Carbon nanofibers embedded with tiny CoNi bimetals as the functional interlayer for high-performance lithium-sulfur batteries

Free-standing carbon nanofibers have been recognized as an effective interlayer to improve sulfur cathode electronic conductivity and inhibit shuttling of polysulfides. However, carbon materials show a limited effect on improving electrochemical performance of lithium-sulfur batteries (LSBs) due to their nonpolar and weak physical limitations for the dissolvable polysulfides. It has been reported that introducing chemical bonds between polar compounds and polysulfides helps to suppress the shuttle effect of polysulfides via combining physical confinement with chemical adsorption. Herein, free-standing N-doped carbon nanofibers embedded with bimetallic CoNi (CoNi@N-CNFs) are constructed as an interlayer for LSBs. Apart from improving electronic conductivity of the sulfur cathode, the CoNi@N-CNF interlayer also displays excellent adsorption ability to the dissolvable polysulfides and promotes conversion reactions between sulfur species. Under the synergistic effect of the carbon framework and CoNi bimetals, the CoNi@N-CNF interlayer achieves decent electrochemical performance with a high initial discharge capacity of 1563 mAh g(-1) at 0.2C and 0.53% capacity decay per cycle during 100 cycles.