Battery explosion-proof valve calibration method

Abstract

The application discloses a battery explosion-proof valve checking method, and belongs to the technical field of batteries. The battery explosion-proof valve checking method comprises the following steps: obtaining the gas production rate and gas production composition under the thermal runaway state of the battery. The valve opening pressure of the explosion-proof valve is preset, and the total area of the explosion-proof valve is calculated according to the gas production rate and the gas production composition under the thermal runaway state of the battery. Then, the preset structure type, position and quantity of the explosion-proof valve are checked based on the total area of the explosion-proof valve, so as to verify whether the preset structure type, position and quantity of the explosion-proof valve meet the use requirements. If the use requirements are met, the preset structure type, position and quantity of the explosion-proof valve can be directly used for product production and processing. If the use requirements are not met, the valve opening pressure of the explosion-proof valve can be re-preset, and the re-preset structure type, position and quantity of the explosion-proof valve are checked. Samples need not to be made for testing, and the development cycle of the structural part can be greatly shortened.

Description

Technical Field

[0001] This application belongs to the field of battery technology, and specifically relates to a method for calibrating a battery explosion-proof valve. Background Technology

[0002] Explosion-proof valves are safety structures designed for battery safety. A well-designed explosion-proof valve can instantly expel heat from the battery in the event of thermal runaway, preventing the accumulation of large amounts of gas and heat inside the battery and thus avoiding serious explosions and fires. The determination of whether the structure, location, and quantity of explosion-proof valves meet design specifications is based on empirical estimations combined with experimental verification. However, using this method to determine the structure, location, and quantity of explosion-proof valves often significantly prolongs the development cycle of structural components and increases development costs. Summary of the Invention

[0003] Purpose of the invention: This application provides a method for verifying battery explosion-proof valves, aiming to overcome the technical problem that determining the structural type, location, and quantity of explosion-proof valves would greatly prolong the development cycle of structural components.

[0004] Technical solution: The battery explosion-proof valve calibration method described in this application includes:

[0005] Obtain the gas generation rate and composition under battery thermal runaway conditions;

[0006] Based on the preset opening pressure of the explosion-proof valve, as well as the gas production rate and gas composition under the thermal runaway state of the battery, the total area of ​​the explosion-proof valve is obtained.

[0007] Based on the total area of ​​the explosion-proof valve, verify whether the opening pressure of the explosion-proof valve under different structural types, positions and quantities meets the preset opening pressure requirements.

[0008] In some embodiments, obtaining the total area of ​​the explosion-proof valve based on the preset opening pressure of the explosion-proof valve, and the gas generation rate and composition under the battery thermal runaway state, includes:

[0009] The pressure P3 generated by the maximum gas production during the entire life cycle of the battery during normal use and the minimum pressure P4 under the thermal runaway state of the battery are obtained. The preset opening pressure P1 of the explosion-proof valve is obtained, satisfying: P3 < P1 ≤ P4.

[0010] In some embodiments, obtaining the total area of ​​the explosion-proof valve based on the preset opening pressure of the explosion-proof valve, and the gas generation rate and composition under the battery thermal runaway state, includes:

[0011] Based on the gas production rate and composition under the thermal runaway state of the battery, the isochoric specific heat and isobaric specific heat of the mixed gas are obtained.

[0012] Based on the specific heat at constant volume and specific heat at constant pressure of the mixed gas, the critical pressure of the critical flow rate of the mixed gas is obtained;

[0013] The total area of ​​the explosion-proof valve is obtained based on the preset opening pressure of the explosion-proof valve and the critical pressure of the critical flow rate of the mixed gas.

[0014] In some embodiments, obtaining the critical pressure of the critical flow rate of the mixed gas based on its isochoric specific heat and isobaric specific heat includes:

[0015] The critical pressure at which the critical flow rate of the gas mixture is critical is obtained using the following formula:

[0016] K = C P / C V ;

[0017]

[0018] Among them, P Critical P5 is the ambient pressure, C is the critical pressure at the critical flow rate of the gas mixture, and P5 is the critical pressure at the critical flow rate of the gas mixture. P C is the specific heat at constant pressure of the gas mixture. V This is the specific heat at constant volume of the gas mixture.

