石墨烯桥联碳-聚乙二醇包覆的Si纳米颗粒Li离子电池复合负极材料

Si是一种很有前途的Li离子电池负极材料。为解决其巨大体积形变导致的容量衰退快、循环寿命短等问题,采用简单的搅拌和热还原,利用聚乙二醇衍生的薄碳修饰Si纳米颗粒(C-PEG@Si NPs),并通过石墨烯的桥联来制备具有多级包覆结构的石墨烯桥联C-PEG包覆的Si纳米颗粒(graphene@C-PEG@Si NPs)复合材料。利用SEM、 TEM、 X射线衍射、恒流充放电测试等一系列表征测试方法对材料结构、物相和电化学性能进行分析。C-PEG与石墨烯涂层可有效地减小Li离子储存过程中Si对电解质的暴露面积并缓解其体积膨胀。研究结果表明,相比纯Si, graphene@C-PEG@Si NPs复合材料表现出优异的电化学性能,在210 mA/g的电流密度下,经过100次循环可逆比容量仍高达1 032 mA·h/g,电极在4 200 mA/g的大电流密度下循环100次,其比容量仍保持在430 mA·h/g以上。

Graphene bridged carbon-polyethylene glycol-coated Si nanoparticle as anode material for lithium ion battery

Si is a promising anode material for use in lithium-ion batteries. To solve the problems of rapid capacity decay and short cycle life caused by its huge volume expansion, a simple agitation and thermal reduction method to modify Si nanoparticles with polyethylene glycol-derived thin carbon (C-PEG@Si NPs) was used, and hierarchical graphene@C-PEG@Si NPs composites by bridge of graphene were prepared. A series of characterization test methods including SEM, TEM, X-ray diffraction and constant charge-discharge test were used to investigate the structure, morphology and electrochemical properties of graphene@C-PEG@Si NPs composites. The thin carbon from PEG and graphene wrapping was used to block electrolyte contact and buffer volume changes, respectively. The results show that compared to pure Si, the graphene@C-PEG@Si composites exhibit outstanding electrochemical performance with the reversible specific capacity of 1 032 mAh/g after 100 cycles at a current density of 210 mA/g, and a capacity higher than 430 mAh/g at a current density of 4 200 mA/g after 100 cycles.