Battery explosion-proof valve verification method

Abstract

The invention discloses a battery explosion-proof valve verification method, and belongs to the technical field of batteries, and the battery explosion-proof valve verification method comprises the following steps: obtaining a gas production rate and gas production components of a battery in a thermal runaway state; the valve opening pressure of the anti-explosion valve is preset, the total area of the anti-explosion valve is calculated according to the gas production rate and gas production components of the battery in the thermal runaway state, and then the preset structure type, position and number of the anti-explosion valve are verified on the basis of the total area of the anti-explosion valve. Whether the preset structural type, position and number of the anti-explosion valves meet the use requirements or not is verified, if the use requirements are met, the preset structural type, position and number of the anti-explosion valves can be directly adopted for production and machining of products, and if the use requirements are not met, the valve opening pressure of the anti-explosion valves can be preset again; and the re-preset structural types, positions and number of the anti-explosion valves are verified, and a sample does not need to be manufactured for testing, so that the development period of structural parts can be greatly shortened.

Description

Technical Field

[0001] The present application belongs to the field of battery technology, and in particular relates to a battery explosion-proof valve calibration method. Background Art

[0002] The explosion-proof valve is a safety structure designed for battery safety considerations. The reasonable design of the explosion-proof valve can achieve instant discharge of heat from the battery when thermal runaway occurs, preventing a large amount of gas and heat from accumulating inside the battery and causing serious explosion and fire accidents. The method for determining whether the structural type, position and number of explosion-proof valves can meet the design indicators is based on the estimation of empirical values ​​combined with experimental verification. However, determining the structural type, position and number of explosion-proof valves by this method often greatly prolongs the development cycle of structural parts and increases development costs. Summary of the invention

[0003] Purpose of the invention: The embodiment of the present application provides a battery explosion-proof valve calibration method, which aims to overcome the technical problem that determining the structural type, position and quantity of the explosion-proof valve will greatly prolong the development cycle of the structural parts.

[0004] Technical solution: A battery explosion-proof valve calibration method described in an embodiment of the present application includes:

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

[0006] Based on a preset valve opening pressure of the explosion-proof valve, and a gas generation rate and a gas generation component in a thermal runaway state of the battery, obtaining a total area of ​​the explosion-proof valve;

[0007] Based on the total area of ​​the explosion-proof valves, it is verified whether the valve opening pressures of the explosion-proof valves in different structural types, positions and quantities meet the requirements of the preset valve opening pressures.

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

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

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

[0011] Based on the gas production rate and gas production composition of the battery in the thermal runaway state, obtaining the constant volume specific heat and constant pressure specific heat of the mixed gas;

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

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

[0014] In some embodiments, obtaining 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 includes:

[0015] The critical pressure of the critical flow rate of the mixed gas is obtained by the following formula:

[0016] K=C P / C V ;

[0017]

[0018] Among them, P Critical is the ambient pressure, P5 is the critical pressure of the critical velocity of the mixed gas, C P is the constant pressure specific heat of the mixed gas, C V is the specific heat at constant volume of the mixed gas.

[0019] In some embodiments, the step of obtaining the total area of ​​the explosion-proof valve based on the preset valve 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 valve 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 obtained by the following formula:

[0021]

[0022] 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, C is the specific heat ratio coefficient, K d is the discharge coefficient, P1 is the preset valve opening pressure of the explosion-proof valve, K b is the back pressure correction coefficient, Kc is the combination correction coefficient, T is the discharge temperature of the mixed gas, Z is the compression coefficient of the mixed gas, and M is the average molecular weight of the mixed gas.

[0023] In some embodiments, the step of obtaining the total area of ​​the explosion-proof valve based on the preset valve 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 valve 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 obtained by the following formula:

[0025]

[0026] K=C P / C V ;

[0027] r = P6 / P1;

[0028] 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 constant pressure specific heat of the mixed gas, C V is the specific heat at constant volume of the mixed gas.

