Battery pack bottom protection plate, battery pack comprising same and vehicle

Abstract

The utility model provides a battery pack bottom protection plate, a battery pack comprising the same and a vehicle, the battery pack bottom protection plate comprises a metal plate, a first electrophoresis layer located on the first surface of the metal plate and a second electrophoresis layer located on the second surface of the metal plate, and the surface, away from the metal plate, of the first electrophoresis layer is provided with a coating. The coating is a solvent type coating or a solvent-free type coating, the thickness of the coating ranges from 200 micrometers to 900 micrometers, and the surface roughness of the coating is smaller than or equal to 20 micrometers. According to the scheme, the wear resistance of the battery pack bottom protection plate coating can be improved, the battery swap station circulation frequency of the battery pack is increased, the metal plate is protected from being corroded by the external environment, and therefore the service life of the battery pack is prolonged.

Description

Technical Field

[0001] This application belongs to the technical field of batteries, and particularly relates to a bottom protection plate of a battery pack, a battery pack containing the same, and a vehicle. Background Art

[0002] In the past two years, the domestic new energy vehicle market has shown a rapid growth trend. With the rapid development of new energy, how to build a perfect energy replenishment system has become an inevitable problem. At present, there are two ways to replenish energy for pure electric vehicles in China. One is to build charging piles, which is more common, and the other is to layout battery swapping stations like NIO. On the one hand, the battery swapping system has a crushing advantage in terms of energy replenishment efficiency. For example, it is more convenient and faster for users. On the other hand, since the battery swapping station uniformly manages the batteries, all users no longer need to worry about battery attenuation and safety issues, and can get a battery physical examination every time they swap the battery.

[0003] At present, the warranty period of power batteries is generally 8 years. After battery companies sell batteries or vehicle manufacturers that adopt the charging energy replenishment route sell vehicles, they do not have much economic motivation to improve the service life of the batteries. For NIO, which adopts the battery swapping energy replenishment route, if it can improve the service life of the batteries, it can bring huge economic benefits. At present, NIO plans to promote a 15-year worry-free battery service, increasing the warranty period of power batteries from 8 years to 15 years, which puts more stringent requirements on the current service life of the batteries. However, there is little prior art reporting on how to improve the service life of power batteries to 15 years. Summary of the Utility Model

[0004] The applicant found that when the battery pack is replenished with battery swapping, it needs to be transferred through a chain or a roller at the battery swapping station. During the transfer process, the bottom protection plate of the battery pack will inevitably come into contact with the chain or the roller, generating friction. If the wear resistance of the coating on the bottom protection plate of the battery pack is poor, it will cause the coating to become thinner or even expose the metal bottom plate, increasing the risk of the metal bottom plate being exposed, corroded or penetrated by external forces, and affecting the service life of the battery pack.

[0005] At present, the coating on the bottom protection plate of the battery pack usually adopts a solvent-based polyvinyl chloride (PVC) coating to achieve the effects of anti-corrosion and anti-stone impact, but the wear resistance of the coating is not considered. Taking NIO's second-generation battery swapping station as an example, the chains used for battery swapping transfer are distributed in 4 positions: the connection position, the buffer position, the lifting position, and the battery compartment position. When the battery pack is transferred from one position to another, there is a sliding friction between the chain and the bottom protection plate of the battery pack. The existing battery packs with PVC-coated bottom protection plates will have the PVC coating worn after 500 - 800 transfers and circulations at the battery swapping station, exposing the underlying anti-corrosion layer, thus affecting the service life of the battery pack. If the service life of the battery pack is to be increased to 15 years, ideally, the coating on the bottom protection plate of the battery pack should not be worn through after 1500 transfers and circulations at the battery swapping station according to the normal usage frequency.

[0006] In view of this problem, the present application provides a bottom guard plate for a battery pack, which can improve the wear resistance of the coating on the bottom guard plate of the battery pack, increase the number of times the battery pack is transferred in the battery swapping station, extend the service life of the battery pack, and at the same time, the coating can also serve as a protective layer to effectively isolate the metal plate from the external environment and protect the metal plate from environmental erosion, thereby extending the life of the battery pack.

[0007] In a first aspect of the present application, there is provided a bottom guard plate for a battery pack, including a metal plate, a first electrophoretic layer on a first surface of the metal plate, and a second electrophoretic layer on a second surface of the metal plate. A coating is provided on a surface of the first electrophoretic layer away from the metal plate. The coating is a solvent-based coating or a solvent-free coating. The thickness of the coating is 200 μm - 900 μm, and the surface roughness of the coating is ≤ 20 μm.

