MOF-derived hierarchical CoP nanoflakes anchored on vertically erected graphene scaffolds as self-supported and flexible hosts for lithium–sulfur batteries

Abstract

Lithium–sulfur (Li–S) batteries have garnered a lot of attention in the realm of electrochemical energy storage owing to their high energy and low cost. However, the serious polysulfide shuttle effect of the sulfur cathode poses a critical challenge for the development of Li–S batteries with elevated sulfur loadings. In addition, the poor robustness of traditional blade-casting cathodes greatly impedes the practical applications of flexible Li–S cells that display high areal capacity. To address these concerns, we report herein a freestanding hybrid sulfur host via in situ crafting of flexible carbon cloth (CC), vertically grown graphene nanoflakes over CC (G/CC) and metal–organic-framework derived CoP anchored on vertical graphene (CoP@G/CC). The thus-derived sulfur cathodes (CoP@G/CC-S) with a typical sulfur loading of 2 mg cm⁻² exhibit outstanding electrochemical performances, including excellent rate capability (930.1 mA h g⁻¹ at 3.0C) and impressive cycling stability (0.03% capacity decay per cycle after 500 cycles at 2.0C). A high areal capacity of 8.81 mA h cm⁻² at 0.05C can also be obtained even at an elevated sulfur loading of 10.83 mg cm⁻². Furthermore, flexible pouch cells based on the self-supported CoP@G/CC-S showcase favorable rate and cycling performances with high mechanical robustness.