[0019] In some embodiments, obtaining the total area of ​​the explosion-proof valve based on the preset opening pressure of the explosion-proof valve and the critical pressure of the critical flow rate of the mixed gas includes:

[0020] If the preset opening pressure of the explosion-proof valve is greater than the critical pressure of the critical flow rate of the mixed gas, the total area of ​​the explosion-proof valve can be obtained by the following formula:

[0021]

[0022] Where A is the total area of ​​the explosion-proof valve, W is the gas generation rate under the thermal runaway state of the battery, C is the specific heat coefficient, and K is the specific heat coefficient. d Where P1 is the release coefficient, and K is the preset opening pressure of the explosion-proof valve. b is the back pressure correction factor, Kc is the combination correction factor, T is the discharge temperature of the mixed gas, Z is the compressibility factor of the mixed gas, and M is the average molecular weight of the mixed gas.

[0023] In some embodiments, obtaining the total area of ​​the explosion-proof valve based on the preset opening pressure of the explosion-proof valve and the critical pressure of the critical flow rate of the mixed gas includes:

[0024] If the preset opening pressure of the explosion-proof valve is less than the critical pressure of the critical flow rate of the mixed gas, the total area of ​​the explosion-proof valve can be obtained by the following formula:

[0025]

[0026] K = C P / C V ;

[0027] r = P6 / P1;

[0028] Where A is the total area of ​​the explosion-proof valve, W is the gas generation rate under the thermal runaway state of the battery, F2 is the flow coefficient of the mixed gas below the critical flow rate, and K d K is the discharge coefficient. c The combined correction coefficients are: T is the venting temperature of the gas mixture, Z is the compressibility coefficient of the gas mixture, M is the average molecular weight of the gas mixture, P1 is the preset opening pressure of the explosion-proof valve, P6 is the back pressure of the explosion-proof valve, and C... P C is the specific heat at constant pressure of the gas mixture. V This is the specific heat at constant volume of the gas mixture.

[0029] In some embodiments, verifying whether the opening pressure of the explosion-proof valves under different structural types, positions, and quantities meets the preset opening pressure requirement based on the total area of ​​the explosion-proof valves includes:

[0030] Obtain the tensile stress-strain curve and the failure strain of the explosion-proof valve material;

[0031] The battery is modeled based on the total area of ​​the explosion-proof valve, and the explosion-proof valve is preset in different structural types, positions and quantities to obtain the finite element model of the battery.

[0032] Based on the finite element model of the battery under different structural types, positions, and quantities of the explosion-proof valve, as well as the tensile stress-strain curve of the explosion-proof valve material and the failure strain of the explosion-proof valve material, it is verified whether the opening pressure of the explosion-proof valve under different structural types, positions, and quantities meets the requirements of the preset opening pressure.

[0033] In some embodiments, obtaining the tensile stress-strain curve of the explosion-proof valve material and the failure strain of the explosion-proof valve material includes:

[0034] Obtain a sample of the explosion-proof valve, mark the two ends of the sample as clamping parts, and pull the clamping parts to both sides along the length direction of the sample to perform a tensile test on the sample and obtain the tensile force-displacement curve of the sample.

[0035] Based on the tensile displacement curve of the sample, the tensile stress-strain curve of the explosion-proof valve material and the failure strain of the explosion-proof valve material are obtained.

[0036] In some embodiments, obtaining the tensile stress-strain curve of the explosion-proof valve material and the failure strain of the explosion-proof valve material includes:

[0037] The tensile stress-strain curve and the failure strain of the explosion-proof valve material are obtained using the following formulas:

[0038] ε=ΔL / L0;

[0039] S = (h * t * L0) / (ΔL + L0);

[0040] σ = F / S;

[0041] Wherein, ε is the tensile strain of the test part, ΔL is the tensile displacement of the test part, L0 is the initial length of the test part before stretching, S is the total cross-sectional area of ​​the test part during the stretching process, h is the width of the test part, t is the initial thickness of the test part, σ is the tensile stress of the test part, and F is the tensile force of the test part during the test process.

[0042] When the test section breaks, ΔL reaches its maximum value ΔL. max The failure strain ε of the explosion-proof valve material max =ΔL max / L0.

[0043] In some embodiments, the step of verifying whether the opening pressure of the explosion-proof valve under different structural types, locations, and quantities meets the preset opening pressure requirement based on the finite element model of the battery under different structural types, locations, and quantities of the explosion-proof valve, as well as the tensile stress-strain curve of the explosion-proof valve material and the failure strain of the explosion-proof valve material, includes:

[0044] Obtain the simulated opening pressure P2 of the explosion-proof valve under different structural types, positions, and quantities; calculate the preset opening pressure P1 of the explosion-proof valve and the simulated opening pressure P2 of the explosion-proof valve; if the following conditions are met:

[0045]

[0046] The pre-set explosion-proof valves meet the battery's usage requirements in terms of structure, location, and quantity.

