Battery pack case and method of manufacturing the same

Abstract

The present application relates to a kind of battery pack box and preparation method thereof, mainly solve the problem of poor fire performance of battery pack box in the prior art, poor heat preservation effect leads to the endurance mileage reduction of battery under extremely cold weather.The present application is by using a kind of battery pack box, including upper cover plate and battery tray, the top surface outer side of upper cover plate is equipped with top surface heat preservation layer, the outer side of battery tray is equipped with at least bottom heat preservation layer;Top surface heat preservation layer and bottom heat preservation layer are polyurethane foam, component A, B with weight ratio 1:1~1.1 is formed, component A includes melamine resin 4~6 parts, high polyether polyol 8~12 parts, hard bubble crosslinking agent 4~6 parts, flame-retardant polyester polyol 40~45 parts, flame retardant 20~25 parts, foam stabilizer 0.5~1.5 parts, catalyst 4~6 parts, water 0.1~0.5 parts, physical foaming agent 10~13 parts, antioxidant 0.5~1 parts by weight fraction, and its preparation method technical scheme, preferably solve the problem, can be used in the industrial production of battery pack box.

Description

Technical Field

[0001] This invention relates to the field of new energy vehicles, and in particular to a battery pack housing and its manufacturing method. Background Technology

[0002] Lithium-ion batteries use lithium metal or lithium alloy as the negative electrode material and a non-aqueous electrolyte solution. They are widely used in various products and equipment that require battery power and are one of the most practical power sources. In the operating environment of lithium-ion batteries, temperature has the greatest impact on their charge and discharge performance; a suitable temperature environment is crucial for maintaining this performance. To enable lithium-ion batteries to operate in low-temperature environments, the traditional solution is to modify the internal materials, using special materials to manufacture batteries known as "low-temperature batteries." However, the manufacturing process for "low-temperature batteries" is difficult and expensive, their low-temperature threshold is limited, and they cannot withstand the impact of high temperatures in environments with large temperature differences.

[0003] In the promotion and application of new energy electric vehicles, the battery range is poor when the ambient temperature is low, especially in winter, when the range is reduced by nearly half compared to the range specified by the car manufacturer. This is a problem that bothers electric vehicle owners and is also the reason why electric vehicles have not been widely promoted and accepted in northern my country. In addition, the ideal operating temperature of a battery is 15-40℃. At low temperatures, the electrolyte in the battery becomes more viscous, the activity of lithium ions decreases, the resistance to chemical reactions increases, the charging and discharging speed slows down, and the capacity decreases. In cold winter conditions, the temperature requirements for the charging process are even more stringent. Lithium batteries are prone to lithium plating when charged below 0℃, causing irreversible damage and safety problems, and may even induce short circuits and spontaneous combustion, posing safety hazards.

[0004] Rigid polyurethane foam is one of the most ideal insulation materials and is currently widely used in refrigerators, freezers, containers, buildings, LNG ships, and other fields requiring insulation. Covering a battery pack with a layer of polyurethane insulation will greatly reduce heat transfer between the battery cells and the external environment, thus ensuring that the battery cells can still maintain a relatively ideal operating temperature when the external temperature is low. However, conventional polyurethane foam has drawbacks such as flammability, low fire resistance, and poor insulation performance.

[0005] Chinese patent CN 108559385A discloses a thermal insulation shell for new energy power batteries and its preparation method. The thermal insulation shell includes a base shell and a thermal insulation layer disposed on the inner end face of the base shell. The thermal insulation layer is formed by reacting and curing a component A (10-90%) with a component B (10-90%). The component A includes the following raw materials in the following mass percentages: 30-97.6 parts of polyol, 1-30 parts of crosslinking agent, 0.1-8 parts of foaming agent, 0.1-10 parts of foam stabilizer, 0.1-3 parts of catalyst, and 0-50 parts of functional additives. The component B includes diisocyanate, polyisocyanate, prepolymer of diisocyanate, and / or prepolymer of polyisocyanate. However, since the thermal insulation layer is disposed on the inner end face of the base shell, the space is limited, which poses a safety hazard if the battery experiences thermal runaway. Furthermore, the physical properties of the thermal insulation layer are not disclosed, which cannot meet the fire resistance and thermal insulation performance requirements of new energy electric vehicle battery packs.

