Battery pack and electric vehicle

Abstract

The present application relates to a battery pack, comprising a battery module, which includes battery cells; and a liquid cooling plate assembly, which includes a liquid cooling plate and a first foam layer disposed on a first side of the liquid cooling plate, wherein the thermal conductivity of the first foam layer is greater than 0.5W / Mk; and the first foam layer is in contact with the surface of the battery cells. In the above technical solution, when the thermal conductivity of the foam is greater than 0.5W / Mk, the foam has a good thermal conductivity, and the medium in the liquid cooling plate achieves a good heat exchange effect with the temperature-controlled structure through the first foam layer. The deformation of the first foam layer can fill the gap between the liquid cooling plate and the battery cells, so that the first foam layer and the surface of the battery cells are well in contact, so that heat is evenly transferred to the surface of the battery cells, achieving a good heat conduction effect. In addition, the deformation of the first foam layer increases the contact area with the battery module, making the force on the battery module and the liquid cooling plate more uniform.

Description

Technical Field

[0001] The present application relates to the field of power battery technology, and more specifically, to a battery pack and an electric vehicle. Background Art

[0002] Most existing power battery cooling solutions use liquid cooling. A liquid cooling plate is typically placed at the bottom of the module (a module consists of multiple cells. In the CTP solution, the liquid cooling plate is placed directly at the bottom of the cells). The liquid cooling plate is bonded to the module or cell using thermally conductive gaskets or adhesive. Multiple liquid cooling plates are connected by plastic pipes, through which coolant flows, cooling / heating the module or cell.

[0003] In the current battery packaging assembly process, this places very high demands on the processing technology of the water cooling plate and the assembly technology of the module, resulting in a decrease in the yield rate and affecting production efficiency. Summary of the Invention

[0004] One of the objectives of this application is to provide a battery pack for reducing the defective rate during battery pack assembly, which is achieved by the following technical solutions:

[0005] A battery pack includes a battery module, wherein the battery module includes a battery cell; and further includes a liquid cooling plate assembly, wherein the liquid cooling plate assembly includes a liquid cooling plate and a first foam layer arranged on a first side of the liquid cooling plate, wherein the thermal conductivity of the first foam layer is greater than 0.5W / Mk; and the first foam layer is bonded to the surface of the battery cell.

[0006] In the above technical solution, when the thermal conductivity of the foam is greater than 0.5W / Mk, the foam has a good thermal conductivity effect, and the medium in the liquid cooling plate achieves a good heat exchange effect with the temperature-controlled structure through the first foam layer. At the same time, the foam is an elastic material that can deform after being compressed. In the case of uneven gaps between the battery cell and the liquid cooling plate due to reasons such as the uneven surface of the battery cell or the first side of the liquid cooling plate, the deformation of the first foam layer can fill the gap between the liquid cooling plate and the battery cell, so that the first foam layer and the surface of the battery cell are well fitted, so that heat is evenly transferred to the surface of the battery cell, achieving a better heat conduction effect. In addition, the deformation of the first foam layer increases the contact area with the battery module, making the force on the battery module and the liquid cooling plate more uniform.

[0007] In the above technical solution, the elastic deformation of the first foam layer is used to adapt to the uneven gap between the liquid cooling plate and the battery cell, which reduces the processing requirements for the liquid cooling plate and the assembly requirements for the battery module, reduces production costs and improves the yield rate of the battery pack assembly process.

[0008] Furthermore, the first foam layer contacts the lower surface of the battery core, and the first foam layer is located between the liquid cooling plate and the battery core.

[0009] Furthermore, the first foam layer contacts the upper surface of the battery core, and the first foam layer is located between the liquid cooling plate and the battery core.

[0010] Furthermore, it also includes a lower shell, and a second foam layer is provided on the second side of the liquid cooling plate, and the thermal conductivity of the second foam layer is less than 0.5W / Mk; the second foam layer is located between the lower shell and the liquid cooling plate.

