溶液法製備橄欖石結構LiFePO4及其特性研究

The Preparation and Characterization of olivine LiFePO4 by a solution method

蕭楷模(Kai-Mo Hsiao)

指導教授 ： 吳溪煌

大同大學/工程學院/材料工程學系所/碩士(2004年)

摘要

以溶液法合成經500~800oC及4~16小時等不同條件熱處理的LiFePO4/C複合正極材料。利用AA、EA、XRD、SEM及EPMA等分析方法分析合成材料之組成、結晶構造及觀察表面形態。並以循環伏安分析和循環充放電測試探討合成粉末之電化學特性。在合成的粉末中，以經700oC熱處理12小時的LiFePO4正極粉末的電化學特性最佳，有最好之循環充放電性。在C/10及1C的充放電速率下，初電容量分別為165mAh/g及130mAh/g。在20oC和60oC的環境下，由循環伏安法測得之鋰離子在正極粉末中之擴散速率分別為4.6×10-12 cm2/s和2.0×10-11 cm2/s，而鋰離子之擴散活化能僅為14.4 kJ/mol.

關鍵字

鋰離子二次電池 ； 磷酸鋰鐵

並列摘要

Composite LiFePO4/C cathode materials were prepared with a novel solution method with various heat-treatment conditions (500 ~ 800oC and 4 ~ 16 h). The compositions, crystalline structure, and morphology of the prepared powders were investigated with AA, EA, XRD, SEM, and EPMA. The electrochemical properties as cathode material for lithium batteries were studied by cyclic voltammetric and capacity retention studies. Among the prepared composite cathode materials, the sample heat-treated at 700oC for 12 hours shows better cycling performance than those of others. It shows initial specific discharge capacities of 165 and 130 mAh/g at 30oC with C rates of C/10 and 1C, respectively. It is caused by high Li+ ion diffusivity coefficient of 4.6×10-12 cm2/s at 20oC and 2.0×10-11 cm2/s at 60oC with low activation energy of Li+ ion diffusion of 14.4 kJ/mol.

並列關鍵字

LiFePO4

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