在這篇研究中,我們以1,1-二氟乙烯和六氟丙烯共聚合體為高分子主體,以不同的製備方式來製備高分子電解質.以TGA和DSC來探討其熱性質,XRD探討其微觀結構,SEM來研究其孔洞大小及孔洞體積,以及impedance analyzer來研究在電化學性質方面的表現.
從TGA結果來看,塑化劑或silica的加入都會使其熱裂解溫度有下降的趨勢,大約降低2-6oC.同時,在DSC的結果中,也會降低其熔融溫度和ΔH大約2-3J/g. 改變溶劑或非溶劑的種類並不會影響其熱穩定性.在XRD的結果中,塑化劑和silica的加入會引起其結晶峰有寬化的效應.在薄膜吸收液態電解液之後,寬化效應更為明顯.溶劑和非溶劑之效應要在液態電解液存在時才會比較明顯.
在SEM和電化學的結果中,塑化劑的加入和萃取有助於孔洞的形成,但是其影響要在silica加入後才會較明顯.塑化劑的存在也可幫助增加其導電度,大約高1-2orders,同時其導電度也超過10-3 S/cm.silica的加入也有助於吸收液態電解液,其吸收的幅度超過100 wt%,同時其導電度也超過10-3 S/cm,在塑化劑的存在下. 對於溶劑的影響,使用正丙醇當作非溶劑其薄膜可以吸收超過100wt%的液態電解液,導電度也超過10-3 S/cm.使用環己烷當作非溶劑其薄膜卻有最小的孔洞,較低的孔洞體積和導電度. 在溶劑的效應上,使用MEK當作溶劑,其薄膜有較低的孔洞體積和導電度.而使用丙酮當作溶劑的薄膜有較高的孔洞體積和導電度由於它的低沸點的性質.

Abstract
In this study, we discuss the properties of gel polymer electrolytes based on poly( vinylidene fluoride-co-hexafluoropropylene ) (PVdF-HFP) with different preparing methods. Thermal properties by TGA and DSC, microstructure by XRD, pore size and porosity of the films by SEM, and electrochemistry by impedance analyzer and charging/discharging systems were investigated.
From the TGA results, the addition of plasticizer or silica makes the decomposition temperature (Td) lowering about 2-6oC. At the same time, in DSC results, it lowers the melting temperature (Tm) about 16-20oC and crystallinity (ΔH) about 2-3 J/g. Changing the solvent or non-solvent does not affect Tm and ΔH much. In X-ray results, the addition of plasticizer or silica shows peak-broadening effect. After the films absorbing electrolytic solution, the peak-broadening effect is obvious. The solvent or non-solvent effects are more obvious due to the presence of the electrolytic solution.
In SEM and conductivity results, the addition and extraction of the plasticizer helps to the pore formation, but the influence is limited. The effect is strengthened as the silica adds. The existence of plasticizer helps to increase the conductivity. It has one or two order of magnitude higher than other films, exceeding 10-3 S/cm. The silica helps the film to absorb electrolytic solution over 100 wt% and increases the conductivity to exceed 10-3 S/cm in the presence of plasticizer. In non-solvent effect, the films using propanol or octanol as a non-solvent have higher pore size and porosity. At the same time, they absorb electrolytic solution over 100 wt% and have the conductivity about 10-3 S/cm. The films using cyclohexane as a non-solvent have the smallest pore size, porosity, and conductivity. In solvent effect, the films using MEK as a solvent have the smallest porosity and conductivity. The films using acetone as a solvent have higher porosity and conductivity because of its low boiling temperature.

Table of Contents
Abstract i

Table of Contents ii

List of Figures iv

List of Tables viii

Chapter 1 Introduction 1

1.1 Development of lithium-ion secondary batteries 1
1.2 Development of polymer electrolytes 3
1.3 Material choices of polymer electrolytes 4
1.4 Objectives of research 7

Chapter 2 Literature Review 9

2.1 Development of PVdF-HFP copolymer 9
2.2 Preparation methods of polymer electrolytes 18
2.3 Effects of polymer electrolyte on battery 19

Chapter 3 Experimental Procedures 23

3.1 Materials 23
3.1-2 Solvent properties 24
3.2 Instruments 24
3.3 Experimental procedures 24
3.3-1 Sample preparations 24
3.3-2 Instrumental analysis 24

Chapter 4 Results 35

4.1 TGA analysis 35
4.2 DSC analysis 38
4.3 X-ray analysis 46
4.4 SEM/SEI analysis 60
4.5 Conductivity analysis 69

Chapter 5 Discussion 74

5.1 Plasticizer effect 74
5.2 Silica effect 75
5.3 Solvent effect 76
5.4 Non-solvent effect 77

Chapter 6 Conclusions 78

References 79


List of Figures
Fig 1.1-1 Lithium and lithium-ion secondary batteries charging/discharging prinpicle 2

Fig 1.3-1 The cation conduction in polymer matrix 5

Fig 2.1-1 SEM microstructures of two types of films 10

Fig 2.1-2 SEM pictures of PVdF-301F (homopolymer) membranes 14

Fig 2.1-3 Conductivities of PVdF-HFP/plasticizer/SiO2 (30/50/20 w/w/w) polymer films soaked with the electrolyte of 1 M LiPF6/EC/DMC/DEC
16

Fig 2.1-4 Pore size distributions obtained by nitrogen adsorption/desorption of PVdF-HFP films 17

