l‑Cysteine-Modified\nAcacia Gum as a Multifunctional Binder for Lithium–Sulfur Batteries

Abstract

A binder plays an important role in stabilizing the electrode\nstructure and improving the cyclic stability of batteries. However,\nthe traditional binders are no longer satisfactory in lithium–sulfur\n(Li–S) batteries because of their failure in accommodating\nthe large volume changes of sulfur and trapping soluble intermediate\npolysulfides, thus causing severe capacity decay. In this work, we\nprepared a multifunctional binder for Li–S batteries by merely\nmodifying the acacia gum (AG), a low-cost biomass polymer, with l-cysteine under mild conditions. Owing to the introduced amino\nand carboxyl branches by the l-cysteine, the modified AG\nshows enhanced polysulfide trapping ability and can effectively restrain\nthe shuttling of polysulfides. In addition, the introduction of branches\ncan help form a cross-linked 3D network with better mechanical strength\nand flexibility for adhering sulfur and accommodating the volume changes\nof cathode materials. As a result, compared with the normally used\npolyvinylidene fluoride binder and the unmodified AG binder, the l-cysteine-modified AG binder effectively enhanced the rate\ncapability and cycling stability of the Li–S batteries directly\nusing sulfur as the cathode, showing a promising way to prompt the\npractical use of Li–S batteries.