基于相变材料的锂离子电池热管理性能

锂离子电池（lithium-ion battery，LIB）作为目前应用最广泛的储能电池之一，在电动汽车等行业发挥着至关重要的作用。电池的温度是影响LIB性能及安全性的重要因素，因此电池热管理（battery thermal management，BTM）至关重要。目前，利用相变材料（phase change material，PCM）进行相变冷却的热管理方式因其潜热高、不需消耗额外能量的优点已成为一种很有前途的方法。本文针对8节并联18650LIB的电池组性能进行了数值模拟及实验研究，探究了石蜡基复合相变材料（composite phase change material，CPCM）物性参数（包括热导率、熔点、相变潜热和材料厚度）对本文设计的电池组热管理性能的影响。结果表明，纯石蜡用于BTM可将3C放电下的电池最高温度降低28.0%，向石蜡中添加膨胀石墨后可使CPCM的热管理性能进一步提升，CPCM的热导率为2.0W/(m·K)时可将3C放电下的电池最高温度进一步降低5.42℃，继续增大CPCM热导率对热管理性能的提升较小。在综合考虑电池组的最高温度和温度均匀性的情况下，为得到在本文所设计的锂离子电池组最佳热管理性能，CPCM的热导率为2.0W/(m·K)、熔点应在36~38℃之间、相变潜热在212J/g左右、CPCM的厚度为4mm时最优。

Thermal management performance of lithium-ion battery based on phase change materials

As one of the most widely used power batteries, lithium-ion battery (LIB) plays an important role in electric vehicles and other industries. Temperature is an important factor affecting LIB performance and safety, and thus battery thermal management (BTM) is very important. At present, phase change material (PCM) has become a research hotspot because of high latent heat and no additional power consumption. In this study, the performance of 8 parallel 18650 LIB pack was numerically simulated, and the temperature variation characteristics of LIB was experimentally studied. The LIB heat generation model was established, and the temperature change of single LIB during the discharge process was tested. The influence of thermophysical parameters of composite phase change material (CPCM), such as thermal conductivity, melting point, latent heat and thickness, on the BTM characteristics of LIB pack designed in this paper were studied. The results showed that pure paraffin used in BTM can reduce the maximum battery temperature under 3C discharge by 28.0%. Adding expanded graphite to paraffin can further improve the thermal management performance of CPCM. When the thermal conductivity of CPCM was 2.0W/(m·K), the maximum temperature of battery under 3C discharge can be further reduced by 5.42℃, and the increase of the thermal conductivity of CPCM had little effect on the improvement of thermal management performance. Considering the maximum temperature and temperature uniformity of the battery pack, in order to obtain the best thermal management performance of the lithium-ion battery pack designed in this paper, the thermal conductivity of CPCM should be 2.0W/(m·K), the melting point of CPCM should be between 36—38℃, the latent heat of phase transition was about 212J/g, and the thickness of CPCM was 4mm.