| Summary: | 博士 === 國立成功大學 === 化學工程學系碩博士班 === 94 === There are two main objectives of this study. The first objective is to synthesize the layered LiAl1-xCoxNi1/3Mn1/3O2 (0≦x≦1/3) cathode material designed by a computational approach. The calculated voltage curve of LiNi1/3Al1/3Mn1/3O2 compound is presented, indicating it is of great potential for a cathode material of lithium ion batteries. Unfortunately, it was found that the LiNi1/3Al1/3Mn1/3O2 compound without impurity phase could not be synthesized via a sol-gel process. To obtain a layered compound without impurity phase, partial of Al is replaced by Co in LiNi1/3Al1/3Mn1/3O2 compound in this study. Layered LiAl1/3-xCoxNi1/3Mn1/3O2 (0≦x≦1/3) compounds were synthesized via sol-gel reaction at 900oC under an oxygen stream. Single phase of the LiAl1/3-xCoxNi1/3Mn1/3O2 in 1/6≦x≦1/3 region could be prepared successfully. The discharge capacity and conductivity increased with an increase in the Co-substitution content. The enhancement of the conductivity and phase purity by the introduction of Co content shows profound influence on the performance of the LiAl1/3-xCoxNi1/3Mn1/3O2 compounds.
The second object is to develop a wireless charging process for the lithium ion battery. In this work, we developed the wireless microwave charging module to overcome the disadvantages of previous methods. The wireless microwave charging module can charge the implanted lithium ion battery in a suitable distance by tuning the power input and the implanted lithium ion battery shows excellent cycleability after 20 cycles. Although the conversion of the wireless microwave charging is only 2~5%, it can be improved by using other designs of antenna (microwave generation part) and rectify antenna (receive and conversion part).
The cycling performance of the LiNi0.45Mn0.45Co0.1O2/Li, LiMn2O4/Li, Li4Ti5O12/Li, MCMB/Li, LiFePO4/Li and LiMn2O4/Li4Ti5O12 cells and the structural stability of these electrode materials in the wireless powering process have been investigated in this work. It was found that the capacity retention of the spinel LiMn2O4 and olivine LiFePO4 cathode materials are better than that of the layered LiNi0.45Mn0.45Co0.1O2 in the wireless powering process. The structure of the spinel and olivine materials remains unchanged but the undesired cation mixing was observed in the layered LiNi0.45Mn0.45Co0.1O2.
The cycling performance and the structural stability of these various anode materials in the wireless powering process have also been investigated in this work. It was found that the capacity retention of the spinel Li4Ti5O12 is better than that of the layered MCMB (Meso-carbon Micro-bead) in the wireless powering process. The structure of the Li4Ti5O12 materials remains unchanged but the particles of the MCMB were disintegrated significantly after the cycling, indicating that the structural stability of the spinel anode is much better than that of the layered one in the wireless powering process. It is worthy to note that the same observation has been reported for the cathode materials in the wireless powering process. Consequently, the full cell of LiMn2O4/Li4Ti5O12 was demonstrated to be excellent capacity retention in the wireless powering process.
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