Battery pack, preparation method thereof and electric equipment

Abstract

The invention discloses a battery pack, a preparation method thereof and electric equipment. The battery pack comprises a plurality of battery cells, a battery cell accommodating space is defined by the box body, a plurality of battery cells are arranged in the battery cell accommodating space, at least partial area of the box body is provided with a polyurea coating, the polyurea coating comprises a polyurea material, and based on the total mass of the polyurea coating, the mass ratio of-HN-CO-NH-is 10%-14%. Therefore, the polyurea coating with excellent impact resistance and protection performance is obtained by increasing the content of-HN-CO-NH-in the polyurea coating.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to battery packs, methods for their fabrication, and electrical devices. Background Technology

[0002] Batteries are not only used in energy storage systems for hydropower, thermal power, wind power, and solar power plants, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. For vehicles, battery packs, because they are designed at the bottom of the vehicle, are susceptible to impacts during use. Therefore, protective coatings are typically applied to the battery pack casing to improve its impact resistance. However, existing protective coatings suffer from insufficient toughness and poor mechanical properties. Summary of the Invention

[0003] A first aspect of this application provides a battery pack comprising a plurality of battery cells; a housing defining a cell housing space within which the plurality of battery cells are disposed, wherein at least a portion thereof has a polyurea coating comprising a polyurea material, wherein the mass percentage of -HN-CO-NH- is 10%-14% based on the total mass of the polyurea coating. Thus, by increasing the content of -HN-CO-NH- in the polyurea coating, a polyurea coating exhibiting both excellent impact resistance and protective properties is obtained.

[0004] According to some embodiments of this application, the mass percentage of -HN-CO-NH- is 11.5%-13% based on the total mass of the polyurea coating. This improves the mechanical properties, weather resistance, abrasion resistance, and impact resistance of the polyurea coating.

[0005] According to some embodiments of this application, the thickness of the polyurea coating is 2mm-5mm. This improves the protective effect of the polyurea coating.

[0006] According to some embodiments of this application, the battery pack satisfies one or more of the following conditions: the tensile strength of the polyurea coating is 15MPa-25MPa; the elongation at break of the polyurea coating is 80%-200%; the tear strength of the polyurea coating is 85KN / m-177KN / m; the impact resistance of the polyurea coating is 1.3kg·m-3kg·m; and the Shore hardness of the polyurea coating is 50D-64D. Thus, the mechanical properties, toughness, wear resistance, and impact resistance of the polyurea coating are comprehensively improved, thereby enhancing the overall protective effect of the polyurea coating.

[0007] According to some embodiments of this application, the housing includes an upper housing and a lower housing, the upper housing and the lower housing defining a space for accommodating the battery cell, and the polyurea coating is disposed on at least a portion of the surface of the lower housing facing away from the battery cell. This improves the protective effect of the polyurea coating on the battery cell.

[0008] According to some embodiments of this application, the battery pack further includes a primer layer located on at least a portion of the surface of the housing, and the polyurea coating located on the surface of the primer layer away from the housing. This increases the adhesion between the polyurea coating and the housing, reducing the risk of the polyurea coating peeling off.

[0009] A second aspect of this application provides a method for manufacturing a battery pack, the method comprising forming a polyurea coating in at least a portion of a housing, the polyurea coating comprising a polyurea material, wherein the mass percentage of -HN-CO-NH- in the polyurea material is 10%-14% based on the total mass of the polyurea coating; and placing a plurality of battery cells within a cell-accommodating space formed by the housing to assemble a battery pack. This improves the tensile strength and impact resistance of the polyurea coating.

[0010] According to some embodiments of this application, the method includes mixing a diisocyanate monomer and a polyether polyol polymer to form a first mixture, heating to obtain an isocyanate prepolymer; mixing a polyether amine, an aromatic diamine, and an aromatic disecondary amine to form a second mixture; and spraying the isocyanate prepolymer and the second mixture onto at least a portion of the housing, causing the isocyanate prepolymer and the second mixture to polymerize to form the polyurea coating. Thus, the isocyanate prepolymer and the second mixture prepared by this method can rapidly polymerize after being sprayed by a spraying device, with a short surface drying time. After forming the polyurea coating, it can be oxidized at room temperature for 1-3 days to obtain a polyurea coating with good impact resistance, toughness, and wear resistance, which can improve the protective effect of the polyurea coating while saving energy.

[0011] According to some embodiments of this application, the method satisfies one or two of the following conditions: based on the total mass of the first mixture, the mass percentage of the diisocyanate monomer is 50%-73%, and the mass percentage of the polyether polyol polymer is 27%-50%; based on the total mass of the second mixture, the mass percentage of the polyether amine is 50%-70%, the mass percentage of the aromatic primary diamine is 20%-32%, and the mass percentage of the aromatic secondary diamine is 10%-20%. Therefore, by ensuring the amount of raw materials is within the above ranges, the impact resistance, toughness, and abrasion resistance of the polyurea coating can be improved, thereby enhancing the protective effect of the polyurea coating.

