Thermal modelling and simulations of lithium-ion battery systems

Much attention has been paid on lithium-ion batteries recent years because of their wide applications in portable electronic devices as well as in vehicles, ships and aircrafts. However, lithium-ion battery has problems of poor safety characteristics caused by high heat generation and the temperature rise during charge and discharge. High temperature affects the performance, reliability and lifespan of the battery and may cause serious safety hazards such as thermal runaway, even ignition. Therefore, the investigation and thermal management of lithium-ion battery are critical issues in research field. This thesis is concerned with thermal investigation and management of lithium-ion battery and battery module. The key aspects in the exploration, design, analysis and management of lithium-ion battery/battery module covered in this thesis are in the sequence as follows: (1) simplified one-dimensional mathematical thermal model of lithium-ion single cell; (2) three-dimensional transient thermal model of lithium-ion single cell based on the actual structure of battery; (3) investigation of forced air cooling strategy and design of battery module structure for lithium-ion battery module based on empirical heat source model; (4) exploration of optimal forced air cooling method; (5) simulation on battery module liquid cooling method. Thermal models are essential part in the research and application of lithium-ion battery. In this thesis, both one-dimensional and three-dimensional thermal models are developed for different application conditions. The one-dimensional thermal model is simplified from existed electrochemical model which describes the reaction process of lithium-ion battery during charge/discharge in a mathematical approach to describe the battery temperature behavior during operation. The three-dimensional transient thermal model is based on the experimental data and the actual structure of lithium-ion battery. Thermal behaviors which include temperature changing trend and temperature distribution of battery under different working conditions are simulated. This thesis has also defined an empirical heat source model for battery module/pack simulation. Design, analysis and optimization of battery module with forced air cooling strategies as well as liquid cooling methods have been presented in this work based on empirical heat source model. The thermal behaviors of battery module under different cooling strategies and working conditions are simulated and compared, optimal cooling strategy are selected for applications. Doctor of Philosophy (EEE