Battery cell detection method, battery cell detection device and battery cell deviation correction method

Abstract

A battery cell detection method, comprising: acquiring an image of an end face (10) of a battery cell, identifying two feature regions (S) respectively having one-to-one correspondence to tabs (P) of two polarities, and determining a reference point (O) at the center of the end face on the basis of the image of the end face (10), the two feature regions (S) being respectively arranged on two sides of the reference point (O); rotating the image of the end face (10) to form a set included angle (b) between the arrangement direction of the two feature regions (S) and a reference line (L1), the reference line (L1) passing through the reference point (O), comprising preliminarily adjusting the angle of the image of the end face (10) to enable the two tabs (P) having opposite polarities theoretically located at a central position between two forbidden regions (D), wherein the two feature regions do not overlap the two prohibited regions (D) when the degree of alignment of the two feature regions meets requirements; determining whether the two feature regions (S) overlap the two forbidden regions (D), and if so, determining that the battery cell is non-conformant and preventing the battery cell having poor degree of alignment from flowing out, wherein the two forbidden regions (D) are located on the reference line (L1) and are symmetrically distributed on two sides of the reference point (O). Also disclosed are a battery cell detection apparatus and a battery cell deviation correction method.

Description

A method for testing battery cells, a device for testing battery cells, and a method for correcting battery cell deviation.

[0001] This application claims priority to Chinese Patent Application No. 202411478608.5, filed on October 22, 2024, entitled "A Cell Testing Method, a Cell Testing Device and a Cell Correction Method", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to the field of battery technology, and in particular to a cell testing method, a cell testing device, and a cell correction method. Background Technology

[0003] In the production process of cylindrical battery cells (such as top-current cylindrical batteries), the positive and negative electrode tabs are located on the same side of the cell. However, during the winding process to form the cell, the tabs may deviate from their ideal positions, resulting in misalignment and leading to safety issues such as short circuits, excessive internal resistance, and poor appearance. Traditional technologies struggle to effectively detect the alignment of the tabs. Summary of the Invention

[0004] This invention discloses a cell testing method, a cell testing device, and a cell alignment method for effectively detecting the alignment of the electrode tabs.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] In a first aspect, a method for testing a battery cell is provided, wherein the end face of the battery cell is provided with tabs of opposite polarity; the method includes: acquiring an image of the end face of the battery cell, identifying two feature regions that are one-to-one with the tabs of the two polarities respectively, and determining a reference point at the center of the end face based on the end face image, wherein the two feature regions are arranged on both sides of the reference point; rotating the end face image so that the arrangement direction of the two feature regions forms a set angle with a reference line, the reference line passing through the reference point, and first preliminarily adjusting the angle of the end face image so that theoretically the two tabs of opposite polarities are centered between two prohibited regions, and the two will not overlap with the two prohibited regions if the alignment meets the requirements; determining whether the two feature regions overlap with the two prohibited regions, and if so, determining that the battery cell is unqualified, wherein the two prohibited regions are located on the reference line and are symmetrically distributed on both sides of the reference point. The area adjacent to the reference line is designated as a prohibited area. If two feature areas overlap with this prohibited area, it indicates that the two feature areas are too close and have poor alignment. These cells are considered seriously defective products and are deemed unqualified, effectively filtering out seriously defective products and preventing them from leaving the market.

[0007] Secondly, a battery cell testing device is provided, wherein the end face of the battery cell is provided with tabs of opposite polarity; the battery cell testing device includes: an image acquisition unit and a processing unit; the image acquisition unit is used to acquire an image of the end face of the battery cell, identify two feature regions that are one-to-one with the tabs of the two polarities respectively, and determine a reference point at the center of the end face based on the end face image, wherein the two feature regions are arranged on both sides of the reference point; the processing unit is used to adjust the end face image so that the arrangement direction of the two feature regions forms a set angle with a reference line, the reference line passing through the reference point, and determine whether the two feature regions overlap with two prohibited regions. If so, the battery cell is determined to be unqualified, wherein the two prohibited regions are located on the reference line and are symmetrically distributed on both sides of the reference point.

[0008] The advantages of the battery cell testing device and the battery cell testing method described above compared to the prior art are the same, and will not be repeated here.

