A method, system, device and medium for screening the self-discharge performance of battery cells

Abstract

The present invention relates to a method, system, device and medium for screening the self-discharge performance of battery cells. The method includes the following steps: solving the parameters of the voltage decay model and obtaining the preliminary screening results of all battery cells to be tested; predicting the voltage drop of the battery cells to be tested after a preset time interval based on the voltage decay model to obtain the final screening results of the battery cells to be tested. The present invention can quickly and accurately screen the self-discharge performance of battery cells, and thus can be widely applied to the field of battery cell technology.

Description

Technical Field

[0001] The present invention relates to a method, system, device and medium for screening the self-discharge performance of battery cells, belonging to the technical field of battery cells. Background Art

[0002] Currently, governments of various countries are actively promoting the development of new energy vehicles, and battery cells are widely used in new energy electric vehicles. Single batteries are usually assembled into a system in series and parallel forms, so the inconsistency of batteries will greatly affect the performance of the system. Self-discharge is a common and important inconsistency index of battery cells, referring to the phenomenon that the capacity of the battery slowly decreases during storage, usually quantified by voltage drop, mainly divided into chemical self-discharge mainly caused by side reactions at the electrolyte and electrode interface and physical self-discharge mainly caused by internal micro-shorts. Although self-discharge is inevitable, batteries with excessive self-discharge will reduce the service life of the system and even cause safety problems. Therefore, it is crucial to screen battery cells with poor self-discharge performance at the production end. The current screening method is to place the battery in a normal temperature or high temperature environment after battery formation, and calculate the self-discharge rate through the voltage difference and time difference before and after standing, and screen out the batteries with excessive self-discharge.

[0003] There are many research and screening methods for the self-discharge of battery cells. For example, by standing the battery cells at different temperatures to distinguish physical self-discharge and chemical self-discharge, but this method is complex to operate; by applying charge and discharge excitation to the battery cells, using an equivalent circuit model to obtain the self-discharge current to quickly judge the self-discharge performance of the battery; or by proposing to collect the battery voltage multiple times, establishing a relationship between the time difference and voltage ratio, predicting the voltage of the battery to be tested, and screening out battery cells with poor self-discharge, etc.

[0004] Although there are many methods for judging the self-discharge of battery cells, they often cannot take into account the accuracy of the results, short test cycle, and simplicity of operation. The main problem in screening the self-discharge of battery cells is the long test cycle. The longer the time, the higher the accuracy, but it greatly affects the production efficiency of products. Another problem is misjudgment. Batteries with a low self-discharge rate in the early stage may also show an accelerated voltage drop rate in the later stage. Therefore, developing a fast and accurate method for screening the self-discharge of battery cells has become one of the key technical problems urgently to be solved in lithium-ion batteries. Summary of the Invention

[0005] In view of the above problems, the purpose of the present invention is to provide a method, system, device and medium for screening the self-discharge performance of battery cells, which can quickly and accurately screen the self-discharge performance of battery cells.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides a method for screening the self-discharge performance of battery cells, including the following steps:

[0008] Solve the parameters of the voltage attenuation model and obtain the preliminary screening results of all cells to be tested;

[0009] Based on the voltage attenuation model, predict the voltage drop of the cells to be tested after a preset time interval to obtain the final screening results of the cells to be tested.

[0010] Furthermore, the method for solving the parameters of the voltage attenuation model and obtaining the preliminary screening results of all cells to be tested includes:

[0011] Conduct self-discharge tests on the cells and collect relevant data;

[0012] Build a voltage attenuation model;

[0013] Solve the model parameters of the voltage attenuation model based on the collected relevant data;

[0014] Based on the model parameters, conduct a preliminary screening of the cells to be tested to obtain the preliminary screening results.

[0015] Furthermore, the method for conducting self-discharge tests on the cells and collecting relevant data includes:

[0016] Charge the cells to be tested after formation to a preset initial state of charge and place them at a preset storage temperature;

[0017] After standing for a first period of time, obtain the open-circuit voltage of the cell to be tested as the initial open-circuit voltage;

[0018] Repeat the above step until the open-circuit voltages corresponding to the cell to be tested at n test times are obtained, and associate the test times and open-circuit voltage values with the information of the cell to be tested, where n≥3.

