Studies on Sputter-deposited Lithium Manganese Oxide as Cathode Electrodes for Flexible Thin Film Lithium Batteries

• Main Authors: Wang Chien Yu, 王堅宇
• Other Authors: Hwang Bing Joe
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/38620424988259853226

碩士 === 國立臺灣科技大學 === 材料科技研究所 === 92 === The main objective of the present study is to investigate the LiMn2O4 cathode films deposited on the silicon substrate and Aluminum foil by means of RF-sputtering. The structural and surface morphology of the deposited films at various annealing temperatures were analyzed by employing XRD and SEM techniques. The LiMn2O4 cathode films were tested their charge - discharge characteristics and analyzed. The LiMn2O4 films were also deposited on plastic Kapton substrate to fabricate a flexible Li-ion micro-battery. The LiMn2O4 films were deposited on Si and Al foil by changing the deposition conditions such as working pressure, sputtering power, substrate temperature in order to obtain high quality and homogeneous films. The structural and surface morphology of the deposited films were analyzed by means of X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). It was found that the best deposition conditions to yield high quality films, from the film properties, at room temperature are: working pressure is 1.2×10-2 torr, sputtering power is 70 W and deposition time is 15 hrs. The crystallinity of the LiMn2O4 film was found for an annealing temperature at 700 0C. The cycle test was performed and it was found that the specific capacity of the film increases with the increase of the annealing temperature. It suggests that the crystallinity of the film increases with an increase in annealing temperature. In order to bring down the annealing temperature to lower than that of kapton melting temperature, we have deposited an oxide layer of ITO or SnO2, between the contacts and active material. It was found that the diffraction peak (111) would appear even without heat treatment. The diffraction peaks (111), (311), (400) are obvious, when the film was annealed at 200 0C. This means that the crystallized LiMn2O4 cathode films can be produced at lower temperature. Our interest is to deposit LiMn2O4 film on a plastic Kapton substrate to make a Li-ion micro-battery more flexible. In this direction, we have designed and fabricated variety of geometry of cells using the Kapton substrate. However, the charge and discharge characteristics of the tested cells are not as good as films deposited on Al foil. In order to fabricate a flexible Li-ion micro-battery, we need to improve our design to avoid moisture or air leak and reduce the internal impedance of the battery.