Comparison Of Four Major Cooling Technologies For Battery Thermal Management, There’s Nothing New Under The Sun

With the rapid advancement of technology, lithium-ion batteries are becoming more and more prevalent in our daily lives, from smartphones to electric cars, they have permeated every aspect of our lives. But just as we enjoy the convenience of batteries, the management of the temperature inside them is also a crucial topic. The temperature of a battery not only affects its performance and life but also the safety of the user. That’s why battery thermal management technology has become so critical.

Follow the TKT team as we take an in-depth look at the four main battery thermal management technologies: air cooling, liquid cooling, phase change material cooling, and thermoelectric cooling.

Three Technologies for Battery Thermal Management

In the current technological era, lithium-ion batteries are becoming the energy source of choice for cell phones, electric vehicles, and energy storage plants due to their high energy density and long life. As an example, the Tesla Roadster electric car in Figure 1, which is equipped with 6,831 lithium-ion cells of the 18650 model, represents an innovative application of lithium-ion batteries in the automotive field and has also brought the public’s attention to the thermal management of batteries.

Batteries may have uneven or insufficient power utilization when in use, so they are often equipped with a battery management system (BMS) to monitor and optimize the battery’s operating status. However, as technology continues to advance, the thermal management of batteries (especially temperature control) is gradually gaining attention. This is because too high or too low a battery temperature can lead to degradation of battery performance and even safety hazards.

An efficient Battery Thermal Management System (BTMS) is indispensable to ensure optimal performance and safety. It ensures that the battery temperature is always in the ideal range and that temperature differences between cells are minimized.

It is important to note that lithium-ion batteries are very sensitive to temperature. For example, when the temperature is too low, the performance of the battery will be affected, and specific types of batteries, such as lithium iron phosphate batteries, will see their conductivity drop dramatically at low temperatures. At high temperatures, the battery may suffer thermal runaway or even cause explosions and other safety incidents.

Cooling technology plays a key role in thermal management by ensuring that battery temperatures are not too high, thereby protecting the battery and ensuring its safe operation. Although we have several battery cooling solutions, they need to be optimized in terms of heat dissipation, temperature equalization, and cost.

To this end, we have conducted an in-depth discussion of several mainstream battery thermal management technologies, including air cooling, liquid cooling, phase change material cooling, and thermoelectric cooling, analyzed their respective advantages and disadvantages, and predicted possible future trends.

Lithium-ion battery thermal management technology

Lithium-ion batteries occupy an important position in the global power and consumer battery market, so their thermal management technologies have been receiving a great deal of attention in the industry. These technologies have evolved from simple natural air cooling to composite cooling, each with its characteristics and challenges. Below, TKT HVAC’s expert technicians provide a detailed overview of the various cooling technologies.

1. Air Cooling

Air cooling can be divided into passive natural cooling and active forced cooling. Both types of cooling are realized through the airflow to take away the heat generated by the battery. The advantages are simple structure, low cost, environmental protection, and no pollution.

Natural cooling: This is a passive cooling technology that only requires a well-designed cooling duct. For example, the early Nissan Leaf electric car adopted this cooling method. However, this method is difficult to meet the efficient cooling needs of power batteries and may affect the life of the battery.

Forced air cooling: Compared to natural cooling, this technology enhances airflow by adding fans and other equipment to improve the cooling effect. However, this also means an increase in noise and energy consumption. In addition, the cooling effect can be further improved by adjusting the shape of the airflow channels.

In electric flight equipment, air cooling technology is still preferred due to its lightweight and low energy consumption. For example, certain electric drones and electric flying cars use natural air cooling technology. Especially for weight-oriented electric flight equipment, properly designed air ducts can also improve its heat dissipation effect.

In summary, air cooling technology still has wide potential and value in specific applications due to its simplicity, economy, and environmental friendliness.