[0006] Chinese patent CN 109585734 A discloses a new energy power battery box and a spraying process. By spraying, an insulation layer is set on the inner and outer sides of the shell. It is not affected by the external structural shape of the shell, has good insulation effect, and is integrally formed. Since the insulation layer on the base shell is formed by the spraying process, it is easy to control the thickness and uniformity of the insulation layer. However, it lacks detailed data support and cannot ensure that the sprayed polyurethane foam layer can meet the fireproof and heat insulation performance requirements of electric vehicle materials. Moreover, its performance decays rapidly with temperature, which is not conducive to maintaining battery performance. Summary of the Invention

[0007] One of the technical problems to be solved by the present invention is that the poor fire resistance and poor heat insulation of the battery pack housing in the prior art lead to a reduction in battery range under extremely cold weather conditions. The present invention provides a battery pack housing that has the advantages of good fire resistance, good heat insulation, and less reduction in battery range under extremely cold weather conditions.

[0008] The second technical problem to be solved by the present invention is to provide a method for preparing a battery pack housing corresponding to the first technical problem.

[0009] To solve one of the above-mentioned technical problems, the present invention adopts the following technical solution: a battery pack housing, comprising a top cover plate 1 and a battery tray 2, wherein the top surface of the top cover plate 1 is provided with a top surface insulation layer 4-1, and the outer surface of the battery tray 2 is provided with at least a bottom surface insulation layer 4-2; the top surface insulation layer 4-1 and the bottom surface insulation layer 4-2 are both polyurethane foam, composed of components A and B, wherein the weight ratio of component A to component B is 1:1 to 1.1; component A, by weight parts, comprises: 4 to 6 parts of melamine resin, 8 to 12 parts of high-functionality polyether polyol, 4 to 6 parts of rigid foam crosslinking agent, 40 to 45 parts of flame-retardant polyester polyol, 20 to 25 parts of flame retardant, and 0.5 to 1.5 parts of foam stabilizer. The composition includes 4-6 parts catalyst, 0.1-0.5 parts water, 10-13 parts physical foaming agent, and 0.5-1 parts antioxidant; wherein, the melamine resin has a hydroxyl value of 350-500 mgKOH / g and a functionality of 2-4; the high-functionality polyether polyol is a polyether polyol with sorbitol or sucrose as the main initiator and a hydroxyl value of 380-550 mgKOH / g; the rigid foam crosslinking agent is a polyether polyol with ethylenediamine and toluenediamine as the main initiators and a hydroxyl value of 435-800 mgKOH / g and a viscosity >4000 mPa·s; the flame-retardant polyester polyol has a functionality of 2-3 and a hydroxyl value of 210-280 mgKOH / g; and component B is polymethylene polyphenyl polyisocyanate.

[0010] Further, the melamine resin is selected from at least one of CN-3360 or CN-4500; the high-functionality polyether polyol is selected from at least one of NJ-8238, NJ-6305C or NJ-4110A; the rigid foam crosslinking agent is selected from at least one of NJ-403 or TD405; and the flame-retardant polyester polyol is selected from at least one of PS7001, Terol250 or HF8730.

[0011] Furthermore, the flame retardant is a phosphate ester flame retardant; the foam stabilizer is selected from one of non-hydrolyzable silicone surfactants or polysiloxane surfactants; and the catalyst is selected from at least three of amine catalysts or metal catalysts.

