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

Abstract 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-N-MCSs 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. Graphical abstract The polysulfides were anchored and reutilized by the Fe-N-MCS layer for high-performance lithium sulfur battery.