Rational construction of rich coordination-unsaturated Zr-BTB electrocatalyst towards advanced lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries show great potential to achieve high-density energy storage, but their commercial application is severely hindered by the notorious shuttling effect of lithium polysulfides (LiPS) and their sluggish conversion kinetics. Herein, we develop a Quasi Zr-based metal-organic frameworks with the tritopic carboxylate ligand 1,3,5-tris(4-carboxyphenyl)benzene (BTB) microflowers with cross-linked CNTs (Q-Zr-BTB@CNTs). The deficiency of Zr-O coordination at the Zr6 node is realized via a control of the deligandation behavior, which subtly modulates the local environment and electronic structure towards enhanced chemical affinity to polysulfides. Meanwhile, the interweave of the ultrathin Q-Zr-BTB nanosheets and CNTs establishes a porous and conductive network for fast charge transfer as well as a vast exposure of active interfaces. As a result, such a combination of defect engineering and architecture construction imposes strong sulfur adsorption and catalyzation, endowing the S/Q-Zr-BTB@CNTs cathode with a high initial capacity (1130 mAh g-1 at 0.2 C) and an excellent cycling stability (500 cycles at 1 C with 0.05% decay per cycle), as well as a decent electrochemical performance even under a high sulfur loading up to 12.7 mg cm-2. This study provides a novel strategy of designing unsaturated coordination centers to boost sulfur catalysis for high-performance lithium sulfur batteries.

Automated summary

This study develops a composite material based on Zr metal-organic frameworks and establishes an interweaved structure of ultrathin nanosheets and CNTs, which provides a porous and conductive network for fast charge transfer and active interface exposure. The composite material shows high initial capacity and excellent cycling stability, as well as decent electrochemical performance even under high sulfur loading.