Power battery module

Abstract

The invention provides a power battery module, which comprises: a box body, in which at least one battery monomer is arranged; an air inlet is formed in a bottom plate of the box body; the cover plate is arranged on the box body in a covering manner, and an air outlet is formed in the cover plate; the heat dissipation collision-resistant unit is located in the module box body, and the heat dissipation collision-resistant unit comprises a foam metal layer and a metal side plate; foam holes in the foam metal layer are distributed in a gradient mode, the area, close to the metal side plate, of the foam metal layer has first porosity, the area, away from the metal side plate, of the foam metal layer has second porosity, and the first porosity is smaller than the second porosity. The working efficiency of the power battery can be improved, the service life of the power battery can be prolonged, the safety risk caused by collision damage can be reduced, and the comprehensive performance of the power battery in a complex and changeable use environment is improved.

Description

Technical Field

[0001] The present invention belongs to the field of new energy electric vehicles, and in particular relates to a power battery module based on gradient open-pore aluminum foam. Background Art

[0002] At present, electric vehicles have the advantages of high efficiency, energy saving and low emissions, and have gradually become an important direction for the development of automobiles. Pure electric vehicles are driven by electricity and have gotten rid of the dependence on oil. They have high energy utilization and low environmental pollution. At the same time, large-capacity power battery systems can store electrical energy, reasonably guide electric vehicles to charge at off-peak times, store excess power from the power grid, and reduce resource waste. At present, the new energy vehicle industry represented by electric vehicles has become one of my country's important strategic emerging industries, and the development of electric vehicles is showing a rapid growth trend.

[0003] Among various types of energy storage technologies for electric and hybrid vehicles, lithium-ion batteries stand out for their light weight, high energy density, long cycle life, low self-discharge rate, and no memory effect. They are currently the main electrochemical energy source for new energy vehicles. Although lithium-ion batteries have many advantages, they are very sensitive to temperature. When the temperature is below 0°C or above 45°C, the number of cycles and performance of the battery will decrease. If the heat generated by lithium-ion batteries during operation accumulates and cannot be eliminated in time, it will cause problems such as rapid aging, low number of cycles, and short service life. In severe cases, it is prone to local overheating, leakage, and even thermal runaway.

[0004] The active electrochemical reaction of lithium-ion batteries brings high energy output, but also makes it more likely to cause fire in a collision accident. Most electric vehicle power batteries are connected in series and parallel and densely arranged in a small vehicle space. If they encounter extreme abuse such as collision, extrusion or puncture, it is easy to cause battery damage, resulting in a significant increase in the battery heat generation rate, causing a sharp rise in temperature and even thermal runaway, which in turn causes the entire battery pack to catch fire, burn, explode and other safety accidents, seriously threatening the safety of electric vehicles. Compared with traditional fuel vehicles, new energy electric vehicles need to pay attention not only to occupant protection in terms of collision safety, but also need to pay special attention to the collision safety of the battery system.

[0005] In the prior art, a foam aluminum plate is arranged on both sides of the battery cell, but the holes in the foam aluminum plate are usually of uniform size or of random and irregular density, which results in limitations in its strength. Under vibration, impact or long-term practical use, the structural strength and durability will become a hidden danger, especially in the power module battery, which cannot provide sufficient protection in the event of severe vibration or collision, resulting in battery damage or performance degradation. Summary of the invention

[0006] The purpose of the present invention is to improve the heat dissipation performance and collision safety performance of a power battery module and to provide a power battery with efficient heat dissipation and good impact resistance.

[0007] To achieve the above object, the present invention adopts the following technical solution: a power battery module, comprising:

[0008] A box body, wherein at least one battery cell is arranged in the box body; an air inlet is arranged on the bottom plate of the box body;

[0009] A cover plate, the cover plate is arranged on the box body, and an air outlet is arranged on the cover plate;

[0010] A heat dissipation and collision resistance unit is located in the module box, and the heat dissipation and collision resistance unit includes a foam metal layer and a metal side plate;

[0011] It is characterized in that the foam pores in the foam metal layer are distributed in a gradient manner, the foam metal layer has a first porosity in an area close to the metal side plate, and has a second porosity in an area away from the metal side plate, and the first porosity is smaller than the second porosity.