[0047] If the following conditions are met:

[0048]

[0049] If the preset explosion-proof valve does not meet the usage requirements of the battery in terms of structure, location, or quantity, it needs to be reset.

[0050] Beneficial effects: The battery explosion-proof valve verification method of this application includes: obtaining the gas generation rate and gas composition under battery thermal runaway state; obtaining the total area of ​​the explosion-proof valve based on the preset opening pressure of the explosion-proof valve and the gas generation rate and gas composition under battery thermal runaway state; and verifying whether the opening pressure of the explosion-proof valve under different structural types, positions and quantities meets the requirements of the preset opening pressure based on the total area of ​​the explosion-proof valve. The opening pressure of the explosion-proof valve is preset, and the total area of ​​the explosion-proof valve is calculated based on the gas generation rate and composition under battery thermal runaway conditions. Then, based on the total area of ​​the explosion-proof valve, the preset structure, position, and quantity of the explosion-proof valve are verified to check whether the preset structure, position, and quantity of the explosion-proof valve meet the usage requirements. If the usage requirements are met, the preset structure, position, and quantity of the explosion-proof valve can be directly used for product manufacturing. If the usage requirements are not met, the opening pressure of the explosion-proof valve can be preset again, and the structure, position, and quantity of the preset explosion-proof valve can be verified. There is no need to make samples for testing, which can greatly shorten the development cycle of structural components and reduce development costs. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0052] Figure 1 A schematic flowchart illustrating the battery explosion-proof valve verification method provided in this application embodiment;

[0053] Figure 2 This is a schematic diagram of the structure of the sample provided in the embodiments of this application;

[0054] Figure 3 Tensile stress-strain curve of the explosion-proof valve material provided in the embodiments of this application;

[0055] Reference numerals: 10-sample; 11-test section; 12-clamping section; X-length direction. Detailed Implementation

[0056] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0057] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, and "at least one" can mean one, two, or more, unless otherwise explicitly specified.

[0058] Explosion-proof valves are safety structures designed for battery safety. A well-designed explosion-proof valve can instantly expel heat from the battery in the event of thermal runaway, preventing the accumulation of large amounts of gas and heat inside the battery and thus avoiding serious explosions and fires. The design of explosion-proof valves must meet two important criteria: first, the valve should not open during normal battery use; second, the valve should open promptly and release gas quickly in the event of thermal runaway. By setting appropriate parameters such as the structure, location, quantity, and area of ​​the explosion-proof valve, the designed valve can meet these two important criteria.

[0059] Currently, the method for judging whether the selection, location, quantity, and area of ​​different explosion-proof valves can meet the design specifications is as follows: Based on a large amount of measured data, the relationship between the explosion-proof valve structure and the valve opening pressure, as well as the discharge capacity under different explosion-proof valve area designs, is summarized. Based on experience, the explosion-proof valve structure and area are initially designed. After the sample is manufactured, a pressure test is conducted to verify whether the initial design meets the usage requirements. However, using this method means that after the design is frozen, it is still necessary to wait for the sample to be manufactured before conducting tests. The original design scheme is continuously adjusted based on the test results, and the direction of adjustment can only be judged based on experience. There are cases where repeated tests fail to meet the usage requirements, resulting in high costs and a very long development cycle.

[0060] In view of the above, this application provides a battery explosion-proof valve calibration method to overcome at least one of the above-mentioned technical problems.

[0061] Please see Figure 1 In this embodiment of the application, the verification method for the battery explosion-proof valve includes:

[0062] S101: Obtain the gas generation rate and gas composition under battery thermal runaway conditions;

[0063] S102: Based on the preset opening pressure of the explosion-proof valve, as well as the gas generation rate and gas composition under the thermal runaway state of the battery, obtain the total area of ​​the explosion-proof valve.

[0064] S103: Based on the total area of ​​the explosion-proof valve, verify whether the opening pressure of the explosion-proof valve under different structural types, positions and quantities meets the preset opening pressure requirements.

