The influences of diameter distribution change of zeolitic imidazolate framework‐67 crystal on electrochemical behavior for lithium‐sulfur cell cathode

Abstract

To improve the electrochemical performance of Li‐S batteries, sulfur composites are prepared through sulfur's melt‐diffusion into porous materials such as metal organic frameworks (MOFs). MOFs are porous nanocrystalline materials consisting of metal ions and organic ligands. Due to their high porosity, specific surface area, and easily controllable porous structure, MOFs and their derivatives are considered useful materials for holding sulfur. Herein, the effect of the concentration of the reactants on the particle diameter distribution of ZIF‐67 is studied, and the performance of the product as a sulfur host for Li‐S battery cathode is evaluated. ZIF‐67 was prepared by regulating the Co2+ concentration in solution from 10 to 250 mM, with a constant mole ratio between Co2+ and the organic ligand. Cyclovoltammetry, galvanostatic charge–discharge, and rate capability tests were performed to electrochemically characterize each sample as a sulfur host for Li‐S battery cathodes. MeZ‐50 mM, prepared with 50 mM Co2+ ion solution, had the smallest particle diameter (591 nm). The sulfur cathode utilizing MeZ‐50 mM afforded the best electrochemical performance (883.7 mAh gS−1). This study demonstrates that the particle size of ZIF‐67 can be controlled by adjusting the reactant concentration, enabling manipulation of the electrochemical properties as a sulfur host.