Battery cell screening method, device and equipment and storage medium

Abstract

The invention provides a battery cell screening method, device and equipment and a storage medium. The method comprises the following steps: determining the ratio of the anode capacity to the cathode capacity of each candidate battery cell in each battery cell of the same batch; according to the ratio of the anode capacity to the cathode capacity of each candidate cell, calculating the ratio deviation between the anode capacity and the cathode capacity of each candidate cell; grouping the candidate cells according to the deviation of the ratio of the anode capacity to the cathode capacity; wherein the deviation of the ratio of the anode capacity to the cathode capacity between the candidate cells in the same group is smaller than a preset deviation. The method can prevent the battery pack from influencing the service life and safety of the battery due to the difference between the single cells.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and more specifically, to a method, device, equipment and storage medium for cell screening in the field of battery technology. Background Art

[0002] Lithium-ion batteries have become the main power source for digital products due to their high energy density, long life cycle, low self-discharge and low environmental pollution. Due to process fluctuations, even cells in the same batch will have differences. If they are randomly assembled without screening, these differences will seriously reduce the service life of the entire battery pack, so it is necessary to screen the batteries for consistency.

[0003] At present, due to fluctuations in the operating environment during the battery manufacturing process, lithium-ion batteries generally have parameter inconsistencies. Most existing technologies pair cells into groups based on parameters that are not directly linked to cycle performance, such as voltage, capacity, and internal resistance. This method ignores the fact that cell differences will continue to increase as the battery module operates, leading to reduced module performance, shortened service life, and even safety issues. Therefore, how to prevent differences between single cells from affecting battery life and safety has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present application provides a method, device, equipment and storage medium for cell screening, which can prevent the battery life and safety of the battery pack from being affected by differences between single cells.

[0005] In a first aspect, a method for screening battery cells is provided, the method comprising: determining the ratio of anode capacity to cathode capacity (hereinafter referred to as: NP ratio) of each candidate battery cell in the same batch; calculating the ratio deviation of anode capacity to cathode capacity between the candidate battery cells (hereinafter referred to as: NP ratio deviation) according to the NP ratio of the above candidate battery cells; grouping the candidate battery cells according to the NP ratio deviation; wherein the NP ratio deviation between the candidate battery cells in the same group is less than a preset deviation.

[0006] In the above technical solution, for each battery cell of the same batch, the NP ratio deviation between each candidate battery cell is calculated according to the NP ratio of each candidate battery cell in each battery cell of the same batch, and each candidate battery cell is grouped according to the NP ratio deviation, and the NP ratio deviation between the candidate battery cells in the same group is less than the preset deviation. Since the NP ratio of the battery cell is directly related to the cycle performance of the battery cell, it can take into account the consistency of the battery cell in the initial stage and the entire life cycle after the battery cell is activated. Therefore, the candidate battery cells with NP ratio deviation less than the preset deviation are divided into a group, taking into account the differences of the battery cells under the dynamic cycle conditions, which is conducive to avoiding the differences between the candidate batteries in the same group from being continuously amplified as the battery pack is operated, and thus avoiding the battery pack being affected by the differences between the single battery cells. Life and safety of the battery.

[0007] In combination with the first aspect, in some possible implementations, determining the NP ratio of each candidate battery cell in each battery cell of the same batch includes: obtaining the capacity of each battery cell of the same batch; selecting multiple battery cells from each battery cell as multiple battery cells to be tested according to the capacity of each battery cell; wherein the capacity of the multiple battery cells to be tested includes multiple different capacities; performing charge and discharge tests on the multiple battery cells to be tested respectively to determine the charge state (State of Charge) of each of the battery cells to be tested. wherein the target SOC indicates that the reaction of the active materials of the battery cell to be tested has ended; the multiple battery cells to be tested are disassembled, and the NP ratios of the multiple battery cells to be tested after disassembly are calculated; a linear relationship between the NP ratios and the voltage is constructed according to the NP ratios of the multiple battery cells to be tested and the voltage when the SOC of each of the battery cells to be tested reaches the target SOC; a discharge test is performed on each of the candidate battery cells to determine the voltage when the SOC of each of the candidate battery cells is discharged to reach the target SOC; the NP ratio of each of the candidate battery cells is determined according to the voltage when the SOC of each of the candidate battery cells is discharged to reach the target SOC and the linear relationship.

[0008] In the above technical scheme, the inventor of the present application found that there is a linear relationship between the NP ratio and the voltage of the battery cell when its SOC reaches the SOC at the end of the active material reaction during the charge and discharge period. Therefore, in the present application, multiple batteries of different capacities are screened out from each battery cell of the same batch as the battery cells to be tested for charge and discharge tests to obtain the voltage when its SOC reaches the SOC at the end of the active material reaction, and then the screened battery cells to be tested are disassembled to calculate the NP ratio of the disassembled battery cells, so as to construct a linear relationship based on the voltage and NP ratio of the above multiple battery cells to be tested. The remaining battery cells in each battery cell of the same batch, i.e., each candidate battery cell, are charged and discharged to obtain the voltage when the SOC of these candidate battery cells reaches the target SOC, so that the NP ratio of each candidate battery cell can be calculated by combining the above linear relationship and the voltage when the SOC of each candidate battery cell reaches the target SOC. The calculation method of the NP ratio provided by the above technical scheme can accurately and reasonably calculate the NP ratio of each candidate battery cell by using the constructed linear relationship.

[0009] In combination with the first aspect and the above-mentioned implementation methods, in some possible implementation methods, the above-mentioned selecting multiple battery cells from each of the battery cells as multiple battery cells to be tested based on the capacity of each of the battery cells includes: determining a distribution interval of the capacity of each of the battery cells; dividing the above-mentioned distribution interval to obtain multiple capacity intervals; based on the above-mentioned multiple capacity intervals, selecting multiple battery cells from each of the battery cells as multiple battery cells to be tested; wherein the capacities of the above-mentioned multiple battery cells to be tested are distributed in the above-mentioned multiple capacity intervals.

[0010] In the above technical solution, by dividing the capacity distribution interval, the capacities of the multiple battery cells to be tested that are finally selected can be distributed in multiple capacity intervals. Since battery cells with different capacities usually have certain differences in NP ratios, the NP ratios of the battery cells to be tested whose capacities are distributed in multiple capacity intervals can usually also have certain differences. This is equivalent to combining multiple different points when constructing a linear relationship, which is conducive to better fitting the linear relationship between the NP ratio and the voltage.

[0011] In combination with the first aspect and the above-mentioned implementation methods, in some possible implementation methods, the above-mentioned distribution interval is divided to obtain multiple capacity intervals, including: calculating the capacity average and standard deviation according to the capacity of each of the above-mentioned battery cells; taking the above-mentioned capacity average as the division center and the above-mentioned standard deviation as the length of the capacity interval, dividing the above-mentioned distribution interval to obtain multiple capacity intervals; wherein the above-mentioned multiple capacity intervals include a first type of capacity interval and a second type of capacity interval, the capacity within the above-mentioned first type of capacity interval is greater than or equal to the above-mentioned capacity average, and the capacity within the above-mentioned second type of capacity interval is less than the above-mentioned capacity average.

