Carrier ion diffusion and phase transition in anode materials and their effects on electrochemical properties of batteries

다국어 초록 (Multilingual Abstract)

Despite their wide applicability for portable electronic devices such as smart phones and laptop computers, Li-ion batteries (LIBs) lack high power density and suffer from safety hazard that are critical for emerging electric transportation systems. To this end, there has been much interest on finding alternative materials with higher specific capacity than traditional materials, while maintaining the required cycle life. One major attempt is to change the carrier ions from conventional Li to Na. This is because, Na not only exhibits electrochemical properties similar to those of Li but also is earth-abundant resources and thus, can be obtained with much lower prices. The other attempt to discover alternative battery materials is to use of alloying anodes. Alloying anodes react with carrier ions via an alloying mechanism: carrier ions diffuse into anodes by breaking the atomic bonds between host atoms to alloy with anode materials. This diffusion process is not constrained by the atomic framework of anodes and thus, can promote the insertion/extrusion of a large number of carrier ions to anodes, resulting in the high specific capacity of alloying anodes.
Above previous studies suggest that the proper selection of carrier ions (Li or Na) and alloying anodes can enable the development of batteries for future electric vehicles. Generally, the electrochemical properties of batteries are directly related to the diffusion behaviors and phase transitions occurring at anode materials. In this regard, by understanding these behaviors in alloying anodes can pave the way for selecting proper carrier ions and alloying anodes. In this study, we first address the effect of diffusion of carrier ions on the various electrochemical performances of energy efficiency, rate performance, and cycle life. In the following section, we interpret the relationship between the phase transition behaviors in alloying anodes and energy loss at anodes, or equivalently, energy efficiency of batteries. Based on above results, the present thesis suggests crude yet effective design criteria for developing future batteries with superior electrochemical performances.

목차 (Table of Contents)

• Chapter I Thesis overview 1
• 1. Introduction to alloying anodes for future batteries 1
• 2. Organization of the thesis 6
• 2.1. Summary of Chapter II 7
• 2.2. Summary of Chapter III 8
• 3. Acknowledgements 10
• References 12
• Chapter II Carrier ion diffusion in anodes and its effect on battery properties 14
• 1. Formation of Zintl clusters and their configurational change during sodiation in NaSn battery 14
• 1.1. Introduction 16
• 1.2. Methods 19
• 1.3. Results and Discussions 23
• 1.4. Conclusions 44
• References 45
• 2. Ultrafast Sodiation of Single-Crystalline Sn Anodes 48
• 2.1. Introduction 50
• 2.2. Methods 53
• 2.3. Results and Discussions 59
• 2.4. Conclusions 80
• References 81
• 3. Anisotropic Swelling Governed by Orientation-Dependent Interfacial Na Diffusion in Single-Crystalline Sb 85
• 3.1. Introduction 87
• 3.2. Methods 91
• 3.3. Results and Discussions 96
• 3.4. Conclusions 112
• References 113
• 4. Interfacial Reactions in the Li/Si diffusion couples: Origin of Anisotropic Lithiation of Crystalline Si in LiSi batteries 116
• 4.1. Introduction 118
• 4.2. Methods 121
• 4.3. Results and Discussions 124
• 4.4. Conclusions 142
• References 143
• Chapter III Phase transition in anodes and its effect on battery properties 145
• 1. Evaluation of energy loss at Sn anodes based on phase transition behaviors and formation of electrically resistive phases of NaSn batteries 145
• 1.1. Introduction 147
• 1.2. Methods 150
• 1.3. Results and Discussions 154
• 1.4. Conclusions 178
• References 179
• 2. Characterizing multiple continuous phase transitions at an alloying anode with voltammetric measurement and first-principles calculations 182
• 2.1. Introduction 184
• 2.2. Methods 188
• 2.3. Results and Discussions 196
• 2.4. Conclusions 219
• References 221
• 3. Continuous/reversible phase transition behaviors and their effect on the hysteresis energy loss of the anodes in Na-ion batteries 225
• 3.1. Introduction 227
• 3.2. Methods 231
• 3.3. Results and Discussions 234
• 3.4. Conclusions 262
• References 263
• 4. Phase transition behaviors and formation of electrically resistive phases at the anode: Major factors determining the energy efficiency of Li-ion batteries 267
• 4.1. Introduction 269
• 4.2. Methods 274
• 4.3. Results and Discussions 277
• 4.4. Conclusions 304
• References 305
• Chapter IV Concluding remarks 309
• 1. Summary of the Main Conclusions 309
• 1.1. Main conclusions of Chapter II 309
• 1.2. Main conclusions of Chapter III 312