Compound Forming And Performance Study Of Cutting Copper Fiber/Paraffin Composites For Heat Dissipation Of Lithium Battery Module

With the lack of energy and the society to strictly control of environmental pollution, electric vehicles and hybrid vehicles have become a major focus of development of today’s automotive industry. Since the 1950 s, lithium metal was introduced into the battery field, lithium batteries have been in rapid development in the past few decades. With its high specific energy, the advantages of small self-discharge rate, long cycle life, no memory effect, large capacity and no pollution, lithium-ion batteries are now available as a mainstream power source of new energy vehicles, but the thermal safety issues still restrict its popularization and application.In order to achieve the best battery performance, prolong the service life and eliminate the potential danger, it is needed to control the battery temperature in the normal operating range and reduce the temperature nonuniformity of the batteries within the battery pack. In view of the above situation, cutting copper fiber/paraffin wax was used as composite phase change material(PCM) for the heat dissipation of the lithium battery module. The heat generation characteristics of lithium ion battery in the work process and the heat transfer performance of the phase change material were studied using experimental and numerical calculation methods. This paper mainly includes the following aspects:(1) The heat dissipation module based on phase change materials was designed and manufactured. Continuous copper fibers were manufactured using multi-tooth cutting tool and copper fiber sintered felts were made with different porosity. The sintering process and formation mechanism were studied. Afterwards paraffin wax was poured into the porous felts and composite phase change materials were formed.(2) DSC tests were conducted to the composite phase change materials. The test results showed that after adding copper foam or copper fiber felts into the paraffin, latent heat and specific heat capacity of the composite materials had a large decline, showing an obvious impact on them.(3) The batteries were wrapped around by the composite phase change materials and experimental studies on the discharge of the battery module in 10 A, 20 A and 35 A current were carried out to examine the heat dissipation effect of the materials. The testing results showed that, with the use of thermal management system based on phase change material, the maximum temperature in the battery pack never exceeded the safety limit even working at maximum current, and the temperature difference among monomer cells decreased a lot compared with natural convection cooling. The testing results showed that with this composite phase change material in the thermal management system, the performance can be improved effectively and ensure the safety of the battery module.(4) Use the numerical method to simulate the heat transfer problem in a lithium battery module in the use of composite phase change material. A two-equation non-thermal equilibrium model was employed to model the battery module, the Enthalpy Method was employed in this study in order to cope with the phase change heat transfer problem, and it was solved using finite difference method by programming in Matlab. Calculation results were compared with the experimental results and there is a good agreement between them, indicating the correctness and the accuracy of modeling and solving process.