Battery heat dissipation structure based on phase change material and packaging method

Abstract

The invention discloses a battery heat dissipation structure based on a phase-change material and a packaging method, the battery heat dissipation structure comprises a battery cell unit, a heat dissipation partition plate, a shell, a heat dissipation material and an insulating plate, the heat dissipation material is filled in a gap between the battery cell unit and the heat dissipation partition plate and a gap between the battery cell unit and the shell, the heat dissipation material adopts the phase-change material, the phase-change material has high latent heat of phase change, and the phase-change material has high latent heat of phase change. And the phase change temperature of the phase change material is 5-10 DEG C lower than the maximum working temperature of the battery cell. The internal gaps of the battery are filled with the phase-change material, and the phase-change latent heat of the phase-change material after being heated can quickly absorb the heat generated by the battery cell, so that the thermal response time is greatly shortened, and the battery cell can be effectively prevented from being overheated.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical batteries, and in particular relates to a battery heat dissipation structure and packaging method based on phase change materials. Background Art

[0002] In order to meet the continuous improvement of equipment performance, the high-rate discharge performance of batteries has received increasing attention. In order to improve the high-rate discharge performance of batteries, many units and scientific researchers have carried out in-depth research on electrode materials, electrode preparation processes, electrolyte formulations, diaphragm materials, etc. In addition to the fact that the output voltage of the battery is lower than the requirement due to its own electrochemical polarization, the high-rate discharge capacity of the battery is also affected by the fact that the battery temperature exceeds the safety requirements due to the large amount of heat generated during high-rate discharge. Therefore, it is necessary to carry out thermal design for the battery pack to ensure that the battery is always within a reasonable temperature range.

[0003] The main sources of heat generation in high-rate discharge of batteries are polarization heat generation inside the battery cell and current collection heat generation. Among them, the current collection heat generation is mainly concentrated at the pole ear. Since it is outside the battery cell, it is generally cooled by air cooling, liquid cooling, etc. based on the principles of convection heat transfer and heat conduction. The polarization heat generation inside the battery cell mainly comes from the inside of the battery cell, and the heat can only be transferred to the outer surface of the battery cell in the form of heat conduction, and then dissipated by heat conduction or convection heat transfer. However, for the battery, the battery cells inside are in a tightly arranged state (especially the soft-pack battery group), and the heat dissipation of the outer surface of each battery cell will be affected by the adjacent battery cells, and will not be lower than the heat dissipation. For this reason, a grid layout structure is generally adopted in the battery structure design. That is, a heat dissipation partition is set every few battery cells in the middle of the stacked multiple battery cells. The heat dissipation partition is generally a metal material with high thermal conductivity (such as an aluminum alloy plate) or a composite material plate with good thermal conductivity (such as a thermally conductive silicone pad or a graphite plate, etc.). The heat dissipation partition is used to transfer the heat inside the battery cell to the outside of the battery pack. Although the heat dissipation baffle has good thermal conductivity, it is limited by the assembly operation.

[0004] Conventional battery packs mainly consist of a shell, a battery pack, a control circuit, and input and output interfaces. Among them, the battery pack is composed of a single cell, a current collector, a structural component, and an insulating material. In order to ensure that the cells in the battery pack have good heat dissipation performance, a thermally conductive potting glue is generally used to fill the gap between the battery pack and the shell to achieve the purpose of improving heat dissipation. This heat dissipation method is widely used in the design of cylindrical cells, square cells, and soft-pack cells.

[0005] In actual engineering applications, we found that the heat dissipation of thermal conductive potting glue also has certain limitations:

[0006] (1) Slow thermal response. The heat dissipation of thermally conductive potting glue is actually achieved based on heat conduction under temperature gradient. Only when the temperature gradient reaches a certain level can the heat dissipation power be increased, and there is a certain temperature response time. Especially when the thickness of the potting glue is large, this temperature response has a long lag phenomenon.

