Chapter 1 18

Figure 1.1. The necessity of developing efficient energy storage system (ESS) to apply renewable energy sources for the usage of electric vehicles (EV), industrial fields and portable IT devices. Note... 18

Figure 1.2. (a) Practical volumetric and gravimetric energy densities per technology at cell level: current high-energy LIB cell as minimum and advanced LIB configuration (the latter using, for example, a... 19

Figure 1.3. (a) Practical volumetric and gravimetric energy densities per technology at cell level: current high-energy LIB cell as minimum and advanced LIB configuration (the latter using, for example, a... 21

Figure 1.4. Schematic illustration of the Li-ion battery. 22

Figure 1.5. Important considerations for the appropriate electrolyte design. 25

Figure 1.6. An outline of the battery thermal runaway mechanisms and the thought of time sequence regulation. 27

Figure 1.7. Redox potential of electrode materials for Li-ion batteries and electrochemical stability window of pure water (pH 7) and aqueous (WiS) electrolytes. 29

Figure 1.8. General trend for the present automobile battery R&D objectives with respect to the employed anode, electrolyte, and cathode materials; please note that this trend is to be taken rather... 31

Figure 1.9. Methods and their traits applied in multi-scale computational approach in this thesis, according to time and length scales; density functional theory (DFT) and molecular dynamics (MD) simulation. 34

Figure 1.10. Role of molecular simulation, which arbitrate theory and experiment 34

Figure 1.11. DFT abandons the many-particle electron reality in favor of electron density. Constitutive relations constructed to relate energy to this density seek to capture the self-interactions of electrons. 35

Figure 1.12. Illustration of the fundamental force field energy terms. 36

Chapter 2 51

Figure 2.1.1. RDF profiles of the phosphorous atom of PF₆⁻ (a), Li⁺ atom (b) at the binder-electrolyte interface. (c), Rinternal and DLi⁺ of the c-IPN (vs. control n-IPN) cathodes (M/A ＝ 65 mg cm⁻²) as a function of discharge voltage, which were estimated from the GITT results. (d), Schematic illustration depicting...[이미지참조] 51

Figure 2.1.2. RDF profiles and coordination number (between Li⁺ and solvents in the liquid electrolyte) of EC (a), DEC (b), and PF₆⁻ (c) at the binder (n-IPN vs. c-IPN)-electrolyte interface and coordination... 52

Figure 2.1.3. HOMO energy levels and relative ratios of the Li⁺ solvation structures in the liquid electrolyte (1M LiPF₆ in EC/DEC ＝ 1/1 (v/v)): n-IPN (a) and c-IPN (b) cathode. The major Li⁺ solvation... 53

Figure 2.1.4. (a) Relative ratio of Li⁺ solvation structure of the liquid electrolyte (1M LiPF₆ in EC/DEC ＝ 1/1 (v/v)) inside the n-IPN and c-IPN cathodes. The Li⁺ solvation structures are denoted as X-Y-Z,... 54

Figure 2.2.1. (a) Photograph of the AEE and control electrolytes (dilute aqueous electrolyte (1 m LiTFSI in water) and organic electrolyte (1 M LiPF₆ in EC/DMC ＝ 1/1 (v/v))) at -40 ℃. (b) Ionic... 63

Figure 2.2.2. (a) Arrhenius plots of Rct for the eutectic HSC and dilute HSC (control). (b) Interaction energy (△Eint) between ions and water molecules at various temperatures: AEE vs. dilute aqueous...[이미지참조] 65

Figure 2.2.3. Radial distribution function (g(r)) (solid line) and coordination number (dotted line) at (a-b) the dilute electrolyte and at (c-d) the AEE, between Li⁺ and (a, c) oxygen atom of water molecules,... 66

Figure 2.2.4. Representative solvation structure type of Li⁺ for (a) free ions, (b) solvent separated ion-pair (SSIP), and (c) contact ion-pair (CIP) in the AEE. Purple, red, yellow, blue, gray, white and cyan... 66

Figure 2.2.5. Comparison in the free energy for Li⁺ solvation (∆Gsolv*(Li)) between the dilute aqeuous electrolyte (for the free Li⁺ ion state) and AEE (for the SSIP state) at 298 K.[이미지참조] 67

