溫度調控下動力鋰離子電池電解液優化之多核種核磁共振技術研究

Optimization of Electrolyte of Dynamic Lithium Ion Battery under Temperature Control using Multinuclear NMR Spectroscopy

林佑珊(Yu-San Lin)

指導教授 ： 賈緒威

中原大學/理學院/化學研究所/碩士(2015年)

https://doi.org/10.6840/CYCU.2015.00102

摘要

20 世紀 90 年代以來鋰離子電池電動車一直是科技國家研究的熱門領域之一。然而，鋰離子電池卻也是最不穩定的電子組件之一。隨著動力電池對高功率的需求，鋰離子電池的效能已有很大的進展。但是其潛在的不穩定性—電池熱爆時有所聞，也讓大眾對於動力鋰離子電池的安全性仍有疑慮，而導致鋰離子電池的應用仍無法廣泛。
電解液是鋰離子電池中極重要的組成部分。本研究以核磁共振儀及其相關技術為重點，探討 (一) 適用低溫環境下電解液組成之設計 (諸如鋰鹽種類與濃度、有機溶劑的種類及其比例)；(二) 於室溫密閉環境下電解液遇水之產物鑑定，以驗證其反應機制以及 (三) 研究三種商用電解液於變溫環境下 (30~80 °C) 的擴散行為表現，藉以瞭解鋰鹽與有機溶劑在不同溫度下的行為機制。
藉由觀察不同電解液組成在低溫下的凝聚情形以及對於核磁共振的氫譜、氟譜、磷譜及擴散係數值的分析，本研究顯示以 Diethyl Carbonate ( DEC)， Ethylene Carbonate (EC)， Propylene Carbonate (PC) 為有機溶劑而 LiClO4 為鋰鹽的電解液系統，於低溫 (例如 20 °C ) 且不凝結的電解液，則鋰鹽濃度不應低於 0.4 M ，同時鏈狀碳酸酯類之含量不應低於環狀碳酸酯類之含量。而在常溫密閉環境下，證實微量的水亦會引發與 LiPF6 的化學反應而產生HF， LiF， H/LiPO2F2， H2/Li2PO3F 等的化學物質。最後，經由變溫條件下之氫核、鋰核及磷核擴散係數實驗可獲得鋰離子在電解液中會與溶劑形成聚集的情形。且鋰鹽中陰離子的改變對電解液中氫的擴散係數值並沒有明顯的影響，而電解液較優的鋰鹽濃度位於 0.8 ~ 1.2M 之間。
經由上述結果，核磁共振儀可以提供吾人電解液在不同溫度下之微觀行為表現。

關鍵字

電解液 ； 擴散係數 ； 鋰離子電池

並列摘要

Since the 1990s, it is well-noticed that Li+ ion battery is at present in the near future one of the most important power sources. Meanwhile, Li+ ion battery does also exhibit electronic instability drawback. Accompanied with the fast growing requirement of high energy density, the battery becomes more and more volatile and dangerous. It is therefore the improvement of Li+ ion safty to prevent from thermal runaway is always a hot topic in its research.
Electrolyte is one of the most impotent parts of the Li+ ion battery. This study focuses on some of the requirements of Li+ ion batteries which involves : firstly, the low temperature electrolyte design (including ion salt type, ion salt concentration, organic solvent composition);second, the interactions between LiPF6 at sealed and room temperature conditions; last, study of three kinds commercial electrolytes diffusion behaviors at temperature between low and high temperature.
By the observation of the freezing tests at various composition made of the Diethyl Carbonate (DEC), Ethylene Carbonate (EC), Propylene Carbonate (PC) and various concentration of LiClO4 added, we conclude that if the ratio of lower conductivity component DEC is more than the higher conductivity component EC and with LiClO4 concentration greater than, say, 0.4 molarity, then this kind of electrolytes exist good low temperature character. At room temperature and sealed condition we have solid evidence that even a trace of water will interact with LiPF6 and create the products of LiF, HF, H/LiPO2F2, H2/Li2PO3F. Last, the diffusion coefficient of lithium and phosphorus obvious difference, which means that the lithium ions will be formed of Li+-solvent coordination sphere aggregation in the solvent. And the different anoion of lithium salt for the diffusion coefficient of the impact is not obvious. In the electrolytic solution for lithium salt concentration from about 0.8 to 1.2M.
Through the above results, NMR can provide electrolyte behavior in microscopic performance under different temperatures.

並列關鍵字

diffusion ； electrolyte ； lithium ion battery

參考文獻

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