[0012] Furthermore, the flame retardant is selected from at least one of TEP, TCPP, TCEP, TDCPP, FR530, or DMMP; the foam stabilizer is selected from at least one of L6900, L6100, DC193, B8462, LK443, or LK221; and the catalyst is selected from at least three of PC5, PC8, PC41, TMR-2, A33, K15, PC46, KAC, or BDMAEE.

[0013] Furthermore, the physical foaming agent is selected from at least one of HFC 245fa, HFC 365 / 227, HFO 1233zd or HFO1336mzz; the antioxidant is selected from at least one of Irganox 1076, Anox PP18 or Irganox 1135.

[0014] Furthermore, a polyurethane foam layer is also sprayed or bonded to the outer side of the battery tray 2 to form a side insulation layer 4-3.

[0015] Furthermore, the density of the top insulation layer 4-1, the bottom insulation layer 4-2, and the side insulation layer 4-3 is 40–130 kg / m³. 3 Compressive strength >300kPa, fire rating V0, thermal conductivity <0.03W / m·k@25℃.

[0016] Furthermore, the density of the top insulation layer 4-1, the bottom insulation layer 4-2, and the side insulation layer 4-3 is 40–60 kg / m³. 3 .

[0017] Furthermore, a top adhesive layer 3-1 is provided between the top cover plate 1 and the top insulation layer 4-1, a bottom adhesive layer 3-2 is provided between the bottom surface of the battery tray 2 and the bottom insulation layer 4-2, and a side adhesive layer 3-3 is provided between the side surface of the battery tray and the side insulation layer 4-3, and the amount of adhesive layer is 50-100 g / m². 2 .

[0018] Furthermore, the adhesives used in the top adhesive layer 3-1, bottom adhesive layer 3-2, and side adhesive layer 3-3 have a viscosity of 2000–3800 mPa·s at 25°C, an NCO% of 13–18%, and a specific gravity of 1.12–1.20%.

[0019] Furthermore, the outer layer of the bottom insulation layer 4-2 is provided with a protective layer 5.

[0020] Furthermore, the protective layer 5 is selected from at least one of polyurea or steel plate.

[0021] Furthermore, the thickness of the top insulation layer 4-1, the bottom insulation layer 4-2, and the side insulation layer 4-3 is 2 to 30 mm.

[0022] To solve the second technical problem mentioned above, the present invention adopts the following technical solution: A method for preparing a battery pack housing, comprising the following steps:

[0023] (a) Prepare the top cover 1 and battery tray 2;

[0024] (b) Spray or attach polyurethane foam to the outer top surface of the top cover plate 1 to form a top surface insulation layer 4-1.

[0025] (c) At least the outer side of the bottom surface of the battery tray 2 is sprayed or laminated with polyurethane foam to form a bottom insulation layer 4-2, thus obtaining the battery pack box;

[0026] The polyurethane foam is composed of components A and B, with a weight ratio of component A to component B of 1:1 to 1.1. Component A, by weight, includes: 4 to 6 parts melamine resin, 8 to 12 parts high-functionality polyether polyol, 4 to 6 parts rigid foam crosslinking agent, 40 to 45 parts flame-retardant polyester polyol, 20 to 25 parts flame retardant, 0.5 to 1.5 parts foam stabilizer, 4 to 6 parts catalyst, 0.1 to 0.5 parts water, 10 to 13 parts physical foaming agent, and 0.5 to 1 part antioxidant; wherein the hydroxyl value of the melamine resin is 350– 500 mg KOH / g, functionality 2-4; high-functionality polyether polyol is a polyether polyol with sorbitol or sucrose as the main initiator, hydroxyl value 380-550 mg KOH / g; rigid foam crosslinking agent is a polyether polyol with ethylenediamine and toluenediamine as the main initiators, hydroxyl value 435-800 mg KOH / g, viscosity >4000 mPa·s; flame-retardant polyester polyol has functionality 2-3, hydroxyl value 210-280 mg KOH / g; component B is polymethylene polyphenyl polyisocyanate.