Chapter 3 79

Figure 3.1. Electrostatic potential of anions depicted on the isosurface of electron density with isovalue 0.08 a.u. 79

Figure 3.2. The relation between the strongest electrostatic potential and water structure forming properties in various kinds of anions. Note that anion-water interaction energy, water coordination number and anion-water distance are averaged value from the last 2ns of MD trajectories. 79

Figure 3.3. Hydration structure of (a) TFSI⁻, (b) OTf⁻, (c) Cl⁻, (d) OAc⁻, and (d) SO₄²⁻ anions. Gray, blue, white, red, yellow, cyan and light green balls represent carbon, nitrogen, hydrogen, oxygen, sulfur,... 80

Figure 3.4. Calculated Hildebrand solubility parameter (δ) of the single-phase electrolytes. 80

Figure 3.5. (a) Photograph of miscibility tests between aqueous electrolytes/AN (1/1, v/v) at ambient temperature. (b) Snapshots of AN/Aqueous electrolytes after 5 ns of MD simulation. (c) Time evolution of the interaction energy (△Eint) between aqueous electrolytes and AN. Note that △Eint is normalized by the...[이미지참조] 82

Figure 3.6. Calculated Hildebrand solubility parameter (δ) of the solvents and electrolytes. △δ denotes the difference in the solubility parameter between the two components in system. 83

Figure 3.7. MD simulation result of the miscible phase of the solvent mixture (a), and immiscible phase of the electrolyte mixture (b). H₂O, AN, Zn²⁺, SO₄²⁻, and TFSI⁻ molecules are depicted as blue, orange,... 84

Figure 3.8. Time evolution of the demixing index (χdemix) (a) and the interaction energy between components (△Eint) (b) calculated for electrolyte mixture and solvent mixture for the 50 ns of MD...[이미지참조] 85

Figure 3.9. (a) The system for MD simulation to calculate ion conduction mechanism of Zn²⁺ ion, transported through interface region of ZBPE electrolyte. H₂O, AN, Zn² , SO₄²⁻, and TFSI⁻ molecules are depicted as blue, orange, cyan, red and green color, respectively. (b) PMF profiles for Zn²⁺ ion transportation.... 86

Chapter 4 94

Figure 4.1. (a) Schematic comparison of ion transport phenomena in various ion conductors: traditional conductors versus an ideal conductor. (b) Chemical structure of the LiGQ and its self-assembly... 94

Figure 4.2. (a) Optimized structure of Li⁺ centered quartet, ribbon A and ribbon B, which are self-assembly structure made of guanine molecule. Orange, gray, white, blue, red, yellow colors represent lithium,... 98

Figure 4.3. (a) Three variables that are considered to find the most stable stacking sequence of LiGQ. (b) Contour plot of relative formation energy, with every possible combination of variables. (c) The most stable stacking sequence found for LiGQ. 100

Figure 4.4. (a) Initially constructed systems to elucidate position of anions. In "Trapped anion" system, all anions are bound to G-quartet at initial structure while "Free anion" system is not. (b) Anion position... 102

Figure 4.5. (a) Relaxed structure of LiGQ with and without Li salts, respectively. (b) Inner hydrogen bond distribution of G-quartet for the last 100 ps of trajectory. (c) Outer hydrogen bond distribution of... 103

Figure 4.6. Contour plot of Li⁺ number density of the LiGQ under an electric field. Red bar indicates the 2D number density of Li⁺ projected to the yz-plane. 104

Figure 4.7. (a) Schematic depicting direction of applied electric field E relative to Li channel direction (along z-axis). (b) MSD of Li⁺ and OTf⁻ under 2 V nm⁻¹ strength of electric field applied to LiGQ along... 105

Figure 4.8. (a) Schematic representation of the chemical structures and Li⁺ binding states of the LiGQ and conventional single-ion conductors. (b) PDOS of the ion-conducting moieties and Li⁺. Colored and... 107

Figure 4.9. Contour plot of relative formation energy, with every possible combination of variables for central cation (a) Na⁺, (b) K⁺ and (c) Mg²⁺. 110

Figure 4.10. Structural variations between the G-quadruplexes in terms of (a) the number of valence electrons and (b) ionic size, and (c) the ion conduction barrier of the G-quadruplexes, which can be affected by (d) the electrostatic and (e) Van der Waals interactions of G-quadruplexes. 113