Fe3O4 nanoparticles encapsulated in graphitized and in-plane porous carbon nanocages derived from emulsified asphalt for a high-performance lithium-ion battery anode

In this work, C@Fe₃O₄ composites were prepared through a typical template method with emulsified asphalt as carbon source, ammonium ferric citrate as transition metal oxide precursor, and NaCl as template. As an anode for lithium-ion batteries, the optimized C@Fe₃O₄-1:2 composite exhibits an excellent reversible capacity of 856.6 mA·h·g⁻¹ after 100 cycles at 0.1 A·g⁻¹ and a high capacity of 531.1 mA·h·g⁻¹ after 300 cycles at 1 A·g⁻¹, much better than those of bulk carbon/Fe₃O₄ prepared without NaCl. Such remarkable cycling performance mainly benefits from its well-designed structure: Fe₃O₄ nanoparticles generated from ammonium ferric citrate during pyrolysis are homogenously encapsulated in graphitized and in-plane porous carbon nanocages derived from petroleum asphalt. The carbon nanocages not only improve the conductivity of Fe₃O₄, but also suppress the volume expansion of Fe₃O₄ effectively during the charge–discharge cycle, thus delivering a robust electrochemical stability. This work realizes the high value-added utilization of low-cost petroleum asphalt, and can be extended to application of other transition-metal oxides-based anodes.