A method and system for evaluating battery capacity consistency

Abstract

The application discloses a kind of method and system for evaluating battery capacity consistency, method includes: setting multiple test instruments capable of forming multiple detection areas in the transverse direction of pole piece, and multiple detection areas form the form of arrangement in the process of pole piece winding;Multiple test instruments correspond to detect the area density in detection area;According to the area density in detection area, the average value and standard deviation of the area density of detection area in longitudinal direction are obtained, the longitudinal area density standard interval is obtained;And the average value and standard deviation of the difference value of the area density of adjacent two transverse detection areas are obtained, the transverse area density standard interval is obtained, and the consistency of the area density of pole piece in longitudinal direction and in transverse direction is evaluated;When the area density of detection area on pole piece is all in area density standard interval, then the battery cell matched by the roll core formed by the pole piece winding can evaluate the capacity of the battery within the capacity standard of normal screening. Through the method disclosed by the application, the capacity of the battery can be evaluated.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a method and system for evaluating battery capacity consistency. Background Technology

[0002] Lithium-ion batteries, as a new energy source, boast advantages such as high operating voltage, high specific capacity, long charge / discharge life, and no memory effect. As lithium-ion batteries gradually become the mainstream energy choice, the demand for them is increasing. Simultaneously, the safety of lithium-ion batteries is becoming a growing concern. On one hand, the manufacturing trend of lithium-ion batteries is towards higher energy and higher capacity, leading to larger cell sizes. This results in higher current during the battery grading process, increasing the equipment cost for new production lines year by year. On the other hand, rising lithium ore prices are also driving up the manufacturing cost of lithium-ion batteries annually.

[0003] Traditional lithium battery manufacturing processes include a capacity grading process. The primary purpose of capacity grading is simply to distinguish and screen cells with abnormal capacity, so as to avoid large voltage differences in subsequent modules or packages due to the capacity differences of some cells. Capacity grading itself has no significant meaning for battery performance. However, if capacity grading is directly eliminated, it is difficult to effectively assess the differences between cells. The main reason is the difference in the consistency of the core due to the difference in the surface density of the electrode sheets. Therefore, how to quickly and effectively assess the surface density consistency of the electrode sheets is the key factor in solving the problem of assessing capacity consistency.

[0004] In the prior art, patent publication number CN112827863A discloses a battery consistency screening method and apparatus based on the manufacturing process. This method obtains environmental factor parameters from the manufacturing process of batteries in the same batch, groups and screens the batteries in the same batch sequentially based on these parameters, and statistically analyzes the capacity distribution of each group of batteries under different environmental factor conditions using a three-parameter Weibull probability model. This yields the capacity Weibull statistical characteristics corresponding to each group of batteries, and based on these characteristics, determines the target battery for each group under the same environmental factor parameter conditions and the target numerical range corresponding to the environmental factor parameters. In the prior art, battery consistency screening aims to improve battery consistency by providing a reasonable numerical range for environmental control during the battery manufacturing process, eliminating the interference caused by the uncertainty of environmental factors. However, this approach relies on the fact that environmental factors are difficult to control in practice. Summary of the Invention

[0005] The technical problem to be solved by this invention is: to solve the problem of the inability to assess the consistency of battery cells after the capacity testing process is eliminated.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] A method for evaluating battery capacity consistency includes:

[0008] Multiple testers are provided, and the multiple testers can form multiple detection areas in the transverse direction of the electrode sheet, and the multiple detection areas are arranged in an array during the winding of the electrode sheet;

[0009] Multiple of the aforementioned testing instruments are used to detect the areal density within the detection area;

[0010] Based on the surface density within the detection area, the average value and standard deviation of the surface density of the detection area in the longitudinal direction are obtained, and the standard interval of the longitudinal surface density is obtained; and the average value and standard deviation of the difference in surface density between two adjacent transverse detection areas are obtained, and the standard interval of the transverse surface density is obtained.

[0011] Using the longitudinal and transverse areal density standard ranges as standards, the consistency of the longitudinal and transverse areal densities of the electrode is evaluated. When the areal densities of the detection areas on the electrode are all within the longitudinal and transverse areal density standard ranges, the cell matched by the core formed by the electrode can be evaluated to have a capacity within the normal screening capacity standard.

