Foaming glue filling processing method for power battery pack and power battery pack

Abstract

The application discloses a foaming glue filling processing method for a power battery pack and the power battery pack. The processing method comprises the following steps: placing the battery pack in a filling chamber and sealing and protecting the battery pack; after preheating, closing the filling chamber, vacuumizing to a first vacuum degree, and keeping pressure for a first preset time length, injecting two-component foaming glue materials from a filling port arranged on the battery pack; if the filling volume ratio is not less than a preset volume ratio value, stopping the filling, vacuumizing to a second vacuum degree, keeping pressure for a second preset time length, slowly recovering to normal pressure, controlling the battery pack to be heated to a first target temperature at a heating rate, and keeping the battery pack at the first target temperature for a third preset time length; according to a stepwise heating strategy, controlling the battery pack to be stepwise heated to a target solidification temperature and keeping the battery pack at the target solidification temperature for a fourth preset time length, and then according to a cooling rate, cooling the battery pack to room temperature. The processing method ensures the high consistency of the foaming glue performance in the battery packs produced in different batches and in different seasons, the total solidification time is controllable, the filling reliability is improved, and the processing method is beneficial to large-scale production.

Description

Foaming potting process for power battery packs and power battery packs Technical Field

[0001] This invention relates to the field of new energy technology, and in particular to a method for foaming adhesive injection processing for power battery packs and a power battery pack. Background Technology

[0002] In power battery packs, irregular gaps typically exist between the cell modules and the battery casing. To improve the overall integrity, structural strength, thermal management efficiency (thermal conductivity or insulation), and impact resistance of the battery pack, expanding foam is usually injected to fill these gaps. After curing, the expanding foam forms a lightweight, porous solid foam, serving as an adhesive, support, buffer, and thermal interface material. However, current injection methods face the following problems during expanding foam injection: 1. Air bubbles and cavities: The complex internal structure of the battery pack and numerous obstacles make it prone to cavitation during injection. Residual air bubbles or cavities create thermal resistance, leading to uneven heat dissipation, severely affecting thermal management consistency, and potentially causing thermal runaway in extreme cases. The chemical reaction of the expanding foam itself also produces gas; if not properly controlled, this can result in irregular, excessively large internal pores, reducing mechanical properties and insulation reliability. 2. Curing stress and cell deformation: Expanding foam undergoes volume expansion and contraction during the curing process. If the curing process is violent or uneven, the resulting expansion stress may compress the battery cell, leading to microscopic deformation of the cell casing or even micro-short circuits in the electrode sheets; contraction stress may cause the foam to peel off from the battery cell or casing, forming gaps and affecting heat conduction and structural rigidity. 3. Compatibility with sensitive components: The battery pack contains precision electronic components such as BMS (Battery Management System) circuitry and voltage acquisition harnesses. If the flowability, exothermic peak temperature, and curing pressure of the foam are not strictly controlled, the battery pack will inevitably be subject to corrosion, high-temperature damage, or mechanical compression. 4. Process efficiency and consistency: Battery packs are large in size and require high curing consistency; however, traditional natural curing or single-temperature-zone curing methods cannot guarantee the consistency of the foam performance inside each battery pack under mass production. Therefore, existing methods for foaming and potting battery packs suffer from low potting reliability. Summary of the Invention

[0003] This invention provides a method for foaming adhesive injection processing of power battery packs and a power battery pack, aiming to solve the problem of low injection reliability in existing methods for foaming adhesive injection processing of battery packs.

[0004] In a first aspect, embodiments of this application provide a method for foaming adhesive injection processing for a power battery pack, wherein the foaming adhesive injection processing method includes:

[0005] The battery pack is placed in the filling chamber and sealed for protection; the battery pack is a battery box equipped with battery modules.

[0006] The battery pack is preheated.

[0007] After closing the infusion chamber and evacuating to the first vacuum level, maintain the pressure for the first preset time.

[0008] According to the preset injection control strategy, the pre-mixed and initially degassed two-component foaming compound is injected through the injection port provided on the battery pack;

[0009] If the injection volume ratio is not less than the preset volume ratio value, pause the injection and evacuate to the second vacuum level and then maintain the pressure for the second preset time.

