Based Hybrid Electrolytes for Lithium-Metal Polymer Batteries
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Crosslinked Poly(Ethylene Glycol)-Based Hybrid Electrolytes for Lithium-Metal Polymer Batteries A Thesis Submitted to the Faculty of Drexel University by Ziyin Huang in partial fulfillment of the requirements of the degree of Master of Science in Materials Science and Engineering June 2016 © Copyright 2016 Ziyin Huang. All Rights Reserved. ii Dedications To my parents, Mr. Yongquan Huang and Mrs. Hongwei Qian, and to all the people and spirits that are guiding me. iii Acknowledgements First and foremost, I would like to thank my thesis advisor Prof. Christopher Li, whom I learned polymer physics from, for all the guidance for the past five years. Without him, I would not have gained experience in scientific research which helped me make my decision to pursue a PhD degree after graduation. I would like to thank my mentor, Dr. Qiwei Pan, for her the assistance and insights on experimental design and data interpretation in this project, and Dr. Shan Cheng, Dr. Derrick Smith, and Hao Qi for discussions. Prof. Kevin Owens and Dr. Jonathan Soffer for analytical chemistry instrument training. I would like to thank my committee members Prof. Ekaterina Pomerantseva and Prof. Andrew Magenau. I would also like to thank my mentors for previous projects, Dr. Wenda Wang, Dr. Bin Dong, Hang Kuen Lau, Dr. Tian Zhou, and Shan Mei, who patiently trained me with the fundamentals of experimentation and scientific research methods which are essential for me to take on the project for this thesis. I also thank the past and present members of the Soft Materials Lab, including Dr. Rebecca Chen, Dr. Eric Liard, Brittany Gallagher, Sarah Gleeson, Gabriel Burks, Tony Yu, and Weichun Huang, for the friendship and support. Additionally, I would like to thank the advice and support from the faculty and staff of the Department of Materials Science and Engineering, as well as the students and alumni from the materials science undergraduate class of sweet sixteen, class of 2015, The Iron Dragons bladesmithing team, Drexel Chapter of Material Advantage, and Tau Beta Pi Pennsylvania Zeta Chapter. Special thanks to my academic advisor Dr. Richard Knight iv who gave me support and showed me resources to help me succeed in academic, extracurricular, professional, and leadership activities that shaped who I am, and my engineering freshman mentor Alicia Kriete who watched me joined Drexel as a freshman before school started knowing nothing about Drexel or materials science and now witnesses me graduating with a master’s degree. Finally, I would like to thank my parents for their encouragement and optimism which helped me go through the five years of undergraduate study. v Table of Contents List of Tables ······················································································· vii List of Figures ····················································································· viii Abstract ····························································································· xiii Chapter 1. Introduction ············································································· 1 1.1. Overview ····················································································· 1 1.2. Motivation and project outline ···························································· 3 Chapter 2. Background ············································································· 4 2.1. Lithium-Ion Batteries and Lithium-Metal Batteries ···································· 4 2.1.1. Overview of the development of batteries ·········································· 4 2.1.2. Lithium batteries and lithium dendrite growth ····································· 7 2.1.3. Electrolytes for lithium-metal batteries ············································ 10 2.2. Polymer Electrolytes ······································································ 13 2.2.1. Types of polymer electrolytes ······················································ 13 2.2.2. Solid polymer electrolytes (SPEs) ·················································· 13 2.2.3. Lithium ion transport in PEG ······················································· 18 2.3. PEG/PEO-Based Crosslinked SPEs ····················································· 21 2.4. Problem Statement ········································································· 26 Chapter 3. Materials and Methods ······························································· 27 3.1. Materials ···················································································· 27 3.2. Methods ····················································································· 27 3.2.1. Synthesis of unplasticized crosslinked SPE films ································ 27 3.2.2. Synthesis of plasticized crosslinked SPE films ··································· 28 3.2.3. Lithium symmetric coin cell assembly ············································ 29 vi 3.3. Characterization Techniques ····························································· 30 3.3.1. Differential scanning calorimetry (DSC) ·········································· 30 3.3.2. Fourier-transform infrared spectroscopy (FTIR) ································· 32 3.3.3. Thermogravimetric analysis (TGA) ················································ 34 3.3.4. Tensile testing ········································································· 34 3.3.5. Electrochemical impedance spectroscopy (EIS) ·································· 35 3.3.6. Battery tester ·········································································· 39 Chapter 4. Composition Characterization and Thermal Analysis ··························· 42 4.1. Characterization of Reagents ····························································· 42 4.2. Crosslinking Characterization ···························································· 45 4.3. Thermal Stability ·········································································· 51 4.4. Mechanical Properties ····································································· 54 Chapter 5. Electrochemical Properties of Crosslinked Hybrid Electrolytes ················ 57 5.1. Ionic Conductivity ········································································· 57 5.2. Lithium Transference Number ··························································· 62 5.3. Polymer Electrolyte Stability ····························································· 64 5.4. Galvanostatic Polarization ································································ 71 5.5. Lithium Symmetric Cell Cycling ························································ 82 Chapter 6. Conclusions ············································································ 90 6.1. Summary ···················································································· 90 6.2. Outlooks ···················································································· 90 6.2.1. POSS-4PEG6k ········································································ 90 6.2.2. Mixed plasticizer for SPEs ·························································· 93 List of References ·················································································· 95 vii List of Tables Table 2-1. Types of electrolyte for lithium-metal batteries summarized from Ref [23]. 12 Table 3-1. Theoretical PEG250 content by weight in the samples ................................... 29 Table 4-1. FTIR spectra band assignments. ...................................................................... 47 Table 4-2. Thermal properties of POSS-4PEG2k samples measured by DSC. ................ 48 Table 4-3. Thermal properties of POSS-2PEG6k samples measured by DSC. ................ 49 Table 4-4. PEG250 weight percent calculation from TGA. ............................................. 54 Table 5-1. VTF fitting constants for the electrolytes. ....................................................... 58 Table 5-2. VTF constants by fitting modified VTF equation with T0 = Tg – 50 K. ......... 59 Table 5-3. VTF constants by fitting modified VTF equation. .......................................... 60 Table 5-4. Lithium transference number of the samples. ................................................. 63 Table 6-1. Thermal properties of POSS-2PEG6k0 and POSS-4PEG6k0 measured by DSC ........................................................................................................................................... 92 viii List of Figures Figure 1-1. Practical specific energies for some rechargeable batteries, along with estimated driving distances and pack prices.[3] ................................................................. 1 Figure 2-1. Block diagram of a simple electrochemical cell.[7] ......................................... 5 Figure 2-2. Comparison of volumetric and gravimetric energy densities of several common battery technologies.[4] ....................................................................................................... 6 Figure 2-3. History and future of batteries.[11] .................................................................. 7 Figure 2-4. Schematic of (a) lithium dendrite growth in lithium-metal battery and (b) lithium-ion battery.[4] ......................................................................................................... 8 Figure 2-5. Observation of lithium dendrite growth under in situ TEM for lithium-ion battery with LiPF6/EC/DEC electrolyte.[19] ....................................................................