PPG/SiO2/IL/LiClO4混合型離子凝膠電解質之製備及其在鋰電池上之應用研究

The Preparation of PPG/SiO2/IL/LiClO4 Hybrid Ionogel Electrolyte and Its Application on Lithium Battery

蘇佳鴻(Jia-Hong Su)

指導教授 ： 陳玉惠

中原大學/理學院/奈米科技碩士學位學程/碩士(2012年)

https://doi.org/10.6840/cycu201200822

摘要

傳統製備高分子電解質過程相當繁瑣且需使用大量有機溶劑來溶解高分子，而有機溶劑的使用會對於環境產生很大的汙染，製備完成後也需要將其有機溶劑移除；以上過程中的浪費與對環境的危害，都是固態高分子於實際應用上之一大障礙。
故本研究係以矽酸乙酯(TEOS)為前驅物與離子熔液[BMIM-ClO4]和聚丙二醇(PPG)高分子混合、並添加過氯酸鋰作為鋰離子的來源及甲酸作為催化劑，藉由溶膠-凝膠法(sol-gel method)一步驟合成出高分子/離子凝膠作為固態之複合電解質。所製備之電解質離子凝膠薄膜藉由FT-IR、TGA、DSC、X-ray、SEM等之量測探討其特性，再以CV、EIS、Galvanostatic Cycling進行其電化學與其可逆電容量之量測。
研究結果顯示，sol-gel製程簡單且快速，過程中利用水和離子熔液為溶劑增加高分子之溶解度，無使用有機溶劑之疑慮，克服環境汙染問題，且可使用各式模板製作不同形狀之電解質薄膜。本論文研究中對SiO2、離子熔液、鋰鹽之間的相互作用力關係的探討，發現其離子傳導活化能低於在離子熔液環境中之活化能，意表其離子更容易被活化，傳導更快，為此類材料高離子導電(5.88 x 10-4 S/cm)特性之主因。TGA結果顯示，PPG/SiO2/IL/LiClO4混合型離子凝膠電解質之熱穩定性達237℃，顯示此材料擁有耐高溫之性質；CV結果證實添加PPG高分子後，提高此混合型離子凝膠電解質之電流量與界面性質，並改善其電化學可逆性。另，亦發現此混合型離子凝膠電解質之材料性質 (熱穩定性、高離子傳導特性)，及電化學和界面特性，均比純離子熔液電解質和SiO2/IL/LiClO4離子凝膠電解質佳，表示其有應用於鋰電池的電解質上之潛力。
此外，以此複合電解質組成半電池進行充放電測試，結果雖然顯示電容量表現未達液態電解質之標準，但其原因非因此PPG/SiO2/IL/LiClO4混合型離子凝膠電解質之性質不佳，乃因與正極材料LiFePO4界面性質仍不理想之故。即便如此，將此複合電解質組成電池應用於市售LED太陽能-鋰電池組上，將其充放電數週後仍可以使用，顯示此PPG/SiO2/IL/LiClO4混合型離子凝膠電解質已能在室溫下使用於小型3C產品上。本研究在高分子/離子凝膠研究中，係首先發表成功將其組成半電池並加以測試電容量之研究者，未來若能進一步改良與正極材料界面之缺失，必能將此類高分子/離子凝膠應用於各式鋰電池上。

關鍵字

鋰電池 ； 離子凝膠 ； 電解質 ； 高分子

並列摘要

Most of the traditional preparation of polymer electrolytes are complicated and use organic solvent to dissolve the Polymer during the process. Besides, the solvent removing process usually causes energy loss and pollution problems, making the application of solid polymer electrolytes difficult to be pratical.
In this study, the polymer/ionogel nanocomposite electrolyte membranes were successfully prepared by the one pot synthesis via sol-gel process with tetraethylorthosilicate (TEOS) as the precursor, 1-butyl-4-methyl imidazolium perchlorate [BMIM-ClO4], an ionic liquid, as ionic conductor, poly(propylene glycol) as reinforcer, lithium perchlorate (LiClO4) as Li-ion source and formic acid as catalyst. The as-prepared membranes were free-standing, translucent, flexible, non-crystallinity, solid-like electrolytes. Their physical and chemical properties were investigated by FT-IR, TGA, DSC, X-ray and SEM measurements. In addition, the capability and electrochemical properties were measured by performing charge-discharge cycles at different charge rate and temperature.
The results showed that the one pot sol-gel process is a easier and cost effective method to prepare the polymer/ionogel nanocomposites without using organic solvents, avoiding the solvent removing problem.The highest conductivity of the polymer/ionogel nanocomposite electrolytes at room temperature was 5.88x10-4 S/cm exhibited by P5SI6C05. There is no weight loss until 237℃ from TGA study of P5SI6C05. The cyclic voltammetry measurement also showed that addition of the polymer enhanced the stability of electrochemical and interfaces properties of the nanocomposite elecatrolytes. Compared to the Ionic liquid electrolyte and ionogel electrolyte, the polymer/ionogel nanocomposite electrolyte showed better electrochemical properties and interface in the symmetric Li/ P5SI6C05/Li cells .
The investigation of the effect of interactions among SiO2, BMIM,ClO4 and LiClO4 in the polymer/ionogel nanocomposite electrolyte showed that the activation energy of ionic migration in the nanocomposite electrolyte is lower than that in the ionic liquid electrolyte, revealing that the ion transport ability in the polymer/ionogel nanocomposite electrolyte is slightly better than that in the ionic liquid electrolyte.
The capability of Li/P5SI6C05/LiFePO4 cell measured was unsatisfactory and is ascribed to the poor interface betweem the electrolyte membrane and the LiFePO4 electrode was that affected intercalation/outcalation ability of the Li+ to the cathode. Evan so, a commercial solar cell-LED was successfully assembled with the Li/P5SI6C05/LiFePO4 cell, and used the sun light to charge and discharge the cell. It is found that the cell is still functionable for more than 2 months, revealing the possiblility of application on the pocket eletronic products. As far as I understand, this is the first report of the half cell assembled by polymer/ionogel nanocomposite electrolyte with it’s lithium properties and applied to a pocket electronic device. The improvement of interface between the polymer/ionogels nanocomposite electrolyte and the electrodes of lithium battery is suggested for the future study.

並列關鍵字

Lithium battery ； ionogels ； electrolyte ； polymer

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