Synthesis and Modification of Li4Ti5O12 Nanomaterials for Li ion Batteries and Na ion Batteries.
| Autor: | Sh, Bin-Cheng, 史斌呈 |
|---|---|
| Rok vydání: | 2019 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 107 At present, there are many kinds of anode materials for lithium ion batteries, and each anode material has its own advantages and disadvantages. Among them, titanium-based materials have stable electrochemical performance and high safety, which makes it gradually applied to sodium ion batteries. But its poor conductivity and low lithium ion diffusion coefficient limited its performance in lithium-ion batteries and sodium-ion battery. In this study, Li4Ti5O12 anode material was prepared by sol-gel method. It had a suitable particle size and crystallinity after calcination at 750oC. At a rate of 1C charge rate, the reversible capacity of Li4Ti5O12 was 142.5 mAh/g. As the charge-discharge rate increased to 5C charge rate, its capacity still remained 121.6 mAh/g. We successfully synthesized Li4Ti5O12 anode material with the highly stable electrochemical performance. Furthermore, graphene oxide (GO) was prepared by Hummers method and then it was reduced to reduced graphene oxide (rGO) by thermal treatment. And rGO was coated on Li4Ti5O12 anode material to improve the conductivity of Li4Ti5O12. At a rate of 5C charge rate, the reversible capacity of LTO@3.7 wt.%rGO was 146.1 mAh/g. After 300 cycles of cycling test, the capacity retention rate was 89.2%. Moreover, it remained 101.5 mAh/g at 20C charge rate. As a result, rGO successfully enhanced the conductivity of Li4Ti5O12 in electrochemical performance. This study also used hydrothermal synthesis of Li4Ti5O12 anode materials and doped Na ions to prepared Li4-xNaxTi5O12(x=0.05, 0.10, 0.15, 0.20) by adding NaOH aqueous solution for sodium ion batteries. The reversible capacity of Li4-xNaxTi5O12(x=0.1) was 80.7 mAh/g after 0.1C cycle test, and the capacity retention rate was 83.0% after 300 cycles. In order to improve its electrochemical performance, we prepared Li4Ti5O12 nanosheets by changing the hydrothermal solvent to reduce the path of sodium ion diffusion. At a rate of 0.1C, the reversible capacity of Li4Ti5O12 nanosheets were as high as 130.1 mAh/g, and the first cycle Coulomb efficiency was 64.1%. In addition, Na ions were doped into Li4Ti5O12 nanosheets by adding NaOH aqueous solution. The results of XRD analysis showed that the lattice constant was enlarged to 8.345 Å, and the thickness was about 30~50 nm. In the electrochemical analysis, the reversible capacity of Li4-xNaxTi5O12(x=0.1) nanosheets were 154.4 mAh/g at a rate of 0.1 C, and the capacity was 115.5 mAh/g after 100 cycles. Furthermore, the Li4-xNaxTi5O12(x=0.1) nanosheets exhibited a reversible capacity of 76.0 mAh/g at the high of 1C. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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