[0008] In a second aspect of the present application, there is provided a battery pack, which includes the bottom guard plate for a battery pack as described in the first aspect, and the coating is provided on an outer surface of the battery pack.

[0009] In a third aspect of the present application, there is provided a vehicle, which includes the battery pack as described in the second aspect, and the battery pack is installed at the bottom of the vehicle.

[0010] The beneficial effects of the present application are as follows: The bottom guard plate of the battery pack in the present application improves the wear resistance of the bottom guard plate of the battery pack through the solvent-based coating or solvent-free coating on the metal plate, enabling the battery pack to withstand the continuous scraping friction caused by periodic sliding with the transmission chain or roller during the battery swapping process, increasing the number of times the battery pack is transferred in the battery swapping station, and extending the service life of the battery pack. At the same time, the solvent-based coating or solvent-free coating can effectively isolate the metal plate from the external environment and protect the metal plate from environmental erosion, thereby further extending the life of the battery pack. Description of the Drawings

[0011] Figure 1 It is a schematic structural diagram of the bottom guard plate of the battery pack in Embodiment 1 of the present utility model.

[0012] Figure 2 It is a schematic structural diagram of the bottom guard plates of the battery packs in Embodiments 2 - 4 and Comparative Examples 1 - 2 of the present utility model.

[0013] In the figure, 1 is the metal plate, 21 is the first electrophoretic layer, 22 is the second electrophoretic layer, 31 is the solvent-free coating, and 32 is the solvent-based coating. Detailed Embodiments

[0014] For the sake of simplicity, this application specifically discloses only some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, and similarly any upper limit can be combined with any other upper limit to form a range not explicitly recited. In addition, each individually disclosed point or single numerical value itself can be used as a lower limit or an upper limit and combined with any other point or single numerical value or combined with other lower limits or upper limits to form a range not explicitly recited.

[0015] In this application, terms indicating directions or positional relationships such as "upper", "lower", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings. This is only for convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation on the utility model. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0016] In this application, unless otherwise clearly specified and defined, the terms "installed", "set", "connected" shall be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, and can also be the communication inside two elements. For those skilled in the art, the specific meanings of the above terms in this utility model can be understood according to specific circumstances.

[0017] Unless otherwise specified, the terms used in this application have the well-known meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values of the various parameters mentioned in this application can be measured by various common measurement methods in the art (for example, it can be tested according to the methods given in the embodiments of this application).

[0018] The following further elaborates this application in combination with specific embodiments. It should be understood that these specific embodiments are only used to illustrate this application and not to limit the scope of this application.

[0019] I. Bottom guard plate of battery pack

[0020] The first aspect of this application provides a bottom guard plate of a battery pack, including a metal plate, a first electrophoretic layer on the first surface of the metal plate, and a second electrophoretic layer on the second surface of the metal plate. A coating is provided on the surface of the first electrophoretic layer away from the metal plate. The coating is a solvent-based coating or a solvent-free coating. The thickness of the coating is 200 μm - 900 μm, and the surface roughness of the coating ≤ 20 μm. The applicant has found that by matching the specific thickness and specific surface roughness of the solvent-based coating or the solvent-free coating, the wear resistance of the battery pack coating can be improved, and the number of turnover times of the battery pack in the battery swapping station can be increased.

[0021] In this application, a "solvent-based coating" refers to a coating formed by curing a solvent-based paint. The solvent-based paint is a liquid paint at room temperature that contains volatile organic solvents as a dispersion medium. During the curing process of the paint, the organic solvents volatilize to form the coating.

[0022] In this application, a "solvent-free coating" refers to a coating formed by curing a solvent-free paint. The solvent-free paint is a liquid paint at room temperature that basically does not contain volatile organic solvents.

[0023] In this application, "abrasion resistance" refers to the ability of the coating surface to resist wear and is a measure of the durability of a material. "Abrasion-resistant" means that the coating is not easily worn under high-frequency friction and there will be no phenomena such as thinning of the surface thickness or peeling of the coating layer.

[0024] In this application, the "number of turnovers in the battery swapping station" refers to the number of times the battery pack completes round trips between the battery storage and the battery swapping platform through the battery transfer and transportation system in the battery swapping station. Here, the "battery transfer and transportation system" is used to transfer the battery between the battery swapping station platform and the battery storage, the "battery swapping platform" is used for vehicle positioning and battery swapping operations, and the "battery storage" is used for battery storage and charging. Taking the second-generation NIO battery swapping station as an example, one turnover in the battery swapping station means that the battery pack makes a round trip through the buffer position, connection position, lifting position, and battery storage in the battery swapping station once.