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

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

[0031] Modeling the battery based on the total area of ​​the explosion-proof valve, and presetting the explosion-proof valve in different structural types, positions, and quantities to obtain a finite element model of the battery;

[0032] Based on the finite element model of the battery with the explosion-proof valve in different structural types, positions and quantities, 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 valve opening pressure of the explosion-proof valve in different structural types, positions and quantities meets the requirement of the preset valve 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 two ends of the sample as clamping parts, pull the clamping parts toward both sides along the length direction of the sample to perform a tensile test on the sample, and obtain a tensile force-displacement curve of the sample;

[0035] Based on the tensile force-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 of the explosion-proof valve material and the failure strain of the explosion-proof valve material are obtained by the following formula:

[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 stretching, 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;

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

[0043] In some embodiments, based on the finite element model of the battery with 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, verifying whether the valve opening pressure of the explosion-proof valve with different structural types, positions, and quantities meets the requirement of the preset valve opening pressure includes:

[0044] The simulated valve opening pressure P2 of the explosion-proof valve under different structural types, positions and quantities is obtained, and the preset valve opening pressure P1 of the explosion-proof valve and the simulated valve opening pressure P2 of the explosion-proof valve are calculated. If:

[0045]

[0046] The preset explosion-proof valve meets the use requirements of the battery in terms of structure, position and quantity;

[0047] If satisfied:

[0048]

[0049] The preset explosion-proof valve does not meet the usage requirements of the battery in terms of structure, position and quantity, and needs to be reset.

[0050] Beneficial effect: The battery explosion-proof valve verification method of the embodiment of the present application includes: obtaining the gas production rate and gas production composition in the thermal runaway state of the battery; obtaining the total area of ​​the explosion-proof valve based on the preset valve opening pressure of the explosion-proof valve, and the gas production rate and gas production composition in the thermal runaway state of the battery; based on the total area of ​​the explosion-proof valve, verifying whether the valve opening pressure of the explosion-proof valves in different structural types, positions and quantities meets the requirements of the preset valve opening pressure. 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 production rate and gas composition under the thermal runaway state of the battery. Then, based on the total area of ​​the explosion-proof valve, the structural type, position and quantity of the preset explosion-proof valve are verified to verify whether the structural type, position and quantity of the preset explosion-proof valve meet the use requirements. If the use requirements are met, the structural type, position and quantity of the preset explosion-proof valve can be directly used for product production and processing. If the use requirements are not met, the opening pressure of the explosion-proof valve can be reset, and the structural type, position and quantity of the reset explosion-proof valve can be verified. There is no need to make samples for testing, which can greatly shorten the development cycle of structural parts and reduce development costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0052] Figure 1 A schematic diagram of a flow chart of a battery explosion-proof valve calibration method provided in an embodiment of the present application;

[0053] Figure 2 A schematic diagram of the structure of a sample provided in an embodiment of the present application;

[0054] Figure 3 A tensile stress-strain curve diagram of the explosion-proof valve material provided in an embodiment of the present application;

[0055] Reference numerals: 10 - sample; 11 - testing portion; 12 - clamping portion; X - length direction. DETAILED DESCRIPTION

[0056] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0057] In the description of the present application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more features. In the description of the present application, "plurality" means two or more, and at least one means one, two or more, unless otherwise clearly and specifically defined.

[0058] The explosion-proof valve is a safety structure designed for battery safety considerations. Through the reasonable design of the explosion-proof valve, the heat can be instantly discharged from the battery when thermal runaway occurs, preventing a large amount of gas and heat from accumulating inside the battery and causing serious explosion and fire accidents. The design of the explosion-proof valve needs to meet two important indicators. One is that the valve is not opened during normal use of the battery, and the other is that the valve is opened in time and the gas is quickly released when thermal runaway occurs. By setting appropriate explosion-proof valve structural type, position, number, area and other parameters, the designed explosion-proof valve can meet the above two important indicators.

[0059] At present, the method for judging whether the selection, position, quantity and area of ​​different explosion-proof valves can meet the design indicators of explosion-proof valves is as follows: based on the summary of a large amount of measured data, the relationship between the explosion-proof valve structure type and the valve opening pressure and the discharge capacity under different explosion-proof valve area designs are summarized, and the explosion-proof valve structure type and area are preliminarily designed according to experience summary. After the sample is manufactured, a pressure test is performed to verify whether the initial design meets the use requirements. However, using this method makes it necessary to wait for the sample to be manufactured before conducting experimental tests after the design is frozen, and the original design plan is continuously adjusted according to the test results. The direction of adjustment can only be judged by experience. There are cases where repeated tests cannot meet the use requirements, the cost is high, and the development cycle is very long.