[0011] By also placing a foam layer on the second side of the cooling plate, the gap between the cooling plate and the lower housing can be adjusted to accommodate unevenness. Furthermore, since the cooling plate assembly is positioned below the battery module, the forces between the cooling plate and the battery module are more evenly distributed, preventing structural impacts on the battery module or cooling plate due to localized uneven forces.

[0012] Furthermore, the thermal conductivity of the first foam layer is 1.5 W / Mk, and the thermal conductivity of the second foam layer is 0.1 W / Mk.

[0013] Furthermore, it also includes a lower shell, which is provided with a cross beam; the battery module also includes a fixed frame, the battery cell is located in the fixed frame, and the fixed frame has a module end plate; the module end plate is supported above the cross beam, and an insulation layer is provided between the module end plate and the cross beam, and the thermal conductivity of the insulation layer is less than 0.5W / Mk.

[0014] By setting an insulation layer between the module end plate and the lower shell, the thermal resistance of heat transfer from the module end plate to the crossbeam can be increased, so that the heat in the battery cells in the battery module is mainly transferred through the liquid cooling plate assembly, which facilitates temperature management of the battery module.

[0015] Furthermore, the thermal insulation layer is a foam structural component or a thermal insulation sheet.

[0016] Furthermore, the thickness of the first foam layer is between 2 mm and 15 mm.

[0017] The first foam layer of the aforementioned thickness can better fill the gap between the battery module and the liquid cooling plate through deformation.

[0018] Furthermore, the battery module includes a first sub-module and a second sub-module; the ratio of the volume of the battery cell in the first sub-module to the volume of the battery cell in the second sub-module is a; the ratio of the thermal conductivity coefficient of the first foam layer pasted on the surface of the battery cell in the first sub-module to the first foam layer pasted on the surface of the battery cell in the second sub-module is b; the ratio of a to b is 2.

[0019] The above technical solution uses a first foam layer with different thermal conductivity coefficients for battery cells of different volumes, which can achieve a temperature change rate of the battery cells in the first sub-module that is similar to the temperature change rate of the battery cells in the second sub-module, avoiding a large temperature difference between the first sub-module and the second sub-module, and extending the life of the battery cells.

[0020] A second object of the present application is to provide an electric vehicle comprising the above-mentioned battery pack, which is used to reduce the defective rate during the battery pack assembly process.

[0021] Other features and advantages of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 An exploded view of the liquid cooling plate assembly provided in an embodiment of the present application;

[0024] Figure 2 A schematic cross-sectional view of the liquid cooling plate assembly provided in an embodiment of the present application;

[0025] Figure 3 An exploded view of a portion of the structure of a battery pack provided in an embodiment of the present application;

[0026] Figure 4 A schematic diagram of the module end plate installation and beam provided in an embodiment of the present application;

[0027] Figure 5 A schematic diagram of a portion of the structure of a battery pack provided in an embodiment of the present application;

[0028] Figure 6 Schematic diagram of the flow channel in an existing liquid cooling plate.

[0029] Icons: 11-first sub-module; 12-second sub-module; 13-module end plate; 20-liquid cooling plate assembly; 21-liquid cooling plate; 22-first foam layer; 23-second foam layer; 30-insulation layer; 40-lower shell; 41-crossbeam. DETAILED DESCRIPTION

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0031] In the description of this application, it should be noted that the terms "inner" and "outer" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or the orientations or positional relationships in which the product of this application is typically placed when in use. These terms are intended solely to facilitate the description of this application and simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" and the like are used solely for distinction and should not be construed as indicating or implying relative importance.

