Preparation and in-situ modification of lithium nickelate thin film electrodes by inductively coupled plasma assisted sputtering

• Main Authors: Zhuo-Cang Yang, 楊卓蒼
• Other Authors: Ku-Fong Chiu
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/8h9pu5

碩士 === 逢甲大學 === 材料科學所 === 91 === Recently, Lithium ion secondary batteries have been of great interest to us. They are used as a portable energy source, particularly for lightweight, compact 3C electronics. Because of its high capacity, stable working voltage, superior energy density, low self-discharge rate, and long cycle life, it will become the most popular type of the rechargeable battery in the future, and replace the other competitors. LiNiO2 is a potential cathode material which has high ideal capacity and is cheaper than LiCoO2 (commerciallized cathode material). In this research, lithium nickelate oxide (LiNiO2) was used as cathode material for the thin film batteries (TFBs). In the experiments, lithium nickelate (Li-Ni-O) thin films was prepared by an inductively coupled plasma (ICP) assisted sputtering technique. Since it is a low-temperature process, various substrate materials can be used. It is an advantage over traditional in-situ heat treatments, which limit the choice of substrates. By this process, in-situ modification of the film texture can be achieved. In addition, Langmuir probe method was applied to study the characteristics of the plasma with the ICP process. The deposition was carried out using a magnetron sputtering gun with a lithium nickelate (LiNiO2) target at different pressures (pure Ar). A second plasma source between the sputtering gun and substrate was introduced by using a rf powered inductive coil. The amount of the bombarding ions (ion flux) and the energy of the bombarding ion (ion energy) could be accurately controlled, which then change the properties of the film during deposition. The main process variables are deposition pressures, rf powers and bias of the substrates. ICP technique could provide higher ion flux and ion energy than traditional method. The properties of lithium nickelate thin films were studied under different bombarding situations. It has been found that different process parameters result in different film texture and crystallity, which influence the performance of the thin film cathodes. Film texture and crystallity were characterized by X-ray Diffractometer (XRD) and Transmission Electron Microscope (TEM). Charge-discharge measurements were carried out to measure the capacity of the films deposited in different conditions (in-situ heating and ICP). It was found that the capacity of the films deposited by ICP was 54μAh/cm2μm, which is close to the film treated by post-RTA, as proposed in the literature.