鋰離子電池碳批覆鋰鐵磷酸鹽正極材料之製備與特性分析

Preparations and Characterizations of Carbon Coated LiFePO4 Cathode Materials for Lithium-Ion Batteries

張鈞智(Chun-Chih Chang)

指導教授 ： 吳乃立

國立臺灣大學/工學院/化學工程學研究所/碩士(2006年)

https://doi.org/10.6342/NTU.2006.01005

摘要

由於鋰鐵磷酸鹽之低成本、低毒性、高工作電位、高理論電容量、以及其組成元素在地球上豐富的藏量，使得它成為一極具潛力之鋰離子電池正極材料。在本研究中，我們使用一能夠讓反應氣氛流經源材料粉體床之實驗配置來合成碳批覆鋰鐵磷酸鹽，利用這個裝置可在兩小時中合成出具良好電化學特性之鋰鐵磷酸鹽。從調整鋰鐵計量比的實驗結果，可以找到一個最適的計量比範圍，其中當鋰鐵比例為1.17時，其產物可以放出140 mAh/g的電容量。將前述的製程稍作改良之後，在最佳化的熱處理條件之下可以得到148 mAh/g的電容量，且在高溫循環壽命測試下有很好的表現(平均每圈0.026%的衰減)，改良過的製程較原本製程更有利於大量生產。之後，不同碳含量的樣品也比較了它們之間高溫循環的能力，結果顯示碳量高的樣品表現出較佳的循環壽命(在循環100圈之後相差了30%的電容量衰退)。最後，以溶膠-凝膠法在少量碳批覆之鋰鐵磷酸鹽表面鍍上一層二氧化鈦，此二氧化鈦鍍層成功地增進了在55oC高速充放電下的半電池壽命。

關鍵字

鋰離子電池 ； 正極材料 ； 鋰鐵磷酸鹽

並列摘要

Lithium iron phosphate (LiFePO4) is a potential cathode material for lithium ion batteries owing to its low cost, low toxicity, abundance on earth, high operating voltage, and high theoretical capacity. In this research, carbon coated LiFePO4 (C-LFP) was synthesized by an experimental setup of flow-through configuration within 2 h. An optimum Li/Fe ratio of 1.17 was found (capacity of 140 mAh/g), and it revealed that the electrochemical performance would greatly be influenced by different stoichiometries. A modified synthetic route was developed. At the optimized heating condition, capacity of 148 mAh/g and good cycle life (0.026% fading per cycle) were obtained. Then, the high temperature (55oC) cycling performances of C-LFP under high rate were compared between different carbon contents. The more carbon one exhibited much better performance than the less carbon one did (30% fading in difference after 100 cycles). Finally, the sol-gel coating TiO2 on C-LFP with less carbon was made to improve the cycle performance of the half cell at 55oC.

並列關鍵字

Li-Ion batteries ； cathode materials ； LiFePO4

參考文獻

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