[0012] According to some embodiments of this application, the method satisfies one or more of the following conditions: the diisocyanate monomer includes one or more of diphenylmethane diisocyanate, toluene diisocyanate, and hexamethylene diisocyanate; the polyether polyol polymer includes one or more of polyethylene oxide polyol, polypropylene oxide polyol, polytetrahydrofuran polyol, ethylene oxide-propylene oxide copolymer polyol, and tetrahydrofuran-propylene oxide copolymer polyol; the polyether amine includes one or more of D400, T403, T5000, and D2000; the aromatic primary diamine includes one or two of diethyltoluenediamine and dimethylthiotoluenediamine; and the aromatic secondary diamine includes one or two of 4,4'-methylenebis[N-sec-butylaniline] and N,N'-dialkylphenyldiamine. Therefore, while improving the impact resistance, toughness, and abrasion resistance of the polyurea coating, the surface drying time and curing time of the polyurea material are shortened, and the cost of raw materials is reduced.

[0013] According to some embodiments of this application, one or two of the following conditions are met: the method further includes adding a viscosity modifier to the isocyanate prepolymer, wherein the viscosity modifier accounts for 1%-5% of the total mass of the isocyanate prepolymer; the second mixture further includes an additive, wherein the additive accounts for 1%-5% of the total mass of the second mixture. This increases the viscosity of the first mixture and improves the toughness of the polyurea coating. When the polyurea coating is applied in different scenarios, different types of additives can be added to the second mixture according to the application requirements to improve the applicability of the polyurea coating.

[0014] According to some embodiments of this application, the method satisfies one or more of the following conditions: at 25°C, the viscosity of the isocyanate prepolymer is 1000 cps-2000 cps; the isocyanate index of the isocyanate prepolymer is 1.05-1.20; based on the total mass of the isocyanate prepolymer, the mass percentage of isocyanate groups is 14%-21%; and at 25°C, the viscosity of the second mixture is 420 cps-635 cps. This improves the impact resistance, toughness, and abrasion resistance of the polyurea coating, thereby enhancing its protective effect.

[0015] According to some embodiments of this application, the volume ratio of the first mixture to the second mixture during spraying is 1:(1-1.5). This increases the content of -HN-CO-NH- in the formed polyurea material, thereby improving the impact resistance, toughness, and abrasion resistance of the polyurea coating, and enhancing its protective effect.

[0016] According to some embodiments of this application, the spraying pressure is 2000 psi-2500 psi. This improves the reaction efficiency between the isocyanate prepolymer and the second mixture.

[0017] According to some embodiments of this application, the method further includes the step of forming a primer layer in at least a portion of the enclosure. This improves the adhesion between the polyurea coating and the enclosure, reducing the risk of the polyurea coating peeling off.

[0018] The third aspect of this application provides an electrical device, including a battery pack provided in the first aspect of this application or a battery pack prepared by the method provided in the second aspect of this application.

[0019] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0020] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0021] Figure 1 A schematic flowchart illustrating the method for preparing a polyurea coating according to an embodiment of this application.

[0022] Figure 2 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0023] Figure 3 yes Figure 2 An exploded view of a battery pack according to one embodiment of this application is shown.

[0024] Figure 4 This is a schematic diagram of an electrical device using a battery pack as a power source according to one embodiment of this application.

[0025] Explanation of reference numerals in the attached figures:

[0026] 1. Battery pack; 2. Upper casing; 3. Lower casing; 4. Battery module. Detailed Implementation

[0027] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0028] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0029] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0030] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0031] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0032] Currently, judging from market trends, battery applications are becoming increasingly widespread. Batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. With the continuous expansion of battery applications, market demand is also constantly increasing.

[0033] Battery packs consist of cells and a casing. Related technologies involve applying a polyurea coating containing polyurea material to the surface of the metal casing to improve the impact resistance of the battery pack's bottom. Polyurea material, in its microstructure, comprises alternating hard and soft segments. Hard segments are high-crosslink density regions with a high content of -HN-CO-NH-, which are in a glassy state at room temperature, exhibiting high modulus, poor plasticity, and high strength. Soft segments are regions containing long-chain segments composed of oligomers such as polyethers, which are in a highly elastic state at room temperature, exhibiting good flexibility and random curling. The hard and soft segments create a complex multiphase system within the material, thus giving the polyurea coating excellent impact resistance. However, existing protective coatings cannot simultaneously achieve both impact resistance and protective performance.

[0034] This application proposes a battery pack that improves the impact resistance, toughness, and mechanical properties of a polyurea coating by increasing the content of -HN-CO-NH- in the polyurea coating and thus increasing the number of hard segments in the polyurea coating. After the content of -HN-CO-NH- is increased, the large number of binary hydrogen bonds between polyurea material molecules can increase the elasticity of the polyurea coating and increase the sliding stress between molecules, thereby reducing the impact strain of the polyurea coating and improving the protective performance of the material.

