Ⅰ. Introduction 1 1.1 Overview of lithium-ion battery 1 1.2 Challenges of fast charging · 2 1.3 Electrolytes design for fast charging 3 1.4 Research goal 4 Ⅱ. Experimental method 2.1 Electrode fabrication 6 2.2 Cell assembly 6 2.3 Electrochemical testing 6 2.4 Characterization 7 2.5 Computational simulation 8 Ⅲ. Result and Discussion 3.1 Electrolyte design: PHCEs · 10 3.2 Changes in solvation structure depending on the type of diluent 13 3.3 Interfacial changes due to variation in solvation structure · 16 3.4 Scenarios of anion and additive co-derived SEI formation with HCE and PHCEs 21 3.5 Electrochemical performances of Li-ion full cells under extreme conditions 22 Ⅳ. Conclusion · 26 References 27 Summary in Korean · 32