Dense and thin coating of gel polymer electrolyte on sulfur cathode toward high performance Li-sulfur battery

Abstract

Lithium-sulfur battery (LSB) has been considered as a promising energy storage technology owing to low production cost and high theoretical capacity. Unfortunately, the notorious “shuttle effect” phenomenon of polysulfides has greatly hindered its commercial applications. Herein, a coating composite cathode is fabricated via a facile phase separation approach, in which commercially available gel PVDF-HFP (poly(vinylidene fluoride-co-hexafluoropropylene)) electrolyte could be formed a thin and dense coating on sulfur cathode. Moreover, carbon nanotubes (CNTs) are employed as conducting skeleton to provide effective electron transfer pathway, which could ensure a long-term cycling life. By elaborately adjusting the concentration and thickness of gel electrolyte, coating composite cathodes with various surface morphologies are obtained. The optimized coating composite cathode with PVDF-HFP gel layer (5 wt%) exhibits a small capacity decay (0.179% per cycle) after 105 cycles at 0.5C, and an outstanding rate performance (408 mAh g−1 at 2C), which holds a great potential for large-scale applications.