Loading Fe3O4 nanoparticles on N, S co-doped graphene suppressing polysulfides conversion toward high-performance Li-S batteries

Lithium-sulfur (Li-S) batteries are the most potential energy storage system due to their high theoretical specific energy/capacity, environment friendly and low cost. Because of low conversion efficiency of middle lithium polysulfides (LiPSs), Li-S batteries still suffer from the shuttle effect. Therefore, a structure of polar ferric oxide nanoparticles on N, S co-doped graphene (Fe3O4-N, S/rGO) sheet structure to regulate LiPSs and enhance the conversion kinetics was designed, which could be of great significance for the realization of Li-S batteries with high energy density and long-term cycling life. Obviously, when compared with undoped Fe3O4-rGO composite, the N, S co-doped Fe3O4-N, S/rGO composite showed stronger LiPS chemisorption. The synergy of the Fe3O4 nanoparticles and heteroatom doping has a significant effect on shuttle effect, when worked as a mechanism to regulate LiPS conversion. The adsorption energy value from - 0.79 eV to- 8.7 eV was obtained based on the First-principle (DFT) calculations, which confirmed the strong adsorption ability of Fe3O4 toward LiPSs. Among them, the critical roles of Fe3O4-N, S/rGO and LiPSs were explored by potentiostatic discharge test, which shows a high precipitation capacity of solid Li2S. Ultimately, the assembled Fe3O4-N, S/rGO-S batteries deliver high rate capability and stable long-term cycle life. After cycling for 400th at 2 C, Fe3O4-N, S/rGO-S electrode still delivers a high discharge specific capacity of 635 mAh g(-1). This work aims to promote the commercialize of Li-S batteries for future design.

Automated summary

In order to address the shuttle effect and improve the conversion kinetics in lithium-sulfur batteries, a special structure of ferric oxide nanoparticles on N, S co-doped graphene composite was designed, which effectively regulated the formation of lithium polysulfides and enhanced the energy density and cycling life of the batteries.