Screening method and device of lithium ion battery cells, electronic equipment and storage medium

Abstract

The invention relates to the technical field of batteries, in particular to a lithium ion battery cell screening method and device, electronic equipment and a storage medium, and the method comprises the steps: obtaining the open-circuit voltage of each cell in a to-be-detected lithium ion battery at different temperatures and different placement durations; calculating the self-discharge rate of each battery cell according to the open-circuit voltage, and preliminarily screening all the battery cells according to the self-discharge rates to obtain battery cells with qualified self-discharge performance and abnormal battery cells; and performing secondary screening on the abnormal cells according to the cells with qualified self-discharge performance and the open-circuit voltage of the abnormal cells to obtain the cells with qualified self-discharge performance in the abnormal cells. Therefore, the problems that omission or over-killing of the battery cells is easily caused, and the self-discharge screening accuracy is low in the prior art are solved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a method, device, electronic device and storage medium for screening lithium-ion battery cells. Background Art

[0002] Lithium-ion batteries are widely used in the digital and power energy industries due to their high energy density, long sequential life and no memory effect. When a lithium-ion battery is in an open circuit state, the phenomenon of spontaneous capacity loss is called the self-discharge of the lithium-ion battery, which can also be called the charge retention capacity of the lithium-ion battery. The K value is a quantitative description of the rate of battery voltage drop, which is calculated by dividing the difference in the open circuit voltage of two tests by the time interval between the two voltage tests. If the K value is too large, it means that the battery storage voltage drops too fast. If a battery with large self-discharge is shipped to a customer, the voltage consistency of the battery with large self-discharge will become increasingly poor over time. According to the barrel principle, if a battery with abnormal self-discharge is combined with a normal battery to form a module, the inconsistency of the self-discharge of each battery will lead to a reduction in the life of the lithium battery pack and a rapid capacity decay, thus affecting the use of the battery. How to achieve accurate self-discharge testing is a topic that the lithium-ion battery industry is considering.

[0003] The relevant technology mainly adopts the K value screening method, which is as follows: battery after capacity division → storage for a period of time T1 → test voltage OCV1 → storage for a period of time T2 → test voltage OCV2, and the ratio of the difference between OCV1 and OCV2 and the difference between the two storage times is the K value. This method can quickly calculate the K value, but since the storage time, storage temperature, test temperature, etc. will all fluctuate in large-scale production, the accuracy of the K value test will be affected, which will lead to missed or over-screening of the battery cell self-discharge, resulting in the consistency of the client battery cells often not being guaranteed. Summary of the invention

[0004] The present application provides a method, device, electronic device and storage medium for screening lithium-ion battery cells to solve the problems of the related technology easily causing missed or over-killing of cells and low self-discharge screening accuracy.

[0005] A first aspect of the present application provides a method for screening lithium-ion battery cells, comprising the following steps: obtaining the open circuit voltage of each cell in the lithium-ion battery to be tested at different temperatures and for different storage times; calculating the self-discharge rate of each cell according to the open circuit voltage, and performing a preliminary screening of all cells according to the self-discharge rate to obtain cells with qualified self-discharge performance and abnormal cells; performing a secondary screening of abnormal cells according to the open circuit voltage of cells with qualified self-discharge performance and abnormal cells, to obtain cells with qualified self-discharge performance among the abnormal cells.

[0006] Optionally, in one embodiment of the present application, a secondary screening is performed on abnormal cells based on the open circuit voltages of cells with qualified self-discharge performance and abnormal cells, including: calculating the average value of the open circuit voltages of cells with qualified self-discharge performance; and performing a secondary screening on abnormal cells based on the average value of the open circuit voltages and the open circuit voltages of abnormal cells.

[0007] Optionally, in one embodiment of the present application, the open circuit voltage includes first to third voltages, and the self-discharge rate of each battery cell is calculated based on the open circuit voltage, including: obtaining the measurement time of the second voltage and the third voltage respectively; calculating the time interval of the measurement time, and calculating the self-discharge rate of each battery cell based on the second voltage, the third voltage and the time interval.

[0008] Optionally, in one embodiment of the present application, all battery cells are preliminarily screened according to the self-discharge rate to obtain battery cells with qualified self-discharge performance and abnormal battery cells, including: calculating the average value of the self-discharge rate of all battery cells; and preliminarily screening all battery cells based on the average value of the self-discharge rate to obtain battery cells with qualified self-discharge performance and abnormal battery cells.