[0007] (2) Not suitable for battery systems with volume shrinkage. Thermally conductive potting glue is generally used to pot the battery under the condition of minimum volume. When the battery expands (or remains unchanged) due to charging or discharging, the thermally conductive potting glue can be compressed; when the battery volume recovers, the elastic potting glue can return to its original volume and compensate for the volume change. However, for battery systems with volume shrinkage characteristics (such as lithium metal oxide batteries, which can shrink by up to 10% during discharge), this potting glue cannot compensate for the shrinkage of the battery volume, which will cause the potting glue to separate from the single battery cell. Once the potting glue separates from the single battery cell, the heat transfer between the two will be significantly reduced, resulting in poor heat dissipation. Summary of the invention

[0008] In view of the problems existing in the prior art, the present invention provides a battery heat dissipation structure and packaging method based on phase change materials. On the basis of the heat dissipation design of thermally conductive potting glue, phase change materials are used to replace thermally conductive potting glue, and the phase change latent heat of the phase change material is used to quickly absorb the heat on the surface of the battery cell, significantly shortening the temperature response time. At the same time, the flow characteristics of the phase change material after the phase change are used to compensate for the volume change of the battery cell, and the phase change material is always in good contact with the surface of the battery cell to ensure that the heat transfer performance remains unchanged. Combined with practical engineering applications, the present invention also proposes a method for encapsulating phase change materials in a small space in a battery pack by using constant temperature heating measures.

[0009] The present invention is implemented as follows: a battery heat dissipation structure based on phase change material includes a battery cell unit, a heat dissipation partition, a shell, a heat dissipation material, and an insulating plate. The heat dissipation material is filled in the pores between the battery cell unit and the heat dissipation partition, and between the battery cell unit and the shell. The heat dissipation material is a phase change material. The phase change material has a high phase change latent heat and absorbs heat from the surface of the battery cell. The phase change temperature of the phase change material is 5°C-10°C lower than the maximum operating temperature of the battery cell.

[0010] The main component of the phase change material is a waxy organic phase change material.

[0011] The phase change material has insulating properties.

[0012] The heat dissipation baffle and the shell have thermal conductivity, and are made of metal materials such as aluminum alloy, steel, and magnesium alloy, or non-metal materials such as plastic, rubber, epoxy resin, and carbon fiber with thermal conductivity.

[0013] The heat dissipation baffle and the shell are structurally connected in one body or separately; the exterior of the shell has a structure and characteristics for dissipating heat to the external environment, including fins, air cooling, and water cooling structures; the shell is a semi-open structure, and the lower part has a sealing structure to ensure that the phase change material in a molten state will not leak; the upper part has holes or channels for filling phase change material.

[0014] The battery cell unit is a single battery cell or a combination of single battery cells connected in series and parallel. The single battery cell is in the structural form of a cylindrical battery cell, a square battery cell, or a soft-pack battery cell.

[0015] The packaging method of the battery heat dissipation structure based on phase change material places the shell containing the battery cell unit and the phase change material in a high-temperature environment. The temperature of the high-temperature environment is higher than the phase change temperature and not higher than the maximum safe operating temperature of the battery. After the temperature of the battery cell unit and the shell reaches stability and the phase change material melts into liquid, the liquid phase change material is added to the shell to completely encapsulate the battery cell unit.

[0016] The phase change material is added in batches or all at once.

[0017] The packaging environment is a normal pressure environment or a vacuum environment with a certain negative pressure. The pressure of the vacuum environment is greater than the lowest vacuum pressure that the battery can withstand. The high temperature environment is obtained by equipment such as an oven, a blast drying oven, and an oil bath.

[0018] The temperature of the high temperature environment is 3°C-5°C higher than the phase change temperature and 10°C lower than the maximum safe temperature of the battery, and the pressure of the vacuum environment is greater than the lowest vacuum pressure that the battery can withstand, which is -20kPa to -50kPa.

[0019] The advantages and positive effects of the present invention are:

[0020] 1. The present invention uses phase change materials to fill the internal gaps of the battery, and uses the latent heat of the phase change material after being heated to quickly absorb the heat generated by the battery cell, greatly reducing the thermal response time and effectively preventing the battery cell from overheating.

[0021] 2. The present invention utilizes the volume expansion property of the phase change material after the phase change, which can avoid stratification and separation caused by the volume change of the battery cell, and ensure that the battery cell has good heat dissipation conditions.

[0022] 3. The present invention adopts a method of placing the battery and the phase change material together in a high temperature environment, thereby ensuring that the phase change material can be fully encapsulated. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of a single cell;

[0024] Figure 2 is a cross-sectional view of a battery pack filled with phase change material using the method of the present invention;

[0025] Figure 3 yes Figure 2 Top view of the battery pack. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0028] In addition, the terms "first", "second", etc. are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features.

[0029] Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0030] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0031] The electrical devices, controllers, etc. described in the present invention are all conventionally configured, and the electrical connection method is also conventionally connected.

