LiMnxFe1-xPO4 (0 < x < 0.5)正極材料之合成與特性研究

Preparation and characterization of LiMnxFe1-xPO4 (0 < x < 0.5) cathode materials

吳岳倫(Yue-Lun Wu)

指導教授 ： 吳溪煌

大同大學/工程學院/材料工程學系所/碩士(2009年)

摘要

本研究利用溶液法合成橄欖石結構之LiFePO4，以及Mn2+離子取代之LiMnxFe1-xPO4 (0 ≤ x ≤ 0.5)正極粉末。以XRD, ICP-OES, PSA, EA, 及SEM研究晶體結構、成分組成、平均粒徑、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化學特性。比起Mn2+離子取代之LiMnxFe1-xPO4 ，未經取代的LiFePO4 具有較高的可逆電容量還有較好的充放電速率承受能力。雖然Mn2+離子的取代可能會改善Fe3+/Fe2+ 氧化還原反應的可逆性，但也使得Li+ 離子的擴散係數減小。

關鍵字

橄欖石結構 ； LiFePO4 ； Mn2+離子取代

並列摘要

In this study, the olivine structure LiFePO4 and Mn2+-substituted LiMnxFe1-xPO4 (0 ≤ x ≤ 0.5) powders were prepared which by a solution method. The crystalline structures, compound composition, mean particle size, carbon content and morphology of the synthesized samples were investigated with XRD, ICP-OES, PSA, EA, and SEM. The electrochemical properties of synthesized samples were studied by capacity retention study and cyclic voltammetry. The un-substituted LiFePO4 shows higher reversible capacity and better rate capability than Mn2+-substituted samples, though Mn2+-substitution may improve the reversibility of the Fe3+/Fe2+ redox reaction. It may be caused by the decrease in diffusion coefficient of Li+ ions by Mn2+-substitution.

並列關鍵字

Mn2+-substituted ； Olivine structure ； LiFePO4

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