[0019] Furthermore, the voltage attenuation model is:

[0020] V n =V 0 -BΔt z

[0021] where V n and V 0 represent the nth and initial open-circuit voltages respectively; Δt represents the time difference between the nth open-circuit voltage and the initial open-circuit voltage test; B represents the voltage attenuation constant, and z represents the power value.

[0022] Furthermore, the method for predicting the voltage drop of the cells to be tested after a preset time interval based on the voltage attenuation model to obtain the final screening results of the cells to be tested includes:

[0023] Based on the voltage attenuation model, predict the voltage drop of each cell to be tested after a preset time interval;

[0024] Perform a normal distribution fitting on the predicted values of the voltage drops of all the cells to be tested, and obtain the mean μ and variance σ corresponding to the predicted values of the voltage drops of all the cells to be tested;

[0025] Based on the obtained mean μ and variance σ, perform a second screening on the cells to be tested after the initial screening to obtain the final screening result.

[0026] Further, the preset time interval range is 30 - 90 days.

[0027] Further, it further includes the following steps:

[0028] Based on the variance σ of the cells to be tested, divide the screened cells to be tested into multiple groups, and assemble them into modules or battery systems according to the groups respectively.

[0029] In a second aspect, the present invention provides a cell self-discharge performance screening system, including:

[0030] An initial screening module, configured to solve the parameters of the pre-established voltage attenuation model based on the obtained self-discharge test data of the cells to be tested, and obtain the initial screening results of all the cells to be tested;

[0031] A final screening module, based on the voltage attenuation model, predicts the voltage drop of the cells to be tested after a preset time interval to obtain the final screening results of the cells to be tested.

[0032] In a third aspect, the present invention provides a processing device, which at least includes a processor and a memory. A computer program is stored on the memory, and when the processor runs the computer program, it executes to implement the steps of the cell self-discharge performance screening method.

[0033] In a fourth aspect, the present invention provides a computer storage medium, on which computer-readable instructions are stored, and the computer-readable instructions can be executed by a processor to implement the steps of the cell self-discharge performance screening method.

[0034] Due to the above technical solutions adopted by the present invention, it has the following advantages:

[0035] 1. The present invention performs two screenings on all the cells to be tested. The initial screening is performed on the cells based on the cell discharge law, effectively avoiding the abnormal cells with small voltage drops in the early stage and large voltage drops in the later stage from flowing out. And the second screening based on the predicted voltage drop in the long term can rescue the over-killed cells with large voltage drops in the early stage and small voltage drops in the later stage, improving the test accuracy;

[0036] 2. When the present invention conducts the initial screening of the battery cells, only three open-circuit voltage tests need to be performed on the battery cells to solve the parameters of the voltage attenuation model, and then predict the long-term self-discharge. The three tests can be shortened to within 10 days, effectively shortening the test cycle;

[0037] 3. The voltage attenuation model established by the present invention adopts a power function form, which can more intuitively display the voltage drop change rate and can quickly and accurately screen out defective batteries;

[0038] Therefore, the present invention can be widely applied to the technical field of battery cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0040] Figure 1 are schematic diagrams of two self-discharge laws of the battery cells provided by the embodiments of the present invention;

[0041] Figure 2 is a flowchart of a method for quickly screening the self-discharge performance of the battery cells provided by the embodiments of the present invention;

[0042] Figure 3 is a graph of the test voltage and standing time of the battery cells in the embodiments of the present invention;

[0043] Figure 4 is a box plot of the predicted voltage drop value of the battery cells after 90 days in the embodiments of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present invention fall within the scope of protection of the present invention.

[0045] It should be noted that the terms used here are only for the purpose of describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used here, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0046] The current method for judging the self-discharge of battery cells is to place the battery in a normal temperature or high temperature environment after formation, calculate the self-discharge rate by measuring the voltage difference and time difference before and after standing, and eliminate the battery cells with excessive self-discharge. For this two-point k-value method, if the voltage measurement error is large in a certain test, it will greatly affect the accuracy of the k-value.

[0047] As Figure 1 shown, through long-term self-discharge tests on battery cells, the present invention finds that battery cells with a small k-value may have a large voltage drop, while battery cells with a large k-value may not have a large voltage drop. That is, there are two laws in the self-discharge curve of battery cells. The first law is that the voltage drop rate in the early stage of the self-discharge curve of battery cells is fast and gradually slows down in the later stage. The second law is that the voltage drop rate in the early stage of the self-discharge curve of battery cells is slow and gradually speeds up in the later stage. For the second law, the current k-value method has misjudgments because battery cells with a low self-discharge rate in the early stage may also show an accelerated voltage drop rate in the later stage.