[0025] In some embodiments, the thickness of the coating is exemplarily 200μm, 220μm, 250μm, 280μm, 300μm, 320μm, 350μm, 380μm, 400μm, 420μm, 450μm, 480μm, 500μm, 520μm, 550μm, 580μm, 600μm, 650μm, 700μm, 750μm, 800μm, 850μm, 900μm or a range composed of any two of these values. If the thickness of the coating is too large, it will increase the usage amount of the coating material, resulting in increased costs, and will also increase the overall package weight, which is not conducive to lightweighting. If the thickness is too small, it will reduce the mechanical strength and wear resistance of the bottom of the battery pack, easily expose the battery pack bottom plate, and thus affect the safety and reliability of the battery. In some embodiments, the thickness of the coating is 300μm - 600μm. In some embodiments, the thickness of the coating is 300μm - 550μm. In this application, those skilled in the art can adjust process parameters such as paint concentration, paint viscosity, coating method, and coating speed to control the thickness of the coating according to the selected solvent-based or solvent-free paint type.

[0026] In some embodiments, the surface roughness of the coating is exemplarily 20μm, 19μm, 18μm, 17μm, 16μm, 15μm, 14μm, 13μm, 12μm, 11μm, 10μm, 9μm, 8μm, or a range composed of any two of these values. If the surface roughness of the coating is too small, the battery pack is more likely to slip during transfer in the battery swapping station, resulting in a decrease in transfer efficiency. If the surface roughness is too large, the coating is more likely to be subject to external friction, scratching, or abrasion, which is not conducive to improving the wear resistance of the coating. In some embodiments, the surface roughness of the coating is 10μm - 20μm. In some embodiments, the surface roughness of the coating is 15μm - 20μm. In the present application, those skilled in the art can adjust the surface roughness of the coating by adjusting the types of solvent-based or solvent-free coatings, coating temperature, coating thickness, and post-treatment means of the coating such as grinding and polishing.

[0027] In some embodiments, the coating is a solvent-based or solvent-free coating of an epoxy coating, a polyurea coating, or an acrylic coating. In some embodiments, the coating is a solvent-based epoxy coating, a solvent-free polyurea coating, or a solvent-based acrylic coating. In a preferred embodiment, the coating is a solvent-based epoxy coating to further improve the wear resistance of the bottom guard plate and extend the service life of the battery pack.

[0028] In some embodiments, the metal plate is a steel plate or an aluminum alloy.

[0029] In some embodiments, the metal plate is a steel plate. Compared with other metal plates, the steel plate has better tensile strength and elongation, can meet the requirements of impact resistance, is conducive to improving the protection of the battery pack, and thus extends the service life of the battery.

[0030] In some embodiments, the first electrophoretic layer is an acrylic electrophoretic paint layer, an acrylate electrophoretic paint layer, an epoxy electrophoretic paint layer, a polyurethane electrophoretic paint layer, or a polyester electrophoretic paint layer. In a preferred embodiment, the first electrophoretic layer is an epoxy electrophoretic paint layer. The first electrophoretic layer acts as a protective layer to effectively isolate the metal plate from the external environment of the battery pack, protecting the metal plate from environmental erosion, especially when the solvent-based or solvent-free coating is damaged, protecting the metal plate from the external environment, thereby extending the service life of the battery pack. At the same time, the first electrophoretic layer can increase the adhesion between the solvent-based or solvent-free coating and the metal plate, making the solvent-based or solvent-free coating not easily fall off when subjected to external friction or scratching.

[0031] In some embodiments, the thickness of the first electrophoresis layer is 25 μm - 60 μm, exemplarily 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, or a range composed of any two of these values. In some embodiments, the thickness of the first electrophoresis layer is 25 μm - 35 μm.

[0032] In some embodiments, the second electrophoresis layer is an acrylic electrophoresis paint layer, an acrylate electrophoresis paint layer, an epoxy electrophoresis paint layer, a polyurethane electrophoresis paint layer, or a polyester electrophoresis paint layer. In a certain preferred embodiment, the second electrophoresis layer is an epoxy electrophoresis paint layer. The second electrophoresis layer serves as a protective layer to effectively isolate the metal plate from the internal environment of the battery pack, protecting the metal plate from erosion, thereby enhancing the service life of the battery pack.

[0033] In some embodiments, the thickness of the second electrophoresis layer is 25 μm - 60 μm, exemplarily 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, or a range composed of any two of these values. In some embodiments, the thickness of the second electrophoresis layer is 25 μm - 35 μm.