[0012] Advantages: By identifying the consistency of the electrode sheets at the front end, it breaks away from the traditional method that can only assess the consistency of the core, reduces the capacity grading process, and simplifies the process flow. Even if the capacity grading process is eliminated, the battery capacity can still be assessed.

[0013] In one embodiment of the present invention, the surface density test cycle of the electrode in the longitudinal direction is to identify a single electrode of a fixed length by winding, and the surface density data of each column is a set of data; and the detection area corresponding to each set of surface density data has an equal lateral spacing between adjacent detection areas.

[0014] In one embodiment of the present invention, the detection area corresponding to the density on the longitudinal surface of the electrode has a longitudinal spacing of ≥1mm between two adjacent detection areas.

[0015] In one embodiment of the present invention, before obtaining the longitudinal surface density standard interval and the transverse surface density standard interval, each set of surface density data in the electrode detection area is sorted, and several values ​​at the beginning and end are removed respectively.

[0016] In one embodiment of the present invention, the plurality of values ​​are specifically: m = s * (0.2 ~ 1)%, where m represents the specific number of the plurality of values ​​and s represents the total number of areal density data in the detection area on the electrode.

[0017] In one embodiment of the present invention, if the areal density of any longitudinal detection area on the electrode is not within the longitudinal areal density standard range or the areal density difference between any two adjacent transverse detection areas on the electrode is not within the transverse areal density standard range, then the electrode is an electrode with unqualified consistency, and the electrode with unqualified consistency is screened out.

[0018] In one embodiment of the present invention, the electrode sheet includes a positive electrode sheet and a negative electrode sheet, which are respectively placed on the unwinding mechanisms on both sides of the winding machine.

[0019] In one embodiment of the present invention, the lateral spacing is in the range of 20mm≤J≤40mm, where J represents the lateral spacing.

[0020] In one embodiment of the present invention, a plurality of the testers are integrated on a winding machine, and the winding machine realizes the areal density of the test areas of the plurality of testers while winding the electrode sheet.

[0021] The present invention also provides a system for evaluating battery capacity consistency, comprising:

[0022] The detection area module is used to set up multiple testers, which can form multiple detection areas in the transverse direction of the electrode sheet, and the multiple detection areas are arranged in an array during the winding of the electrode sheet;

[0023] A surface density module is used for multiple testing instruments to detect the surface density within the detection area.

[0024] The standard interval module is used to obtain the average value and standard deviation of the surface density of the detection area in the longitudinal direction based on the surface density in the detection area, and to obtain the standard interval of the longitudinal surface density; and to obtain the average value and standard deviation of the difference between the surface densities of two adjacent detection areas in the transverse direction, and to obtain the standard interval of the transverse surface density.

[0025] The consistency assessment module is used to assess the consistency of the longitudinal and transverse surface densities of the electrode using the longitudinal surface density standard range and the transverse surface density standard range as standards. When the surface densities of the detection areas on the electrode are all within the longitudinal and transverse surface density standard ranges, the battery formed by winding the electrode can be assessed to have a capacity within the normal screening capacity standard.

[0026] Compared with existing technologies, the beneficial effects of this invention are: it enables rapid online evaluation of the areal density of individual positive and negative electrodes, achieving consistency in matching the winding core through electrode areal density consistency, and further achieving cell consistency through winding core consistency matching, thereby solving the problem of being unable to evaluate battery capacity consistency after eliminating capacity grading. This invention can effectively achieve consistent cell capacity evaluation, making blind capacity matching possible in subsequent grouping processes, eliminating concerns about large voltage differences between modules or entire packs, and thus directly eliminating the capacity grading process, achieving the goal of directly screening self-discharge of cells after formation. Attached Figure Description

[0027] Figure 1 This is a flowchart of a method for evaluating battery capacity consistency according to the present invention.

[0028] Figure 2 This is a schematic diagram of the positive electrode sheet of the present invention.

