An explosion-proof flame-retardant foamed battery pack and a preparation method thereof

Abstract

The application provides an explosion-proof and fire-retardant foamed battery pack and a preparation method, comprising: a one-time formed foamed box body without joints, wherein the surface of the foamed box body is covered with a metal protective layer, and the inner wall of the metal protective layer is coated with a polyurea coating layer. The foamed base body in the application has a small density, a good weight reduction effect compared with metal materials, and can achieve the purpose of light weight. The foamed box body combined with the polyurea coating layer can provide double fire-retardant protection. The foamed box body has excellent energy absorption characteristics in cooperation with the polyurea coating layer, can withstand explosion overpressure, and can effectively prevent fragments from splashing.

Description

Technical Field

[0001] This invention belongs to the field of new energy battery technology, and in particular relates to an explosion-proof and flame-retardant foamed battery pack and its preparation method. Background Technology

[0002] With the rapid development of new energy vehicles, aerospace and energy storage, the performance requirements for battery pack casings are increasing.

[0003] Current battery case casings are generally made of metal, which has a high density and significantly increases overall weight, reducing driving range. While conventional plastic casings are lighter, they lack impact resistance and are prone to cracking under external impact or battery thermal runaway, failing to effectively prevent fragmentation. Regarding flame retardancy, some engineering plastics (such as PC / ABS) require the addition of halogen or phosphorus-based flame retardants to achieve a V-0 rating, posing environmental and leaching issues. In terms of processing, existing foam casings are mostly made by first preparing sheet materials and then bonding them together, resulting in seams that affect overall strength and sealing. Summary of the Invention

[0004] The present invention provides an explosion-proof and flame-retardant foamed battery pack, comprising: a seamless foamed housing body formed in one piece, wherein the surface of the foamed housing body body is covered with a metal protective layer, and the inner wall of the metal protective layer is coated with a polyurea coating. The main body of the foamed box comprises, by weight: 40-80 parts of polyphenylene ether, 10-40 parts of polyphenylene sulfide, 2-10 parts of compatibilizer, 1-8 parts of organic peroxide, and 0.1-1 parts of inorganic nanonucleating agent.

[0005] Furthermore, it also includes at least one non-foamed area for mounting a heat dissipation structure.

[0006] Furthermore, it also includes a pressure relief component, which is used to release pressure when the air pressure inside the foaming box body reaches a preset value.

[0007] The present invention also provides a method for preparing the aforementioned explosion-proof and flame-retardant foamed battery pack, comprising: According to the mass ratio, 40-80 parts of polyphenylene ether, 10-40 parts of polyphenylene sulfide, 2-10 parts of compatibilizer, 1-8 parts of organic peroxide, and 0.1-1 parts of inorganic nanonucleating agent are mixed, melt-blended and granulated by a twin-screw extruder to obtain modified granules. The modified particles are placed in a box mold, the mold is sealed, the temperature is raised to 2160-250℃, supercritical fluid is injected to maintain a saturation pressure of 10-35MPa, the saturation time is 30-60min, the pressure is released to atmospheric pressure at a rate of 15-20 MPa / s, and then the temperature is cooled and shaped at a cooling rate of at least 30℃ / min. The mold is then demolded to obtain a seamless foamed box that is formed in one step. The inner wall of the foamed metal protective layer is surface treated by spraying polyurea coating and curing to obtain the foamed box body. A metal protective layer is applied to the surface of the foaming box body. A polyurea coating is applied to the inner wall of the metal protective layer.

[0008] Specifically, the polyphenylene ether is in the form of 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, and 80 parts; the polyphenylene sulfide is in the form of 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, and 40 parts; the compatibilizer is in the form of 2 parts, 4 parts, 5 parts, 6 parts, and 8 parts; the organic peroxide is in the form of 1 part, 3 parts, 5 parts, 6 parts, and 8 parts; and the inorganic nanonucleating agent is in the form of 0.1 parts, 0.3 parts, 0.5 parts, 0.8 parts, and 1 part.