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

[0061] See also Figure 1 In an embodiment of the present application, the battery explosion-proof valve verification method includes:

[0062] S101: Obtaining the gas generation rate and gas generation composition in a battery thermal runaway state;

[0063] S102: Obtaining the total area of ​​the explosion-proof valve based on the preset valve opening pressure of the explosion-proof valve, and the gas production rate and gas production composition in the thermal runaway state of the battery;

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

[0065] It is understandable that when designing the structural type, position and number of explosion-proof valves on the battery, the gas production rate and gas composition under the thermal runaway state of the battery can be obtained based on the measurement of tests and 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 production rate and gas composition under the thermal runaway state of the battery. The total area of ​​the explosion-proof valve calculated at this time is the area required to meet the preset opening pressure of the explosion-proof valve. Then, the structure type, position and quantity of the explosion-proof valve are preset according to experience and other design parameters. Based on the calculated total area of ​​the explosion-proof valve, the structure type, position and quantity of the preset explosion-proof valve are verified to verify whether the structure type, position and quantity of the preset 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 opening pressure of the explosion-proof valve can be reset, and the new total area of ​​the explosion-proof valve is obtained by calculation, and then the structure type, position and quantity of the reset explosion-proof valve are verified. Through this method, it is not necessary to make a battery sample with a preset explosion-proof valve, which can reduce the development cost of the battery. Since there is no need to make samples to test the designed explosion-proof valve, the method can quickly verify the preset explosion-proof valves of different structure types, positions and quantities, and verify whether the preset explosion-proof valves of different structure types, positions and quantities meet the use requirements. It is not necessary to make physical products according to the design form of each preset explosion-proof valve (the design form includes the structure type, position and quantity), which can greatly shorten the development cycle of the structural parts.

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

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

[0068] Based on the gas production rate and gas composition under the thermal runaway state of the battery, the constant volume specific heat and constant pressure specific heat of the mixed gas are obtained.

[0069] 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.

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

[0071] It is understandable that after experimentally measuring and calculating the gas production rate and gas production composition under the thermal runaway state of the battery, the constant volume specific heat and constant pressure specific heat of the mixed gas can be calculated based on the gas production rate and gas production composition. Then, based on the constant volume specific heat and constant pressure specific heat of the mixed gas, as well as other more conventional parameter information, the critical pressure of the critical flow rate of the mixed gas can be calculated. At this time, it is necessary to compare the critical pressure of the critical flow rate of the mixed gas with the preset valve opening pressure of the explosion-proof valve, and according to the comparison results, use different calculation methods to calculate the total area of ​​the explosion-proof valve.

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

[0073] The critical pressure of the critical flow rate of the mixed gas is obtained by the following formula:

[0074] K=C P / C V ;

[0075]

[0076] Among them, P Critical is the ambient pressure, P5 is the critical pressure of the critical velocity of the mixed gas, C P is the constant pressure specific heat of the mixed gas, C V is the specific heat at constant volume of the mixed gas.

[0077] Among them, for the constant volume specific heat C of the mixed gas V and constant pressure specific heat 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, X i It is the ratio of the number of moles of gas components to the total number of moles of mixed gas. a, b, c, d, e are the constant pressure specific heat temperature coefficients of common gases, which vary from gas to gas. The following table is a table of constant pressure specific heat temperature coefficients of common gases:

[0081]

[0082]

[0083] The constant pressure specific heat C of the mixed gas can be calculated based on the above formula and parameters. P The value of C is then calculated according to the formula: P -C V =R, calculate the constant volume specific heat C VThe value of, where R is the gas constant, R = 8.134 [J / (moLK)].

