Method and system for determining opening pressure of battery cell safety valve

Abstract

The application provides a kind of electric core safety valve opening pressure determination method and system, belongs to battery technical field.Therein method includes determining the target normalized voltage when target gas first appears in electric core under target abuse condition;Target gas is double bond or multi bond reducing gas;Determine the internal gas pressure of electric core corresponding to target normalized voltage under target abuse condition, as the opening pressure of safety valve.The application is from thermal runaway chemical reaction mechanism, and the internal pressure at the moment when the key gas of accelerated thermal runaway is generated is taken as the design basis of opening pressure, to ensure that the safety valve is accurately opened before thermal runaway accelerates, and the sealing reliability and timely pressure relief are considered, which significantly improves the safety of electric core.

Description

Technical Field

[0001] This application belongs to the field of battery technology, and in particular relates to a method and system for determining the opening pressure of a battery cell safety valve. Background Technology

[0002] Lithium-ion batteries are typically composed of multiple cells. Under adverse conditions such as overcharging, over-discharging, overheating, long-term storage, high-current charging and discharging, and water molecules entering the battery, gas can be generated inside the cells. The most serious consequence is thermal runaway. Therefore, each cell needs to be designed with a safety valve. If the internal pressure of the cell becomes too high, the safety valve will open to release pressure and prevent an explosion.

[0003] Patent application No. 2019111122467 discloses a design method, system, safety valve, and battery for the opening pressure of a lithium battery safety valve. The design method includes measuring the in-situ pressure and temperature of the battery and fitting a temperature-pressure function. By taking the second derivative of the temperature-pressure function, the pressure value corresponding to the second derivative being 0 is calculated. Based on the pressure value corresponding to the second derivative being 0, the opening pressure value of the safety valve is obtained. The opening pressure value is the point where the second derivative of the temperature-pressure function is 0. The opening pressure value characterizes the transition point of the battery's internal pressure from the electrolyte evaporation and gas generation process to the electrolyte decomposition and gas generation process.

[0004] However, the aforementioned patent application only broadly distinguishes between two stages: "electrolyte evaporation and gas generation" and "electrolyte decomposition and gas generation." The electrolyte decomposition and gas generation stage produces various gases, including hydrogen, carbon monoxide, ethylene, and methane. Different reducing gases exhibit completely different reducing activities on the battery cathode material: hydrogen and methane only have a slight effect on the initial temperature (<3°C), while multi-bonded gases such as alkenes and alkynes advance the failure temperature of the cathode material by 55°C. The aforementioned patent application fails to consider that reducing gases containing double or multiple bonds, such as alkenes and alkynes, are key factors accelerating thermal runaway. It relies solely on two macroscopic parameters—pressure and temperature—without introducing gas composition analysis methods, thus failing to establish a causal relationship at the chemical mechanism level of "key gas appearance → accelerated thermal runaway." This makes the opening pressure determined in the aforementioned patent application potentially too late (opening only after the key gas has been generated) or too early (opening too early during the electrolyte evaporation stage, leading to leakage), making it difficult to achieve the design goal of "precise pressure relief before accelerated thermal runaway." Therefore, the "stage transition node" identified in the aforementioned patent application does not correspond to the critical moment when timely pressure relief is most needed. Summary of the Invention

[0005] This application provides a method and system for determining the opening pressure of a battery cell safety valve. Based on the mechanism of thermal runaway chemical reaction, the internal pressure of the battery cell when double or multi-bonded reducing gases appear is used as the design basis for the opening pressure of the safety valve. This achieves the technical effect of accurately releasing pressure before thermal runaway acceleration, significantly improving the safety and scientific design of lithium batteries.

[0006] In a first aspect, this application provides a method for determining the opening pressure of a battery cell safety valve, including: Step 101: Determine the target normalized voltage when the target gas first appears inside the cell under the target abuse conditions; wherein, the target gas is a double-bonded or multi-bonded reducing gas; Step 102: Determine the internal air pressure of the battery cell corresponding to the target normalized voltage under the target abuse condition, so as to serve as the opening pressure of the safety valve.

[0007] Optionally, determining the target normalized voltage at the first appearance of the target gas inside the battery cell under target abuse conditions includes: Under overcharge conditions, the curves of the actual voltage and internal gas composition of the battery cell over time are obtained and used as the first curve and the second curve, respectively. The time when the target gas first appears is obtained from the second curve, and the actual cell voltage at the same time is obtained on the first curve and used as the first voltage. Differentiating the first curve yields the first first derivative curve, which can be used as the third curve. The actual cell voltage in the first curve corresponding to the first time the first derivative is greater than the preset threshold is obtained from the third curve, and used as the second voltage. The target normalized voltage is determined based on the first voltage and the second voltage.

