Lithium/sulfur (Li/S) cells have great potential to become mainstream secondary batteries due to their ultra-high theoretical specific energy. The major challenge for Li/S cells is the unstable cycling performance caused by the sulfur's insulating nature and the high-solubility of the intermediate polysulfide products. Several years of efforts to develop various fancy carbon nanostructures, trying to physically encapsulate the polysulfides, did not yet push the cell's cycle life long enough to compete with current Li ion cells. The focus of this review is on the recent progress in chemical bonding strategy for trapping polysulfides through employing functional groups and additives in carbon matrix. Research results on understanding the working mechanism of chemical interaction between polysulfides and functional groups (e.g. O-, B-, N-and S-) in carbon matrix, metal-based additives, or polymer additives during charge/discharge are discussed.

Conductive polymer coatings can boost the power storage capacity of lithium-sulfur batteries. We report here on the design and preparation-by combining a facile and green chemical deposition method with an oxidative polymerization approach-of polyaniline (PANI)-modified cetyltrimethylammonium bromide (CTAB)-graphene oxide (GO)-sulfur (S) nanocomposites with significantly enhanced performance in lithium-sulfur batteries. Such conductive polymer modified CTAB-GO-S nanocomposites as sulfur cathode materials can deliver high specific discharge capacities and long-term cycling performance, i.e., ~970 mAh·g^-1 at 0.2 C and ~715 mAh·g^-1 after 300 cycles, ~820 mAh·g^-1 at 0.5 C and ~670 mAh·g^-1 after 500 cycles, ~770 mAh·g^-1 at 1 C and ~570 mAh·g^-1 after 500 cycles. The capacity decay was as low as 0.036% per cycle at 0.5 C, and 0.051% per cycle at 1 C. Under the same condition, batteries using PANI-modified CTAB-GO-S as cathodes exhibited higher specific capacity and higher average coulombic efficiency compared with CTAB-decorated GO-S and GO-S nanocomposites. The improved performance can be attributed to the lower charge transfer resistance and the alleviated dissolution of polysulfides in the PANImodified CTAB-GO-S cathodes.