Fabrication and Characteristics of All Solid-state Lithium Ion Thin Film Batteries
Date Issued
2012
Date
2012
Author(s)
Chen, Chih-Jung
Abstract
Electronic devices play important roles in our daily life and the number of wireless devices is nowadays rapidly growing. Therefore, developing stable energy-storage materials is a significant task. Because of high energy density and long cycle life in all-solid-state thin film batteries, they can serve as the major candidates to replace the conventional lithium ion batteries.
The purposes of this research are to fabricate and analyze the all-solid-state lithium ion thin film batteries. First, we deposited lithium cobalt oxide (LiCoO2) cathode material and lithium phosphorus oxynitride (LiPON) solid electrolyte on Si wafer with Pt current collector by RF magnetic sputtering technique. And then we prepared lithium metal anode material by thermal evaporation to complete the fabrication of the batteries.
The different sputtering parameters (power, pressure, and gas flow rate ratio) and the different annealing conditions (temperature and time) were revealed to discuss the effects on the thin film materials, and set up the best electrochemical performance of them. The crystal structure and crystallization were characterized by X-ray diffraction (XRD). The morphology and deposition rate were analyzed by scanning electron microscope (SEM). X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) were used to observe the oxidation states and the coordination conditions. The ion conductivity of solid electrolyte was calculated by performing the electrochemical impedance spectroscopy (EIS), and the capacity and the cycle life of electrodes were measured by the capacity tester. Under these characterizations could discover that the LiCoO2 thin film was (101) and (104) preferred orientation after post-annealing. As a result, it could avoid the diffusion of lithium ions from the oxygen layer blocking. In addition, there was more triply coordinated nitrogen in the LiPON thin film under the 75 W and 5 mtorr fabricating factors. Its ionic conductivity could reach 1.38×10－6 S/cm.
Subjects
thin film battery
LiCoO2 thin film
LiPON thin film
solid electrolyte
Type
thesis
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