[0012] In the above technical scheme, considering that the capacity of normally produced battery cells is normally distributed due to process fluctuations, the distribution interval is divided with the capacity average value of each battery cell in the same batch as the division center and the capacity standard deviation of each battery cell in the same batch as the division interval to obtain multiple capacity intervals, which is conducive to meeting the characteristic that the capacity is normally distributed during battery cell production, and the capacity in the first type of capacity interval in the multiple capacity intervals is greater than or equal to the capacity average value, and the capacity in the second type of capacity interval is less than the capacity average value, that is, the multiple capacity intervals are distributed before and after the capacity average value, so that the battery cells to be tested finally selected can include both battery cells to be tested with a capacity greater than the capacity average value and battery cells to be tested with a capacity less than the capacity average value, which is conducive to making the multiple points for constructing a linear relationship reasonably evenly distributed, so that the constructed linear relationship is more reasonable and accurate, and further makes the NP ratio of the candidate battery cells calculated in combination with the linear relationship more accurate, so that the battery cell grouping based on the NP ratio is finally more reasonable and accurate, and the dynamic consistency is better.

[0013] In combination with the first aspect and the above-mentioned implementation methods, in some possible implementation methods, the above-mentioned multiple battery cells are selected from each of the above-mentioned battery cells as multiple battery cells to be tested according to the above-mentioned multiple capacity intervals, including: for each of the above-mentioned capacity intervals, selecting a target capacity within the above-mentioned capacity interval; selecting at least two battery cells with a capacity of the above-mentioned target capacity from each of the above-mentioned battery cells as battery cells to be tested whose capacities are distributed in the above-mentioned capacity intervals.

[0014] In the above technical solution, it is equivalent to selecting at least two battery cells with different capacities in each capacity range as the battery cells to be tested, which is helpful to reduce the test error.

[0015] In combination with the first aspect and the above-mentioned implementation methods, in some possible implementation methods, for each of the above-mentioned capacity intervals, selecting the target capacity within the above-mentioned capacity interval includes: for each of the above-mentioned capacity intervals, using the middle capacity of the above-mentioned capacity interval as the target capacity selected in each of the above-mentioned capacity intervals.

[0016] In the above technical solution, for each capacity interval, the middle capacity of the capacity interval is used as the target capacity selected in each capacity interval, so that the NP ratios of multiple cells to be tested can be evenly distributed, which is conducive to constructing a more accurate linear relationship.

[0017] In combination with the first aspect and the above-mentioned implementation methods, in some possible implementation methods, the above-mentioned charge and discharge tests are performed on the above-mentioned multiple battery cells to be tested respectively to determine the voltage when the SOC of each of the above-mentioned battery cells to be tested reaches the target SOC, including: for each of the above-mentioned battery cells to be tested, using a preset charging current and charging voltage, and performing a charging test on the above-mentioned battery cell to be tested until the voltage of the above-mentioned battery cell to be tested reaches the full charge voltage; after the voltage of the above-mentioned battery cell to be tested reaches the full charge voltage, using a preset discharge rate, and performing a discharge test on the above-mentioned battery cell to be tested until the voltage of the above-mentioned battery cell to be tested reaches the cut-off voltage, so as to obtain the discharge differential curve of the above-mentioned battery cell to be tested; and determining the voltage when the SOC of the above-mentioned battery cell to be tested reaches the target SOC according to the above-mentioned discharge differential curve.

[0018] In combination with the first aspect and the above-mentioned implementation manner, in some possible implementation manners, the above-mentioned preset discharge rate is less than or equal to 0.5C, the above-mentioned preset charging current is between 0.05C and 0.5C, and the above-mentioned preset charging voltage is between 3V and 4.45V.

[0019] In a second aspect, a device for screening battery cells is provided, which includes: an NP ratio determination module, used to determine the NP ratio of each candidate battery cell in each battery cell of the same batch; an NP ratio deviation calculation module, used to calculate the NP ratio deviation between the above-mentioned candidate battery cells based on the NP ratios of the above-mentioned candidate battery cells; a grouping module, used to group the above-mentioned candidate battery cells according to the above-mentioned NP ratio deviation; wherein the NP ratio deviation between the candidate battery cells in the same group is less than a preset deviation.

[0020] In a third aspect, an electronic device is provided, comprising a memory and a processor. The memory is used to store executable program code, and the processor is used to call and run the executable program code from the memory, so that the electronic device executes the method in the first aspect or any possible implementation of the first aspect.

[0021] In a fourth aspect, a computer program product is provided, comprising: a computer program code, which, when executed on a computer, enables the computer to execute the method in the first aspect or any possible implementation of the first aspect.

[0022] In a fifth aspect, a computer-readable storage medium is provided, which stores a computer program code. When the computer program code runs on a computer, the computer executes the method in the above-mentioned first aspect or any possible implementation manner of the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic flow chart of a method for cell screening provided in an embodiment of the present application;

[0024] Figure 2 is a schematic flow chart of an implementation method of step 101 provided in an embodiment of the present application;

[0025] Figure 3 is a schematic diagram of a dv / dq curve of a battery cell to be tested provided in an embodiment of the present application;

[0026] Figure 4 is a schematic diagram of a linear relationship between NP ratio and voltage provided in an embodiment of the present application;

[0027] Figure 5 It is a schematic diagram of the effect of a difference in NP ratio on the cycle performance of a battery cell provided in an embodiment of the present application;

[0028] Figure 6 It is a schematic diagram of the difference in cycle performance after a module is composed of cells with different NP ratios provided in an embodiment of the present application;

[0029] Figure 7 It is a structural schematic diagram of a battery cell screening device provided in an embodiment of the present application;

[0030] Figure 8 It is a structural schematic diagram of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0031] The technical solution in the present application will be described clearly and in detail below in conjunction with the accompanying drawings. In the description of the embodiments of the present application, unless otherwise specified, " / " means or, for example, A / B can mean A or B: "and / or" in the text is only a description of the association relationship of associated objects, indicating that there can be three relationships, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present application, "multiple" means two or more than two.

[0032] In the following, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as suggesting or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features.

[0033] The fluctuation of process capability and the difference of incoming batches inevitably lead to a certain degree of difference in parameters such as capacity, internal resistance, and shelf voltage. When multiple cells are used in series and parallel to meet the requirements of high voltage and high capacity, this difference is magnified, resulting in a significant reduction in the service life of the cells. The service life of module cells can be significantly improved through an effective consistency pairing method.

[0034] Currently, the most commonly used methods to solve module consistency are divided into two categories: static method and dynamic method. The static method is to use capacity classification equipment to test the capacity of the battery cells, eliminate the battery cells with unqualified capacity, and then use the battery cells with qualified capacity to form the module; the dynamic method is to perform a DC resistance test on the battery cells, apply a pulse current signal to compare the difference in the response voltage signal, and form the module according to the difference in the voltage signal.