[0009] Optionally, in one embodiment of the present application, the open circuit voltage of each battery cell in the lithium-ion battery to be tested is obtained at different temperatures and different placement times, including: after dividing the capacity of each battery cell, charging each battery cell to a target SOC with a preset current; after placing the battery cell at a first preset temperature for a first preset time, measuring the first voltage of each battery cell; after measuring the first voltage, placing the battery cell at a second preset temperature for a second preset time and at the first preset temperature for a third preset time, measuring the second voltage of each battery cell; after measuring the second voltage, placing the battery cell at the first preset temperature for a fourth preset time, measuring the third voltage of each battery cell, wherein the second preset temperature is higher than the first preset temperature, the fourth preset time is greater than the second preset time, and the second preset time is greater than the first preset time.

[0010] Optionally, in one embodiment of the present application, before performing secondary screening on abnormal battery cells based on the open circuit voltages of battery cells with qualified self-discharge performance and abnormal battery cells, it also includes: after storing the battery cells with qualified self-discharge performance and the abnormal battery cells at a fourth preset temperature for a preset number of days, re-measuring the open circuit voltage of each battery cell with qualified self-discharge performance and the open circuit voltage of each abnormal battery cell.

[0011] Optionally, in one embodiment of the present application, the abnormal battery cells are screened for the second time based on the average value of the open circuit voltage and the open circuit voltage of the abnormal battery cells, including: if the open circuit voltage of the abnormal battery cell is greater than a first preset voltage, the abnormal battery cell is determined to be a battery cell with qualified self-discharge performance; if the open circuit voltage of the abnormal battery cell is greater than or equal to a second preset voltage and less than the first preset voltage, the abnormal battery cell is determined to be a second-level battery cell; if the open circuit voltage of the abnormal battery cell is less than the second preset voltage, the abnormal battery cell is determined to be a battery cell with unqualified self-discharge performance, wherein the first preset voltage and the second preset voltage are both related to the average value of the open circuit voltage.

[0012] A second aspect of the present application provides a lithium-ion battery cell screening device, comprising: an acquisition module, used to obtain the open circuit voltage of each cell in the lithium-ion battery to be tested at different temperatures and different storage times; a first screening module, used to calculate the self-discharge rate of each cell according to the open circuit voltage, and perform a preliminary screening of all cells according to the self-discharge rate to obtain cells with qualified self-discharge performance and abnormal cells; a second screening module, used to perform a secondary screening of abnormal cells according to the open circuit voltage of cells with qualified self-discharge performance and abnormal cells, to obtain cells with qualified self-discharge performance among the abnormal cells.

[0013] Optionally, in one embodiment of the present application, the second screening module is further used to: calculate the average value of the open circuit voltage of the battery cells with qualified self-discharge performance; and perform secondary screening on the abnormal battery cells according to the average value of the open circuit voltage and the open circuit voltage of the abnormal battery cells.

[0014] Optionally, in one embodiment of the present application, the open circuit voltage includes first to third voltages, and the first screening module is further used to: obtain the measurement time of the second voltage and the third voltage respectively; calculate the time interval of the measurement time, and calculate the self-discharge rate of each battery cell based on the second voltage, the third voltage and the time interval.

[0015] Optionally, in one embodiment of the present application, the first screening module is further used to: calculate the average value of the self-discharge rates of all battery cells; and perform preliminary screening of all battery cells based on the average value of the self-discharge rates to obtain battery cells with qualified self-discharge performance and abnormal battery cells.

[0016] Optionally, in one embodiment of the present application, the acquisition module is further used to: after each battery cell is divided into different capacities, charge each battery cell to a target SOC with a preset current; after placing the battery cell at a first preset temperature for a first preset time, measure the first voltage of each battery cell; after measuring the first voltage, place the battery cell at a second preset temperature for a second preset time, and place the battery cell at the first preset temperature for a third preset time, and measure the second voltage of each battery cell; after measuring the second voltage, place the battery cell at the first preset temperature for a fourth preset time, and measure the third voltage of each battery cell, wherein the second preset temperature is higher than the first preset temperature, the fourth preset time is greater than the second preset time, and the second preset time is greater than the first preset time.