[0048] Based on the above analysis results of the two laws of the self-discharge curve of battery cells, the present invention proposes a method for screening the self-discharge performance of battery cells, including: solving the parameters of the voltage attenuation model and obtaining the preliminary screening results of all battery cells to be tested; predicting the voltage drop of the battery cells to be tested after a preset time interval based on the voltage attenuation model to obtain the final screening results of the battery cells to be tested. The present invention screens all battery cells to be tested twice. The first screening is based on the discharge law of battery cells, effectively avoiding the abnormal battery cells with a small voltage drop in the early stage and a large voltage drop in the later stage from flowing out. The second screening based on predicting the voltage drop in the long term can rescue the over-killed battery cells with a large voltage drop in the early stage and a small voltage drop in the later stage, improving the test accuracy.

[0049] Embodiment 1

[0050] As Figure 2 shown, this embodiment provides a method for screening the self-discharge performance of battery cells, including the following steps:

[0051] Step S1, solve the parameters of the voltage attenuation model and obtain the preliminary screening results of all battery cells to be tested.

[0052] Among them, the above step S1 can be implemented through the following steps:

[0053] S11, conduct self-discharge tests on battery cells and collect relevant data.

[0054] Specifically, it includes the following steps:

[0055] Charge the battery cells to be tested after formation to a preset initial state of charge and place them at a preset storage temperature;

[0056] After standing for the first time, obtain the open-circuit voltage of the battery cells to be tested as the initial open-circuit voltage;

[0057] Repeat the above step until the open-circuit voltages corresponding to the battery cell under test at n test times are obtained, and associate the test times and the open-circuit voltage values with the information of the battery cell under test.

[0058] Optionally, the above preset initial state of charge can be any value within 0% - 100% SOC. Considering capacity loss and resolution, in this embodiment, the selection range of the preset initial state of charge is recommended to be 30 - 80% SOC, preferably 70% SOC.

[0059] Optionally, the above preset storage temperature should be within the preset storage temperature range. Based on the influence of temperature on the battery cell, that is, the higher the temperature, the higher the resolution, but the greater the capacity loss. In this embodiment, the range of the preset storage temperature is set to 25 - 50 °C.

[0060] Optionally, the above first time is to make the temperature of the battery cell under test consistent with the external temperature. In this embodiment, it is preferably 1 - 5 h and can be set according to actual needs.

[0061] Optionally, the above n test times are selected according to actual needs. Generally, n ≥ 3.

[0062] Preferably, when n is equal to 3, considering both time and accuracy requirements, the selection range of the second test time is 24 - 72 h, and the selection range of the third test time is 120 - 240 h.

[0063] S12. Build a voltage decay model.

[0064] To analyze the voltage drop rate of the battery cell more intuitively, in this embodiment, a voltage decay model is built based on a power function, and the formula is:

[0065] V n =V 0 -BΔt z (1)

[0066] Wherein, V n and V 0 respectively represent the nth and initial open-circuit voltages; Δt represents the time difference between the nth open-circuit voltage and the initial open-circuit voltage test; B represents the voltage decay constant, z represents the power value, and B and z are the parameters to be solved in the voltage decay model.

[0067] Transform formula (1), and we get

[0068] ΔV=V 0 -V n =Bt z (2)

[0069] Wherein, ΔV is the voltage drop value.

[0070] Derive formula (2), and we get:

[0071]

[0072] As can be seen from the above formula, when z is less than 1, it represents the first self-discharge law, that is, the initial voltage drop rate is relatively large and then gradually slows down. When z is greater than 1, it represents the second self-discharge law, that is, the initial voltage drop rate is relatively small and then gradually speeds up. Therefore, the initial screening of the battery cells can be carried out according to the value of the power z.

[0073] S13. Solve the model parameters of the voltage decay model based on the collected relevant data.

[0074] When measuring the open-circuit voltage three times, substitute the test values of the three open-circuit voltages into formula (1) respectively, and we get:

[0075] V 1 = V 0 - B(Δt 1 ) z (4)

[0076] V 2 = V 0 - B(Δt 2 ) z (5)

[0077] Among them, (V 0 , t 0 ), (V 1 , t 0 + Δt 1 ), (V 2 , t 0 + Δt 2 ) are the test values and test times of the initial open-circuit voltage, the first open-circuit voltage, and the second open-circuit voltage respectively.

