| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 104 === Owing to the high energy density and power capability properties, the layered lithium-rich cathode materials, Li (Li1/3-2x/3NixMn2/3-x/3)O2, have become one of potential cathode materials for lithium secondary battery. Using co-precipitation method, it is possible to effectively synthesize lithium-rich secondary particles in a perfect spherical morphology and with high packing density. By adjusting the pH value, reaction temperature, and precursor concentration, the uniformity and the size of the secondary particles can be controlled. Nevertheless, Li (Li1/3-2x/3NixMn2/3-x/3)O2 has poor structural stability. Therefore, cobalt ions are usually added to improve the structural stability and the capacity of the synthesized Li1.2Ni0.13Mn0.54Co0.13O2 cathode powder is also increased to 250 mAh/g.
During the charge-discharge process, the battery capacity of the cathode materials decays as the number of the charge cycles increases. Two approaches are adopted in this work to improve the long-term cyclability of developed Li-rich cathode materials. First, PEDOT: PSS is used to modify the surface of spherical powders to enhance the conductivity and stability, especially the capacity retention under the high-rate conditions. The other method is to dip the coated electrode of lithium rich materials in Prussian Blue dye. The surface-modified electrode material shows the ability to inhibit the reaction with the electrolyte, and thus to improve the charge-discharge cycle life.
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