[0010] Slowly introduce gas into the infusion chamber to restore it to normal pressure;

[0011] The battery pack is heated to a first target temperature at a preset heating rate and kept at that temperature for a third preset duration.

[0012] The battery pack is heated to the target curing temperature in a stepped manner according to the stepped heating strategy and kept at that temperature for a fourth preset time.

[0013] The battery pack is cooled from the target curing temperature to room temperature according to a preset cooling rate.

[0014] Secondly, this application also provides a power battery pack, which is processed by the foaming process described in the first aspect above. The power battery pack includes a battery module and a battery housing. The battery module is fixedly disposed in the battery housing, and the electrical connection terminals of the battery module are electrically connected to the connection base in the battery housing. Each electrical connection terminal is provided with an insulating protective component.

[0015] The gap between the battery module and the battery housing is filled with foamed adhesive.

[0016] This invention provides a method for filling a power battery pack with expanding foam and a power battery pack. The method includes placing the battery pack in a filling chamber and sealing it; after preheating, closing the filling chamber and evacuating to a first vacuum level, then maintaining pressure for a first preset time; injecting a two-component expanding foam material through a filling port on the battery pack; if the filling volume ratio is not less than a preset volume ratio value, pausing the filling and evacuating to a second vacuum level, then maintaining pressure for a second preset time; slowly restoring to atmospheric pressure and then controlling the temperature rise of the battery pack to a first target temperature at a controlled heating rate, then maintaining that temperature for a third preset time; controlling the temperature rise of the battery pack stepwise to a target curing temperature according to a stepped heating strategy and maintaining that temperature for a fourth preset time, then cooling to room temperature according to a cooling rate. This method ensures a high degree of consistency in the performance of the expanding foam in battery packs produced in different batches and seasons, with controllable total curing time, significantly improving filling reliability and facilitating large-scale production. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 is a flowchart of a foaming adhesive injection process for a power battery pack provided in an embodiment of the present invention;

[0019] Figure 2 is an application effect diagram of the foaming adhesive injection processing method for power battery packs provided in the embodiment of the present invention. Detailed Implementation

[0020] The technical solutions of 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, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0022] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations.

[0023] This application discloses a method for filling a power battery pack with expanded polyurethane foam. Please refer to Figure 1. As shown in the figure, this application provides a method for filling a power battery pack with expanded polyurethane foam, which includes steps S1 to S9.

[0024] S1. Place the battery pack in the filling chamber and seal it for protection; the battery pack is a battery box equipped with battery modules.

[0025] The battery modules are assembled into the battery box to form a battery pack to be filled. At this stage, the battery pack is a semi-finished product with completed cell module assembly, electrical connections, and necessary insulation protection (such as attaching mica boards and insulating films as insulation protection components). The electrical connections involve connecting the electrical connection terminals of the battery modules to the connection sockets in the battery box. These electrical connection terminals include the positive terminal, negative terminal, temperature detection terminal, and internal pressure detection terminal. The battery pack is placed in the filling chamber, and sensitive areas such as the electrical interfaces (such as the positive and negative interfaces), BMS connectors, and pressure relief valves are sealed for protection. The BMS connectors are key components in the Battery Management System (BMS) used to connect the signal acquisition harness to the main control board, responsible for transmitting voltage, current, and temperature signals to ensure the accuracy and reliability of battery pack status monitoring. The pressure relief valve is used to relieve pressure on the battery pack; when the internal pressure of the battery pack is too high, the pressure relief valve can be opened to ensure the safety of the battery pack during use.

[0026] S2. Preheat the battery pack.

[0027] Furthermore, the battery pack is preheated, with the preheating temperature set to 28-35°C, and in a preferred embodiment, 30°C. Preheating the battery pack reduces the initial viscosity of the foamed adhesive during injection, thereby improving flowability and reducing thermal shock upon contact with the cold metal casing (i.e., the battery casing).

[0028] S3. Close the infusion chamber and evacuate to the first vacuum level, then maintain the pressure for the first preset time.