[0078] Solve the equations of formula (4) and formula (5) simultaneously to obtain the fitting parameters B and z. Among them, the solution of the power value z is shown in formula (6), and the solution of the voltage drop decay rate constant B is shown in formula (7). After completing the three open-circuit voltage tests, the output results can be calculated in real time.

[0079]

[0080]

[0081] When measuring the open-circuit voltage more than three times, take the logarithm of both sides of formula (2) to get formula (8). It can be seen that Ln(V 0 - V n ) and Ln(Δt n ) are linearly related. Take Ln(Δtn ) is the independent variable, and taking Ln(V 0 -V n ) as the dependent variable, the fitting formula (9) is obtained through linear fitting, where the solution of the power value z is shown in formula (10), and the solution of the voltage drop attenuation rate constant B is shown in formula (11).

[0082] Ln(V 0 -V n ) = LnB + zLn(Δt n ) (8)

[0083] y = b + ax (9)

[0084] z = a (10)

[0085] B = exp(b) (11)

[0086] Conventional k-value tests usually take 10 days or 20 days, and the latter is more common. To improve the accuracy, the test cycles mentioned in many existing technologies are even longer. In this embodiment, through fitting the results of three times (the test cycle can be shortened to within 10 days) or more, the long-term self-discharge is predicted, effectively shortening the test cycle.

[0087] S14. Based on the model parameters, the cells to be tested are preliminarily screened to obtain the preliminary screening results.

[0088] According to the above analysis, based on the obtained voltage attenuation model parameter z, the preliminary screening results of the cells to be tested can be realized. Specifically, if z > 1.0, the later self-discharge rate of the cells to be tested will become larger and larger, and they should be regarded as defective products.

[0089] Step S2. Based on the voltage attenuation model, predict the voltage drop of the cells to be tested after a preset time interval to obtain the final screening results of the cells to be tested.

[0090] Among them, the above step S2 can be realized through the following steps:

[0091] Step S21. Based on the voltage attenuation model, predict the voltage drop of each cell to be tested after a preset time interval.

[0092] Optionally, since the voltage drop values of the same batch of batteries in the short term have a small difference and the resolution is relatively small, the preset time interval should be a relatively long time. After considering time and accuracy, this embodiment recommends setting the preset time interval range to 30 - 90 days, preferably 30 days.

[0093] Step S22. Perform normal distribution fitting on the predicted voltage drop values of all the cells to be tested to obtain the mean μ and variance σ corresponding to the predicted voltage drop values of all the cells to be tested.

[0094] Step S23: Based on the obtained mean value μ and variance σ, re-screen the cells to be tested after the initial screening to obtain the final screening result.

[0095] Optionally, when re-screening the cells to be tested after the initial screening, set the screening condition as:

[0096] If ΔV > μ + 3σ, it is regarded as a product with poor self-discharge.

[0097] Preferably, after the above step S23, the following steps are further included:

[0098] S24: Based on the variance σ of the cells to be tested, divide the screened cells to be tested into multiple groups, and assemble them into modules or battery systems according to the groups respectively.

[0099] Actually, according to the mean value μ and variance σ of the predicted voltage drop of the cells to be tested in the same batch, dividing the batteries into multiple groups according to σ and assembling them into modules or battery systems respectively can greatly improve the consistency of the batteries and optimize the system performance.

[0100] The method for screening the self-discharge performance of the cells in the embodiments of the present invention can be applied to the screening of cells and can also be applied to the optimization of module grouping. In this regard, the embodiments of the present invention do not make any restrictions.

[0101] Embodiment 2

[0102] Taking a ternary lithium-ion battery produced by a domestic manufacturer and applied to mild hybrid as an example, the specific implementation manner of the present invention will be further described below.

[0103] First, perform formation on the cells to be tested, then adjust the initial state of charge (SOC) to 30%, then let it stand for 3 days at 25°C to eliminate polarization, test the open-circuit voltage at this time and record it as the initial open-circuit voltage V 0 , and the test time is t 0 . Continue to let it stand for 3 days at this temperature, and record the open-circuit voltage of the re-test as the first test voltage V 1 , and the test time is t 1 . Then continue to let it stand for 6 days at this temperature, and record the open-circuit voltage of the re-test as the second test voltage V 2 , and the test time is t 2 . The relevant original test data is summarized in Table 1, and the self-discharge attenuation trend is shown in Figure 3 .

