以水热法合成的包覆油酸的α-Fe2O3粒子为前驱体,在氩气下500℃煅烧1 h,得到Fe3O4/C纳米复合物.用傅里叶变换红外(FTIR)光谱,X射线衍射(XRD),扫描电镜(SEM),X射线能量散射(EDX)谱,高分辨透射电镜(HRTEM),元素分析,循环伏安(CV)和恒流充放电测试等方法对材料的结构、形貌、成分及电化学性能进行了表征.结果表明:所制备的Fe3O4/C复合物呈长约200 nm,粗约100 nm的纺锤形,表面碳层厚约1-2 nm,碳含量为1.956%(质量分数);这种复合物作为锂离子电池负极材料具有很好的循环稳定性(在0.2C(1C=928mA.g-1)循环80次后具有691.7 mAh·g-1比容量)和倍率性能(在2C循环20次后依然有520 mAh·g-1比容量).相对于未包覆的商业Fe3O4粒子,复合物显著提高的电化学性能是由于碳包覆能防止粒子聚集,提高导电性以及稳定固体电解质界面(SEI)膜.%Oleic acid-capped α-Fe2O3 nanoparticles were initially prepared as precursors by a simple hydrothermal method. Fe3O4/C nanocomposites were synthesized by annealing the precursor at 500℃ for 1 h under an Ar atmosphere. The surface organic groups and core phase structure of the samples were characterized by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD), respectively.Scanning electron microscopy (SEM) was used to observe their morphology. The existence of carbon was confirmed by elemental analysis, energy-dispersive X-ray (EDX) spectroscopy and high-resolution transmission electron microscopy (HRTEM). Cyclic voltammetry (CV) and galvanostatic discharge/charge measurements were used to evaluate the electrochemical performance of the as-prepared Fe3O4/C nanocomposites. The results showed that Fe3O4/C nanocomposites were spindles alike with a length of about 200 nm and a diameter of about 100 nm. A carbon layer of 1-2 nm in thickness was coated on the surface of the Fe3O4 nanocrystals and the carbon content was 1.956％ (mass fraction). As anode materials for lithium-ion batteries, the composite exhibited excellent cycling performance (691.7 mAh· g-1 after 80 cycles at 0.2C (1 C=928 mA·g-1)) and rate capability (520 mAh· g-1 after 20 cycles at 2C). Compared with commercial Fe3O4 particles, the remarkably improved electrochemical performance of the Fe3O4/C composites was attributed to in situ carbon coating, which prevented nanoparticle aggregation, increased electronic conductivity and stabilized the solid electrolyte interface (SEI) films.
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