[0029] Figure 3 This is a schematic diagram of the negative electrode sheet of the present invention.

[0030] Figure 4 This is a system block diagram for evaluating battery capacity consistency according to the present invention. Detailed Implementation

[0031] To facilitate understanding of the technical solution of the present invention by those skilled in the art, the technical solution of the present invention will now be further described in conjunction with the accompanying drawings.

[0032] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0033] Please see Figure 1 As shown, the present invention provides a method for evaluating battery capacity consistency, comprising:

[0034] S100, multiple testers are provided, which can form multiple detection areas in the transverse direction of the electrode sheet, and the multiple detection areas are arranged in an array during the winding of the electrode sheet.

[0035] Please see Figures 1 to 3As shown, in one embodiment of the present invention, an electrode is formed by coating a substrate 100. The electrode includes a positive electrode 110 and a negative electrode 120. When the substrate 100 is made of aluminum foil, it is the positive electrode 110; when the substrate 100 is made of copper foil, it is the negative electrode 120. Multiple testing instruments are integrated on a winding machine. The winding machine simultaneously winds the electrode and performs areal density testing on the areas of the areas tested by the multiple testing instruments. Specifically, the positive and negative electrode sheets to be tested are placed on unwinding mechanisms on both sides of the winding machine. Multiple testing instruments are fixedly connected to the winding machine, and the multiple testing instruments can form multiple testing areas 130 in the transverse direction of the electrode.

[0036] S200, multiple testing instruments are used to detect the areal density within the detection area.

[0037] Please see Figures 1 to 3 As shown, in one embodiment of the present invention, a winding machine is started, with a winding speed of, for example, 60 m / min. A single positive electrode 110 has a length of, for example, 7777 mm and a width of, for example, 94 mm. A single negative electrode 120 has a length of, for example, 8077 mm and a width of, for example, 98 mm. During the winding process, a testing instrument is activated to test the areal density of the electrode. The testing frequency is, for example, 500 Hz. The winding direction is as indicated by arrow E. As the winding machine winds the electrode, multiple testing areas are arranged in an array. Specifically, horizontally, the number of testing areas in each row corresponds to the number of testing instruments and the number of sets of data. The longitudinal areal density test cycle is for identifying a single electrode of a fixed length during winding. The areal density data of one column constitutes one set of data (as shown in the attached figure). Figure 2The areal density data corresponding to the detection area within the reference number 140 is a set of data, and the lateral spacing between adjacent detection areas corresponding to a set of areal density data is equal. The lateral spacing is within the range of 20mm ≤ J ≤ 40mm, where J represents the lateral spacing. The winding machine is an existing device and will not be described further here. The longitudinal spacing between adjacent detection areas corresponding to the longitudinal surface density of the electrode sheet is ≥ 1mm. Further, in this embodiment, the lateral test spacing is set to 20mm, and the tester is an areal density tester. The longitudinal surface density of the positive electrode sheet 110 is tested, denoted as Pxn, with an example of 3880 test data points; the longitudinal surface density of the negative electrode sheet 120 is tested, denoted as Qxn, with an example of 4385 test data points. x represents a specific data set in the lateral direction, n represents the position of the detection area in the longitudinal direction, P represents the areal density of the positive electrode sheet detection area, and Q represents the areal density of the negative electrode sheet detection area. Specifically, P11 represents the areal density data of the first column of the first group of positive electrode sheets, P12 represents the areal density data of the second column of the first group of positive electrode sheets, and so on. P21 represents the areal density data of the first column of the second group of positive electrode sheets, P22 represents the areal density data of the second column of the second group of positive electrode sheets, and so on. The areal density data of negative electrode sheets is recorded in the same way as that of positive electrode sheets.