[0017] Optionally, in one embodiment of the present application, it also includes: a storage module, which is used to store the battery cells with qualified self-discharge performance and the abnormal battery cells at a fourth preset temperature for a preset number of days before performing a secondary screening on the abnormal battery cells based on the open circuit voltages of the battery cells with qualified self-discharge performance and the abnormal battery cells, and then re-measure the open circuit voltage of each battery cell with qualified self-discharge performance and the open circuit voltage of each abnormal battery cell.

[0018] Optionally, in one embodiment of the present application, the second screening module is further used for: if the open circuit voltage of the abnormal battery cell is greater than the first preset voltage, then the abnormal battery cell is determined to be a battery cell with qualified self-discharge performance; if the open circuit voltage of the abnormal battery cell is greater than or equal to the second preset voltage and less than the first preset voltage, then the abnormal battery cell is determined to be a second-level battery cell; if the open circuit voltage of the abnormal battery cell is less than the second preset voltage, then the abnormal battery cell is determined to be a battery cell with unqualified self-discharge performance, wherein the first preset voltage and the second preset voltage are both related to the average value of the open circuit voltage.

[0019] A third aspect of the present application provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to perform the lithium-ion battery screening method as described in the above embodiment.

[0020] A fourth aspect of the present application provides a computer-readable storage medium having a computer program or instructions stored thereon, and the computer program or instructions are executed by a processor to perform the lithium-ion battery screening method as described in the above embodiment.

[0021] Therefore, this application has at least the following beneficial effects:

[0022] The embodiment of the present application can perform a preliminary screening of the cells according to the self-discharge rate of the cells to obtain the primary abnormal cells and the cells with qualified self-discharge performance, and perform a secondary screening of the primary abnormal cells to obtain the cells with qualified self-discharge performance among the primary abnormal cells, so as to prevent the cells from being missed or over-killed by only the primary screening, improve the accuracy of the screening, and further improve the performance and reliability of the lithium-ion battery module or battery pack. Therefore, the technical problems that the related technology easily causes the cells to be missed or over-killed, and the self-discharge screening accuracy is low are solved.

[0023] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0025] Figure 1 A flow chart of a method for screening lithium-ion battery cells according to an embodiment of the present application;

[0026] Figure 2 A specific flow chart of a method for screening lithium-ion battery cells provided according to an embodiment of the present application;

[0027] Figure 3 This is an example diagram of a lithium-ion battery cell screening device provided according to an embodiment of the present application;

[0028] Figure 4 It is a schematic diagram of the structure of an electronic device provided according to an embodiment of the present application. DETAILED DESCRIPTION

[0029] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0030] The following describes the screening method, device, electronic device and storage medium of the lithium-ion battery cell of the embodiment of the present application with reference to the accompanying drawings. In view of the K value screening method mentioned in the above background technology, since the shelf time, shelf temperature, test temperature, etc. will fluctuate in large-scale production, affecting the accuracy of the K value test, and thus causing the problem of missed killing and over-killing in the self-discharge screening of the battery cell, the present application provides a lithium-ion battery screening method, in which the battery cell is preliminarily screened and judged according to the self-discharge rate of the battery cell to obtain the primary abnormal battery cell and the battery cell with qualified self-discharge performance, and the primary abnormal battery cell is screened for the second time to obtain the battery cell with qualified self-discharge performance in the primary abnormal battery cell, so as to prevent the missed killing and over-killing of the battery cell only after the primary screening, improve the accuracy of the screening, and then improve the performance and reliability of the lithium-ion battery module or battery pack. Thus, the problems that the related technology is prone to missed killing or over-killing of the battery cell, and the self-discharge screening accuracy is low are solved.

[0031] Specifically, Figure 1 A schematic diagram of a process for screening lithium-ion battery cells provided in an embodiment of the present application.

[0032] like Figure 1 As shown, the screening method of the lithium-ion battery cell comprises the following steps:

[0033] In step S101, the open circuit voltage of each cell in the lithium-ion battery to be tested is obtained at different temperatures and different storage times.

[0034] The open circuit voltage OCV includes first to third voltages, which respectively correspond to the open circuit voltages at different temperatures and different placement times.

[0035] It is understandable that the embodiments of the present application can measure the open circuit voltage of each cell in the lithium-ion battery at different temperatures and for different storage times, so as to subsequently screen the self-discharge performance of the lithium-ion battery.

