高温氢还原法制备纳米硅/石墨烯复合材料的结构与电化学性能

将Hummers法制备的氧化石墨烯(graphene oxide,GO)与纳米硅粉进行超声复合和高温氢还原,制备锂离子电池用纳米硅/石墨烯(Si/G)复合材料。利用扫描电镜、透射电镜、X射线衍射和Raman光谱分析,对Si/G复合材料的形貌与结构进行分析与表征,并测试其电化学性能。结果表明,通过高温氢还原,氧化石墨烯全部还原为石墨烯,无其它杂质相生成。石墨烯包覆在纳米硅颗粒表面,形成层状复合结构;与纯纳米硅粉相比,Si/G复合材料的电化学性能明显提高,在300 m A/g电流密度下,首次放电比容量为2 915.0(m A·h)/g,首次充电比容量为1 080.5(m A·h)/g,20次循环后比容量稳定在969.6(m A·h)/g,库伦效率为99.8%;而纯纳米硅粉的首次放电比容量和首次充电比容量分别为932.7和349.4(m A·h)/g,20次循环后比容量仅为6.4(m A·h)/g。

Structure and electrochemical performance of Si/graphene nanocomposites prepared by high temperature hydrogen reduction

The nano-Si/graphene composites (Si/G) were prepared through ultrasonic mixing and high temperature hydrogen reduction using graphene oxide (GO) fabricated by Hummers method and nano-Si powder as raw materials. The morphology, microstructure and electrochemical properties of the Si/G composite material were investigated by the methods of scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray Diffraction (XRD) and Raman spectra and constant current charge-discharge experiments. The results show that graphene oxide is reduced to graphene completely, and no other phases appear. The graphene coated on the surface of nano-Si particles forms a laminar composite structure. The electrochemical properties of Si/G composites are better than that of pure nano-Si powder. Si/G composite exhibits a high initial discharge capacity of 2 915.0 (mA·h)/g and an initial charge capacity of 1 080.5 (mA·h)/g at the current density of 300 mA/g. The reversible capacity is 969.6 (mA·h)/g after 20 cycles at the current density of 0.3 A/g, and the capacity retention is 99.8%. Compared to pure nano-Si powder with the initial discharge capacity of 932.7 (mA·h)/g, initial charge capacity of 349.4 (mA·h)/g and the reversible capacity of 6.4 (mA·h)/g at the current density of 0.3 A/g, the electrochemical performance of Si/G composites is improved significantly.