[0009] Preferably, the composition includes 50-65 parts of polyphenylene ether, 15-25 parts of polyphenylene sulfide, 3-6 parts of compatibilizer, 2-5 parts of organic peroxide, and 0.2-0.5 parts of inorganic nanonucleating agent. Alternatively, the polyphenylene ether can be 50, 53, 55, 60, 63, or 65 parts; the polyphenylene sulfide can be 15, 18, 20, 22, or 25 parts; the compatibilizer can be 3, 4, 5, or 6 parts; the organic peroxide can be 2, 3, 4, or 5 parts; and the inorganic nanonucleating agent can be 0.2, 0.3, 0.4, or 0.5 parts.

[0010] It should be noted that blending polyphenylene oxide (PPO) with polyphenylene sulfide (PPS) during foaming can leverage the heat resistance of PPO and the corrosion resistance of PPS, resulting in a foamed material with excellent heat resistance and corrosion resistance. Adding a solubilizer can improve the interfacial compatibility between PPO and PPS. Specifically, solubilizers can be epoxy resins, maleic anhydride grafts, polystyrene, styrene copolymers, etc., preferably styrene-glycidyl methacrylate copolymer (SG).

[0011] Organic peroxides, used as modifiers, combined with inorganic nanonucleating agents, can cause branching or cross-linking of PPS molecular chains, significantly improving melt strength. Specifically, the organic peroxides can be selected from dicumyl peroxide, bis-tert-butyl peroxide, or 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, with di-tert-butyl peroxide being preferred. The inorganic nanonucleating agents can be selected from nano-montmorillonite, talc, preferably nano-silica or nano-titanium dioxide, with a particle size of 10-50 nm, more preferably 20-40 nm.

[0012] To improve the thermal conductivity of the explosion-proof and flame-retardant foamed battery pack, it also includes 5-15 parts by weight of thermally conductive filler, specifically 5 parts, 8 parts, 10 parts, 12 parts, or 15 parts, preferably 8-10 parts, specifically 8 parts, 9 parts, or 10 parts. The thermally conductive filler can be boron nitride or aluminum oxide.

[0013] Specifically, the housing mold can be configured according to specific application scenarios. For example, when used in new energy batteries, the mold can be designed to resemble a battery pack. Furthermore, the mold has at least one localized heat-conducting area, creating at least one non-foamed area on the surface of the seamless foamed housing. This localized heat-conducting area forms cooling channels on the surface of the mold cavity, preventing foaming at corresponding locations during the foaming process and thus creating a high-density non-foamed area. This area has high heat dissipation performance and can be used to install heat dissipation structures, such as those in battery modules or electronic devices that are prone to heat generation. In some embodiments, metal parts can also be provided on the mold, allowing the metal parts to be pre-embedded in the foamed housing during the foaming process for battery installation or module fixation.

[0014] In the specific implementation process, the modified particles are placed in a mold, the mold is sealed, and the temperature is raised to 160-250℃, specifically 160℃, 180℃, 200℃, 230℃, and 250℃. After heating, supercritical fluid is injected to maintain a saturation pressure of 10-35MPa. After saturation for 30-60 minutes, the pressure is released to atmospheric pressure at a rate of 15-20 MPa / s, and then cooled to 50-70℃ at a cooling rate of at least 30℃ / min for shaping. The mold is then demolded to obtain a seamless foamed box body formed in one piece. Specifically, the saturation pressure is 10MPa, 15MPa, 20MPa, 25MPa, 30MPa, and 35MPa; the saturation time is 30 minutes, 40 minutes, 50 minutes, and 60 minutes; and the depressurization rate is 15MPa / s, 16MPa / s, 18MPa / s, and 20 MPa / s. Preferably, the saturation pressure is 20-25 MPa, the saturation time is 40-50 min, and the pressure relief rate is 16-18 MPa / s. Specifically, the saturation pressures are 20 MPa, 22 MPa, 24 MPa, and 25 MPa; the saturation times are 40 min, 43 min, 46 min, and 50 min; and the pressure relief rates are 16 MPa / s, 17 MPa / s, and 18 MPa / s. The foamed box obtained from these process parameters has a density of 0.3-0.8 g / cm³. 3 With a wall thickness of 3-8 mm, it is a seamless, one-piece molded structure that is thick yet lightweight, enabling lightweight product design.