[0012] Furthermore, the heat dissipation and durability unit includes a first metal side plate, a foam metal layer, and a second metal side plate, and the foam metal layer is located between the first metal side plate and the second metal side plate.

[0013] Furthermore, the foam pores of the foam metal layer are distributed in a gradient symmetrical manner, the surface area of ​​the foam pores close to the first metal side plate has the first porosity, and the area of ​​the foam pores away from the central symmetry plane of the foam metal layer has the second porosity; the surface area of ​​the foam pores close to the second metal side plate has the first porosity, and the surface area of ​​the foam pores close to the central symmetry plane away from the second metal side plate has the second porosity.

[0014] Furthermore, the porosity gradient of the foam metal layer is controlled by the following formula:

[0015]

[0016] Among them, ε x To express the porosity at a certain point in the gradient aluminum foam, ε max and ε min are the maximum porosity and minimum porosity in this study respectively, x-metal side plate represents the distance to the edge with the highest density, b is the distance from the second metal side plate to the center plane, and m represents the power exponential parameter controlling the porosity change.

[0017] Furthermore, the metal side plate is an aluminum plate, and the foam metal layer is a foam aluminum layer.

[0018] Furthermore, the power battery module includes N battery cells and N+1 heat dissipation and collision-resistant units, and the heat dissipation and collision-resistant units are arranged on both sides of the battery cells, and N is a natural number greater than or equal to 1.

[0019] Furthermore, the foam metal layer is fixedly connected to the first metal side plate and the second metal side plate by any one of screws, riveting, brazing and laser beam welding.

[0020] Furthermore, the gradient distribution of the foam metal layer is achieved by regulating a power exponent parameter m of the porosity change, and the value range of the power exponent parameter m is 0.1≤m≤10.

[0021] Furthermore, the low porosity region of the foam metal layer is coated with a coating material which is a mixture of a thermally conductive polymer coating and a metal coating.

[0022] The present invention also provides a coating method for a foam metal structure for improving heat dissipation and crash resistance, the method comprising the following steps:

[0023] S01: surface pretreatment, cleaning the surface of the foam metal structure;

[0024] S02: preparing a coating material, adding a polymer matrix to a solvent, heating and stirring until completely dissolved to form a uniform solution; slowly adding a thermal conductive filler and a dispersant under stirring, and performing ultrasonic dispersion or high-speed shear mixing to improve the dispersibility of the thermal conductive filler to form a coating liquid with a viscosity in the range of 1000 to 5000 centipoise (cps);

[0025] S03: Dip coating treatment, immersing the low porosity area of ​​the foam metal structure into the coating liquid, the immersion time is 10 to 30 seconds, and the immersion speed is 0.5 to 1.5 m / min, so that the coating material evenly covers the low porosity area;

[0026] S04: removing excess coating liquid, after the foam metal structure is lifted from the coating liquid, applying centrifugal force to remove excess coating liquid to prevent the coating from accumulating in certain areas;

[0027] S05: Coating curing and height detection: the coated foam metal structure is cured and the height after coating is detected to ensure that the coating thickness is within the allowable tolerance range.

[0028] Based on the excellent enhanced heat transfer and lightweight energy absorption characteristics of gradient open-cell aluminum foam, the present invention incorporates heat dissipation and collision protection into the same framework, which can not only improve the working efficiency and life of the power battery, but also reduce the safety risks caused by collision damage, and improve its comprehensive performance in complex and changeable use environments. The thermal conductivity of the low porosity area of ​​the heat dissipation and collision-resistant unit can be effectively improved through the thermal conductive polymer coating and the metal coating, so that heat can be transferred and dissipated faster, and the coating material can cover the low porosity area to avoid the decrease in heat dissipation performance due to low porosity, ensuring that the overall temperature of the battery module is controlled within a safe range. The improved heat dissipation and impact resistance design can significantly extend the service life of the battery module and reduce failures caused by overheating or impact. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0030] Figure 1 is a schematic structural diagram of a power battery module of the present invention;

[0031] Figure 2 It is a schematic diagram of the structure of a single battery unit in the present invention;

[0032] Figure 3 This is the processing technology of the foam metal layer in the present invention.