[0027] Furthermore, before spraying or bonding polyurethane foam, adhesive is sprayed to form a top adhesive layer 3-1, a bottom adhesive layer 3-2, and a side adhesive layer 3-3.

[0028] Furthermore, the viscosity of the adhesive is 2000–3800 mPa·s at 25°C, the NCO% is 13–18%, and the specific gravity is 1.12–1.20%.

[0029] Furthermore, during spraying, component A and component B are uniformly mixed in a weight ratio of 1:1 to 1.1 using a high-pressure sprayer, atomized and foamed, and the foam is rapidly formed and cured to form a polyurethane foam layer. The operating conditions of the high-pressure sprayer are as follows: the distance between the spray gun nozzle and the substrate is 300 to 450 mm, the moving speed is uniform, the ambient temperature during spraying is 10 to 25°C, the relative humidity is less than 85%, and the wind speed during construction does not exceed 5 m / s.

[0030] The battery pack housing provided by this invention forms an insulation layer by spraying or laminating a rigid polyurethane foam with excellent performance onto the outer side of the bottom surface, the outer side of the sides, and the outer side of the top surface of the upper cover plate. The density of the polyurethane foam insulation layer is 40-130 kg / m³. 3With a compressive strength >300MPa, a fire rating of V0, and a thermal conductivity <0.03W / m·k@25℃, the battery pack exhibits a long temperature drop time in thermal insulation simulation experiments. This combination results in the battery pack housing possessing excellent fire resistance, thermal insulation, high compressive strength, and minimal temperature-dependent battery performance. Furthermore, the thickness of the sprayed insulation layer is controllable, ensuring good insulation and effectively reducing heat transfer between the battery pack and the external environment. Additionally, spraying polyurea or installing a steel plate on the outside of the polyurethane foam at the bottom of the tray further enhances the battery pack housing's resistance to stone impacts. Applying adhesive before spraying the polyurethane foam further strengthens the bond between the polyurethane foam and the battery tray or top cover, preventing detachment even at low temperatures, achieving excellent technical results.

[0031] The performance data for the polyurethane foam and battery pack housing in this manual are based on the following testing standards:

[0032] Density: GB / T 6343-2009

[0033] Compressive strength: GB / T 8813-2020

[0034] Thermal conductivity: GB / T 10294-2008

[0035] Fire rating: UL-94

[0036] Temperature drop time: An aluminum box simulation experiment was conducted. The specific process was as follows: Two aluminum boxes were fabricated to simulate battery trays. One box had no insulation layer, while the other was coated with insulation according to the technical solution of this invention. A reference battery cell was placed inside the aluminum box, and temperature sensors were installed at the middle, second outermost, and outermost positions inside the aluminum box. First, both aluminum boxes were placed in a constant temperature environment at 25°C, and then simultaneously placed in a constant temperature environment at -20°C. The time required for the temperature at each point inside the aluminum box to drop from 25°C to 0°C was recorded as the temperature drop time. Attached Figure Description

[0037] Appendix Figure 1 This is a schematic diagram of the cross-sectional structure of the battery pack housing in this invention.

[0038] Appendix Figure 1 In the diagram, 1 is the top cover, 2 is the battery tray, 3-1 is the top adhesive layer, 3-2 is the bottom adhesive layer, 3-3 is the side adhesive layer, 4-1 is the top insulation layer, 4-2 is the bottom insulation layer, 4-3 is the side insulation layer, and 5 is the protective layer. Detailed Implementation

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0040] Table 1 Raw Material List

[0041]

[0042]

[0043]

Example 1

[0044] A method for preparing a battery pack housing includes the following steps:

[0045] (a) Prepare the top cover 1 and battery tray 2;

[0046] (b) Spray polyurethane foam onto the outer top surface of the top cover plate 1 to form a top surface insulation layer 4-1 with a thickness of 7 mm.