[0008] Optionally, determining the target normalized voltage based on the first voltage and the second voltage includes: The ratio of the first voltage to the second voltage is used as the target normalized voltage.

[0009] Optionally, determining the internal gas pressure of the battery cell corresponding to the target normalized voltage under the target abuse conditions, as the opening pressure of the safety valve, includes: The curves of the actual voltage and internal pressure of the battery cell changing over time under the condition of overcharging were obtained and used as the fourth and fifth curves, respectively. Differentiating the fourth curve yields the second first derivative curve, which serves as the sixth curve. The actual cell voltage in the fourth curve corresponding to the first time the first derivative of the sixth curve is obtained is used as the third voltage. The fourth voltage in the fourth curve is determined based on the target normalized voltage and the third voltage. The time corresponding to the fourth voltage is obtained from the fourth curve, and the internal pressure of the cell at the same time is obtained on the fifth curve, which is then used as the opening pressure of the safety valve.

[0010] Optionally, determining the fourth voltage in the fourth curve based on the target normalized voltage and the third voltage includes: The product of the target normalized voltage and the third voltage is determined as the fourth voltage in the fourth curve.

[0011] Optionally, the preset threshold is greater than or equal to 0.01V / s.

[0012] Optionally, the target gas includes ethylene, acetylene, or propylene.

[0013] Secondly, this application provides a battery cell safety valve opening pressure determination system, comprising: The first determining module is used to determine the target normalized voltage when the target gas first appears inside the battery cell under the target abuse conditions; wherein, the target gas is a double-bonded or multi-bonded reducing gas; The second determining module is used to determine the internal air pressure of the battery cell corresponding to the target normalized voltage under the target abuse condition, so as to serve as the opening pressure of the safety valve.

[0014] Thirdly, this application provides a computer device including a processor and a memory; wherein, when the processor executes a computer program stored in the memory, it implements the steps of the method for determining the opening pressure of the battery cell safety valve described in the first aspect.

[0015] Fourthly, this application provides a computer-readable storage medium, characterized in that it is used to store a computer program; when the computer program is executed by a processor, it implements the steps of the method for determining the opening pressure of the battery cell safety valve as described in the first aspect.

[0016] The method for determining the opening pressure of the battery cell safety valve described above has the following advantages: This application starts from the chemical reaction mechanism of thermal runaway, using the normalized voltage at which the target gas first appears inside the battery cell under the target abuse conditions as the target normalized voltage, and the internal gas pressure of the battery cell corresponding to this target normalized voltage as the opening pressure of the safety valve; wherein, the target gas is a double-bonded or multi-bonded reducing gas. Since double-bonded or multi-bonded reducing gases are key gases that accelerate thermal runaway, using the internal gas pressure at the time of their first appearance as the opening pressure can open the safety valve in time to release pressure before thermal runaway is about to accelerate, achieving precise intervention.

[0017] When determining the target normalized voltage, the actual cell voltage at the moment when the first derivative first exceeds a preset threshold is obtained by differentiating the curve of the actual cell voltage changing over time. The target normalized voltage is then determined by the ratio of the actual cell voltage at the moment the target gas first appears to this voltage, thus mapping the moment of target gas appearance to a unified normalized voltage reference. When determining the valve opening pressure, the internal gas pressure of the cell corresponding to the target normalized voltage is obtained through the same differentiation method. This decouples the gas composition experiment from the internal pressure experiment, allowing for accurate acquisition of the internal pressure value at the moment the target gas first appears without the need for simultaneous measurement of gas composition and internal pressure, reducing experimental difficulty. Simultaneously, using this pressure as the valve opening pressure ensures that it is higher than the pressure during the electrolyte evaporation stage, preventing premature opening and leakage, while being lower than the peak pressure during the violent thermal runaway stage, ensuring timely pressure relief and balancing sealing reliability and timely pressure relief. Furthermore, this application does not rely on empirical coefficients and is applicable to the design of safety valves for lithium battery cells in different systems. Attached Figure Description