[0035] The battery pack proposed in this application can be used in electrical devices that use the battery pack as a power source or in various energy storage systems that use the battery pack as an energy storage element. Electrical devices can include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0036] The first aspect of this application provides a battery pack including a plurality of battery cells; a housing defining a cell housing space, wherein the plurality of battery cells are disposed within the cell housing space, and at least a portion thereof has a polyurea coating, the polyurea coating comprising a polyurea material, wherein the mass percentage of -HN-CO-NH- is 10%-14% based on the total mass of the polyurea coating.

[0037] The battery pack proposed in this application improves the impact resistance and protection of the housing by increasing the content of -HN-CO-NH- in the polyurea coating, thereby enhancing the protection of the battery cells.

[0038] In this application, the method for testing the -HN-CO-NH- content is to characterize the polyurea coating using nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy to determine the -HN-CO-NH- content in the polymer. For example, Fourier transform infrared spectroscopy can be used to quantitatively analyze the polyurea coating material, and the content can be determined at 3350 cm⁻¹ in the spectrum. -1 A shoulder peak was found at the point where -HN was found to be the stretching vibration peak of -HN in -HN-CO-NH-. The content of urea bonds in the material can be obtained by integrating the peak and comparing it with the control group with known content of -HN-CO-NH-.

[0039] As an example, based on the total mass of the polyurea coating, the mass percentage of -HN-CO-NH- can be 10%, 11%, 12%, 13%, or 14%, or a range of any of the above values. According to some specific embodiments of this application, based on the total mass of the polyurea coating, the mass percentage of -HN-CO-NH- can be 11.5%-13%.

[0040] According to some embodiments of this application, the density of the polyurea coating can be 1.05 g / cm³ at 25°C. 3 -1.6g / cm 3 For example, it could be 1.05 g / cm³. 3 1.1g / cm 3 1.2g / cm 3 1.3g / cm 3 1.4g / cm 3 1.5g / cm 3 Or 1.6g / cm 3 The values ​​can be any range of the above values. Therefore, the polyurea coating has a higher density, which improves its mechanical properties, weather resistance, abrasion resistance, and impact resistance.

[0041] In this application, the density test of the polyurea coating can be performed with reference to GB / T 6750-2007.

[0042] According to some embodiments of this application, the thickness of the polyurea coating can be 2mm-5mm. For example, it can be 2mm, 3mm, 4mm, or 5mm, or any range of the above values. Specifically, it can be selected according to the application scenario of the polyurea coating. Thus, selecting different thicknesses according to different scenarios can improve the protective performance of the polyurea coating.

[0043] In this application, the thickness of the polyurea coating can be tested with reference to GB1764-79.

[0044] According to some embodiments of this application, the tensile strength of the polyurea coating can be between 15 MPa and 26 MPa, for example, it can be 15 MPa, 17 MPa, 19 MPa, 21 MPa, 23 MPa, or 26 MPa, or a range of any of the above values. This gives the polyurea coating excellent protective properties.

[0045] In this application, the tensile strength test of the polyurea coating can be performed with reference to GB / T 528-2009.

[0046] According to some embodiments of this application, the elongation at break of the polyurea coating can be 80%-200%, for example, it can be 80%, 100%, 120%, 140%, 160%, 180% or 200%, or it can be a range of any of the above values.

[0047] In this application, the elongation at break test can be performed with reference to GB / T 528-2009. This ensures that the polyurea coating has suitable hardness.

[0048] According to some embodiments of this application, the tear strength of the polyurea coating can be between 85 kN / m and 177 kN / m, for example, it can be 85 kN / m, 90 kN / m, 100 kN / m, 110 kN / m, 120 kN / m, 130 kN / m, 140 kN / m, 150 kN / m, 160 kN / m, or 177 kN / m, or any range of the above values. This improves the tear resistance of the polyurea coating.

[0049] In this application, the test method for the tear strength of the polyurea coating can be carried out with reference to GB / T 529-2008.

[0050] According to some embodiments of this application, the Shore hardness of the polyurea coating can be 50D-64D, for example, it can be 50D, 52D, 54D, 56D, 58D, 60D, 62D or 64D, or it can be any range of the above values.

[0051] In this application, the Shore hardness test method for the polyurea coating can be found in GB / T 531.1-2008. This ensures the polyurea coating possesses suitable hardness.

[0052] According to some embodiments of this application, the impact resistance of the polyurea coating can be between 1.3 kg·m and 3 kg·m, for example, it can be 1.3 kg·m, 1.8 kg·m, 2.3 kg·m, 2.7 kg·m, or 3 kg·m, or any range of the above values. This gives the polyurea coating excellent impact resistance.

[0053] In this application, the test method for the impact resistance of the polyurea coating can be found in GB / T 20624.2-2006.

[0054] Thus, by keeping the tensile strength, elongation at break, tear strength, Shore hardness, and impact resistance within the above ranges, a polyurea coating that simultaneously possesses excellent impact resistance, protective properties, tear resistance, and moderate hardness can be obtained.

