还原氧化石墨烯(RGO)/硅复合材料的制备及用作锂离子电池负极的电化学性能

Reduced Graphene Oxide (RGO)/Silicon Network Structured Composites: Preparation and Electrochemical Performance as Anode Materials for Li-ion Batteries

利用天然鳞片石墨通过改进的Hummers法制备氧化石墨烯(GO),在碱性条件下通过超声波剥离、静电自组装、磁力搅拌和高温还原的方法合成了还原氧化石墨烯/硅(RGO/Si)复合材料。借助XRD、SEM、TEM、EDX能谱分析和比表面积分析等发现,Si颗粒均匀分布在RGO片层内。在室温下,以该复合材料作为锂离子电池负极,在不同电流密度下研究了其电化学性能。结果表明,RGO/Si复合材料(2∶1)首次循环的放电比容量为1 231 mAh/g,首次库仑效率高达90.9%,在20次循环后,可逆容量保持在452 mAh/g,库仑效率为99.2%。RGO/Si复合材料(1∶1)的RGO片层包覆Si颗粒最紧密,其复合结构最稳定,在高电流密度下容量保持率较高。

This contribution presents the preparation and electrochemical performance of a series of reduced graphene oxide(RGO)/silicon network structured composites,which differ in RGO/Si ratio and are expected to serve as anode materials for Li-ion batteries.The preparation of the composites involved a combination of several methods such as ultrasonic exfoliation,electrostatic self-assembly,magnetic stirring and high temperature reduction,within an alkaline circumstance and from the graphene oxide(GO)which had been obtained by a modified Hummers method using natural flake graphite powders.The microstructure and relevant characteristics of the prepared RGO/Si composites was characterized and analyzed by means of XRD,SEM,TEM,energy dispersive X-ray microanalysis(EDX),and specific surface area analysis.And the electrochemical performance test was conducted under room temperature and various current densities.The experimental results showed that the prepared RGO/Si composites have a network structure,in which silicon microparticles distribute uniformly in the RGO networks.Moreover,the RGO/Si composites with RGO-to-Si ratios of 2∶1 and 1∶1 displayed relatively satisfactory electrochemical performances compared with the samples with RGO-to-Si ratios of 1∶4,1∶2 and 4∶1.The RGO/Si(2∶1)composite has a specific capacity of 1 231 mAh/g and a coulomb efficiency of 90.9%for the first cycle,as well as a reversible capacity retaining above 452 mAh/g and a Coulombic efficiency of 99.2% within 20 cycles.The RGO/Si(1∶1)composite was observed to have the most compact RGO lamellar coated onto Si microparticles and the most stable network structure,so that it exhibited high capacity retention abilities at high current density.