[0036] In an embodiment of the present application, the open circuit voltage of each battery cell in the lithium-ion battery to be tested is obtained at different temperatures and different placement times, including: after each battery cell is divided into different capacities, each battery cell is charged to a target SOC with a preset current; after being placed at a first preset temperature for a first preset time, the first voltage of each battery cell is measured; after measuring the first voltage, after being placed at a second preset temperature for a second preset time, and at the first preset temperature for a third preset time, the second voltage of each battery cell is measured; after measuring the second voltage, after being placed at the first preset temperature for a fourth preset time, the third voltage of each battery cell is measured, wherein the second preset temperature is higher than the first preset temperature, the fourth preset time is longer than the second preset time, and the second preset time is longer than the first preset time.

[0037] Among them, the preset current, the first preset temperature, the first preset time, the second preset temperature, the second preset time, the third preset time, and the fourth preset time can all be calibrated according to specific circumstances, and no specific limitation is made to this.

[0038] It is understandable that the embodiments of the present application can be implemented by setting the preconditions for the initial screening of the lithium-ion battery cells, specifically:

[0039] 1. After each battery cell is divided into different capacities, each battery cell is charged to the target SOC with a preset current;

[0040] 2. After being placed at a first preset temperature for a first preset time, measuring a first voltage of each battery cell;

[0041] 3. After measuring the first voltage, after placing the battery at the second preset temperature for a second preset time, and placing the battery at the first preset temperature for a third preset time, measure the second voltage of each battery cell;

[0042] 4. After measuring the second voltage, place the battery at the first preset temperature for a fourth preset time and measure the third voltage of each battery cell, wherein the second preset temperature is higher than the first preset temperature, the fourth preset time is greater than the second preset time, and the second preset time is greater than the first preset time.

[0043] For example, after the cell is recharged after capacity division, the temperature is 0.1 0.3C low current charging to 3% of the cell charge state 35% SOC;

[0044] Incubate at 25±2℃ for 6-12h and record the first voltage OCV1;

[0045] Transfer the battery cells to a high temperature cabinet or room and place them at 45±2℃ for 24-48h;

[0046] Cool the battery cell to 25℃±2℃ for 12±1h and record the second voltage OCV2;

[0047] After the battery cell is placed at 25℃±2℃ for 48-96h, the third voltage OCV3 is recorded.

[0048] In step S102, the self-discharge rate of each battery cell is calculated according to the open circuit voltage, and all battery cells are preliminarily screened according to the self-discharge rate to obtain battery cells with qualified self-discharge performance and abnormal battery cells.

[0049] It can be understood that the embodiment of the present application can calculate the self-discharge rate K value of each battery cell according to the open circuit voltage, and perform preliminary screening of all battery cells based on the K value to obtain battery cells with qualified self-discharge performance and abnormal battery cells, thus completing the preliminary screening of all battery cells in the first stage.

[0050] In an embodiment of the present application, the open circuit voltage includes first to third voltages, and the self-discharge rate of each battery cell is calculated based on the open circuit voltage, including: obtaining the measurement time of the second voltage and the third voltage respectively; calculating the time interval of the measurement time, and calculating the self-discharge rate of each battery cell based on the second voltage, the third voltage and the time interval.

[0051] It can be understood that the embodiment of the present application can calculate the self-discharge rate of each battery cell according to the measurement time interval of the second voltage and the third voltage, the second voltage and the third voltage, that is, calculate the K value of each battery cell according to the voltage difference, wherein the specific calculation formula is:

[0052] K value = (OCV3 OCV2) / Δt, wherein OCV3 is the third voltage, OCV2 is the second voltage, and Δt is the interval between OCV2 and OCV3 in hours.

[0053] In an embodiment of the present application, all battery cells are preliminarily screened according to their self-discharge rates to obtain normal battery cells and abnormal battery cells, including: calculating the average value of the self-discharge rates of all battery cells; and preliminarily screening all battery cells based on the average value of the self-discharge rates to obtain battery cells with qualified self-discharge performance and abnormal battery cells.

[0054] It is understandable that the embodiment of the present application can perform a preliminary screening of all the cells based on the average value of the self-discharge rate of all the cells to obtain cells with qualified self-discharge performance and abnormal cells. The screening conditions can be Among them, σ is the standard deviation of the K value of all cells in this group.