[0104] Table 1 Open-circuit voltage test results of the cells under the static condition of 25°C - 30% SOC

[0105] Battery number <![CDATA[V 0 (V)]]> <![CDATA[V 1 (V)]]> <![CDATA[V 2 (V)]]> <![CDATA[Δt 1 = t 1 - t 0 > <![CDATA[Δt 2 = t 2 - t 0 > 1# 3.56190 3.56121 3.56002 3 9 2# 3.56184 3.56106 3.55980 3 9 3# 3.56187 3.56105 3.55971 3 9 4# 3.56165 3.56059 3.55860 3 9 5# 3.56249 3.56180 3.56062 3 9 6# 3.56255 3.56182 3.56062 3 9 7# 3.56212 3.56185 3.56082 3 9 8# 3.56173 3.56067 3.55905 3 9 9# 3.56146 3.56049 3.55888 3 9 10# 3.56156 3.56078 3.55948 3 9 11# 3.56452 3.56363 3.56224 3 9 12# 3.56206 3.56133 3.56013 3 9 13# 3.56198 3.56114 3.55975 3 9 14# 3.56228 3.56151 3.56025 3 9 15# 3.56302 3.5624 3.56131 3 9

[0106] Substitute the above raw data into the parameter fitting formula, and the results are shown in Table 2. Among them, the power value of the 7# cell is 1.4330, which is greater than 1.0, belonging to the defective product with an increasing self-discharge rate in the later stage. Here, the voltage value after 90 days is selected as the judgment standard for the self-discharge performance of the cell. The box plot of the predicted voltage drop of the remaining batteries after 90 days is shown in Figure 4 , the mean and variance of the voltage drop are 17.0 and 3.4 respectively, and the upper limit value of 3σ is 27.2 mV. Among them, the voltage of the 4# cell is higher than this specification and is judged as a defective product.

[0107] Table 2 Fitting values of cell self-discharge parameters and two judgments

[0108]

[0109]

[0110] Obviously, the above-mentioned implementation cases are only examples for more clearly describing the present invention, rather than limitations on the implementation manners of the present invention. For example, the SOC and temperature of cell testing are not limited to the data in this example.

[0111] Example 3

[0112] The above Example 1 provides a method for screening the self-discharge performance of cells. Correspondingly, this example provides a system for screening the self-discharge performance of cells. The system provided in this example can implement a method for screening the self-discharge performance of cells in Example 1, and this system can be implemented in a software, hardware, or a combination of software and hardware manner. For example, this system can include integrated or separate functional modules or functional units to execute the corresponding steps in each method of Example 1. Since the system in this example is basically similar to the method embodiment, the description process in this example is relatively simple. For related parts, reference can be made to the partial description of Example 1. The embodiments of the system provided in this example are only illustrative.

[0113] A system for screening the self-discharge performance of cells provided in this example includes:

[0114] A preliminary screening module, configured to solve the parameters of the pre-built voltage attenuation model based on the obtained self-discharge test data of the cells to be tested, and obtain the preliminary screening results of all cells to be tested;

[0115] A final screening module, based on the voltage attenuation model, predicts the voltage drop of the cells to be tested after a preset time interval, and obtains the final screening results of the cells to be tested.

[0116] Example 4

[0117] This embodiment provides a processing device corresponding to the method for screening the self-discharge performance of the battery cells provided in Embodiment 1. The processing device can be a processing device for a client, such as a mobile phone, a laptop computer, a tablet computer, a desktop computer, etc., to execute the method of Embodiment 1.

[0118] The processing device includes a processor, a memory, a communication interface, and a bus. The processor, the memory, and the communication interface are connected through the bus to complete communication with each other. A computer program that can run on the processor is stored in the memory. When the processor runs the computer program, it executes the method for screening the self-discharge performance of the battery cells provided in Embodiment 1.

[0119] In some embodiments, the memory can be a high-speed random access memory (RAM: Random Access Memory), and may also include a non-volatile memory, such as at least one disk memory.

[0120] In other embodiments, the processor can be a general-purpose processor of various types such as a central processing unit (CPU), a digital signal processor (DSP), etc., which is not limited here.

