Battery pack bottom protection plate and preparation method thereof

Abstract

The invention discloses a battery pack bottom protection plate and a preparation method thereof.The battery pack bottom protection plate comprises a first protection layer, an anti-impact layer and a second protection layer, and the anti-impact layer is arranged between the first protection layer and the second protection layer; the first protective layer and the second protective layer respectively comprise a continuous fiber reinforced bio-based high-temperature polyamide composite material. Therefore, the battery pack bottom protection plate has excellent mechanical properties, and the risk that the battery protection bottom plate is impacted to be layered and hollow is reduced.

Description

Technical Field

[0001] The present invention relates to the field of composite protective plates, and in particular to a battery pack bottom protective plate and a preparation method thereof. Background Art

[0002] With the rapid development of electric vehicles, people have higher and higher safety requirements for electric vehicles. As the power source of electric vehicles, the safety of power battery packs is self-evidently important. In electric vehicles, the battery pack is generally located at the bottom of the vehicle chassis and connected to the chassis by bolts. The lower surface of the battery pack is exposed. During daily driving of the vehicle, the bottom of the battery pack is easily bumped, resulting in the failure of the box body to break and the protection. During driving, stones splashing from the bottom will also cause impact on the battery pack. In order to cope with complex working conditions, a protective plate is usually set at the bottom of the battery pack to protect the bottom of the battery pack.