[0009] Thirdly, a cell correction method based on the cell detection method described in any one of the technical solutions 13 to 16 above, comprising: when the absolute value of the difference between an initial angle and a set angle is greater than 0, controlling a driving component to drive the cell to rotate by the angle of the difference, wherein the rotation direction of the cell is the same as the rotation direction of the end face image, to perform preliminary correction of the cell, wherein the initial angle refers to the angle between the arrangement direction of the two feature regions and the reference line before the end face image is rotated; when the areas of interest of the two feature regions are located on the same side of the reference point in the direction of the reference line, rotating the cell so that the areas of the areas of interest of the two feature regions are equal or... The corresponding circumferential angles are the same, thus distributing the alignment deviation of the battery cell across the two feature regions, minimizing the positional deviation of both feature regions; or, when the parts of interest of the two feature regions are located on different sides of the reference point in the direction of the reference line, the battery cell is rotated so that the areas of the feature regions in the four danger zones tend to be close, thus distributing the alignment deviation of the battery cell across the two feature regions, minimizing the positional deviation of both feature regions; wherein, the part of interest refers to the larger portion of the overlapping area between each feature region and the danger zones on both sides. Attached Figure Description

[0010] Figure 1 is a schematic diagram of the end face image obtained in the cell testing method provided in the embodiment of this application;

[0011] Figure 2 is a schematic diagram of the identification of the feature region S in the cell detection method provided in the embodiment of this application;

[0012] Figure 3 shows a schematic diagram of the cell testing method provided in this application after rotating the end face image;

[0013] Figure 4 shows a schematic diagram of region division of the image shown in Figure 3;

[0014] Figure 5 shows the positional relationship between the prohibited area D and the feature area S in Figure 4;

[0015] Figure 6 shows a schematic diagram of the positional relationship of the tangents in the feature region S in Figure 4;

[0016] Figure 7 shows a schematic diagram of the positional relationship between the first and second medians of the feature region S;

[0017] Figure 8 shows the positional relationship between the ideal region T and the characteristic region S of the electrode ear in Figure 4;

[0018] Figure 9 shows the positional relationship between the dangerous area G of the electrode ear and the characteristic area S in Figure 4;

[0019] Figure 10 shows the positional relationship between each feature region S and the corresponding virtual welding region W in Figure 3;

[0020] Figure 11 shows a flowchart of an application scenario of the cell detection method and cell correction method provided in the embodiments of this application;

[0021] Figure 12 shows a schematic diagram of the image acquisition unit used in step S3 of Figure 11;

[0022] Figure 13 shows a schematic diagram of the image acquisition unit used in step S6 of Figure 11. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] To gain a clearer understanding of the cell testing method provided in this application, a brief background is given below. The cell of a cylindrical battery (such as a top-current cylindrical battery) can be a wound cell. For example, a roughly cylindrical wound cell is formed by winding alternating layers of positive and negative electrode sheets. A separator is provided between adjacent positive and negative electrode sheets to insulate them. To achieve good insulation, the length of the separator can be greater than the lengths of the positive and negative electrode sheets.

[0025] Referring to Figure 1, the end face 10 of the wound battery cell is provided with tabs P of opposite polarity. The tabs P may include multiple positive tabs P1 connected to the positive electrode plate (refer to Figure 1) and multiple negative tabs P2 connected to the negative electrode plate. The positive tabs P1 and negative tabs P2 are located on the same side of the battery cell. For example, the material of the positive tabs P1 may be copper and the material of the negative tabs P2 may be aluminum, but it is not limited to these. The materials of the positive tabs P1 and the negative tabs P2 can be adjusted as needed.

[0026] Before winding, multiple positive electrode tabs P1 (refer to Figure 1) are sequentially and spaced apart on the edge of the positive electrode sheet, and multiple negative electrode tabs P2 (refer to Figure 1) are sequentially and spaced apart on the edge of the negative electrode sheet. After the cell is wound, the alignment of the multiple positive electrode tabs P1 corresponding to the positive electrode sheets from the inner layer to the outer layer should theoretically be within a reasonable range, and the negative electrode tabs P2 should also meet similar requirements. However, in the actual winding process, misalignment can easily occur between the inner layer positive electrode tabs P1 and the outer layer positive electrode tabs P1, causing the positive electrode tabs P1 to gradually shift and the alignment to fail to meet the requirements. This may result in the distance between the positive electrode tabs P1 and the negative electrode tabs P2 being too close, leading to safety issues such as short circuits, excessive internal resistance, and poor appearance of the cell.