[0047] (c) Spray polyurethane foam on the outer bottom and outer sides of the battery tray 2 to form a bottom insulation layer 4-2 and a side insulation layer 4-3 with a thickness of 7mm, respectively, to obtain the battery pack box.

[0048] The polyurethane foam is composed of component A and component B. The components are: melamine resin CN-3360 (4 parts), high-functionality polyether polyol NJ-6305C (8.96 parts), rigid foam crosslinking agent NJ-403 (3.99 parts), flame-retardant polyester polyol PS7001 (42.95 parts), flame retardant TEP (22.93 parts), foam stabilizer DC193 (0.73 parts), catalysts PC-5 (1.6 parts), A33 (1.0 part), K15 (0.7 parts), PC-41 (1.0 part), antioxidant Irganox 1076 (0.5 parts), water (0.3 parts), and physical blowing agent HFC 245fa (11.97 parts). Component B is polymethylene polyphenyl polyisocyanate M20S (105.1 parts).

[0049] During spraying, component A and component B are uniformly mixed in a weight ratio using a high-pressure sprayer, atomized and foamed, and the foam is rapidly formed and cured to create a polyurethane foam layer. Sampling and testing revealed the following performance indicators for the polyurethane foam: density 45 kg / m³. 3 The compressive strength is 303 kPa, the fire rating is V0, and the thermal conductivity at 25℃ is 0.023 W / m·k. The operating conditions of the high-pressure sprayer are: the distance between the spray gun nozzle and the base surface is 400 mm, the moving speed is uniform, the ambient temperature for spraying is 23℃, the relative humidity is less than 85%, and the wind speed during construction does not exceed 5 m / s.

[0050]

Example 2

[0051] A method for preparing a battery pack housing includes the following steps:

[0052] (a) Prepare the top cover 1 and battery tray 2;

[0053] (b) Apply Suprasec 2060 adhesive to the outer top surface of the upper cover plate 1, forming a coating of 50–100 g / m². 2 Top surface adhesive layer 3-1; 50-100 g / m² of adhesive is sprayed onto the outer bottom and outer sides of the battery tray 2. 2 The adhesive is used to form a bottom adhesive layer 3-2 and a side adhesive layer 3-3, respectively.

[0054] (c) Spray a 22mm thick polyurethane foam onto the outer side of the top adhesive layer 3-1 and the bottom adhesive layer 3-2 to form a top insulation layer 4-1 and a bottom insulation layer 4-2. Then, attach a 22mm thick polyurethane foam onto the outer side of the side adhesive layer 3-3 to form a side insulation layer 4-3.

[0055] (d) Spray a 3mm thick polyurea onto the outside of the bottom insulation layer 4-2 to form a protective layer 5, thus obtaining the battery pack housing;

[0056] The performance data for polyurethane foam are as follows: density 62 kg / m³ 3 The compressive strength is 416 kPa, the fire rating is V0, and the thermal conductivity at 25℃ is 0.024 W / m·k. The specific polyurethane foam formulation is shown in Table 2. The operating conditions of the high-pressure sprayer during spray foaming are the same as in Example 1.

[0057]

Example 3

[0058] A method for preparing a battery pack housing includes the following steps:

[0059] (a) Prepare the top cover 1 and battery tray 2;

[0060] (b) Spray polyurethane foam on the outer top surface of the top cover plate 1 to form a top surface insulation layer 4-1 with a thickness of 7mm. Spray polyurethane foam on the outer bottom surface and outer side surface of the battery tray 2 to form a bottom surface insulation layer 4-2 and a side surface insulation layer 4-3 with a thickness of 7mm respectively; thus obtaining the battery pack box.

[0061] The performance data for polyurethane foam are as follows: density 81 kg / m³ 3 The compressive strength is 838 kPa, the fire rating is V0, and the thermal conductivity at 25℃ is 0.025 W / m·k. The specific polyurethane foam formulation is shown in Table 2. The operating conditions of the high-pressure sprayer during spray foaming are the same as in Example 1.