[0038] Please see Figures 1 to 3 As shown, in one embodiment of the present invention, each set of areal density data within the detection area on the electrode is sorted, and several values ​​at the beginning and end are removed to improve the accuracy of the areal density data for the positive and negative electrodes. The sorting method is from smallest to largest or from largest to smallest. Specifically, the several values ​​are: m = s * (0.2~1)%, where m represents the specific number of values, and s represents the total number of areal density data within the detection area on the electrode. In this embodiment, m = s * 0.2%, meaning that m = 3380 * 0.2% = 17 areal densities Pxn in the longitudinal direction of the positive electrode are removed, and m = 4385 * 0.2% = 22 areal densities Qxn in the longitudinal direction of the negative electrode are removed. Please refer to Tables 1 and 2 for partial data, which only represent partial test values ​​for one positive electrode and one negative electrode.

[0039] Table 1

[0040]

[0041] Table 2

[0042]

[0043] S300: Based on the areal density within the detection area, obtain the average value and standard deviation of the areal density in the longitudinal direction of the detection area, and obtain a standard interval for the longitudinal areal density. Also, obtain the average value and standard deviation of the differences in areal density between two adjacent transverse detection areas, and obtain a standard interval for the transverse areal density.

[0044] Referring to Figure 1, in one embodiment of the present invention, the average value and standard deviation of the surface density of the detection area in the longitudinal direction are obtained based on the surface density data obtained in step S200. Specifically, Ax represents the average value of the surface density of the detection area in the longitudinal direction of the positive electrode sheet, σ1x represents the standard deviation of the surface density of the detection area in the longitudinal direction of the positive electrode sheet, Bx represents the average value of the surface density of the detection area in the longitudinal direction of the negative electrode sheet, and σ2x represents the standard deviation of the surface density of the detection area in the longitudinal direction of the negative electrode sheet. C represents the average value of the difference in surface density between two adjacent transverse detection areas on the positive electrode sheet, and σ3 represents the standard deviation of the difference in surface density between two adjacent transverse detection areas on the positive electrode sheet. D represents the average value of the difference in surface density between two adjacent transverse detection areas on the negative electrode sheet, and σ4 represents the standard deviation of the difference in surface density between two adjacent transverse detection areas on the negative electrode sheet. That is, Ax=(Px1+Px2+...+Pxn) / sm, Bx=(Qx1+Qx2+...+Qxn) / sm, C=[(P21-P11)+...+(Pxn-P(x-1)n)] / sm, D=[(Q21-Q11)+...+(Qxn-Q(x-1)n)] / sm.

[0045] Referring to Figure 1, in one embodiment of the present invention, the longitudinal areal density standard intervals include the longitudinal areal density standard intervals for the positive electrode and the negative electrode, with the positive electrode being Ax ± (1~3)σ1x and the negative electrode being Bx ± (1~3)σ2x. The transverse areal density standard intervals include the transverse areal density standard intervals for the positive and negative electrodes, with the positive electrode being C ± (1~3)σ3 and the negative electrode being D ± (1~3)σ4. Please refer to Table 3, which shows the average value and standard deviation of the electrodes.

[0046] Table 3

[0047]

[0048] S400, using the longitudinal surface density standard range and the transverse surface density standard range as standards, perform a consistency evaluation of the longitudinal surface density and transverse surface density of the electrode; when the surface density of the detection area on the electrode is within the longitudinal surface density standard range and the transverse surface density standard range, the cell matched by the core formed by the winding of the electrode can be evaluated to have a capacity within the normal screening capacity standard.

[0049] Please see Figure 1 As shown, in one embodiment of the present invention, the longitudinal surface density consistency of the positive and negative electrode sheets is evaluated using a longitudinal surface density standard range as the standard, and the surface density consistency of two adjacent transverse detection areas on the positive and negative electrode sheets is evaluated using a transverse surface density standard range as the standard. Only when the longitudinal detection area surface density and the difference in surface density between two adjacent transverse detection areas of the positive and negative electrode sheets are both within the longitudinal and transverse surface density standard ranges, is the cell matched with the core formed by winding the electrode sheet a cell with acceptable consistency, and the battery capacity can be further evaluated to be within the normal screening capacity standard. If the surface density of any longitudinal detection area on the electrode sheet is not within the longitudinal surface density standard range, or if the difference in surface density between any two adjacent transverse detection areas on the electrode sheet is not within the transverse surface density standard range, then the electrode sheet is an unacceptable consistency electrode sheet, and the unacceptable consistency electrode sheets are screened out. Only when both the positive and negative electrode sheets are of consistent quality and are wound into a qualified core can they be matched to form a qualified battery with a capacity within the normal screening capacity standard.