[0003] Traditionally, the bottom guard plate of the battery pack of electric vehicles is made of fiberglass or stainless steel, but the fiberglass preparation process is not environmentally friendly and cannot be recycled after forming. Traditional steel has a high specific gravity and cannot meet the lightweight requirements of electric vehicles. In addition, it is difficult to effectively compound steel plates with other non-metallic materials, which also limits the formation of high-performance composite materials by compounding steel plates with other non-metallic materials. Summary of the invention The present invention aims to solve one of the technical problems existing in the prior art. To this end, the present invention proposes a battery pack bottom guard plate and a preparation method thereof. In one aspect of the present invention, a battery pack bottom protective plate is proposed, comprising a first protective layer, an impact-resistant layer and a second protective layer, wherein the impact-resistant layer is between the first protective layer and the second protective layer, and the first protective layer and the second protective layer both comprise continuous fiber reinforced bio-based high-temperature polyamide composite materials. In some embodiments, the continuous fiber reinforced bio-based high temperature polyamide composite material includes a bio-based copolyamide material and continuous fibers. For details, reference may be made to the composite material and preparation method described in the patent publication CN115536876A. In some embodiments, the impact-resistant layer is a metal plate, and the metal plate is preferably a steel plate. In some embodiments, the thickness of the first protective layer and the second protective layer are independently 0.5-1 mm, for example, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, etc. In some embodiments, the thickness of the metal plate is 0.5-1.5 mm, for example, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, etc. In a second aspect of the present invention, the present invention provides a method for preparing the battery pack bottom guard plate described in the first aspect, the method comprising: (1) cross-laying the prepreg tapes and then performing molding to obtain a first protective layer and a second protective layer respectively; (2) Preheating the first protective layer and the second protective layer, placing the metal plate between the preheated first protective layer and the second protective layer, and then performing secondary molding to obtain the battery pack bottom protective plate. In some embodiments, in step (1), the prepreg tape includes a bio-based copolyamide material and continuous fibers, and can be prepared according to the method for preparing a composite material disclosed in patent publication CN115536876A. In some embodiments, in step (1), the cross-laying refers to the cross-laying of the layers at a certain angle to meet the principle of balanced and symmetrical laying, such as 0° / 90° cross-laying, 45° / 45° cross-laying, etc. In some embodiments, in step (1), the temperature of the primary molding is 310-320° C., and the pressure is 10-13 MPa. In some embodiments, in step (2), the metal plate is pretreated before being placed between the preheated first protective layer and the second protective layer, and the pretreatment includes: immersing the metal plate in a 70-80wt% sulfuric acid solution for 5-10 minutes, and then transferring it to a 35-45wt% amine compound aqueous solution for immersion for 5-10 minutes to obtain a pretreated metal plate. The inventors found that by immersing the metal plate in a sulfuric acid solution, a double-textured rough structure can be formed on the surface of the metal plate, and small irregular nanopores can be formed on the inner wall of the depression and the surface of the metal plate. The metal plate treated with sulfuric acid is then immersed in an amine compound solution, and the amine compound enters the nanopore structure. In the subsequent secondary molding process, the amine compound reacts with polyamide, thereby improving the bonding strength between the bio-based high-temperature polyamide material and the metal plate, and reducing the risk of delamination and hollowing of the battery protective bottom plate due to impact. In some embodiments, the amine compound includes at least one of dimethylamine, diethylamine, and dipropylamine. In some embodiments, in step (2), the preheating temperature is 300-320° C., preferably 310° C., and the preheating time is 90-120 s, preferably 90 s. In some embodiments, in step (2), the secondary molding temperature is 130-150° C., preferably 150° C., the pressure is 10-15 MPa, preferably 13-15 MPa, and the time is 60-120 min. The beneficial effects of the present invention are: (1) The present application uses bio-based high-temperature polyamide composite materials as raw materials, and the monomer pentamethylenediamine in the raw materials is prepared by biological fermentation, which can effectively reduce the use of fossil raw materials and reduce carbon emissions; (2) The first protective layer and the second protective layer of the present application are made of bio-based high temperature resistant polyamide composite materials, which have excellent mechanical properties and can significantly improve the impact resistance of the battery pack bottom guard plate; (3) The present application adopts a sandwich structure of a first protective layer, an anti-impact layer, and a second protective layer, and pre-treats the anti-impact layer to improve the bonding ability between the protective layer and the anti-impact layer, thereby reducing the risk of delamination and hollowing of the bottom protective plate of the battery pack due to impact. Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. DETAILED DESCRIPTION The present invention is further described below in conjunction with preferred embodiments and comparative examples. It should be noted that the described embodiments are only representative embodiments and cannot represent all embodiments. The content described below is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention. The scheme of the present invention will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Where specific techniques or conditions are not indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used are not indicated by the manufacturer and are all conventional products that can be obtained commercially. The steel plate grade is DP780, purchased from Shanghai Baosteel Shanghai Baosteel, PA66 resin (melting point is 220℃, relative viscosity is 2.7) was purchased from Pingdingshan Shenma Engineering Plastics Co., Ltd., antioxidant was purchased from BASF Group of Germany; lubricant WAX-C was purchased from Clariant of Germany; coupling agent was purchased from Hangzhou Jessica Chemical Co., Ltd.; continuous long glass fiber was purchased from Owens Corning (OC), specification is 1200Tex; flow modifier MF-3332 was purchased from Beijing Weisheng Hongda Technology