[0062]

Example 4

[0063] A method for preparing a battery pack housing includes the following steps:

[0064] (a) Prepare the top cover 1 and battery tray 2;

[0065] (b) Apply Suprasec 2060 adhesive to the outer top surface of the upper cover plate 1, forming a coating of 50–100 g / m². 2 Top surface adhesive layer 3-1; 50-100 g / m² of adhesive is sprayed onto the outer bottom and outer sides of the battery tray 2. 2 The adhesive is used to form a bottom adhesive layer 3-2 and a side adhesive layer 3-3, respectively.

[0066] (c) Spray a 22mm thick polyurethane foam onto the outer side of the top adhesive layer 3-1 and the bottom adhesive layer 3-2 to form a top insulation layer 4-1 and a bottom insulation layer 4-2. Then, attach a 22mm thick polyurethane foam onto the outer side of the side adhesive layer 3-3 to form a side insulation layer 4-3.

[0067] (d) A steel plate is installed on the outside of the bottom insulation layer 4-2 to form a protective layer 5, thus obtaining the battery pack box;

[0068] The performance data for polyurethane foam are as follows: density 103 kg / m³ 3 The compressive strength is 1026 kPa, the fire rating is V0, and the thermal conductivity at 25℃ is 0.025 W / m·k. The specific polyurethane foam formulation is shown in Table 2. The operating conditions of the high-pressure sprayer during spray foaming are the same as in Example 1.

[0069]

Example 5

[0070] A method for preparing a battery pack housing includes the following steps:

[0071] (a) Prepare the top cover 1 and battery tray 2;

[0072] (b) Apply Suprasec 2060 adhesive to the outer top surface of the upper cover plate 1, forming a coating of 50–100 g / m². 2 Top surface adhesive layer 3-1; 50-100 g / m² of adhesive is sprayed onto the outer bottom and outer sides of the battery tray 2. 2 The adhesive is used to form a bottom adhesive layer 3-2 and a side adhesive layer 3-3, respectively.

[0073] (c) Spray a 27mm thick polyurethane foam onto the outer side of the top adhesive layer 3-1 and the bottom adhesive layer 3-2 to form the top insulation layer 4-1 and the bottom insulation layer 4-2. Then, attach a 27mm thick polyurethane foam onto the outer side of the side adhesive layer 3-3 to form the side insulation layer 4-3.

[0074] (d) A 3mm thick polyurea layer is sprayed on the outside of the bottom insulation layer 4-2 to form a protective layer 5, thus obtaining the battery pack box;

[0075] The performance data for polyurethane foam are as follows: density 125 kg / m³ 3 The compressive strength is 1458 kPa, the fire rating is V0, and the thermal conductivity at 25℃ is 0.026 W / m·k. The specific polyurethane foam formulation is shown in Table 2. The operating conditions of the high-pressure sprayer during spray foaming are the same as in Example 1.

[0076]

Example 6

[0077] The simulation experiment on the thermal insulation effect of the battery pack casing is as follows:

[0078] (a) Prepare 6 aluminum boxes with dimensions of 24cm×24cm×12cm to replace the battery pack box. The aluminum boxes are marked as 1#, 2#, 3#, 4#, 5# and 6# respectively. The reference cell material is placed inside the aluminum box, and temperature sensors are installed at the center, second outer edge and outer edge of the aluminum box respectively.

[0079] (b) Apply thermal insulation spraying treatment to the outer surface of aluminum boxes #2 to #6 according to the technical solutions of Examples 1 to 5 respectively;

[0080] (c) The aluminum box No. 1 without heat preservation treatment and the aluminum boxes No. 2 to No. 6 with heat preservation treatment were placed in an environment of 25°C for constant temperature treatment. Then they were placed in a constant temperature environment of -20°C. The time required for the temperature at different positions inside the aluminum box to drop from 25°C to 0°C was recorded as the temperature drop time. The specific results are shown in Table 3.