[0055] According to some embodiments of this application, the housing includes an upper housing and a lower housing, which define a space for accommodating the battery cells. The polyurea coating is disposed on at least a portion of the lower housing surface facing away from the battery cells. Specifically, when the battery pack is used as a power source for an electric vehicle, the battery pack is disposed at the bottom of the vehicle. A polyurea coating is disposed on at least a portion of the lower housing surface facing away from the battery cells (i.e., at least a portion of the lower housing surface near the ground). The polyurea coating has excellent impact resistance, toughness, and abrasion resistance. When the lower housing is impacted, the polyurea coating can improve the protection of the internal battery cells by the lower housing, thereby improving the safety of the battery pack.

[0056] It should be noted that the polyurea coating is disposed on at least a portion of the surface of the lower housing that is away from the battery cell. The polyurea coating may be in direct contact with the lower housing, or there may be other functional coatings between the polyurea coating and the lower housing.

[0057] According to some embodiments of this application, in order to improve the adhesion between the polyurea coating and the housing, the battery pack may further include a primer layer, the primer layer being located on at least a portion of the surface of the housing, and the polyurea coating being located on the surface of the primer layer away from the housing. That is, the primer layer is located between the lower housing and the polyurea coating to improve the adhesion between the polyurea coating and the housing, reducing the risk of the polyurea coating peeling off when subjected to impact or friction.

[0058] A second aspect of this application provides a method for manufacturing a battery pack, the method comprising forming a polyurea coating in at least a portion of a housing, the polyurea coating comprising a polyurea material, wherein the mass percentage of -HN-CO-NH- in the polyurea material is 10%-14% based on the total mass of the polyurea coating; and placing a plurality of battery cells within a cell-accommodating space formed by the housing to assemble a battery pack. This yields a polyurea coating possessing excellent impact resistance, protective properties, and mechanical properties.

[0059] The following section provides a detailed explanation of each step of this method. (Refer to the following for further details.) Figure 1 The method includes:

[0060] S10: Mix the diisocyanate monomer and the polyether polyol polymer to form a first mixture, and heat to obtain the isocyanate prepolymer.

[0061] According to some embodiments of this application, the diisocyanate monomer is added to a dry reaction vessel under nitrogen protection, stirred and heated at a uniform speed, and then a polyether polyol polymer is added to the reaction vessel. The reaction is carried out at 60°C-70°C to obtain the isocyanate prepolymer.

[0062] According to some embodiments of this application, the diisocyanate monomer is added to a dry reaction vessel under nitrogen protection, stirred at a uniform rate and heated to 75°C, and then a polyether polyol polymer is added to the reaction vessel. The reaction is carried out at 60°C-70°C for 3 hours to obtain the isocyanate prepolymer. Specifically, the polyether polyol polymer can be added to the reaction vessel in portions every 10 minutes.

[0063] According to some embodiments of this application, based on the total mass of the first mixture, the mass percentage of the diisocyanate monomer can be 50%-73%, and the mass percentage of the polyether polyol polymer can be 27%-50%. Therefore, by adjusting the amounts of diisocyanate monomer and polyether polyol polymer, the content of -HN-CO-NH- in the polyurea coating can be controlled, thereby obtaining a polyurea coating with excellent impact resistance, mechanical properties, and protective properties. By reacting the diisocyanate monomer and the polyether polyol polymer to obtain an isocyanate prepolymer, the prepolymer has a larger molecular weight when reacting with the second mixture (i.e., an amine chain extender), which can prevent the reaction from being too rapid, improve the uniformity of the polyurea coating, and enhance its protective performance. The polyurea material prepared by reacting the isocyanate prepolymer with an amine chain extender also has a larger molecular weight, which can improve the mechanical properties of the polyurea coating.

[0064] According to some embodiments of this application, based on the total mass of the first mixture, the mass percentage of the diisocyanate monomer can be 60%, 61%, 62%, 63%, 64%, or 65%, or can be any range of the above values.

[0065] According to some embodiments of this application, the mass percentage of the polyether polyol polymer can be 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, or 38%, or can be any of the above values.

[0066] According to some embodiments of this application, the diisocyanate monomer includes one or more of diphenylmethane diisocyanate, toluene diisocyanate, and hexamethylene diisocyanate. Therefore, the isocyanate prepolymer prepared from the above-mentioned types of diisocyanate monomers exhibits rapid surface drying at room temperature during the reaction with amine chain extenders. Furthermore, the sprayed polyurea coating can be cured at room temperature for 1-3 days to allow for further complete reaction, achieving the optimal performance of the polyurea coating. Further reaction in an oven is unnecessary, saving energy. Simultaneously, the raw material cost is low, reducing production costs.

[0067] According to some embodiments of this application, the diisocyanate monomer includes diphenylmethane diisocyanate.

[0068] According to some embodiments of this application, the polyether polyol polymer includes one or more of polyethylene oxide polyol, polypropylene oxide polyol, polytetrahydrofuran polyol, ethylene oxide-propylene oxide copolyol, and tetrahydrofuran-propylene oxide copolyol.

[0069] According to some embodiments of this application, the polyether polyol polymer includes a polyether polyol polymer of methyl ethylene oxide and ethylene oxide.