[0035] The inventors of this application found that the disadvantage of both the static method and the dynamic method is that they do not take into account the significant activation process of the battery cell in the early stage of use. Due to the improved electrolyte infiltration effect in the early stage of the battery cell cycle, the capacity and internal resistance of the battery will undergo relatively obvious changes. The parameters obtained by the static method and the dynamic method cannot well evaluate the differences after activation, and the ability to control the entire life cycle is poor.

[0036] Based on this, the embodiment of the present application proposes a method for improving the consistency of module cells based on the cell NP ratio. The cell NP ratio is directly related to the cycle performance of the cell, and can take into account the consistency of the cell in the initial stage and throughout the life cycle of the cell after activation. Similar NP ratios can ensure that the cathode and anode potentials of the cell are consistent and the decay paths are consistent. Using the NP ratio as a parameter to evaluate cell consistency can simultaneously avoid the shortcomings of the poor accuracy of the static method and the dynamic method that only evaluates the consistency of the initial cell parameters, thereby improving the consistency of the grouped module cells throughout their life cycle.

[0037] Figure 1 It is a schematic flow chart of a method for cell screening provided in an embodiment of the present application.

[0038] For example, Figure 1 As shown, the method includes:

[0039] Step 101: Determine the NP ratio of each candidate battery cell in each battery cell of the same batch.

[0040] Step 102: Calculate the NP ratio deviation between the candidate cells according to the NP ratio of each candidate cell.

[0041] Step 103: grouping the candidate cells according to the NP ratio deviation; wherein the NP ratio deviation between the candidate cells in the same group is less than a preset deviation.

[0042] exist Figure 1In the illustrated embodiment, for each battery cell of the same batch, the NP ratio deviation between each candidate battery cell is calculated based on the NP ratio of each candidate battery cell in each battery cell of the same batch, and each candidate battery cell is grouped based on the NP ratio deviation, and the NP ratio deviation between the candidate battery cells in the same group is less than the preset deviation. Since the NP ratio of the battery cell is directly related to the cycle performance of the battery cell, it can take into account the consistency of the battery cell in the initial stage and the entire life cycle after the battery cell is activated. Therefore, the candidate battery cells with an NP ratio deviation less than the preset deviation are grouped into one group, taking into account the differences of the battery cells under the dynamic cycle conditions, which is conducive to avoiding the differences between the candidate battery cells in the same group from being continuously amplified as the battery pack is operated, and thus avoiding the battery pack being affected by the differences between the single battery cells. Life and safety of the battery.

[0043] Below Figure 1 The specific implementation methods of each step in the illustrated embodiment are described as follows:

[0044] In step 101, the NP ratio is the ratio of the negative electrode capacity to the positive electrode capacity of the battery cell. In this embodiment, the NP ratio of each candidate battery cell can be understood as: the ratio of the negative electrode capacity to the positive electrode capacity of each candidate battery cell. The above-mentioned candidate battery cells can be part of the battery cells of the same batch, specifically, they can be the remaining battery cells of the same batch except for the battery cells to be tested below, or they can be part of the remaining battery cells, which is not specifically limited in this embodiment.

[0045] In an exemplary embodiment, the implementation of step 101 can be found in Figure 2 Steps 1011 to 1017 in:

[0046] Step 1011: Obtain the capacity of each battery cell in the same batch.

[0047] Step 1012: selecting a plurality of cells from each cell as a plurality of cells to be tested according to the capacity of each cell; wherein the capacity of the plurality of cells to be tested includes a plurality of different capacities.

[0048] Step 1013: performing charge and discharge tests on the plurality of cells to be tested respectively, and determining the voltage when the SOC of each cell to be tested reaches the target SOC; wherein the target SOC indicates that the reaction of the active material of the cell to be tested is completed.

[0049] Step 1014: disassemble the plurality of cells to be tested, and calculate the NP ratios of the plurality of cells to be tested after being disassembled.

[0050] Step 1015: constructing a linear relationship between the NP ratio and the voltage according to the NP ratios of the plurality of cells to be tested and the voltage when the SOC of each cell to be tested reaches the target SOC.

[0051] Step 1016: Perform a discharge test on each candidate battery cell to determine the voltage of each candidate battery cell when the SOC reaches the target SOC.

[0052] Step 1017: Determine the NP ratio of each candidate battery cell according to the voltage of each candidate battery cell when the SOC is discharged to reach the target SOC and the above linear relationship.

[0053] The inventor of the present application has found that there is a linear relationship between the NP ratio and the voltage of the battery cell when its SOC reaches the SOC at the end of the active material reaction during the charge and discharge period. Therefore, in the present application, multiple batteries of different capacities are screened out from each battery cell of the same batch as the battery cells to be tested for charge and discharge tests to obtain the voltage when its SOC reaches the SOC at the end of the active material reaction, and then the screened battery cells to be tested are disassembled to calculate the NP ratio of the disassembled battery cells, so as to construct a linear relationship based on the voltage and NP ratio of the above multiple battery cells to be tested. The remaining battery cells in each battery cell of the same batch, i.e., each candidate battery cell, are charged and discharged to obtain the voltage when the SOC of these candidate battery cells reaches the target SOC, so that the NP ratio of each candidate battery cell can be calculated by combining the above linear relationship and the voltage when the SOC of each candidate battery cell reaches the target SOC. The calculation method of the NP ratio provided by the above technical solution can accurately and reasonably calculate the NP ratio of each candidate battery cell using the constructed linear relationship.

[0054] Below Figure 2 The specific implementation methods of each step in the illustrated embodiment are described as follows:

[0055] In step 1011, a capacity separation device may be used to test the capacity of each battery cell in the same batch to obtain the capacity of each battery cell in the same batch.

[0056] In step 1012, the capacity of each battery cell can be used as a reference to select multiple battery cells from each battery cell as multiple battery cells to be tested, and the capacities of the multiple battery cells to be tested finally selected include multiple different capacities. For example, the multiple battery cells to be tested include battery cells with a capacity of a, battery cells with a capacity of b, battery cells with a capacity of c, etc., a, b, c are different and there can be a certain interval between a, b, c, that is, the capacities of the multiple battery cells to be tested selected will not be too dense. Optionally, the multiple battery cells to be tested may also include multiple battery cells with a capacity of a, multiple battery cells with a capacity of b, and multiple battery cells with a capacity of c.

[0057] In an exemplary embodiment, step 1012 may be implemented by determining a distribution interval of the capacity of each battery cell, dividing the distribution interval to obtain multiple capacity intervals, and selecting multiple battery cells in each battery cell as multiple battery cells to be tested based on the multiple capacity intervals; wherein the capacities of the multiple battery cells to be tested are distributed in multiple capacity intervals.

[0058] Exemplarily, the maximum capacity and the minimum capacity can be determined among the capacities of the cells in the same batch, and the capacity distribution interval of each cell can be determined based on the maximum capacity and the minimum capacity, wherein the minimum capacity is the lower limit of the distribution interval, and the minimum capacity is the upper limit of the distribution interval. After determining the distribution interval, the distribution interval is divided to obtain multiple capacity intervals, and the multiple capacity intervals may not overlap with each other.