[0055] For example, if the battery If the battery is abnormally discharged, it is a normal self-discharging battery.

[0056] In step S103, the abnormal cells are screened for a second time according to the open circuit voltages of the cells with qualified self-discharge performance and the abnormal cells, so as to obtain the cells with qualified self-discharge performance among the abnormal cells.

[0057] It can be understood that the embodiments of the present application can perform a secondary screening on the abnormal battery cells obtained in the primary screening to obtain battery cells with qualified self-discharge performance among the abnormal battery cells in the primary screening, so as to prevent the missed or over-killing of battery cells in the primary screening process and improve the accuracy of battery cell screening.

[0058] In an embodiment of the present application, before performing a secondary screening on abnormal battery cells based on the open circuit voltages of battery cells with qualified self-discharge performance and abnormal battery cells, it also includes: after storing the battery cells with qualified self-discharge performance and the abnormal battery cells at a fourth preset temperature for a preset number of days, re-measuring the open circuit voltage of each battery cell with qualified self-discharge performance and the open circuit voltage of each abnormal battery cell.

[0059] Among them, the fourth preset temperature and preset number of days can be set according to specific circumstances, and there is no specific limitation on this, such as the temperature of the test environment on that day, that is, normal temperature.

[0060] It can be understood that before calculating the average value of the open circuit voltages of the battery cells with qualified self-discharge performance, the embodiment of the present application stores the battery cells with qualified self-discharge performance and the abnormal battery cells at a fourth preset temperature for a preset number of days, and then remeasures the open circuit voltage of each battery cell with qualified self-discharge performance and the open circuit voltage of each abnormal battery cell to facilitate subsequent secondary screening of the abnormal battery cells.

[0061] In an embodiment of the present application, abnormal cells are secondary screened based on the open circuit voltages of cells with qualified self-discharge performance and abnormal cells, including: calculating the average value of the open circuit voltages of cells with qualified self-discharge performance; and secondary screening the abnormal cells based on the average value of the open circuit voltages and the open circuit voltages of the abnormal cells.

[0062] It can be understood that the embodiments of the present application can calculate the average value of the open circuit voltage OCV of the battery cells with qualified self-discharge performance, and compare the average value of the open circuit voltage with the open circuit voltage remeasured from the abnormal battery cells to achieve secondary screening of the abnormal battery cells.

[0063] In an embodiment of the present application, abnormal cells are screened for a second time based on the average value of the open circuit voltage and the open circuit voltage of the abnormal cells, including: if the open circuit voltage of the abnormal cell is greater than a first preset voltage, the abnormal cell is determined to be a cell with qualified self-discharge performance; if the open circuit voltage of the abnormal cell is greater than or equal to a second preset voltage and less than the first preset voltage, the abnormal cell is determined to be a second-level cell; if the open circuit voltage of the abnormal cell is less than the second preset voltage, the abnormal cell is determined to be a cell with unqualified self-discharge performance.

[0064] The first preset voltage and the second preset voltage are both equal to the average value of the open circuit voltage. For example, the first preset voltage can be set to The second preset voltage can be set to Wherein, σ is the standard deviation of the OCV remeasured of normal cells during the secondary screening process, and n is a positive integer ≥3.

[0065] It can be understood that the embodiment of the present application performs secondary screening of abnormal cells according to the average value of the open circuit voltage of normal cells and the open circuit voltage of the initial abnormal cells, specifically:

[0066] When the open circuit voltage of the abnormal battery cell is greater than the first preset voltage, the abnormal battery cell is determined to be a battery cell with qualified self-discharge performance;

[0067] When the open circuit voltage of the abnormal cell is greater than or equal to the second preset voltage and less than the first preset voltage, the abnormal cell is determined to be a second-level cell;

[0068] When the open circuit voltage of the abnormal battery cell is less than the second preset voltage, the abnormal battery cell is determined to be a battery cell with unqualified self-discharge performance.

