Comparison of cooling methods for lithium ion battery pack heat dissipation: air cooling vs. liquid cooling vs. phase change material cooling vs. hybrid cooling

In the field of lithium ion battery technology, especially for power and energy storage batteries (e.g., batteries in containerized energy storage systems), the uniformity of the temperature inside the battery module is a key factor in the overall performance. Significant temperature differences between battery modules can exacerbate inconsistencies in internal resistance and capacity. Over time, this can lead to over-charge or over-discharge of certain battery cells, which can affect battery life cycle and performance and may pose a safety hazard. Therefore, maintaining an optimal operating temperature is critical to the efficient operation of the lithium ion battery. Battery pack heat dissipation, also called thermal management cooling technology plays a key role in this regard. It involves the transfer of internal heat to the external environment via a cooling medium, thereby reducing the internal temperature. This process is particularly important for lithium-ion batteries, which are highly sensitive to temperature changes. Excessive heat can trigger adverse reactions, such as solid electrolyte interface film (SEI film) decomposition inside the battery, which can seriously affect the service life of the battery. Therefore, an effective battery heat dissipation system is important for improving the overall performance of the battery pack.

At present, the common lithium ion battery pack heat dissipation methods are: air cooling, liquid cooling, phase change material cooling and hybrid cooling. Here we will take a detailed look at these types of heat dissipation.

1.  Air cooling

Air cooling, mainly using air as the medium for heat exchange, cools down the heated lithium-ion battery pack through the circulation of air. This is a common method of heat dissipation for lithium-ion battery packs, which is favoured for its simplicity and cost-effectiveness.

a. Principle

Air cooling of lithium-ion batteries is achieved by two main methods:

Natural Convection Cooling: This method utilises natural air flow for heat dissipation purposes. It is a passive system where ambient air circulates around the battery pack, absorbing and carrying away the heat generated by the battery.

Forced Convection Cooling: Compared with natural convection, forced convection cooling uses fans or specially designed air ducts to form a corresponding airflow in a specific space for the purpose of heat dissipation.

The difference between the two is that the air flows at different speeds, and it is common in design to compare the cooling effect by comparing different air flow speeds. Different air outlet design will lead to different distribution of velocity field and temperature field.

b. Appliance

Air cooling efficiency is greatly influenced by the design of the airflow path. For example, having inlets and outlets at each end of the battery pack can promote a more uniform air path, thereby effectively cooling the entire battery pack.

Adjusting the spacing between battery cells promotes optimal airflow and ensures even cooling of each battery cell. Thermally conductive materials such as silicone pads can also be used on the top and bottom of the batteries. These silicone pads help to conduct heat away from areas that are less exposed to airflow, thus improving overall cooling efficiency.

In colder climates, the air cooling system may include heating elements to preheat the batteries to ensure they operate in the optimal temperature range. This ensures that batteries do not perform poorly due to cold temperatures.

c. Advantages and disadvantages

Advantages: The simplicity of the air-cooled design makes it not only easy to implement, but also lightweight and easy to maintain. This simplicity saves costs as fewer complex components are required. It is a widely applicable and non-polluting method.

Disadvantages: However, air cooling has a limited cooling capacity, low heat transfer coefficient and is susceptible to ambient conditions. Reduced reliability in overheating or overcooling conditions. Less effective in managing high heat loads.

2. Liquid cooling

Liquid cooling refers to the use of liquid cooling media such as water, mineral oil, glycol, etc. for cooling. It provides better heat exchange capacity compared to air cooling.

a. Principle

The principle of liquid cooling is to circulate the coolant in the system in direct or indirect contact with the battery cells, so as to take away the heat generated by the battery to dissipate heat. It is usually divided into direct contact liquid cooling and indirect contact liquid cooling.

Direct contact liquid cooling: It refers to submerging the battery directly in the coolant, so that the coolant is in direct contact with the battery pack to achieve the purpose of heat dissipation.

Indirect contact liquid cooling: It refers to the installation of cold plates and flow channels around the battery or between the battery cells. The coolant flows through these cold plate channels and takes away the heat generated by the battery for heat dissipation.

b. Appliance

In practice, liquid cooling varies in complexity. Simple systems may involve simple channel designs, while more advanced systems may use complex layouts to ensure even temperature distribution across all battery cells. This may include optimising the cold plate material, its position relative to the battery and the choice of coolant. For example, in some electric vehicles, coolant flows through channels (similar to a snake) that surround each battery cell to maximise heat absorption.

c. Advantages and disadvantages

Advantages: As the coolant has higher heat capacity and thermal conductivity than air, the heat exchange process of liquid cooling is more direct, efficient and closed, so its temperature control, temperature equalisation ability and heat dissipation effect are better than air cooling. Moreover, it is highly flexible and can be designed and adjusted according to the specific conditions of the battery system in terms of cold plate, pipeline and coolant. And the external environment has little influence, and it is still effective under various environmental conditions.

