- 學位論文
碳批覆鋁電流收集板之合成與應用
Synthesis and Application of Al Current Collector with a Conformal Carbon Coating
摘要
近幾年來由於能源危機訊號響起，油價迅速高漲，環境保護意識抬頭，人們對於全球空氣品質惡化以及二氧化碳排放量逐年增加所引起的溫室效應感到憂慮，因此對潔淨能源與無污染環境的需求遽增。發展混合式電動車(Hybrid Electric Vehicle；簡稱HEV)或純電動車蔚為趨勢.油電混合車用電池最重要的是電池要能夠提供瞬間大電流充電和放電的能力。大電流放電除了可透過電池設計與正負極材料選用,正負極的導電基板，或俗稱收集板(current collector)，也是關鍵材料之一。 傳統電極技術製造方法是將活性物質之漿料添加黏著劑(binder)，再將漿料披覆在電流收集板上經乾燥而得，其中碳材被廣泛地使用於電化學儲能元件的電極製備。最近五年，國外對鋁箔電流收集板表面技術改良方面己獲致相當成就，例如將鋁箔經過傳統蝕刻方式提高鋁箔表面積再塗佈一層碳材當活性物質，或是利用合金、電鍍方式在直流收集板鍍一層過渡金屬。這些方法所得到的碳披覆鋁或過渡金屬披覆鋁，往往因為基材和活性物的緊貼度不夠，在長期充放電時造成活性物質從基板上剝落，進而造成電池壽命減少問題。近期文獻顯示，電極中高電阻抗經常發生在披覆層與收集板間的介面；在應用於電動車高功率充放電的條件下，不僅造成不可逆的能量損耗，並限制最大輸出功率。為了克服此一問題，近年來研發趨勢是在收集板上先披覆上一層黏著性高、且高導電性的碳膜。 本論文中，利用化學氣相沉積法合成碳膜批覆鋁直流板，經由3M 膠帶測試和XPS分析得知，此碳膜不但具有很強的貼合性，且鋁箔上表面具有連續氧化層將被碳層所取代，經由CV和EIS證實，此碳覆鋁直流收集板之導電性及接觸面積均大於鋁箔，因此將此收集板應用於超高電容器及鋰離子二次電池，以提升整體的能量及功率密度，舉例來說，使用碳批覆鋁直流收集板可提升鋰鐵磷電極 3~7倍的電容量(在1~10 C充放電速度下)比起未表面處理的鋁箔且在高速充放電下(5 C)，大大提升電性使用的壽命。
並列摘要
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).
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