[0081] Table 2 shows the composition of polyurethane foam formulations in Examples 1-5 by weight.

[0082]

[0083]

[0084]

[0085] Table 3. Results of the aluminum box simulation experiment

[0086]

[0087] The battery pack housing manufactured using the technical solution of this invention has a fire rating of V0, exhibiting good fire resistance. Thermal insulation simulation experiments show that the aluminum boxes (2# to 6#) using the insulation schemes of Examples 1-5 exhibit minimal temperature decay with changes in low-temperature ambient temperature, a long temperature drop time, and good insulation effect. Combined with the use of polyurea or steel plates, the strength of the battery pack housing is improved, resulting in good resistance to stone impacts. The use of adhesive further enhances the bonding strength between the polyurethane foam and the battery tray or top cover, preventing the polyurethane foam from easily detaching from the substrate. This design can be used in the industrial production of battery pack housings for new energy electric vehicles.

Claims

1. A battery pack housing, comprising a top cover (1) and a battery tray (2), characterized in that, The top surface of the top cover plate (1) is provided with a top surface insulation layer (4-1), and the outer side of the battery tray (2) is provided with at least a bottom surface insulation layer (4-2); the top surface insulation layer (4-1) and the bottom surface insulation layer (4-2) are both polyurethane foam, composed of components A and B, with a weight ratio of component A to component B of 1:1 to 1.1; component A includes, by weight parts: 4 to 6 parts of melamine resin, 8 to 12 parts of high-functionality polyether polyol, 4 to 6 parts of rigid foam crosslinking agent, 40 to 45 parts of flame-retardant polyester polyol, 20 to 25 parts of flame retardant, and 0 parts of foam stabilizer. 5-1.5 parts, catalyst 4-6 parts, water 0.1-0.5 parts, physical foaming agent 10-13 parts, antioxidant 0.5-1 parts; wherein, the hydroxyl value of the melamine resin is 350-500 mgKOH / g, and the functionality is 2-4; the high-functionality polyether polyol is a polyether polyol with sorbitol or sucrose as the main initiator, and the hydroxyl value is 380-550 mgKOH / g; the rigid foam crosslinking agent is a polyether polyol with ethylenediamine and toluenediamine as the main initiators, the hydroxyl value is 435-800 mgKOH / g, and the viscosity is >4000 mPa·s; The flame-retardant polyester polyol has a functionality of 2-3 and a hydroxyl value of 210-280 mgKOH / g; component B is polymethylene polyphenyl isocyanate; and the density of the polyurethane foam is 40-130 kg / m³. 3 Compressive strength >300kPa, fire rating V0, thermal conductivity <0.03W / m·k@25℃.

2. The battery pack housing according to claim 1, characterized in that, The melamine resin is selected from at least one of CN-3360 or CN-4500; the high-functionality polyether polyol is selected from at least one of NJ-8238, NJ-6305C or NJ-4110A; the rigid foam crosslinking agent is selected from at least one of NJ-403 or TD405; the flame-retardant polyester polyol is selected from at least one of PS7001, Terol250 or HF8730; the flame retardant is selected from at least one of TEP, TCPP, TCEP, TDCPP, FR530 or DMMP; the foam stabilizer is selected from at least one of L6900, L6100, DC193, B8462, LK443 or LK221; the catalyst is selected from at least three of PC5, PC8, PC41, TMR-2, A33, K15, PC46, KAC or BDMAEE; and the physical blowing agent is selected from HFC 245fa, HFC365 / 227, HFO 1233zd or HFO. At least one of 1336mzz; the antioxidant is selected from at least one of Irganox 1076, Anox PP18 or Irganox 1135.