[0029] The filling chamber is closed and a vacuum is drawn; this step is also known as pre-vacuuming and pressure holding for leak detection. The vacuum is drawn to a first vacuum level and then held for a first preset time. The first vacuum level has a pressure of 5-10 kPa, and the first preset holding time can be 5-20 minutes. During this time, the sealing of the chamber and battery pack can be checked. If the chamber pressure rises during the pressure holding process, it indicates insufficient chamber sealing.

[0030] S4. According to the preset injection control strategy, the pre-mixed and initially degassed two-component foaming material is injected through the injection port provided on the battery pack.

[0031] Under conditions maintaining a first vacuum level, a pre-mixed and initially degassed two-component foaming compound is injected through a filling port on the battery pack using a filling gun. The two-component foaming compound is a reactive polyurethane foaming compound. Component A includes: a polymeric polyol, water as a chemical blowing agent, a catalyst composition for controlling the reactive gel and foaming balance, a surfactant, and a flame retardant; component B includes: isocyanate or its prepolymer. The compound can be injected at a uniform rate through one or more filling ports located at the bottom of the battery pack, or multiple filling ports located elsewhere, using a multi-head filling gun.

[0032] In a more specific embodiment, before injecting the pre-mixed and initially degassed two-component foamed adhesive into the injection port on the battery pack according to a preset injection control strategy, the method further includes: calculating injection speed information corresponding to the basic parameters of the battery pack according to the injection rate calculation rules in the injection control strategy; determining whether the injection speed information meets the single injection port judgment condition set in the injection control strategy; if the injection speed information meets the single injection port judgment condition, determining the corresponding injection speed range according to the injection speed information; determining the target injection speed according to the injection speed range and setting one injection port and at least one vent port; if the injection speed information does not meet the single injection port judgment condition, calculating the corresponding number of injection ports according to the injection port determination rules in the injection control strategy and the injection speed information; setting multiple injection ports and at least one vent port according to the number of injection ports; and calculating the target injection speed corresponding to the basic parameters according to the number of injection ports and the injection rate calculation rules.

[0033] The injection speed of the foamed rubber compound can be precisely calculated and controlled based on the whitening time, rising time, and internal volume of the battery pack to ensure that the foamed rubber compound rises smoothly, expelling rather than encapsulating air. To accurately determine the injection speed, this invention establishes a quantitative injection model based on the chemical properties of the rubber compound and the geometry of the battery pack. The injection speed is then obtained according to the injection control strategy corresponding to this quantitative injection model.

[0034] The infusion rate calculation rule in the infusion control strategy is used to calculate the infusion rate information corresponding to the basic parameters of the battery pack. The infusion rate information includes the basic infusion rate and the maximum allowable infusion rate.

[0035] In a more specific embodiment, the step of calculating the injection speed information corresponding to the basic parameters of the battery pack according to the injection rate calculation rule in the injection control strategy includes: determining the corresponding injection volume based on the basic parameters of the battery pack and the density ratio of the foamed rubber; calculating the corresponding basic injection speed based on the safety factor in the injection rate calculation rule, the injection volume, and the milky white time of the foamed rubber; determining the corresponding maximum allowable injection speed based on the rise speed threshold in the injection rate calculation rule and the basic parameters; and combining the basic injection speed and the maximum allowable injection speed as the corresponding injection speed information.

[0036] In practical applications, the filling must be completed within the "flowable time window" of the foamed compound. This window begins at the start of foamed compound mixing and ends at a safe percentage point (e.g., 80%) during the milky whitening time. Within this window, the compound viscosity is sufficiently low and its flowability is good, allowing it to fully fill complex spaces while also allowing the encapsulated air time to rise and escape. Therefore, the battery pack gap volume V can be obtained from the basic parameters of the battery pack. foam Battery pack gap volume V foam This refers to the total volume (cm³) of the foamed rubber compound, determined based on the clearance space in the battery pack design. The density ratio of the foamed rubber compound is used to determine the clearance volume V of the battery pack. foam The density ratio of the foamed rubber compound is determined based on the inherent properties of the foamed rubber compound for the corresponding injection volume. The density ratio is determined by the target density ρ of the foamed compound. foam (g / cm³) and the density ρ of the liquid adhesive before mixing and foaming liquid Dividing by (g / cm³), the infusion volume V can be calculated accordingly. liquid = V foam *(ρ foam / ρ liquid ), Injection volume V liquid That is, the volume (cm³) of liquid adhesive to be injected. After injection, the liquid adhesive foams and forms a solid adhesive.

