Abstract:

A kind of mesophase pitch-based microspheres (MPMB-et) with perfect spherical shape and narrow particle size distribution were prepared by emulsion-polymerization method from petroleum-based isotropic pitch. After pre-oxidation and carbonization, the mesocarbon microbeads (MCMB-et) were obtained. The properties of MCMB-et were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and other analytical methods. Subsequently, the electrochemical performance of microspheres as the anode material for lithium-ion battery was tested. Results showed that MCMB-et had a large specific surface area (13.35m²/g), wide interlayer spacing (0.352nm) and moderate structural disorder degree (the orientation of carbon layers with the MCMB-et were distorted and irregular), which promoted the intercalation and extraction rate of lithium ions between the graphite-like flakes and active sites. Compared with the MCMBs prepared by the direct thermal polycondensation method (MCMB-t) and the direct emulsification method (MCMB-e), the MCMB-et prepared by the polymerization-emulsification method had obvious advantages in terms of cycle performance and rate performance. MCMB-et could still deliver a reversible capacity of 325.3mAh/g at a current density of 500mA/g for 100 cycles and maintain a specific capacity of 240.0mAh/g at a high current density of 2A/g.

Key words: petroleum, emulsion-polymerization method, mesocarbon microbeads, microstructure, electrochemistry, lithium-ion battery

摘要：

以石油基各向同性沥青为原料，采用乳化-聚合法制备出一种球形规整、粒径分布较窄的中间相沥青基微球（MPMB-et）。经过预氧化、炭化得到中间相炭微球熟球（MCMB-et），采用扫描电镜（SEM）、高分辨透射电镜（HRTEM）、X射线衍射（XRD）和Raman光谱等分析手段表征了MCMB-et的外部形貌和微观结构，并对微球的储锂性能进行测试，结果表明：MCMB-et具有较大的比表面积（13.35m²/g）、较宽的层间距（0.352nm）和一定的结构无序度（内部类石墨片层堆积结构排列无序），加快了锂离子在类石墨片层间及活性位点的嵌入和脱出。与直接热缩聚法（MCMB-t）和直接乳化法（MCMB-e）制备的微球相比，MCMB-et在循环性能和倍率性能方面均具有明显的优势，MCMB-et在500mA/g的电流密度下循环100圈仍能保持325.3mAh/g的比容量，并在2A/g的高电流密度下仍能保持240.0mAh/g的比容量。

关键词: 石油, 乳化-聚合法, 中间相炭微球, 显微结构, 电化学, 锂离子电池