Imidazolyl ionic liquid-derived nitrogen-doped carbon layer coated Fe3O4 loaded on graphene as an advanced host for long life lithium sulfur batteries

Abstract

Lithium-sulfur batteries are regarded as promising alternatives for next-generation energy storage systems. Developing high-performance lithium-sulfur battery cathode materials requires the efficient synthesis of electrocatalysts that can both anchor LiPS and catalyze their conversion. Herein, we synthesized a composite of ionic liquid-derived nitrogen-doped carbon-coated Fe₃O₄ loaded on graphene (Fe₃O₄@NC/G) by utlizing the π-π interaction between [Bmim][FeCl₄] and graphene. Fe³⁺ ions were uniformly dispersed, effectively preventing particle aggregation during the carbonization process and producing Fe₃O₄ nanoparticles averaging 20.64 nm in size. This structure provides plentiful active sites for adsorbing and catalyzing LiPS, thereby accelerating the redox reaction. Additionally, the nitrogen-doped carbon coating not only stabilizes the Fe₃O₄ nanoparticles and firmly anchors them to the graphene nanosheets, significantly enhancing structural integrity, but also increases the adsorption of LiPS due to the introduction of the heteroatom nitrogen. The assembled LSBs demonstrated excellent cyclic stability with a capacity fade rate of 0.35 % per cycle over 1200 cycles at 1C.