[0032] It should also be noted that, in the description of this application, unless otherwise expressly specified or limited, the terms "disposed" and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to direct connections, indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0033] In the existing battery pack assembly process, the liquid cooling plate is installed first, and then a thermal pad is pasted on the upper surface of the liquid cooling plate or thermal adhesive is applied, and then the battery module is installed on top of the liquid cooling plate. The gluing process has high requirements for the flatness of the module and the liquid cooling plate. Otherwise, after the battery module is installed, there may be a gap between the battery cell and the thermal adhesive, resulting in uneven heat dissipation or heating of the battery cell. The thermal pad has poor compressibility. When using a thermal pad to achieve heat exchange between the battery cell and the liquid cooling plate, if the surface flatness tolerance of the liquid cooling plate or the battery cell in the battery module is large, there will be a gap between the thermal pad and the surface of the liquid cooling plate or the surface of the battery cell, and they cannot fit completely, which may also cause uneven heat dissipation or heating of the battery cell.

[0034] After research, the inventors of this application have proposed a battery pack that effectively solves the problem of uneven heating or dissipation of battery cells, while also reducing the flatness tolerance requirements for the liquid cooling plate and the battery cell surface. This improves the battery pack yield rate while saving production costs.

[0035] The battery pack provided in this application includes a battery module, which has multiple battery cells inside. A liquid cooling plate assembly 20 is arranged below the battery module. The liquid cooling plate assembly 20 includes a liquid cooling plate 21. A first foam is arranged on the first side of the liquid cooling plate 21. The thermal conductivity of the first foam is greater than 0.5W / Mk. The first foam is bonded to the surface of the battery cell to achieve heat transfer between the liquid cooling plate 21 and the battery cell.

[0036] Foam is a material made by expanding plastic particles, including PU foam, anti-static foam, conductive foam, EPE, anti-static EPE, CR, EVA, cross-linked PE, SBR, EPDM, etc. Foam materials have good elasticity and low density. The deformation of the foam material compresses and deforms the first foam layer 22 after the battery cell is installed on top of the first foam layer 22. Even if the surface of the liquid cooling plate 21 or the battery cell has a large flatness tolerance, the first foam layer 22 can fill the uneven areas of the battery cell or the surface of the liquid cooling plate 21 after being squeezed and deformed, compensating for the tolerance and ensuring that the gap between the first side surface of the liquid cooling plate 21 and the battery cell is completely filled by the first foam layer 22. Those skilled in the art will readily understand that the thickness of the first foam layer 22 should be greater than the distance between the first side surface of the liquid cooling plate 21 and the surface of the battery cell. The greater the difference between the two, the greater the deformation of the first foam layer 22, allowing it to accommodate liquid cooling plates 21 and battery cells with larger flatness tolerances. However, as the thickness of the first foam layer 22 increases, the heat transfer rate will be affected. Therefore, the thickness of the first foam layer 22 is preferably between 2 mm and 15 mm.

[0037] The density of the foam material is smaller than that of the thermal conductive adhesive, which can make the battery pack lighter. When the first foam layer 22 is used to achieve heat transfer between the liquid cooling plate 21 and the battery module, the weight of the entire vehicle can be reduced and the endurance of the entire vehicle can be improved.

[0038] In terms of assembly process, the use of thermally conductive adhesive for heat transfer requires applying thermally conductive adhesive to the first side of the liquid cooling plate 21 during production. The battery module installation process can only proceed after the thermally conductive adhesive dries, which results in a long waiting time. The use of the liquid cooling plate assembly 20 provided in this application can shorten the assembly time.

[0039] Currently, the liquid cooling plate 21 is mostly installed below the battery cell in the battery pack. However, in the battery pack provided in this application, the liquid cooling plate assembly 20 can be installed below the battery cell, above the battery cell, or between two battery cells. As long as the first foam layer 22 is bonded to the surface of the battery cell, the elastic deformation of the first foam layer 22 can compensate for the flatness tolerance between the first side surface of the liquid cooling plate 21 and the surface of the battery cell, making the heat exchange between the liquid cooling plate 21 and the battery cell more uniform.

