以水熱合成LiF-LiFePO4鋰離子電池複合正極材料之組織解析與充放電特性研究

Electrochemical and Microstructural Characteristics of Hydrothermally Synthesized LiF-coated LiFePO4 Composite Cathode Materials for Lithium Ion Batteries

鄭博維(Bo-Wei Zheng)

指導教授 ： 楊崇煒

國立虎尾科技大學/工程學院/材料科學與綠色能源工程研究所/碩士(2014年)

https://doi.org/10.6827/NFU.2014.00136

摘要

由於磷酸鋰鐵(LiFePO4)電池具有安全性高及充放電循環壽命長等優點，因此LiFePO4目前已被用於鋰離子二次電池作為正極材料。本研究乃利用水熱合成法製備LiFePO4正極材料粉末，並亦藉由水熱法合成過程中添加不同莫耳濃度之LiF，並控制在150oC、170oC以及改變合成溫度3小時、6小時等不同的水熱製程條件下，合成F-doped-LiFePO4複合正極材料粉末，藉由XRD繞射與TEM解析此複合粉末之相組成與形貌觀察，利用DTA檢測相穩定性，並亦藉由XPS分析LiF/LiFePO4複合粉末結晶結構之鍵結能與離子之化學位移；綜合以上之複合粉末分析結果，選擇其中最佳水熱合成條件，將其塗佈於鋁箔並組裝成電池以進行電性測試。實驗結果顯示LiFePO4及LiF/LiFePO4複合正極材料粉末皆可藉水熱法製程加以合成，粉末之相穩定與結晶性佳，電性測試結果顯示其充放電壓偏低，推測可能為導電石墨添加不足而使LiF/LiFePO4導電度較低之結果。

關鍵字

水熱合成法 ； LiFePO4 ； 正極材料

並列摘要

Since the LiFePO4 compound displays advantages with a high safety and high charge-discharging cycles, it has been widely used as cathode materials of the secondary lithium-ion battery. In the present study, hydrothermally synthesized LiFeO4 powders were used as the raw material, and the LiF-coated LiFeO4 composite cathode materials were also prepared by the hydrothermal synthesizing method at 150oC, 170oC, held for 3hr. and 6hr. to improve electrochemical properties of raw-LiFeO4 cathode powders under a high voltage. The phase composition, crystallinity and particle morphologies were examined by the x-ray diffraction and TEM analysis.
The phase stability was examined by the TGA analysis. The binding energy and chemical shift of crystalline LiF/LiFePO4 composite powders were analysized by the XPS. Concluded the above-mentioned results, the optimal powder conditions were selected to deposit on the Al-foil. Then the deposited Al-foils were assembled as a battery for the electrochemical tests.
Experimental results showed that the raw-LiFePO4 powders and LiF/LiFePO4 composite cathode powders were synthesized by the hydrothermal method. The LiF/LiFePO4 composite powders showed good thermal stability and good crystallinity. After the charge-discharge experiments, it was found that the LiF/LiFePO4 composite powders shows a lower capacity, which is resulted from a lower adding content of the conductive carbon black.

並列關鍵字

Hydrothermal synthesizing ； LiFePO4 ； Cathode material

參考文獻

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