Title Page
Contents
ABSTRACT 10
Chapter 1. Introduction 12
1.1. Research background 12
1.2. The fundamentals of ultrasound 13
1.3. Research purposes 15
1.4. Application of ultrasound in battery testing 16
Chapter 2. Simulation of ultrasonic response 17
2.1. Battery cell modelling 17
2.1.1. Cell structure 17
2.1.2. Selection of material parameters 19
2.2. Result and discussion 22
2.2.1. Time domain study 22
2.2.2. Frequency domain study 23
2.2.3. Piezo layer materials comparison 26
2.2.4. Effect of each layer thickness in PUT 29
2.2.5. Matching layer 31
Chapter 3. Experimental ultrasonic detection 33
3.1. Experiment 33
3.1.1. Charging/discharging of lithium-on battery cell 33
3.1.2. Ultrasonic testing during charging/discharging 34
3.2. Result and discussion 36
3.2.1. Ultrasonic signal response analysis based on SoC 36
Chapter 4. Battery equivalent model modeling 38
4.1. Experimental 38
4.1.1. Modeling of commercial ultrasonic transducers 38
4.1.2. Optimal parameter design 40
4.2. Result and discussion 42
4.2.1. Modeling of commercial ultrasonic transducers 42
4.2.2. Optimal parameter design 47
Chapter 5. Conclusions 49
References 51
Abstract (in Korean) 53
Table 1-1. Piezoelectric ultrasonic transducer model size 18
Table 2-1. 210 mAh LCO pouch cell properties 21
Table 2-2. Electrode material properties of each SOC 21
Table 2-3. Piezo layer combination method 28
Table 2-4. Acoustic impedance of materials and optimal acoustic impedance 32
Table 4-1. PN series material parameters 38
Table 4-2. Material parameters used in simulation 46
Table 4-3. Optimal parameter design from inversion 48
Figure 1-1. Method of propagation of pressure and shear waves 14
Figure 1-2. Pulse-echo method vs. transmission method 15
Figure 2-1. Detailed battery layer structure and single cell model 17
Figure 2-2. PUT model and physical field settings 18
Figure 2-3. Cathode/anode material properties for ultrasonic simulation 20
Figure 2-4. Simulation output; (a) ultrasonic time-domain signaling of batteries at different SoC and (b) time of flight and peak values 22
Figure 2-5. Fast Courier Transform of time domain signals 24
Figure 2-6. The impact of center frequency and bandwidth changes with SoC 24
Figure 2-7. Sound pressure when AlN / PZT-5H are used as piezo layers in hydroacoustic simulation 26
Figure 2-8. Simulation results of single-cell ultrasonic response in time/frequency domain with different piezo layer combinations; (a) ToF, (b) peak value, (c) center... 28
Figure 2-9. Model setup for hydroacoustic experiments 29
Figure 2-10. Effect of thickness of each layer in PUT on the emitter sound pressure; (a) piezo layer, (b)backing layer, (c) matching layer 30
Figure 2-11. Acoustic impedance test model setup 31
Figure 2-12. Effect of different matching layers on the sound pressure of ultrasonic emission 31
Figure 3-1. Schematic of an ultrasonic detection system with battery cell 33
Figure 3-2. Photo of ultrasonic Tx-Rx experiment 34
Figure 3-3. Charge/discharge characteristic curve 36
Figure 3-4. Time-frequency domain and eigenvalues of ultrasonic response signals; (a) ultrasonic response signals of different SoCs in the time domain, (b) variations... 37
Figure 4-1. Tx input and glass Tx-Rx experiment 39
Figure 4-2. Commercial PUT modeling and Tx-Rx glass simulation 40
Figure 4-3. Flowchart for establishment of battery equivalent model 40
Figure 4-4. 2D homogenized battery equivalent model 41
Figure 4-5. Frequency response curves and modal of piezo layers 42
Figure 4-6. Comparison of simulation and experiment for Tx_Rx ultrasonic testing of glass; (a) time domain, (b) frequency domain (FFT) 43
Figure 4-7. Modeling of Tx_Rx ultrasonic test of water 44
Figure 4-8. Comparison of simulation and experiment for Tx_Rx ultrasonic testing of water; (a) time domain, (b) frequency domain (FFT) 44
Figure 4-9. Modeling of Tx_Rx ultrasonic tests in acrylic plate 45
Figure 4-10. Comparison of simulation and experiment for Tx_Rx ultrasonic testing of acrylic plate; (a) time domain, (b) frequency... 45
Figure 4-11. Comparison of experiments and simulation of equivalent models at 0%,50,100% SoC about time(left)-frequency(right) domain; (a) SoC 0%, (b) SoC... 47