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Thermal Behavior of Rechargeable Li-ion Batteries; Experimental Evaluations and Modeling

Shadman Rad, Mojtaba | 2013

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 45062 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Baghalha, Morteza; Kazemeini, Mohammad
  7. Abstract:
  8. The main objective of this research is to experimentally evaluate thermal behavior of commercially available rechargeable Li-ion batteries based on minimum measurements on main battery parameters and then develop experimental based models to investigate their thermal behavior. Li-ion batteries with Graphit anodes and Li(Ni0.8¬Co0.15Al0.05)O2 cathodes will be used for this purpose. Voltage and temperature developments during cycling under various currents at controlled ambient temperatures are measured by battery tester. Measurements show that temperature evolutions demonstrate falls and rises at specific State-of-Charge (SoC) of the battery during cycling and therefore some heat consumers rather than heat generation resources exist in the battery operation and it is studied carefully in the current work. Equilibrium voltages, overpotentials and also entropy changes are determined and reported for this battery system. Polynomial regression (PR) and Galvanostatic Intermittent Titration Technique (GITT) are introduced in order to determine equilibrium voltages and it is shown that PR method is more accurate for determination of equilibrium voltage. Then, a lumped thermal model is developed and an optimization procedure is introduced to determine entropy changes. The lumped model can predict the temperature development of the battery accurately in compare to the experimental measurements. In the next step, the model is extended in axial-radial coordinates to evaluate the internal temperature variations as well. It is shown that low thermal conductivity of the battery is one of the important parameters for temperature differences between the surface and core of the cell. However, heat capacity and heat transfer coefficient with surrounding are also other important parameters. Two-dimensional model with coupled MATLAB-COMSOL programming provides an advanced structure for Battery Management Systems (BMS). Consequently, the model is extended to three-dimensional for single cell and then, to battery module. Details of the battery components, e.g. casing, plastic cover, active materials and terminals are taken into account in 3-D model. In addition to, discharge voltage curve upon 45 A current is simulated based on 7.5, 10 and 15 A currents. Thermal behavior of single and module of battery with various arrangements are investigated. Eventually it is shown that each arrangement has different thermal effects. Air and water laminar flow are also added to the model in order to accurately simulate various battery structures and temperature control mechanisms. Good agreement between experiments and model results are achieved
  9. Keywords:
  10. Lithium Batteries ; Thermal Modeling ; Thermal Behavior ; Computational Fluid Dynamics (CFD)

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