[0034] In some embodiments, the bottom guard plate of the battery pack includes the metal plate, a first electrophoresis layer on the first surface of the metal plate, and a second electrophoresis layer on the second surface of the metal plate. A coating is provided on the surface of the first electrophoresis layer away from the metal plate. The coating is a solvent-based or solvent-free coating of epoxy, polyurea, or acrylic. The thickness of the coating is 200 μm - 900 μm, the surface roughness of the coating is ≤ 20 μm, the thickness of the first electrophoresis layer is 25 μm - 60 μm, and the thickness of the second electrophoresis layer is 25 μm - 60 μm.

[0035] In some embodiments, the bottom guard plate of the battery pack includes the metal plate, a first electrophoresis layer on the first surface of the metal plate, and a second electrophoresis layer on the second surface of the metal plate. A coating is provided on the surface of the first electrophoresis layer away from the metal plate. The coating is a solvent-based or solvent-free coating of epoxy, polyurea, or acrylic. The thickness of the coating is 300 μm - 600 μm, the surface roughness of the coating is 10 μm - 20 μm, the thickness of the first electrophoresis layer is 25 μm - 60 μm, and the thickness of the second electrophoresis layer is 25 μm - 60 μm.

[0036] In some embodiments, the bottom guard plate of the battery pack includes the metal plate, a first electrophoretic layer on the first surface of the metal plate, and a second electrophoretic layer on the second surface of the metal plate. A coating is provided on the surface of the first electrophoretic layer away from the metal plate. The coating is a solvent-based epoxy coating or a solvent-free coating. The thickness of the coating is 400μm - 600μm, the surface roughness of the coating is 10μm - 20μm, the thickness of the first electrophoretic layer is 25μm - 60μm, and the thickness of the second electrophoretic layer is 25μm - 60μm.

[0037] In some embodiments, the thickness of the metal plate is 0.7mm - 1.5mm, and exemplarily it is 0.7mm, 0.9mm, 1.1mm, 1.3mm, 1.5mm, or the range formed by any two of these values. In some embodiments, the thickness of the metal plate is 0.8mm - 1mm.

[0038] In some embodiments, the thickness of the bottom guard plate of the battery pack is 0.7mm - 1.5mm, and exemplarily it is 0.7mm, 0.9mm, 1.1mm, 1.3mm, 1.5mm, or the range formed by any two of these values. In some embodiments, the thickness of the bottom guard plate of the battery pack is 0.8mm - 1mm.

[0039] In some embodiments, the pressure on the coating is 10g / mm 2 -20g / mm 2 , and exemplarily it is 10g / mm 2 , 12g / mm 2 , 14g / mm 2 , 16g / mm 2 , 18g / mm 2 , 20g / mm 2 or the range formed by any two of these values. When the battery pack is being swapped, the bottom guard plate needs to bear the pressure of the entire battery pack. Correspondingly, the coating on the bottom guard plate also needs to bear the pressure of the entire battery pack. Otherwise, phenomena such as cracking, breakage, and peeling of the coating will occur.

[0040] II. Battery Pack

[0041] The second aspect of the present application provides a battery pack, which includes the bottom guard plate of the battery pack as described in the first aspect, and the coating is provided on the outer surface of the battery pack. The solvent-based or solvent-free coating is provided on the outer surface of the battery pack to improve the ability of the battery pack to resist continuous scratching and friction in the external environment, increase the number of turnovers of the battery pack at the swapping station, and at the same time, as a protective layer, it can protect the metal plate from the erosion of the external environment and extend the service life of the battery pack.

[0042] In some embodiments, the battery pack includes the battery pack bottom guard plate as described in the first aspect, the coating is disposed on the outer surface of the battery pack, and the second electrophoresis layer is disposed on the inner surface of the battery pack. The second electrophoresis layer is disposed on the inner surface of the battery pack to resist the erosion of the internal environment of the battery pack, such as the erosion of water, acid, alkali, and salt inside the battery pack, thereby further enhancing the service life of the battery pack.

[0043] III. Vehicle

[0044] The third aspect of the present application provides a vehicle, which includes the battery pack as described in the second aspect, and the battery pack is installed in the vehicle. In some embodiments, the battery pack is installed at the bottom of the vehicle. In the installed state of the battery pack, the battery pack bottom guard plate is arranged towards the ground direction.

[0045] In some embodiments, the battery pack is installed on the chassis of the vehicle, and the battery pack bottom guard plate is arranged away from the chassis.

[0046] In some embodiments, the vehicle is a vehicle that can be battery-swapped. In the present application, a vehicle that can be battery-swapped generally refers to all vehicles that support the battery-swapping function. In some embodiments, the vehicle has a structure for replacing the battery pack.