Co., Ltd., black masterbatch was purchased from Cabot, Araldite 420 epoxy resin was purchased from Huntsman Group of the United States; PP was purchased from LG Chemical of South Korea. Preparation Example Prepreg tape A (PA56T): (1) Raw materials and preparation methods refer to comparative example 4 of the patent publication CN 112029090A, and bio-based high temperature polyamide A (number average molecular weight of 30,000, relative viscosity of 2.7, water content of 850 ppm after drying, melting point of 282° C.) is obtained; (2) according to 93wt% of bio-based high temperature polyamide A, 0.5wt% of antioxidant 1098, 0.5wt% of coupling agent KH570, 0.4wt% of lubricant WAX-C, 1.5wt% of flow modifier MF-3332, and 2wt% of black masterbatch, the above components are added into a high-speed mixer and mixed to obtain bio-based high temperature polyamide material A; (3) A composite material A, namely, prepreg tape A, was prepared by referring to the method of patent publication CN115536876A, wherein the weight fraction ratio of the bio-based copolyamide material A to the continuous long glass fiber was 35:65. Prepreg tape B (PA512T): (1) Using 10.2 mol of bio-based pentamethylenediamine, 2.9 mol of dodecanedioic acid and 6.9 mol of terephthalic acid as raw materials, the preparation method is as shown in Example 7 of the patent publication CN 112029090A, and a bio-based high temperature polyamide B (number average molecular weight of 25,800, relative viscosity of 2.43, water content of 690 ppm after drying, melting point of 302° C.) is obtained; (2) according to 91.4wt% of bio-based high temperature polyamide B, 0.5wt% of antioxidant 1098, 0.5wt% of coupling agent KH570, 0.4wt% of lubricant WAX-C, 1.5wt% of flow modifier MF-3332, and 2wt% of black masterbatch, the above components are added into a high-speed mixer and mixed to obtain bio-based high temperature polyamide material B; (3) A composite material B, namely, prepreg tape B, was prepared by referring to the method of patent publication CN115536876A, wherein the weight fraction ratio of bio-based copolyamide material B and continuous long glass fiber was 40:60. Prepreg tape C (PA5T66): (1) 7.05 mol of bio-based pentamethylenediamine, 7 mol of terephthalic acid, 3 mol of 1,6-hexanediamine, 3 mol of 1,6-hexanediamine, 0.03 wt% of sodium hypophosphite and water were mixed uniformly, the stirring speed was set to 80 rpm, the temperature was raised to 80°C in a nitrogen atmosphere and maintained at this temperature for 1 hour to obtain a 50 wt% polyamide salt solution, the temperature was raised to 130°C, the water was drained and concentrated to a concentration of 65 wt%; the temperature was raised to 240°C again, the pressure was maintained at 2.5 MPa and reacted for 1 hour; the pressure in the reaction system was reduced to 0 MPa by draining and reducing the pressure, and the temperature of the reaction system was 340°C after the pressure reduction was completed; the vacuum was evacuated to -0.08 MPa and maintained for 40 seconds to obtain a polyamide melt; the polyamide melt was water-cooled and pelletized to obtain a bio-based high-temperature polyamide C (number average molecular weight of 21,000, relative viscosity of 2.23, water content of 1045 ppm after drying, and melting point of 308°C); (2) according to 90.3wt% of bio-based high temperature polyamide C, 0.5wt% of antioxidant, 0.5wt% of coupling agent KH570, 0.4wt% of lubricant WAX-C, 1.8wt% of flow modifier MF-3332, and 2wt% of black masterbatch, the above components are added into a high-speed mixer and mixed to obtain bio-based high temperature polyamide material C; (3) A composite material C, namely, prepreg tape C, was prepared by referring to the method of patent publication CN115536876A, wherein the weight fraction ratio of the bio-based copolyamide material C and the continuous long glass fiber was 40:60. Prepreg tape D (PA56TI): The preparation method is shown in Example 5 of the patent publication CN115536876A. Example 1 (1) Prepreg tape A is symmetrically laid at 0° / 90°, and then molded once to obtain a first protective layer and a second protective layer. The temperature of the molding once is 310° C., the pressure is 10 MPa, and the thickness of the first protective layer and the second protective layer is 1 mm. (2) immersing a steel plate having a thickness of 1.5 mm in a 70 wt % sulfuric acid solution at 30° C. for 5 min, and then transferring to a 40 wt % dimethylamine aqueous solution and immersing for 10 min to obtain a pretreated steel plate; (3) The first protective layer and the second protective layer are placed in an oven for preheating at a temperature of 320°C for 90 seconds. The pretreated steel plate is then placed between the preheated first protective layer and the second protective layer for secondary molding at a temperature of 150°C and a pressure of 15 MPa to obtain a finished battery pack bottom protective plate. Example 2 (1) Prepreg tape B is symmetrically laid at 0° / 90°, and then pressed once to obtain a first protective layer and a second protective layer. The temperature of the first pressing is 310° C., the pressure is 10 MPa, and the thickness of the first protective layer and the second protective layer is 1 mm. (2) immersing a steel plate having a thickness of 1.5 mm in a 70 wt % sulfuric acid solution at 30° C. for 5 min, and then transferring to a 40 wt % dimethylamine aqueous solution and immersing for 10 min to obtain a pretreated steel plate; (3) The first protective layer and the second protective layer are placed in an oven for preheating at a temperature of 320°C for 90 seconds. The pretreated steel plate is then placed between the preheated first protective layer and the second protective layer for secondary molding at a temperature of 150°C and a pressure of 15 MPa to obtain a finished battery pack bottom protective plate. Example 3 (1) The prepreg tape C is symmetrically laid at 0° / 90°, and then molded once to obtain a first protective layer and a second protective layer. The temperature of the molding once is 310° C., the pressure is 10 MPa, and the thickness of the first protective layer and the second protective layer is 1 mm; (2) immersing a steel plate having a thickness of 1.5 mm in a 70 wt % sulfuric acid solution at 30° C. for 5 min, and then transferring to a 40 wt % dimethylamine aqueous solution and immersing for 10 min to obtain a pretreated steel plate; (3) The first protective layer and the second protective layer are placed in an oven for preheating at a temperature of 320°C, and then the pretreated steel plate is placed between the preheated first protective layer and the second protective layer for secondary molding at a temperature of 150°C and a pressure of 15 MPa to obtain a finished battery pack bottom protective plate. Example 4 (1) The prepreg tape D is symmetrically laid at 0° / 90°, and then molded once to obtain a first protective layer and a second protective layer. The temperature of the molding once is 310° C., the pressure is 10 MPa, and the thickness of the first protective layer and the second protective layer is 