Disadvantages: Liquid cooling requires the selection of a suitable coolant, the addition of additional coolant circulation devices, and a higher requirement for its sealing to prevent the risk of leakage. Therefore he is structurally complex, which will make it more difficult to maintain at a later stage, and may also increase the size and weight of the overall battery pack, with a higher manufacturing cost than air cooling.

3. Phase change material cooling

a.Principle

Phase change material cooling is to use the phase change material as a cooling medium, using in the phase change reaction process the physical state changes to absorb or release the heat of the battery.

Phase change materials are classified as inorganic, organic and composite materials. Inorganic phase change materials, such as graphite and water of crystallisation, have a high enthalpy of phase change, high thermal conductivity, but also high subcooling and poor thermal stability. Organic phase change materials, such as paraffin and acetic acid, are non-corrosive, have low subcooling and are chemically stable. Composite phase change materials are organic and inorganic materials that are used together to provide better thermal management of lithium-ion batteries.

b. Appliance

Phase change materials applied in lithium-ion battery packs usually require: high material heat density, high latent heat; high thermal conductivity, rapid heat absorption and heat release process. Good stability, not easy to decompose as well as side reactions with the surrounding materials, long life cycle, will not cause adverse effects on the system.

c. Advantages and disadvantages

Advantages: Better temperature control effect and homogeneous temperature capability, significant thermal conductivity and heat absorption of phase change materials, compact structure, high space utilisation.

Disadvantages: Effective phase change cooling requires precise temperature control. Phase change materials can be expensive and may need to be replaced periodically.

In summary, while phase change cooling offers advantages in terms of passive cooling and temperature stabilisation, it requires precise temperature management. It is often used in combination with other cooling methods to help provide a more comprehensive thermal management solution for lithium-ion batteries, especially in applications where space is limited and passive cooling is favoured.

4. Hybrid cooling

a.Principle

Hybrid cooling of lithium-ion batteries combines two or more cooling methods to take advantage of the benefits of each. This cooling strategy addresses the limitations of a single cooling method by integrating the advantages of a single cooling method to achieve more efficient thermal management.

Common combinations include air cooling and phase change material cooling, liquid cooling and phase change material cooling, etc.

b. Appliance

In practice, hybrid cooling systems can be customised to meet the specific thermal management needs of a battery pack. They can be designed to adapt to different operating conditions and can be optimised to handle different thermal loads efficiently. This adaptability makes hybrid cooling an attractive option for a variety of applications, especially where battery performance and safety are critical.

c. Advantages and disadvantages

Advantages: By combining different cooling methods, the shortcomings that exist in a single thermal cooling method are solved. Various heat loads can be managed more effectively, making it suitable for various applications. And with its design flexibility, it can also be better adapted to various battery configurations and space constraints.

Disadvantages: Integration of multiple cooling technologies can lead to higher complexity and costs compared to single-method systems. Achieving the optimal balance and integration of different cooling technologies also requires careful design and engineering. Over time, the complexity of a hybrid system can lead to higher maintenance requirements.

Hybrid cooling of lithium-ion batteries provides a complex solution that combines the benefits of various cooling methods for enhanced thermal management. These systems provide superior cooling performance and versatility while adding complexity and cost. Their ability to provide customised thermal regulation makes them particularly well suited to advanced battery applications where safety, efficiency and lifetime are critical.

In summary, the choice of lithium-ion battery cooling method depends on a delicate balance of efficiency, cost, complexity and application-specific requirements. Air cooling is simple and cost-effective, but has limited cooling efficiency, making it suitable for less demanding applications or in combination with other methods. Liquid cooling excels in demanding applications due to its superior heat transfer capabilities, which are often enhanced by integration with phase change material cooling to improve temperature uniformity. Hybrid cooling incorporates a variety of cooling technologies to provide better thermal management, especially in high-density and high-performance applications. The development of this diverse range of cooling technologies paves the way for more efficient, reliable and adaptable battery systems in the future.

As a professional manufacturer of lithium-ion battery modules and battery packs, lythbattery has a professional technical team, mechanised production lines and product testing equipment. If you have customised needs for lithium-ion battery modules and battery packs, please feel free to contact us. We will solve your problems and meet your needs at the first time!

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