Fe_2O_3填充碳纳米管作为锂离子电池负极材料的电化学性能

Electrochemical Performance of Carbon Nanotubes Filled with Fe_2O_3 as Anode Materials for Li-ion Batteries

通过碳纳米管与硝酸铁水热反应和随后烧结处理合成了Fe2O3填充多壁碳纳米管,透射电子显微镜(TEM)和X鄄射线衍射(XRD)分析显示,Fe2O3多数填充入碳纳米管管腔内,在碳纳米管外壁极少发现有附着物,碳纳米管中Fe2O3颗粒具有γ鄄Fe2O3结构,这与水热法制备的的纺锤状Fe2O3(α鄄Fe2O3相)明显不同。这是因为硝酸将管壁及管端腐蚀,Fe3+由于毛细管作用进入管腔。文章初步研究了Fe2O3填充多壁碳纳米管、水热法合成的纳米Fe2O3颗粒和硝酸纯化的多壁碳纳米管的电化学嵌/脱锂性能。研究发现,Fe2O3填充多壁碳纳米管具有Fe2O3的高的放电容量和碳纳米管的低放电电位特征。由于碳纳米管的限定作用,缓解了碳纳米管空腔内γ鄄Fe2O3在反复锂嵌/脱过程中的结构应变,该复合材料表现出具有良好的循环稳定性。

MWCNTs filled with Fe2O3 nanoparticles were prepared via hydrothermal reaction of purified MWCNTs in iron nitrate solution and subsequent calcination. It was found from the XRD patterns and TEM images that most of Fe2O3 nanoparticles instead of nanowires were filled inside nanotubes, and only few were found on the outside wall of the nanotubes. The Fe2O3 nanoparticles inside nanotubes was of gamma-Fe2O3 phase, different from spindle Fe2O3 nanoparticles with alpha-Fe2O3 phase obtained in hydrothermal reaction without nanotubes as the template. The purification and oxidation treatment of MWCNTs in concentrated HNO3 Solution contributed to the formation of open tips and surface functional groups, which were beneficial to the entrance of iron ion by capillarity as well as the adsorption and nucleation of iron inside nanotubes. Electrochemical lithium insertion/extraction was studied preliminarily on the obtained samples. MWCNTs filled with Fe2O3 nanoparticles were shown to have a high electrochemical reversible capacity for Li-ion insertion and extraction and to be with the advantages of both higher discharge capacity of Fe2O3 and lower discharge potential of MWCNTs. Moreover, MWCNTs can accommodate a larger structure strain of Fe2O3 nanoparticles inside nanotubes produced during Li-ion insertion and extraction, which may improve the cycle stability of the electrode to a certain extent.