[0033] 1. Box body; 2. Cover body; 3. Foam metal layer; 4. First metal side plate; 5. Second metal layer; 6. Battery cell. DETAILED DESCRIPTION

[0034] It should be noted that those skilled in the art will easily think of other embodiments of the present application after considering the specification and practicing the invention disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary technical means in the art that are not disclosed in the present application. The specification and examples are only regarded as exemplary, and the true scope and spirit of the present application are indicated by the claims.

[0035] It should be understood that the present application is not limited to the precise structure described below and shown in the drawings, and various modifications and changes can be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims, and the present invention is further described in conjunction with the drawings and specific embodiments.

[0036] See also Figures 1 to 3 The scheme shown, the technical solution adopted by the embodiment of the present invention is:

[0037] A power battery module comprises: a box body 1, wherein at least one battery cell 6 is arranged in the box body 1; an air inlet is arranged on the bottom plate of the box body 1; a cover plate, wherein the cover plate is arranged on the box body 1 and the cover plate is provided with an air outlet; a heat dissipation and collision-resistant unit is located in the module box body 1, wherein the heat dissipation and collision-resistant unit comprises a foam metal layer 3 and a metal side plate; the foam pores in the foam metal layer 3 are distributed in a gradient manner, the foam metal layer 3 has a first porosity in an area close to the metal side plate, and has a second porosity in an area away from the metal side plate, and the first porosity is smaller than the second porosity. The present invention optimizes the heat dissipation effect of the power battery module by distributing the porosity of the pores in the foam metal layer 3 in a gradient manner, provides a larger surface area in the area with higher porosity, so that the power battery can dissipate heat faster, and has higher structural strength in the area with lower porosity close to the metal side plate, which can effectively absorb external impact force and protect the battery cell 6 from external impact damage. By setting the porosity of the foam metal layer 3 in a gradient manner, it can provide excellent impact resistance while enhancing the safety performance of the module.

[0038] In some embodiments of the present invention, the first porosity is smaller than the second porosity. In the process from the first porosity to the second porosity, the porosity change of the foam metal layer is gradient distributed, rather than a completely determined vertical. The first porosity can be regarded as the porosity value of the foam metal layer closest to the metal side plate, and the second porosity is the value of the foam metal layer at the farthest end from the metal side plate.

[0039] In some embodiments of the present invention, the air inlet is arranged near one side edge of the bottom plate of the box body 1 and close to the battery cell 6, which can allow air to enter from below, ensuring that the cold air can directly contact the lower part of the battery cell 6, and then gradually flow upward to cover the entire surface of the battery cell 6; the air outlet is arranged at the top of the cover plate, which can be set at a diagonal position with the air inlet, so that the air flow path is the longest, so that its cold air can cover the entire battery module, and the flow path with the maximum stroke.

[0040] In some embodiments of the present invention, optionally, there may be multiple air inlets evenly distributed at multiple positions of the bottom plate to ensure that air can evenly enter the box body 1, thereby avoiding local overheating; there may also be multiple air outlets corresponding to the air inlet, and the number and distribution of the air outlets correspond to the air inlet, which are arranged at corresponding positions of the position of the foam metal layer 3, so that cold air can pass through the foam metal layer 3 and then flow out from the air outlet position, so that all battery cells 6 are evenly cooled.