[0027] To address the aforementioned issues, the battery cell testing method provided in this application includes: referring to Figure 1, acquiring an end-face image of the battery cell; then referring to Figure 2, identifying two feature regions S corresponding one-to-one with the two polarity tabs P, such as the positive feature region S1 corresponding to the positive tab P1 and the negative feature region S2 corresponding to the negative tab P2; and determining a reference point O at the center of the end-face based on the end-face image, wherein the two feature regions S are positioned on either side of the reference point O, and the reference point O serves as a reference point in subsequent steps; referring to Figure 3, rotating the end-face image so that the arrangement direction of the two feature regions S aligns with... Reference line L1 is at a set angle b and passes through reference point O. In this step, the angle of the end face image is initially adjusted so that, theoretically, the positive electrode tab P1 and the negative electrode tab P2 are centered between the two prohibited areas D. If the alignment meets the requirements, they will not overlap with the two prohibited areas D. Next, it is determined whether the two feature areas S overlap with the two prohibited areas D. If so, the cell is deemed unqualified. The two prohibited areas D are located on reference line L1 and are symmetrically distributed on both sides of reference point O. Prohibited area D1 is located to the left of reference point O, and prohibited area D2 is located to the right of reference point O. The area adjacent to reference line L1 is designated as prohibited area D. If the positive electrode feature area S1 overlaps with at least one of prohibited areas D1 and D2, or if the negative electrode feature area S2 overlaps with at least one of prohibited areas D1 and D2, it means that the positive electrode feature area S1 and the negative electrode feature area S2 are too close together. This portion of the battery cell is considered a severely defective product and is deemed unqualified, effectively filtering out severely defective products and preventing them from leaving the factory. Specifically, after rotating the end-face image as described above and initially adjusting the angle of the end-face image, the positive electrode feature area S1 can be located above reference L1, while the negative electrode feature area S2 can be located below reference L1. An additional detection step can be added: the color of the two feature areas S is used to determine whether the positive electrode feature area S1 and the negative electrode feature area S2 conform to the above rule. If they do not conform, the battery cell is deemed unqualified.

[0028] Referring to Figures 4 and 5, in a specific embodiment, each prohibited area D is a sector centered on the reference point O and symmetrical about the reference line L1. For example, in Figure 5, both are sectors and symmetrical about the reference line L1. Theoretically, after the battery cell is wound, multiple positive electrode tabs P1 form a sector centered on the reference point O, and multiple negative electrode tabs P2 also form a sector centered on the reference point O. Therefore, the two feature areas S are theoretically sector-shaped; the prohibited area D is also sector-shaped and set in the above manner. Theoretically, the two prohibited areas D can be located exactly in the middle of the positive feature area S1 and the negative feature area S2, and are adapted to the sector shape of the feature area S, thus having a relatively balanced warning effect on both feature areas S. The term "theoretically" means that the positive electrode tabs P1 and the negative electrode tabs P2 do not shift during the winding process. The circumferential angle corresponding to each prohibited area D can be between 5° and 20°, for example, it can be 5°, 8°, 11°, 15°, 18°, and 20°. If the circumferential angle corresponding to the prohibited area D is too large, the feature area S will easily enter the prohibited area D, causing even cells that actually meet the performance requirements to be rejected. If the circumferential angle corresponding to the prohibited area D is too small, the two feature areas S will be close enough that a short circuit is likely to occur between the positive electrode tab P1 and the negative electrode tab P2, but the feature area S will still not enter the prohibited area D, resulting in defective products being released.

[0029] In one specific embodiment, the included angle b is set between 85° and 95°, for example, it can be 85°, 90° and 95°, so that the arrangement direction of the two feature regions S is close to or completely perpendicular to the reference line L1. Thus, each feature region S is theoretically located in the middle of the two forbidden regions D, so as to avoid one side of the feature region S being too tilted towards the reference line L1 and too easy to enter the forbidden region D.

[0030] In a specific embodiment, the arrangement direction of the two feature regions S refers to the direction of the line connecting the centroids K of the two feature regions S. For example, referring to Figure 3, the direction of the line L2 connecting the centroid K1 of the positive electrode feature region S1 and the centroid K2 of the negative electrode feature region S2 is taken as the arrangement direction of the positive electrode feature region S1 and the negative electrode feature region S2.