[0069] The following is a specific example to describe the method for screening lithium-ion battery cells of the present application. Figure 2 As shown in the figure, the screening is mainly divided into two stages. The first stage relies on the K value to strictly screen the bad cells. The second stage is the long-term OCV screening of the bad cells to obtain the final qualified cells, which includes:

[0070] 1. Strict K value screening in the first stage

[0071] S1: After the cell capacity is divided, the battery is charged at a low current of 0.1 - 0.3C at 25±2℃ until the cell state of charge is 3% - 35% SOC;

[0072] S2: Incubate at 25±2℃ for 6-12h and record OCV1;

[0073] S3: The battery cells are transferred to a high temperature cabinet or room and placed at 45±2℃ for 24-48h;

[0074] S4: Cool the battery cell to 25℃±2℃ for 12±1h and record OCV2;

[0075] S5: After the battery cell is stored at 25℃±2℃ for 48-96h, test OCV3;

[0076] S6: Calculate the K value of each battery cell according to the voltage difference = (OCV3 OCV2) / Δt, where Δt is the number of hours between OCV2-OCV3;

[0077] S7: If the actual (For example, 0.035mv / h), the battery under test is an abnormal self-discharge battery; if the actual Then the battery to be tested is a normal battery.

[0078] 2. Second stage long-term OCV screening and grading

[0079] In the first stage, abnormal cells are collected in batches every 2 days and stored in a room at room temperature for 10-60 days together with 50 normal cells in the same batch, where N≥32EA.

[0080] After long-term storage, the abnormal cell OCV and normal cell OCV are tested, and the average value of the normal cell OCV is calculated as σ is 0.98mv.

[0081] If the abnormal cell meets This is the first stage overkill of the actually normal battery cell.

[0082] If the abnormal cell meets The second-stage battery cells are divided separately, and n is a positive integer ≥3.

[0083] Abnormal battery cell If the self-discharge is too large, it will be downgraded to Class B battery.

[0084] In summary, the short-term K value is strictly screened according to the mean + 2σ, which can shield the fluctuation errors of various factors in the process and will not cause the omission of self-discharge cells; the short-term K intercepts the cells for the second-stage long-term OCV screening and grading, that is, the long-term K screening avoids omissions and errors, and further grades them, which improves the concentration of the gears and the superiority of the matching.

[0085] According to the lithium-ion battery screening method proposed in the embodiment of the present application, the battery cells can be preliminarily screened according to the self-discharge rate of the battery cells to obtain abnormal battery cells and battery cells with qualified self-discharge performance, and the abnormal battery cells can be screened for the second time to obtain battery cells with qualified self-discharge performance among the abnormal battery cells, so as to prevent the battery cells from being missed or over-screened by only the primary screening, thereby improving the accuracy of the screening and further improving the performance and reliability of the lithium-ion battery module or battery pack.

[0086] Next, a lithium-ion battery cell screening device according to an embodiment of the present application is described with reference to the accompanying drawings.

[0087] Figure 3 It is a block diagram of a screening device for lithium-ion battery cells according to an embodiment of the present application.

[0088] like Figure 3 As shown, the lithium-ion battery screening device 10 includes: an acquisition module 100 , a first screening module 200 and a second screening module 300 .

[0089] Among them, the acquisition module 100 is used to obtain the open circuit voltage of each battery cell in the lithium-ion battery to be tested at different temperatures and different placement times; the first screening module 200 is used to calculate the self-discharge rate of each battery cell according to the open circuit voltage, and perform preliminary screening of all battery cells according to the self-discharge rate to obtain battery cells with qualified self-discharge performance and abnormal battery cells; the second screening module 300 is used to perform secondary screening of abnormal battery cells according to the open circuit voltage of battery cells with qualified self-discharge performance and abnormal battery cells, and obtain battery cells with qualified self-discharge performance among the abnormal battery cells.

[0090] In the embodiment of the present application, the second screening module 300 is further used to: calculate the average value of the open circuit voltage of the battery cells with qualified self-discharge performance; and perform secondary screening on the abnormal battery cells according to the average value of the open circuit voltage and the open circuit voltage of the abnormal battery cells.

[0091] In an embodiment of the present application, the open circuit voltage includes first to third voltages, and the first screening module 200 is further used to: obtain the measurement time of the second voltage and the third voltage respectively; calculate the time interval of the measurement time, and calculate the self-discharge rate of each battery cell according to the second voltage, the third voltage and the time interval.

[0092] In the embodiment of the present application, the first screening module 200 is further used to: calculate the average value of the self-discharge rates of all battery cells; and perform preliminary screening of all battery cells based on the average value of the self-discharge rates to obtain battery cells with qualified self-discharge performance and abnormal battery cells.