1 mm. (2) immersing a steel plate having a thickness of 1.5 mm in a 70 wt % sulfuric acid solution at 30° C. for 5 min, and then transferring to a 40 wt % dimethylamine aqueous solution and immersing for 10 min to obtain a pretreated steel plate; (3) The first protective layer and the second protective layer are placed in an oven for preheating at a temperature of 320°C for 90 seconds. The pretreated steel plate is then placed between the preheated first protective layer and the second protective layer for secondary molding at a temperature of 150°C and a pressure of 15 MPa to obtain a finished battery pack bottom protective plate. Comparative Example 1 (1) Weigh the following components according to weight: 95 wt% of PP resin, 0.5 wt% of antioxidant 1098, 0.5 wt% of coupling agent KH570, 0.4 wt% of lubricant WAX-C, and 2 wt% of black masterbatch, add the above components into a high-speed mixer and mix to obtain a PP material; (2) Adding PP material into a twin-screw extruder and melt-extruded through the twin-screw extruder, wherein: the processing temperatures of the twin-screw extruder from zone 1 to zone 5 are 190° C., 210° C., 220° C., 220° C., and 230° C., respectively; the screw speed is 400 r / min; the main feed speed is 30 r / min; the length-to-diameter ratio of the twin-screw extruder is 36:1; and the die head temperature is 230° C.; (3) The extruded melt is evenly coated at the extrusion die to obtain a resin film that enters the impregnation die. The temperature of the impregnation die is set to 230°C. At the same time, the continuous glass fiber is preheated by the heating system and then pulled into the impregnation die at a pulling speed of 25m / min. The preheating temperature is 170°C and the preheating time is 8s. The PP material covers the continuous dispersed fibers on both sides. The continuous glass fiber content of the prepreg is controlled to be 60wt% by pulling. The prepreg is rolled into a prepreg at the composite unit by a composite roller. The thickness of the prepreg is 0.2mm. Finally, it is cooled, shaped, and cut. The circulating water temperature in the system water cooler is 23°C. (4) 0° / 90° symmetrical plying of the PP prepreg tapes was performed, and then a molding process was performed to obtain a first protective layer and a second protective layer. The molding process was performed at a temperature of 310° C. and a pressure of 10 MPa. The thickness of the first protective layer and the second protective layer was 1 mm. (5) immersing a steel plate having a thickness of 1.5 mm in a 70 wt % sulfuric acid solution at 30° C. for 5 min, and then transferring to a 40 wt % dimethylamine aqueous solution and immersing for 10 min to obtain a pretreated steel plate; (6) The first protective layer and the second protective layer are placed in an oven for preheating at a temperature of 210°C for 90 seconds. The pretreated steel plate is then placed between the preheated first protective layer and the second protective layer for molding at a temperature of 100°C and a pressure of 10 MPa to obtain a finished battery pack bottom protective plate. Comparative Example 2 The pretreatment of the steel plate in step (2) of Example 2 was not performed, and the rest was the same as Example 2. Comparative Example 3 The temperature and pressure of the secondary molding were 90° C. and 8 MPa, respectively, and the rest were the same as in Example 2. Comparative Example 4 (1) Prepreg tape B is symmetrically laid at 0° / 90°, and then pressed once to obtain a first protective layer and a second protective layer. The temperature of the first pressing is 310° C., the pressure is 10 MPa, and the thickness of the first protective layer and the second protective layer is 1 mm. (2) The surface of a steel plate with a thickness of 1.5 mm was cleaned by wiping with anhydrous ethanol to remove the oil stains and oxide film on the surface of the steel plate, and then Araldite 420 epoxy resin was coated on the steel plate on both sides, and the coating thickness was controlled to be no more than 50 μm. (3) The first protective layer and the second protective layer are placed in an oven for preheating at a temperature of 320° C., and then a steel plate coated with an adhesive Araldite 420 epoxy resin is placed between the preheated first protective layer and the second protective layer for secondary molding at a temperature of 150° C. and a pressure of 15 MPa to obtain a finished battery pack bottom protective plate. Comparative Example 5 The steel plate in step (2) is treated in a 70 wt % sulfuric acid solution at 30° C. for 5 minutes to obtain a pretreated steel plate. The rest is the same as in Example 2. Performance Testing The battery pack bottom guard plates provided in the above embodiments and comparative examples were subjected to the following performance tests: A sphere is used as an impact head to impact the battery pack bottom guard plate of the battery pack composite protection structure to simulate the working condition that the bottom of the vehicle is hit by a foreign object. The diameter of the sphere is 25 mm, the weight is 10 kg, the impact energy is 300 J, and the impact speed is 8.5 m / s. The center point of the battery protection bottom plate and four points around the center point are selected as impact points. Five impacts are performed. No penetration cracks should appear on the surface of the protective plate, and there should be no cracks as a whole, and the concave deformation is less than 4 mm. Use a vernier caliper to measure the diameter of the powdered area of ​​the battery protection bottom plate after impact. Repeat the measurement three times for a single impact point to determine the average value. Select the impact point with the largest diameter of the powdered area and record it as the diameter of the powdered area of ​​the battery protection bottom plate. Generally, the diameter of the powdered area is required to be no greater than 10mm. Use a vernier caliper to measure the diameter of the layered hollow part of the battery protection bottom plate after impact. Repeat the measurement three times for a single impact point to determine the average value. Select the impact point with the largest hollow diameter and record it as the hollow size of the battery protection bottom plate. Determine the hollow degree according to the following grading standards: R1: no stratification; R2: Slight delamination, hollow size diameter <4mm; R3: Slight delamination, hollow size diameter <8mm; R4: Layering, hollow size diameter > 8mm. The test results are shown in Table 1. Table 1 The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A battery pack bottom guard plate, characterized in that: The battery pack bottom protective plate includes a first protective layer, an impact-resistant layer and a second protective layer, the impact-resistant layer is between the first protective layer and the second protective layer, and the first protective layer and the second protective layer both include continuous fiber reinforced bio-based high-temperature polyamide composite materials.

