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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/1790

    Title: 鋰離子電池陰極材料LiCoO2粉體尺寸與形貌對電池性能的影響;Effects of the LiCoO2 particle size and morphology on the performance of lithium-ion batteries
    Authors: 林庭安;Ting-an Lin
    Contributors: 能源工程研究所
    Keywords: 鋰離子電池;LiCoO2;球磨;奈米顆粒;尺度效應;Li-ion battery;size effect;nano powder;ball-milling;LiCoO2
    Date: 2009-06-30
    Issue Date: 2009-09-21 11:30:38 (UTC+8)
    Publisher: 國立中央大學圖書館
    Abstract: 本研究為將商用鋰離子電池陰極材料LiCoO2 (Nippon Chem.Ind.),利用恆溫濕式球磨技術進行研磨,以降低粒徑尺寸。研磨介質為丙酮溶液與0.1 mm 球形釔安定化氧化鋯,研磨腔槽維持在氮氣環境,腔體溫度維持在15 ℃,控制球磨時間與轉速,以得到不同粒徑之陰極粉體。藉由SEM 觀察,在研磨時間與轉速提升下,LiCoO2 粉體尺寸能由原本20 μm 降低至12 nm 附近,藉由粉體與鋯珠相互碰撞,產生的剪切力與衝擊力達到降低尺寸與粒徑分布集中;另外粉體 產物,外型由多角形轉變為球形,振實密度可從2.53 上升至3.31 g/cm3。 材料檢測方面,由XRD 觀察,材料隨著球磨時間與轉速的增加,繞射峰強度降低且有寬化情形發生,但並無雜相產生,這顯示LiCoO2 粉體經球磨過程後,可使尺寸降低且保持完整材料特性;在TEM 觀察下,LiCoO2 材料層狀結構之CoO2 層間距離,會因球磨的運轉能量增加而導致距離縮短,並比對XRD繞射圖分析所獲得之資訊,讓實驗觀察與理論推理能相輔相成。 電池性能檢測方面,不同粒徑之粉體中,以尺寸最小者電池性能最佳,於充放電截止電壓分別為4.3 與3 V,0.2 C-rate 的測試條件下,商用材料20 μm粉體,初始電容量為145 mAh/g,但在11 次循環充放電後,電容量下降至原來的80 %;經球磨後所得12 nm 球形粉體材料,電容量能有189 mAh/g表現,並在30 次循環充放電後,電容量僅損失16 %,且較能承受3 C-rate 大電流充放電。 在其它檢測方面,由四點探針導電度儀及比表面積分析結果發現,球磨後之LiCoO2 奈米級粉體具有高導電度與比表面積,導電度可提升至原本材料的10 倍以上,且比表面積可達37 m2/g。 Lithium rechargeable batteries are widely used in many portable devices, such as cellular phones and computers. One method to improve the power density is to use very fine spherical particles in the cathode. In this study, various sizes of LiCoO2 powders are successfully prepared by using the mechanical ball-milling method. The particle size is controlled by the rotation rate and milling time. The structure and morphology of the particles are analyzed and characterized by X-ray diffraction, scanning electron microscope, high resolution transmission electron microscope, energy dispersive spectrometer, and conductivity test. It is found that the discharge capacities of all coin cells made of the ball-milled powders are higher than that of cells made of commercial powders. Furthermore, the cycle performance of the cell using nano-sized LiCoO2 powders is also better when tested at discharge rates 0.2 to 3 C. It is concluded that the smaller size and spherical shape of particles contribute to the enhancement of reliability by increasing the surface area for intercalation site, and hence overcome the kinetic problems in high charge-discharge rate by increasing the lithium ion diffusion rate in the electrode.
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