Fig 2.1-5 Cycling performance of LiCoO2/Li cells employing PVdF-HFP membranes 17

Fig 3.3-1 The experimental flow chart for plasticization/extraction method 30

Fig 3.3-2 The experimental flow chart for phase inversion method 31

Fig 3.3-3 Film characterizations 32

Fig 3.3-4 Electrochemical analysis 33

Fig 3.3-5 The test battery model 34

Fig 4.1-1 TGA curves of A0 and DBP 35

Fig 4.1-2 TGA curves of A1, A2, and A3 films 36

Fig 4.1-3 TGA curves of A4, A5, and A6 films 36

Fig 4.1-4 TGA curves of A1 and A4 films 37

Fig 4.1-5 TGA curves of A2 and A5 films 37

Fig 4.1-6 TGA curves of A3 and A6 films 38

Fig 4.2-1 DSC curves of A1, A2, and A3 films 39

Fig 4.2-2 DSC curves of A4, A5, and A6 films 39

Fig 4.2-3 DSC curves of A1 and A4 films 40

Fig 4.2-4 DSC curves of A2 and A5 films 40

Fig 4.2-5 DSC curves of A3 and A6 films 41

Fig 4.2-6 DSC curves of B1, B2, and B3 films 42

Fig 4.2-7 DSC curves of B4, B5, and B6 films 42

Fig 4.2-8 DSC curves of B7, B8, and B9 films 43

Fig 4.2-9 DSC curves of B1, B4, and B7 films 44

Fig 4.2-10 DSC curves of B2, B5, and B8 films 45

Fig 4.2-11 DSC curves of B3, B6, and B9 films 45

Fig 4.3-1 X-ray curves of A1, A2, and A3 films 47

Fig 4.3-2 X-ray curves of A4, A5, and A6 films 47

Fig 4.3-3 X-ray curves of A1, A1’, A2, A2’, A3, and A3’ films 48

Fig 4.3-4 X-ray curves of A4, A4’, A5, A5’, A6, and A6’ films 49

Fig 4.3-5 X-ray curves of A1 and A4 films 49

Fig 4.3-6 X-ray curves of A2 and A5 films 50

Fig 4.3-7 X-ray curves of A3 and A6 films 50

Fig 4.3-8 X-ray curves of A1, A1’, A4, and A4’ films 51

Fig 4.3-9 X-ray curves of A2, A2’, A5, and A5’ films 52

Fig 4.3-10 X-ray curves of A3, A3’, A6, and A6’ films 52

Fig 4.3-11 X-ray curves of B1, B2, and B3 films 53

Fig 4.3-12 X-ray curves of B4, B5, and B6 films 53

Fig 4.3-13 X-ray curves of B7, B8, and B9 films 54

Fig 4.3-14 X-ray curves of B1, B1’, B2, B2’, B3, and B3’ films 55

Fig 4.3-15 X-ray curves of B4, B4’, B5, B5’, B6, and B6’ films 55

Fig 4.3-16 X-ray curves of B7, B7’, B8, B8’, B9, and B9’ films 56

Fig 4.3-17 X-ray curves of B1, B4, and B7 films 57

Fig 4.3-18 X-ray curves of B2, B5, and B8 films 57

Fig 4.3-19 X-ray curves of B3, B6, and B9 films 58

Fig 4.3-20 X-ray curves of B1, B1’, B4, B4’, B7, and B7’ films 59

Fig 4.3-21 X-ray curves of B2, B2’, B5, B5’, B8, and B8’ films 59

Fig 4.3-22 X-ray curves of B3, B3’, B6, B6’, B9, and B9’ films 60

Fig 4.4-1 SEI of (a) A1 film (b) A3 film (c) A4 film (d) A6 film (Surface images) 61

Fig 4.4-2 SEI of (a) A1 film (b) A3 film (c) A4 film (d) A6 film
(Cross-section images) 62

Fig 4.4-3 SEI of (a) B1 film (b) B2 film (c) B3 film 63

Fig 4.4-4 SEI of (a) B4 film (b) B5 film (c) B6 film 64

Fig 4.4-5 SEI of (a) B7 film (b) B8 film (c) B9 film 65

Fig 4.4-6 SEI of (a) B1 film (b) B4 film (c) B7 film 66

Fig 4.4-7 SEI of (a) B2 film (b) B5 film (c) B8 film 67

Fig 4.4-8 SEI of (a) B3 film (b) B6 film (c) B9 film 68

Fig 4.5-1 Impedance curve of B1’ film 73










List of Tables
Table 1.3-1 The solubility parameter of plasticizers 6

Table 3.1-1 Materials 23

Table 3.1-2 Solvents and non-solvents data 26

Table 3.2-1 Instruments 27

Table 3.3-1 Compositions of A-series films 28

Table 3.3-2 Compositions of B-series films 29

Table 4.2-1 DSC data of A-series films 38

Table 4.2-2 DSC data of B1, B2, and B3 films 41

Table 4.2-3 DSC data of B4, B5, and B6 films 42

Table 4.2-4 DSC data of B7, B8, and B9 films 43

Table 4.2-5 DSC data of B1, B4, and B7 films 44

Table 4.2-6 DSC data of B2, B5, and B8 films 44

Table 4.2-7 DSC data of B3, B6, and B9 films 45

Table 4.3-1 X-ray data of PVdF homopolymer on 2θ to diffraction peak 46

Table 4.4-1 The average pore size of B-series films 69

Table 4.5-1 Electrolyte absorbed data of A’-series films 70

Table 4.5-2 Conductivity data of A’-series films 70

Table 4.5-3 Electrolyte absorbed data of B’-series films 72

Table 4.5-4 Conductivity data of B’-series films 73

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