Highly stabilized sulfur cathode with natural fenugreek gum as binder

Abstract

• Natural polymer FG is proposed as a new cathode binder for Li/S cells. • FG provides the cathode with better structure integrity than PVDF. • FG can suppress the shuttle effect in Li/S cells. • The cells with FG present excellent cycling stability and rate capability. To address instability of sulfur cathode in lithium-sulfur batteries, we propose a novel binder, a water-soluble natural polymer fenugreek gum (FG). Physical characterizations demonstrate that FG exhibits outstanding mechanical strength, adhesion and ductility compared with traditional binder polyvinylidene fluoride (PVDF). Especially, FG possesses strong adsorption capability to trap the polysulfieds, as verified by immersion tests and density functional theory calculations. With these features, FG as binder provides the sulfur cathode with remarkable cycling stability, which presents a capacity retention of 91.6% with a Coulombic efficiency of 98.7% after 250 cycles at 0.5 C, compared to the 62.9% and 95.4% of the sulfur cathode using PVDF as binder. Impressively, FG outperforms other natural polymers that have been reported as the binders of sulfur cathodes.