[0059] For example, assuming that the distribution interval is [Rmin, Rmax], and the number of capacity intervals to be divided is m, the distribution interval [Rmin, Rmax] can be evenly divided into m sub-intervals, and these m sub-intervals are used as m capacity intervals. After obtaining m capacity intervals, the battery cells with capacities in each capacity interval can be selected as the battery cells to be tested, so that the capacity of the battery cells to be tested can be distributed in multiple capacity intervals.

[0060] In the present embodiment, by dividing the capacity distribution intervals, the capacities of the multiple battery cells to be tested that are finally selected can be distributed in multiple capacity intervals. Since battery cells with different capacities usually have certain differences in NP ratios, the NP ratios of the battery cells to be tested whose capacities are distributed in multiple capacity intervals may usually also have certain differences. This is equivalent to combining multiple different points when constructing a linear relationship, which is conducive to better fitting the linear relationship between the NP ratio and the voltage.

[0061] In an exemplary embodiment, the above-mentioned division of the distribution interval to obtain multiple capacity intervals may include: first, calculating the capacity average and standard deviation according to the capacity of each battery cell, and then dividing the distribution interval with the capacity average as the division center and the standard deviation as the length of the capacity interval to obtain multiple capacity intervals, the multiple capacity intervals including a first type of capacity interval and a second type of capacity interval, the capacity in the first type of capacity interval is greater than or equal to the capacity average, and the capacity in the second type of capacity interval is less than the capacity average.

[0062] Exemplarily, assuming that the capacity average value calculated according to the capacity of each battery cell is recorded as mean, and the standard deviation is recorded as sigma, the distribution interval is divided with the capacity average value mean as the division center, and the standard deviation sigma as the length of the capacity interval, and the multiple capacity intervals obtained can be expressed as: mean±n*sigma, where n is greater than or equal to 1. Assuming that n is 3, 6 capacity intervals can be obtained, namely: [mean-3sigma, mean-2sigma), [mean-2sigma, mean-sigma), [mean-sigma, mean), [mean, mean+sigma), [mean+sigma, mean+2sigma), [mean+2sigma, mean+3sigma]. It can be seen from these 6 capacity intervals that these 6 capacity intervals are divided with mean as the dividing center, and the interval length of each capacity interval is sigma. The capacity in the first 3 capacity intervals of these 6 capacity intervals is less than mean, that is, the first 3 capacity intervals belong to the second type of capacity intervals mentioned above, and the capacity in the last 3 capacity intervals of these 6 capacity intervals is greater than or equal to mean, that is, the last 3 capacity intervals belong to the first type of capacity intervals mentioned above. It should be noted that in this example, n is taken as 3 for the convenience of understanding, and it is not limited to this in the specific implementation. Those skilled in the art can choose the size of n according to actual needs. The larger n is, the more capacity intervals are divided, and the corresponding number of selected battery cells to be tested may be more.

[0063] In this embodiment, considering that the capacity of battery cells in normal production is normally distributed due to process fluctuations, the distribution interval is divided with the capacity average value of each battery cell in the same batch as the division center and the capacity standard deviation of each battery cell in the same batch as the division interval to obtain multiple capacity intervals, which is conducive to meeting the characteristic that the capacity is normally distributed during battery cell production, and the capacity in the first type of capacity interval among the multiple capacity intervals is greater than or equal to the capacity average value, and the capacity in the second type of capacity interval is less than the capacity average value, that is, the multiple capacity intervals are distributed before and after the capacity average value, so that the battery cells to be tested finally selected can include both battery cells to be tested with a capacity greater than the capacity average value and battery cells to be tested with a capacity less than the capacity average value, which is conducive to making the multiple points for constructing a linear relationship reasonably and evenly distributed, so that the constructed linear relationship is more reasonable and accurate, and further makes the NP ratio of the candidate battery cells calculated in combination with the linear relationship more accurate, so that the battery cell grouping based on the NP ratio is ultimately more reasonable and accurate, and the dynamic consistency is better.

[0064] In an exemplary embodiment, the above-mentioned method of selecting multiple battery cells in each battery cell as multiple battery cells to be tested according to multiple capacity intervals includes: for each capacity interval, selecting a target capacity within the capacity interval; and selecting at least two battery cells with a capacity of the target capacity in each battery cell as battery cells to be tested whose capacities are distributed in the capacity interval.

[0065] Exemplarily, the target capacity selected in each capacity interval can be any capacity in the capacity interval, and the capacity difference between the target capacities of two adjacent capacity intervals can be the same, so that the capacity of the battery cell to be tested can be regularly and evenly distributed. Assume that the multiple capacity intervals include those mentioned in the above example: [mean-3sigma, mean-2sigma), [mean-2sigma, mean-sigma), [mean-sigma, mean), [mean, mean+sigma), [mean+sigma, mean+2sigma), [mean+2sigma, mean+3sigma], then for the capacity interval [mean-3sigma, mean-2sigma), the target capacity R1 (mean-3sigma≤R1<mean-2sigma) can be determined first in [mean-3sigma, mean-2sigma), and then at least two battery cells with a capacity of the target capacity R1 are selected from each battery cell as the battery cells to be tested whose capacity is distributed in the capacity interval [mean-3sigma, mean-2sigma). For the capacity interval [mean+2sigma, mean+3sigma], the target capacity R2 (mean+2sigma≤R2≤mean+3sigma) can be first determined within [mean+2sigma, mean+3sigma], and then at least two cells with a capacity of the target capacity R2 are selected from each cell as the cells to be tested whose capacities are distributed in the capacity interval [mean+2sigma, mean+3sigma]. The method of selecting cells to be tested whose capacities are distributed in other capacity intervals is similar to the above method, and will not be repeated here to avoid repetition.

[0066] In this embodiment, it is equivalent to selecting at least two battery cells with different capacities in each capacity interval as the battery cells to be tested, which is helpful to avoid test errors.

[0067] In an exemplary embodiment, for each capacity interval, selecting a target capacity within the capacity interval includes: for each capacity interval, using a middle capacity of the capacity interval as a target capacity selected within each capacity interval.

[0068] For example, for the capacity interval [mean-3sigma, mean-2sigma), the middle capacity of the capacity interval is: mean-3sigma+2 / sigma=mean-5 / 2sigma, that is, the above R1=mean-5 / 2sigma. For the capacity interval [mean+2sigma, mean+3sigma], the middle capacity of the capacity interval is: mean+2sigma+2 / sigma=mean+5 / 2sigma, that is, the above R2=mean+5 / 2sigma.

[0069] Exemplarily, assuming that mean is 2500, sigma is 50, and n is 3, the 6 capacity intervals obtained by division can be expressed as: [2350, 2400), [2400, 2450), [2450, 2500), [2500, 2550), [2550, 2600), [2600, 2650]. In this embodiment, 2 battery cells can be selected in each of the above capacity intervals as the battery cells to be tested. For example, the battery cells selected in the above 6 capacity intervals are as follows: 2 battery cells with a capacity of 2375mAh, 2 battery cells with a capacity of 2425mAh, 2 battery cells with a capacity of 2475mAh, 2 battery cells with a capacity of 2525mAh, 2 battery cells with a capacity of 2575mAh, and 2 battery cells with a capacity of 2625mAh, that is, a total of 12 battery cells are selected in the 6 capacity intervals as the battery cells to be tested.