[0037] Furthermore, the corresponding basic injection rate is calculated based on the safety factor, injection volume, and the milky whitening time of the foamed rubber compound in the injection rate calculation rules; the milky whitening time of the foamed rubber compound is determined by its own characteristics, and its milky whitening time T... creamThe time required from the start of mixing the rubber compound to its emulsification is the critical point in time when the rubber compound viscosity begins to rise sharply and loses its good fluidity.

[0038] The safe injection time window T can be determined based on the safety factor in the injection rate calculation rules and the milky white time of the foaming compound. safe (Unit: seconds), T safe =k1*T cream Where k1 is the safety factor, ranging from 0.6 to 0.8. This means that the pouring must be completed within 60%-80% of the time it takes for the rubber compound to reach its milky white state after mixing. Therefore, based on this safe pouring time window T... safe (Unit: seconds) and the infusion volume obtained from the above steps can be used to determine the corresponding basic infusion rate Q. total =V liquid / T safe Basic infusion rate Q total The unit is cm³ / s, and the basic grouting rate Q can also be expressed as a volumetric measure. total When converted to infusion rate in weight, the unit of the converted value is g / s (grams per second).

[0039] The maximum allowable injection rate is determined based on the rise velocity threshold and fundamental parameters in the injection rate calculation rules. To avoid turbulent air entrainment, the actual injection rate must be lower than a critical value, which is also the rise velocity threshold. This critical value is related to the fluidity of the rubber compound under vacuum and the narrowest flow channel size inside the battery pack. The minimum flow cross-sectional area along the rubber compound flow path is obtained from the fundamental parameters (the minimum flow cross-sectional area can be obtained through 3D modeling analysis based on the internal structure of the battery pack), and the maximum allowable injection rate Q is calculated. max = A min ×v max Maximum permissible infusion rate Q max That is, the maximum permissible infusion rate (cm³ / s) based on flow channel limitations; A min Minimum flow cross-sectional area; v max The maximum permissible infusion rate, also known as the maximum permissible interfacial rise rate (cm / s), is, for example, for most expanding foams, in a vacuum environment, v max ≤ 2.0cm / s to ensure laminar flow.

[0040] Combining the obtained baseline injection rate with the maximum permissible injection rate yields the injection rate information. Furthermore, by determining whether the obtained injection rate information satisfies the single injection port condition, the baseline injection rate Q within the injection rate information can be determined. total Is it not greater than the maximum permissible infusion rate Q? max If the basic injection rate Qtotal Not greater than the maximum permissible infusion rate Q max If the foundation injection rate Q is within the range of 100 mm, then the single injection port condition is met. total Greater than the maximum permissible infusion rate Q max If the condition is not met, then it is determined that the single injection port judgment condition is not met.

[0041] If the infusion rate information meets the single infusion port judgment condition, the corresponding infusion rate range can be determined based on the infusion rate information; for example, if the infusion rate range is determined to be [Q total Q max Then a target perfusion rate Q can be determined from the perfusion rate range. actual Target perfusion rate Q actual The value is within the filling speed range. Further, a filling port is set, such as a filling port at the bottom of the battery pack, and a corresponding exhaust port is set. The exhaust port can be located above the battery pack, so the filling port and the exhaust port correspond to each other; that is, the exhaust port should be set in the dead corner of the filling area last to be filled, to ensure that the air is completely driven to the exhaust port.

[0042] At this point, the number of injection ports must be no less than 2. Based on the number of injection ports, multiple injection ports and at least one vent port are set. The target injection speed corresponding to the basic parameters is calculated according to the number of injection ports and the injection rate calculation rules.

[0043] In a more specific embodiment, the step of calculating the corresponding number of infusion ports according to the infusion port determination rule in the infusion control strategy and the infusion speed information includes: calculating and rounding the infusion speed information according to the rounding calculation formula in the infusion port determination rule to obtain the corresponding number of infusion ports.

