Abstract:In order to solve the problem of battery thermal management, a new battery temperature control device based on the coupling of stearic acid and thermal switch of phase change material is proposed. In this paper, the temperature control device of phase change material coupled thermal switch was used to study the temperature control effect of pouch lithium-ion battery based on numerical simulation. Based on the volume change characteristics of stearic acid in the phase transformation process of organic phase change material, the device provides passive drive for the mechanical thermal switch, which can quickly dissipate heat when the battery operating temperature is high, and keep the battery warm in time when the operating temperature is low. The numerical simulation results show that compared with the battery without thermal management system, the final temperature of the battery at the end of the 4 C high-rate discharge is reduced by 22.46 °C, and the temperature control of the phase change thermal switch extends the temperature management time of the battery by 390 s when the external ambient temperature is −20 °C, which has excellent temperature control characteristics.
conclusion
1) Through the comparative analysis of the filling amount of phase change materials in the thermal management device, it is found that the temperature management effect of the thermal management system is not good when the filling amount is small, and the switching ratio of the thermal switch will be reduced when the filling amount is large, and the temperature control effect of the thermal switch will be weakened. When the filling amount is 75%, it can meet the needs of the lightweight thermal management system and the effective temperature control of the battery at the same time.
2) For batteries without thermal management system, when the battery is charged and discharged at a high rate, the battery temperature exceeds the normal working range after the charge and discharge is completed. For the battery thermal management system using phase change material coupled thermal switch, the phase change latent heat and thermal switch provide double temperature protection for the battery, so the temperature of the battery is still in the normal working temperature range when charging and discharging at high rate, and has good temperature control performance.
3) Under low temperature conditions, the heat loss of the battery without thermal management system is faster, while for the temperature control system with PCM coupled thermal switch, when the battery temperature is reduced to near the melting point of the PCM, the PCM solidifies and releases the heat accumulated in the process of battery heating to the battery, providing heat to the battery continuously, thus effectively prolonging the time when the battery is in the normal temperature range.
4) Taking 75% filling volume as an example, the temperature control and regulation performance of the thermal switch was analyzed. The equivalent thermal resistance of the thermal switch when disconnected/closed is 0.016 and 0.18 m2⋅K/W, respectively, and the switching ratio reaches 11.25:1, so it has a significant temperature regulation effect.
