Fe, N co-doped mesoporous carbon spheres as barrier layer absorbing and reutilizing polysulfides for high-performance Li-S batteries

Lithium-sulfur (Li-S) batteries have been considered as a promising substitute for lithium-ion batteries because of their high theoretical specific capacity, low cost, and environmental friendliness. However, the further practical application of Li-S batteries is greatly limited by the intrinsic insulation of sulfur, the shuttle effects of polysulfides and sluggish kinetics of the redox reaction. Herein, a well-designed Fe, N co-doped mesoporous carbon sphere (Fe-N-MCS) was fabricated to modify separator for absorbing and reutilizing polysulfides in high-performance Li-S batteries using cost-effective S cathode. The obtained Fe-N-MCS was not only acted as a physical barrier layer to block polysulfides, but also as trapper to capture and anchor polysulfides due to its highly porous structure and N dopants in the carbon frameworks. Furthermore, the high-conductive Fe-N-MCS barrier layer can facilitate electron and ion transfer to improve the electrochemical reutilization of polysulfide trapped therein, because the Fe-NMCSs exhibited high catalytic activity for enormously boosting the redox kinetics of polysulfides. In consequence, the Li-S batteries with Fe-N-MCS modified separator exhibited high reversible capacity, superior rate capability and impressively cycling stability. The construction of non-precious metal barrier layer with catalyst activity is a promising pathway for the development of high-energy-density Li-S batteries. [GRAPHICS] .