2. Liquid cooling technology

Liquid cooling uses a coolant to exchange heat in the battery, which can dissipate heat efficiently and rapidly. This technology is divided into direct liquid cooling and indirect liquid cooling. In direct liquid cooling, the coolant is in direct contact with the battery, such as immersion liquid cooling. Indirect liquid cooling, on the other hand, achieves its cooling effect through specific components, such as cooling plates.

2.1 Cooling Plate Liquid Cooling

Compared with air cooling, cooling plate liquid cooling technology is more efficient, and the cooling plate is mostly aluminum or aluminum alloy, which is relatively low cost. The main research direction is to optimize the structure and fluid flow characteristics of the cooling plate to simplify the manufacturing process and enhance its effectiveness.

Recent research has focused on the design of coolant channels and the direction of coolant flow. For example, some experts have designed a new type of liquid cooling plate based on serpentine flow channels. This new design can greatly improve the cooling efficiency under specific conditions. Some experts have also designed a honeycomb structure cooling plate based on square batteries, and this design improves heat dissipation by increasing cooling channels. All of these studies have pointed out that reasonable coolant channel design and flow direction are critical for temperature uniformity. Overall, the cooling plate liquid cooling technology is quite mature and is widely used in a variety of electric devices.

Application Examples

Cooling plate liquid cooling technology has been widely used in energy storage power stations and electric vehicles. A company’s cooling plate liquid cooling products and related patents demonstrate its effect in practical applications. The serpentine-shaped cooling plate inside Tesla’s 4680CTC battery pack also adopts this technology to increase the contact area and improve the cooling effect.

Overall, cooling plate liquid cooling technology is very effective for most application scenarios. Its main materials, such as copper and aluminum, have good thermal conductivity at moderate costs, making it ideal for use in electric vehicles or other devices with high cooling needs. In practice, to ensure high-quality cooling, it is necessary to design suitable cooling channels and select appropriate materials according to the battery type and structure.

2.2 Submerged liquid cooling

Submerged liquid cooling technology is to completely immerse the battery and other heat-generating parts in the cooling liquid. Compared to traditional air cooling, this technology reduces noise and energy consumption, and also better controls the temperature of the battery. Despite the excellent results of this technology, its main drawback is the relatively large weight and size of the system, which limits its application in electric vehicles. However, it is ideal for stationary energy storage plants.

Immersion liquid cooling uses mainly insulating oils and fluorinated fluids as coolants, albeit at a higher cost. However, studies have demonstrated that this cooling technology ensures that the average temperature rise of the batteries does not exceed 5°C, while the temperature difference between the batteries is only 2°C. This helps to improve the energy storage plant. This helps to improve the service life and safety of the energy storage plant.

The latest research points out that immersion liquid cooling can greatly improve cooling efficiency. For example, experiments have shown that increasing the submergence depth improves the cooling effect, and the maximum temperature and temperature difference of the battery are reduced by 32.4% and 75.3%, respectively. In addition, it is also critical to choose the appropriate coolant flow mode and speed, and the correct choice can lead to better control of the temperature and temperature difference of the battery.

While immersion liquid cooling technology has been widely used in energy storage power plants, its use in electric vehicles is still limited by cost and size. However, it may still be possible for certain high-end models or models with special cooling needs.

CONCLUSION: Immersion liquid cooling technology has great potential for battery cooling, especially for large installations such as energy storage plants. However, the widespread adoption of electric vehicles still needs to address issues such as cost, volume, and design challenges.

3. Phase change material cooling technology

Phase change material (PCM)-based battery thermal management technology is an innovative approach that maintains the battery at an optimal temperature by utilizing the thermal storage and release properties of PCM. The advantages of this approach are multiple: it requires no additional energy, there are no moving parts, it is low maintenance, and it does a good job of ensuring a uniform battery temperature.

Currently, the PCM materials commonly used in thermal management are:
Organic materials such as paraffins, alkanes, and organic acids.
Inorganic materials such as aqueous solutions, salt hydrates, and molten salts.
Eutectic materials.

