Bifunctional Mott-Schottky-type Co-Fe3N electrocatalyst as sulfur host and separator modifier to enhance the transformation kinetics of Li2S

Abstract

Recently, lithium-sulfur batteries (LSBs) with ultra-high theoretical energy density attract the attention of researchers. However, the shuttle of lithium polysulfides (LPSs) seriously restrict the development of LSBs. Here, Co-Fe3N with Mott-Schottky type exhibits exceptional chemisorption and catalytic capabilities towards LPSs. The Co-Fe3N Mott-Schottky heterojunction induces charge redistribution at the heterogeneous interface, thereby increasing the rate of charge transfer, enhancing chemisorption ability, and reducing the energy barrier for S8 reduction and Li2S oxidation. The Co metal provides more catalytic and adsorption active sites for the conversion of LPSs and further improves the catalytic activity of Fe3N. Under the synergistic effect of the metal Co and Fe3N, the redox reaction of LPSs is improved, and the nucleation/decomposition energy barriers of Li2S are decreased, realizing the multifunctional coupling of adsorption-catalytic-conversion of LPSs. The LSBs with Co-Fe3N/S cathode and Co-Fe3N-PP separator exhibits a low capacity decay of 0.067 % per cycle at 1 C during 400 cycles. Even at a high sulfur loading of 3.1 mg cm−2, the LSBs delivers a reversible capacity of 1016 mA h g−1 at 0.1 C. The utilization of the Co-Fe3N with Mott-Schottky type in LSBs presents a novel approach towards designing multifunctional coupled materials with adsorption-catalysis-conversion capabilities.