[0065] Understandably, when designing the structure, location, and number of explosion-proof valves on a battery, the gas generation rate and composition under battery thermal runaway conditions can be obtained based on tests and measurements from devices (such as adiabatic calorimeters). The opening pressure of the explosion-proof valve can be preset based on experience, and the total area of ​​the explosion-proof valve can be calculated based on the gas generation rate and composition under battery thermal runaway conditions. The calculated total area of ​​the explosion-proof valve is the area required to meet the preset opening pressure of the explosion-proof valve. Then, based on experience and other design parameters, the structure, location, and quantity of the explosion-proof valves are preset. Using the calculated total area of ​​the explosion-proof valves as a basis, the preset structure, location, and quantity are verified to ensure they meet the usage requirements. If they do, the preset structure, location, and quantity can be directly used for product manufacturing. If they do not meet the requirements, the valve opening pressure can be re-preset, the new total area of ​​the explosion-proof valves can be calculated, and the newly preset structure, location, and quantity are then verified. This method eliminates the need to manufacture battery samples with preset explosion-proof valves, reducing battery development costs. Since testing the designed explosion-proof valves does not require sample production, this method allows for rapid verification of different preset structures, locations, and quantities of explosion-proof valves to ensure they meet usage requirements. It also eliminates the need to manufacture physical products based on each preset design (including structure, location, and quantity), significantly shortening the development cycle of structural components.

[0066] In conjunction with the above embodiments, in some embodiments, the total area of ​​the explosion-proof valve is obtained based on the preset opening pressure of the explosion-proof valve, as well as the gas production rate and composition under battery thermal runaway conditions. This includes: obtaining the pressure P3 generated by the maximum gas production during the entire life cycle of the battery under normal use and the minimum pressure P4 under battery thermal runaway conditions; and obtaining the preset opening pressure P1 of the explosion-proof valve, satisfying: P3 < P1 ≤ P4. It is understood that, through experience, testing, and evaluation, the pressure P3 generated by the maximum gas production during the entire life cycle of the battery under normal use is obtained. The preset opening pressure P1 of the explosion-proof valve needs to be greater than P3 so that the internal pressure of the battery will not break through the explosion-proof valve during normal use. Meanwhile, through experience, testing, and evaluation, the minimum pressure P4 under battery thermal runaway is obtained. The preset opening pressure P1 of the explosion-proof valve must be less than or equal to P4. When the battery experiences thermal runaway, the internal pressure of the battery will reach P4 or even higher. The internal pressure of the battery during thermal runaway can break through the explosion-proof valve, causing the explosion-proof valve to open and release the gas pressure inside the battery, thereby improving the battery's safety.

[0067] In conjunction with the above embodiments, in some embodiments, the total area of ​​the explosion-proof valve is obtained based on the preset opening pressure of the explosion-proof valve, as well as the gas generation rate and gas composition under battery thermal runaway conditions, including the following steps:

[0068] Based on the gas production rate and composition under battery thermal runaway conditions, the isochoric specific heat and isobaric specific heat of the mixed gas are obtained.

[0069] The critical pressure of the gas mixture is obtained based on its isochoric specific heat and isobaric specific heat.

[0070] The total area of ​​the explosion-proof valve is obtained based on the preset opening pressure of the explosion-proof valve and the critical pressure of the critical flow rate of the mixed gas.

[0071] Understandably, after experimentally measuring and calculating the gas production rate and composition under battery thermal runaway conditions, the isochoric specific heat and isobaric specific heat of the mixed gas can be calculated based on the gas production rate and composition. Then, based on the isochoric specific heat and isobaric specific heat of the mixed gas, along with other relatively conventional parameter information, the critical pressure of the mixed gas at its critical flow rate can be calculated. At this point, it is necessary to compare the magnitude of the critical pressure of the mixed gas at its critical flow rate with the magnitude of the preset opening pressure of the explosion-proof valve. Based on the comparison result, different calculation methods are used to calculate the total area of ​​the explosion-proof valve.

[0072] In conjunction with the above embodiments, in some embodiments, the critical pressure of the critical flow rate of the mixed gas is obtained based on the isochoric specific heat and isobaric specific heat of the mixed gas, including:

[0073] The critical pressure at which the critical flow velocity of the gas mixture is critical can be obtained using the following formula:

[0074] K = C P / C V ;

[0075]

[0076] Among them, P Critical P5 is the ambient pressure, C is the critical pressure at the critical flow rate of the gas mixture, and P5 is the critical pressure at the critical flow rate of the gas mixture. P C is the specific heat at constant pressure of the gas mixture. V This is the specific heat at constant volume of the gas mixture.

