鋰離子電池中，碳極（負極）上的鈍化層因是決定電池性能的關鍵因素，而受到廣泛的研究與注意。因此，本論文從三方面著手，分別探討化成程序的電位範圍、熱處理、以及熱添加劑乙烯碳酸酯（vinylene carbonate；VC）對此鈍化層造成的影響。所採用的分析工具包括X光線電子光譜（ESCA）、富利葉紅外光譜（FTIR）、差分掃瞄式卡計（DSC）、核磁共振光譜（NMR）、交流阻抗頻譜及一些標準的電化學分析技術。由化成電位對鈍化層形成的影響，我們發展出一套更快速的化成程序。此外，本論文也清楚點出造成鈍化層的熱不穩定性之原因，以及VC之所以能成為好的熱添加劑，其主要的功用所在。
目前鋰離子電池工業上慣用的化成程序事實上包含了兩個部分：鈍化層的長成程序以及鋰離子嵌入（充進）碳極的程序。後者其實佔了整個化成程序大部分的時間，因此不僅是浪費作業時間也浪費能源。在此論文中，我們提出一個新的化成觀念，亦即省略鋰離子嵌入的程序，使得化成程序僅負責鈍化層之長成，而此想法可以藉由縮小化成電位範圍來達成。我們的研究結果發現，對於標準的鋰離子電池（LiCoO2/C）而言，3.7 V是最佳的化成截止電位。在此狀況下，所需的時間不但明顯的縮短到少於傳統化成程序時間的1/3倍，而且電池的性能依然維持正常的水準。這是因為在此電位下，所形成的鈍化層已經符合電池所需，因此無須再提供更多的電能去增厚鈍化層或進行之後的鋰離子嵌入程序。這些結果顯示，我們所提出的化成程序比之現今慣用者，具有絕佳的優勢。
另外，我們的研究發現，鋰離子電池中所使用的導電鹽類，對鈍化層的熱穩定性有決定性的影響。根據FTIR結果顯示，鈍化層的主要組成為乙基碳酸鹽（ethylene carbonate；EC）的還原產物，他的結構決定了整個鈍化層所呈現出來的阻抗特性。在以六氟磷酸鋰（LiPF6）為鹽類的電解質中，鈍化層的阻抗會呈現時而減小、時而增大的震盪特性，這是由於此環境下的鈍化層具有熱不穩定性，因而在高熱環境下會有交互性的破損及重新生成的現象發生；然而，在以過氯酸鋰（LiClO4）為鹽類的電解質中，鈍化層卻不會被破壞，呈現相當穩定的阻抗特性。造成這兩個系統的差異就在於所使用的鹽類不同。此外，我們也找出LiPF6系統鈍化層熱不穩定的原因－為LiPF6在高溫之下熱分解產生的高反應性產物PF5，攻擊鈍化層與之反應所致。
最後，本論文由兩方面探討熱添加劑VC在鋰離子電池中所扮演的角色：（1）能否保護電解質中各組成防止其熱分解？（2）能否使得鈍化層具有熱穩定性？根據NMR圖譜的分析，VC在高溫系統下並不能防止LiPF6產生熱分解，因此高反應性產物PF5仍會產生。然而，由鈍化層的阻抗變化及ESCA分析結果顯示，在添加VC後所產生的鈍化層具有高分子型態的組成，且其在高溫之下能抵抗PF5的攻擊，具有相當的穩定性，有別於原本由EC還原所產生的鈍化層結構。此外，我們也證明了VC的加入能抑制高阻抗性的氟化鋰（LiF）形成於碳極表面，進而降低了介面阻抗，使得高溫充放電循環大幅改進其效率。

In lithium-ion batteries, solid electrolyte interphase (SEI) formed on carbon electrodes (negative electrodes) has been studied intensively due to its crucial impact on cycling performance of the cells. This dissertation presents the effects of formation potential range, heat treatment, and the thermal additive, vinylene carbonate (VC), on the formation and stability of SEI by electron spectroscopy for chemical analysis (ESCA), fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR), AC impedance, and certain standard electrochemical techniques. A faster formation process is developed in this study. In addition, the source of thermal instability of SEI and the functions of VC are clearly identified.
The formation process presently used in the manufacture of lithium-ion batteries includes the solid electrolyte interphase (SEI) growth process and another process for lithium intercalation into carbon. The latter process is both time and energy consuming. This study proposes a new formation concept that can shorten the formation time by narrowing the potential range and bypassing the intercalation step during formation. The optimal cut-off voltage is found to be 3.7 V for industrial LiCoO2/C cells, and the formation time is markedly reduced to less than one-third of that required in the conventional formation procedure. Cycle performance is not affected significantly because the desired SEI growth is mainly completed in this potential range. These results suggest that our new formation method is superior to the conventional one.
The type of lithium salts (LiPF6 and LiClO4) was found to have a strong impact on the thermal stability of the SEI layer formed on graphite electrodes. According to FTIR spectra, the dominant species of the SEI layer is the EC reduction product. Hence, the change of the impedance of the SEI layer is determined by its structure. The oscillating phenomena of the thickness of SEI layer in the LiPF6-system can be attributed to an alternating deterioration and reformation of SEI, illustrating its inherent thermal instability. As for LiClO4 system, because it is less reactive, the build-up of the SEI layer is stable and gradual. In addition, PF5, a decomposition product of LiPF6, was identified to be a chief source of the thermal instability of SEI in the LiPF6-system.
Finally, the role of VC as a thermal additive to electrolytes in lithium ion batteries are studied in two aspects: the protection of liquid electrolyte species and the thermal stability of SEI formed from VC on graphite electrodes at elevated temperatures. The NMR spectra indicate VC can not protect LiPF6 salt from thermal decomposition. Hence, the thermally decomposed product PF5 still has the chance to attack SEI. However, the function of VC on SEI can be observed via impedance and ESCA. These results clearly show VC-induced SEI comprises polymeric species and is stable enough to resist thermal damage. It has been confirmed that VC can suppress the formation of resistive LiF, and thus reduce the interfacial resistance. These advantages leads to the improved cycling performance at elevated temperatures.

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