Electrochemical properties of iron oxides/carbon nanotubes as anode material for lithium ion batteries

• Published in: Journal of power sources 2015-01, Vol.274, p.1091-1099
• Main Authors: Zeng, Zhipeng, Zhao, Hailei, Lv, Pengpeng, Zhang, Zijia, Wang, Jie, Xia, Qing
• Format: Article
• Language: English
• Subjects: Anodes; Carbon; Chemical vapor deposition; Electrochemical impedance spectroscopy; Electrodes; Formations; Lithium; Lithium-ion batteries; Nanostructure
• ISSN: 0378-7753
• DOI: 10.1016/j.jpowsour.2014.10.181

A composited anode material with combined Fe sub(3)O sub(4)/FeO nanotube and carbon shell is synthesized by a facile hydrothermal method with subsequent CVD heat treatment. The as-prepared Fe sub(3)O sub(4)/FeO/C composite shows excellent cycle stability and rate capability as lithium ion battery anode. We study the effect of FeO on the electrochemical performances of the Fe sub(3)O sub(4)/FeO/C electrode. A capacity climbing phenomenon can be observed for the Fe sub(3)O sub(4)/FeO/C electrodes, which tends to be more evident with increasing FeO content. The "extra capacity" is correlated with the reversible formation of polymeric gel-like film on the particle surface of active materials, which is electrochemical active towards Li ions. The FeO component presents a certain extent of catalytic role in assisting the formation of the gel-like film. Transmission electron microscope (TEM) and electrochemical impedance spectroscopy (EIS) analytical technique are combined to further confirm the reversible growth of the SEI gel-like film. High temperature promotes the formation of gel-like film, while the resistance from the film decreases remarkably with temperature due to the enhanced lithium ion conductivity. The film contributes little to the whole EIS resistance of Fe sub(3)O sub(4)/FeO nanotube/carbon electrode. Tentative explanations based on the current experiments and existing literature are made to explain such unusual finding.