[0077] Among them, the specific heat at constant volume C of the mixed gas V and specific heat at constant pressure C P The calculation formula is as follows:

[0078] C P (T)=a+bT+cT 2 +dT 3 +e / T 2 ;

[0079] C P.mix =∑C p.i X i =∑a i X i +∑b i X i T+∑c i X i T 2 +∑d i X i T 3 +∑e i X i T -2 ;

[0080] Where T is the temperature at the exhaust port, and X... i It is the proportion of the number of moles of a component gas to the total number of moles in the gas mixture. a, b, c, d, and e are the isobaric specific heat temperature coefficients for commonly used gases, which vary depending on the gas. The table below shows the isobaric specific heat temperature coefficients for commonly used gases:

[0081]

[0082]

[0083] The isobaric specific heat C of the gas mixture can be calculated using the above formula and parameters. P The value of is then determined according to the formula: C P -C V =R, calculate the specific heat at constant volume C VThe value of , where R is the gas constant, R = 8.134 [J / (molK)].

[0084] In conjunction with the above embodiments, in some embodiments, the total area of ​​the explosion-proof valve is obtained based on the preset opening pressure of the explosion-proof valve and the critical pressure of the critical flow rate of the mixed gas, including:

[0085] If the preset opening pressure of the explosion-proof valve is greater than the critical pressure of the critical flow rate of the mixed gas, the total area of ​​the explosion-proof valve can be obtained by the following formula:

[0086]

[0087] Where A is the total area of ​​the explosion-proof valve, W is the gas generation rate under battery thermal runaway conditions, C is the specific heat coefficient, and K... d Where P1 is the discharge coefficient, K is the preset opening pressure of the explosion-proof valve, and K is the pressure at which the valve is opened. b is the back pressure correction factor, Kc is the combination correction factor, T is the discharge temperature of the gas mixture, Z is the compressibility factor of the gas mixture, and M is the average molecular weight of the gas mixture.

[0088] In conjunction with the above embodiments, in some embodiments, the total area of ​​the explosion-proof valve is obtained based on the preset opening pressure of the explosion-proof valve and the critical pressure of the critical flow rate of the mixed gas, including:

[0089] If the preset opening pressure of the explosion-proof valve is less than the critical pressure of the critical flow velocity of the mixed gas, the total area of ​​the explosion-proof valve can be obtained by the following formula:

[0090]

[0091] K = C P / C V ;

[0092] r = P6 / P1;

[0093] Where A is the total area of ​​the explosion-proof valve, W is the gas generation rate under battery thermal runaway conditions, F2 is the flow coefficient of the mixed gas below the critical flow rate, and K... d K is the discharge coefficient. c The combined correction factor is given by: T being the venting temperature of the gas mixture, Z being the compressibility coefficient of the gas mixture, M being the average molecular weight of the gas mixture, P1 being the preset opening pressure of the explosion-proof valve, P6 being the back pressure of the explosion-proof valve, and C being the average molecular weight of the gas mixture. P C is the specific heat at constant pressure of the gas mixture. V This is the specific heat at constant volume of the gas mixture.

[0094] In conjunction with the above embodiments, in some embodiments, based on the total area of ​​the explosion-proof valve, it is verified whether the opening pressure of the explosion-proof valve under different structural types, positions, and quantities meets the preset opening pressure requirements, including:

[0095] Obtain the tensile stress-strain curve and failure strain of the explosion-proof valve material.

[0096] The battery is modeled based on the total area of ​​the explosion-proof valve, and the explosion-proof valve is preset in different structural types, locations and quantities to obtain the finite element model of the battery.

[0097] Based on the finite element model of the battery under different structural types, locations, and quantities of explosion-proof valves, as well as the tensile stress-strain curves and failure strains of the explosion-proof valve material, it is verified whether the opening pressure of the explosion-proof valve under different structural types, locations, and quantities meets the preset opening pressure requirements.

