Water-Soluble Cross-Linking Functional Binder for Low-Cost and High-Performance Lithium-Sulfur Batteries

Binders play an important role in battery systems. The lithium-sulfur (Li-S) batteries have poor cycling performance owing to large volume alteration of sulfur and shuttle effect. Herein, a novel water-soluble functional binder (named GN-BA) is prepared by the cross-linking effect between gelatin and boric acid. The excellent binder can effectively maintain the integrated electrode stable, buffer the volume changes, prevent active materials exfoliation from current collectors, and anchor polysulfides by chemical bonding. Sulfur electrodes in this binder also exhibit a loosely stacked porous structure, which is advantageous to the electrolyte permeation and fast ion diffusion. X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, and density functional theory calculations further verified that the binder can anchor polysulfides by forming B-O-Li, C-O-Li, and C-N-Li chemical bonds. At 0.5 C, a high initial capacity of 980 mA h g(-1) can be obtained, which is higher than those sulfur cathodes with traditional poly(vinylidene fluoride) binder. When the sulfur loading is up to 5.0 mg cm(-2), a high areal specific capacity of 5.7 mA h cm(-2) and excellent cycling stability are achieved. This study proposes an economical and environmentally friendly strategy for the construction of advanced binders and promotes the practical application of high-energy Li-S batteries.