Ziyuan Wang

Experimental study of a passive thermal management system for three types of battery using copper foam saturated with phase change materials

Battery thermal management (BTM) technology is vital for the development of new energy vehicle because the lithium batteries exhibit a more resistive behavior leading to extra heat generation with age. The CF/PCM (copper foam/phase change material) coupled thermal management system for different types of lithium ion batteries such as 26650, 42110 and square (105 mm × 28 mm × 71 mm) were selected comparatively to research in detail, especially at a relatively high discharge rate. To evaluate the effect of the battery generating heat close to the actual operating conditions, the thermal management system in an insulated environment were investigated at discharge rate of 5C, in comparison with a natural convection environment. Furthermore, the results show that the effect of the temperature control based PCM is improved when compared to air-based BTM under an insulated environment. Moreover, the maximum temperature of 26650, 42110 and square batteries of CF/PCM coupled with BTM can be controlled below 44.37 °C, 51.45 °C and 50.69 °C for a longer time than those of the pure PCM based case and air-based case under the same conditions, respectively. The passive system was coupled with copper foam as a skeleton net structure to improve the strength of the PCM during its melting. More importantly, a CF/PCM (copper foam/phase change material) battery thermal management system was designed and tested experimentally.

Thermal management investigation for lithium-ion battery module with different phase change materials

Lithium-ion batteries, with their advantages of high energy and power density, have attracted much attention for application in electric vehicles and hybrid electric vehicles. However, there have been increasing reports of lithium-ion batteries catching fire and exploding in recent years, so there is a need for a battery thermal management (BTM) system to ensure battery safety performance. In this study, a novel shaped stabilized structure (paraffin/expanded graphite/epoxy) of composited materials was investigated for the 18 650 batteries module. The selected batteries were evaluated at different conditions to ensure the consistency of batteries initially. Then, different kinds of PCM were applied in the batteries module for thermal management, such as PCM 1 (pure paraffin), PCM 2 (EG 20%, paraffin 80%) and PCM 3 (EG 3%, epoxy 47%, paraffin 50%). The maximum temperatures of the battery modules with PCM 2 decreased more than 10%, 12% and 20% at 1C, 3C and 5C discharge rates, respectively, while paraffin mixed with expanded graphite. Furthermore, PCM can be modified by epoxy: the temperature of the module with PCM 3 was 59.79 °C while that of the module with PCM 2 was 64.79 °C after 30 charge–discharge cycles, revealing that epoxy as a plasticizer can cure the melting paraffin, preventing PCM leakage as the cycle number of the battery increases. The composite materials provide a promising solution to control temperature and decrease temperature difference in batteries modules.

A study on structure-performance relationship of overcharged 18650-size Li4Ti5O12/LiMn2O4 battery

The electrochemical properties and thermal generation behavior of 18650 Li4Ti5O12/LiMn2O4 batteries were tested before and after overcharge. The experimental results showed that after overcharge, the specific capacity decreased obviously. The higher the current density was, the more obvious the capacity decreased. For instance, the overcharged battery had almost no capacity when the current density increased to 5C. At the same time, the overcharged battery presented a much more apparent thermal runaway trend compared to the normal battery. After measuring the electrochemical impedance spectroscopy of the batteries and characterizing the crystal structure/nanostructure of the electrode materials, these phenomena could be attributed to the following two reasons: (1) the decomposition of the electrolyte arisen from the overcharge process resulted in increased internal resistance; (2) the thermal runaway due to the increased internal resistance resulted in the damage to crystal structure/nanostructure and aggregation of the electrode materials, thus leading to the secondary decrease in capacity.