[0032] like Figure 1-3As shown, the battery heat dissipation structure based on phase change material of the present invention includes a battery cell unit 1A, a heat dissipation partition 2a-2, a shell 2, a heat dissipation material, and an insulating plate 3. The heat dissipation material is filled in the pores between the battery cell unit 1A and the heat dissipation partition, and between the battery cell unit 1A and the shell. The heat dissipation material is a phase change material. The phase change material has a high phase change latent heat and absorbs heat from the surface of the battery cell. The phase change temperature of the phase change material is 5°C-10°C lower than the maximum operating temperature of the battery cell.

[0033] The main component of the phase change material is a waxy organic phase change material.

[0034] The phase change material has insulating properties.

[0035] The heat dissipation baffle 2a-2 and the housing 2 have thermal conductivity, and are made of metal materials such as aluminum alloy, steel, and magnesium alloy, or non-metal materials such as plastic, rubber, epoxy resin, and carbon fiber with thermal conductivity.

[0036] The heat dissipation baffle 2a-2 and the outer shell 2 are structurally connected in one body or separately; the outer shell has a structure and characteristics for dissipating heat to the external environment, including fins, air cooling, and water cooling structures; the outer shell 2 is a semi-open structure, and the lower part has a sealing structure to ensure that the phase change material in a molten state will not leak; the upper part has holes or channels for adding phase change material.

[0037] The battery cell unit 1A is a single battery cell 1 or a combination of single battery cells 1 connected in series and in parallel. The single battery cell is in the form of a cylindrical battery cell, a square battery cell, or a soft-pack battery cell.

[0038] The packaging method of the battery heat dissipation structure based on phase change material places the shell containing the battery cell unit and the phase change material in a high-temperature environment. The temperature of the high-temperature environment is higher than the phase change temperature and not higher than the maximum safe operating temperature of the battery. After the temperature of the battery cell unit and the shell reaches stability and the phase change material melts into liquid, the liquid phase change material is added to the shell to completely encapsulate the battery cell unit.

[0039] The phase change material is added in batches or all at once.

[0040] The packaging environment is a normal pressure environment or a vacuum environment with a certain negative pressure. The pressure of the vacuum environment is greater than the lowest vacuum pressure that the battery can withstand. The high temperature environment is obtained by equipment such as an oven, a blast drying oven, and an oil bath.

[0041] The temperature of the high temperature environment is 3°C-5°C higher than the phase change temperature and 10°C lower than the maximum safe temperature of the battery, and the pressure of the vacuum environment is greater than the lowest vacuum pressure that the battery can withstand, which is -20kPa to -50kPa.

[0042] Specifically, the phase change material is filled in the gaps between the single cell and the heat dissipation partition, and between the single cell and the outer shell. When the single cell discharges at a high rate and generates heat, the temperature of its outer surface will rise rapidly. At the same time, because the phase change material tightly wraps the single cell, its temperature will also rise with the increase in the temperature of the outer surface of the single cell. When its temperature reaches or exceeds the phase change temperature of the phase change material, the phase change material will undergo a phase change and release the phase change latent heat, thereby maintaining the temperature of the outer surface of the single cell unchanged.

[0043] The packaging method of the battery heat dissipation structure is mainly to place the battery and the phase change material together in a high temperature environment not lower than the phase change temperature of the phase change material. After the phase change occurs, the phase change material is injected into the pores inside the battery using its own fluidity. After the pores in the battery are completely filled, the battery is restored to normal temperature conditions, and the phase change material returns to a solid state to complete the packaging.

[0044] The phase change material is in a solid or gel state with no fluidity or poor fluidity before the phase change, and has good fluidity after the phase change, and can achieve the sealing of narrow gaps under the action of gravity or vacuum.

[0045] The phase change material has a suitable phase change temperature point, and its temperature value matches the battery operating temperature range and shall not be higher than the battery safety temperature. Furthermore, the phase change temperature of the phase change material is preferably 5°C to 10°C lower than the maximum operating temperature of the battery cell.

[0046] The phase change material has high phase change latent heat and can absorb heat from the surface of the battery core.

[0047] The phase change material is a waxy organic phase change material, or a composite phase change material mainly based on waxy organic phase change and with other organic and inorganic materials added. Further, the phase change material is phase change paraffin wax.

[0048] The phase change material has the characteristic of increasing volume after phase change.

