锂离子电池负极材料Si@C/SiO_x的制备及其电化学性能

Preparation and Electrochemical Performance of Si@C/SiO_x as Anode Material for Lithium-ion Batteries

硅理论比容量高,放电平台低,是商业化锂离子电池石墨负极的替代材料之一,但是其充放电循环中体积变化大,容量衰减迅速,制约了其商业化使用。本研究通过一步法制备了具有核壳结构的硅@碳/硅氧化物(Si@C/SiO_x),将其作为锂离子电池负极材料。采用SEM、TEM、XRD、XPS等手段对所制备材料的微观形貌、结构以及组分进行了分析,并对其进行了相关的电化学测试。结果表明,Si@C/SiO_x核壳材料比Si@C核壳材料具备更优良的电化学性能。在200 mA/g电流密度下,循环45次后,Si@C的容量保持率为60.2%;而当C/SiO_x作为Si核外壳时,200 mA/g电流密度下,循环45次后,Si@C/SiO_x比容量值为787.2 mAh/g,容量保持率提高到87.3%。这主要是由于C与SiO_x复合后,外壳的机械强度大于碳壳,能够较好地缓冲Si体积膨胀产生的巨大应力,从而保证结构的完整性,提高了硅基负极材料的商业化应用的可能性。

Silicon is one of candidates for graphite anode on account of its high theoretical specific capacity and low discharge plateau. But, the severe decay caused by huge volume change during the process of charge/discharge hinders the realization of Si commercial use in lithium-ion batteries（LIBs）. A new material named Si@C/SiOx nanocomposite with core-shell structure was prepared via a facile one-step method and used as anode material for LIBs. The micromorphology, structure and electrochemical performance of Si@C/SiOx nanomaterial were investigated by SEM, TEM, XRD, and XPS measurements. It is found that the electrochemical performance of Si@C/SiOx is better than Si@C core-shell nanomaterial. After 45 cycles at current density of 200 mA/g, the capacity retentions of Si@C electrode and Si@C/SiOx electrode are 60.2% and 87.3%, respectively, and the reversible capacity of Si@C/SiOx electrode remains 787.2 m Ah/g. The electrochemical performance improvement of Si@C/SiOx electrode is ascribed to the combination of carbon and SiOx, which maintains the integrity of electrode structure through buffering the big pressure more effectively. And it improves the possibility of commercial use for Si anodes.