Enhanced Cyclability for Sulfur Cathode Achieved by a Water-Soluble Binder

Abstract

The electrochemical properties of sulfur cathodes based on commercially available sulfur powder (S) and water-soluble binder have been investigated. The mixture of styrene butadiene rubber (SBR) and sodium carboxyl methyl cellulose (CMC) is used as the binder. Compared with conventional poly(vinylidene fluoride) (PVDF) binder, the SBR–CMC binder significantly improves cycling performance of the sulfur cathode. A high specific capacity of 580 mA h g –1 after 60 cycles has been achieved. Studies on the electrode slurries show that the SBR–CMC mixture is not only a high adhesion agent but also a strong dispersion medium, which favors the uniform distribution between insulating sulfur and conductive carbon black (CB) and ensures a good electrical contact, leading to a high sulfur utilization. Furthermore, our experiments show that the improvement in cyclability is ascribed to structural stability of the sulfur cathode promoted by the SBR–CMC binder during charge/discharge cycles due to the combined effects of homogeneous distribution of the S and CB particles in the composite cathode, the low electrolyte uptake, and the suppressed agglomeration of Li 2 S.