鎂、鉀部分取代之磷酸鋰鐵正極材料的製備與特性研究

Preparation and characterization of LiFe1-xMgxPO4 (0 £ x £ 0.09) & LiFe1-xK2xPO4 (0 £ x £ 0.05) cathode materials

李俊漢(Jyun-Han Li)

指導教授 ： 吳溪煌

大同大學/工程學院/材料工程學系所/碩士(2011年)

摘要

本研究利用溶液法合成橄欖石結構之LiFePO4、Mg2+離子部分取代鐵離子之LiFe1-xMgxPO4 (0 ≤ x ≤ 0.09)及K+離子部分取代鐵離子之LiFe1-xK2xPO4 (0 ≤ x ≤ 0.05)正極粉末。以XRD、ICP-OES、EA及SEM研究合成粉末之晶體結構、成分組成、碳含量以及表面形貌。並以循環充放電測試、循環伏安分析去探討所合成粉末之電化學特性。在合成之LiFe1-xMgxPO4粉末中，以LiFe0.95Mg0.05PO4具有較高的放電電容量以及較好的充放電速率承受能力。而合成之LiFe1-xK2xPO4 (0 ≤ x ≤ 0.05)正極粉末的可逆電容量隨著K+離子取代量增加而降低，同時速率放電能力也變差。

關鍵字

鋰離子電池 ； 磷酸鋰鐵 ； 摻雜

並列摘要

In this study, the olivine-structured LiFePO4, Mg2+-substituted LiFe1-xMgxPO4 (0 ≤ x ≤ 0.09), and K+-substituted LiFe1-2xKxPO4 (0 ≤ x ≤ 0.05) powders were prepared via a solution method. The crystal structure, composition, carbon content, and morphology of the synthesized samples were investigated with XRD, ICP-OES, EA, and SEM, respectively. The electrochemical properties of synthesized samples were studied with capacity retention study and cyclic voltammetry. Among the prepared LiFe1-xMgxPO4 samples, LiFe0.95Mg0.05PO4 exhibited the best cycling performance. It demonstrated the initial discharge capacities of 148, 133, 128, 117, and 104 mAh/g at 0.1, 0.5, 1, 2, and 5C rates, respectively. Furthermore, it also showed excellent cycling stability. However, the reversible capacity of LiFe1-xK2xPO4 decreases significantly with increasing x, and the reduction in capacity becomes worse as they were cycled at higher C rates.

並列關鍵字

doping ； Lithium ion batteries ； LiFePO4

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