2. The battery pack bottom guard plate according to claim 1, characterized in that: The impact-resistant layer is a metal plate, and the metal plate is preferably a steel plate.

3. The battery pack bottom guard plate according to claim 1, characterized in that: The thickness of the first protective layer and the second protective layer are independently 0.5-1 mm; Optionally, the metal plate has a thickness of 0.5-1.5 mm.

4. A method for preparing the battery pack bottom guard plate according to any one of claims 1 to 3, characterized in that: The method comprises: (1) cross-laying the prepreg tapes and then performing molding to obtain a first protective layer and a second protective layer respectively; (2) Preheating the first protective layer and the second protective layer, placing the metal plate between the preheated first protective layer and the second protective layer, and then performing secondary molding to obtain the battery pack bottom protective plate.

5. The method according to claim 4, characterized in that In step (1), the cross-plying method is 0 to 90 degrees; Optionally, in step (1), the temperature of the primary molding is 310-320° C. and the pressure is 10-13 MPa.

6. The method according to claim 4, characterized in that In step (2), before the metal plate is placed between the preheated first protective layer and the second protective layer, the metal plate is pretreated, the pretreatment comprising: immersing the metal plate in a 30-50 wt % sulfuric acid solution for 5-10 min, and then transferring the metal plate to a 35-45 wt % amine compound aqueous solution for immersion for 5-10 min, to obtain a pretreated metal plate; Optionally, the amine compound includes at least one of dimethylamine, diethylamine and dipropylamine.

7. The method according to claim 4, characterized in that The preheating temperature is 320-340° C. and the preheating time is 90-120 seconds.

8. The method according to claim 4, characterized in that In step (2), the secondary molding temperature is 100-150° C., preferably 130-150° C., the pressure is 12-17 MPa, preferably 13-15 MPa, and the time is 60-120 seconds.

Images