[0031] Referring to Figure 2, when identifying the two feature regions S, due to the redundancy in the length of the separator between the positive and negative electrode plates, the redundant part covers the end face 10 of the cell, making it difficult to distinguish the boundary between the tab P and the separator. If the line connecting the geometric centers of the inscribed rectangles of the feature regions S is chosen as the arrangement direction of the two feature regions S, it is difficult to determine the position of the inscribed rectangle. However, when determining the centroid K, the different edges of the feature regions S have an equal probability of offset error, which can cancel each other out. Theoretically, the position offset of the centroid K is small. Therefore, the position of the centroid K can be determined more accurately, and the line connecting the two centroids K can more accurately reflect the arrangement direction of the two feature regions S, making it less likely for the feature regions S to tilt to one side.

[0032] In one specific embodiment, determining the reference point O based on the end face image specifically includes: identifying the contour M of the end face 10, and using the center of the circumscribed circle or the center of the inscribed circle of the contour M of the end face 10 as the reference point O. During the winding process of the battery cell, various errors exist, resulting in the final contour M of the end face 10 not being a standard circle. Therefore, using the center of the circumscribed circle or the center of the inscribed circle of the contour M of the end face 10 as the reference point O can more accurately reflect the center position of the end face 10.

[0033] In a specific embodiment, each feature region S has two tangents passing through the reference point O. For example, referring to Figure 6, the positive electrode feature region S1 has tangents L6 and L7 passing through the reference point O, and the negative electrode feature region S2 has tangents L9 and L10 passing through the reference point O. The above method also includes: determining whether the angle between each tangent and the reference line L1 is within a first threshold range. If not, the cell is determined to be unqualified. If the angle between tangent L6 and the reference line L1 is too small, or the angle between tangent L7 and the reference line L1 is too large, it indicates that the positive electrode feature region S1 is too tilted to the side of tangent L6. The determination method for tangents L9 and L10 is the same.

[0034] The system determines whether the angle between adjacent tangents of two characteristic regions S is within the second threshold range. If not, the cell is deemed unqualified. For example, if the angle between the tangent L7 of the positive electrode characteristic region S1 and the tangent L9 of the negative electrode characteristic region S2 is too small, it indicates that the positive electrode characteristic region S1 and the negative electrode characteristic region S2 are too close, which may easily lead to a short circuit between the positive electrode tab P1 and the negative electrode tab P2. Therefore, the cell is deemed unqualified. The system also determines whether the angle between two tangents of each characteristic region S is within the third threshold range. If not, the cell is deemed unqualified. For example, if the angle between the tangents L6 and L7 of the positive electrode characteristic region S1 is too large, it indicates that the misalignment between the positive electrode sheets of different layers of the positive electrode characteristic region S1 may be too large. If the angle between the tangents L6 and L7 is too small, it indicates that the area of ​​the positive electrode characteristic region S1 that can be used to weld the current collector is too small. Therefore, the cell is deemed unqualified, which can prevent defective products from flowing out.

[0035] In one specific embodiment, the first threshold range is greater than or equal to 17.5° and less than or equal to 22.5°, for example, it can be 17.5°, 19°, 20°, 21° or 22.5°; the second threshold range is greater than or equal to 35° and less than or equal to 55°, for example, it can be 35°, 40°, 45°, 50° and 55°; the third threshold range is greater than or equal to 35° and less than or equal to 55°, for example, it can be 35°, 40°, 45°, 50° and 55°.

[0036] In a specific embodiment, each feature region S has an inner peripheral edge close to the reference point O and an outer peripheral edge away from the reference point O, and has a first center line and a second center line. The first center line is the line connecting the reference point O and the midpoint of the inner peripheral edge, and the second center line is the line connecting the reference point O and the midpoint of the outer peripheral edge. For example, referring to FIG7, the positive electrode feature region S1 has an inner peripheral edge V1 close to the reference point O and an outer peripheral edge V2 away from the reference point O. Both the inner peripheral edge V1 and the outer peripheral edge V2 are close to arc-shaped. The line connecting the reference point O and the inner peripheral edge V1 forms the first center line L4, and the line connecting the reference point O and the outer peripheral edge V2 forms the second center line L5. The above method further includes: determining whether the included angle between the first center line and the second center line of each feature region S is within the range of a fourth threshold. If not, the cell is determined to be unqualified. If the angle between the first center line L4 and the second center line L5 of the aforementioned positive electrode characteristic region S1 is too large, it indicates that during the winding process, the positional deviation between the outer ring positive electrode tab P1 and the inner ring positive electrode tab P1 is large, i.e., the alignment is poor. Therefore, this type of battery cell is judged as unqualified, which can prevent defective products from flowing out. The fourth threshold range can be greater than or equal to 0° and less than or equal to 20°, for example, it can be 0°, 5°, 10°, 15°, and 20°, etc. If the upper limit of the fourth threshold range is too large, it may lead to the outflow of battery cells with poor tab alignment.