[0050] Please see Figures 1 to 3 As shown, in one embodiment of the present invention, multiple testing instruments are interconnected with the winding machine and the production system MES to collect and mark data on the electrode sheets, which can quickly and effectively evaluate the consistency of the electrode sheets and effectively perform front-end screening.

[0051] Please see Figure 4As shown, the present invention also provides a system for evaluating battery capacity consistency, including a detection area module 210, an areal density module 220, a standard interval module 230, and a consistency evaluation module 340. The detection area module 210 is used to set up multiple testers, which can form multiple detection areas in the transverse direction of the electrode sheet, and arrange the multiple detection areas in an arranged form during the winding of the electrode sheet. The areal density module 220 is used for the multiple testers to detect the areal density within the detection area. The standard interval module 230 is used to obtain the average value and standard deviation of the areal density of the detection area in the longitudinal direction based on the areal density within the detection area, and obtain a longitudinal areal density standard interval; and to obtain the average value and standard deviation of the difference in areal density between two adjacent transverse detection areas, and obtain a transverse areal density standard interval. The consistency evaluation module 340 is used to evaluate the consistency of the longitudinal surface density and the transverse surface density of the electrode using the longitudinal surface density standard range and the transverse surface density standard range as standards. When the surface density of the detection area on the electrode is within the longitudinal surface density standard range and the transverse surface density standard range, the battery formed by winding the electrode can be evaluated to have a capacity within the normal screening capacity standard.

[0052] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0053] The above embodiments are merely examples of implementation methods of the invention. The scope of protection of the present invention is not limited to the above embodiments. For those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A method of assessing battery capacity consistency, characterized by, The method comprises the following steps: a plurality of testers are arranged, which can form a plurality of detection areas in the transverse direction of the electrode sheet, and the detection areas form an array during the winding of the electrode sheet; the plurality of testers correspond to the detection of the area density in the detection area; according to the area density in the detection area, the average value and the standard deviation of the area density of the detection area in the longitudinal direction are obtained, and the longitudinal area density standard interval is obtained; the average value and the standard deviation of the difference value of the area density of the adjacent two transverse detection areas are obtained, and the transverse area density standard interval is obtained; the longitudinal area density and the transverse area density consistency of the electrode sheet are evaluated by taking the longitudinal area density standard interval and the transverse area density standard interval as the standard; when the area density of the detection area on the electrode sheet is within the longitudinal area density standard interval and the transverse area density standard interval, the battery capacity of the battery formed by the winding of the electrode sheet is within the normal screening capacity standard; wherein the longitudinal area density standard interval includes the positive electrode sheet longitudinal area density standard interval Ax±(1-3)σ1x and the negative electrode sheet longitudinal area density standard interval Bx±(1-3)σ2x; the transverse area density standard interval includes the positive electrode sheet transverse area density standard interval C±(1-3)σ3 and the negative electrode sheet transverse area density standard interval D±(1-3)σ4; and Ax represents the average value of the area density of the detection area in the longitudinal direction of the positive electrode sheet, σ1x represents the standard deviation of the area density of the detection area in the longitudinal direction of the positive electrode sheet, Bx represents the average value of the area density of the detection area in the longitudinal direction of the negative electrode sheet, and σ2x represents the standard deviation of the area density of the detection area in the longitudinal direction of the negative electrode sheet; C represents the average value of the difference value of the area density of the adjacent two transverse detection areas on the positive electrode sheet, σ3 represents the standard deviation of the difference value of the area density of the adjacent two transverse detection areas on the positive electrode sheet, D represents the average value of the difference value of the area density of the adjacent two transverse detection areas on the negative electrode sheet, and σ4 represents the standard deviation of the difference value of the area density of the adjacent two transverse detection areas on the negative electrode sheet.