[0015] It should be noted that the supercritical fluid is a mixture of carbon dioxide gas and nitrogen gas, with a mass ratio of carbon dioxide gas to nitrogen gas of (1:5)-(6:1), specifically: (1:5), (1:2), (1:1), (2:1), (3:1), (4:1), (5:1), (6:1). Preferably, the mass ratio of carbon dioxide gas to nitrogen gas is (1:2)-(3:1), specifically: (1:2), (1:1), (1.5:1), (2:1), (2.5:1), (3:1). By adjusting the mixing ratio, the foam density and pore size distribution are controlled, thereby making the strength and density of the foamed box uniform and improving the overall explosion-proof performance.

[0016] Specifically, when pretreating the inner wall of the metal protective layer, the inner wall can be subjected to anodic corona treatment, plasma treatment, or coating with an interface agent to improve the roughness of the inner wall. Then, a polyurea coating is applied to the inner wall surface to improve the adhesion of the polyurea coating.

[0017] Furthermore, it also includes: spraying a flame-retardant polyurea coating onto the inner wall of the metal protective layer with a coating thickness of 1.5-3 mm, a spraying temperature of 65-75°C, and a spraying pressure of 2000-3000 psi. Specifically, the coating thickness is 1.5 mm, 2 mm, 2.5 mm, and 3 mm; the spraying temperature is 65°C, 70°C, and 75°C; and the spraying pressure is 2000 psi, 2500 psi, and 3000 psi.

[0018] Polyurea possesses extremely high strength and excellent elasticity. Therefore, applying it as a coating to the inner wall of the metal protective layer of a foamed enclosure can give the enclosure excellent explosion-proof and impact-resistant properties. To prevent fragments from flying when the enclosure breaks and to achieve explosion-proof performance, the thickness of the polyurea is typically 1.5-3 mm, preferably 2-3 mm, specifically 2 mm, 2.5 mm, and 3 mm. In practical implementation, high-temperature and high-pressure spraying equipment can be used to spray flame-retardant polyurea coating onto the inner wall of the metal protective layer. The preferred spraying temperature is 68-72℃, and the pressure is 2500-2800 psi. Specifically, the spraying temperatures are 68℃, 70℃, and 72℃, and the spraying pressures are 2500 psi, 2600 psi, and 2800 psi, respectively.

[0019] Specifically, the polyurea coating is obtained by reacting isocyanate polymers and amino compounds. It should be noted that during spraying, the polyurea coating is formed by rapidly reacting the isocyanate polymer and amino compound using high-temperature, high-pressure spraying equipment to create a polyurea elastomer. The isocyanate polymer, an MDI prepolymer, provides the framework for the polyurea coating to improve its hardness and strength, while the amino compound provides the polyurea coating with elasticity, toughness, and reactivity.

[0020] Specifically, the amino compound includes terminal amino polyethers, amine chain extenders, and functional additives, with the following weight proportions: 50-70 parts amino polyether, 10-25 parts amine chain extenders, and 5-15 parts functional additives. The terminal amino polyether is Jeffamine D2000 or T5000, which is the core raw material for polyurea, providing the elastic backbone. Its molecular weight affects the ratio of hard and soft segments. Preferably, the molecular weight of the terminal amino polyether is 10,000-50,000, primarily providing elasticity and impact resistance to the coating. The amine chain extender is DETDA (diethyltoluene diamine), E100, or E300, which reacts with isocyanates to form urea bonds, regulating the hard segment content and mechanical properties. Its main function is to improve the hardness and strength of the coating and control the reaction rate. The functional additive is a phosphorus-based or nitrogen-based flame retardant, achieving a flame-retardant effect.