[0047] In some embodiments, the vehicle includes, but is not limited to: electric vehicles, hybrid electric vehicles, and plug-in hybrid electric vehicles.

[0048] Examples

[0049] In the present application, for the methods in the examples, unless otherwise specified, they are all conventional methods in the art; for the raw materials, materials, and reagents in the examples, unless otherwise specified, they are all conventional raw materials, materials, or reagents that are commercially available.

[0050] Testing Methods

[0051] 1. Thickness Measurement

[0052] A film thickness gauge is used to measure the thickness of the solvent-based coating, solvent-free coating, and electrophoresis layer.

[0053] A vernier caliper is used to measure the thickness of the battery pack bottom guard plate.

[0054] 2. Coating Surface Roughness Measurement

[0055] A 3D profilometer VR-6000 is used to measure the surface roughness of the solvent-based coating and solvent-free coating at a magnification of 50 times, and the data of the arithmetic mean height Sa is taken as the surface roughness value. The Z-direction measurement accuracy is 0.4 μm, and the X-direction and Y-direction measurement accuracies are 0.5 μm.

[0056] 3. Coating Rotation Abrasion Test (Taber Test)

[0057] Cut the bottom protection plates of the battery packs in each example and comparative example into rectangular specimens of 100 mm × 100 mm. Test the abrasion resistance of the solvent-based coating and the solvent-free coating with an abrasion testing machine at room temperature of 23°C ± 2°C and relative humidity of 50% ± 5%. Prepare at least 3 specimens for each example and comparative example for testing, and take the average value of the test results. The test method refers to GB / T 1768 Determination of Abrasion Resistance of Paints and Varnishes - Rotating Rubber Wheel Method.

[0058] The parameters of the grinding wheel and abrasion testing machine used in the test simulate the actual situation of NIO battery swap stations. The grinding wheel used is a polyurethane grinding wheel, the rotation radius of the grinding wheel is set to 28.25 mm, the rotation speed of the grinding wheel is set to 72 r / min, the thickness of the grinding wheel is set to 8 mm, the single-wheel load is set to 2 kg, and the Shore hardness D of the grinding wheel is 28 - 38. Every 1000 revolutions of the grinding wheel, check the wear of the solvent-based coating or the solvent-free coating inside the standard light source color matching lamp box. If it is not worn through, measure the film thickness at 3 points of the friction mark with a dry film thickness gauge and record it, and weigh the film weight with an electronic balance, and then continue the test.

[0059] Stop the test (whichever comes first) after the grinding wheel runs 30000 revolutions or the coating is worn through. Record the reduction in coating thickness and coating weight of the solvent-based coating or the solvent-free coating. The thickness is accurate to 1 μm, and the weight is accurate to 0.001 g. If the coating is not worn through after the grinding wheel runs 30000 revolutions, record the coating thickness and coating weight abrasion after running 30000 revolutions. If the coating is worn through after the grinding wheel runs 5000 revolutions, record the coating thickness and coating weight abrasion after running 5000 revolutions. "Worn through" here means exposing the electrophoretic layer or metal plate under the solvent-based coating or the solvent-free coating.

[0060] Since the above abrasion test simulates the actual situation of the battery swap station, if the coating on the bottom protection plate is not worn through after running 30000 revolutions, it can be approximately considered that the coating on the battery pack containing this bottom protection plate is not worn through after 1500 rotations in the battery swap station, which is equivalent to extending the service life of the battery pack to 15 years.

[0061] 4. Corrosion Resistance Test

[0062] Test the corrosion resistance of the solvent-based coating and the solvent-free coating of the bottom protection plates of the battery packs in each example and comparative example, including water resistance test, acid resistance test, alkali resistance test, and neutral salt spray test.

[0063] Among them, the water resistance test method refers to ASTM D870. The test temperature is 38°C ± 0.2°C, and the test time is 144 h. If there is no significant discoloration, softening, swelling, blistering, peeling of the coating after 144 h of testing, and the adhesion in the cross-cut test is grade 0, it is considered that the coating passes the water resistance test; otherwise, it fails. The acid resistance test and alkali resistance test methods refer to GB / T 9274. The test uses a sulfuric acid (H2SO4) solution with a concentration of 0.05 mol / L or a sodium hydroxide (NaOH) solution with a concentration of 0.1 mol / L. If there is no significant discoloration, softening, swelling, blistering, peeling of the coating after 48 h of testing, and the adhesion in the cross-cut test is grade 0, it is considered that the coating passes the acid resistance test or alkali resistance test; otherwise, it fails. The neutral salt spray test method refers to GB / T 10125. If there is no blistering, peeling of the coating after 1000 h of testing, the unilateral diffusion distance at the scratch is ≤ 2 mm, and the adhesion in the cross-cut test is grade 0, it is considered that the coating passes the neutral salt spray test; otherwise, it fails.

