Experimental Research on Lithium-Ion Batteries Based on Immersion Cooling
In recent years, with the widespread application of lithium-ion batteries in electric vehicles and energy storage systems, battery thermal management technology has become a hot topic of research. Immersion cooling, as an efficient thermal management method, addresses the heat dissipation issues of batteries under high-rate charging and discharging and thermal runaway conditions by directly immersing the batteries in a coolant. The following is a summary of the latest research progress on experimental studies of lithium-ion batteries based on immersion cooling:
1. Single-Phase Immersion Cooling Technology
Single-phase immersion cooling technology (SLIC) has attracted widespread attention due to its simple system structure and broad application scope. Research indicates that SLIC can significantly reduce the peak temperature of battery modules and effectively suppress the propagation of thermal runaway. For example:
Mineral Oil-Based Cooling: Patil et al. proposed a mineral oil-based immersion cooling technology, developing an electrochemical-thermal model of the battery using a multi-scale multi-domain (MSMD) approach. The results showed that compared to indirect cooling methods, immersion cooling reduced the module's peak temperature by 9.3% during 5C discharge.
Transformer Oil-Based Cooling: Wang et al. designed an immersion cooling system based on transformer oil. Experimental data indicated that at a cooling liquid flow rate of 0.8 L/min, the system demonstrated excellent cooling capability during 2C discharge.
Moreover, SLIC also shows significant advantages in terms of the volumetric integration ratio of battery modules and temperature uniformity. For example, the volumetric integration ratio of a direct liquid cooling system is 1.5 times that of an indirect cooling system, while the highest temperature increase in the module is only 20% to 30% of that in the indirect cooling system.
2. Two-Phase Immersion Cooling Technology
Two-phase immersion cooling technology, which utilizes the latent heat of phase change of the coolant, further enhances cooling capability. Research shows that two-phase flow cooling systems can significantly improve the uniformity of module temperature. For example:
HFE-7000 Two-Phase Flow Cooling: Wang et al. proposed a two-phase flow cooling system based on HFE-7000, describing the gas-liquid flow using a two-phase Euler-Euler hybrid model. The results indicated that the boiling heat transfer of two-phase HFE-7000 significantly improved the uniformity of module temperature.
Intermittent Flow Boiling Cooling: Wu et al. designed an intermittent flow boiling cooling method for pouch batteries. During 2C discharge, the peak temperature and temperature difference of the battery were limited to below 36°C and 2°C, respectively, demonstrating excellent cooling performance while significantly reducing the energy consumption of the pump.
3. Application of New Coolants and Composite Materials
In addition to traditional coolants, researchers have explored the application of new coolants and composite materials to further enhance cooling efficiency and safety. For example:
Highly Conductive Composite Materials: A study developed a battery cooling design based on highly conductive phase-change composite materials (GF_PW), encapsulated with 3D-printed polyethylene-boron nitride layers, exhibiting excellent thermal performance with a thermal conductivity between 4.5 and 4.6 W/m.
Novec 649 Coolant: Zhou et al. combined a heat pipe with an immersion cooling system using Novec 649 coolant, which has good dielectric properties. The study showed that the peak temperature and temperature difference of the battery module were limited to below 47°C and 2.1°C, respectively.
4. Thermal Runaway Suppression and Safety Performance
Immersion cooling technology not only effectively dissipates heat but also significantly suppresses thermal runaway. For example:
Thermal Runaway Behavior in 340 Ah Lithium Iron Phosphate Batteries: A study analyzed the thermal runaway behavior of 340 Ah lithium iron phosphate batteries under thermal and mechanical abuse conditions. By using fire blankets and bund irrigation systems, thermal runaway was successfully suppressed, the battery was rapidly cooled, and vehicle damage was minimized.
5. Experimental Research and Optimization Design
Experimental research and optimization design are key to the development of immersion cooling technology. For example:
Coolant Flow and Temperature Relationship: Experiments have shown that the flow rate and temperature of the coolant significantly affect the heat dissipation performance of the battery. By optimizing the flow rate and temperature of the coolant, cooling efficiency can be further improved.
Cooling System Design: Research has also explored issues related to cooling system design, such as active vs. passive cooling, liquid vs. air cooling, and the relative needs of cooling and heating systems.
Conclusion
Immersion cooling technology has demonstrated significant advantages in the thermal management of lithium-ion batteries, especially in high-rate charging and discharging and thermal runaway suppression. Future research directions may include the development of more efficient coolants, optimization of cooling system design, and further reduction of energy consumption. With continuous technological advancements, immersion cooling is expected to become an important solution for lithium-ion battery thermal management.
