Title Page
ABSTRACT
국문 초록
Contents
CHAPTER 1. INTRODUCTION 15
CHAPTER 2. METHODS 18
CHAPTER 3. RESULTS AND DISCUSSION 20
2.1. Solvent effects on the electrochemical properties 20
2.2. Observation of electrode structures 32
2.3. Overall cell resistance 36
2.4. Desolvation energy 40
2.5. SEI layer 43
CHAPTER 4. CONCLUSION 49
REFERENCES 50
SUPPLEMENTARY MATERIALS 60
Table 1. Characteristics of each electrolyte. 60
Figure 1. Schematics showing the pathways for the Na-ion transport from a cathode to anode. 17
Figure 2. SEM image of bulk Bi particles. 22
Figure 3. Changes in the voltage-capacity profiles of (a) EC/DEC, (b) DME, (c) THF, (d) DEGDME and (e) 2-MeTHF with Na–Bi half-cells measured at 1C. 23
Figure 4. Electrochemical performances of Na–Bi half-cells. a) Changes in the specific capacity measured at various C-rates for the Na–Bi half-cells with electrolytes containing... 24
Figure 5. Changes in the voltage-capacity profiles measured at various C-rates for the NaBi half-cells with an electrolyte containing EC/DEC. 25
Figure 6. Changes in the voltage-capacity profiles of ether-based electrolytes with Na–Bi half-cells measured at 10C. 26
Figure 7. Changes in the voltage-capacity profiles measured at various C-rates for the (a) DME, (b) THF, and (c) DEGDME, with Na–Bi half-cells. 28
Figure 8. Changes in the measured voltage–capacity profiles of Na–Bi half-cells in electrolytes containing EC/DEC (at 1C). 29
Figure 9. Changes in the voltage-capacity profiles measured for various cycles at 10C for the (a) DME, (b) THF, and (c) DEGDME, with Na–Bi half-cells. 31
Figure 10. SEM image of pulverized Bi nanoparticles extracted from the Na-Bi half-cell subjected to 100 cycles in an electrolyte comprising 1M NaPF6 dissolved in EC/DEC solvent. 33
Figure 11. (a–h) Surface morphologies of the Bi anodes with different ether solvents cycled at 1C for 100 cycles. Secondary-electron images recorded at (a–d) low magnification... 34
Figure 12. SEM image of Bi pristine electrode. 35
Figure 13. a) EIS results of Na–Bi(DME), Na–Bi(THF), Na–Bi(DEGDME), and Na–Bi(EC/DEC) half-cells measured at 1C after 100 cycles. b) Comparison diagram of the... 38
Figure 14. The ionic conductivity of various electrolytes. 39
Figure 15. a) Solvents number and number of solvated solvents, b) Stabilized solvated structure, c) desolvation energy for DME, THF, and DEGDME. 42
Figure 16. TEM for Na–Bi(EC/DEC) at 1C 100cycles. 45
Figure 17. TEM for a) DME, b) THF AND c) DEGDME Na–Bi half-cells at 1C 100cycles. 46
Figure 18. In-depth XPS characterization of SEI in the ether-based electrolytes after 100 cycles at 1C. The atomic concentrations of carbon, fluorine, oxygen, and sodium as functions... 47
Figure 19. Fitted (a, d, g, j) C1s, (b, e, h, k) F1s and (c, f, i, l) Bi 4f spectrum of (a-c) DME-, (d-f) THF-, (g-i) DEGDME-, and (j-l) EC/DEC-derived SEI at surface and interior. 48