2. The method of assessing battery capacity consistency according to claim 1, wherein, The longitudinal area density test cycle of the electrode sheet is to recognize a single electrode sheet of a fixed length, and the area density data of each column is a group of data; and the detection area corresponding to each group of area density data has an equal transverse distance between adjacent two groups of detection areas.

3. The method of assessing battery capacity consistency according to claim 1, wherein, The longitudinal distance between the adjacent two detection areas of the detection area corresponding to the longitudinal area density of the electrode sheet is greater than or equal to 1 mm.

4. The method of assessing battery capacity consistency according to claim 2, wherein, Before obtaining the longitudinal area density standard interval and the transverse area density standard interval, each group of area density data in the detection area of the electrode sheet is sorted, and a certain number of values at the beginning and end are removed, respectively.

5. The method of assessing battery capacity consistency according to claim 4, wherein, The several values are specifically: Wherein, m represents the specific number of the several values, and s represents the total number of the surface density data in the detection area on the pole piece.

6. The method of assessing battery capacity consistency of claim 1, wherein, If the area density of any one longitudinal detection area on the electrode sheet is not within the longitudinal area density standard interval or the difference value of the area density of any one adjacent two transverse detection areas on the electrode sheet is not within the transverse area density standard interval, the electrode sheet is a consistency unqualified electrode sheet, and the consistency unqualified electrode sheet is screened out.

7. The method of assessing the consistency of the capacity of a battery according to any one of claims 1 to 6, characterized in that, The electrode sheet includes a positive electrode sheet and a negative electrode sheet, and the positive electrode sheet and the negative electrode sheet are respectively arranged on the unwinding mechanisms on both sides of the winding machine.

8. The method of assessing battery capacity consistency of claim 2, wherein, The lateral spacing is in the range of 20mm≤J≤40mm, wherein J represents the lateral spacing.

9. The method of assessing battery capacity consistency of claim 1, wherein, The plurality of testers are integrated on a winding machine, which realizes the plurality of testers to test the area density of the detection area while winding the pole piece.

10. A system for assessing consistency of battery capacity, the system comprising: Comprise: A detection area module for setting a plurality of testers, which can form a plurality of detection areas in the lateral direction of the pole piece, and the plurality of detection areas form an array during the winding process of the pole piece; An area density module for the plurality of testers to detect the area density in the detection area; A standard interval module for obtaining the average and standard deviation of the area density of the detection area in the longitudinal direction according to the area density in the detection area, and obtaining the longitudinal area density standard interval; And obtaining the average and standard deviation of the difference value of the area density of the adjacent two detection areas in the lateral direction, and obtaining the lateral area density standard interval; A consistency evaluation module for evaluating the consistency of the area density in the longitudinal direction and the lateral direction of the pole piece according to the longitudinal area density standard interval and the lateral area density standard interval; When the area density of the detection area on the pole piece is within the longitudinal area density standard interval and the lateral area density standard interval, the battery formed by winding the pole piece can evaluate the capacity of the battery within the normal screening capacity standard; Wherein, the longitudinal area density standard interval includes the positive pole piece longitudinal area density standard interval Ax±(1-3)σ1x and the negative pole piece longitudinal area density standard interval Bx±(1-3)σ2x; The lateral area density standard interval includes the positive pole piece lateral area density standard interval C±(1-3)σ3 and the negative pole piece lateral area density standard interval D±(1-3)σ4; And Ax represents the average of the area density of the detection area in the longitudinal direction of the positive pole piece, σ1x represents the standard deviation of the area density of the detection area in the longitudinal direction of the positive pole piece, Bx represents the average of the area density of the detection area in the longitudinal direction of the negative pole piece, σ2x represents the standard deviation of the area density of the detection area in the longitudinal direction of the negative pole piece; C represents the average of the difference value of the area density of the adjacent two detection areas in the lateral direction of the positive pole piece, σ3 represents the standard deviation of the difference value of the area density of the adjacent two detection areas in the lateral direction of the positive pole piece, D represents the average of the difference value of the area density of the adjacent two detection areas in the lateral direction of the negative pole piece, and σ4 represents the standard deviation of the difference value of the area density of the adjacent two detection areas in the lateral direction of the negative pole piece.

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