[0098] Understandably, after calculating the total area of ​​the explosion-proof valve, a finite element simulation model of the battery needs to be built. Building this model requires calibrating two key parameters: the tensile stress-strain curve of the explosion-proof valve material and its failure strain. Both can be obtained through tensile testing of the explosion-proof valve sample. After obtaining these parameters, the finite element simulation model of the battery is built based on the total area of ​​the explosion-proof valve. During model building, the structural type of the explosion-proof valve, the placement of the explosion-proof valve considering the discharge channel within the module, and the number of explosion-proof valves are preliminarily determined. The stress-strain curve and failure strain of the explosion-proof valve obtained from the tests are input into the model. The model outputs the simulated opening pressure of the battery explosion-proof valve under this design, and this simulated opening pressure is compared with the preset opening pressure of the explosion-proof valve to verify whether it meets the preset opening pressure requirements.

[0099] Please see Figure 2 In conjunction with the above embodiments, in some embodiments, obtaining the tensile stress-strain curve and failure strain of the explosion-proof valve material includes:

[0100] Obtain a sample 10 of the explosion-proof valve, calibrate the two ends of the sample 10 as clamping parts 12, and pull the clamping parts 12 to both sides along the length direction X of the sample 10 to perform a tensile test on the test part 11 of the sample 10 and obtain the tensile displacement curve of the sample 10.

[0101] Based on the tensile displacement curve of sample 10, the tensile stress-strain curve and failure strain of the explosion-proof valve material are obtained.

[0102] Understandably, tensile testing is a common material performance testing method used to evaluate the performance of materials under tensile loading. In a tensile test, two clamps are used to hold the sample 10 at both ends of the sample 10, applying a tensile force along the length X direction, causing the test section 11 of the sample 10 to be stretched and deformed. The tensile test obtains tensile-displacement curve information by recording the changes in tensile force and displacement on the test section 11. Based on the tensile-displacement curve information, the tensile stress-strain curve information of the test section 11 is obtained. The tensile stress can be calculated from the ratio of tensile force to the cross-sectional area, while the tensile strain can be calculated from the ratio of displacement to the initial size. By plotting the relationship between tensile stress (tensile force divided by cross-sectional area) and tensile strain (displacement divided by initial size), the tensile stress-strain curve information can be obtained. The failure strain of the explosion-proof valve material is the strain corresponding to the maximum tensile displacement and fracture of the test section 11.

[0103] In conjunction with the above embodiments, in some embodiments, obtaining the tensile stress-strain curve and failure strain of the explosion-proof valve material includes:

[0104] The tensile stress-strain curve and failure strain of the explosion-proof valve material are obtained using the following formulas:

[0105] ε=ΔL / L0;

[0106] S = (h * t * L0) / (ΔL + L0);

[0107] σ = F / S;

[0108] Where ε is the tensile strain of test part 11, ΔL is the tensile displacement of test part 11, L0 is the initial length of test part 11 before tension, S is the total cross-sectional area of ​​test part 11 during the tensioning process, h is the width of test part 11, t is the initial thickness of test part 11, σ is the tensile stress of test part 11, and F is the tensile force of test part 11 during the test. When test part 11 breaks, ΔL reaches its maximum value. max Failure strain ε of explosion-proof valve material max =ΔL max / L0.

[0109] In conjunction with the above embodiments, in some embodiments, based on the finite element model of the battery under different structural types, positions, and quantities of explosion-proof valves, as well as the tensile stress-strain curves and failure strains of the explosion-proof valve material, it is verified whether the opening pressure of the explosion-proof valves under different structural types, positions, and quantities meets the preset opening pressure requirements, including:

[0110] When building the finite element model of a battery, the structural type, location, and quantity of explosion-proof valves can be preset based on experience and relevant parameters, thus facilitating the construction of the battery's finite element model. Then, based on the battery's finite element model, the simulated opening pressure P2 of the explosion-proof valves under different structural types, locations, and quantities can be obtained. The preset opening pressure P1 and the simulated opening pressure P2 of the explosion-proof valves can then be calculated. If the following conditions are met:

[0111]

[0112] The pre-designed explosion-proof valves meet the battery usage requirements in terms of structure, location, and quantity.

[0113] If the following conditions are met:

[0114]

[0115] If the preset explosion-proof valve does not meet the battery's usage requirements in terms of structure, location, or quantity, the opening pressure of the explosion-proof valve needs to be preset again, and the total area of ​​the explosion-proof valve under the preset opening pressure needs to be recalculated until a new simulated opening pressure of the explosion-proof valve is obtained. The new simulated opening pressure of the explosion-proof valve needs to be recalculated until the usage requirements are met before the design is frozen.

