- 學位論文
石墨烯/四氧化三鐵多層複合結構在高效能鋰離子電池陽極上之應用
Graphene/Fe3O4 Hierarchical Sandwich Structure as Anode for High Performance Lithium-Ion Batteries
摘要
近年來，隨著消費性電子產品的快速發展，鋰離子二次電池的需求量也越來越大。雖然鋰電池的研究已經持續了超過40年，但鋰電池仍然存在著一些問題，其中最大的問題在於電池的可靠度以及電池容量。目前，各界的研究團隊們主要專注於開發更高容量、循環壽命更長以及更安全、穩定的材料。 本研究中，使用石墨烯/四氧化三鐵多層複合結構來做為鋰電池的負極。由於四氧化三鐵擁有許多良好的特性，例如高比容量、價格低廉、含量豐富、無毒、安全性高以及對環境無害等特性，所以此結構可望用來改良目前商業化電池所使用的石墨負極。本研究使用熱分解法來合成四氧化三鐵奈米顆粒，並進一步利用TEM、XRD及FT-IR等技術來分析所合成的奈米顆粒。接著，將四氧化三鐵奈米顆粒與石墨烯混合，製作成多層複合結構，最後再以爐管於300℃進行熱處理。在分析的部分，利用SEM、TEM來觀察複合結構的表面形貌，並使用XRD鑑定其結構，最後再透過FT-IR的分析，來確定四氧化三鐵奈米顆粒表面的油酸是否已經由300℃熱處理而除去。此外，由四點探針的電性量測結果可知，電子確實如同預期般藉由石墨烯來傳導。 為了進一步瞭解此結構的電化學性質，我們在手套箱中將此多層複合結構進行半電池組裝，並藉由定電流量測法以0.1 C的充放電速率對所組裝完成的電池作量測。由得到的充放電曲線可知，四氧化三鐵的特徵電壓平台確實出現在此曲線中，但與已發表的文獻相比較，電容量值偏低。若能進一步調整四氧化三鐵與石墨烯的比例，將四氧化三鐵層的厚度降低，可望改善此現象，並得到較好的電池特性。
並列摘要
The demand for lithium-ion batteries is ascending in the past few years due to the fast growth of a variety of consumer electronics. Although the study of rechargeable lithium batteries has been conducted for more than 40 years, some problems still remain, including reliability of electrodes and capacity of batteries. Therefore, materials with high specific capacity, long cycle life, and good safety are still widely investigated now. In this study, graphene/Fe3O4 sandwich structure was introduced as the anode of lithium-ion batteries and it has the potential to replace graphite, which is used as the anode in commercial lithium-ion batteries, due to the charming features of Fe3O4, such as high specific capacity, low cost, abundant in earth, nontoxicity, good safety, and eco-friendly property. We synthesized Fe3O4 nanoparticles by thermal decomposition method. The as-prepared nanoparticles were examined and analyzed by TEM, XRD and FT-IR. The Fe3O4 nanoparticles were further mixed with CVD graphene to form graphene/Fe3O4 sandwich structure, followed by annealed at 300℃ in Ar atmosphere in a furnace tube. The morphology and phase of graphene/Fe3O4 sandwich structure were observed and investigated by SEM, TEM, and XRD. FT-IR was also used to confirm the absence of oleic acid after annealing. The results of four probe measurement show that the electrons are transported by graphene in the sandwich structure, which is the same as expectation. In order to know the electrochemical properties of graphene/Fe3O4 sandwich structure, coin-type half cells (CR2032) were assembled with the as-prepared graphene/Fe3O4 sandwich structure as the anode in an argon-filled glove box, followed by measured via galvanostatic cycling at 0.1 C rate. The characteristic voltage plateaus of Fe3O4 were appeared in the charge/discharge profiles, but the capacity of graphene/Fe3O4 sandwich structure in this work is lower than the reported data. It is expected that the performance will be further improved if the ratio of Fe3O4 nanoparticles and graphene is adjusted.
參考文獻
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