Improved Cycling Performance Using a Poly-2-Acrylamido-2-Methylpropanesulfonic Acid (AMPS)-Based Crosslinked Gel Polymer on a Sulfur Cathode for Inhibiting the Dissolution of Polysulfide in a Li-S Battery

In lithium-sulfur (Li-S) batteries, the impregnation of sulfur into electrically conductive materials of porous carbon plays a significant role in preventing the dissolution of lithium polysulfide (LiPS) into an electrolyte solution and improving cycling performance. However, this strategy does not render high-energy density to Li-S cells because of the limited amount of sulfur in porous carbon. Once the sulfur overflows out of porous carbon because of the significant volume change occurring during charge-discharge cycling, the LiPS formed outside porous carbon probably diffuses toward the anode, leading to poor cycling performance. In this study, the poly-2-acrylamido-2-methylpropanesulfonic acid (AMPS)-based polymer incorporated into the sulfur/porous carbon composite cathode in a Li-S cell effectively suppresses LiPS dissolution even when sulfur is present outside porous carbon, achieving good cycling performance with a capacity retention of 72% at the 100th cycle. Herein, the polymer used is poly-AMPS with a crosslinker of N-[tris(3-acrylamidopropoxymethyl)methyl]acrylamide, which is synthesized using 2-hydroxy-2-methylpropiophenone as the photoinitiator. The characteristics of the as-synthesized AMPS-based polymer and sulfur-carbon composite cathode are meticulously investigated by scanning electron microscopy-energy-dispersive X-ray spectrometry, transmission electron microscopy, dynamic light-scattering analysis, thermogravimetric analysis, and X-ray diffraction.