Modulation of Potential‐Limiting Steps in Lithium–Sulfur Batteries by Catalyst Synergy

Abstract

AbstractElectrocatalysis is considered to be an effective method to solve the sluggish kinetics of lithium–sulfur batteries. However, a single catalyst cannot simultaneously catalyze multi‐step sulfur reductions. And once the catalyst surface is covered by the initially deposited solid products, the subsequent catalytic activity will significantly deteriorate. Here, microporous ZIF‐67 and its derivative nano‐metallic Co0 are used as dual‐catalyst aiming to address these drawbacks. The dual catalytic center effectively cooperates the adsorption and electron transfer for multi‐steps of sulfur reductions, transforming the potential‐limited step (Li2S4→Li2S2/Li2S) into a thermodynamic spontaneous reaction. ZIF‐67 first adsorbs soluble Li2S4 to form a coordination structure of ZIF‐Li2S4. Then nano‐metallic Co0 attracts uncoordinated S atoms in ZIF‐Li2S4 and facilitates the breaking of S–S bonds to form transient reductive ZIF‐Li2S2 and Co‐S2 via. spontaneous electron transfer. These intermediates facilitate continuous conversion to Li2S with reduced formation energy, which is beneficial to the regeneration of the catalyst. As a result, the cathode with ZIF@CNTs/Co@CNFs synergetic catalyst achieves initial areal capacity of 4.7 mAh cm−2 and maintains 3.5 mAh cm−2 at low electrolyte/sulfur ratio (E/S) of 5 µL mg−1. This study provides valuable guidance for improving the electrochemical performance of lithium–sulfur batteries through catalyst synergistic strategies for multi‐step reactions.