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URN etd-0722105-160348 Statistics This thesis had been viewed 3287 times. Download 1717 times. Author Ming-tlau Yu Author's Email Address No Public. Department Materials Engineering Year 2004 Semester 2 Degree Master Type of Document Master's Thesis Language English Page Count 111 Title The Preparation and Characterization of the Pechini Method Derived o-LiMnO2 Cathode Materials Keyword sol-gel method orthorhombic LiMnO2 lithium ion batteries lithium ion batteries orthorhombic LiMnO2 sol-gel method Abstract Orthorhombic LiMnO2 cathode powders with various Li/Mn molar ratios were prepared via a Pechini route followed by heat-treating at temperatures between 700 and 900 oC under nitrogen atmosphere. The influences of the residual carbon in the calcined precursor on the crystalline structure and the charge/discharge cycling performance of the prepared powders were studied. The effects of heat-treatment conditions on the crystalline structure and the electrochemical properties were also investigated with XRD, capacity retention study, and cyclic voltammetry. It is found that the sample prepared with starting Li/Mn ratio of 1.05 followed by calcination at 300 oC for 6 hr under air atmosphere and heat-treatment at 800 oC for 15 hr under nitrogen atmosphere shows the best cycling performance among the prepared powders. This sample shows the maximum discharge capacity of 158 mAh/g at 20th cycle and capacity loss of 3% between 20th and 80th cycles at 30 oC. From the variation of charge/discharge curves and the redox peaks on the cyclic voltammogram for each cycle, the observation of ex-situ XRD patterns of the cathodes cycled for various cycles and those charged to various potentials during the 15th cycle, it was found that o-LiMnO2 transforms into spinel-like phase as that suggested previously. It is the transformation that supresses the Jahn-Teller effect, thus the sample exhibited very low capacity loss as it was cycled between 2.5 and 4.3 V for 80 cycles. Advisor Committee She-huang Wu - advisor
Mu-Rong Yang - co-chair
Ru-shi Liu - co-chair
Yung-Jen Lin - co-chair
Files Date of Defense 2005-06-14 Date of Submission 2005-07-22