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전기자동차용 리튬이온전지의 열적거동 모델링

Thermal modeling of a lithium-ion battery for electric vehicle applications

초록/요약

The lithium-ion battery (LIB) is a preferred power source for electrically propelled vehicles because of its high energy density, high power, and low self-discharge rate. Because battery performance and battery life are strongly dependent on battery temperature, thermal control of the LIB is particularly important. To control the temperature of an LIB cell within a suitable range for the various electrically propelled vehicles operating conditions, it is essential to calculate the uneven temperature distribution of an LIB cell accurately based on thermal modeling and to validate the model by comparing the modeling results with the experimental measurements. Modeling can play an important role for exploring various battery pack cooling strategies in electrically propelled vehicle applications. This thesis reports a modeling methodology of an LIB considering the effects of the various conditions for electrically propelled vehicle applications. These include modeling of the temperature dependence of the discharge behavior of an LIB in low environmental temperature, modeling of the transient behaviors of an LIB battery during dynamic cycling, and Three-dimensional thermal modeling of an LIB considering the combined effects of the electrical and thermal contact resistances between current collecting tab and lead wire. The first part of this thesis is a modeling methodology on the temperature dependence of the discharge behavior of an LIB in low environmental temperature. The discharge curves from the modeling for the discharge rates ranging from 0.5 C i to 5 C under the low environmental temperatures of -20, -10 and 0 oC are compared with the experimental data in order to validate the two-dimensional modeling of the potential and current density distributions on the electrodes of an LIB cell as a function of the discharge time during constant-current discharge. The heat generation rates as a result of electrochemical reactions and ohmic heating are calculated to predict the temperature variations of the LIB as a function of the discharge time. The temperature variations obtained from the modeling agree well with the experimental measurements. The second part of this thesis is a modeling methodology on the transient behaviors of an LIB during dynamic cycling. To account for the short time effects of current pulses and rest periods, the nonfaradaic component of the current density transferred through the separator between the positive and negative electrodes is included based on the lumped double-layer capacitance. Two-dimensional modeling is performed to predict the transient behaviors of an LIB cell during dynamic cycling. To validate the modeling approach presented in this part, modeling results for the variations in cell voltage and two-dimensional temperature distribution of the LIB cell as a function of time are compared with the experimental data for constant-current discharge and charge cycles and the Heavy Duty Urban Dynamometer Driving Schedule cycles. The transient behaviors obtained from the modeling agree well with the experimental measurements. The last part of this thesis is Three-dimensional thermal modeling of an LIB considering the combined effects of the electrical and thermal contact resistances ii between current collecting tab and lead wire. The combined effects of the thermal and electrical contact resistances between the current collecting tab of an LIB cell and the lead wire connecting the cell to an external cycler are considered explicitly in addition to the heat generated as a result of electrochemical reactions and ohmic heating in the electrode region of the battery cell. The effect of electrical contact resistance is taken into account when calculating current collecting tab heating, and the effect of thermal contact resistance is included in the heat flux boundary condition at the contact area between the current collecting tab and the lead wire. The three-dimensional thermal modeling is validated by comparing the modeling results with experimental temperature distributions from IR images during discharge in an LIB cell.

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목차

Chapter 1. Introduction 1
1.1. Lithium-ion battery 1
1.2. Thermal issues of LIB 5
1.2.1. Safety issues related with thermal effect of LIB 5
1.2.2. Ageing issues related with thermal effect of LIB 6
1.2.3. Thermal modeling of LIB 7
1.3. Objectives 10
Chapter 2. Modeling the temperature dependence of the discharge behavior of a lithium-ion battery in low environmental temperature 12
2.1. Introduction 12
2.2. Mathematical model 15
2.3. Results and discussion 29
Chapter 3. Modeling of the transient behaviors of a lithium-ion battery during dynamic cycling 43
3.1. Introduction 43
3.2. Mathematical model 44
3.3. Results and discussion 56
Chapter 4. Three-dimensional thermal modeling of a lithium-ion battery considering the combined effects of the electrical and thermal contact resistances between current collecting tab and lead wire 74
4.1. Introduction 74
4.2. Mathematical model 76
4.3. Results and discussion 82
Chapter 5. Summary and Conclusions 103
Chapter 6. Recommendations for Further Research 106
Bibliography 110
국 문 초 록 119
List of publications 121
Appendix A. Nomenclature 127
Appendix B. Experimental measurements 130
Appendix C. Battery glossary 133

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