A Liquid Cooling System for Thermal Management
of Lithium-ion Battery Packs
The development of electric vehicles has accelerated significantly in recent years due to growing concerns over fossil fuel consumption and tailpipe carbon emissions. Lithium-ion batteries are currently the most widely used power source for electric vehicles due to their high energy density, low self-discharge rate, low maintenance requirements, long cycle life, light weight, and compact structure. However, the performance of Li-ion batteries is greatly affected by the operating temperature. The ideal operating temperature range for lithium-ion batteries is 25 to 40°C, and the maximum temperature difference between different batteries is less than 5°C. Working in a low or high temperature environment will lead to battery performance degradation, shortened life, and even thermal runaway. Therefore, an excellent battery thermal management system (BTMS) is very necessary to ensure the safe and efficient operation of lithium-ion batteries.
According to different cooling strategies, BTMS can be divided into passive cooling system, active cooling system and hybrid system combining passive and active. In passive cooling systems, there is no additional power consumption, but they also cannot control the cooling system to change the cooling rate. Implement special materials or heat dissipation structures on the surface of lithium-ion batteries to achieve high heat transfer capabilities between the battery and the external environment. Typical examples include natural air convection, phase change materials (PCMs) and heat pipes.
Passive air cooling has low cooling capacity and is not suitable for cooling high energy density Li-ion batteries. PCMs are capable of storing and releasing large amounts of energy during thawing, and have received increasing attention in recent years. The main advantages of incorporating PCM into BTMS are good cell temperature uniformity and flexible geometry. However, the low thermal conductivity of PCM hinders the heat dissipation rate of the battery, which poses serious hidden dangers under high-rate charge-discharge conditions. Therefore, it is very important to develop a battery thermal management system for new energy electric vehicles with excellent heat dissipation performance.
