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URN etd-0818108-165537 Statistics This thesis had been viewed 4125 times. Download 1356 times. Author Mao-Sung Chen Author's Email Address firstname.lastname@example.org Department Materials Engineering Year 2007 Semester 2 Degree Master Type of Document Master's Thesis Language English Page Count 73 Title Effects of Al3+ ion substitution of LiFe1-xAlxPO4/ MCMB on the cycle properties and capacity fading mechanism Keyword capacity fading olivine structure cathode materials cathode materials olivine structure capacity fading Abstract A solution method was used to synthesize LiFePO4 and Al3+-doped LiFe1-xAlxPO4 (0 £ x £ 0.1) powders. After heat-treatment at 700oC for 8 hours under N2 flowing atmosphere, the crystalline structure, compositions, and morphology of the prepared powders were investigated with the XRD patterns performed with 01C beamline of NSRRC of Taiwan, ICP-OES, and SEM. The powder with composition of LiFe0.95Al0.05PO4 shows the best cycling performance at room temperature among the prepared samples. The effects of Al3+-doping on the cycling performance of the LiFePO4/ Li coin-type cells and LiFePO4/ MCMB were investigated. From the cycling results of LiFePO4/ Li cells and the results of GSAS refinement, it was found the reversible capacity of LiFePO4 was increased by Al3+-substitution due to the enlargements of lattice parameter. From the results of capacity retention study for the LiFe1-xAlxPO4/ MCMB stacked cells, the high resolution X-ray image observation, and soaking study, it was revealed that the cycling performance of improvement in LiFe1-xAlxPO4/ MCMB cells by Al3+-substitution was attributed to the suppression of Fe2+-dissolution into LiPF6 electrolyte. Advisor Committee Hong-Ming Lin - advisor
She-Huang Wu - advisor
Ru-Shi Liu - co-chair
Wen-Chang Chen - co-chair
Files Date of Defense 2008-07-15 Date of Submission 2008-08-21