Tackling the Capacity Fading Issue of Li–S Battery by a Functional Additive—Hexafluorobenzene

Due to the strong electron-withdrawing fluorine groups, the aromatic ring of hexafluorobenzene (HFB) becomes more electron-deficient and strongly interacts with the lone-pair electrons of the medium. When used as an electrolyte additive for Li–S cell, HFB preferably coordinates with low-order lithium sulfides Li 2 S and Li 2 S 2 and subsequently reacts and converts both into active aromatic sulfides—bis(pentafluorophenyl) disulfides and bis(pentafluorophenyl) polysulfides in situ —thus facilitating the utilization of the electronically insulating Li 2 S and Li 2 S 2 and improving the cycling stability of the Li–S cell. This research opens a new avenue to tackle the inherent issues associated with the Li–S chemistry.