Porous Organic Cage as a Sulfur Host for Upgrading Capacity and Longevity of Li–S Batteries

Abstract

Suffering from the severe shuttle effect, constructing high-performance lithium–sulfur (Li–S) batteries with high capacity and prolonged cycling life remains a great challenge. Developing porous host materials for sulfur loading remains a tendency. Porous organic cages (POCs), as a kind of porous material, exhibit potential in energy storage and conversion because of their inherent cavities and plentiful active sites. Herein, two POC materials of CPOC-301 and HPOC-401 with large octahedral cavities and abundant N and O heteroatoms were explored as host materials for loading a high sulfur content of 84 wt % in Li–S batteries. The resulting CPOC-301-S and HPOC-401-S cathodes exhibit improved electrochemical performances with high specific capacity (1302 and 1109 mA h g–1 at 0.05 C, respectively) and excellent cycling reversibility and stability (a low average capacity fading rate of 0.015% for 2500 cycles at 5 C for CPOC-301-S). Moreover, the interconversion of keto-enamine in CPOC-301 could accelerate the redox kinetics. This work provides the blueprint for POC families applied as promising host materials for advanced Li–S batteries.