[0037] In one specific embodiment, the method further includes: determining whether the ratio of the area of ​​each feature region S to the area of ​​the corresponding ideal tab region T is within a fourth threshold range; if not, the cell is determined to be unqualified. The two ideal tab regions T are symmetrically distributed on both sides of the reference line L1, and each ideal tab region T is spaced apart from the prohibited regions D on both sides in the circumferential direction, which is the direction surrounding the reference point O. For example, referring to Figures 4 and 8, the positive ideal tab region T1 corresponding to the positive feature region S1 and the negative ideal tab region T2 corresponding to the negative feature region S2 are symmetrically distributed on both sides of the reference line L1. The positive ideal tab region T1 is spaced apart from the prohibited regions D1 and D2 in the circumferential direction, and the negative ideal tab region T2 is spaced apart from the prohibited regions D1 and D2 in the circumferential direction. The degree of overlap between the positive electrode characteristic region S1 and the positive electrode ideal tab region T1 is determined by judging the proportion of the area of ​​the positive electrode characteristic region S1 to the area of ​​the positive electrode ideal tab region T1. If the area ratio is too small, it indicates that the positive electrode characteristic region S1 deviates too much from the positive electrode ideal tab region T1. Such cells are deemed unqualified, which can prevent defective cells from flowing out.

[0038] In one specific embodiment, each ideal tab region T is a sector centered at a reference point O. When there is no deviation between the inner and outer tabs P, the characteristic region S is also a sector. The sector structure of the ideal tab region T serves as a standard graphic for comparison with the characteristic region S, effectively reflecting the degree of deviation of the characteristic graphic. The circumferential angle corresponding to the ideal tab region T is between 40° and 50°, for example, it can be 40°, 45°, and 50°, etc. The axis of symmetry of the ideal tab region T is perpendicular to the reference line L1. Both the positive ideal tab region T1 and the negative ideal tab region T2 can be symmetrical about the vertical line L3, which passes through the reference point O and is perpendicular to the reference line L1.

[0039] In one specific embodiment, the fourth threshold range is greater than or equal to 80% and less than or equal to 100%, for example, it can be 80%, 85%, 90%, 95%, and 100%, etc. If the lower limit of the fourth threshold range is too small, it may result in the inability to reject cells with large deviations between the characteristic region S and the ideal tab region T, leading to defective products being released.

[0040] In one specific embodiment, the method further includes: determining whether the area of ​​each feature region S occupies the proportion of the area of ​​the corresponding danger region G within a fifth threshold range; if not, the cell is determined to be unqualified. Here, a danger region G is set at adjacent positions on both sides of each prohibited region D in the circumferential direction, with the circumferential direction being the direction surrounding the reference point O. For example, referring to Figures 4 and 9, a coordinate system is formed with the reference point O as the origin, reference line L1 as the horizontal axis, and vertical line L3 as the vertical axis. The four danger regions G are respectively danger region G1 in the first quadrant, danger region G2 in the second quadrant, danger region G3 in the third quadrant, and danger region G4 in the fourth quadrant. Taking the positive electrode feature region S1 as an example, if too much of the positive electrode feature region S1 is located in danger region G1 or danger region G2, i.e., its area proportion is too large, it indicates that at least one side of the positive electrode feature region S1 is too close to the negative electrode feature region S2, which can easily cause a short circuit. Such cells are determined to be unqualified, preventing defective products from flowing out.

[0041] In one specific embodiment, each danger zone G is a sector centered at a reference point O, with a corresponding circumferential angle between 5° and 20°, for example, 5°, 10°, 15°, and 20°. If the circumferential angle is too small, the feature area S will easily occupy too large a proportion of the danger zone G, and the feature area S will easily enter the prohibited zone D, causing qualified battery cells to be judged as unqualified, resulting in waste. If the circumferential angle is too large, it will excessively encroach on the space of the prohibited zone D or the ideal tab area T, causing qualified battery cells to be included in the defective products, or making it impossible to effectively remove defective products.

