to form insulating Li₂S on lithium anode, leading to the irreversible capacity loss. Our present operando XAS study provides a valuable insight into the important role of LiNO₃ for the protection of lithium anodes, which will be beneficial for the further development of new electrolyte additives for high-performance Li-S batteries.