[0018] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A flowchart illustrating a method for determining the opening pressure of a battery cell safety valve, provided in an embodiment of this application; Figure 2 This is a schematic diagram of a method for determining the opening pressure of a battery cell safety valve, provided in an embodiment of this application. Figure 3 A graph showing the relationship between cell voltage and time provided in an embodiment of this application; Figure 4 This is a graph showing the relationship between ethylene signal intensity and time, provided in an embodiment of this application. Figure 5 A graph showing the relationship between the internal pressure of the battery cell and time, provided for an embodiment of this application; Figure 6 A graph showing the relationship between the normalized voltage of the battery cell and time, provided in an embodiment of this application; Figure 7 This is a schematic diagram of a battery cell safety valve opening pressure determination system provided in an embodiment of this application. Detailed Implementation

[0020] 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 some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0021] Example 1 like Figure 1 and Figure 2 As shown, this embodiment provides a method for determining the opening pressure of a battery cell safety valve, including: Step 101: Determine the target normalized voltage when the target gas first appears inside the cell under the target abuse conditions; wherein, the target gas is a double-bonded or multi-bonded reducing gas.

[0022] In this step, the battery cell is subjected to abuse experiments (e.g., overcharging) to trigger thermal runaway; the gas composition generated inside the battery cell is detected in real time using an in-situ mass spectrometer, and the time point of the first appearance of each gas (component) is recorded; the change of battery cell voltage over time is monitored simultaneously to obtain the actual voltage-time curve of the battery cell; the target gas includes, but is not limited to, ethylene, acetylene or propylene.

[0023] High-resolution transmission electron microscopy / in-situ XRD results indicate that in the early stages of battery thermal runaway, the morphology and crystal deterioration of the positive electrode are caused by the attack of reducing gases migrating from the negative electrode side, mainly including hydrogen, carbon monoxide, ethylene, and methane. Different reducing gases exhibit completely different reduction activities on the cathode material: hydrogen and methane only have a slight effect on the onset temperature (<3℃), while compared to saturated reducing gases such as hydrogen and methane, multi-bonded gases such as alkenes and alkynes cause the cathode failure temperature to occur 55℃ earlier (relative to the cathode failure temperature without the presence of multi-bonded reducing gases such as alkenes and alkynes). Therefore, controlling double- or triple-bonded reducing gases such as alkenes and alkynes is key to suppressing and mitigating the thermal runaway reaction. Previous findings suggest that the safety valve opening is caused by the internal battery pressure rising above the safety valve opening pressure due to thermal runaway. This internal pressure rise is caused by electrolyte vapor and thermal runaway gas generation, with electrolyte vapor generation preceding double- or multi-bonded gases. Therefore, the internal pressure of the battery cell when double or multi-bonded gases are generated can serve as an important basis for the design of the safety valve opening pressure.

[0024] For example, such as Figure 3 and Figure 4 As shown, curves of the actual voltage and internal gas composition of the battery cell over time are obtained under overcharge conditions, and are used as the first curve and the second curve, respectively.

[0025] The time when the target gas first appears is obtained from the second curve, and the actual cell voltage at the same time is obtained on the first curve and used as the first voltage.

[0026] Differentiating the first curve yields the first first-order derivative curve, which can be used as the third curve.

[0027] The actual cell voltage on the first curve corresponding to the point on the third curve where the first derivative first exceeds a preset threshold (e.g., 0.01V / s, at which point the internal short circuit point of the cell intensifies) is obtained as the second voltage. That is, the actual cell voltage on the first curve corresponding to the point on the third curve where the first derivative exceeds the preset threshold is integrated.

[0028] The target normalized voltage is determined based on the first voltage and the second voltage; specifically, the ratio of the first voltage to the second voltage is used as the target normalized voltage.

[0029] Although the electrical performance parameters of the battery cells may differ in this step, the physical mechanism of the voltage abrupt change is the same (both are caused by gas-induced distortion of the electrode interface). Therefore, the tangent voltage at the abrupt change point (first derivative 0.01V / s) and the normalized voltage are introduced as two characteristic values ​​of the thermal runaway reaction process to eliminate the influence of cell inconsistencies. Specifically, 0.01V / s corresponds to the starting point of electrode interface distortion due to gas accumulation; the normalized voltage reflects the progress position of the target gas occurrence relative to the voltage abrupt change starting point, eliminating the absolute voltage deviation caused by manufacturing differences between different battery cells.

[0030] Step 102: Determine the internal air pressure of the battery cell corresponding to the target normalized voltage under the target abuse condition, so as to serve as the opening pressure of the safety valve.

