近年來因行動裝置、電動車快速的發展，高能量密度鋰離子電池之開發是迫切需要的，其中表面積電容是個重要的指標，於啇業化鋰離子電池負極單位面積電容約為4 m Ah/cm2，而相關鋰離子負極材料的文獻中其值都低於4 m Ah/cm2，於此我們提供一個新穎電極結構可達到2.5倍的啇業化的負極單位面積電容。此結構是以數個鍺奈米線和銅奈米線製成的織布和黏著劑所搭配而成的層狀電極結構，許多活性材料可乘載在此單位面積上。藉由著不同的層數搭配，可以得到不同的單位面積電容，其電池表現如下所示: 2層的電極承載5.3 mg的鍺奈米線以1.2 mA/cm2充/放電，經過50次循環表現下可以達到約5 m Ah/cm2的表現，3層的電極承載8.5mg的鍺奈米線以1.0 mA/cm2充/放電，經過20次循環表現下可以達到10 m Ah/cm2的表現。同時我們和啇業化的鋰鎳鈷錳氧正極材料搭配成功地製作出高單位面積電容的全電池，以1.08 mA/cm2的電流充放電，經過50次循環表現下可達到6 m Ah/cm2的表現。以此結構所組成的全電池可提供較大的單位面積電容量於LED燈和風扇上的應用。

Recently, because of the emerging market for portable device and electric vehicles, the development of high energy lithium ion batteries was urgent required. In high energy lithium ion batteries development, the areal capacity is an important indicator. The areal capacity of commercial negative electrode is around 4 m Ah/cm2, that most of the negative material literature were still lower than it. Here we report the novel structure of electrode by using germanium nanowires as lithium-ion battery anode to achieve 2.5 times commercial areal-capacity. Germanium nanowires and copper nanowires were combined to manufacture germanium/copper nanowires fabrics with a layer-by-layer structure. The electrodes fabricated by using several nanowires fabrics and c-PAA-CMC to form a multi-layered structure which contain lot of active material on its unit area. By different layers of the multi-layered structure electrode, the high areal capacity are showing as followed. The 2 layers structure loading 5.3 mg Ge NWs exhibited the reversible areal capacity of ~5 m Ah/cm2 at the charge/discharge current 1.2 mA/cm2 after 50 cycles, and the 3 layers structure loading 8.5 mg Ge NWs performed the reversible areal capacity of ~10 m Ah/cm2 at the charge/discharge current 1.0 mA/cm2 after 20 cycles. Moreover, we successfully assemble the full battery by using a LiNiCoMnO2 cathode, which the areal capacity can achieve to ~6 m Ah/cm2 at the charge/discharge current 1.08 mA/cm2 after 50 cycle and the full battery can provide large capacity for uses on light-emitting-diodes (LEDs) and electric fan.