[0070] According to some embodiments of this application, based on the total mass of the first mixture, the mass percentage of the diphenylmethane diisocyanate can be 50%-73%, and the mass percentage of the methyl ethylene oxide and ethylene oxide polyether polyol polymer can be 27%-50%. Thus, by reacting the diphenylmethane diisocyanate and the methyl ethylene oxide and ethylene oxide polyether polyol polymer to obtain an isocyanate prepolymer, the isocyanate prepolymer has a larger molecular weight when reacting with amine chain extenders, which can prevent the reaction from being too rapid, improve the uniformity of the polyurea material, and enhance the protective performance of the polyurea material. This is achieved through the use of isocyanates with a larger molecular weight.

[0071] According to some embodiments of this application, the first mixture may further include a viscosity modifier. Specifically, the diisocyanate monomer is added to a dry reaction vessel under nitrogen protection, stirred at a uniform rate and heated to 75°C. Then, a polyether polyol polymer is added to the reaction vessel in portions at 10-minute intervals. The reaction is carried out at 60°C-70°C for 3 hours to obtain the isocyanate prepolymer. After cooling and discharge, a viscosity modifier is added to adjust the viscosity of the isocyanate prepolymer, thereby improving the toughness of the formed polyurea coating. The polyurea material prepared by reacting the ester prepolymer with an amine chain extender also has a larger molecular weight, which can improve the mechanical properties of the polyurea material.

[0072] According to some embodiments of this application, the first mixture further includes a viscosity modifier, the mass percentage of which may be 1%-5% based on the total mass of the first mixture. This increases the viscosity of the isocyanate prepolymer and improves the mechanical properties of the formed polyurea coating.

[0073] As an example, the mass percentage of the viscosity modifier can be 1%, 2%, 3%, 4%, or 5%, or a range of any of the above values.

[0074] According to some embodiments of this application, at 25°C, the viscosity of the isocyanate prepolymer can be between 1000 cps and 2000 cps, for example, it can be 1000 cps, 1200 cps, 1400 cps, 1600 cps, 1800 cps, or 2000 cps, or any range of the above values. This improves the toughness of the formed polyurea coating.

[0075] In this application, the viscosity of the isocyanate prepolymer can be tested with reference to GB / T 1723-1993.

[0076] According to some embodiments of this application, the isocyanate index of the isocyanate prepolymer can be 1.05-1.2, for example, it can be 1.05, 1.07, 1.09, 1.1, 1.12, 1.14, 1.16, 1.18, or 1.2, or a range of any of the above values. Therefore, an appropriate excess of isocyanate groups can compensate for losses during material storage and construction, allowing the isocyanate prepolymer to react fully with the second mixture; simultaneously, it reduces the risk of isocyanate groups reacting with water in the air to generate gas, thereby causing foaming or pores on the polyurea coating surface.

[0077] In this application, the isocyanate index of the isocyanate prepolymer is the ratio of the amount of isocyanate groups in the isocyanate prepolymer to the amount of amine groups in the second mixture during batching, or the molar ratio of -NCO groups to -NH2 groups (or -NH groups).

[0078] According to some embodiments of this application, the mass percentage of isocyanate groups in the isocyanate prepolymer is 14%-21%, for example, it can be 14%, 16%, 17%, 18%, 19%, or 21%, or any range of the above values. Therefore, adjusting the viscosity of the isocyanate prepolymer facilitates smooth spraying and results in a cured product with good physical properties and moderate reactivity.

[0079] In this application, the test method for the isocyanate group content of the isocyanate prepolymer can be referred to HG / T 2409-92.

[0080] S20: Mix polyetheramine, aromatic diamine, and aromatic disecondary amine to form a second mixture.

[0081] According to some embodiments of this application, polyetheramine, aromatic diamine, and aromatic disecondary amine are added to a paint tank and stirred at high speed for 30 minutes using a high-shear dispersion device to obtain a second mixture. Thus, a polyurea coating is prepared by reacting the above three amine chain extenders with the isocyanate prepolymer. After the isocyanate prepolymer and the second mixture are sprayed through a spray gun, they can be fully mixed and atomized at the nozzle to form a polyurea coating on at least a portion of the surface of the housing. The surface drying time at room temperature is approximately 30 seconds, and the sprayed polyurea coating can be cured at room temperature for 1-3 days to allow the material to react further completely, achieving the optimal performance of the polyurea coating.

[0082] When using the above three amine chain extenders, the polyetheramine has a smaller molecular weight, which increases the reaction rate when reacting with the isocyanate prepolymer. This shortens the surface drying time after spraying, allowing the formed polyurea coating to be cured directly at room temperature without the need for an oven reaction, saving energy and preventing spray gun clogging, thus improving construction efficiency. Aromatic diamines are light in color and have good color retention. When reacting with the isocyanate prepolymer, they react quickly, improving the tensile strength, impact strength, and heat resistance of the formed polyurea coating. Aromatic disecondary amines are sterically hindered secondary amine chain extenders. When reacting with the isocyanate prepolymer, they reduce the reaction rate and appropriately prolong the reaction time, thereby improving the surface condition of the polyurea coating and enhancing its impact resistance and low-temperature performance.

