Synthesis and Application of Al Current Collector with a Conformal Carbon Coating
Date Issued
2011
Date
2011
Author(s)
Wu, Hsien-Chang
Abstract
Due to the alarming energy crisis emerging in recent years, the demand for high efficiency energy-saving transportation vehicles is soaring nowadays. Extra requirement to meet the environment standard is also highly desirable. One of the major progress is the development of Hybrid Electric Vehicle (HEV), which relies on a high-quality battery with capability to generate and release huge current within a very short time scale. Hence a high performance current collector is essential to the success of the battery.
In the typical electrode configuration, the layer containing the active material was supported on a metallic current collector, especially carbon material coating current collectors. Although the state of the art synthesis technologies for modification of the current collector was quite accomplish abroad such as etching method, electroplating method, carbon coating by sol-gel method and so on, the adhesion of carbon film or transition metal on the current collector was too weak to fall. The interface between the current collector and the active layer imposes additional resistance to charge transfer within the electrode. This resistance source has not received sufficient attention in the literature, presumably because it was not considered of significance for the low-power Li-ion electrode materials in the past. However, as described above, the state-of-the-art material synthesis technologies may have reduced the ionic and electronic resistances associated with the active materials to certain point that they become competitive to the other resistance sources. Thus, the significance of the electronic resistance at the active layer/current collector interface is worthy of careful re-examination.
In this thesis, Al foil with a conformal carbon coating was synthesized by chemical vapor deposition using methane gas. According to 3M tape test and XPS data, C-E-Al foil has a strong adhesion of carbon layer, and the insulating oxide layer is replaced by the carbon layer. CV and EIS data show it not only possesses a higher conductivity but also more contact area than un-treated Al foil. For example, the use of the C-coated current collector not only remarkably increases the power-delivering capability, by 3~7-fold based on different comparison criteria, of the LFPO electrode, but also greatly enhances its cycle stability under high C rate (5 C).
Subjects
Al foil
Chemical vapor deposition
Adhesion
Current collector
surafce resistance
Etched-Al foil
Type
thesis
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