[0116] Based on the above description, an example of the design verification of a battery explosion-proof valve is provided:

[0117] The maximum gas production pressure during the battery's normal operating lifespan is 0.4 MPa, and the minimum pressure under thermal runaway conditions is 0.8 MPa. Therefore, it is necessary to ensure that the valve opens promptly either before or during thermal runaway, and remains open during normal operation throughout the battery's lifespan. Considering the manufacturing tolerances of the explosion-proof valve, the preset opening pressure is set at 0.6 MPa. The gas production rate and composition under thermal runaway conditions were tested. The gas production rate was 2.5 L / s. Based on the gas composition, the constant-volume specific heat CV = 1.417 KJ / Kg.K and the constant-pressure specific heat CP = 1.913 KJ / Kg.K of the mixed gas, with a gas density of 1.29 kg / m³. 3 Based on the above formula, the critical pressure for the critical flow velocity of the mixed gas is calculated to be 0.188 MPa. Since the preset opening pressure of the explosion-proof valve is 0.6 MPa, which is greater than the critical pressure for the critical flow velocity of the mixed gas, the subsequent calculation of the required valve opening area is performed using the following formula:

[0118]

[0119] The total area of ​​the explosion-proof valve was calculated to be 477 mm². Then, a tensile test was performed on sample 10 of the explosion-proof valve material to create the tensile stress-strain curve and failure strain (e.g., ...). Figure 3As shown in the figure, its failure strain is 0.35. Based on the total area of ​​the explosion-proof valve, the tensile stress-strain curve and failure strain of the explosion-proof valve material, a finite element model of the battery is built. When building the finite element model, the preset structural form, position and quantity of the explosion-proof valve are input. The finite element model of the battery outputs the simulated valve opening pressure corresponding to the failure strain of the explosion-proof valve, which is 0.62 MPa. Through calculation:

[0120]

[0121] If the opening pressure of the explosion-proof valve under this design meets the requirements, the design is frozen.

[0122] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0123] The battery explosion-proof valve verification method provided in the embodiments of this application has been described in detail above, and specific examples have been used to illustrate the principle and implementation of this application. The description of the above embodiments is only for the purpose of helping to understand the technical solution and core idea of ​​this application. Those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and 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.

Claims

1. A method of verifying a battery explosion relief valve, the method comprising: The method comprises the following steps: acquiring the gas production rate and gas production composition under the battery thermal runaway state; acquiring the constant volume specific heat and constant pressure specific heat of the mixed gas based on the gas production rate and gas production composition under the battery thermal runaway state; acquiring the critical pressure of the critical flow rate of the mixed gas based on the constant volume specific heat and constant pressure specific heat of the mixed gas; acquiring the total area of the explosion-proof valve based on the preset opening pressure of the explosion-proof valve and the critical pressure of the critical flow rate of the mixed gas; verifying whether the opening pressure of the explosion-proof valve under different structural types, positions and quantities meets the requirement of the preset opening pressure based on the total area of the explosion-proof valve.

2. The method of claim 1, wherein, The method for acquiring the total area of the explosion-proof valve based on the preset opening pressure of the explosion-proof valve and the gas production rate and gas production composition under the battery thermal runaway state comprises the following steps: acquiring the pressure P3 generated by the maximum gas production in the whole life cycle of the battery in the normal use process and the minimum pressure P4 under the battery thermal runaway state, and acquiring the preset opening pressure P1 of the explosion-proof valve, which satisfies: P3 < P1 ≤ P4.

3. The method of claim 1, wherein the method further comprises: The method for acquiring the critical pressure of the critical flow rate of the mixed gas based on the constant volume specific heat and constant pressure specific heat of the mixed gas comprises the following steps: acquiring the critical pressure of the critical flow rate of the mixed gas through the following formula: K = C P / C V ; ； wherein, P Critical is the ambient pressure, is the critical pressure of the mixed gas, C P is the specific heat at constant pressure of the mixed gas, C V is the specific heat at constant volume of the mixed gas.

