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 Li2S and Li2S2 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 Li2S and Li2S2 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.