全固態式鋰離子二次薄膜電池製作及其特性分析

Abstract

於我們日常生活中電子產品扮演重要角色，而現今隨著無線裝置之使用量不斷劇增，可穩定提供電源之儲能材料被視為發展重點，其中全固態薄膜電池具高能量密度與高循環壽命表現之優點，而深具取代傳統鋰離子二次電池之潛力。 本研究主要為製作與分析全固態式鋰離子二次薄膜電池，其中以射頻磁控濺鍍技術製備鋰鈷氧化物(lithium cobalt oxide; LiCoO2)陰極材料與鋰磷氧氮化物(lithium phosphorous oxynitride; LiPON)固態電解質，依序沉積於具白金電流收集器之矽基板表面，進而再以熱蒸鍍技術沉積鋰金屬陽極薄膜即可完成電池組裝。 本研究乃探討不同濺鍍環境(濺鍍功率、工作壓力與氣體比例流速)與熱處理條件(退火溫度與退火時間)對於薄膜材料之影響，並建立其最佳電化學表現。其中以粉末X光繞射儀(X-ray diffraction; XRD)鑑定樣品之晶相及其結晶度；以掃描式電子顯微鏡(scanning electron microscope; SEM)觀測樣品表面形貌與其鍍率；並以X光電子能譜(X-ray Photoelectron Spectroscopy; XPS)與同步輻射產生之X光吸收光譜(X-ray absorption; XAS)分別量測樣品之配位環境與其氧化價數；此外利用交流阻抗測試計算電解質之離子導電度，並配合充放電儀研究電極材料之電容量與循環表現。經上述鑑定發現退火後之LiCoO2薄膜為(101)與(104)晶面優選方向，而具鋰離子於其中擴散不受氧離子層阻擋之優勢，此外於75 W與5 mtorr條件下製備之LiPON薄膜具較高含量之三重鍵結氮，故其離子導電度可達1.38×10－6 S/cm。

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.