[0042] In one specific embodiment, the fifth threshold range is greater than or equal to 0 and less than or equal to 50%, for example, it can be 50%, 40%, 30%, 20% and 15%. If the upper limit is set too high, it may be impossible to remove defective products where the two feature regions S are too close together.

[0043] In a specific embodiment, when an ideal tab area T is provided between two prohibited areas D, the ideal tab area T is located between two dangerous areas G on the same side of the reference line L1 and is adjacent to the dangerous areas G. The characteristic area S is judged step by step by three levels of areas: the ideal tab area T, the dangerous area G that can be partially occupied, and the prohibited area D that is absolutely prohibited from being occupied. This can avoid over-rejection of cells that meet the usage requirements and also avoid the outflow of cells that do not meet the usage requirements, thus achieving a good balance between the two.

[0044] Referring to Figure 10, in a specific embodiment, the method further includes: determining whether each virtual welding area W is completely filled by the corresponding feature area S; if not, the cell is deemed unqualified. Two virtual welding areas W are symmetrically arranged on both sides of the reference line L1, spaced apart from it. Examples of virtual welding areas W are the positive virtual welding area W1 corresponding to the positive feature area S1 and the negative virtual welding area W2 corresponding to the negative feature area S2. If the virtual welding area W is not completely filled by the feature area S, it may cause the diaphragm welded to the end face 10 surface to short-circuit with the tab P and the electrode sheet of different polarities when welding the current collector and the tab P.

[0045] Based on the same inventive concept, this application also provides a battery cell testing device. The end face of the battery cell is provided with tabs P of opposite polarity. The battery cell testing device includes an image acquisition unit and a processing unit. The image acquisition unit is used to acquire an image of the end face of the battery cell, identify two feature regions S that are one-to-one with the tabs of the two polarities, and determine a reference point O at the center of the end face based on the end face image. The two feature regions S are arranged on both sides of the reference point O. The processing unit is used to adjust the end face image so that the arrangement direction of the two feature regions S forms a set angle b with the reference line L1. The reference line L1 passes through the reference point O. The processing unit determines whether the two feature regions S overlap with two prohibited regions D. If so, the battery cell is determined to be unqualified. The two prohibited regions D are located on the reference line L1 and are symmetrically distributed on both sides of the reference point O. The area adjacent to reference line L1 is designated as prohibited area D. If the positive characteristic area S1 overlaps with at least one of prohibited areas D1 and D2, or if the negative characteristic area S2 overlaps with at least one of prohibited areas D1 and D2, it means that the positive characteristic area S1 and the negative characteristic area S2 are too close together. This part of the battery cell is regarded as a seriously defective product and judged as unqualified, effectively screening out seriously defective products and preventing them from flowing out.

[0046] In one specific embodiment, each feature region S has two tangents passing through reference point O. For example, referring to FIG6, the positive electrode feature region S1 has tangents L6 and L7 passing through reference point O, and the negative electrode feature region S2 has tangents L9 and L10 passing through reference point O; the processing unit is further configured to:

[0047] Determine if the angle between each tangent and reference line L1 is within the first threshold range. If not, the cell is deemed unqualified. For example, if the angle between tangent L6 and reference line L1 is too small, or the angle between tangent L7 and reference line L1 is too large, it indicates that the positive electrode feature region S1 is tilted too far to one side of tangent L6. The determination method for tangents L9 and L10 is similar. Determine if the angle between adjacent tangents of two feature regions S is within the second threshold range. If not, the cell is deemed unqualified. For example, if the angle between tangent L7 of positive electrode feature region S1 and tangent L9 of negative electrode feature region S2 is too small, it indicates that the positive electrode feature region S1 is unqualified. If the distance between the positive electrode and the negative electrode feature area S2 is too close, a short circuit may easily occur between the positive electrode tab P1 and the negative electrode tab P2. Therefore, the cell is deemed unqualified. It is also necessary to determine whether the angle between the two tangents of each feature area S is within the third threshold range. If not, the cell is deemed unqualified. For example, if the angle between the tangents L6 and L7 of the positive electrode feature area S1 is too large, it indicates that the misalignment between the positive electrode sheets of different layers of the positive electrode feature area S1 may be too large. If the angle between the tangents L6 and L7 is too small, it indicates that the area of ​​the positive electrode feature area S1 that can be used to weld the current collector is too small. Therefore, the cell is deemed unqualified, which can prevent defective products from flowing out.