[0070] In this embodiment, for each capacity interval, the middle capacity of the capacity interval is used as the target capacity selected in each capacity interval, so that the NP ratios of multiple cells to be tested can be evenly distributed, which is conducive to constructing a more accurate linear relationship.

[0071] In step 1031, charge and discharge tests can be performed on multiple cells to be tested on the test equipment to determine the voltage when the state of charge (SOC) of each cell to be tested reaches the target SOC; wherein the target SOC represents the end of the reaction of the active material of the cell to be tested, and the target SOC is usually in the low SOC region at the end of discharge. Different active materials may correspond to different target SOCs, and the target SOCs corresponding to different active materials can be obtained through charge and discharge tests. For example, when the active material is lithium cobalt oxide, the corresponding target SOC can be 10%. The target SOC is generally at a low SOC, such as between 5% and 15%. The specific position is related to the doping and coating of the cathode material, and the discharge differential curve characteristics are all upward protrusions.

[0072] In an exemplary embodiment, the above-mentioned charging and discharging tests are performed on the plurality of cells to be tested respectively, and a method for determining the voltage when the SOC of each cell to be tested reaches the target SOC may include the following S1-S3:

[0073] S1: For each battery cell to be tested, a preset charging current and charging voltage are used to perform a charging test on the battery cell to be tested until the voltage of the battery cell to be tested reaches the full charging voltage.

[0074] Among them, the charging current and charging voltage can be set according to actual needs. In a specific implementation, the preset charging current can be between 0.05C and 0.5C, and the charging voltage can be between 3V and 4.45V. In this embodiment, the charging current can be selected as 0.5C, and the charging voltage can be selected as 0.05C. Thus, for each battery cell to be tested, 0.5C constant current and 0.05C constant voltage can be used to charge to the full charge voltage of the battery cell to be tested, and the full charge voltage can be, for example, 4.45V.

[0075] S2: After the voltage of the battery cell to be tested reaches the full charge voltage, a preset discharge rate is used to perform a discharge test on the battery cell to be tested until the voltage of the battery cell to be tested reaches a cut-off voltage, so as to obtain a discharge differential curve of the battery cell to be tested.

[0076] Among them, the discharge rate can be set according to actual needs, for example, the preset discharge rate is less than or equal to 0.5C. In this embodiment, the preset discharge rate can be selected as 0.5C, that is, after the voltage of the battery cell to be tested reaches the full charge voltage, the battery cell to be tested is discharged at a discharge rate of 0.5C until the voltage of the battery cell to be tested reaches the cut-off voltage, and the cut-off voltage can be 3V, for example. The test data of this charge and discharge test is obtained, and the test data may include: capacity data and voltage data, so that a curve of the battery cell voltage-battery cell capacity of the battery cell to be tested can be constructed according to the test data, and the curve is subjected to first-order differential processing to obtain the discharge differential curve of the battery cell to be tested, that is, the dv / dq curve.

[0077] In this embodiment, a discharge rate less than or equal to 0.5C is used to perform constant current full discharge on the battery cell to be tested. A smaller discharge rate will obtain more detailed reaction phase change peaks when using differential processing, which is convenient for accurately determining the target SOC.

[0078] S3: Determine the voltage when the SOC of the battery cell to be tested reaches the target SOC according to the discharge differential curve.

[0079] For example, assuming that the cathode material of the battery cell to be tested is lithium cobalt oxide, the schematic diagram of the dv / dq curve of the battery cell to be tested can be referred to Figure 3 , Figure 3DOD is the depth of discharge (Depth of Discharge, DOD), which is a measure of the degree of discharge and reflects the proportion of active materials participating in the reaction, SOC = 1-DOD. Figure 3 It can be seen that: when the discharge of the battery cell to be tested is completed, the SOC of the last phase change characteristic of the cathode lithium cobalt oxide is 10%, that is, the target SOC is 10%. In other words, the SOC of 10% is the end peak of the reaction of the cathode lithium cobalt oxide. When other cathode materials are used, the SOC state of the reaction end peak is not necessarily 10%. In theory, the SOC of the last phase change peak of the cathode should be selected on the dv / dq curve, which is the SOC corresponding to the reaction end peak of this material. After determining that the target SOC is 10%, the voltage when the SOC of the battery cell to be tested reaches 10% can be recorded, recorded as V-10%SOC.

[0080] In step 1014, each cell to be tested after the charge and discharge test is completed can be disassembled, and the NP ratio of the multiple cells to be tested after disassembly can be calculated. Specifically, for each of the above-mentioned cells to be tested after disassembly, the mass of the anode electrode sheet obtained after disassembly is measured, the mass of the current collector of the anode electrode sheet, the ratio of the active material of the anode electrode sheet, and the gram capacity of the anode electrode sheet are determined, and the discharge capacity of the cell to be tested during the charge and discharge test is measured, and the NP ratio of the cell to be tested after disassembly is calculated based on the mass of the anode electrode sheet, the mass of the current collector, the ratio of the active material, the gram capacity of the anode electrode sheet, and the discharge capacity.

[0081] Exemplarily, after the battery cell to be tested is disassembled, the anode electrode piece can be dried in an oven at a preset temperature for a preset time, and then the anode electrode piece mass ma of the battery cell to be tested can be weighed. The preset temperature can be between 45-80°C, and the preset time can be 4-6h. Then, the current collector mass ma' of the anode electrode piece, the proportion loading of the active material of the anode electrode piece, and the gram capacity k of the anode electrode piece can be determined when manufacturing the battery cell to be tested. The current collector mass ma' can be obtained by multiplying the density of the current collector by the volume, and the proportion loading of the active material may be between 95% and 99% in a specific implementation, and the gram capacity k can be 360mAh / g, for example. Finally, the NP ratio of the battery cell to be tested after disassembly can be calculated based on the mass ma of the anode electrode piece, the mass ma' of the current collector, the proportion loading of the active material, the gram capacity k of the anode electrode piece, and the discharge capacity Q of the battery cell to be tested during the charge and discharge test. For example, the NP ratio can be calculated by the following formula: NP ratio = k(mAh / g)*(ma-ma')*loading / Q.

[0082] In an exemplary embodiment, the NP ratio (N / P) can also be calculated using the following formula: N / P = negative electrode active material gram capacity × negative electrode surface density × negative electrode active material content ratio ÷ (positive electrode active material gram capacity × positive electrode surface density × positive electrode active material content ratio).

[0083] In step 1015 , a linear relationship between the NP ratio and the voltage may be constructed according to the NP ratios of the plurality of cells to be tested and the voltage when the SOC of each cell to be tested reaches the target SOC.

