The Influence of Internal Parameters on the Electrochemical and Thermal Behaviors of Lithium-Ion Batteries by Rui Zhao A thesis submitted to the Faculty of Graduate and Postdoctoral Affairs in partial fulfillment of the requirements for the degree of Master of Applied Science in Materials Engineering Carleton University Ottawa, Ontario © 2014 Rui Zhao Abstract Lithium ion (Li-ion) batteries, consisting of multiple electrochemical cells, are complex system whose high electrochemical and thermal stability is often critical to the well-being and functional capabilities of the electric device. Considering any change in the specifications may significantly affect the overall performance and life of a battery, an investigation of the impacts of the electrode thickness and initial electrolyte salt concentration on the electrochemical and thermal properties of lithium-ion cells based on experiments and a coupling model composed of a 1D electrochemical model and a 3D thermal model is conducted in this work. Pertinent results have demonstrated that the electrode thickness as well as the electrolyte salt concentration can significantly influence the battery from many key aspects such as the energy density, voltage, temperature, distribution and proportion of different heat sources and ability to prevent lithium plating. ii Acknowledgements First and foremost, I would like to express my great gratitude to my supervisors, Dr. LIU Jie and GU Junjie, for their enthusiastic supervision and patient guidance. They guided me throughout my entire master program. Without their perspectiveness, knowledge, constant support and encouragement, it is impossible for me to have the current thesis. In addition, I wish to acknowledge of Dr. ZHANG Zhonghua in the technical suggestion. This research work is financially supported by Natural Sciences and Engineering Research Council of Canada, Ontario China Research and Innovation Fund, and Carleton University. I would also like to express my appreciation to ZHANG Sijie, another student in the lithium-ion battery research group, for her tremendous help and scientific support. In addition, I am indebt, forever, to my parents for their endless understanding, support and encouragement. iii Table of Contents Abstract .............................................................................................................................. ii Acknowledgements .......................................................................................................... iii Table of Contents ............................................................................................................. iv List of Tables .................................................................................................................... vi List of Illustrations .......................................................................................................... vii Nomenclature .................................................................................................................... 1 1 Chapter: Introduction ................................................................................................ 5 1.1 Overview and Related Issues .......................................................................................... 5 1.2 Objectives and Thesis Organization ............................................................................... 8 1.3 List of Contributions ....................................................................................................... 9 2 Chapter: Background and Literature Review ....................................................... 11 2.1 Lithium-ion Battery ...................................................................................................... 11 2.1.1 Internal Structure of Li-ion battery .......................................................................... 13 2.1.1.1 Negative Electrode (Anode) ............................................................................ 15 2.1.1.2 Positive Electrode (Cathode) ........................................................................... 16 2.1.1.3 Separator .......................................................................................................... 18 2.2 Thermal Issues of Li-ion Battery .................................................................................. 20 2.3 Review of Li-ion Battery Modeling ............................................................................. 23 3 Chapter: Experimental Setup and Mathematical Modeling ................................ 26 3.1 Experimental Setup ...................................................................................................... 26 3.2 Mathematical Modeling ................................................................................................ 31 3.2.1 Electrochemical Model ............................................................................................ 33 3.2.2 Thermal Model ......................................................................................................... 37 iv 4 Chapter: The Evaluation of the Impact of Electrode Thickness on the Electrochemical and Thermal Behaviors of Li-Ion Battery ....................................... 40 4.1 Overview ...................................................................................................................... 40 4.2 Model Validation and Experimental Results ................................................................ 40 4.3 Simulated Thermal Behaviors of Two Experimental Batteries .................................... 45 4.4 Simulated Electrochemical and Thermal Behaviors of Batteries at High Rate ............ 49 4.5 Summary....................................................................................................................... 58 5 Chapter: The Evaluation of the Impact of Initial Electrolyte Salt Concentration on the Performance of Li-ion Battery ........................................................................... 60 5.1 Overview ...................................................................................................................... 60 5.2 Charging Process .......................................................................................................... 60 5.2.1 Simulated Results and Discussion............................................................................ 61 5.3 Discharging Process ..................................................................................................... 70 5.3.1 Simulated Results and Discussion............................................................................ 71 5.4 Summary....................................................................................................................... 84 6 Chapter: Conclusion and Future Work .................................................................. 85 6.1 Conclusion .................................................................................................................... 85 6.2 Future Work.................................................................................................................. 87 Bibliography .................................................................................................................... 88 v List of Tables Table 1. Summary of reviewed capacity fade high temperature cycling studies [1]. ....... 25 Table 2. Specification of the LiMn2O4 batteries. .............................................................. 30 Table 3. Parameters used in the 3D thermal model [75-77]. ............................................ 31 Table 4. Parameters used in 1D electrochemical model [65, 69]. .................................... 37 vi List of Illustrations Figure 2.1. Ragone plot of various electrochemical energy storage and conversion devices [21]. ................................................................................................................................... 12 Figure 2.2 Market share of secondary cells [22].............................................................. 12 Figure 2.3. Internal structure picture of a commercial Li-ion battery. ............................. 14 Figure 2.4. Schematic illustrations of a) 1 D electrochemical model and b) 3 D thermal model................................................................................................................................. 14 + Figure 2.5. Voltage curves for Li insertion and extraction of LiMn2O4 [50]. ................. 17 Figure 2.6. Comparison of charge/discharge voltage curves of Li[Ni0.5−xMn1.5+x]O4 with those of LiCoO2 and LiFePO4 [50]. .................................................................................. 18 Figure 2.7. Separator thermal shutdown [52]. .................................................................. 19 Figure 2.8. The photographs of the PP membrane and PI nonwoven before (a) and after (b) thermal treatment at 150 °C for 1 h [53]. .......................................................................... 20 Figure 3.1. Photograph of 10 Ah battery (Cell 1, ECPC-SP1037) with thick electrodes used. ........................................................................................................................................... 27 Figure 3.2. Photograph of 9 Ah battery (Cell 2, ECPC-SP8532) with thin electrodes used. ........................................................................................................................................... 27 Figure 3.3. Thickness gauge used in the