4. The method of claim 1, wherein, The method for acquiring the total area of the explosion-proof valve based on the preset opening pressure of the explosion-proof valve and the critical pressure of the critical flow rate of the mixed gas comprises the following steps: if the preset opening pressure of the explosion-proof valve is greater than the critical pressure of the critical flow rate of the mixed gas, the total area of the explosion-proof valve is acquired through the following formula: ； wherein A is the total area of the explosion-proof valve, W is the gas production rate under the thermal runaway state of the battery, C is a specific heat ratio coefficient, K d is a discharge coefficient, P1 is a preset opening pressure of the explosion-proof valve, K b is a back pressure correction coefficient, Kc is a combination correction coefficient, T is the discharge temperature of the mixed gas, Z is the compressibility coefficient of the mixed gas, and M is the average molecular weight of the mixed gas.

5. The method of claim 1, wherein, The method for acquiring the total area of the explosion-proof valve based on the preset opening pressure of the explosion-proof valve and the critical pressure of the critical flow rate of the mixed gas comprises the following steps: if the preset opening pressure of the explosion-proof valve is less than the critical pressure of the critical flow rate of the mixed gas, the total area of the explosion-proof valve is acquired through the following formula: ； ； K = C P / C V ; r = P6 / P1; Wherein A is the total area of the explosion-proof valve, W is the gas production rate of the battery in the thermal runaway state, F2 is the flow coefficient of the mixed gas below the critical flow rate, K d is the discharge coefficient, K c is the combined correction coefficient, T is the discharge temperature of the mixed gas, Z is the compressibility coefficient of the mixed gas, M is the average molecular weight of the mixed gas, P1 is the preset opening pressure of the explosion-proof valve, P6 is the back pressure of the explosion-proof valve, C P is the specific heat at constant pressure of the mixed gas, C V is the specific heat at constant volume of the mixed gas.

6. The method of claim 1, wherein, The method for verifying whether the opening pressure of the explosion-proof valve under different structural types, positions and quantities meets the requirement of the preset opening pressure based on the total area of the explosion-proof valve comprises the following steps: acquiring the tensile stress-strain curve of the explosion-proof valve material and the failure strain of the explosion-proof valve material; modeling the battery based on the total area of the explosion-proof valve, and presetting the explosion-proof valve under different structural types, positions and quantities to acquire the finite element model of the battery; verifying whether the opening pressure of the explosion-proof valve under different structural types, positions and quantities meets the requirement of the preset opening pressure based on the finite element model of the battery under different structural types, positions and quantities of the explosion-proof valve, and the tensile stress-strain curve of the explosion-proof valve material and the failure strain of the explosion-proof valve material.

7. The method of claim 6, wherein the method further comprises: The method for acquiring the tensile stress-strain curve of the explosion-proof valve material and the failure strain of the explosion-proof valve material comprises the following steps: acquiring a sample of the explosion-proof valve, marking both ends of the sample as clamping parts, pulling the clamping parts to both sides along the length direction of the sample to perform tensile test on the test part of the sample, and acquiring the tensile displacement curve of the sample; Based on the tensile displacement curve of the sample, a tensile stress-strain curve of the explosion-proof valve material and a failure strain of the explosion-proof valve material are obtained.

8. The method of claim 7, wherein the method further comprises: The obtaining of the tensile stress-strain curve of the explosion-proof valve material and the failure strain of the explosion-proof valve material comprises: The tensile stress-strain curve of the explosion-proof valve material and the failure strain of the explosion-proof valve material are obtained by the following formula: ； ； ； wherein, is the tensile strain of the test section, is the tensile displacement of the test section, is the initial length of the test section before stretching, is the total cross-sectional area of the test section during stretching, h is the width of the test section, is the initial thickness of the test section, is the tensile stress of the test section, is the tensile force during testing of the test section; When the test portion breaks, reaches a maximum max , the failure strain of the explosion valve material = max / .

9. The method of claim 6, wherein the method further comprises: Based on the finite element model of the battery under different structural types, positions and quantities of the explosion-proof valve, and the tensile stress-strain curve of the explosion-proof valve material and the failure strain of the explosion-proof valve material, whether the opening valve pressure of the explosion-proof valve under different structural types, positions and quantities meets the requirement of the preset opening valve pressure is verified, comprising: The simulation opening valve pressure P2 of the explosion-proof valve under different structural types, positions and quantities is obtained, and the preset opening valve pressure P1 of the explosion-proof valve and the simulation opening valve pressure P2 of the explosion-proof valve are calculated. If it meets: ， The preset explosion-proof valve in structural type, position and quantity meets the use requirement of the battery; If it meets: ， The preset explosion-proof valve in structural type, position and quantity does not meet the use requirement of the battery, and needs to be reset.

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