[0084] For example, the NP ratio of a cell to be tested and the voltage of the cell to be tested when the SOC reaches the target SOC can be used as the horizontal and vertical axis coordinates of a point respectively. Thus, multiple cells to be tested will correspond to the horizontal and vertical axis coordinates of multiple points. According to the horizontal and vertical axis coordinates of the multiple points, a linear relationship between the NP ratio and the voltage is constructed.

[0085] Exemplarily, assuming that at least two cells to be tested are selected in a capacity interval, the mean NP ratio of the at least two cells to be tested and the average voltage when the SOC of the at least two cells to be tested reaches the target SOC can be used as the horizontal and vertical axis coordinates of the fitting point corresponding to the capacity interval, the mean NP ratio is used as the vertical axis coordinate of the fitting point, and the average voltage is used as the horizontal axis coordinate of the fitting point. One capacity interval corresponds to the horizontal and vertical axis coordinates of one fitting point, and multiple capacity intervals correspond to the horizontal and vertical axis coordinates of multiple fitting points. According to the horizontal and vertical axis coordinates of the multiple fitting points, a linear relationship between the NP ratio and the voltage is constructed.

[0086] For example, assuming that there are 6 capacity intervals, 2 cells to be tested are selected in each capacity interval, and the target SOC is 10%, the discharge capacity Q, V-10% SOC (i.e., the voltage when the SOC reaches 10% SOC), anode plate mass, NP ratio, V-10% SOC mean, i.e., the average value of the above-mentioned voltage, and the mean value of the NP ratio of the cells to be tested selected in the 6 capacity intervals can be shown in Table 1 below:

[0087] Table 1

[0088]

[0089] From Table 2, we can see that the horizontal and vertical coordinates of the six fitting points corresponding to the six capacity intervals are (3.657, 1.051), (3.712, 1.042), (3.731, 1.037), (3.787, 1.028), (3.818, 1.024), and (3.868, 1.019). The linear relationship between the NP ratio and the voltage is constructed by linear fitting these six fitting points. The schematic diagram of the linear relationship can be found in Figure 4 .pass Figure 4It can be seen that the expression of the linear relationship between the NP ratio and the voltage is: y = -0.1553x + 1.6179, where y is the NP ratio and x is V-10% SOC. Figure 4 Medium R 2 =0.9843 indicates that there is a good correlation between the voltage value x and the NP ratio, and the reliability of converting the voltage value into the NP ratio of the battery cell is high, and the calculation deviation is small.

[0090] In step 1016, a test device may be used to perform a discharge test on each candidate cell, and when each candidate cell is discharged until the SOC reaches the target SOC, the voltage at this time is recorded. Each candidate cell may be: all cells or part of cells in the same batch except for the multiple cells to be tested. The discharge strategy used in the discharge test on each candidate cell may be the same as the discharge strategy used in the discharge test on the cell to be tested.

[0091] In step 1017 , the voltage of each candidate battery cell when the SOC is discharged to reach the target SOC may be used as a dependent variable x and substituted into the expression of the above linear relationship to calculate the NP ratio of each candidate battery cell.

[0092] In step 102, the NP ratio deviation between the candidate cells may be calculated according to the NP ratio of each candidate cell, that is, the difference in the NP ratio between any two candidate cells may be calculated.

[0093] In step 103, candidate cells with NP ratio deviations less than a preset deviation are grouped together, that is, the NP ratio deviations between candidate cells in the same group are less than the preset deviation. The preset deviation can be set according to actual needs, for example, can be set to ±0.5%.

[0094] For example, after obtaining the NP ratio of each candidate battery cell, single batteries with different NP ratios can be selected for cycle performance testing. Batteries with different NP ratios will show different cycle performance. It is generally believed that the battery cell cycle performance is the same or very small when the NP ratio deviation is within ±0.5%. For different types of batteries, an NP ratio range α can also be determined by experimental testing. If the NP ratio deviation between the candidate batteries is ≤α, it is considered that the consistency is good and can be grouped. That is to say, in this embodiment, the preset deviation of the candidate battery cell suitable for this type can be obtained through experimental testing to better perform consistency grouping.

[0095] To facilitate understanding of the embodiments of the present application, the method for cell screening in the embodiments of the present application is described below with a specific example:

[0096] 1. Assume that the battery cells in the same batch are a certain type of lithium cobalt battery cells. There are 1000 battery cells in total. The capacity of 1000 battery cells is tested using capacity classification equipment. The test results show that the mean value of the capacity is 2500 and the sigma value is 50. According to the mean and sigma, the battery cells can be divided into 6 capacity intervals: 2350-2400, 2400-2450, 2450-2500, 2500-2550, 2550-2600 and 2600-2650.

[0097] 2. Select 2 battery cells in each capacity range. The capacities of the 2 battery cells selected in each capacity range are: 2 2375mAh, 2 2425mAh, 2 2475mAh, 2 2525mAh, 2 2575mAh, and 2 2625mAh. A total of 12 battery cells are selected as the battery cells to be tested.

[0098] 3. The 12 cells to be tested are first fully charged to 4.45V using a constant current of 0.5C and a constant voltage of 0.05C, and then discharged to 3V at a discharge rate of 0.5C. The discharge capacity within the normal voltage range is recorded as Q, which can be directly read from the capacity test equipment. The test statistical results are shown in Table 1 above.

[0099] 4. Obtain the dv / dq curve based on the test data in step 3, such as Figure 3 As shown. Combined Figure 3 The final phase change feature of the cathode lithium cobalt oxide is determined to be at 10% SOC, which is generally at 5%-15% SOC and presents an upward protrusion shape. The voltage value at 10% SOC is recorded, and the recording results can be seen in Table 1.

[0100] 5. Disassemble 12 cells and calculate the actual NP ratio of the 12 cells. The statistical results of the NP ratio are shown in Table 1 above. After disassembly, use a 60°C oven to dry the anode pole piece for 4 hours, weigh the mass of the anode pole piece of each cell, the mass of the bare current collector during cell manufacturing is 6g, the anode gram capacity uses the designed gram capacity of 360mAh / g, and the anode pole piece is loaded at 97%. The actual NP ratio of the cell = 360mAh / g*(anode pole piece mass-bare current collector mass)*anode pole piece loading / discharge capacity Q.

[0101] 6. The average values ​​of the V-10% SOC in step 4 and the measured NP ratio in step 5 are shown in Table 1. A linear relationship equation of univariate regression is constructed, and the linear relationship between the NP ratio and the voltage value is obtained as follows:

[0102] y(NP ratio)=-0.1533x(V-10%SOC)+1.6179

[0103] 7. For the batch cells of the same batch, i.e., the candidate cells mentioned above, use the test equipment to discharge at a rate of 0.5C and adopt the same discharge process as step 3 to 10% SOC to record V-10% SOC, and substitute it into the calculation formula in step 6 to obtain the NP ratio of the batch cells. The NP ratio of each candidate cell can be calculated without disassembling the candidate cells.