[0044] Specifically, the injection rate information can be calculated and rounded according to the rounding formula to obtain the corresponding number of injection ports. The rounding formula can be expressed as N. min = CEILING(Q total / Q max ), N min That is, the number of injection ports, where CEILING is the floor function. For example, if Q total / Q max If the ratio is 3.2, then N min The actual value should be 4, which means that 4 injection ports should be set.

[0045] Multiple filling ports and at least one venting port are configured according to the number of filling ports. The filling ports should ideally be located at the lowest point of the battery pack bottom or the geometric center of the filling area to ensure the adhesive fills radially from bottom to top or from the center outwards. The venting port must be located at the highest point of the filling area or the last dead corner to be filled, ensuring that air is completely driven out to the outlet. The arrangement of the filling and venting ports is determined based on the internal 3D model of the battery pack and fluid simulation to ensure a uniform flow front of the adhesive without dead zones.

[0046] Furthermore, the target infusion velocity corresponding to the basic parameters can be calculated based on the number of infusion ports and the infusion rate calculation rules. The target infusion velocity obtained at this time corresponds to the infusion velocity information during multi-head infusion operations. Specifically, the target infusion velocity includes the infusion velocity of each infusion port, which is also the flow rate Q of each infusion port. i The flow rate Q at each injection port i The volume V of the sub-region to be filled can be determined based on the injection port volume in the basic parameters. i Proportional allocation: Q i = Q actual ×(V i / V liquid ), where Q actual =N min ×Q max Q actual This represents the actual injection rate.

[0047] S5. If the injection volume ratio is not less than the preset volume ratio value, pause the injection and evacuate to the second vacuum level and then maintain the pressure for the second preset time.

[0048] During the injection process, the injection volume ratio continuously increases. The injection volume ratio is the ratio of the volume of the injected liquid adhesive to the total injection volume V. liquid The ratio between the two. If the infused volume ratio is not less than the preset volume ratio value, then infusion should be paused; for example, the preset volume ratio value can be set to 90%-95%. After stopping infusion, evacuate to a second vacuum level and maintain the pressure for a second preset time, where the pressure of the second vacuum level is lower than that of the first vacuum level, for example, the pressure of the second vacuum level can be set to ≤2 kPa; the second preset time can be set to 180s. At the end of the entire infusion process, sufficient time should be reserved for a "secondary vacuum degassing" operation, which must meet the following requirements: T fill +T1 <T rise Among them, T fill T represents the actual infusion time. fill = V liquid / Q actual T1 is the second preset duration, which is the secondary high-vacuum degassing and pressure holding time of 180 seconds. riseThis refers to the rise time of the rubber compound (the time it takes for the rubber compound to stop foaming and expanding). This criterion ensures that during high-vacuum degassing, the rubber compound is still in the middle of foaming, making it easier for bubbles to escape. Final verification confirms T. fill +T1 <T rise If the condition is not met, k1 needs to be adjusted accordingly (e.g., reduce k1) or a slower-reacting compound needs to be selected.

[0049] By evacuating to a second vacuum level and maintaining pressure for a second preset time, the high vacuum environment promotes the rapid escape, expansion, and removal of dissolved gases and microbubbles generated in the early stages of the chemical reaction from the injected adhesive. At the same time, it reserves space for the final expansion and foaming of the adhesive, avoiding excessive expansion and internal pressure.

[0050] S6. Slowly introduce gas into the infusion chamber to restore it to normal pressure.

[0051] Gas is then slowly introduced into the filling chamber to restore atmospheric pressure; the introduced gas can be dry air or nitrogen. Under atmospheric pressure, the remaining adhesive completes its final foaming and expansion process, filling all remaining spaces. An atmospheric pressure environment is conducive to the formation of a uniform, dense closed-cell or open-cell foam structure.

[0052] S7. Control the battery pack to heat up to the first target temperature at a preset heating rate and keep it at that temperature for a third preset duration.

