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National Chung Hsing University Institutional Repository - NCHUIR > 工學院 > 材料科學與工程學系 > 依資料類型分類 > 碩博士論文 >  電化學合成LiCoPO4薄膜應用於鋰離子電池正極材料之研究

Please use this identifier to cite or link to this item: http://nchuir.lib.nchu.edu.tw/handle/309270000/152972

標題: 電化學合成LiCoPO4薄膜應用於鋰離子電池正極材料之研究
Electrochemical Synthesis of LiCoPO4 Thin Film for Cathode Materials in Lithium-Ion Batteries
作者: 鳳, 林 昭
Lin, Jhao-Fong
Contributors: 顏 秀 崗
Shiow-Kang Yen
材料科學與工程學系所
關鍵字: 5V 高電位正極材料LiCoPO4;橄欖石結構;薄膜鋰電池
5V high voltage cathode materials;LiCoPO4;olivine-like structure;thin film lithium-ion batteries.
日期: 2012
Issue Date: 2013-11-18 11:39:26 (UTC+8)
Publisher: 材料科學與工程學系所
摘要: 為了滿足未來對高電位大電流電池之需求,本研究原創地且成功地在不鏽鋼基材上以嶄新方法沉積及退火合成5V高電位正極材料 LiCoPO4 應用於薄膜鋰電池。剛沉積的薄膜是由結晶的Co3(PO4)2‧8H2 及非晶的Li3PO4所組成,在200至400℃退火下,去結晶水轉化成非結晶Co3PO4及結晶的Li3PO4,在450℃(或以上)退火下開始合成LiCoPO4。經由陰極極化FE-SEM,XRD,循環伏安,充放電測試,發現此正極材料具橄欖石結構之氧化電位分別為 4.8V 和 4.9 V (vs. Li/Li+),還原電位為 4.7 V (vs. Li/Li+)。退火溫度會影響LiCoPO4之純度與結晶性,最後導致其充放電性能之優劣,雜相如Co3O4與Li3PO4常會出現於鍍膜中而影響其充放電性能,透過沉積的時間沉積電位及退火溫度等的調控可大幅降低雜相之含量。本研究建議使用定電位-Pulse V1=-0.6 V, V2=0.1 V且在退火溫度 500℃ 時具有較好充放電性能。在此沉積條件下,LiCoPO4薄膜半電池在 3.5 至 5 V 之間以 50μA/cm2電流密度充放電 20 圈,第一圈放電電容量達 91.54mAh/g,第二十圈放電電容量達 38 mAh/g。顯然其電容量與LiCOPO4粒徑、結晶性及純度息息相關。
In order to satisfy the need of batteries with the high voltage and the high current, the coating of 5V high voltage LiCoPO4 on stainless steel for cathodes in thin film lithium batteries has been originally and successfully prepared by a novel method in this study. The as-deposited film was composed of crystalline Co3(PO4)2‧8H2 and amorphous Li3PO4, transformed into dehydrated amorphous Co3(PO4)2 and crystalline Li3PO4 at temperature from 200℃ to 400℃, and synthesized into LiCoPO4 at 450℃ or higher. Through cathodic polarization tests, field emission scanning electron microscopy (FE-SEM), cyclic voltammetry (CV), x-ray diffraction (XRD) analysis and charge/discharge tests, it was found that the oxidation peaks at 4.8 and 4.9 V and reduction peaks at 4.7 V resulted from the overall cell reaction for the Li extraction/insertion reaction from/in the LiCoPO4 with olivine-like structure. The impure phases such as Co3O4 and Li3PO4 were often found, and could be minimized by tuning the deposition time, the applied voltage, and the annealing temperature. The LiCoPO4 film deposited with potential-pulse at V1=-0.6 V, V2=0.1 V and annealed at 500℃, revealed the greater capacity 162 and 91 mAh/g for the first charge and discharge, respectively and 38 mAh/g for the 20th cycle discharge at 50 μA/cm2 between 3.5 and 5 V, compared with the other coating conditions. It was concluded that the capacity was related to the crystallinity and the phase purity of LiCoPO4.
Appears in Collections:[依資料類型分類] 碩博士論文

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