Oversaturated iron sites on mesopore-rich carbon nanocages boost adsorption and transformation of polysulfides for lithium–sulfur batteries

Abstract

Lithium–sulfur (Li–S) batteries have attracted considerable interest owing to their ultrahigh energy density and abundant sulfur resources. However, the practical implementation of Li–S batteries is hindered by the adverse shuttling effect and retarded redox conversion of polysulfides. Herein, oversaturated Fe–N₅ moieties incorporated into mesopore-rich N-doped carbon nanocages (Fe–NCNCs) are constructed as a multifunctional sulfur host for Li–S batteries. The Fe–N coordination centres on Fe–NCNCs can firmly adsorb polysulfides and facilitate the generation and decomposition of Li₂S during discharging and charging processes. The nanocage structure of Fe–NCNCs enables fast charge transfer, accommodates volume fluctuation during cycling, and provides strong physical confinement of polysulfides. Accordingly, the Li–S battery with the Fe–NCNC/S cathode delivers a high reversible capacity, superior rate performance and long-term cycle stability. This work will inspire the rational design of functional sulfur hosts with atomically dispersed metal sites for advanced Li–S batteries.