[0041] The heat dissipation and collision-resistant unit includes a first metal side plate 4, a foam metal layer 3, and a second metal side plate 5. The foam metal layer 3 is located between the first metal side plate 4 and the second metal side plate 5. By arranging the foam metal layer 3 between the first metal side plate 4 and the second metal side plate 5, its strength and impact resistance can be effectively increased. The pore structure of the foam metal layer 3 and the side plate can naturally form airflow channels. These channels can guide air to enter from the air inlet and flow through the battery cell 6 along a set path, and finally be discharged from the air outlet. The first metal side plate 4 and the second metal side plate 5 are fixed by welding, riveting or screws, and the foam metal layer 3 is firmly clamped in the middle to ensure that energy can be effectively dispersed and absorbed when impacted. This can also ensure that the airflow in the module is effectively guided, thereby improving the heat dissipation efficiency.

[0042] In some embodiments of the present invention, the foam pores of the foam metal layer 3 are distributed in a gradient symmetrical manner, the surface area of ​​the foam pores close to the first metal side plate 4 has a lower porosity, and the area of ​​the foam pores away from the central symmetric plane of the foam metal layer 3 has a higher porosity; the surface area of ​​the foam pores close to the second metal side plate 5 has a lower porosity, and the surface area of ​​the foam pores away from the second metal side plate 5 and close to the central symmetric plane has a higher porosity. By distributing the porosity of the foam metal layer 3 in a gradient manner along the central symmetric plane, the porosity gradually decreases when the center of the foam layer transitions to the first metal side plate 4 and the second metal side plate 5. This symmetrical design can ensure that heat is evenly distributed between the first metal side plate 4 and the second metal side plate 5 to avoid local overheating, and by making the porosity of the foam pores of the foam metal layer 3 the highest in the area close to the central symmetric plane, it is helpful to achieve more efficient airflow in this area, which can take away more heat, and as the distance from the central symmetric plane gradually approaches the metal side plate, the porosity gradually decreases, increasing the density and structural strength of the material, thereby improving the impact resistance.

[0043] Furthermore, the porosity gradient of the foam metal layer 3 is controlled by the following formula:

[0044]

[0045] Among them, ε x To represent the porosity at a certain point in the gradient metal foam layer, ε max and ε min are the maximum porosity and the minimum porosity, respectively; x represents the distance from the first metal side plate to the edge with the highest density; b represents the distance from the second metal side plate 5 to the center plane; and m represents the power exponent parameter for controlling the porosity change. Further, the gradient distribution of the foam metal layer is achieved by regulating the power exponent parameter m for the porosity change, and the value range of the power exponent parameter m is 0.1≤m≤10. Preferably, εmax =0.92 and ε min =0.68.

[0046] The following table is a comparison table of thermal resistance and impact absorption capacity when the foam metal layer 3 is made of aluminum and has a gradient porosity and when the foam metal layer has a constant porosity;

[0047]

[0048] From the table, we can see that the area close to the metal side panel (porosity 68%) provides higher thermal conductivity and impact absorption capacity, suitable for bearing external impact and providing better heat dissipation performance, the middle area (porosity 80%) balances the impact absorption capacity and heat dissipation performance, suitable for finding a balance between heat dissipation and energy absorption, and the area far away from the metal side panel (porosity 92%) provides a good thermal conduction channel, reduces the channel pressure drop, and reduces system power consumption.

[0049] Unchanged design (80% constant porosity): Both the impact absorption capacity and thermal conductivity are medium values, providing medium impact absorption capacity and heat dissipation performance. The thermal resistance is low, suitable for more balanced heat dissipation needs, but may not provide optimal performance in some areas.

[0050] Strength: Gradient designs provide higher strength in areas where higher strength is needed (near the metal side panels), while the uniform strength distribution of non-changing designs may not provide localized additional protection.

[0051] Thermal conductivity: The low porosity area of ​​the gradient design (close to the metal side panel) provides better heat dissipation performance, and provides better fluidity in the area away from the metal side panel, thereby reducing system power consumption. The heat dissipation performance of the unchanged design is medium and the power consumption is high, and the heat dissipation effect may not be as good as the gradient design in some areas.

