Semi-Immobilized\nMolecular Electrocatalysts for High-Performance\nLithium–Sulfur Batteries

Abstract

Lithium–sulfur\n(Li–S) batteries constitute promising\nnext-generation energy storage devices due to the ultrahigh theoretical\nenergy density of 2600 Wh kg^–1. However, the multiphase\nsulfur redox reactions with sophisticated homogeneous and heterogeneous\nelectrochemical processes are sluggish in kinetics, thus requiring\ntargeted and high-efficient electrocatalysts. Herein, a semi-immobilized\nmolecular electrocatalyst is designed to tailor the characters of\nthe sulfur redox reactions in working Li–S batteries. Specifically,\nporphyrin active sites are covalently grafted onto conductive and\nflexible polypyrrole linkers on graphene current collectors. The electrocatalyst\nwith the semi-immobilized active sites exhibits homogeneous and heterogeneous\nfunctions simultaneously, performing enhanced redox kinetics and a\nregulated phase transition mode. The efficiency of the semi-immobilizing\nstrategy is further verified in practical Li–S batteries that\nrealize superior rate performances and long lifespan as well as a\n343 Wh kg^–1 high-energy-density Li–S pouch\ncell. This contribution not only proposes an efficient semi-immobilizing\nelectrocatalyst design strategy to promote the Li–S battery\nperformances but also inspires electrocatalyst development facing\nanalogous multiphase electrochemical energy processes.