[0053] The temperature curves of the curing process corresponding to steps S7 to S9 are shown in Figure 2. First, the battery pack is heated to the first target temperature at a pre-set heating rate and held at that temperature for a third preset time. Specifically, the heating rate is 0.4-0.6℃ / min, and in a preferred embodiment, it can be set to 0.5℃ / min. If the internal temperature of the battery pack is 30℃, the temperature is slowly increased to the first target temperature T1 (e.g., T1 is set to 40℃) at this heating rate. For example, the third preset time H1 can be set to 120 minutes. The purpose of this slow heating stage is to provide a mild and long-term thermal environment during the "green strength" stage, when the foaming adhesive has just completed chemical foaming and has very low mechanical strength, to promote initial cross-linking of the molecular chains and achieve stress relaxation. This stage effectively releases the initial expansion stress generated during the foaming process, preventing stress from being directly transferred to the battery cell, and laying a uniform foundation for subsequent curing.

[0054] S8. Control the battery pack to be heated to the target curing temperature in a stepped manner according to the stepped heating strategy and keep it heated for a fourth preset time.

[0055] Furthermore, the battery pack is controlled to rise from the first target temperature to the target curing temperature and held at that temperature for a fourth preset time according to a stepped heating strategy. Since it is a stepped heating, the process of rising from the first target temperature to the target curing temperature includes at least two temperature steps.

[0056] In a more specific embodiment, step S8 specifically includes the following sub-steps: heating from the first target temperature to an intermediate temperature at a first rate controlled by the stepped heating strategy and holding at that temperature for a preset holding time, wherein the preset holding time is less than the fourth preset time; heating from the intermediate temperature to the target curing temperature at a second rate controlled by the stepped heating strategy and holding at that temperature for a fourth preset time; wherein the target curing temperature is 50-55℃.

[0057] Specifically, the first rate in the stepped heating strategy control can be used to heat the temperature from the first target temperature to the intermediate temperature, where the first rate is equal to the heating rate. After heating to the intermediate temperature, a preset holding time is set, which is less than a fourth preset time; for example, the intermediate temperature T2 can be set to 50℃, and the preset holding time H2 can be set to 60 minutes.

[0058] The temperature is increased from the intermediate temperature to the target curing temperature using a step-by-step heating strategy at a second rate, where the second rate is less than the first rate. After reaching the target curing temperature, the temperature is held for a fourth preset time; the target curing temperature T3 is 50-55℃, and in a preferred embodiment, the target curing temperature can be set to 50℃. The fourth preset time H3 can be set to 120 minutes. In specific applications, the second rate can be set to 0.3-0.5 times the heating rate; for example, if the first rate is set to 0.5℃ / min, the second rate can be set to 0.2℃ / min accordingly.

[0059] The main purpose of this stepped temperature increase step is to avoid the violent vaporization of residual foaming agent inside the foam or excessive differences in curing rates between different areas caused by rapid heating. The T2 temperature plateau helps thicker areas keep pace with the overall curing process, while the T3 temperature plateau ensures the foam reaches fully cured mechanical strength, bond strength, and thermal stability. T3 temperature must be strictly controlled to not exceed 55℃ to protect the battery cell and internal electronic components from high-temperature damage.

[0060] Specifically, the curing time is obtained by summing the third preset time, the preset heat preservation time, and the fourth preset time; the curing time is not less than the product of the base thickness and the curing coefficient, the base thickness is the thickness of the thickest part of the foamed adhesive injected into the battery pack, and the curing coefficient is 8-15 min / mm.

[0061] The curing time is obtained by summing the third preset time H1, the preset insulation time H2, and the fourth preset time H3. The curing time is also the total curing time of the foamed adhesive. There is a correlation between the curing time and the base thickness: curing time ≥ k × d; where k is the curing absorption, ranging from 8-15 min / mm, and d is the base thickness, which is the thickness of the thickest part of the foamed adhesive poured into the battery pack. Determining the curing time in this way ensures that the thicker sections of the adhesive within the battery pack are fully cured.

[0062] S9. Control the battery pack to cool down from the target curing temperature to room temperature according to the preset cooling rate.