[0031] For example, under the same overcharge conditions as in step 101, the curves showing the actual voltage and internal pressure of the battery cell changing over time are obtained, and used as the fourth and fifth curves, respectively. The curve showing the internal pressure changing over time is as follows: Figure 5 As shown.

[0032] Differentiating the fourth curve yields the second first derivative curve, which serves as the sixth curve.

[0033] The actual cell voltage in the fourth curve corresponding to the first time the first derivative of the cell exceeds a preset threshold (e.g., 0.01V / s, at which point the short circuit point inside the cell intensifies) is obtained from the sixth curve and used as the third voltage.

[0034] The fourth voltage in the fourth curve is determined based on the target normalized voltage and the third voltage. Further, the target normalized voltage U obtained in step 101 is... a The product of the voltage V3 obtained in step 102 and the voltage V4 obtained in step 102 is determined as the fourth voltage V4 in the fourth curve, that is: .

[0035] Where V1 is the first voltage and V2 is the second voltage.

[0036] The time corresponding to the fourth voltage is obtained from the fourth curve, and the internal pressure of the cell at the same time is obtained on the fifth curve, which is then used as the opening pressure of the safety valve.

[0037] In step 101, when the in-situ mass spectrometer detects the gas composition inside the cell, the internal pressure of the cell is not measured simultaneously. Therefore, in step 102, it is necessary to obtain the curves of the actual voltage and internal pressure of the cell changing over time. The internal pressure of the cell is measured by a pressure sensor.

[0038] Under the condition that the other electrical properties (capacity, AC internal resistance ACR, initial circuit voltage OCV) are basically the same in the same batch, the remaining minor differences are mainly concentrated in the self-discharge rate.

[0039] Selection logic for the tested battery cells: A cell with a very small K-value (a measure of the self-discharge rate of a lithium battery, representing the decrease in battery voltage per unit time) indicates stable internal chemical reactions and virtually no electronic conduction or micro-short circuit paths. These cells exhibit the slowest aging rate, the longest cycle life, and the strongest voltage retention capability after long-term storage.

[0040] A battery cell with a relatively large K-value (although still within the acceptable range) indicates that it has slightly more internal impurities or minor defects in the separator. Although the electrical performance is similar at the factory, these minor defects will be amplified after several hundred cycles, leading to accelerated capacity decay. In this embodiment, the standard for the tested battery cell is a K-value ≤ 1.5mV / day.

[0041] The fourth and fifth curves have the same horizontal axis, both representing time. Under the premise that the battery cells are basically the same and the overcharge and abuse conditions are the same, the time corresponding to the fourth voltage on the fourth curve, which is calculated from the target normalized voltage, can be regarded as the time when the target gas is generated (the time when thermal runaway will occur). Then, the internal pressure of the battery cell when thermal runaway will occur can be obtained from the fifth curve, which can be used as the valve opening pressure.

[0042] This embodiment takes the design of the safety valve opening pressure of a 52Ah lithium iron phosphate battery as an example.

[0043] like Figure 3 and Figure 4As shown, a thermal runaway experiment was conducted on a 52Ah lithium iron phosphate battery cell to obtain the relationship between the cell voltage and the intensity of various gas signals inside the cell as a function of time. It was found that ethylene appeared at 436.971s. At this time, the voltage on the first curve corresponding to the first point on the curve (the third curve) where the derivative of the cell voltage versus time curve is greater than 0.01 is 5.7291V. Using the second voltage (5.7291V), a normalized voltage was obtained. The first voltage (5.4935V) at the time of ethylene appearance inside the cell (436.971s) and the normalized voltage were then determined. (0.9588).

[0044] like Figure 5 and Figure 6 As shown, the correspondence between cell pressure and normalized voltage at the same time is obtained. Based on the correspondence between cell pressure and normalized voltage, the normalized voltage is found. The cell pressure corresponding to (0.9588) can be determined as the opening pressure of the safety valve of a 52Ah lithium iron phosphate battery.

[0045] In summary, this embodiment provides a method for determining the opening pressure of a battery cell safety valve. The internal pressure when a double- or multi-bonded reducing gas (such as ethylene) first appears is used as the opening pressure. This ensures that the safety valve opens to release pressure at the critical moment when thermal runaway is about to accelerate, rather than waiting until a large amount of less harmful gases such as hydrogen and methane are produced. This achieves precise intervention "earlier than thermal runaway acceleration" at the chemical mechanism level.