[0021] The foamed matrix in this invention has a low density, resulting in better weight reduction compared to metal materials and achieving lightweighting. Both PPO and PPS in the foamed housing material are intrinsically flame-retardant, and PPS also possesses excellent corrosion resistance. Combined with a polyurea coating, it provides double flame-retardant protection. The foamed housing also exhibits excellent energy absorption characteristics, which, combined with the polyurea coating, allow it to withstand explosive overpressure and effectively prevent fragmentation. Furthermore, this invention uses intermittent molding foaming in a single process, resulting in a seamless housing with high overall strength and excellent sealing. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the structure of the explosion-proof and flame-retardant foamed battery pack provided in the embodiments of this application.

[0024] The markings used in the attached diagram are: 1-foamed box body; 2-polyurea coating; 3-metal protective layer; 4-pressure relief assembly. Detailed Implementation

[0025] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0026] The present invention provides an explosion-proof and flame-retardant foamed battery pack, comprising: a seamless foamed housing body 1 formed in one piece, wherein the surface of the foamed housing body 1 is covered with a metal protective layer 3, and the inner wall of the metal protective layer 3 is coated with a polyurea coating 2.

[0027] Among them, the metal protective layer 3 is an aluminum alloy film, a magnesium alloy film or other materials, and the metal protective layer 3 provides structural strength support for the explosion-proof and flame-retardant foamed battery pack.

[0028] Furthermore, it also includes at least one non-foamed area for mounting a heat dissipation structure.

[0029] Furthermore, it also includes a pressure relief component 4, used to release pressure when the air pressure inside the foaming chamber body 1 reaches a preset value. The pressure relief component 4 can be a mechanical automatic pressure relief valve, which opens when the air pressure inside the foaming chamber body 1 reaches the preset value. Alternatively, the pressure relief component 4 can be an electrically controlled pressure relief valve, where a pressure sensor detects the air pressure inside the foaming chamber body 1 and controls the valve to open or close.

[0030] For example, the pressure relief assembly 4 is a mechanical pressure relief valve, including a valve body for rotatably assembling with a mounting hole on the battery housing. The outer circumferential surface of the valve body is radially protruded with an anti-disengagement step for engaging with an anti-disengagement stop provided on the wall of the mounting hole to prevent the pressure relief valve from disengaging from the mounting hole. The anti-disengagement step has a top anti-disengagement surface for engaging with the anti-disengagement stop when the valve body rotates with the anti-disengagement step to the anti-disengagement position. The outer circumferential surface of the valve body is also provided with two stop structures distributed circumferentially along the valve body for engaging with a limiting structure provided in the mounting hole to limit the valve body in both directions of rotation when the anti-disengagement step rotates to the anti-disengagement position. The two stop structures are front and rear stop structures spaced back and forth in the direction of rotation of the anti-disengagement step toward the anti-disengagement position. The front stop structure is an elastic block that deforms under pressure when the anti-disengagement step rotates toward the anti-disengagement position and elastically resets when the anti-disengagement step rotates to the anti-disengagement position.

[0031] Specifically, the main body 1 of the foamed box comprises, by weight: 40-80 parts of polyphenylene ether, 10-40 parts of polyphenylene sulfide, 2-10 parts of compatibilizer, 1-8 parts of organic peroxide, and 0.1-1 parts of inorganic nano-nucleating agent.

[0032] The present invention also provides a method for preparing an explosion-proof and flame-retardant foamed battery pack, the specific embodiments of which are as follows.