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

[0086]

[0087] Where A is the total area of ​​the explosion-proof valve, W is the gas production rate under thermal runaway of the battery, C is the specific heat ratio coefficient, K is d is the discharge coefficient, P1 is the preset opening pressure of the explosion-proof valve, K b is the back pressure correction factor, Kc is the combined correction factor, T is the discharge temperature of the mixed gas, Z is the compression coefficient of the mixed gas, and M is the average molecular weight of the mixed gas.

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

[0089] 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 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 production rate under thermal runaway of the battery, 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 compression 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 constant pressure specific heat of the mixed gas, C V is the specific heat at constant volume of the mixed gas.

[0094] In combination with the above embodiments, in some embodiments, based on the total area of ​​the explosion-proof valve, checking whether the valve opening pressure of the explosion-proof valves in different structural types, positions, and quantities meets the requirements of the preset valve opening pressure includes:

[0095] Obtain the tensile stress-strain curve of the explosion-proof valve material and the 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, positions, and quantities to obtain a finite element model of the battery.

[0097] Based on the finite element model of the battery with explosion-proof valves in different structural types, positions and quantities, 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 valve opening pressure of the explosion-proof valves in different structural types, positions and quantities meets the preset valve opening pressure requirements.

[0098] It is understandable that after calculating the total area of ​​the explosion-proof valve, it is necessary to build a finite element simulation model of the battery. Building a finite element simulation model of the battery requires calibration of two key parameters, one is the tensile stress-strain curve of the explosion-proof valve material, and the other is the failure strain of the explosion-proof valve material. Both can be obtained by tensile testing the explosion-proof valve sample. After obtaining these two key parameters, a finite element simulation model of the battery is built according to the total area of ​​the explosion-proof valve. In the process of model building, the structural type of the explosion-proof valve, the location of the explosion-proof valve arrangement in the discharge channel of the module, and the number of explosion-proof valve arrangements are preliminarily determined. The stress-strain curve of the explosion-proof valve obtained by the test and the failure strain of the explosion-proof valve are input into the model, and the simulated valve opening pressure of the battery explosion-proof valve under the design is output through the model, and the simulated valve opening pressure of the battery explosion-proof valve under the design is compared with the preset valve opening pressure of the explosion-proof valve to verify whether the preset valve opening pressure of the explosion-proof valve is met.

[0099] See also Figure 2 In combination with the above embodiments, 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:

[0100] Obtain a sample 10 of the explosion-proof valve, calibrate the two ends of the sample 10 as clamping parts 12, 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 tension displacement curve of the sample 10.

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

[0102] It is understandable that tensile testing is a common material performance testing method used to evaluate the performance of materials under tensile loading. In the tensile test, two clamps can be clamped on the two clamping parts 12 at both ends of the sample 10, and tensile force can be applied to the sample 10 along the length direction X, so that the test part 11 of the sample 10 is stretched and deformed. The tensile test can obtain the tensile force displacement curve information by recording the changes in the tensile force and displacement of the test part 11. Based on the tensile force displacement curve information, the tensile stress strain curve information of the test part 11 is obtained. The tensile stress can be obtained by the ratio of the tensile force to the force-bearing cross-sectional area, and the tensile strain can be obtained by the ratio of the displacement to the initial size. By plotting the relationship between the tensile stress (tensile force divided by the force-bearing cross-sectional area) and the tensile strain (displacement divided by the initial size), the tensile stress strain curve information can be obtained. Among them, the failure strain of the explosion-proof valve material is the strain corresponding to the maximum fracture of the tensile displacement of the test part 11.

[0103] In combination with the above embodiments, 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:

[0104] 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:

[0105] ε=ΔL / L0;

[0106] S = (h*t*L0) / (ΔL+L0);

[0107] σ=F / S;

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

[0109] In combination with the above embodiments, in some embodiments, based on the finite element model of the battery with explosion-proof valves in different structural types, positions, and quantities, 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 valve opening pressure of the explosion-proof valves in different structural types, positions, and quantities meets the requirements of the preset valve opening pressure, including:

[0110] When building a finite element model of a battery, the structural type, position and quantity of the explosion-proof valve can be preset based on experience and relevant parameters, so as to facilitate the construction of the finite element model of the battery. Then, the simulated valve opening pressure P2 of the explosion-proof valve under different structural types, positions and quantities is obtained according to the finite element model of the battery, and the preset valve opening pressure P1 of the explosion-proof valve and the simulated valve opening pressure P2 of the explosion-proof valve are calculated. If:

[0111]

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

[0113] If satisfied:

[0114]

[0115] If the preset explosion-proof valve does not meet the battery usage requirements in terms of structure, position and quantity, it is necessary to reset the opening pressure of the explosion-proof valve and recalculate the total area of ​​the explosion-proof valve under the preset opening pressure until the new simulated opening pressure of the explosion-proof valve is obtained. The new simulated opening pressure of the explosion-proof valve is recalculated and the design is frozen until the usage requirements are met.

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

[0117] During normal use of the battery, the pressure generated by the maximum gas production during the entire life cycle is 0.4MPa, and the minimum pressure in the battery thermal runaway state is 0.8MPa. It is necessary to ensure that the battery can open the valve in time when or before thermal runaway occurs, and the valve is not opened during normal operation of the entire life cycle. Considering that there are certain tolerances in the manufacturing process of the explosion-proof valve, the preset valve opening pressure of the explosion-proof valve is determined to be 0.6Mpa. The gas production rate and gas production composition in the thermal runaway state of the battery were tested. The gas production rate was 2.5L / S, and the constant volume specific heat of the mixed gas CV=1.417KJ / Kg.k and the constant pressure specific heat CP=1.913KJ / Kg.k were calculated based on the gas production composition. The gas density is 1.29kg / m 3 According to the above formula, the critical pressure of the critical flow rate of the mixed gas is calculated to be 0.188MPa. Since the preset valve opening pressure of the explosion-proof valve is 0.6MPa, which is greater than the critical pressure of the critical flow rate of the mixed gas, the subsequent required valve opening area calculation is calculated using the following formula:

[0118]

[0119] The total area of ​​the explosion-proof valve is calculated to be 477 mm2. Then, the sample 10 of the explosion-proof valve material is subjected to a tensile test to produce a tensile stress-strain curve and a failure strain (such as Figure 3As shown), it can be known that its failure strain is 0.35. Based on the total area of ​​the explosion-proof valve, the material tensile stress-strain curve and failure strain of the explosion-proof valve, a finite element model of the battery is built. When building the finite element model, the structure, position and number of the preset explosion-proof valve are input. The finite element model output of the battery makes the explosion-proof valve strain reach the failure strain corresponding to the simulated valve opening pressure of 0.62Mpa. By calculation:

[0120]

[0121] Then the explosion-proof valve opening pressure under this design meets the requirements and the design is frozen.

[0122] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0123] The battery explosion-proof valve calibration method provided in the embodiments of the present application is introduced in detail above, and the principle and implementation mode of the present application are explained by applying specific examples. The description of the above embodiments is only used to help understand the technical solution and its core idea of ​​the present application; ordinary technicians in this field should understand that: it is still possible to modify the technical solutions recorded in the aforementioned embodiments, or to replace some of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A battery explosion-proof valve calibration method, characterized in that: include: Obtain the gas generation rate and gas composition under the thermal runaway state of the battery; Based on a preset valve opening pressure of the explosion-proof valve, and a gas generation rate and a gas generation component in a thermal runaway state of the battery, obtaining a total area of ​​the explosion-proof valve; Based on the total area of ​​the explosion-proof valves, it is verified whether the valve opening pressures of the explosion-proof valves in different structural types, positions and quantities meet the requirements of the preset valve opening pressures.

2. The battery explosion-proof valve verification method according to claim 1, characterized in that: The obtaining of the total area of ​​the explosion-proof valve based on the preset valve opening pressure of the explosion-proof valve, and the gas production rate and gas production composition in the thermal runaway state of the battery includes: The pressure P3 generated by the maximum gas production during the whole life cycle of the battery in normal use and the minimum pressure P4 of the battery in the thermal runaway state are obtained, and the preset valve opening pressure P1 of the explosion-proof valve is obtained, satisfying: P3<P1≤P4.