[0104] 8. Selecting single cells with the upper and lower limits of NP ratio for 0.5C charge and discharge cycles confirms that NP ratio has a significant impact on the cycle performance of single cells, see Figure 5 , Figure 5 The horizontal axis represents the capacity retention rate, and the vertical axis represents the number of cycles. Figure 5 It can be seen that the capacity retention rate of two battery cells with a NP ratio difference of 0.05 differs by ~5%, which shows that the NP ratio has a significant impact on the cycle performance of the battery cell. Figure 5 CB=1.0625, that is, NP ratio=1.0625, CB=1.0125, that is, NP ratio=1.0125.

[0105] It should be noted that the present embodiment takes lithium cobalt batteries as an example for the sake of convenience. In a specific implementation, the battery cell screening method can be applied to battery cells of various chemical systems, such as battery cells of ternary, lithium iron phosphate and other chemical systems. The present embodiment does not specifically limit the chemical system of the battery cells.

[0106] In this embodiment, it is believed that there is no significant difference in the performance of single cells with NP ratios within the range of ±0.5%, which can be verified in the following way: take NP ratio = 1.050, NP ratio = 1.060, two cells are connected in series to form module A, and the NP ratio deviation value of the two cells in module A is 0.01; take NP ratio = 1.050, NP ratio = 1.053, two cells are connected in series to form module B, and the NP ratio deviation value of the two cells in module B is 0.003. Module A and module B are subjected to cycle life tests at a temperature of 45°. The cycle test process is 0.5C constant current charging to 8.9V, constant voltage to 0.2C; after standing for 10 minutes, discharge at a discharge rate of 0.5C to 6V, and cycle test for 400 cycles. Passed Figure 6 It can be seen that the capacity retention rate of module A (82%) is much lower than that of module B (88%), and the capacity retention rate of module B has been significantly improved. It can be seen that there is no significant difference in the performance of single cells within the range of NP ratio of ±0.5%. Dividing single cells within the range of NP ratio of ±0.5% into a group makes the dynamic consistency of the grouped module cells better and the cycle performance is also better.

[0107] Figure 7 It is a structural schematic diagram of a battery cell screening device provided in an embodiment of the present application.

[0108] For example, Figure 7 As shown, the device includes: an NP ratio determination module 701, used to determine the NP ratio of each candidate battery cell in each battery cell of the same batch; an NP ratio deviation calculation module 702, used to calculate the NP ratio deviation between the above-mentioned candidate battery cells according to the NP ratio of the above-mentioned candidate battery cells; a grouping module 703, used to group the above-mentioned candidate battery cells according to the above-mentioned NP ratio deviation; wherein the NP ratio deviation between the candidate battery cells in the same group is less than the preset deviation.

[0109] In a possible implementation, the NP ratio determination module 701 is specifically used to: select multiple cells from the above-mentioned cells as multiple cells to be tested according to the capacity of each of the above-mentioned cells; wherein the capacity of the above-mentioned cells to be tested includes multiple different capacities; perform charge and discharge tests on the above-mentioned cells to be tested respectively to determine the voltage when the SOC of each of the above-mentioned cells to be tested reaches the target SOC; wherein the above-mentioned target SOC represents the end of the reaction of the active materials of the above-mentioned cells to be tested; disassemble the above-mentioned cells to be tested and calculate the NP ratio of the above-mentioned cells to be tested after disassembly; construct a linear relationship between the NP ratio and the voltage according to the NP ratio of the above-mentioned cells to be tested and the voltage when the SOC of each of the above-mentioned cells to be tested reaches the target SOC; perform a discharge test on the above-mentioned candidate cells to determine the voltage when the above-mentioned candidate cells are discharged to the SOC reaching the above-mentioned target SOC; determine the NP ratio of the above-mentioned candidate cells according to the voltage when the above-mentioned candidate cells are discharged to the SOC reaching the above-mentioned target SOC and the above-mentioned linear relationship.

[0110] In one possible implementation, the NP ratio determination module 701 is specifically used to: determine the distribution interval of the capacity of each of the above-mentioned battery cells; divide the above-mentioned distribution interval to obtain multiple capacity intervals; according to the above-mentioned multiple capacity intervals, select multiple battery cells from each of the above-mentioned battery cells as multiple battery cells to be tested; wherein the capacities of the above-mentioned multiple battery cells to be tested are distributed in the above-mentioned multiple capacity intervals.

[0111] In a possible implementation, the NP ratio determination module 701 is specifically used to: calculate the capacity average and standard deviation according to the capacity of each of the above-mentioned battery cells; divide the above-mentioned distribution interval with the above-mentioned capacity average as the division center and the above-mentioned standard deviation as the length of the capacity interval to obtain multiple capacity intervals; wherein the above-mentioned multiple capacity intervals include a first-category capacity interval and a second-category capacity interval, the capacity within the above-mentioned first-category capacity interval is greater than or equal to the above-mentioned capacity average, and the capacity within the above-mentioned second-category capacity interval is less than the above-mentioned capacity average.

[0112] In a possible implementation, the NP ratio determination module 701 is specifically used to: for each of the above-mentioned capacity intervals, select a target capacity within the above-mentioned capacity interval; select at least two battery cells with a capacity of the above-mentioned target capacity from the above-mentioned battery cells as the battery cells to be tested whose capacities are distributed in the above-mentioned capacity intervals.

[0113] In a possible implementation, the NP ratio determination module 701 is specifically configured to: for each of the capacity intervals, use the middle capacity of the capacity interval as the target capacity selected in each of the capacity intervals.

[0114] In one possible implementation, the NP ratio determination module 701 is specifically used to: for each of the above-mentioned battery cells to be tested, use a preset charging current and charging voltage to perform a charging test on the above-mentioned battery cell to be tested until the voltage of the above-mentioned battery cell to be tested reaches the full charging voltage; after the voltage of the above-mentioned battery cell to be tested reaches the full charging voltage, use a preset discharge rate to perform a discharge test on the above-mentioned battery cell to be tested until the voltage of the above-mentioned battery cell to be tested reaches the cut-off voltage, so as to obtain the discharge differential curve of the above-mentioned battery cell to be tested; and determine the voltage when the SOC of the above-mentioned battery cell to be tested reaches the target SOC according to the above-mentioned discharge differential curve.

[0115] In a possible implementation, the preset discharge rate is less than or equal to 0.5C, the preset charging current is between 0.05C and 0.5C, and the preset charging voltage is between 3V and 4.45V.

[0116] Figure 8 It is a structural schematic diagram of an electronic device provided in an embodiment of the present application.

[0117] For example, Figure 8 As shown, the electronic device includes: a memory 801 and a processor 802, wherein the memory 801 stores executable program code, and the processor 802 is used to call and execute the executable program code to perform a method for cell screening.

[0118] In this embodiment, the electronic device can be divided into functional modules according to the above method example. For example, each functional module can be corresponded to, or two or more functions can be integrated into one processing module. The above integrated module can be implemented in the form of hardware. It should be noted that the division of modules in this embodiment is schematic and is only a logical function division. There may be other division methods in actual implementation.

[0119] In the case of dividing each functional module according to each function, the electronic device may include: an NP ratio determination module, an NP ratio deviation calculation module, a grouping module, etc. It should be noted that all relevant contents of each step involved in the above method embodiment can be referred to the functional description of the corresponding functional module, which will not be repeated here.