[0033] Example 1 The following mixtures were prepared by mass: 60 parts of polyphenylene oxide (PPO), 20 parts of polyphenylene sulfide (PPS), 5 parts of compatibilizer (SG), 3 parts of organic peroxide (di-tert-butyl peroxide), and 0.3 parts of inorganic nano-nucleating agent (nano-SiO2). The mixtures were then melt-blended and granulated using a twin-screw extruder. The modified particles were placed into the battery box mold (mold wall thickness 5mm), the mold was sealed, the temperature was raised to 200℃, supercritical fluid (CO2 and N2 mixed in 1:1) was injected to 25MPa, the saturation time was 45min, the pressure was released to atmospheric pressure at a rate of 18MPa / s, and then the temperature was lowered to 60℃ at a cooling rate of 30℃ / min to set the shape and demold. Plasma treatment was performed on the inner wall of the foam box body using a spraying equipment, followed by spraying a 2mm layer of polyurea coating (spraying temperature 70℃, pressure 2500 psi), and curing to obtain the foam box body 1. A metal protective layer 3 is applied to the surface of the foamed box body 1. A polyurea coating 2 is applied to the inner wall of the metal protective layer 3.

[0034] Table 1 shows the components of Comparative Examples 1-2 and Examples 2-17. The preparation steps are described in Example 1.

[0035] Table 1. Mass composition of Comparative Examples 1-2 and Examples 2-17

[0036] Density testing, flame retardancy rating testing, impact strength testing, thermal conductivity testing, explosion pressure testing, and electrolyte resistance testing were conducted on the foamed boxes prepared in Comparative Examples 1-2 and Examples 1-17 above.

[0037] Density test: Cut a 10mm×10mm×10mm sample from the foaming box, weigh it as m1 using an analytical balance with an accuracy of 0.1mg, wet the sample with a surfactant to remove air bubbles, and then completely immerse it in distilled water. Weigh its mass in the liquid as m2, and calculate the density ρ=m1 / (m1-m2)×ρdistilled water.

[0038] Flame retardancy rating test: vertical burning method, national standard GB / T 2408.

[0039] Impact strength test: drop hammer impact test, national standard GB / T 14153.

[0040] Thermal conductivity test: heat flow meter method, standard ASTM E1530.

[0041] Explosion-proof pressure test: explosion pressure test of explosion-proof enclosure, national standard GB 3836.2.

[0042] Corrosion resistance test: Electrolyte for vented nickel-cadmium batteries, national standard GB / T 18270-2012, test the mass change rate of the sample and the surface condition when viewed visually.

[0043] Table 2. Test results of Comparative Examples 1-2 and Examples 2-17

[0044] The test results of Example 1 show that the composite component of PPO and PPS has a high impact strength of 85 J, a thermal conductivity of 0.12 W / m·K, and a high explosion pressure resistance of 1.28 MPa, which is significantly improved compared to the single-component comparative examples 1 and 2. Its corrosion resistance is also greatly improved. Example 1 is significantly superior to comparative examples 1 and 2.

[0045] As can be seen from Examples 1 and 2, the thermal conductivity of Example 2 was significantly improved after adding thermally conductive filler while maintaining other properties basically the same.

[0046] As shown in Examples 1 and 3-5, keeping other components constant and changing the composition of PPS, such as when the PPS composition in Examples 1 and 3 is 20 and 25 respectively, the explosion resistance pressure is 1.28 MPa and 1.5 MPa, and the corrosion resistance is significantly better than that in Examples 4 and 5. Example 4 has a high density and does not achieve the desired lightweight effect.

[0047] As can be seen from Examples 1, 6-9, keeping other components unchanged and changing the PPO composition, such as when the PPO composition in Examples 1, 6 and 7 is 50, 60 and 65, the explosion resistance pressure is 1.28MPa, 1.28MPa and 1.3MPa, which is better than that in Examples 8 and 9. The flame retardant rating is better than that in Example 8. The corrosion resistance is significantly better than that in Examples 8 and 9. The density of Example 9 is too high and does not achieve the effect of lightweighting.

[0048] As can be seen from Examples 1 and 10-13, keeping other components unchanged, but changing the di-tert-butyl peroxide component, such as the di-tert-butyl peroxide components of 3, 2, and 5 in Examples 1, 11, and 12, and 1 and 8 in Examples 10 and 13, the impact strength of Examples 10 and 13 is too high at 150J and 140J, and the explosion pressure is 0.9MPa and 0.8MPa, respectively. Obviously, the overall performance of Examples 1, 11, and 12 is better than that of Examples 10 and 13.