[0049] The phase change material should have good chemical stability and good compatibility with materials such as battery core, housing, and separator. Furthermore, the phase change material may also have good insulation properties.

[0050] The heat dissipation baffle and the shell have good thermal conductivity, and are generally made of metal materials such as aluminum alloy, steel, magnesium alloy, etc., or non-metal materials such as plastic, rubber, epoxy resin, carbon fiber, etc. with thermal conductivity. The heat dissipation baffle and the shell can be connected in one structure or can be separated. Furthermore, the outer shell has a structure and characteristics for good heat dissipation to the external environment, including but not limited to fins, air cooling, water cooling, etc.

[0051] The shell should be a semi-open structure, and its lower part should have a sealing structure to ensure that the phase change material in a molten state will not leak; its upper part should have holes or channels for filling the phase change material.

[0052] The single cell may be a cylindrical cell, a square cell, a soft-pack cell, etc. The single cell has a surface in contact with the phase change material. The single cell may also be a combination of the aforementioned cells in series and parallel in a specific form.

[0053] The temperature of the high temperature environment in the packaging method should not be lower than the phase change temperature of the phase change material, preferably 3°C to 5°C higher than the phase change temperature. The high temperature environment temperature should not be higher than the maximum safe operating temperature of the battery, preferably 10°C lower than the maximum safe temperature of the battery. Further, the high temperature environment can be obtained by equipment including but not limited to ovens, blast drying ovens, oil baths, etc.

[0054] In the packaging method, the phase change material can be added in batches or all at once.

[0055] The packaging environment can be a normal pressure environment or a vacuum environment with a certain negative pressure, so as to facilitate the injection of phase change materials into narrow gaps. Furthermore, the pressure of the vacuum environment should be greater than the lowest vacuum pressure that the battery can withstand, generally -20kPa to -50kPa.

[0056] To further illustrate the content, features and effects of the present invention, a certain soft-pack lithium battery pack (hereinafter referred to as "battery pack") is taken as an example and described in detail as follows:

[0057] Figure 1 , 2 As shown, a certain soft-pack lithium battery pack adopts the form of 2 parallel and 6 series groups, which is mainly composed of a single cell 1, a module shell 2, an insulating plate 3, a phase change material 4, etc. The single cell 1 is a soft-pack battery encapsulated with an aluminum-plastic film, which has a positive electrode ear 1a and a negative electrode ear 1b. Two single cells 1 are connected in parallel to form a cell unit 1A. The module shell 2 includes a shell 2a and an upper cover 2b, and the shell and the upper cover are both made of aluminum alloy and machined. The shell and the upper cover are connected as a whole by fasteners. The lower part of the shell has a sealed bottom plate 2a-1; the partition 2a-2 provided in the shell divides the internal space of the shell into 6 slots. The insulating plate 3 is made of a 1.0 mm thick epoxy plate. A rectangular through hole 3a is opened at the insulating plate corresponding to the pole ear of the cell unit 1A, and the cell unit pole ear can extend to the upper part of the insulating plate through this through hole. The outer dimensions of the insulating plate are smaller than the inner opening dimensions of the housing, so that the insulating plate can be embedded in the housing and a 2 mm gap 3c is reserved between the insulating plate and the inner wall of the housing. Six through holes 3b with a diameter of 6 mm are designed in the middle of the insulating plate.

[0058] The negative electrode tab of the battery cell unit 1A is Figure 3 After bending, it is overlapped with the positive electrode ear of the next battery cell unit and welded together by laser welding. The positive electrode of the first battery cell unit and the negative electrode of the sixth battery cell unit are respectively led out to the outside of the module shell as the positive electrode and negative electrode of the battery pack.

[0059] The phase change material 4 used in the embodiment is phase change paraffin, and its specification is PCM-A-70, which is white particles at room temperature, has a phase change temperature of 70°C, a phase change latent heat of 220 J / g, and a solid density of 0.84 g / cm 3 , liquid density 0.76g / cm 3 , thermal conductivity 0.2W / mK.

[0060] The battery assembly and phase change material potting process in this embodiment is as follows:

[0061] 1. Stack two single batteries together with the positive electrodes facing the positive electrodes and the negative electrodes facing the negative electrodes to form a battery cell. Prepare a total of 6 battery cells.

[0062] 2. Put 6 battery cells Figure 3 Insert the positive and negative poles of the connector into the slots of the outer casing in sequence.

