Fe and Co containing N-doped graphene sulfur cathode for high performance Li–S batteries and in situ Raman investigation

Transition metal modified carbon materials hold great potential in Li–S batteries. Optimizing the electronic interaction between metal and carbon support is the key to improve the electrochemical performance of materials. Herein, unique graphene/N-doped carbon (G/FeCo@N-C) materials doped with CoFe2O4/Co3Fe7 nanoparticles were prepared by thermal decomposition of graphene-coated bimetallic metal organic frameworks. The double G/N-carbon layer not only provides abundant sulfur loading space and adsorption site but also improves the electrical conductivity of the material. CoFe2O4/Co3Fe7 nanoparticles were used as catalysts to accelerate the conversion of polysulfide. Importantly, in situ Raman spectroscopy is used to explain the mechanism of capacity attenuation of the G/FeCo@N-C-S material during charge and discharge. The electrochemical test shows that G/FeCo@N-C-S delivers a high specific capacity of 440.3 mAh g−1 after 1000 cycles with very low capacity decay of 0.042% per cycle as well as excellent rate performance. This work provides a useful approach for the rational design of bimetal-containing carbon materials to promote the electrochemical applications.