[0046] The design value is based on the actual internal pressure when the reducing gas with double or multiple bonds appears. This pressure is higher than the pressure during the electrolyte evaporation stage (to avoid premature opening and leakage) and significantly lower than the peak pressure during the violent thermal runaway stage (to ensure timely pressure relief). This achieves a scientific balance between sealing reliability and timely pressure relief.

[0047] By employing an indirect measurement method using normalized voltage, this invention solves the technical challenge of directly measuring the correlation between internal pressure and gas timing in valveless cells. Since valveless cells are internally sealed during thermal runaway experiments, directly measuring the correlation between gas composition and internal pressure is limited by equipment connection methods and experimental conditions. This embodiment links the gas composition experiment and pressure monitoring experiment using normalized voltage, enabling accurate acquisition of the internal pressure value at the first appearance of each gas without simultaneously monitoring the internal pressure during gas composition testing. This reduces experimental difficulty and equipment requirements.

[0048] This embodiment does not depend on specific cell systems (such as different cathode materials or different capacities). By simply following the steps to conduct experiments on the target cell, a targeted valve opening pressure design value can be obtained. This avoids the uncertainty of traditional empirical values ​​or simply applying safety factors, and is applicable to the safety valve design of various lithium batteries.

[0049] Example 2 Based on the same inventive concept as Embodiment 1, this embodiment also provides a battery cell safety valve opening pressure determination system. Since the principle of this system in solving the problem is similar to the aforementioned battery cell safety valve opening pressure determination method, the implementation of this system can refer to the implementation of the battery cell safety valve opening pressure determination method.

[0050] like Figure 7 As shown, the battery cell safety valve opening pressure determination system includes: The first determining module 10 is used to determine the target normalized voltage when the target gas first appears inside the battery cell under the target abuse condition; wherein the target gas is a double-bonded or multi-bonded reducing gas.

[0051] The second determining module 20 is used to determine the internal air pressure of the battery cell corresponding to the target normalized voltage under the target abuse condition, so as to serve as the opening pressure of the safety valve.

[0052] For more detailed information on the working process of each of the above modules, please refer to the relevant content disclosed in Example 1, which will not be repeated here.

[0053] Example 3 This embodiment provides a safety valve, the opening pressure of which is obtained by the method for determining the opening pressure of a battery cell safety valve as described in Embodiment 1.

[0054] For a more detailed explanation of the above method, please refer to the relevant content disclosed in Example 1, which will not be repeated here.

[0055] Example 4 This embodiment provides a battery including the safety valve as described in Embodiment 3.

[0056] For a more detailed explanation of the above method, please refer to the relevant content disclosed in Example 1, which will not be repeated here.

[0057] Example 5 This embodiment provides a computer device, including a processor and a memory; wherein, when the processor executes the computer program stored in the memory, it implements the steps of the method for determining the opening pressure of the battery cell safety valve as described in Embodiment 1.

[0058] For a more detailed explanation of the above method, please refer to the relevant content disclosed in Example 1, which will not be repeated here.

[0059] Example 6 This embodiment provides a computer-readable storage medium for storing a computer program; when the computer program is executed by a processor, it implements the steps of the method for determining the opening pressure of the battery cell safety valve as described in Embodiment 1.

[0060] For a more detailed explanation of the above method, please refer to the relevant content disclosed in Example 1, which will not be repeated here.

[0061] Example 7 This embodiment provides a computer program product, including computer-executable instructions or a computer program. When the computer-executable instructions or the computer program are executed by a processor, they implement the steps of the method for determining the opening pressure of the battery cell safety valve as described in Embodiment 1.

[0062] For a more detailed explanation of the above method, please refer to the relevant content disclosed in Example 1, which will not be repeated here.

[0063] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems, devices, storage media, and computer program products disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and relevant parts can be referred to the method section.

[0064] Those skilled in the art will clearly understand that the techniques in the embodiments of this application can be implemented using software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solutions in the embodiments of this application, or the parts that contribute to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments of this application or some parts of the embodiments.

[0065] In some embodiments, computer-executable instructions may take the form of programs, software, software modules, scripts, or code, written in any form of programming language (including compiled or interpreted languages, or declarative or procedural languages), and may be deployed in any form, including as stand-alone programs or as modules, components, subroutines, or other units suitable for use in a computing environment.