[0064] If the coating passes the water resistance test, acid resistance test, alkali resistance test, and neutral salt spray test simultaneously, it is considered that the coating passes the corrosion resistance test; otherwise, it fails.

[0065] 5. High and low temperature adhesion test

[0066] After storing the battery pack bottom guard plates of each example and comparative example at -40°C for 1 h, the adhesion of the coating is tested by cross-cutting. If the adhesion is grade 0, it is considered that the coating passes the low temperature adhesion test; otherwise, it fails.

[0067] After storing the battery pack bottom guard plates of each example and comparative example at 60°C for 3 h, the adhesion of the coating is tested by cross-cutting. If the adhesion is grade 0, it is considered that the coating passes the high temperature adhesion test; otherwise, it fails.

[0068] 6. High and low temperature impact resistance test

[0069] Cut the battery pack bottom guard plates of each example and comparative example into rectangular specimens of 150 mm × 60 mm, bake them at 80°C for 30 min, then leave them for 24 h. After that, put the test panels into a programmable constant temperature and humidity test chamber at -40°C and keep them for 1 h before performing the impact resistance test. The test conditions are as follows: punch diameter 8 mm, groove diameter (15 ± 3) mm, weight of the hammer 1000 g, impact height 50 cm. If there is no falling off of the coating, no cracks, and no peeling phenomenon after the impact resistance test, it is considered that the coating passes the low temperature adhesion test; otherwise, it fails.

[0070] Cut the bottom protection plates of each example and comparative example into rectangular specimens of 150 mm × 60 mm, bake them at 60 °C for 3 h, then leave them for 24 h, and then conduct an impact resistance test. The test conditions are as follows: punch diameter 8 mm, groove diameter (15 ± 3) mm, weight of the hammer 1000 g, impact height 50 cm. If the coating does not fall off the bottom, and there are no cracks or peeling phenomena after the impact resistance test, it is considered that the coating passes the high-temperature adhesion test; otherwise, it fails.

[0071] 7. Low-temperature and high-temperature flexibility test

[0072] Cut the bottom protection plates of each example and comparative example into rectangular specimens of 150 mm × 60 mm, bake them at 80 °C for 30 min, then leave them for 24 h. Then, place the test panel in a programmable constant temperature and humidity test machine at -40 °C for 1 h. After taking out the test panel, immediately bend the test panel 180° along a mandrel with a diameter of 25 mm within 1 s with the solvent-based coating or solvent-free coating facing outwards, and check the crack situation at the bottom. If there are no cracks or peeling phenomena in the coating, it is considered that the coating passes the low-temperature flexibility test; otherwise, it fails.

[0073] Cut the bottom protection plates of each example and comparative example into rectangular specimens of 150 mm × 60 mm, bake them at 60 °C for 30 min, then leave them for 24 h. Then, bend the test panel 180° along a mandrel with a diameter of 25 mm within 1 s with the solvent-based coating or solvent-free coating facing outwards, and check the crack situation at the bottom. If there are no cracks or peeling phenomena in the coating, it is considered that the coating passes the high-temperature flexibility test; otherwise, it fails.

[0074] Example 1

[0075] The structural schematic diagram of the bottom protection plate of the battery pack in this example is as Figure 1 shown, including a metal plate 1 as the bottom plate, a first electrophoretic layer 21 provided on the first surface of the metal plate 1, and a second electrophoretic layer 22 provided on the second surface of the metal plate 1. A solvent-free coating 31 is provided on the surface of the first electrophoretic layer 21 away from the metal plate 1. Among them, the metal plate is made of steel, the first electrophoretic layer is made of an epoxy electrophoretic paint layer, the second electrophoretic layer is made of an epoxy electrophoretic paint layer, and the solvent-free coating is made of a solvent-free polyurea coating. The thickness data of the first electrophoretic layer, the second electrophoretic layer, and the solvent-free coating, as well as the surface roughness data, are shown in Table 1 in detail. The overall thickness of the bottom protection plate of the battery pack is 0.8 mm - 1 mm.