[0040] The liquid cooling plate 21 also includes a second side surface opposite to the first side surface. When the liquid cooling plate 21 is installed below the battery module, the second side surface of the liquid cooling plate 21 faces the lower shell 40 of the battery pack. In order to prevent the heat of the medium in the liquid cooling plate from being lost to the lower shell 40 through the second side surface, a heat insulation plate needs to be provided between the second side surface of the liquid cooling plate 21 and the lower shell 40 to reduce the heat exchange between the liquid cooling plate 21 and the lower shell 40. In the embodiment provided in the present application, Figure 1 and Figure 2 As shown, the second side of the liquid cooling plate 21 is provided with a second foam layer 23, whose thermal conductivity is less than 0.5W / Mk. Since the second foam layer 23 is also a foam structural component, it is elastic and can increase the ability of the liquid cooling plate assembly 20 to adapt to the flatness tolerance of the battery cell. Taking the example of the first foam layer 22 and the second foam layer 23 being compressed by 50%, if the combined thickness of the first foam layer 22 and the second foam layer 23 is 10mm, the liquid cooling plate assembly 20 provided in this application can compensate for a 5mm flatness tolerance on the battery cell surface. Of course, the tolerance of the cell surface will not reach 5mm, but in the process of installing the cells to form a battery module, there may be deviations in the vertical installation positions of two adjacent cells, resulting in steps on the lower surfaces of the two adjacent cells. In this case, the elastic deformation of the first foam layer 22 in the present application can also adapt to the installation errors of the cells in the battery module in the height direction, so that the surfaces of the two adjacent cells are in uniform contact with the first foam layer 22, so that the cells in the battery module can be heated or dissipated evenly. Preferably, the thermal conductivity of the first foam layer 22 is 1.5W / Mk, and the thermal conductivity of the second foam layer 23 is 0.1W / Mk.

[0041] When the liquid cooling plate assembly 20 provided in the present application is arranged between two battery cells, the first foam layer 22 and the second foam layer 23 can be respectively adhered to the surfaces of the two adjacent battery cells, and the thermal conductivity coefficients of the first foam layer 22 and the second foam layer 23 can be set to be greater than 0.5W / Mk.

[0042] Currently, foam materials with different thermal conductivity coefficients can be obtained by disposing thermal conductive fillers inside the foam.

[0043] In existing technology, battery packs may contain battery modules of varying sizes. Consequently, the cells within these modules vary in size, and so do the heat dissipation efficiencies. Given the same ambient temperature, larger cells experience slower temperature changes. Given the same temperature change, larger cells absorb or release more heat.

[0044] If the temperature difference between the cells is too large, it will affect the life of the cells. Currently, there is only one liquid cooling plate 21 in the battery pack, which also plays the role of cooling or heating the cells in different modules. The current method to solve the problem of large temperature difference between cells of different volumes is to optimize the flow channel of the liquid cooling plate 21. The flow channel structure inside the liquid cooling plate 21 is as follows: Figure 6 As shown, when the volumes of cells in different battery modules are different, it is technically difficult to optimize the flow channel structure so that the temperature difference between cells is smaller after the medium flows through cells of different volumes.

[0045] In this regard, the inventor of the present application also provides a battery pack with battery cells of different volumes. There is still only one liquid cooling plate 21 in the battery pack. A first foam layer 22 with different thermal conductivity coefficients is provided on the first side of the liquid cooling plate 21, which is used to dissipate heat or heat the battery modules containing battery cells of different volumes to reduce the temperature difference between the battery cells.

