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  • 學位論文

鋰離子二次電池Li4Ti5O12負極材料之合成及其電化學性質之研究

Preparation, Characterization and Electrochemical Property of Li4Ti5O12 Negative Electrode Material of Lithium-ion Battery

指導教授 : 洪逸明

摘要


本研究利用水熱法製備二氧化鈦粉末,並探討不同煆燒溫度對於二氧化鈦表面型態之影響。將水熱法所製備之二氧化鈦與碳酸鋰均勻混合後,利用固相反應法於750 oC 煆燒8小時,生成Li4Ti5O12 粉末,探討不同製程條件對於Li4Ti5O12 電化學性質之影響。此外,利用二氧化鈦、碳酸鋰與不同濃度之硝酸鑭均勻混合,於750 oC 煆燒8小時,生成摻雜La 之Li4Ti5O12 粉末,並探討摻雜不同濃度鑭對於Li4Ti5O12 電化學性質之影響。將Li4Ti5O12 粉末製備成電池之負極極片,並利用分析儀器量測材料特性及其電化學性質。利用X光繞射分析 (X-ray diffraction)鑑定其結構、掃描式電子顯微鏡 (Scanning Electron Microscope)分析粉末之大小及形貌與穿透式電子顯微鏡 (Transmission Electron Microscopy)分析晶粒大小、形貌及結晶性。利用充放電儀與循環伏安法 (Cyclic Voltammetry)分析其電化學性質。 經由XRD鑑定得知已成功製備出單一相尖晶石結構之Li4Ti5O12 之粉末。於SEM圖中可發現,利用400 oC 煆燒之TiO2 及攪拌方式所合成之Li4Ti5O12 為球形結構;而利用球磨方式可製備出不規則小顆粒之Li4Ti5O12,其顆粒較小且較均一;藉由摻雜鑭則可降低Li4Ti5O12 之粒徑大小。於充放電測試其電化學性質,可發現利用400 oC 煆燒之TiO2 及攪拌方式所合成之Li4Ti5O12 於充放電速率0.1C時,電容量為141 mAh/g;於充放電速率1C時,電容量為80 mAh/g;利用400 oC 煆燒之TiO2 及球磨方式所合成之Li4Ti5O12 於充放電速率0.1C時,電容量為164 mAh/g;於速率1C時,電容量為148 mAh/g。由此可知利用400 oC 煆燒之TiO2 及球磨方式所製備之Li4Ti5O12 於高充放電速率下能維持較高之電容量;利用400 oC 煆燒之TiO2 並摻雜5 mole % La合成Li4Ti5O12之電容量為151 mAh/g 高於未摻雜La 試樣之電容量為141 mAh/g於充放電速率0.1C時,發現藉由摻雜5 mole % La 可以提升Li4Ti5O12 之電化學性質。

並列摘要


Hydrothermal method was used to prepare TiO2 powders, and the effect of different calcination temperatures on the morphology of TiO2, were investigated. In this work, TiO2 powders and Li2CO3 were mixed to prepare the Li4Ti5O12. The Li4Ti5O12 powders were calcined at 750 oC for 8 h by solid-state method, and investigate the effect of different mixing process for the electrochemical properties of the Li4Ti5O12. In addition, the different concentrations La were doped with Li4Ti5O12, and investigated the effect of different La concentrations on the electrochemical properties of the Li4Ti5O12. The crystal structure, particle size, morphology, grain size and electrochemical properties of the products were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscopy and cyclic voltammetry. The XRD patterns show the structure of Li4Ti5O12 was single phase with spinel structure. The SEM micrographs show the morphology was sphere when stirred method was used, and relatively small and irregular particle were obtained by using ball-mill method. The SEM micrographs show the particle size decreased with increasing La concentrations. The charge-discharge curves for Li4Ti5O12, which was prepared by stirred method, had the capacity of 141 and 80 mAh/g at the current density of 0.1C and 1C, respectively and while using ball-mill method for TiO2, the capacity was 164 and 148 mAh/g at the current density of 0.1C and 1C. In this work, Li4Ti5O12 prepared by ball-mill method had a high capacity at higher constant current density. Meanwhile, 5 mole% of La doped Li4Ti5O12 had the capacity of 141 mAh/g at the current density of 0.1C. The results indicated that 5 mole% of La doped Li4Ti5O12 improved the electrochemical properties of Li4Ti5O12.

並列關鍵字

Li4Ti5O12 anode material lithium-ion battery

參考文獻


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