[0093] In an embodiment of the present application, the acquisition module 100 is further used to: after each battery cell is divided into different capacities, charge each battery cell to a target SOC with a preset current; after being placed at a first preset temperature for a first preset time, measure the first voltage of each battery cell; after measuring the first voltage, place the battery cell at a second preset temperature for a second preset time, and place the battery cell at the first preset temperature for a third preset time, and measure the second voltage of each battery cell; after measuring the second voltage, place the battery cell at the first preset temperature for a fourth preset time, and measure the third voltage of each battery cell, wherein the second preset temperature is higher than the first preset temperature, the fourth preset time is greater than the second preset time, and the second preset time is greater than the first preset time.

[0094] In the embodiment of the present application, the device 10 of the embodiment of the present application further includes: a storage module.

[0095] Among them, the storage module is used to store the battery cells with qualified self-discharge performance and the abnormal battery cells at a fourth preset temperature for a preset number of days before performing a secondary screening on the abnormal battery cells based on the open circuit voltages of the battery cells with qualified self-discharge performance and the abnormal battery cells, and then re-measure the open circuit voltage of each battery cell with qualified self-discharge performance and the open circuit voltage of each abnormal battery cell.

[0096] In the embodiment of the present application, the second screening module 300 is further used for: if the open circuit voltage of the abnormal battery cell is greater than the first preset voltage, then the abnormal battery cell is determined to be a battery cell with qualified self-discharge performance; if the open circuit voltage of the abnormal battery cell is greater than or equal to the second preset voltage and less than the first preset voltage, then the abnormal battery cell is determined to be a second-level battery cell; if the open circuit voltage of the abnormal battery cell is less than the second preset voltage, then the abnormal battery cell is determined to be a battery cell with unqualified self-discharge performance, wherein the first preset voltage and the second preset voltage are both related to the average value of the open circuit voltage.

[0097] It should be noted that the above explanations and descriptions of the embodiment of the screening method for lithium-ion battery cells are also applicable to the screening device for lithium-ion battery cells of this embodiment, and will not be repeated here.

[0098] According to the screening device for lithium-ion battery cells proposed in the embodiment of the present application, the cells can be preliminarily screened according to the self-discharge rate of the cells to obtain primary abnormal cells and cells with qualified self-discharge performance, and the primary abnormal cells can be screened for the second time to obtain cells with qualified self-discharge performance among the primary abnormal cells, so as to prevent the missed or over-screened cells by only the primary screening, thereby improving the accuracy of screening and further improving the performance and reliability of the lithium-ion battery module or battery pack.

[0099] Figure 4 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application. The electronic device may include:

[0100] Memory 401 , processor 402 , and a computer program stored in the memory 401 and executable on the processor 402 .

[0101] When the processor 402 executes the program, the lithium-ion battery cell screening method provided in the above embodiment is implemented.

[0102] Furthermore, the electronic device further comprises:

[0103] The communication interface 403 is used for communication between the memory 401 and the processor 402 .

[0104] The memory 401 is used to store computer programs that can be executed on the processor 402 .

[0105] The memory 401 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0106] If the memory 401, the processor 402 and the communication interface 403 are implemented independently, the communication interface 403, the memory 401 and the processor 402 can be connected to each other through a bus and communicate with each other. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 4 Only one thick line is used in the diagram, but this does not mean that there is only one bus or only one type of bus.

[0107] Optionally, in a specific implementation, if the memory 401, the processor 402 and the communication interface 403 are integrated on a chip, the memory 401, the processor 402 and the communication interface 403 can communicate with each other through an internal interface.

[0108] The processor 402 may be a central processing unit (CPU), or an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present application.

[0109] The embodiment of the present application also provides a computer-readable storage medium on which a computer program or instruction is stored. When the computer program or instruction is executed by a processor, the above lithium-ion battery screening method is implemented.

[0110] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0111] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, "N" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0112] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or N executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0113] It should be understood that the various parts of the present application can be implemented by hardware, software, firmware or a combination thereof. In the above embodiment, the N steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one or a combination of multiple of the following technologies known in the art: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0114] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

Claims

1. A method for screening lithium-ion battery cells, characterized in that: The following steps are involved: Obtain the open circuit voltage of each cell in the lithium-ion battery to be tested at different temperatures and different storage times; Calculating the self-discharge rate of each battery cell according to the open circuit voltage, and preliminarily screening all battery cells according to the self-discharge rate to obtain battery cells with qualified self-discharge performance and abnormal battery cells; The abnormal cells are screened for a second time according to the open circuit voltages of the cells with qualified self-discharge performance and the abnormal cells, so as to obtain the cells with qualified self-discharge performance among the abnormal cells.

