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

Abstract

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.