Promoting polysulfide conversion by catalytic ternary Fe3O4/carbon/graphene composites with ordered microchannels for ultrahigh-rate lithium-sulfur batteries
As a promising energy storage system, the sluggish reaction kinetics and shuttle effect caused by the dissolution of lithium polysulfide limit the practical application for Lithium-sulfur (Li-S) batteries and their substantial commercialization. Herein, a significant improvement of conversion kinetics and areal sulfur loading is achieved by an ordered microchannel graphene scaffold with incorporated catalytic Fe3O4 nanocrystals and porous carbon as a multifunctional sulfur host. The synergy between the polar catalytic Fe3O4 nanocrystals and porous carbon frameworks enables a strong polysulfides anchoring effect and a fast polysulfides conversion rate. Thus, the 3D ternary Fe3O4/porous carbon/graphene aerogel demonstrates ultrahigh rate performance of 755 mAh g-1 at 3 C and a high areal capacity of 6.24 mAh cm-2 at a sulfur loading of 7.7 mg cm-2. Moreover, the promoted reaction kinetics and reliable cycliability are revealed by visible evolution of polysulfides detected using in situ X-ray diffraction (XRD), and the enhanced chemical anchoring of polysulfides is disclosed by density functional theory (DFT) calculation, which are vital to the superb lithium sulfur batteries. This work provides a promising approach to develop multifunctional 3D interconnected porous aerogel with metal oxide nanocrystals for high-performance Li-S batteries, especially those suffer from low sulfur loading and inferior rate performance.