以奈米級ZrO2為塗佈物質改良鋰離子電池LiCoO2陰極材料充放電性能研究; Zirconia-coated lithium cobalt oxide as a long-cycling cathode for lithium batteries

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Title:	以奈米級ZrO2為塗佈物質改良鋰離子電池LiCoO2陰極材料充放電性能研究;Zirconia-coated lithium cobalt oxide as a long-cycling cathode for lithium batteries
Authors:	黃俊達;Jiun-Da Huang
Contributors:	化學工程與材料工程研究所
Keywords:	表面改質;LiCoO2;ZrO2;lithium cobalt oxide;surface coating
Date:	2004-06-17
Issue Date:	2009-09-21 12:23:08 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	本論文採用ZrO2作為塗佈物質，處理由台灣康普化學公司所提供之商用LiCoO2陰極材料，以下簡稱該材料為ComA-LiCoO2。論文探討溶凝膠法(Sol-gel Method)、聚合先驅物法(Polymeric Precursor Method)及機械塗佈熱處理法(Mechano-thermal Method)等三種改質方法，將奈米級ZrO2塗佈於ComA-LiCoO2材料，藉由微細的奈米粉體，包覆於ComA-LiCoO2表面，形成一緻密ZrO2鈍化層，不僅可隔絕陰極材料與電解質液的直接接觸，減緩電容量快速衰退現象，並可穩定結構，以提高陰極材料的工作電壓。改質ComA-LiCoO2陰極材料，是藉由奈米級ZrO2粒子，於陰極材料表面形成一層緻密鈍化層。以溶凝膠法採用0.3 wt%ZrO2塗佈ComA-LiCoO2陰極材料後，在0.2C-rate充放電速率下，充放電截止電壓分別為4.40至2.75V，可得到初始電容量為172 mAh/g，循環壽命為87次循環為最佳。以聚合先驅物法將0.3wt% ZrO2塗佈ComA-LiCoO2陰極材料後，以相同的測試條件下進行測試，初始放電電容量為168 mAh/g，循環壽命可達93次循環。當採用機械塗佈熱處理法將奈米ZrO2塗佈於ComA-LiCoO2陰極材料後，所得材料之循環壽命為三者之最佳，可達110次循環。經TEM鑑定，以機械塗佈熱處理法所得ZrO2厚度最為均一，同時其BET測試值為三者之最高，另由循環伏安測試可知，經過ZrO2塗佈後材料，電壓介於4.0~4.2V間六方晶相與單斜晶相變換，有效地受到抑制，並同時提升電池之循環壽命。由上述結果，藉由ZrO2的處理，的確可在ComA-LiCoO2表面上，形成一ZrO2薄層，以減少材料在充放電時，活性物質與電解質液間之直接接觸，同時穩定材料結構，此舉不僅可延長電池使用之年限，亦可改善鋰離子電池層狀結構陰極材料無法承受更高電壓與快速充放電的問題。 A commercial sample of LiCoO2 was coated with ZrO2 by sol-gel and mechano-thermal processes. The effects of the coating method and the precursor used in the sol-gel coating process were studied. Electron microscopic images of the coated particles revealed the presence of a compact coating over the cathode particles. XRD and ESCA results suggested the formation of substitutional compounds of the composition LixZryCo1–yO2+0.5y on the surface of the cathode. Coating levels of 0.3 and 1.0 wt.% were found to be optimal in terms of cyclability for the materials coated by the sol-gel and mechano-thermal methods, respectively. At these coating levels, the R-factor values, determined from XRD data, were the lowest. The maximum improvements in cyclability registered at a 0.2 C rate were about eight-fold with the sol-gel and mechano-thermal coating methods. Cyclic voltammetric studies showed that the coating led to a suppression of the cycle-limiting phase transitions accompanying the charge-discharge processes.
Appears in Collections:	[National Central University Department of Chemical & Materials Engineering] Electronic Thesis & Dissertation

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