Interface covalent bonding endowing high-sulfur-loading paper cathode with robustness for energy-dense, compact and foldable lithium-sulfur batteries

Abstract

Lithium-sulfur batteries are promising candidates for powering flexible devices with high energy densities. To realize both high areal and volumetric capacity of lithium-sulfur batteries, while maintaining flexible and mechanically robust characteristics, is challenging for their portable energy storage applications. Herein, interface covalent bonding was demonstrated to design densely-packed graphene/CoS2/nano-sulfur hybrid papers with flexible and robust characteristics for energy-dense, compact and foldable lithium-sulfur batteries. The as-designed paper cathodes showed excellent cycling stability with a low decay rate of 0.044% per cycle over 800 cycles at 1 C, as well as high reversible areal capacity (4.11 mAh cm−2) and volumetric capacity (1240 Ah L−1). Meanwhile, the assembled batteries performed a high gravimetric/volumetric energy density (363.5 Wh kg−1/378 Wh L−1) under high sulfur loading (5.6 mg cm−2) and lean electrolyte/sulfur ratio (E/S: 5 μL mg−1). Furthermore, durable pouch cells based on as-designed integrated paper cathodes showed negligible performance decay even at a folding angle of 180°, highlighting their practical applications for flexible power systems.