[0052] Impact absorption capacity: The low porosity areas of the gradient change design can effectively absorb more impact energy, while the impact absorption capacity of the unchanged design is low and may not be sufficient to protect the battery cells under extreme conditions.

[0053] By comparison, it can be seen that the porosity gradient design of the foam metal layer shows better performance in terms of structural strength, thermal conductivity and impact absorption capacity, especially in the optimization of performance in specific areas. In contrast, the design with constant porosity provides uniform performance but may not achieve the best results in some cases.

[0054] In some embodiments of the present invention, the foam metal layer 3 is fixedly connected to the first metal side plate 4 and the second metal side plate 5 by any one of screws, riveting brazing, and laser beam welding. Specifically, the foam metal layer 3 and the first metal side plate 4 are fixedly connected by using high-strength, stainless steel screws to ensure that they are not easy to loosen or corrode during long-term use. The length of the screw is determined according to the thickness of the foam metal layer 3 and the first metal side plate and the second metal. Screw holes are pre-arranged on the foam metal layer 3 and the metal side plate for precise alignment, and reinforcing ribs are added in the area near the screw holes to improve the connection strength and prevent the screws from loosening.

[0055] Optionally, the materials of the first metal side plate 4, the second metal side plate 5 and the foam metal layer 3 are selected by selecting aluminum-based or nickel-based brazing filler metals to ensure that good metallurgical bonding can be formed during brazing, and a low-temperature brazing process is adopted to avoid high temperature from damaging the pore structure of the foam metal layer 3. Brazing is performed under inert gas protection or a vacuum environment to prevent oxidation and ensure that the metal surface of the welding area remains clean, thereby improving the welding quality.

[0056] Optionally, the materials of the first metal side plate 4, the second metal side plate 5 and the foam metal layer 3 can be welded by precision laser equipment, such as fiber laser or carbon dioxide laser, and the laser power and focal position need to be adjusted according to the material thickness of the metal side plate and the foam metal layer 3.

[0057] In some embodiments of the present invention, the metal side plate is an aluminum plate, and the foam metal layer 3 is a foam aluminum layer. The interior of the foam aluminum layer has a large number of closed and open pores, so that it can form an efficient heat dissipation channel inside, effectively reduce the operating temperature of the battery module, and it can absorb energy under the action of external force, and the foam filter layer has a lower porosity in the area close to the aluminum plate, which can effectively enhance the mechanical strength and thermal conductivity of the area, and the area away from the aluminum plate can be designed to have a higher porosity, which can improve the energy absorption performance. Optionally, when the metal side plate is an aluminum plate and the foam metal layer 3 is a foam aluminum layer, the metal aluminum plate and the foam aluminum plate are firmly combined by a hot pressing process, which can provide better mechanical strength and ensure good thermal conductivity of the interface component.

[0058] In some embodiments of the present invention, the power battery module includes N battery cells 6 and N+1 heat dissipation and crash-resistant units, and the heat dissipation and crash-resistant units are arranged on both sides of the battery cells 6, and N is a natural number greater than or equal to 1. Specifically, heat dissipation and crash-resistant units are arranged on both sides of each battery cell 6 in the power battery module, and the heat dissipation and crash-resistant units, battery cells 6, and heat dissipation and crash-resistant units are arranged alternately, and there is still a heat dissipation and crash-resistant unit on one side of the outermost battery cell 6, so that it can effectively increase the coverage of the heat dissipation and crash-resistant units, ensuring that each battery cell 6 can be fully protected and heat dissipated, and the added additional heat dissipation and crash-resistant units can provide additional impact resistance and heat dissipation protection to prevent the terminal battery cell 6 from being affected by external impact or heat accumulation.

[0059] In some embodiments of the present invention, the heat dissipation and impact-resistant unit is coated with a coating for improving the heat dissipation capacity in the low porosity area in the area in contact with the battery cell 6, so that the heat dissipation capacity of the area in contact with the battery cell 6 will not be reduced due to low porosity.