[0083] According to some embodiments of this application, based on the total mass of the second mixture, the mass percentage of the polyether amine can be 50%-70%, the mass percentage of the aromatic diprimary amine can be 20%-32%, and the mass percentage of the aromatic disecondary amine can be 10%-20%. Thus, by keeping the contents of the three amine chain extenders within the above ranges, the tensile strength, impact resistance, thermal properties, and low-temperature properties of the polyurea coating are improved, while the surface drying time of the polyurea coating is shortened.

[0084] As an example, the mass percentage of the polyetheramine can be 50%, 55%, 60%, 65%, or 70%, or a range of any of the above values.

[0085] As an example, the mass percentage of the aromatic diamine can be 20%, 22%, 24%, 26%, 28%, 30%, or 32%, or a range of any of the above values.

[0086] As an example, the aromatic diamine may contain 10%, 12%, 14%, 16%, 18%, or 20% by mass, or any range of these values. This shortens the surface drying time of the polyurea coating.

[0087] According to some embodiments of this application, the polyetheramine includes one or more of D400, T403, T5000, and D2000.

[0088] According to some embodiments of this application, the aromatic diamine includes one or both of diethyltoluenediamine and dimethylthiotoluenediamine.

[0089] According to some embodiments of this application, the aromatic di-secondary amine includes one or both of 4,4'-methylenebis[N-sec-butylaniline] and N,N'-dialkylphenylenediamine.

[0090] According to some embodiments of this application, the second mixture may further include an additive, the mass percentage of which is 1%-5% based on the total mass of the second mixture. For example, it may be 1%, 2%, 3%, 4%, or 5%, or a range of any of the above values.

[0091] As an example, the additives may include one or more of the following: colorants, dispersants, flame retardants, rheology modifiers, antisettling agents, fillers, mildew inhibitors, antistatic agents, antioxidants, light stabilizers, coupling agents, catalysts, and leveling defoamers. Specifically, different types of additives can be added according to the application scenarios of the battery pack to improve the applicability of the polyurea coating.

[0092] According to some embodiments of this application, at 25°C, the viscosity of the second mixture is 420 cps-635 cps. For example, it can be 420 cps, 460 cps, 500 cps, 540 cps, 580 cps, 620 cps, or 635 cps, or any range of the above values. This improves the toughness of the formed polyurea coating.

[0093] It should be noted that steps S10 and S20 can be performed simultaneously.

[0094] S30: The isocyanate prepolymer and the second mixture are sprayed onto at least a portion of the housing, causing the isocyanate prepolymer and the second mixture to polymerize and form the polyurea coating.

[0095] According to some embodiments of this application, the isocyanate prepolymer and the second mixture are sprayed onto the surface of the housing using a spraying device. Therefore, the process of forming a polyurea coating using the aforementioned isocyanate prepolymer and the second mixture does not involve volatile organic solvents, thus reducing environmental impact.

[0096] According to some embodiments of this application, the volume ratio of the isocyanate prepolymer to the second mixture during spraying is 1:(1-1.5). For example, it can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, or 1:1.5, or any range of the above values. This improves the tensile strength, impact resistance, thermal properties, and low-temperature performance of the polyurea coating.

[0097] According to some embodiments of this application, the method further includes the step of forming a primer layer in at least a portion of the enclosure. Specifically, the metal enclosure may be soaked before spraying to remove oil stains from the metal surface and improve the adhesion between the polyurea coating and the metal enclosure. After soaking and drying for 15-30 minutes, an epoxy primer is sprayed, with a spray thickness of 45μm-55μm.

[0098] According to some embodiments of this application, before spraying with a spraying device, the isocyanate prepolymer and the second mixture can be heated to 65°C-80°C respectively to improve fluidity.

[0099] According to some embodiments of this application, the spraying pressure is 2000psi-2500psi, for example, it can be 2000psi, 2100psi, 2200psi, 2300psi, 2400psi, or 2500psi, or any range of the above values. Thus, under high pressure, the isocyanate prepolymer and the second mixture can be thoroughly mixed after spraying to form a uniform polyurea coating on the metal casing.

[0100] Figure 2 and Figure 3 This is an example of battery pack 1, along with an exploded view of battery pack 1. (Refer to...) Figure 2 The battery pack 1 may include a housing and multiple battery modules 4 disposed within the housing. The battery housing includes an upper housing 2 and a lower housing 3, with the upper housing 2 covering the lower housing 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the housing.

[0101] According to some embodiments of this application, the type of battery cell in the battery pack is not limited and can be one or more of lithium-ion batteries, sodium-ion batteries, negative electrode-free sodium metal batteries, and sodium metal batteries.