[0120] The electronic device provided in this embodiment is used to execute the above-mentioned method for screening battery cells, and thus can achieve the same effect as the above-mentioned implementation method.

[0121] In the case of an integrated unit, the electronic device may include a processing module and a storage module. The processing module may be used to control and manage the actions of the electronic device. The storage module may be used to support the electronic device in executing mutual program codes and data.

[0122] The processing module may be a processor or a controller, which may implement or execute various exemplary logic blocks, modules and circuits represented in combination with the contents disclosed in this application. The processor may also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of digital signal processing (DSP) and a microprocessor, etc. The storage module may be a memory.

[0123] This embodiment also provides a computer-readable storage medium, in which a computer program code is stored. When the computer program code is run on a computer, the computer executes the above-mentioned related method steps to implement a method for cell screening in the above-mentioned embodiment.

[0124] This embodiment further provides a computer program product. When the computer program product is run on a computer, the computer is enabled to execute the above-mentioned related steps to implement a method for cell screening in the above-mentioned embodiment.

[0125] In addition, the electronic device provided in the embodiments of the present application may specifically be a chip, a component or a module, and the electronic device may include a connected processor and a memory; wherein the memory is used to store instructions, and when the electronic device is running, the processor may call and execute instructions so that the chip executes a method for cell screening in the above-mentioned embodiments.

[0126] Among them, the electronic device, computer-readable storage medium, computer program product or chip provided in this embodiment are all used to execute the corresponding methods provided above. Therefore, the beneficial effects that can be achieved can refer to the beneficial effects in the corresponding methods provided above and will not be repeated here.

[0127] Through the description of the above implementation methods, technical personnel in the relevant field can understand that for the convenience and simplicity of description, only the division of the above-mentioned functional modules is used as an example. In actual applications, the above-mentioned functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above.

[0128] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic, for example, the division of modules or units is only a logical function division, and there may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another device, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0129] The above contents are only specific implementation methods of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for screening battery cells, characterized in that: The method comprises the steps of: Step 101: determining the ratio of the anode capacity to the cathode capacity of each candidate battery cell in each battery cell of the same batch; Step 102: calculating the deviation of the ratio of the anode capacity to the cathode capacity between the candidate cells according to the ratio of the anode capacity to the cathode capacity of the candidate cells; Step 103: grouping the candidate cells according to the ratio deviation of the anode capacity to the cathode capacity; wherein the ratio deviation of the anode capacity to the cathode capacity between the candidate cells in the same group is less than a preset deviation.

2. The method according to claim 1, characterized in that The step 101 comprises: Obtaining the capacity of each battery cell in the same batch; According to the capacity of each battery cell, selecting a plurality of battery cells with different capacities from each battery cell as a plurality of battery cells to be tested; Performing charge and discharge tests on the multiple cells to be tested respectively, and determining the voltage when the charge state of each cell to be tested reaches a target charge state; wherein the target charge state indicates that the reaction of the active material of the cell to be tested has ended; Disassembling the plurality of battery cells to be tested, and calculating a ratio of anode capacity to cathode capacity of the plurality of battery cells to be tested after disassembly; Constructing a linear relationship between the ratio of the anode capacity to the cathode capacity and the voltage according to the ratio of the anode capacity to the cathode capacity of the plurality of cells to be tested and the voltage when the charge state of each cell to be tested reaches the target charge state; Performing a discharge test on each candidate battery cell to determine the voltage of each candidate battery cell when the charge state reaches the target charge state; The ratio of the anode capacity to the cathode capacity of each candidate battery cell is determined according to the voltage of each candidate battery cell when the charge state reaches the target charge state and the linear relationship.

3. The method according to claim 2, characterized in that The step of selecting a plurality of cells with different capacities from the cells as the plurality of cells to be tested according to the capacities of the cells comprises: Determining a distribution range of the capacity of each battery cell; Dividing the distribution interval to obtain a plurality of capacity intervals; According to the multiple capacity intervals, multiple cells are selected from the multiple cells as multiple cells to be tested; wherein the capacities of the multiple cells to be tested are distributed in the multiple capacity intervals.

4. The method according to claim 3, characterized in that: The distribution interval is divided to obtain a plurality of capacity intervals, including: Calculate the capacity average and standard deviation according to the capacity of each battery cell; The distribution interval is divided with the capacity average value as the division center and the standard deviation as the length of the capacity interval to obtain multiple capacity intervals; wherein the multiple capacity intervals include a first type of capacity interval and a second type of capacity interval, the capacity in the first type of capacity interval is greater than or equal to the capacity average value, and the capacity in the second type of capacity interval is less than the capacity average value.

5. The method according to claim 3, characterized in that: The selecting, according to the multiple capacity intervals, multiple cells from each of the cells as multiple cells to be tested comprises: For each of the capacity intervals, selecting a target capacity within the capacity interval; At least two battery cells having capacities equal to the target capacities are selected from the battery cells as the battery cells to be tested whose capacities are distributed in the capacity interval.

6. The method according to claim 5, characterized in that For each of the capacity intervals, selecting a target capacity within the capacity interval includes: For each of the capacity intervals, the middle capacity of the capacity interval is used as the target capacity selected in each of the capacity intervals.

7. The method according to any one of claims 2 to 6, characterized in that: The step of performing charge and discharge tests on the plurality of cells to be tested respectively to determine the voltage when the charge state of each cell to be tested reaches a target charge state includes: For each of the battery cells to be tested, a preset charging current and charging voltage are used to perform a charging test on the battery cell to be tested until the voltage of the battery cell to be tested reaches a full charge voltage; After the voltage of the battery cell to be tested reaches the full charge voltage, a preset discharge rate is used to perform a discharge test on the battery cell to be tested until the voltage of the battery cell to be tested reaches a cut-off voltage, so as to obtain a discharge differential curve of the battery cell to be tested; Determining the voltage when the charge state of the battery cell to be tested reaches the target charge state according to the discharge differential curve; Wherein, the preset discharge rate is less than or equal to 0.5C, the preset charging current is between 0.05C and 0.5C, and the preset charging voltage is between 3V and 4.45V.

8. A device for screening battery cells, characterized in that: The device comprises: A module for determining the ratio of anode capacity to cathode capacity, used to determine the ratio of anode capacity to cathode capacity of each candidate battery cell in each battery cell of the same batch; A module for calculating the ratio deviation of the anode capacity to the cathode capacity, for calculating the ratio deviation of the anode capacity to the cathode capacity between the candidate cells according to the ratio of the anode capacity to the cathode capacity of the candidate cells; A grouping module is used to group the candidate cells according to the ratio deviation of the anode capacity to the cathode capacity; wherein the ratio deviation of the anode capacity to the cathode capacity between the candidate cells in the same group is less than a preset deviation.

9. An electronic device, characterized in that: The electronic device comprises: A memory for storing executable program codes; A processor, configured to call and run the executable program code from the memory, so that the electronic device executes the method according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed, the method according to any one of claims 1 to 7 is implemented.

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