[0121] Embodiment 5

[0122] The method for screening the self-discharge performance of the battery cells in Embodiment 1 of this embodiment can be specifically implemented as a computer program product. The computer program product can include a computer-readable storage medium, on which computer-readable program instructions for executing the method for screening the self-discharge performance of the battery cells described in Embodiment 1 are loaded.

[0123] The computer-readable storage medium can be a tangible device that holds and stores instructions used by an instruction execution device. The computer-readable storage medium can be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any combination of the above.

[0124] The content not described in detail in this specification belongs to the prior art well-known to those skilled in the art.

[0125] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for screening the self-discharge performance of battery cells, characterized in that, it includes the following steps: Solve the parameters of the voltage decay model and obtain the preliminary screening results of all battery cells to be tested; Based on the voltage decay model, predict the voltage drop of the battery cells to be tested after a preset time interval to obtain the final screening results of the battery cells to be tested; The method for solving the parameters of the voltage decay model and obtaining the preliminary screening results of all battery cells to be tested includes: Conduct self-discharge tests on the battery cells and collect relevant data; Build a voltage decay model; Solve the model parameters of the voltage decay model based on the collected relevant data; Based on the model parameters, conduct a preliminary screening of the battery cells to be tested to obtain preliminary screening results; The voltage decay model is: Among them, respectively represent the nth and initial open-circuit voltages; represents the time difference between the nth open-circuit voltage test and the initial open-circuit voltage test; B represents the voltage decay constant, and z represents the power value.

2. The method for screening the self-discharge performance of battery cells according to claim 1, characterized in that, the method for conducting self-discharge tests on the battery cells and collecting relevant data includes: Charge the battery cells to be tested after formation to a preset initial state of charge and place them at a preset storage temperature; After standing for a first period of time, obtain the open-circuit voltage of the battery cells to be tested as the initial open-circuit voltage; Repeat the above step until the open circuit voltages corresponding to the cell under test at n test times are obtained, and associate the test times and open circuit voltage values with the cell under test information, where, .

3. The method for screening the self-discharge performance of battery cells according to claim 1, characterized in that, the method for predicting the voltage drop of the battery cells to be tested after a preset time interval based on the voltage decay model to obtain the final screening results of the battery cells to be tested includes: Based on the voltage decay model, predict the voltage drop of each battery cell to be tested after a preset time interval; Perform a normal distribution fitting on the predicted voltage drop values of all battery cells to be tested to obtain the mean μ and variance σ corresponding to the predicted voltage drop values of all battery cells to be tested; Based on the obtained mean μ and variance σ, conduct a secondary screening of the battery cells to be tested after the initial screening to obtain the final screening results.

4. The method for screening the self-discharge performance of battery cells according to claim 3, characterized in that, the preset time interval ranges from 30 to 90 days.

5. The method for screening the self-discharge performance of battery cells according to claim 3, characterized in that, it further includes the following steps: Based on the variance σ of the battery cells to be tested, divide the screened battery cells to be tested into multiple groups and assemble them into modules or battery systems according to the groups respectively.

6. A system for screening the self-discharge performance of battery cells, characterized in that, it includes: A preliminary screening module for solving the parameters of a pre-built voltage decay model based on the self-discharge test data of the battery cells to be tested and obtaining the preliminary screening results of all battery cells to be tested; A final screening module for predicting the voltage drop of the battery cells to be tested after a preset time interval based on the voltage decay model to obtain the final screening results of the battery cells to be tested; The method for solving the parameters of the voltage decay model and obtaining the preliminary screening results of all battery cells to be tested includes: Conduct self-discharge tests on the battery cells and collect relevant data; Build a voltage decay model; Solve the model parameters of the voltage decay model based on the collected relevant data; Based on the model parameters, conduct a preliminary screening of the battery cells to be tested to obtain preliminary screening results; The voltage decay model is: Among them, respectively represent the nth and the initial open-circuit voltage; represents the time difference between the nth open-circuit voltage test and the initial open-circuit voltage test; B represents the voltage decay constant, and z represents the power value.

7. A processing device, the processing device at least includes a processor and a memory, and a computer program is stored on the memory, characterized in that, When the processor runs the computer program, it executes steps to implement the method for screening the self-discharge performance of the battery cell according to any one of claims 1 to 5.

8. A computer storage medium, characterized in that, it stores computer-readable instructions that can be executed by a processor to implement the steps of the method for screening the self-discharge performance of the battery cell according to any one of claims 1 to 5.

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