奈米粒子修飾之硫化鉬可以有效的改善其鋰離子電池的電化學質。在此結構中，奈米粒子扮演一個間隔者來避免相鄰的硫化鉬薄片相互重疊，使其可以和含有鋰離子的電解液接觸。在本研究中，開發出一個簡單的方法來合成Ge/MoS2複合物。Ge/MoS2複合物在0.2 A/g的電流密度下循環五十圈後，展現很優越的電容量1362 mA h/g。Ge/MoS2複合物在較高的電流密度下(5和7 A/g)循環一百圈， 依舊表現出高度可逆且穩定的電容量。其平均電容量分別為790 (5 A/g)和594 (7 A/g) mA h/g。在此，鍺奈米粒子不僅扮演一個重要的角色來穩定結構，也有效地提升Ge/MoS2複合物在高電流(>1 A/g)的充放電能力。對於更進一步的應用，我們使用Ge/MoS2陽極和Li(MnCoNi)O2陰極來組成鈕扣型的全電池(CR2032)，並用來驅動LED燈。

Nanoparticle-decorated MoS2 can effectively improve the electrochemical performance of lithium-ion battery. Among this structure, nanoparticles can act as a spacer to prevent the restack of adjacent MoS2 nanosheets and make them accessible to the electrolyte, which is a source of Li-ions. In this study, a facile synthesis of Ge/MoS2 composites has been developed. Ge/MoS2 composites exhibit the superior performance of 1362 mA h/g with the current density at 0.2 A/g after 50 cycles. Highly reversible and stable specific capacity of Ge/MoS2 composites at high rate (5 and 7 A/g) can be achieved for 100 cycles. The average specific capacity at 5 and 7 A/g is approximately 790 and 594 mA h/g, respectively. Herein, Ge nanoparticles not only play an important role to stabilize the structure but also to effectively enhance the high rate capability (>1 A/g) of Ge/MoS2 composites. For further application, coin-typed full-cell (CR2032) was assembled with a Ge/MoS2 anode and a Li(MnCoNi)O2 cathode to power the light-emitting diode (LED) array.

Table of Contents
中文摘要 I
Abstract II
Table of Contents III
List of Figures IV
Chapter 1. Introduction 1
1.1 Development of Lithium ion batteries 1
1.2 Development of transition-metal dichalocogenides anode for LIB 2
1.3 Development of Li-alloying anode for LIB 6
Chapter 2. Experimental Section 9
2.1 Chemicals 9
2.2 Synthesis of MoS2 9
2.3 Synthesis of Ge nanoparticles 9
2.4 Synthesis of Ge/MoS2 composites 10
2.5 Lithium ion battery assembly 10
2.6 Electrochemical characterization 11
2.7 Characterization 11
Chapter 3. Result and discussion 12
3.1 Material characterization 12
3.1.1 Characterization of MoS2 12
3.1.2 Characterization of Ge nanoparticles 14
3.1.3 Characterization of Ge/MoS2 composites before annealing 15
3.1.4 Characterization of Ge/MoS2 composites after annealing 17
3.2 Electrochemical performance 19
3.3 Conclusion 29
Reference 30

List of Figures
Figure 1.1 Schematic illustration and the operation principles of rechargeable LIB 1
Figure 1.2 (a, b) TEM images of nano-TiO2-decorated MoS2 nanosheets. (b) Cycling performance with the current density at 100 mA/g and (c) rate capability of the TiO2-MoS2 hybrid at different current densities (from 50 to 1000 mA /g). 4
Figure 1.3 (a) SEM and (b) TEM images of the NDG/MoS2. (c) Cycling performance of the NDG/MoS2 anode at 0.1 A/g and (d) rate capability at various current densities. 5
Figure 1.4 (a) Schematic illustration of different anode material for LIB. (b) High specific capacity and volumetric capacity of Li-alloying elements. 6
Figure 1.5 (a) SEM and (b) TEM images of Ge/rGO/C composite. (c) Capacity of composites was cycled at 0.2 C and 1 C for ~600 cycles. (d) Cycle performance of composites at different C rate. 7
Figure 1.6 Illustration of the facile process and structure evolution of the Ge/MoS2 composites. 8
Figure 3.1.1.1 (a, b) SEM images of the MoS2. 13
Figure 3.1.1.2 (a) XRD pattern, (b, c) TEM images, (d) HRTEM image and (e) SAED pattern of the MoS2. 13
Figure 3.1.2.1 XRD pattern of the Ge nanoparticles. 14
Figure 3.1.2.2. (a) TEM image and (b) SAED pattern of the Ge nanoparticles. 14
Figure 3.1.3 (a, b) SEM images, (c, d) TEM images, (e) HRTEM image and (f) SAED pattern of the Ge/MoS2 composites before annealing. 16
Figure 3.1.4.1 (a, b) SEM images and (c, d) TEM images of the Ge/MoS2 composites. (e, f) EDS elemental mappings of Mo (red), S (green) and Ge (yellow) in the Ge/MoS2 composites. (g) HRTEM image and (h) SAED pattern of the Ge/MoS2 composites. 18
Figure 3.1.4.2 XRD patterns of the Ge/MoS2 composites before and after annealing. 18
Figure 3.2.1 (a) Cycling performance of the Ge/MoS2 composites at a rate of 0.1 A/g for the initial cycle and following cycles at a rate of 0.2 A/g. (b) Voltage profiles of the Ge/MoS2 composites at 1st, 2nd and 10th cycles. (c) Differential capacity curves of the Ge/MoS2 composites at 1st, 10th and 20th cycles. 21
Figure 3.2.2. Rate capability of the Ge/MoS2 composites from 0.1 to 15 A/g. (a) All of the discharge rates are equal to the charge rates. (b) Discharge and charge at low rates (0.1, 0.2, 0.5 and 1 A/g) are kept the same and discharge rate is fixed to 1 A/g at high charge rates (2, 3, 5, 7, 10 and 15 A/g). 23
Figure 3.2.3 Galvanostatic discharge and charge cycles between 0.01 to 3 V of the Ge/MoS2 composites. The current density at 0.1 A/g for the first cycle and followed by a rate of (a) 5 A/g and (b) 7 A/g for total 100 cycles. The inset in (a) and (b) are the discharge and charge curves at 1st, 10th and 100th cycles. 25
Figure 3.2.4 (a) Structure evolution and (b-e) EDS elemental mappings of the Ge/MoS2 composites with the current density at 7A/g after 100 cycles. 26
Figure 3.2.5 (a) Areal and volumetric capacity of coin-typed full-cell (CR2032) with a Ge/MoS2 anode and a Li(MnCoNi)O2 cathode with areal current at 0.3 A/cm2 for 30 cycles. (b) Voltage profile of coin-typed full-cell with areal current at 0.3 A/cm2 at 10th and 20th cycles. (c) Coin-typed full-cell was used to power the green LEDs (87 bulbs). 28
Figure 3.2.6 Rate capability of this study is comparable with those of previous studies about nanoparticle-decorated and graphene-based MoS2. The red star symbolizes our data, which were calculated base on the active material, from 0.2 to 15 A/g (discharge and charge rates were kept the same). 28