[0063] 3. Cover the top of the battery cell with the insulating plate, and pass the tabs of the battery cell through the corresponding rectangular through holes on the insulating plate. Adjust the position of the insulating plate so that there is a gap of about 2 mm between its edge and the inner wall of the shell.

[0064] 4. Follow Figure 3 Position, stack the positive and negative ears of the battery cell unit together, and weld them into one by laser welding.

[0065] 5. Place the shell containing the battery cell into an oven with the preset temperature of 73°C. At the same time, take an appropriate amount of phase change material and put it into a small beaker and put it into the oven together.

[0066] 6. After standing for about 1 hour, when the temperature of the battery cell and the shell reaches a stable state and the phase change material in the beaker melts into liquid, pour the liquid phase change material in the beaker into the 6mm through hole on the insulating plate until the phase change material overflows from the gap between the insulating plate and the inner wall of the shell. In this way, the six battery cells are completely potted in sequence.

[0067] 7. Take out the encapsulated battery cell unit together with the shell from the oven and place it at room temperature to cool naturally.

[0068] 8. Install the upper cover onto the housing through fasteners. This completes the packaging of the battery pack.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A battery heat dissipation structure based on phase change material, comprising a battery cell unit (1A), a heat dissipation partition (2a-2), a shell (2), a heat dissipation material, and an insulating plate (3), wherein the heat dissipation material is filled in the gaps between the battery cell unit (1A) and the heat dissipation partition, and between the battery cell unit (1A) and the shell, and characterized in that: The heat dissipation material uses phase change material, which has high latent heat of phase change and absorbs heat from the surface of the battery cell. The phase change temperature of the phase change material is 5℃-10℃ lower than the maximum operating temperature of the battery cell.

2. According to claim 1, the battery heat dissipation structure based on phase change material is characterized in that: The main component of the phase change material is a waxy organic phase change material.

3. The battery heat dissipation structure based on phase change material according to claim 1, characterized in that: The phase change material has insulating properties.

4. The battery heat dissipation structure based on phase change material according to claim 1, characterized in that: The heat dissipation baffle (2a-2) and the outer shell (2) have thermal conductivity and are made of metal materials such as aluminum alloy, steel, and magnesium alloy, or non-metal materials such as plastic, rubber, epoxy resin, and carbon fiber that have thermal conductivity.

5. The battery heat dissipation structure based on phase change material according to claim 1, characterized in that: The heat dissipation baffle (2a-2) and the outer shell (2) are structurally connected in one piece or are separate; the outer shell has a structure and characteristics for dissipating heat to the external environment, including fins, air cooling, and water cooling structures; the outer shell (2) is a semi-open structure, the lower part has a sealing structure to ensure that the phase change material in a molten state will not leak; the upper part has a hole or channel for filling the phase change material.

6. The battery heat dissipation structure based on phase change material according to claim 1, characterized in that: The battery cell unit (1A) is a single battery cell (1) or a combination of single battery cells (1) connected in series and in parallel, and the single battery cell is in the form of a cylindrical battery cell, a square battery cell, or a soft-pack battery cell.

7. The packaging method of a battery heat dissipation structure based on phase change material according to any one of claims 1 to 6, characterized in that: The shell containing the battery cell unit and the phase change material are placed in a high-temperature environment. The temperature of the high-temperature environment is higher than the phase change temperature and not higher than the maximum safe operating temperature of the battery. After the temperature of the battery cell unit and the shell reaches stability and the phase change material melts into liquid, the liquid phase change material is added to the shell to completely encapsulate the battery cell unit.

8. The packaging method of the battery heat dissipation structure based on phase change material according to claim 7, characterized in that: The phase change material is added in batches or all at once.

9. The packaging method of the battery heat dissipation structure based on phase change material according to claim 7, characterized in that: The packaging environment is a normal pressure environment or a vacuum environment with a certain negative pressure. The pressure of the vacuum environment is greater than the lowest vacuum pressure that the battery can withstand. The high temperature environment is obtained by equipment such as an oven, a blast drying oven, and an oil bath.

10. The packaging method of a battery heat dissipation structure based on phase change material according to claim 7 or 9, characterized in that: The temperature of the high temperature environment is 3°C-5°C higher than the phase change temperature and 10°C lower than the maximum safe temperature of the battery, and the pressure of the vacuum environment is greater than the lowest vacuum pressure that the battery can withstand, which is -20kPa to -50kPa.

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