Highly branched amylopectin binder for sulfur cathodes with enhanced performance and longevity

The sulfur cathode of lithium‐sulfur (Li‐S) batteries suffers from inherent problems of insufficient mechanical strength and the dissolution of sulfur and polysulfides. Inspired by the extraordinarily resilient and strong binding force of the Great Wall binder, that is, the sticky rice mortar, we extracted highly branched amylopectin (HBA), the effective ingredient, as a low‐cost, nontoxic and environmentally benign aqueous binder for the sulfur cathode. The HBA‐based cells outperform the Li‐S batteries based on the traditional polyvinyldene diflouride (PVDF) binder and a lowly branched polysaccharide binder. The improved electrochemical performance in the HBA‐based cell could be attributed to two mechanisms. First, the branched structure of the HBA provides enhanced mechanical and adhesive properties, which allow for a robust electronic and ionic conductive framework to be maintained throughout the cathode after extended cycling. Second, the HBA shows enhanced polysulfide retention due to the polymer's abundant lone‐pair rich hydroxyl groups and the formation of C─S bonds between the HBA and polysulfides prohibits the shuttle effect of polysulfides. The improved mechanical properties and polysulfide retention function of the HBA binder facilitate the HBA‐based Li‐S battery to deliver a long cycle life of 500 cycles at 2 C while only displaying a capacity fading of 0.104% per cycle.