Substrate effect induced microstructural evolution of LiFePO4 thin films
| Autor: | Cheng-lun Chen, 陳正倫 |
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| Rok vydání: | 2009 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 97 Current, digital cameras, i-phone, notebook computers and netbooks have become the global mainstreams of electronic industries. As the weight and volume of these portable devices continuously decrease, the search for smaller, lighter, and higher power density power sources have never stopped. In order to meet these requirements, the concept of Thin Film Batteries (TFB), or all solid state micro-batteries, has therefore been of great interest. With only a few micron meters of thickness or less, thin film batteries are compatible with micron electro-mechanical devices, and can be the back-up power for SRAM, as well. This research used pure LiFePO4 thin films as the cathode materials for thin film batteries. Based on previous studies of our laboratory, that interdiffusion occurs between thin films and substrates, the substrate effects and interdiffusion between cathodes and substrates were investigated. The results indicate significant microstructural evolution of LiFePO4 thin films, and improved electrochemical performances. In this study, Carbon-free LiFePO4 thin films was deposited onto different substrates(Si3N4, Ti/Si3N4, Ag/Si3N4 and Ag/S.S.). The LiFePO4 films were annealed at 700 ℃ with Joule heating and radiation heating, respectively. X-ray diffraction (XRD) revealed that the films with radiation heating were well crystallized, free of second phases, may be textured with a (011) orientation. Comparing the properties of these thin films indicated a relationship between the microstructures and the types of substrates. The conductivity of thin films were greatly improved by the diffusion of Ag. The distribution of Ag in the LiFePO4 thin films were investigated by using a X-ray photoelectron spectroscope (XPS) and a transmission electron microscope (TEM). The thin film (LiFePO4/Ag/S.S.) showed a typical discharge voltage of LiFePO4 at 3.4 V. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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