3. The battery explosion-proof valve verification method according to claim 1, characterized in that: The obtaining of the total area of ​​the explosion-proof valve based on the preset valve opening pressure of the explosion-proof valve, and the gas production rate and gas production composition in the thermal runaway state of the battery includes: Based on the gas production rate and gas production composition of the battery in the thermal runaway state, obtaining the constant volume specific heat and constant pressure specific heat of the mixed gas; Based on the constant volume specific heat and constant pressure specific heat of the mixed gas, a critical pressure of a critical flow rate of the mixed gas is obtained; Based on the preset valve opening pressure of the explosion-proof valve and the critical pressure of the critical flow rate of the mixed gas, the total area of ​​the explosion-proof valve is obtained.

4. The battery explosion-proof valve verification method according to claim 3, characterized in that: The step of obtaining 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 critical pressure of the critical flow rate of the mixed gas is obtained by the following formula: K=C P / C V ; Among them, P Critical is the ambient pressure, P5 is the critical pressure of the critical velocity of the mixed gas, C P is the constant pressure specific heat of the mixed gas, C V is the specific heat at constant volume of the mixed gas.

5. The battery explosion-proof valve verification method according to claim 3, characterized in that: The obtaining of the total area of ​​the explosion-proof valve based on the preset valve opening pressure of the explosion-proof valve and the critical pressure of the critical flow rate of the mixed gas comprises: If the preset valve 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 obtained by the following formula: 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, C is the specific heat ratio coefficient, K d is the discharge coefficient, P1 is the preset valve opening pressure of the explosion-proof valve, K b is the back pressure correction coefficient, Kc is the combination correction coefficient, T is the discharge temperature of the mixed gas, Z is the compression coefficient of the mixed gas, and M is the average molecular weight of the mixed gas.

6. The battery explosion-proof valve verification method according to claim 3, characterized in that: The obtaining of the total area of ​​the explosion-proof valve based on the preset valve opening pressure of the explosion-proof valve and the critical pressure of the critical flow rate of the mixed gas comprises: If the preset valve 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 obtained by 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 constant pressure specific heat of the mixed gas, C V is the specific heat at constant volume of the mixed gas.

7. The battery explosion-proof valve verification method according to claim 1, characterized in that: The checking, based on the total area of ​​the explosion-proof valve, whether the valve opening pressure of the explosion-proof valve under different structural types, positions, and quantities meets the requirement of the preset valve opening pressure includes: Obtaining a tensile stress-strain curve of the explosion-proof valve material and a 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 in different structural types, positions, and quantities to obtain a finite element model of the battery; Based on the finite element model of the battery with the explosion-proof valve in different structural types, positions and quantities, 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 valve opening pressure of the explosion-proof valve in different structural types, positions and quantities meets the requirement of the preset valve opening pressure.

8. The battery explosion-proof valve verification method according to claim 7, characterized in that: 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: Obtain a sample of the explosion-proof valve, mark the two ends of the sample as clamping parts, pull the clamping parts toward both sides along the length direction of the sample to perform a tensile test on the test part of the sample, and obtain a tensile force-displacement curve of the sample; Based on the tensile force-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.

9. The battery explosion-proof valve verification method according to claim 8, characterized in that: 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: ε=ΔL / L0; S = (h*t*L0) / (ΔL+L0); σ=F / S; 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 stretching, 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; When the test part breaks, ΔL reaches the maximum value ΔL max , the failure strain ε of the explosion-proof valve material max =ΔL max / L0.

10. The battery explosion-proof valve verification method according to claim 7, characterized in that: The finite element model of the battery with 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, verifying whether the valve opening pressure of the explosion-proof valve with different structural types, positions and quantities meets the requirement of the preset valve opening pressure, includes: The simulated valve opening pressure P2 of the explosion-proof valve under different structural types, positions and quantities is obtained, and the preset valve opening pressure P1 of the explosion-proof valve and the simulated valve opening pressure P2 of the explosion-proof valve are calculated. If: The preset explosion-proof valve meets the use requirements of the battery in terms of structure, position and quantity; If satisfied: The preset explosion-proof valve does not meet the usage requirements of the battery in terms of structure, position and quantity, and needs to be reset.

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