[0076] When preparing the bottom guard plate of the battery pack, epoxy electrophoresis is first carried out on the front and back surfaces of the steel plate, and after baking, the bottom guard plate substrate is obtained, that is, a steel plate with epoxy electrophoretic paint on both the first surface and the second surface. The dry film thickness of both the first electrophoretic layer and the second electrophoretic layer is 30 μm. The back surface of the bottom guard plate substrate is shielded with masking tape, and a solvent-free polyurea coating is sprayed on the first surface of the bottom guard plate substrate. After drying, the masking tape on the back surface is removed to obtain the bottom guard plate of the battery pack, where the thickness of the solvent-free polyurea coating is 300 μm and the surface roughness Sa is 18.8 μm.

[0077] Example 2

[0078] The structural schematic diagram of the bottom guard plate of the battery pack in this example is as Figure 2 shown, and it includes a metal plate 1 as the bottom plate, a first electrophoretic layer 21 provided on the first surface of the metal plate 1, and a second electrophoretic layer 22 provided on the second surface of the metal plate 1. A solvent-based coating 32 is provided on the surface of the first electrophoretic layer 21 away from the metal plate 1. Among them, the metal plate uses a steel plate, the first electrophoretic layer uses an epoxy electrophoretic paint layer, the second electrophoretic layer uses an epoxy electrophoretic paint layer, and the solvent-based coating uses a solvent-based epoxy coating. The thickness data of the first electrophoretic layer, the second electrophoretic layer, and the solvent-based coating, as well as the surface roughness, are shown in Table 1 in detail. The overall thickness of the bottom guard plate of the battery pack is 0.8 mm - 1 mm.

[0079] When preparing the bottom guard plate of the battery pack, epoxy electrophoresis is first carried out on the front and back surfaces of the steel plate, and after baking, the bottom guard plate substrate is obtained, that is, a steel plate with epoxy electrophoretic paint on both the first surface and the second surface. The dry film thickness of both the first electrophoretic layer and the second electrophoretic layer is 30 μm. The back surface of the bottom guard plate substrate is shielded with masking tape, and a solvent-based epoxy coating is sprayed on the first surface of the bottom guard plate substrate. After drying, the masking tape on the back surface is removed to obtain the bottom guard plate of the battery pack, where the thickness of the solvent-based epoxy coating is 543 μm and the surface roughness Sa is 16.5 μm.

[0080] Example 3

[0081] The structural schematic diagram of the bottom guard plate of the battery pack in Example 3 is as Figure 2 shown, and the overall thickness of the bottom guard plate of the battery pack is 0.8 mm - 1 mm. The bottom guard plate of the battery pack in Example 3 is based on Example 2, and the thickness and surface roughness of the solvent-based epoxy coating are adjusted by changing the spraying process conditions and parameters. The specific adjusted data are shown in Table 1.

[0082] Example 4

[0083] The structural schematic diagram of the bottom guard plate of the battery pack in this example is as Figure 2As shown in the figure, it includes a metal plate 1 as the bottom plate, a first electrophoretic layer 21 provided on the first surface of the metal plate 1, and a second electrophoretic layer 22 provided on the second surface of the metal plate 1. A solvent-based coating 31 is provided on the surface of the first electrophoretic layer 21 away from the metal plate 1. Among them, the metal plate is a steel plate, the first electrophoretic layer is an epoxy electrophoretic paint layer, the second electrophoretic layer is an epoxy electrophoretic paint layer, and the solvent-based coating is a solvent-based acrylic coating. The thickness data of the first electrophoretic layer and the second electrophoretic layer, as well as the thickness and surface roughness of the solvent-based coating, are shown in Table 1 in detail. The overall thickness of the battery pack bottom guard plate is 0.8 mm - 1 mm.

[0084] When preparing the battery pack bottom guard plate, first electrophorese epoxy on the front and back surfaces of the steel plate, and after baking, obtain the bottom guard plate substrate, that is, a steel plate with epoxy electrophoretic paint on both the first surface and the second surface. The dry film thickness of both the first electrophoretic layer and the second electrophoretic layer is 30 μm. Mask the back surface of the bottom guard plate substrate with masking tape, spray solvent-based acrylic paint on the first surface of the bottom guard plate substrate, and after drying, remove the masking tape on the back surface to obtain the battery pack bottom guard plate, where the thickness of the solvent-based acrylic coating is 440 μm and the surface roughness Sa is 14.2 μm.

