Heteroatom-doped ZIF-67 for anchoring and catalyzing polysulfides in lithium-sulfur batteries

The performance and stability of lithium-sulfur (Li-S) batteries are significantly impeded by the shuttle effect of lithium polysulfides (LiPSs) and the sluggish redox kinetics. Herein, a series of heteroatom-doped ZIF-67-600/X (X: N, P, and S) composites were synthesized as sulfur host materials using ZIF-67 as a template, involving steps such as carbonization and heteroatom-doped. Experimental findings indicate that the N-doped ZIF67-600composites exhibit optimal catalytic performance, superior reversibility, and optimized electrochemical kinetics during the conversion process of soluble lithium polysulfide to insoluble Li2S2/Li2S. Density functional theory (DFT) calculations reveal that N-doped ZIF-67-600composites exhibit the robust Li2S8 adsorption capacity, and it is more favorable for the transition from soluble LiPSs to insoluble Li2S2. The outstanding adsorption capacity and liquid-solid phase conversion kinetics significantly reduce the concentration of soluble LiPSs in the electrolyte. Batteries assembled with ZIF-67-600/N@S electrodes demonstrate substantially enhanced specific capacity, rate performance, and cycling stability. Notably, over 1000cycles at a 2.0C rate, the capacity decay is a mere 0.023 % per cycle. This work provide promising insights into the understanding of design and modification for high-performace catalytic materials in Li-S batteries.