[0060] In some embodiments of the present invention, the coating material is prepared by coating a thermally conductive polymer coating and a metal coating on the area with low porosity of the heat dissipation and collision-resistant unit. Specifically, polymer materials such as polyimide (PI), polyamide (PA), and epoxy resin are selected as the base material, and aluminum oxide (Al2O3), magnesium oxide (MgO), carbon nanotubes, graphene, etc. are selected as thermally conductive fillers to coat the surface of the heat dissipation and collision-resistant unit.

[0061] Specifically, in order to ensure that the coating material can be fully coated on the area of ​​the heat dissipation and collision-resistant unit with low porosity, the following coating process is performed;

[0062] S01: Pretreatment: Before coating, the foam metal layer in the heat dissipation and collision resistance unit is cleaned to ensure that the surface is free of oil and impurities and can evenly adhere to the coating material;

[0063] S02: Add the polymer matrix to the solvent, heat and dissolve it under stirring, ensure that the polymer is completely dissolved to form a uniform solution, slowly add the thermal conductive filler under stirring, and at the same time add a dispersant, ultrasonic dispersion or high-speed shear mixer to improve the dispersibility of the filler, and form a coating material dipping solution, the viscosity of which is between 1000 and 5000 cps (centipoise), preferably 2800 cps.

[0064] S03: Immerse the first porosity region of the foam metal layer in the coating liquid for 10-30 seconds at a speed of 0.5-1.5 m / min, so that the coating material can evenly cover the low porosity region.

[0065] S04: When the foam metal layer is lifted from the dipping liquid, the excess coating liquid is removed by centrifugal force to prevent the coating from accumulating in certain areas and affecting the height, which will lead to poor heat dissipation capacity.

[0066] S05: After coating, curing treatment is performed. After curing is completed, the height of the foam metal layer is tested to ensure that the height after coating is within the allowable tolerance range.

[0067] The following table is a comparison table of thermal resistance with the foam metal layer 3 being aluminum and having a gradient porosity combined with coating in the area with lower porosity and the foam metal layer having a gradient change and no coating layer;

[0068]

[0069] It can be seen from the table that after applying the heat dissipation coating, the area close to the metal side panel (porosity 68%): the heat dissipation performance of the foam metal can be enhanced, so the thermal conductivity will be improved. Due to the addition of the coating, the structural strength is increased, and the coating can play a strengthening role, but its impact absorption capacity is slightly reduced, but the overall heat dissipation performance is improved.

[0070] In some embodiments of the present invention, the battery cells are square battery cells, which can be neatly arranged in the power battery module to maximize the use of the space inside the box, and have a flat surface that can be in close contact with the heat dissipation and collision-resistant unit, thereby improving heat conduction efficiency.

[0071] The present invention increases the surface area by making the porosity of the foam metal layer higher in the area far away from the metal side plate, which helps to dissipate heat more efficiently. The area close to the metal side plate has a lower porosity, which provides better thermal conductivity and ensures that heat can be quickly transferred to the heat dissipation area. The area close to the metal side plate has a lower porosity, which improves the mechanical strength of the foam metal layer, can better absorb and disperse external impact forces, and protect the battery cells from damage. The area far away from the metal side plate has a higher porosity, which provides better energy absorption performance and reduces the impact of external forces on the battery module. Furthermore, the thermal conductivity of the low-porosity area of ​​the heat dissipation and collision-resistant unit can be effectively improved by the thermal conductive polymer coating and the metal coating, so that heat can be transferred and dissipated faster, and the coating material can cover the low-porosity area to avoid the decrease in heat dissipation performance due to low porosity, ensuring that the overall temperature of the battery module is controlled within a safe range. The improved heat dissipation and impact resistance design can significantly extend the service life of the battery module and reduce failures caused by overheating or impact.

