Reversible insertion/extraction of polysulfides into/from polyaniline as an effective strategy to confine polysulfides in lithium-sulfur batteries

Being a promising candidate for the next-generation rechargeable batteries, lithium-sulfur (Li-S) batteries are suffering from a rapid capacity fade due to the shuttling of soluble polysulfides, which restricts their application in many areas. In this report, we introduced an effective strategy to immobilize soluble polysulfides by insertion/extraction of polysulfides into/from polyaniline (PANI). Two kinds of C-S@PANI composites, proton acid-doped PANI and proton acid dedoped PANI, were synthesized and utilized to assemble batteries, and their electrochemical properties were carefully compared by CV, FT-IR, and EQCM experiments. It is found that C-S@PANI composite with dedoped PANI delivers higher specific capacity and elegant cycle stability compared with the C-S@PANI with doped PANI composite. Polysulfides can be reversibly inserted into and extracted from dedoped PANI chains during the charge/discharge process, indicating a confining effect of polysulfides. In contrast, polysulfides could not easily insert into or extract from doped PANI with very poor solubility. Therefore, the immobilizing of polysulfides combined with good solubility of dedoped PANI, less side reaction between dedoped PANI and polysulfides and no corrosion of the current collector, gives the C-S@PANI composite with dedoped PANI good performance in lithium-sulfur batteries.