However, PCM itself does not have a high thermal conductivity, so other materials such as copper foam, expanded graphite, and nanoparticles are usually added to improve its thermal conductivity. This also solves some of the physical problems of PCM, such as fluidity after a phase change.

To understand this more intuitively, we can refer to some recent studies. For example, some experts have created a composite phase change material consisting of lauric acid and paraffin wax combined with expanded graphite, and this material succeeded in lowering the maximum temperature of a certain battery to 42.39°C. Other studies have also shown that the cooling effect of PCM can be further enhanced by combining it with other cooling methods, such as air cooling.

This technology is not just limited to the lab. A PCM cooling system has been used in a certain electric airplane. Although PCM has the advantage of being lightweight, its high cost limits its wide application.

In practice, PCM is often combined with other cooling methods to improve its effectiveness. For example, adding fins can improve cooling efficiency, while certain fin structures can be used as supports to prevent PCM flow. Of course, other factors need to be considered when selecting PCM, such as its melting temperature, safety, and thickness.

In summary, although PCM shows great potential in battery thermal management, further research and optimization are still needed to ensure its efficiency and safety in practical applications.

4. Thermoelectric cooling technology

Thermoelectric cooling is an advanced active cooling technology with a core based on the Peltier effect. In short, when an electric current passes through a particular material, it absorbs heat on one side and releases it on the other, thus achieving a cooling effect. The main advantages of this technology include no need for refrigerants, low energy consumption, fast start-up, good stability, low noise, and no moving parts. However, challenges are also apparent, such as inefficient cooling and difficulties in manufacturing large devices.

Researchers have conducted numerous experiments to optimize this technology for use in battery cooling systems. For example, one expert designed a system combining dual silica cooling plates with copper mesh and air cooling and found that the thickness of the silica cooling plates was related to the temperature performance of the battery, determining that 1.5mm was the optimal thickness. Another study combined thermoelectric cooling with liquid cooling, and experiments proved that this combination can effectively improve the cooling effect.

However, despite these positive research developments, thermoelectric cooling technology is currently mainly applicable to small electronic devices because of its limited cooling effect and technical difficulties in large-area applications.

In summary, the combination of thermoelectric cooling technology with other cooling technologies is the key to its commercialization. For example, the combination of liquid cooling allows for faster cooling and improved temperature uniformity. In addition, the manufacturing process of TEC still needs to be further studied and optimized to reduce the cost.

Conclusion and Outlook

Thermal management technology for Li-ion batteries plays a crucial role in their wide range of applications. In the future, efficient, environmentally friendly, and cost-effective solutions will be the direction of technology development. With the help of current simulation software, we have a solid foundation to further refine these technologies. The following conclusions and perspectives are drawn for the various cooling technologies discussed in this paper:

Air cooling: although air cooling is a classical technology, its application in the field of high-power lithium batteries has encountered limitations. It is expected that more efficient liquid cooling technologies will gradually replace air cooling in future large-scale energy storage plants and power battery applications. However, for small electronic devices and simple power tools, air cooling still has its application space due to its cost-effectiveness and simplicity.

Liquid cooling: There are two types of liquid cooling technology, direct and indirect. Cooling plate technology is well-established and widely used in energy storage plants and electric vehicles. Submerged liquid cooling shows better cooling results, but is more complex to maintain. It is expected that submerged technology will be used more often in large-scale energy storage plants and high-end electric vehicles.

Phase change material cooling (PCM): PCM has excellent heat absorption and storage capabilities, but due to its inherent thermal conductivity limitations, it usually requires the incorporation of high-cost reinforcement materials, which somewhat limits its popularity in large battery applications.

Thermoelectric Cooling: As an emerging technology, thermoelectric cooling has been commercially used in certain small devices, such as cell phones. However, its cooling efficiency is relatively low and needs to be used in combination with other technologies. Future development should focus on improving cooling efficiency and reducing costs.

In summary, there is no one-size-fits-all cooling solution. It appears that the main trend in the future will be to combine a variety of cooling technologies to select the most appropriate cooling method for a specific application and to meet a variety of needs.