2. The method for screening lithium-ion battery cells according to claim 1, characterized in that: The second screening of the abnormal battery cells according to the open circuit voltages of the battery cells with qualified self-discharge performance and the abnormal battery cells comprises: Calculating the average value of the open circuit voltage of the battery cells with qualified self-discharge performance; The abnormal cells are screened for a second time according to the average value of the open circuit voltage and the open circuit voltage of the abnormal cells.

3. The method for screening lithium-ion battery cells according to claim 2, characterized in that: The open circuit voltage includes first to third voltages, and calculating the self-discharge rate of each battery cell according to the open circuit voltage includes: respectively obtaining the measurement time of the second voltage and the third voltage; The time interval of the measurement time is calculated, and the self-discharge rate of each battery cell is calculated according to the second voltage, the third voltage and the time interval.

4. The method for screening lithium-ion battery cells according to claim 3, characterized in that: The preliminary screening of all cells according to the self-discharge rate to obtain cells with qualified self-discharge performance and abnormal cells includes: Calculate the average self-discharge rate of all cells; Based on the average value of the self-discharge rate, all the battery cells are preliminarily screened to obtain battery cells with qualified self-discharge performance and abnormal battery cells.

5. The method for screening lithium-ion battery cells according to claim 1, characterized in that: The step of obtaining the open circuit voltage of each cell in the lithium-ion battery to be tested at different temperatures and for different storage times includes: After dividing the capacity of each battery cell, charging each battery cell to a target SOC with a preset current; After being placed at a first preset temperature for a first preset time, measuring a first voltage of each battery cell; After measuring the first voltage, after placing the battery at a second preset temperature for a second preset time, and placing the battery at the first preset temperature for a third preset time, measuring the second voltage of each battery cell; After measuring the second voltage, the battery is placed at the first preset temperature for a fourth preset time and the third voltage of each battery cell is measured, wherein the second preset temperature is higher than the first preset temperature, the fourth preset time is greater than the second preset time, and the second preset time is greater than the first preset time.

6. The method for screening lithium-ion battery cells according to claim 2, characterized in that: Before performing secondary screening on the abnormal cells according to the open circuit voltages of the cells with qualified self-discharge performance and the abnormal cells, the method further includes: After storing the battery cells with qualified self-discharge performance and the abnormal battery cells at a fourth preset temperature for a preset number of days, the open circuit voltage of each battery cell with qualified self-discharge performance and the open circuit voltage of each abnormal battery cell are remeasured.

7. The method for screening lithium-ion battery cells according to claim 6, characterized in that: The second screening of the abnormal cells according to the average value of the open circuit voltage and the open circuit voltage of the abnormal cells comprises: If the open circuit voltage of the abnormal battery cell is greater than the first preset voltage, the abnormal battery cell is determined to be a battery cell with qualified self-discharge performance; If the open circuit voltage of the abnormal cell is greater than or equal to the second preset voltage and less than the first preset voltage, the abnormal cell is determined to be a second-level cell; If the open circuit voltage of the abnormal cell is less than the second preset voltage, the abnormal cell is determined to be a cell with unqualified self-discharge performance, wherein the first preset voltage and the second preset voltage are both related to the average value of the open circuit voltage.

8. A method for screening lithium-ion battery cells, characterized in that: include: An acquisition module is used to obtain the open circuit voltage of each cell in the lithium-ion battery to be tested at different temperatures and different storage times; A first screening module, used for calculating the self-discharge rate of each battery cell according to the open circuit voltage, and performing preliminary screening on all battery cells according to the self-discharge rate to obtain battery cells with qualified self-discharge performance and primary abnormal battery cells; The second screening module is used to perform secondary screening on the abnormal cells according to the open circuit voltages of the cells with qualified self-discharge performance and the abnormal cells, so as to obtain cells with qualified self-discharge performance among the abnormal cells.

9. An electronic device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the lithium ion battery screening method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program or instruction stored thereon, characterized in that: The computer program or instruction is executed by a processor to implement the lithium ion battery screening method according to any one of claims 1 to 7.

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