[0049] As shown in Examples 1, 14-17, keeping other components unchanged but altering the SG solubilizer composition (e.g., SG solubilizer components 5, 3, and 6 in Examples 1, 15, and 16, and 2 and 10 in Examples 14 and 17), the flame retardant ratings of Examples 1, 15, and 16 are superior to those of Examples 14 and 17. Example 17 exhibits a high impact strength of 130 J and a low explosion pressure of 0.9 MPa. The corrosion resistance of Examples 1, 15, and 16 is superior to that of Examples 14 and 17. Clearly, the overall performance of Examples 1, 15, and 16 is superior to that of Examples 14 and 17.

[0050] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

[0051] The above description is only a partial embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An explosion-proof and flame-retardant foamed battery pack, characterized in that, include: A seamless foamed box body formed in one piece, wherein the surface of the foamed box body is covered with a metal protective layer, and the inner wall of the metal protective layer is coated with a polyurea coating. The main body of the foamed box comprises, by weight: 40-80 parts of polyphenylene ether 10-40 parts of polyphenylene sulfide Compatibilizer 2-10 parts, 1-8 parts of organic peroxides 0.1-1 parts of inorganic nanonucleating agent.

2. The explosion-proof and flame-retardant foamed battery pack according to claim 1, characterized in that, It also includes at least one non-foamed area for mounting heat dissipation structures.

3. The explosion-proof and flame-retardant foamed battery pack according to claim 1, characterized in that, It also includes a pressure relief component, which is used to release pressure when the air pressure inside the foaming box body reaches a preset value.

4. A method for preparing an explosion-proof and flame-retardant foamed battery pack as described in any one of claims 1-3, characterized in that, include: According to the mass ratio, 40-80 parts of polyphenylene ether, 10-40 parts of polyphenylene sulfide, 2-10 parts of compatibilizer, 1-8 parts of organic peroxide, and 0.1-1 parts of inorganic nanonucleating agent are mixed, melt-blended and granulated by a twin-screw extruder to obtain modified granules. The modified particles are placed in a box mold, the mold is sealed, the temperature is raised to 160-250℃, supercritical fluid is injected to maintain a saturation pressure of 10-35MPa, the saturation time is 30-60min, the pressure is released to atmospheric pressure at a rate of 15-20 MPa / s, the temperature is cooled and shaped at a cooling rate of at least 30℃ / min, and the mold is demolded to obtain a seamless foamed box that is formed in one step. The inner wall of the foamed metal protective layer is surface treated by spraying polyurea coating and curing to obtain the foamed box body. A metal protective layer is applied to the surface of the foaming box body. A polyurea coating is applied to the inner wall of the metal protective layer.

5. The preparation method according to claim 4, characterized in that, The product also includes, by weight: 5-15 parts of thermally conductive filler.

6. The preparation method according to claim 4, characterized in that, Also includes: The coating thickness of flame-retardant polyurea coating is 1.5-3 mm when sprayed on the inner wall of the metal protective layer, the spraying temperature is 65-75℃, and the spraying pressure is 2000-3000 psi.

7. The preparation method according to claim 4, characterized in that, The supercritical fluid is a mixture of carbon dioxide gas and nitrogen gas, with a mass ratio of carbon dioxide gas to nitrogen gas of (1:5) to (6:1).

8. The preparation method according to claim 4, characterized in that, The mold is provided with at least one local heat-conducting area so that the surface of the seamless foamed box is formed with at least one non-foamed area.

9. The preparation method according to claim 4, characterized in that, Polyurea coatings are obtained by reacting isocyanate polymers with amino compounds.

10. The preparation method according to claim 4, characterized in that, A polyurea coating is applied to the inner wall of the metal protective layer, comprising: Anodizing corona treatment is performed on the inner wall of the metal protective layer to roughen the inner wall surface; The polyurea coating is applied to the inner wall surface after corona treatment.

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