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URN etd-0901114-110127 Statistics This thesis had been viewed 993 times. Download 57 times. Author Chien-Liang Chen Author's Email Address No Public. Department Materials Engineering Year 2013 Semester 2 Degree Master Type of Document Master's Thesis Language English Page Count 113 Title Preparation and characterization of Cr-doped Li2MnO3 cathodes for lithium ion batteries Keyword cation substitution layer structure Li2MnO3 Pechini method Pechini method Li2MnO3 layer structure cation substitution Abstract Monoclinic Li2MnO3 cathode materials were prepared via Pechini method followed by heat treatment at temperatures between 600 and 900 oC. The effects of heat-treatment temperature and Cr substitution on the physical and the electrochemical properties of Li2MnO3 were investigated. The crystalline structure, composition, and morphology of the prepared samples were studied by XRD, ICP-OES, and FE-SEM, the average valence and of Cr in the prepared samples were estimated by XPS, and the electrochemical properties were analyzed by capacity retention study with Li2MnO3/Li coin-type cells. The reasons of capacity fade upon cycling investigated by TEM.
The results of XRD study indicated that the Li2MnO3 prepared at temperatures between 600 and 900 oC crystalize into monoclinic with space group C2/m. From the results of XPS, it can be fiund that the content of Cr6+ increases with increasing Cr substitution for Mn. Among the samples prepared at temperatures between 600 and 900 °C, 600 oC sample shows the highest initial discharge capacity. Furthermore, it is also manifested that be initial discharge capacity is lowered by Cr substitution for Mn shows poor initial discharge capacity
Advisor Committee She-huang Wu - advisor
Nae-Lih Wu - co-chair
Yung-Jen Lin - co-chair
Files Date of Defense 2014-07-30 Date of Submission 2014-09-01