LiMn1-x MxO2 (M=Al, Fe, Cr and Mg; 0 < x < 0.1) 正極材料在充放電過程中之相變化

Phase Transformation of LiMnxM1-xO2 (M=Al, Fe, Cr and Mg; 0 < x < 0.1) During Charge/Discharge Cycling

李俊諺(Chun-yen 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(2009年)

摘要

利用Pechini法合成o-LiMnO2及LiMnxM1-xO2(M = Al、Mg、Cr、Fe；x = 0.05, 0.1)粉末。以XRD、 ICP、EA、FE-SEM分析合成粉末之組成、粉末碳含量、結晶構造及表面形態，以循環伏安及循環充放電分析合成粉末之正極材料特性。o-LiMnO2 之可逆比電容量為161 mAh/g，發現取代5%之Al3+、Mg2+、Fe3+，其生成粉末仍為orthorhombic相，其充放電行為與o-LiMnO2類似；而5%和10%之Cr3+取代結晶相為monoclinic相。在所有的樣品中只10%之Mg2+、5%和10%的Cr3+之粉末之充放電曲線與o-LiMnO2不同，初期循環充放電比電容量不會隨循環圈數增加而增加，有明顯改善初期電容量增加之效果。LiMn0.9Cr0.1O2之可逆比電容量達200 mAh/g。LiMn0.9Cr0.1O2 和 LiMn0.9Mg0.1O2在循環充放電下之相變化已被觀察出來。

關鍵字

相變化 ； 正極材料 ； o-LiMnO2 ； 摻雜

並列摘要

o-LiMnO2 and LiMn1-xMxO2 (M = Fe, Cr, Al, and Mg; x = 0.05, 0.1) powders were prepared via Pechini method. The crystalline structure, compositions, carbon content, morphology, cycling voltammetry, and capacity of the prepared powders were investigated with XRD, ICP-OES, EA, FE-SEM and electrochemical characterization. It was found that well-ordered o-LiMnO2 sample and exhibited a high discharge capacity about 161mAh/g. The samples prepared by 5% of Al3+, Mg2+ and Fe3+-substitution remained orthorhombic phase, and show similar electrochemical performances as o-LiMnO2, whereas 5 and 10 % Cr3+-substisuted samples crystallize into monoclinic phase. Among the prepared samples, only powders prepared with 10 % Mg2+-substisuted, 5 % and 10 % Cr3+-substisuted do not show increasing capacity during the initial cycles as the cycling performance of o-LiMnO2. LiMn0.9Cr0.1O2 shows stable reversible capacity of 200 mAh/g. The phase transformation of LiMn0.9Cr0.1O2 and LiMn0.9Mg0.1O2 upon cycling is observed.

並列關鍵字

cathode materials ； o-LiMnO2 ； doping ； phase transformation

參考文獻

17. A. R. Armstrong, N. Dupre, A. J. Paterson, C. P. Grey, and P. G. Bruce, Chem. Mater. 16 (2004) 3106.

93. A. R. Armstrong, A. J. Paterson, N. Dupre, C. P. Grey, and P. G. Bruce, Chem. Mater. 19 (2007) 1016-1023.

56. W. D. Johnston, R. R. Heikes, and D. D. Sestrich, J. Phys. Chem. Solids 7 (1958) 1-13.

20. Vanderspurt, H. Thomas, Taylor, and D. Paul, U.S. Patents 4, 190 (1980) 620.

94. S. K. Mishra and G. Ceder, Physical Review B Volume 59, (1999) Number 9.