[0102] Furthermore, a third aspect of this application provides an electrical device, which includes the battery pack provided in this application. The battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0103] Figure 4 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0104] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application clearer, the following will provide a more detailed description in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0105] Example 1

[0106] 1. Preparation of isocyanate prepolymer

[0107] Diphenylmethane diisocyanate was added to a dry reactor under nitrogen protection, and the mixture was stirred at a constant speed and heated to 75°C. Ethylene oxide-propylene oxide copolyol was then added to the reactor in batches at 10-minute intervals. Based on the total mass of diphenylmethane diisocyanate and ethylene oxide-propylene oxide copolyol, the mass percentage of diphenylmethane diisocyanate was 54.2%, and the mass percentage of ethylene oxide-propylene oxide copolyol was 45.8%. The mixture was reacted at 70°C for 3 hours to obtain the isocyanate prepolymer. After cooling and discharge, an appropriate amount of propylene carbonate was added to the prepolymer. Based on the total mass of the isocyanate prepolymer, the mass percentage of propylene carbonate was 2%. The mixture was stirred evenly to adjust the viscosity of the isocyanate prepolymer to 2000 cps.

[0108] 2. Preparation of the second mixture

[0109] Add D2000, diethyltoluenediamine, and 4,4'-methylenebis[N-sec-butylaniline] to a paint tank. The mass percentage of D2000 is 60%, the mass percentage of diethyltoluenediamine is 25%, and the mass percentage of 4,4'-methylenebis[N-sec-butylaniline] is 15%. Stir at high speed for 30 minutes using a high-shear dispersant at a speed of 800 rpm.

[0110] 3. Spraying

[0111] The coating was applied using a Graco XP2 / XP3 / E-10hp main unit and a Fusion flat spray gun. Before coating, the metal was immersed in a 10% aluminum deacidification solution for 15 minutes to remove oil stains from the metal surface. After drying, a primer was applied with a thickness of 50μm and dried for 12 hours.

[0112] The isocyanate prepolymer and the second mixture are heated to 75°C with a volume ratio of 1:1. The spraying equipment pressure is 2200 psi. The sprayed polyurea coating is then placed in a room temperature environment for curing to obtain a metal with a polyurea coating on the surface.

[0113] The preparation methods of the polyurea coatings in Examples 2-10, Comparative Examples 1 and 2 are the same as those in Example 1, with the differences detailed in Table 1.

[0114]

[0115]

[0116] Performance testing methods

[0117] 1. Viscosity

[0118] Refer to GB / T 1723-1993.

[0119] 2. Surface drying time

[0120] Refer to GB / T 1728-1979.

[0121] 3. Tensile strength

[0122] Refer to GB / T 528-2009.

[0123] 4. Elongation at break

[0124] Refer to GB / T 528-2009.

[0125] 5. Tear strength

[0126] Refer to GB / T 529-2008.

[0127] 6. Shore hardness

[0128] Refer to GB / T 531.1-2008.

[0129] 7. Adhesion

[0130] Refer to GB / T 5210-20068.

[0131] 8. Impact resistance

[0132] Refer to GB / T 20624.2-2006.

[0133] 9. Abrasion resistance index

[0134] Refer to GB / T 9867-2008.

[0135] 10. Method for determining the content of -HN-CO-NH-

[0136] In this application, the method for testing the -HN-CO-NH- content is to characterize the polyurea coating using nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy to determine the -HN-CO-NH- content in the polymer. For example, Fourier transform infrared spectroscopy can be used to quantitatively analyze the polyurea coating material, and the content can be determined at 3350 cm⁻¹ in the spectrum. -1 A shoulder peak was found at the point where -HN was found to be the stretching vibration peak of -HN in -HN-CO-NH-. The content of urea bonds in the material can be obtained by integrating the peak and comparing it with the control group with known content of -HN-CO-NH-.

[0137] The performance test results of the polyurea coatings in Examples 1-10, Comparative Example 1, and Comparative Example 2 are shown in Table 2.

[0138]

[0139] As can be seen from the comparison between Examples 1-10 and Comparative Examples 1 and 2, the polyurea coating on the battery pack proposed in this application can achieve a surface drying time of less than 40 seconds at room temperature after spraying by controlling the amount of reactants. Furthermore, the sprayed polyurea coating can be fully reacted after curing at room temperature for 1-3 days, resulting in a polyurea coating with high impact resistance, tensile strength, elongation at break, tear strength, Shore hardness, and abrasion resistance index. This demonstrates that by controlling the content of -HN-CO-NH- in the polyurea coating, this application can obtain a polyurea coating with excellent impact resistance, protective properties, tear resistance, and moderate hardness.

[0140] As can be seen from Examples 1-4 and Comparative Example 1, if the mass proportion of -HN-CO-NH- in the polyurea coating is too small, although the polyurea coating has a high elongation at break, its impact resistance, tensile strength, tear strength, and abrasion index are low, resulting in insufficient strength of the polyurea coating and reduced impact resistance. As can be seen from Examples 1-4 and Comparative Example 2, if the mass proportion of -HN-CO-NH- in the polyurea coating is too large, the elongation at break of the polyurea coating is low, and the polyurea coating has high hardness and brittleness, which reduces the impact resistance of the polyurea coating.

[0141] As can be seen from Examples 1-5, different types of diisocyanate monomers, polyether polyol polymers, polyether amines, aromatic primary diamines, and aromatic secondary diamines can all form polyurea coatings with both excellent impact resistance and protective properties.