[0085] Comparative Example 1

[0086] The structural schematic diagram of the battery pack bottom guard plate in this comparative example is as Figure 2 As shown in the figure, it includes a metal plate 1 as the bottom plate, a first electrophoretic layer 21 provided on the first surface of the metal plate 1, and a second electrophoretic layer 22 provided on the second surface of the metal plate 1. A solvent-based coating 32 is provided on the surface of the first electrophoretic layer 21 away from the metal plate 1. Among them, the metal plate is a steel plate, the first electrophoretic layer is an epoxy electrophoretic paint layer, the second electrophoretic layer is an epoxy electrophoretic paint layer, and the solvent-based coating is a solvent-based polyvinyl chloride (PVC) coating. The thickness data of the first electrophoretic layer and the second electrophoretic layer, as well as the thickness and surface roughness of the solvent-based coating, are shown in Table 1 in detail. The overall thickness of the battery pack bottom guard plate is 0.8 mm - 1 mm.

[0087] When preparing the battery pack bottom guard plate, first electrophorese epoxy on the front and back surfaces of the steel plate, and after baking, obtain the bottom guard plate substrate, that is, a steel plate with epoxy electrophoretic paint on both the first surface and the second surface. The dry film thickness of both the first electrophoretic layer and the second electrophoretic layer is 30 μm. Mask the back surface of the bottom guard plate substrate with masking tape, spray solvent-based PVC paint on the first surface of the bottom guard plate substrate, and after drying, remove the masking tape on the back surface to obtain the battery pack bottom guard plate, where the thickness of the solvent-based PVC coating is 996 μm and the surface roughness Sa is 56.4 μm.

[0088] Comparative Example 2

[0089] The structural schematic diagram of the battery pack bottom guard plate in Comparative Example 2 is as Figure 2As shown, the overall thickness of the bottom guard plate of the battery pack is 0.8 mm - 1 mm. The bottom guard plate of Comparative Example 2 adjusts the thickness and surface roughness of the solvent-based PVC coating by changing the spraying process conditions and parameters on the basis of Comparative Example 1. The specific adjustment data are shown in Table 1.

[0090] Table 1

[0091]

[0092]

[0093] Table 2 records the test results of the rotational abrasion @30,000 revolutions of the bottom guard plate coatings of each example and comparative example. It can be seen that the bottom guard plate coatings of Examples 1 - 4 of the present utility model have lower abrasion amounts compared to the PVC coatings of Comparative Examples 1 - 2, showing excellent wear resistance.

[0094] Table 2

[0095]

[0096] Table 3 records the test results of the corrosion resistance, high and low temperature adhesion, high and low temperature impact resistance, and high and low temperature flexibility of the bottom guard plate coatings of each example and comparative example. It can be seen that the bottom guard plate coatings of Examples 1 - 4 and Comparative Examples 1 - 2 of the present utility model have all passed the corrosion resistance test, high and low temperature adhesion test, high and low temperature impact resistance test, and high and low temperature flexibility test, and can completely replace the PVC coating.

[0097] Table 3

[0098]

[0099]

[0100] Although some exemplary embodiments of the present application have been illustrated and described, the present application is not limited to the disclosed embodiments. On the contrary, those of ordinary skill in the art will recognize that some modifications and changes can be made to the described embodiments without departing from the spirit and scope of the present application as described in the appended claims.

Claims

1. A battery pack bottom guard plate, characterized in that, It includes a metal plate, a first electrophoresis layer located on the first surface of the metal plate, and a second electrophoresis layer located on the second surface of the metal plate. A coating is provided on the surface of the first electrophoresis layer away from the metal plate. The coating is a solvent-based coating or a solvent-free coating. The thickness of the coating is 200μm - 900μm, and the surface roughness of the coating is ≤20μm.

2. The bottom protection plate of the battery pack according to claim 1, characterized in that The thickness of the coating is 300μm - 600μm.

3. The bottom protection plate of the battery pack according to claim 1 or 2, characterized in that The surface roughness of the coating is 10μm - 20μm.

4. The bottom protection plate of the battery pack according to claim 1 or 2, characterized in that The coating is an epoxy coating, a polyurea coating or an acrylic coating.

5. The bottom protection plate of the battery pack according to claim 4, characterized in that, The coating is the epoxy coating.

6. The bottom protection plate of the battery pack according to claim 5, characterized in that, The thickness of the epoxy coating is 400μm - 600μm, and the surface roughness of the epoxy coating is 10μm - 20μm.

7. The bottom protection plate of the battery pack according to claim 1 or 2, characterized in that, The thickness of the first electrophoresis layer is 25μm - 60μm, and / or the thickness of the second electrophoresis layer is 25μm - 60μm.

8. A battery pack, comprising the battery pack bottom guard plate according to any one of claims 1 - 7, wherein the coating is provided on the outer surface of the battery pack.

9. A vehicle, comprising the battery pack according to claim 8, wherein the battery pack is installed in the vehicle.

10. The vehicle according to claim 9, wherein The vehicle has a structure for replacing the battery pack.

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