Title Page
Contents
ABSTRACT 9
Ⅰ. Introduction 11
Ⅱ. Experimental procedure 15
2.1. Materials 15
2.2. Material synthesis 15
2.2.1. Zn-modified cathode 15
2.2.2. Pristine SC-NCM90 16
2.3. Material characterization 16
2.4. Electrochemical measurements 17
Ⅲ. Results and discussion 19
3.1. Synthesis and material characterizations 19
3.2. Electrochemical characterizations 36
3.3. High temperature storage test 52
3.4. Differental scanning calorimetry(DSC) analysis 61
Ⅳ. Conclusion 63
References 64
국문초록 76
Table 1. Lattice parameters and degrees of Li/Ni mixing of Pristine SC-NCM90 and SC-NCM90@Zn3,10 31
Table 2. Initial charge-discharge capacities and coulombic efficiencies of Pristine SC-NCM90 and SC-NCM90@Zn1,3 38
Table 3. Fitting results for the EIS profiles of Pristine SC-NCM90 and SC-NCM90@Zn1 shown in Figure 14 obtained after the 100th cycle 51
Figure 1. Schematic diagrams illustrating the synthesis procedure of PVP-assisted Zn-modified NCM. 20
Figure 2. XRD patterns of Pristine SC-NCM90 and SC-NCM90@Zn3,10. 22
Figure 3. XRD patterns of Pristine SC-NCM90, undoped SC-NCM90@Zn10, and SC-NCM90@Zn10. 24
Figure 4. TEM image of the surface of SC-NCM90@Zn3. 25
Figure 5. (a) SEM, (b) TEM, and (c) TEM-EDS mapping images of Ni, Co, Mn, O, and Zn in SC-NCM90@Zn3. 27
Figure 6. Comparison of Rietveld analysis data for (a) Pristine SC-NCM90 and (b) SC-NCM90@Zn3 and (c) SC-NCM@Zn10. 30
Figure 7. Full-spectrum XPS profiles of Pristine SC-NCM90 and SC-NCM90@Zn3 and (b) XPS profile of Zn 2p in SC-NCM90@Zn3.... 33
Figure 8. (a) Schematic illustration of Zn near-surface region doping on the Ni-rich single-crystal cathode. (b) XPS depth profile... 35
Figure 9. First charge/discharge profiles of Pristine SC-NCM90, SC-NCM90@Zn1, and 3 at 0.1 C. 37
Figure 10. (a) Discharge capacity and (b) discharge profiles of rate-dependent cycling performance for Pristine SC-NCM90,... 41
Figure 11. (a) Nyquist plots of Pristine SC-NCM90, SC-NCM90@Zn1, and SC-NCM90@Zn3 of the initial cycle. (b)... 42
Figure 12. (a) Capacity retention of Pristine SC-NCM90 and SC-NCM90@Zn1 at a constant current of 1 C-rate in a voltage... 45
Figure 13. (a) Galvanostatic intermittent titration technique (GITT) potential profiles after the 100th cycle of Pristine SC-NCM90 and... 47
Figure 14. Nyquist plots of Pristine SC-NCM90 and SC-NCM90@Zn1 at (a) the initial cycle and (b) after 100th cycles under open... 50
Figure 15. Process flowchart for the 60 °C exposure test. 54
Figure 16. Comparison of the (a) cycle performance and (b) average charge/discharge voltage of Pristine SC-NCM90 and... 55
Figure 17. O 1s and F 1s XPS profiles of Pristine SC-NCM90 and SC-NCM90@Zn1 electrodes (a) after 3 cycles of formation cycle... 58
Figure 18. HR-TEM and FFT images of (a) Pristine SC-NCM90 and (b) SC-NCM90@Zn1 after 3 cycles of formation (25 °C) and after... 60
Figure 19. DSC test results of Pristine SC-NCM90 and SC-NCM90@Zn1 electrodes measured in the electrolyte solution... 62