A Universal MOF‐Confined Strategy to Synthesize Atomically Dispersed Metal Electrocatalysts Toward Fast Redox Conversion in Lithium‐Sulfur Batteries

Abstract

AbstractAccelerating catalytic conversion of lithium polysulfides (LiPSs) is a promising way to address the shuttle effect of lithium‐sulfur (Li‐S) batteries but remains a challenge to date. Herein, a universal metal‐organic framework (MOF)‐confined strategy is proposed to fabricate atomically dispersed metal catalysts (ADMCs) with the help of ethylenediaminetetraacetic acid (EDTA) toward fast redox conversion in Li‐S batteries. In the synthesis, the EDTA acts as not only the coupling agent for the chemical bonding with unsaturated sites of MOF but also the chelating agent for metal ion capture and further confining them into MOF. As a proof of concept, the ADMCs made of transition metal sites anchored on MOF‐808 (named MOF‐808‐M, M = Fe, Co, Ni, Cu, Zn, etc.) are obtained, with well‐defined M‐N2O2 configurations. The in‐depth experiments and theoretical calculations reveal that the atomically dispersed M‐N2O2 sites are capable of enhancing the chemical affinity of MOF‐808‐M toward LiPSs and further accelerating their redox conversion by reducing the energy barrier of the rate‐limiting step. As a result, the assembled Li‐S batteries with S@MOF‐808‐M cathode, represented by S@MOF‐808‐Zn exhibit a high reversible specific capacity of 1192 mAh g−1 at 0.1 C, excellent rate capability of 599 mAh g−1 at 2 C, and remarkable long‐term cycling stability with a capacity retention rate of 94.6% after 300 cycles at 1 C. Moreover, the high areal capacity of 4.79 mAh cm−2 at 0.2 C with a sulfur loading of 5.14 mg cm−2 for S@MOF‐808‐M cathode can be achieved. This work presents a universal strategy to fabricate ADMCs with well‐defined active centers by combining the advantages of MOF for Li‐S batteries.