水熱法合成LiFe1-xMgxPO4/C鋰電池正極材料之組織解析與電化學特性研究

Microstructure Analysis and Electrochemical Performance of Hydrothermally Synthesized Mg-doped LiFe1-xMgxPO4/C Cathode for Lithium Ion Batteries

張家瑗(Chia-Yuan Chang)

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.2014.00262

摘要

本研究乃利用水熱合成法製備不同含量Mg2+取代Fe2+之LiFe1-XMgXPO4/C複合正極材料粉末，進行粉末之微觀組織解析及電化學性能 測試，並歸納最佳Mg2+條件。LiFe1-XMgXPO4/C材料之水熱合成溫度為170oC，再藉由XRD繞射分析此複合粉末之相組成，利用SEM觀察粉末形貌，並以TEM進行選區繞射與微區晶相觀察，藉由XPS分析此複合粉末結晶結構之鍵結能與離子之化學位移；綜合以上之分析結果，選擇其中較佳水熱 合成成分配比之粉末，塗佈於鋁箔並組裝成電池進行充放電性能與交流阻抗測試。實驗結果顯示Mg2+部分取代的Fe2+可有效提高LiFePO4/C的充放 電容量，其中又以LiFe0.9Mg0.1PO4/C之複合正極材料粉末最佳，基於此最佳條件下，再以水熱法合成 LiFe0.9Mg0.1(PO4)0.9F0.3/C之複合正極材料粉末，發現部分摻雜F-有助於再提升LiFePO4/C的電化學性能。

關鍵字

水熱法 ； 正極材料 ； 磷酸鋰鐵 ； 鎂 ； 嵌入 ； 充放電容量

並列摘要

The aim of present study is to hydrothermally synthesize various Mg2+-doped LiFe1-XMgXPO4/C composite cathode powders for lithium ion batteries. The optimal synthesized condition is obtained through the microstructure analysis and electrochemical testing results. The hydrothermal temperature for synthesizing LiFe1-XMgXPO4/C powders is 170oC. The phase composition is determined by the X-ray diffraction (XRD). The particle morphologies are observed by the secondary electron microscope (SEM). The selected area electron diffraction (SAED) pattern and crystal images are examined through the transmission electron microscope (TEM). The chemical bonding and chemical shift of ions are determined y the x-ray photoelectron spectroscopy (XPS). The powders are coated on the Al foil and then assembled as coin cells to test the charge-discharge capacity and the impedence. The results indicated that the substitution of Mg2+ can effectively inprove the charge-discharge capacity of LiFePO4/C cathode material. The optimal composition is LiFe0.9Mg0.1PO4/C composite cathode powders. In addition, the partial substitution of F- within the LiFe0.9Mg0.1(PO4)0.9F0.3/C composited powders can further increase the electrochemical performance of LiFePO4/C.

並列關鍵字

Hydrothermal method ； Cathode Material ； Lithium iron phosphate ； Magnesium ； Doping ； Charge-discharge capacity

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