基於電化學交流阻抗法的鋰離子電池之老化檢測

Abstract

鋰離子電池在儲能元件的領域裡展現出優異的性能，包括高電池電壓、高能量密度以及高放電功率。近幾年來鋰離子電池已被廣泛地應用在3C產品以及攜帶型智慧裝置，並且在未來有希望成為電動車的主要動力來源。鋰離子電池的廣泛應用也促使了大量研究資源的投入，希望能更進一步地了解電池內部的反應過程與儲能機制。 電化學交流阻抗法(Electrochemical Impedance Spectroscopy, EIS)是一種非破壞性檢測方法，被認為是最適合檢測封裝電池的技術。由於鋰離子電池於使用過程中會不斷地老化，造成電池的容量減少與性能衰退，因此鋰離子電池的老化是其中一項重要的研究課題。電池的內阻上升被認為是老化的特徵之一，EIS可以很好地檢測出鋰離子電池的內阻，並且透過等效電路模型之擬合，進一步區分出電池內部各反應的貢獻，透過交流阻抗頻譜之研究，我們可以將電池於不同工作環境下的老化因素與阻抗頻譜互相連結，預測在不同循環條件的電池壽命。 本論文針對多種不同型號商業化18650鋰離子電池進行測試，分別從電池性能、電化學測試與交流阻抗頻譜等三個方面探討鋰離子電池的電極材料對性能之影響。除此之外，還使用了兩種不同類型的電池分別進行循環充放電過程，以及常溫長時間儲存之實驗，探討電池的循環老化與儲存老化對於電池內阻之影響。

Lithium-ion battery has a superior performance among energy storage devices, including working voltage, energy density, and power capability. Because of these outstanding operational value, lithium-ion battery has been widely used in mobile applications and nowadays find their way gradually into the automotive applications. This wider field of usage demands a comprehensive understanding of the reaction process inside the lithium-ion battery. Therefore we have to give general explanation of the energy storage mechanism inside the lithium-ion battery. EIS is a non-destructive testing methods which is presented as a suitable technique for detecting the encapsulated cells. In addition, EIS can also display the change of cell impedance when the lithium-ion battery aged. It was shown that the impedance spectra of lithium-ion battery is significantly increasing as the number of cycles increases and the origins of these changes were outlined. By studying the impedance spectra of lithium-ion battery, a link between the rise in impedance and loss in capacity was found and a comprehensive method to predict the SOH of lithium-ion battery was given. In this study, aging examination of lithium-ion battery using different electrode materials has been shown. In the future, more and different types of lithium-ion batteries could be investigated, in order to identify and analyze similarities in their changes in behavior during the aging process. In conclusion it can be said, that good progress was made in understanding and predicting the aging behavior of lithium-ion battery modelling using EIS measurements. Nevertheless, challenging tasks are awaiting in the promising field of lithium-ion battery research.