Synthesis of uniform and superparamagnetic Fe3O4 nanocrystals embedded in a porous carbon matrix for a superior lithium ion battery anode

Abstract

A facile and scalable strategy for the synthesis of discrete, homogeneous and small (mostly 5–15 nm) Fe₃O₄ nanocrystals embedded in a partially graphitized porous carbon matrix was developed, which involved the simple mixing of a metal precursor (Fe(NO₃)₃·9H₂O), a carbon precursor (C₆H₈O₇), and a dispersant (NaCl) in an aqueous solution followed by calcination at 600 °C for 2 h under Ar. As the anode materials for lithium-ion batteries, the Fe₃O₄/carbon composite with 55.24 wt% Fe₃O₄ exhibited superior electrochemical performances, such as high reversible lithium storage capacity (834 mA h g⁻¹ at 1 C after 60 cycles, 1 C = 924 mA g⁻¹), high Coulombic efficiency (100%), excellent cycling stability, and superior rate capability (588 mA h g⁻¹ at 5 C and 382 mA h g⁻¹ at 10 C). These excellent electrochemical performances could be attributed to the robust porous carbon matrix with a partially graphitized structure for embedding a mass of small Fe₃O₄ nanocrystals, which not only provided excellent electronic conductivity, short transportation length for both lithium ions and electrons, and enough elastic buffer space to accommodate volume changes upon lithium insertion/extraction, but also could effectively avoid agglomeration of the Fe₃O₄ nanocrystals and maintain the structural integrity of the electrode during the charge–discharge process. It is believed that the Fe₃O₄/carbon composite synthesized by the current method is a promising anode material for high energy and power density lithium-ion batteries.