[0072] It should be noted that, in the present application, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or still includes elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements limited by the sentence "comprise one..." do not exclude the existence of other identical elements in the process, method, article or equipment including the elements. Each embodiment in the present application is described in a related manner, and the same and similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments.

[0073] The basic principles, main features and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for illustrating the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which shall fall within the scope of the present invention to be protected. The scope of protection of the present invention shall be defined by the attached claims and their equivalents.

Claims

1. A power battery module, comprising: A box body, wherein at least one battery cell is arranged in the box body; an air inlet is arranged on the bottom plate of the box body; A cover plate, the cover plate is arranged on the box body, and an air outlet is arranged on the cover plate; A heat dissipation and collision resistance unit is located in the module box, and the heat dissipation and collision resistance unit includes a foam metal layer and a metal side plate; It is characterized in that the foam pores in the foam metal layer are distributed in a gradient manner, the foam metal layer has a first porosity in an area close to the metal side plate, and has a second porosity in an area away from the metal side plate, and the first porosity is smaller than the second porosity.

2. The power battery module according to claim 1, characterized in that: The heat dissipation and durability unit comprises a first metal side plate, a foam metal layer, and a second metal side plate, wherein the foam metal layer is located between the first metal side plate and the second metal side plate.

3. The power battery module according to claim 2, characterized in that: The foam pores of the foam metal layer are distributed symmetrically in a gradient, the surface area of ​​the foam pores close to the first metal side plate has the first porosity, and the area of ​​the foam pores away from the central symmetry plane of the foam metal layer has the second porosity; the surface area of ​​the foam pores close to the second metal side plate has the first porosity, and the surface area of ​​the foam pores close to the central symmetry plane away from the second metal side plate has the second porosity.

4. A power battery module according to claim 3, characterized in that: The porosity gradient of the foam metal layer is controlled by the following formula: Among them, ε x To express the porosity at a certain point in the gradient aluminum foam, ε max and ε min are the maximum porosity and minimum porosity in this study respectively, x represents the distance from the first metal side plate to the edge with the highest density, b represents the distance from the second metal side plate to the center plane, and m represents the power exponential parameter controlling the porosity change.

5. The power battery module according to claim 1, characterized in that: The metal side plate is an aluminum plate, and the foam metal layer is a foam aluminum layer.

6. The power battery module according to claim 1, characterized in that: The power battery module includes N battery cells and N+1 heat dissipation and collision-resistant units. The heat dissipation and collision-resistant units are arranged on both sides of the battery cells. N is a natural number greater than or equal to 1.

7. The power battery module according to any one of claims 2 to 4, characterized in that: The foam metal layer is fixedly connected to the first metal side plate and the second metal side plate by any one of screws, riveting, brazing and laser beam welding.

8. The power battery module according to claim 4, characterized in that: The gradient distribution of the foam metal layer is achieved by regulating the power exponent parameter m of the porosity change, and the value range of the power exponent parameter m is 0.1≤m≤10.

9. The power battery module according to claim 4, characterized in that: The low porosity region of the foam metal layer is coated with a coating material which is a mixture of a thermal conductive polymer coating and a metal coating.

10. A coating method for a foam metal layer in a power battery module according to claim 9, the method comprising the following steps: S01: surface pretreatment, cleaning the surface of the foam metal layer; S02: preparing a coating material, adding a polymer matrix into a solvent, heating and stirring until completely dissolved to form a uniform solution; slowly adding a thermal conductive filler and a dispersant under stirring, and forming a coating liquid after ultrasonic dispersion or high-speed shear mixing; S03: dip coating treatment, immersing the first porosity region of the foam metal layer into the coating liquid, the immersion time is 10 to 30 seconds, the immersion speed is 0.5 to 1.5 m / min, so that the coating material uniformly covers the first porosity region; S04: removing excess coating liquid, after the foam metal structure is lifted from the coating liquid, applying centrifugal force to remove excess coating liquid; S05: Coating curing and height detection: curing the coated foam metal layer and detecting the height after coating.

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