[0048] In a specific embodiment, each feature region S has an inner peripheral edge close to the reference point O and an outer peripheral edge away from the reference point O, and has a first center line and a second center line. The first center line is the line connecting the reference point O and the midpoint of the inner peripheral edge, and the second center line is the line connecting the reference point O and the midpoint of the outer peripheral edge. For example, referring to FIG7, the positive electrode feature region S1 has an inner peripheral edge V1 close to the reference point O and an outer peripheral edge V2 away from the reference point O. Both the inner peripheral edge V1 and the outer peripheral edge V2 are close to arc-shaped. The line connecting the reference point O and the inner peripheral edge V1 forms the first center line L4, and the line connecting the reference point O and the outer peripheral edge V2 forms the second center line L5. The processing unit is also used to: determine whether the angle between the first center line and the second center line of each feature region S is within the range of a fourth threshold. If not, the cell is determined to be unqualified. If the angle between the first center line L4 and the second center line L5 of the aforementioned positive electrode characteristic region S1 is too large, it indicates that during the winding process, the positional deviation between the outer ring positive electrode tab P1 and the inner ring positive electrode tab P1 is large, i.e., the alignment is poor. Therefore, this type of battery cell is judged as unqualified, which can prevent defective products from flowing out. The fourth threshold range can be greater than or equal to 0° and less than or equal to 20°, for example, it can be 0°, 5°, 10°, 15°, and 20°, etc. If the upper limit of the fourth threshold range is too large, it may lead to the outflow of battery cells with poor tab alignment.

[0049] In a specific embodiment, the processing unit is further configured to: determine whether the ratio of the area of ​​each feature region S to the area of ​​the corresponding ideal tab region T is within a fourth threshold range; if not, the cell is determined to be unqualified. The two ideal tab regions T are symmetrically distributed on both sides of the reference line L1, and each ideal tab region T is spaced apart from the prohibited regions D on both sides in the circumferential direction, which is the direction surrounding the reference point O. For example, referring to Figures 4 and 8, the positive ideal tab region T1 corresponding to the positive feature region S1 and the negative ideal tab region T2 corresponding to the negative feature region S2 are symmetrically distributed on both sides of the reference line L1. The positive ideal tab region T1 is spaced apart from the prohibited regions D1 and D2 in the circumferential direction, and the negative ideal tab region T2 is spaced apart from the prohibited regions D1 and D2 in the circumferential direction. The degree of overlap between the positive electrode characteristic region S1 and the positive electrode ideal tab region T1 is determined by judging the proportion of the area of ​​the positive electrode characteristic region S1 to the area of ​​the positive electrode ideal tab region T1. If the area ratio is too small, it indicates that the positive electrode characteristic region S1 deviates too much from the positive electrode ideal tab region T1. Such cells are deemed unqualified, which can prevent defective cells from flowing out.

[0050] In a specific embodiment, the processing unit is further configured to: determine whether the area of ​​each feature region S occupies the proportion of the area of ​​the corresponding danger region G within a fifth threshold range; if not, the cell is determined to be unqualified. Here, a danger region G is set at adjacent positions on both sides of each prohibited region D in the circumferential direction, with the circumferential direction being the direction surrounding the reference point O. For example, referring to Figures 4 and 9, a coordinate system is formed with the reference point O as the origin, reference line L1 as the horizontal axis, and vertical line L3 as the vertical axis. The four danger regions G are respectively danger region G1 in the first quadrant, danger region G2 in the second quadrant, danger region G3 in the third quadrant, and danger region G4 in the fourth quadrant. Taking the positive electrode feature region S1 as an example, if too much of the positive electrode feature region S1 is located in danger region G1 or danger region G2, i.e., its area proportion is too large, it indicates that at least one side of the positive electrode feature region S1 is too close to the negative electrode feature region S2, which can easily cause a short circuit. Such cells are determined to be unqualified, preventing defective products from flowing out.