[0046] For example, Figure 5 As shown, the battery module within the battery pack includes a first submodule 11 and a second submodule 12. The volume of the cells within the first submodule 11 is larger than that within the second submodule 12. When the temperature changes by the same amount, the cells in the first submodule 11 absorb or release more heat. The thermal conductivity of the first foam layer below the first submodule 11 is greater than that of the first foam layer below the second submodule 12. When the temperature of the medium in the liquid cooling plate 21 is the same, the cells in the first submodule 11 exchange more heat with the liquid cooling plate 21 through the first foam layer with a higher thermal conductivity. This allows the temperature of the cells in the first submodule 11 to change synchronously with that of the cells in the second submodule 12, reducing the temperature difference between cells of different volumes and extending the service life of the cells. The volume ratio of the battery cells in the first submodule 11 to the battery cells in the second submodule 12 is a; the thermal conductivity ratio of the first foam layer below the first submodule 11 to the first foam layer below the second submodule 12 is b. According to the inventor's experiments, when a = 10, if b = 1, the temperature difference between the first submodule 11 and the second submodule 12 will reach 20°C; when a = 10, if b = 5, the measured temperature difference is approximately 10°C. Preferably, a and b have a relationship of a:b = 2.

[0047] The battery module includes a fixed frame for fixing the battery cells. The fixed frame has a module end plate 13. A crossbeam 41 is provided in the battery pack. The current battery module is supported on the crossbeam 41 by the module end cover. The current module end plate 13 and crossbeam 41 are generally made of aluminum, which has a high thermal conductivity. In a low temperature environment, the temperature of the battery module or battery cell drops rapidly, making it difficult to control the temperature. In the battery pack provided in this application, Figure 3 and Figure 4As shown, a heat insulation layer 30 with a thermal conductivity coefficient less than 0.5W / Mk is provided between the crossbeam 41 and the module end plate 13. The heat insulation layer 30 can be made of mica sheet, epoxy resin or other materials, or foam with a thermal conductivity coefficient that meets the requirements.

[0048] The present application also provides an electric vehicle equipped with the above-mentioned battery pack.

[0049] It should be noted that, unless there is any conflict, the features in the embodiments of this application can be combined with each other.

[0050] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A battery pack, comprising a battery module, wherein the battery module comprises a battery cell; The battery pack further includes a liquid cooling plate assembly, the liquid cooling plate assembly including a liquid cooling plate and a first foam layer disposed on a first side of the liquid cooling plate, wherein the thermal conductivity of the first foam layer is greater than 0.5 W / Mk; the first foam layer is bonded to the surface of the battery cell; and the thickness of the first foam layer is between 2 mm and 15 mm; The battery module includes a first submodule and a second submodule; the ratio of the volume of the battery cell in the first submodule to the volume of the battery cell in the second submodule is a; the ratio of the thermal conductivity of the first foam layer attached to the surface of the battery cell in the first submodule to the first foam layer attached to the surface of the battery cell in the second submodule is b; the ratio of a to b is 2; It also includes a lower shell, and a second foam layer is provided on the second side of the liquid cooling plate, and the thermal conductivity of the second foam layer is less than 0.5W / Mk; the second foam layer is located between the lower shell and the liquid cooling plate; the first side and the second side are two opposite sides of the liquid cooling plate.

2. The battery pack according to claim 1, wherein: The first foam layer contacts the lower surface of the battery core, and the first foam layer is located between the liquid cooling plate and the battery core.

3. The battery pack according to claim 1, wherein: The first foam layer contacts the upper surface of the battery core, and the first foam layer is located between the liquid cooling plate and the battery core.

4. The battery pack according to claim 1, wherein: The thermal conductivity of the first foam layer is 1.5 W / Mk, and the thermal conductivity of the second foam layer is 0.1 W / Mk.

5. The battery pack according to claim 1, wherein: It also includes a lower shell, which is provided with a cross beam; the battery module also includes a fixed frame, the battery cell is located in the fixed frame, and the fixed frame has a module end plate; the module end plate is supported above the cross beam, and an insulation layer is provided between the module end plate and the cross beam, and the thermal conductivity of the insulation layer is less than 0.5W / Mk.

6. The battery pack according to claim 5, characterized in that: The heat insulation layer is a foam structure component or a heat insulation sheet.

7. An electric vehicle, characterized in that: A battery pack comprising any one of claims 1 to 6.

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