Research Of Thermal Management Systems Based On Phase Change Materials For Lithium-ion Battery

Lithium-ion battery is the major power source of electric vehicles, it directly affect theperformance of electric vehicles. Temperature is an important parameter affecting theperformance of lithium-ion battery, and only at a reasonable temperature range can thebattery acquire its best performance. The battery thermal management system is an importantcomponent of the battery management system, responsible for controlling battery operatingtemperature within reasonable limits and reducing the temperature difference betweenmonomers to promote the performance of the battery pack as far as possible. In this thesis,paraffin wax is used as phase change material and a new type of lithium-ion battery thermalmanagement system based on paraffin is analyzed.Firstly, via the study of temperature characteristic of the battery, we tested thetemperature response of battery energy, battery dc-internal resistance, battery efficiency andbattery cycle life to decide the objective temperature of the battery thermal managementsystem.Secondly, establish the thermodynamic model to giving off heat generation rate underdifferent current. The thermal physical properties of paraffin wax are measured bydifferential scanning calorimetric method in order to calculate the required amount ofparaffin wax.Thirdly, build the electrode-non-stratification model of lithium-ion with finite elementanalysis software to simulate the temperature of batteries in the thermal management systemand give optimization to the system. With the simulation results, we found that comparedwith natural convection cooling, the thermal management system based on phase changematerial can obtain good performance under different temperatures, and can ease thetemperature rise effectively in thermal runaway condition. We also found that shell materialaffect the performance mostly, and put forward optimization proposes accordingly.Lastly, conduct tests of the thermal management system under different temperatures.The testing and simulation results are compared with each other to verify the FEA model.The testing results show that, with the use of thermal management system based on phasechange material, the maximum temperature in the battery pack never exceeds the safety limiteven working at maximum current, and the temperature difference among monomer cellsdecrease a lot compared with natural convection cooling. Use foam metal skeleton to form composite phase change material with paraffin wax, the testing results show that with thiscomposite phase change material in the thermal management system, the performance can beimproved effectively.