[0063] The cooling process is further executed to control the cooling rate of the battery pack from the target curing temperature to room temperature, wherein the cooling rate is less than the second rate. For example, the cooling rate can be set to 0.1℃ / min, slowly cooling from T3 to a temperature T4 (30℃) close to room temperature through an extremely low rate. The purpose of slow cooling is to fully release the thermal stress caused by the difference in thermal expansion coefficients between the foam, battery cell, and housing. This process can significantly reduce the risk of interface delamination between the foam and the housing / module after cooling, ensuring dimensional stability and constant interfacial contact pressure during long-term use, and maintaining stable thermal resistance.

[0064] This invention also provides a power battery pack, which is processed by the foaming process described in the above embodiments. The power battery pack includes a battery module and a battery housing. The battery module is fixedly disposed in the battery housing, and the electrical connection terminals of the battery module are electrically connected to the connection base in the battery housing. Each electrical connection terminal is provided with an insulating protective component. The gap between the battery module and the battery housing is filled with foaming material.

[0065] The beneficial effects of this invention are as follows: Elimination of internal defects: Through a combined process of "dynamic vacuum infusion + secondary high-vacuum degassing," air bubbles and cavities within the complex structure of the battery pack are eliminated to the greatest extent possible, achieving defect-free filling and ensuring the uniformity and reliability of thermal conduction / insulation. Protection of cells and components: A gentle curing temperature profile (T3 ≤ 55℃) and an extremely slow cooling rate throughout the process minimize stress and thermal damage to the cells, protecting sensitive components such as the BMS. Optimization of mechanical properties: The combination of "low-temperature long-term stress relaxation" and "ultra-low-speed cooling" systematically releases internal stress throughout the foaming-curing-cooling process, improving the adhesion durability between the foam and the cell modules and housing, and preventing interface peeling or cell deformation due to stress. Improved production consistency and efficiency: Standardized program control replaces uncontrollable curing dependent on ambient temperature and time, ensuring high consistency of the foam performance within battery packs produced in different batches and seasons. Furthermore, the total curing time is predictable and optimizable, facilitating large-scale production.

[0066] This invention provides a method for vacuum potting and staged temperature-rate curing of encapsulant for battery packs. This method employs a precisely designed synergistic process of "vacuum potting - staged temperature-rate curing" to minimize large air bubbles during the vacuum potting stage, and then precisely controls the heating / cooling rates and the heat preservation platform in stages during the subsequent curing stage. This potting process combines "vacuum control matching foaming characteristics" with a "stress-guided temperature-rate curing curve" to achieve defect-free filling of the complex internal space of the battery pack with the foamed adhesive, minimize curing stress, protect the cells and sensitive components, and ultimately obtain a highly consistent and reliable integrated battery pack structure.

[0067] This invention provides a method for filling a power battery pack with expanding foam and a power battery pack. The method includes placing the battery pack in a filling chamber and sealing it; after preheating, closing the filling chamber and evacuating to a first vacuum level, then maintaining pressure for a first preset time; injecting a two-component expanding foam material through a filling port on the battery pack; if the filling volume ratio is not less than a preset volume ratio value, pausing the filling and evacuating to a second vacuum level, then maintaining pressure for a second preset time; slowly restoring to atmospheric pressure and then controlling the temperature rise of the battery pack to a first target temperature at a controlled heating rate, then maintaining that temperature for a third preset time; controlling the temperature rise of the battery pack stepwise to a target curing temperature according to a stepped heating strategy and maintaining that temperature for a fourth preset time, then cooling to room temperature according to a cooling rate. This method ensures a high degree of consistency in the performance of the expanding foam in battery packs produced in different batches and seasons, with controllable total curing time, significantly improving filling reliability and facilitating large-scale production.

[0068] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for foaming adhesive injection processing for power battery packs, characterized in that, The foaming adhesive injection process includes: placing a battery pack in an injection chamber and sealing it for protection; the battery pack is a battery box equipped with battery modules; preheating the battery pack; closing the injection chamber and evacuating it to a first vacuum level and holding it at pressure for a first preset time; injecting pre-mixed and pre-degassed two-component foaming adhesive through an injection port on the battery pack according to a preset injection control strategy; if the injection volume ratio is not less than a preset volume ratio value, pausing the injection and evacuating it to a second vacuum level and holding it at pressure for a second preset time; slowly introducing gas into the injection chamber to restore atmospheric pressure; controlling the battery pack to heat up to a first target temperature at a preset heating rate and holding it at that temperature for a third preset time; controlling the battery pack to heat up to a target curing temperature in a stepwise manner according to a stepwise heating strategy and holding it at that temperature for a fourth preset time; and controlling the battery pack to cool down from the target curing temperature to room temperature according to a preset cooling rate.