[0142] As can be seen from Examples 7-10, by controlling the mass ratio of polyetheramine, aromatic diamine and aromatic diamine in the second mixture, a polyurea coating with high impact resistance, tensile strength, elongation at break, tear strength, Shore hardness and abrasion index can be obtained, thereby obtaining a polyurea coating with excellent impact resistance, protective performance and tear resistance as well as moderate softness and hardness.

[0143] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery pack, characterized in that, include: Multiple battery cells; A housing that defines a cell housing space, in which a plurality of cells are disposed, and at least a portion thereof has a polyurea coating comprising a polyurea material, wherein the mass percentage of -HN-CO-NH- is 10%-14% based on the total mass of the polyurea coating.

2. The battery pack according to claim 1, characterized in that, Based on the total mass of the polyurea coating, the mass percentage of -HN-CO-NH- is 11.5%-13%.

3. The battery pack according to claim 1 or 2, characterized in that, The thickness of the polyurea coating is 2mm-5mm.

4. The battery pack according to any one of claims 1-3, characterized in that, One or more of the following conditions must be met: The tensile strength of the polyurea coating is 15MPa-26MPa; The elongation at break of the polyurea coating is 80%-200%; The tear strength of the polyurea coating is 85KN / m-177KN / m; The impact resistance of the polyurea coating is 1.3 kg·m-3 kg·m; The polyurea coating has a Shore hardness of 50D-64D.

5. The battery pack according to any one of claims 1-4, characterized in that, The housing includes an upper housing and a lower housing, which define a space for accommodating the battery cell. The polyurea coating is disposed on at least a portion of the surface of the lower housing facing away from the battery cell.

6. The battery pack according to any one of claims 1-5, characterized in that, It also includes a primer layer located on at least a portion of the surface of the housing, and the polyurea coating located on the surface of the primer layer away from the housing.

7. A method for preparing a battery pack, characterized in that, include: A polyurea coating is formed in at least a portion of the housing, the polyurea coating comprising a polyurea material, wherein the mass percentage of -HN-CO-NH- in the polyurea material is 10%-14% based on the total mass of the polyurea coating; Multiple battery cells are placed within the cell housing space formed by the housing to assemble a battery pack.

8. The method according to claim 7, characterized in that, include: Diisocyanate monomers and polyether polyol polymers are mixed to form a first mixture, which is then heated to obtain an isocyanate prepolymer. The polyetheramine, the aromatic diamine, and the aromatic disecondary amine are mixed to form a second mixture; The isocyanate prepolymer and the second mixture are sprayed onto at least a portion of the housing, causing the isocyanate prepolymer and the second mixture to polymerize and form the polyurea coating.

9. The method according to claim 8, characterized in that, One or two of the following conditions must be met: Based on the total mass of the first mixture, the mass percentage of the diisocyanate monomer is 50%-73%, and the mass percentage of the polyether polyol polymer is 27%-50%. Based on the total mass of the second mixture, the polyetheramine accounts for 50%-70% of the mass, the aromatic diamine accounts for 20%-32% of the mass, and the aromatic disecondary amine accounts for 10%-20% of the mass.

10. The method according to claim 8 or 9, characterized in that, One or more of the following conditions must be met: The diisocyanate monomer includes one or more of diphenylmethane diisocyanate, toluene diisocyanate, and hexamethylene diisocyanate; The polyether polyol polymer includes one or more of polyethylene oxide polyol, polypropylene oxide polyol, polytetrahydrofuran polyol, ethylene oxide-propylene oxide copolyol, and tetrahydrofuran-propylene oxide copolyol; The polyetheramine includes one or more of D400, T403, T5000, and D2000; The aromatic diamine includes one or both of diethyltoluenediamine and dimethylthiotoluenediamine; The aromatic diamine includes one or both of 4,4'-methylenebis[N-sec-butylaniline] and N,N'-dialkylphenylenediamine.

11. The method according to any one of claims 8-10, characterized in that, One or two of the following conditions must be met: The method further includes adding a viscosity modifier to the isocyanate prepolymer, wherein the viscosity modifier accounts for 1%-5% of the total mass of the isocyanate prepolymer. The second mixture also includes additives, which account for 1%-5% of the total mass of the second mixture.

12. The method according to any one of claims 8-11, characterized in that, One or more of the following conditions must be met: At 25°C, the viscosity of the isocyanate prepolymer is 1000cps-2000cps; The isocyanate index of the isocyanate prepolymer is 1.05-1.20; Based on the total mass of the isocyanate prepolymer, the mass percentage of isocyanate groups is 14%-21%; At 25°C, the viscosity of the second mixture is 420 cps-635 cps.

13. The method according to any one of claims 8-12, characterized in that, During spraying, the volume ratio of the isocyanate prepolymer to the second mixture is 1:(1-1.5).

14. The method according to any one of claims 8-13, characterized in that, The spraying pressure is 2000psi-2500psi.

15. The method according to any one of claims 7-14, characterized in that, Also includes: The step of forming a primer layer in at least a portion of the housing.

16. An electrical appliance, characterized in that, The battery pack includes the battery pack according to any one of claims 1-6 or the battery pack prepared by the method according to any one of claims 7-15.

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