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| Autor: | Guan-hong Liu, 劉冠宏 |
|---|---|
| Rok vydání: | 2015 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 103 To meet the emerging growth of power and energy storage market, new generation of lithium-ion batteries (LIBs) must meet the reqirements such as high energy density、high power、fast charge/discharge and long cycle life. The purpose of this research is to design high performance electrode active materials so as to meet those requirements. Spinel lithium titanate LTO(Li4Ti5O12)-based anode has attracted great interest in high power lithium ion batteries due to its zero-strain character during lithiation and a very flat potential plateau at about 1.55V (vs. Li/Li+), which served as a safe electrode. Due to its low conductivity (~10-13 S cm-1) 、 low lithium ion diffusivity (~10-12 cm2 s-1) and poor specific capacity, LTO suffers from poor capacity and lower power density at high charge/discharge rates. Present research proposed to incorporate transition metal oxide (TMO) into the LTO in order to mitigate these drawbacks. Because TMO have been envisaged as alternate anode materials for LIBs which has high specific capacity and could reduce a part of high conductivity transition metal irreversibly and remain as the electrical conduction enhancer. Moreover, it contributes in promoting electron transfer in the redox reaction of LTO and thus improving the rate capability of LTO. For the synthesis of the composite anode materials, Co3O4 was incorporated into LTO with three different composition, LTO:Co3O4=75:25、50:50 and 25:75 of weight percentage. Furthermore, it was found that by reducing calcination time from 12h to 6h, the capacity could be enhanced. Compared to 140.4 mAh/g in single LTO anode, the result shows that LC(75/25)-6 and LC(25/75)-6 could enhance the lithium charge capacity to about 363.5 and 682.2 mAh/g under 0.1C. The charge/discharge rate could be improved to 1C and 2C, with the capacity around 239.1 and 198.6 mAh/g for LC(75/25)-6 、 397.9 mAh/g and 312 mAh/g for LC(25/75)-6. It also performs good cycling stability, in which after 150 cycles under0.1C and 1C remain stable for LC(75/25)-6 and LC(25/75)-6. The Coulombice efficiency of capacity、rate capacity and long-term cycle is almost 100%. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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