FeCo/Fe₃C-cross-linked N-doped carbon via synergistic confinement and efficient catalyst to enable high-performance Li-S batteries

Lithium-sulfur batteries (LSB) with high specific energy capacity and low material costs promise to be the next generation of energy storage devices. However, their commercialization is holding back by the poor cycling stability and fast capacity fading resulting from the shuttle effect and slow redox reaction. In this work, the FeCo/Fe₃C-CNC composite was prepared by anchoring FeCo/Fe₃C nanoparticles onto the crosslinked N-doped Carbon (CNC). The results showed that the addition of Co element improved the electrochemical activity of Co-Fe alloy through tuning the electronic structure of Fe atoms. The carbon nanotubes (CNTs) grown around Co-Fe alloy and Fe₃C nanoparticles exhibited a strong affinity to polysulfide species and superior catalytic capability as nano-reactors. The N-doping CNTs/carbon sheets (CS) facilitated the formation of Li₂S compound by promoting the Li⁺ ions transport while hindering the polysulfide shuttle effect. Hence, the issues of slow redox reactions and loss of polysulfide species were effectively rectified. As a result, the composite cathode FeCo/Fe₃C-CNC-based LSB delivered a good specific capacity of 1401 mAh g⁻¹ at 0.1C, and a low apacity fading rate of 0.029% per cycle at 1C. Besides, the structural stability of the FeCo/Fe₃C-CNC composite confirms its potential for the deployment in LSB applications.