3. The battery pack housing according to claim 1, characterized in that, The battery tray (2) has a side insulation layer (4-3) on its outer side. This side insulation layer (4-3) is made of polyurethane foam with a density of 40-130 kg / m³. 3 Compressive strength >300kPa, fire rating V0, thermal conductivity <0.03W / m·k@25℃.

4. The battery pack housing according to claim 3, characterized in that, A top surface adhesive layer (3-1) is provided between the top cover plate (1) and the top surface insulation layer (4-1), a bottom surface adhesive layer (3-2) is provided between the bottom surface of the battery tray (2) and the bottom surface insulation layer (4-2), and a side surface adhesive layer (3-3) is provided between the side surface of the battery tray and the side surface insulation layer (4-3), and the amount of adhesive layer is 50-100g / m². 2 .

5. The battery pack housing according to claim 4, characterized in that, The adhesives used in the top adhesive layer (3-1), bottom adhesive layer (3-2) and side adhesive layer (3-3) have a viscosity of 2000-3800 mPa·s at 25℃, an NCO% of 13-18%, and a specific gravity of 1.12-1.20%.

6. The battery pack housing according to claim 1, characterized in that, The outer layer of the bottom insulation layer (4-2) is provided with a protective layer (5), which is selected from at least one of polyurea or steel plate.

7. The battery pack housing according to claim 3, characterized in that, The thickness of the top insulation layer (4-1), bottom insulation layer (4-2), and side insulation layer (4-3) is 2-30 mm, and the density is 40-60 kg / m³. 3 .

8. The method for preparing the battery pack housing according to claim 1, comprising the following steps: (a) Prepare the top cover (1) and battery tray (2); (b) Spray or attach polyurethane foam to the outer top surface of the top cover plate (1) to form a top surface insulation layer (4-1); (c) At least on the outer side of the bottom surface of the battery tray (2), polyurethane foam is sprayed or bonded to form a bottom insulation layer (4-2) to obtain the battery pack box; The polyurethane foam is composed of components A and B, with a weight ratio of component A to component B of 1:1 to 1.

1. Component A, by weight, includes: 4 to 6 parts melamine resin, 8 to 12 parts high-functionality polyether polyol, 4 to 6 parts rigid foam crosslinking agent, 40 to 45 parts flame-retardant polyester polyol, 20 to 25 parts flame retardant, 0.5 to 1.5 parts foam stabilizer, 4 to 6 parts catalyst, 0.1 to 0.5 parts water, 10 to 13 parts physical foaming agent, and 0.5 to 1 part antioxidant; wherein the hydroxyl value of the melamine resin is 350– 500 mg KOH / g, functionality 2-4; high-functionality polyether polyol is a polyether polyol with sorbitol or sucrose as the main initiator, hydroxyl value 380-550 mg KOH / g; rigid foam crosslinking agent is a polyether polyol with ethylenediamine and toluenediamine as the main initiators, hydroxyl value 435-800 mg KOH / g, viscosity >4000 mPa·s; flame-retardant polyester polyol has functionality 2-3, hydroxyl value 210-280 mg KOH / g; component B is polymethylene polyphenyl polyisocyanate.

9. The method for preparing the battery pack housing according to claim 8, characterized in that, Before spraying or bonding polyurethane foam, apply an adhesive with a viscosity of 2000–3800 mPa·s at 25°C, an NCO% of 13–18%, and a specific gravity of 1.12–1.20%.

10. The method for preparing the battery pack housing according to claim 8, characterized in that, During spraying, component A and component B are mixed evenly in a weight ratio of 1:1 to 1.1 using a high-pressure sprayer, atomized and foamed, and the foam is rapidly formed and cured to form a polyurethane foam layer. The operating conditions of the high-pressure sprayer are as follows: the distance between the spray gun nozzle and the substrate is 300 to 450 mm, the moving speed is uniform, the ambient temperature during spraying is 10 to 25°C, the relative humidity is less than 85%, and the wind speed during construction does not exceed 5 m / s.

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