2. The foaming compound injection processing method for power battery packs according to claim 1, characterized in that, The step of controlling the battery pack to be heated to the target curing temperature in a stepped manner according to the stepped heating strategy and holding it at that temperature for a fourth preset time includes: heating the battery pack from the first target temperature to an intermediate temperature at a first rate controlled by the stepped heating strategy and holding it at that temperature for a preset holding time, wherein the preset holding time is less than the fourth preset time; heating the battery pack from the intermediate temperature to the target curing temperature at a second rate controlled by the stepped heating strategy and holding it at that temperature for a fourth preset time; wherein the target curing temperature is 50-55℃.

3. The foaming compound injection processing method for power battery packs according to claim 2, characterized in that, The curing time is obtained by summing the third preset time, the preset heat preservation time, and the fourth preset time; the curing time is not less than the product of the base thickness and the curing coefficient, the base thickness is the thickness of the thickest part of the foamed material injected into the battery pack, and the curing coefficient is 8-15 min / mm.

4. The foaming process for power battery packs according to claim 3, characterized in that, The first rate is equal to the heating rate, and the second rate is less than the first rate; the cooling rate is less than the second rate.

5. The foaming compound injection processing method for power battery packs according to claim 4, characterized in that, The heating rate is 0.4-0.6℃ / min, and the second rate is 0.3-0.5 times the heating rate.

6. The foaming process for power battery packs according to any one of claims 1-5, characterized in that, Before injecting the pre-mixed and initially degassed two-component foamed adhesive into the injection port on the battery pack according to the preset injection control strategy, the method further includes: calculating injection speed information corresponding to the basic parameters of the battery pack according to the injection rate calculation rules in the injection control strategy; determining whether the injection speed information meets the single injection port judgment condition set in the injection control strategy; if the injection speed information meets the single injection port judgment condition, determining the corresponding injection speed range according to the injection speed information; determining the target injection speed according to the injection speed range and setting one injection port and at least one vent port; if the injection speed information does not meet the single injection port judgment condition, calculating the corresponding number of injection ports according to the injection port determination rules in the injection control strategy and the injection speed information; setting multiple injection ports and at least one vent port according to the number of injection ports; calculating the target injection speed corresponding to the basic parameters according to the number of injection ports and the injection rate calculation rules.

7. The foaming process for power battery packs according to claim 6, characterized in that, The step of calculating the injection speed information corresponding to the basic parameters of the battery pack according to the injection rate calculation rule in the injection control strategy includes: determining the corresponding injection volume based on the basic parameters of the battery pack and the density ratio of the foamed rubber; calculating the corresponding basic injection speed based on the safety factor in the injection rate calculation rule, the injection volume, and the milky white time of the foamed rubber; determining the corresponding maximum allowable injection speed based on the rise speed threshold in the injection rate calculation rule and the basic parameters; and combining the basic injection speed and the maximum allowable injection speed as the corresponding injection speed information.

8. The foaming process for power battery packs according to claim 7, characterized in that, The step of calculating the corresponding number of infusion ports according to the infusion port determination rule in the infusion control strategy and the infusion speed information includes: calculating and rounding the infusion speed information according to the rounding calculation formula in the infusion port determination rule to obtain the corresponding number of infusion ports.

9. The foaming process for power battery packs according to claim 8, characterized in that, The preheating temperature during the preheating treatment of the battery pack is 28-35℃.

10. A power battery pack, characterized in that, The power battery pack is processed using the foaming adhesive injection method as described in any one of claims 1-9; the power battery pack includes a battery module and a battery housing; the battery module is fixedly disposed in the battery housing, and the electrical connection terminals of the battery module are electrically connected to the connection seat in the battery housing, and each electrical connection terminal is provided with an insulating protective component; the gap between the battery module and the battery housing is filled with foaming adhesive.

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