[0066] As an example, computer-executable instructions may, but do not necessarily, correspond to files in a file system. They may be stored as part of a file that holds other programs or data, for example, in one or more scripts in a Hyper Text Markup Language (HTML) document, in a single file dedicated to the program in question, or in multiple co-located files (e.g., files that store one or more modules, subroutines, or code sections).

[0067] As an example, computer-executable instructions can be deployed to execute on a single electronic device, or on multiple electronic devices located at one location, or on multiple electronic devices distributed across multiple locations and interconnected via a communication network.

[0068] The present application has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present application. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and implementation methods of the present application without departing from the spirit and scope of the present application, and all such modifications and improvements fall within the scope of the present application. The scope of protection of the present application is determined by the appended claims.

Claims

1. A method for determining the opening pressure of a battery cell safety valve, characterized in that, include: Step 101, determine the target normalized voltage when the target gas first appears inside the cell under the target abuse condition, including: Under overcharge conditions, the curves of the actual voltage and internal gas composition of the battery cell over time are obtained and used as the first curve and the second curve, respectively. The time when the target gas first appears is obtained from the second curve, and the actual cell voltage at the same time is obtained on the first curve and used as the first voltage. Differentiating the first curve yields the first first derivative curve, which can be used as the third curve. The actual cell voltage in the first curve corresponding to the first time the first derivative is greater than the preset threshold is obtained from the third curve, and used as the second voltage. The ratio of the first voltage to the second voltage is used as the target normalized voltage; wherein, the target gas is a reducing gas with double or multiple bonds; Step 102: Determine the internal air pressure of the battery cell corresponding to the target normalized voltage under the target abuse condition, so as to serve as the opening pressure of the safety valve.

2. The method for determining the opening pressure of the battery cell safety valve according to claim 1, characterized in that, The determination of the internal gas pressure of the battery cell corresponding to the target normalized voltage under the target abuse condition, as the opening pressure of the safety valve, includes: The curves of the actual voltage and internal pressure of the battery cell changing over time under the condition of overcharging were obtained and used as the fourth and fifth curves, respectively. Differentiating the fourth curve yields the second first derivative curve, which serves as the sixth curve. The actual cell voltage in the fourth curve corresponding to the first time the first derivative of the sixth curve is obtained is used as the third voltage. The fourth voltage in the fourth curve is determined based on the target normalized voltage and the third voltage. The time corresponding to the fourth voltage is obtained from the fourth curve, and the internal pressure of the cell at the same time is obtained on the fifth curve, which is then used as the opening pressure of the safety valve.

3. The method for determining the opening pressure of the battery cell safety valve according to claim 2, characterized in that, The step of determining the fourth voltage in the fourth curve based on the target normalized voltage and the third voltage includes: The product of the target normalized voltage and the third voltage is determined as the fourth voltage in the fourth curve.

4. The method for determining the opening pressure of the battery cell safety valve according to claim 1 or 2, characterized in that, The preset threshold is greater than or equal to 0.01V / s.

5. The method for determining the opening pressure of the battery cell safety valve according to any one of claims 1-3, characterized in that, The target gas includes ethylene, acetylene, or propylene.

6. A system for determining the opening pressure of a battery cell safety valve, characterized in that, include: The first determining module is used to determine the target normalized voltage when the target gas first appears inside the battery cell under target abuse conditions, including: Under overcharge conditions, the curves of the actual voltage and internal gas composition of the battery cell over time are obtained and used as the first curve and the second curve, respectively. The time when the target gas first appears is obtained from the second curve, and the actual cell voltage at the same time is obtained on the first curve and used as the first voltage. Differentiating the first curve yields the first first derivative curve, which can be used as the third curve. The actual cell voltage in the first curve corresponding to the first time the first derivative is greater than the preset threshold is obtained from the third curve, and used as the second voltage. The ratio of the first voltage to the second voltage is used as the target normalized voltage; wherein, the target gas is a reducing gas with double or multiple bonds; The second determining module is used to determine the internal air pressure of the battery cell corresponding to the target normalized voltage under the target abuse condition, so as to serve as the opening pressure of the safety valve.

7. A computer device, characterized in that, It includes a processor and a memory; wherein, when the processor executes the computer program stored in the memory, it implements the steps of the method for determining the opening pressure of the battery cell safety valve as described in any one of claims 1-5.

8. A computer-readable storage medium, characterized in that, Used to store computer programs; when the computer programs are executed by a processor, they implement the steps of the method for determining the opening pressure of the battery cell safety valve as described in any one of claims 1-5.

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