中文摘要………………………………………………………………………………I
Abstract…………………………………………………..…………………………..II
Table of Contents…………………………………………………………………...III
List of Figures……………………………………………………………………….IV
List of Table…………………………………………………………………………..V
Chapter 1. Introduction……………………………..……………………………………………1
Chapter 2.
Experiment Detail………………………...………………………………...………14
2-1 Materials…...………………………………………………………………14
2-2 Gold Nanoparticle Formation………………………..………….14
2-3 Germanium Nanowires Formation...……………………………………15
2-4 Germanium Nanowires Surface Passivation…...………………………..15
2-5 Copper nanowires formation………...…………………………………...16
2-6 c-PAA-CMC adhesive slurry formation…...…………………………….16
2-7 Ge/Cu nanowires Fabric Formation…...………………………………...16
2-8 Multi-layered Electrode Formation………………………………………17
2-9 High Areal Capacity Cathode Electrode Formation…………………….19
2-10 Battery Assembly and Electrochemical Characterization…….............19
Chapter 3.
Result and Discussion..........…………………...…………….……………………...20
Conclusion……………………………..…………………………………………….34
Chapter 4.
Reference…………………………………………………………………………….35
List of Figures
Figure 1-1. Schematic illustration of operating principle of a typical rechargeable Li-ion battery…………………………………………………………………………….2
Figure 1-2. (a) Theoretical capacity histogram of IV group elements. (b) Common Li-alloying elements, the specific capacity (mAh /g) and the volumetric capacity (mAh /cm3) is shown……………………………………………………………………...…4
Figure 1-3. (a) Schematic of morphological changes that occur in Si during electrochemical cycling. (b) Schematic of SEI formation that the SEI thickness increased gradually during charge/discharge cycling…………………………………5
Figure 1-4. The Si NWs do not pulverize or break into smaller particles after cycling
…………………………………………………………………………………………6
Figure 1-5. GeNWs grown directly on the current collector and its LIBs performance………………………………………..…………………………………..7
Figure 1-6. Alkanethiol-passivated GeNWs and its LIBs performance………………..8
Figure 1-7. The electrode loading around 2.5 mg/cm2 of active material and perform a very good first cycle coulombic efficiency of ∼90% was achieved at the charge/discharge rate of 1.25 mA/cm2………………………...........…………….…..10
Figure 1-8. The synthesis method and The LIBs performance of Si/CNT multi-layers…………………………………………………………………………….……11
Figure 1-9. The preparation and the performance of the G/Si-C material……....…….12
Figure 2-1. Schematic of the multi-layered structure without adhesive…………..…17
Figure 2-2. Schematic of the multi-layered structure with adhesive that the interface between the two nanowires fabric contains adhesive (blue) to combine the fabric together……………………………....………………………………………………18
Figure 3-1. (a) SEM images of Ge nanowires. (b) XRD analysis of Ge nanowires…20
Figure 3-2. (a) SEM images of Cu nanowires. (b) XRD analysis of Cu nanowires...…21
Figure 3-3. (a) SEM images of Ge/Cu nanowires fabric and the line-scan analysis of the nanowires fabric. (b) XRD analysis of Cu/Ge nanowires fabric before and after annealing……………………………………………………………………………..23
Figure 3-4. (a) SEM cross-section image of 1layer electrode after 25 cycle charge/discharge and the inner image is line scan of the 1 layer electrode (red line means Cu; Cyan line means Ge.) (b) SEM cross-section image of 3 layer electrode after 25 cycle charge/discharge and the inner image is line scan of the 3 layer electrode………………………………………………………………………….......24
Figure 3-5 (a) electrochemical impedance spectrum of the 1 layer electrode (b) electrochemical impedance spectrum of the 3 layer electrode ………………….….…24
Figure 3-6. Charge/discharge cycle performance of multilayers GeNWs at a rate of 0.1 C between 0.01 and 1.5 V: (filled symbol) charge; (open symbol) discharge….......….25
Figure 3-7. Voltage profiles of the GeNWs in 3 layers structure at the 0.1 C rate. Inset shows differential capacity plots of the 1st, 5th, 10th, 20thand 40th cycle, respectively…………………………………………………………………………...25
Figure 3-8 photograph of formation step to the 3 layer electrode with adhesives….....26
Figure 3-9 SEM cross-section image of 3layer electrode with adhesives (b) EDX mapping image of the 3layers electrode with the adhesives. The Green color means the Ge fabric layer position; Red color means the Cu layer position; The blue color roughly means the adhesives position………………………………………………...........….27
Figure 3-10 Comparison of the using the adhesvies and no using the adhesive.….......29
Figure 3-11. Areal capacity of Ge nanowires in multilayers with adhesives...………..29
Figure 3-12. Voltage profiles of the GeNWs in 2 layers structure at the 1.2mA/cm2 current density. ………………………..……………………………………………...30

Figure 3-13(a) The lithium foil before reaction. (b) (c) (d) (e) (f) are the image of the lithium foil of 1, 2, 3, 4 layer electrode half-cell after charged/discharged, respectively.
………………………………......…………………………………………………....31
Figure 3-14 The performance of cycle stability in the Retention verse Cycle number plot; commercial NCM go with the Ge (8.5mg) expressed in red color dot and the Li foil go with the Ge (8.1mg) expressed in blue color dot. Both of the batteries are charged/discharged at 0.1C rate.……………………………………………………...32
Figure 3-15 (a) Cycling performances of the full cell. Here the areal loading of Ge is 8.5mg/cm2 and NCM is 65mg/cm2 (b) Discharge/charge curves (at 5th 25th 50th )…….33
Figure 3-16. (a) Photograph showing a direct current fan (0.5-6V, 20-60mA) powered by an 10 mAh/cm2 full coin cell. (b) Photograph showing 48 blue LEDs (3.9V, 20mA) powered by an 10 mAh/cm2 full coin cell. (c) Photograph showing a 10 mAh/cm2 full coin cell in comparison with the 4 mAh/cm2 full coin cell by lighting 83 green LEDs (3.7V, 20mA)………………………………………………………………………....34


List of Table
Table 1-1. Areal capacity paper review of Ge, Si, and the other active material compared to commercial graphite……………………………...…………………….10

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