[0051] In one specific embodiment, the processing unit is further configured to: determine whether each virtual welding area W is completely filled by the corresponding feature area S; if not, determine that the cell is unqualified. The two virtual welding areas W are symmetrically arranged on both sides of the reference line L1 and spaced apart from the reference line L1. If the virtual welding area W is not completely filled by the feature area S, it may cause the diaphragm welded to the end face 10 surface to short-circuit with the tab P and the electrode sheet of different polarity when welding the current collector and the tab P.

[0052] Based on the same inventive concept, this application also provides a cell correction method based on the cell detection method provided in the above embodiments. The cell correction method includes: when the absolute value of the difference between the initial angle a and the set angle b is greater than 0, controlling the driving component to drive the cell to rotate by the angle of the difference to perform preliminary correction of the cell. The rotation direction of the cell is the same as the rotation direction of the end face image. The initial angle refers to the angle between the arrangement direction of the two feature regions S before the end face image is rotated and the reference line L1. When the parts of interest of the two feature regions S are located on the same side of the reference point O in the direction of the reference line L1, the cell is rotated so that the areas of the parts of interest of the two feature regions S are equal or the corresponding circumferential angles are the same. Thus, the alignment deviation of the cell is distributed to the two feature regions, so that the positional deviation of the two feature regions is minimized. The circumferential angle corresponding to each part of interest refers to the tangent of the part of interest through the reference point O. The angle between the line and the boundary of the corresponding danger zone G, such as the angle d formed by the tangent L0 of the positive electrode feature region S located in the part of concern in danger zone G1 and the corresponding boundary of danger zone G1, is the circumferential angle corresponding to the part of concern of the positive electrode feature region S1; or, when the parts of concern of two feature regions S are located on different sides of the reference point O in the direction of the reference line L1, the cell is rotated so that the area of ​​the feature region S in the four danger zones G tends to be close, thereby dispersing the alignment deviation of the cell to the two feature regions and minimizing the positional deviation of the two feature regions; where the part of concern refers to the larger part of the overlapping area between each feature region S and the two danger zones G, for example, if the area of ​​the positive electrode feature region S1 overlapping with danger zone G1 is larger than the area of ​​the overlapping area with danger zone G2, then the part of the positive electrode feature region S1 overlapping with danger zone G1 is the part of concern of the positive electrode feature region S1.

[0053] For example, referring to Figure 11, in a specific battery cell production line, the following steps are performed sequentially:

[0054] S1. A battery cell is formed by winding an electrode assembly using a winding mechanism. The electrode assembly includes positive and negative electrodes arranged alternately in sequence. A diaphragm is provided between the positive and negative electrodes. The battery cell tab P formed by winding stands on the end face 10 of the battery cell and has not yet been flattened.

[0055] S2. The wound battery cells are fed into a conveying mechanism, such as a conveyor belt;

[0056] S3. After the battery cell is transferred to the first inspection station, the battery cell is tested for whether it is qualified using the above battery cell inspection method. If it is not qualified, step S31 is executed to discard the unqualified battery cell; otherwise, step S4 is executed.

[0057] S4. The battery cell is corrected using the battery cell correction method provided in the above embodiment so that the electrode tab P can be aligned with the flattening mechanism;

[0058] S5. Control the flattening mechanism to flatten the tab P. For example, the tab P is gradually pushed down from the periphery to the reference point O along the radial direction of the end face 10 of the cell by the flattening structure with an arc notch. The tab P lies on the end face 10 of the cell to facilitate subsequent welding with the current collector.

[0059] S6. After the battery cell is transferred to the second inspection station, the battery cell is inspected for qualification using the above battery cell inspection method. If it is not qualified, step S61 is executed to discard the unqualified battery cell; otherwise, step S7 is executed.

[0060] S7. The battery cell is corrected using the battery cell correction method provided in the above embodiment so that the electrode tab P can be rotated to the angle required for unloading. The correction mechanism can be a battery cell picking robot arm.

[0061] In particular, both steps S3 and S6 can be detected using a CCD (Charge-Coupled Device).

[0062] When performing the above-described cell detection method in step S3, an image acquisition unit as shown in Figure 12 can be used. Referring to Figure 12, the image acquisition unit includes a camera 03 and a light source 02. The camera 03 can be an industrial area array camera with the aforementioned charge-coupled device, and is positioned facing the end face 10 of the cell 01. The camera 03 and the light source 02 can be coaxially positioned with the cell 01, and the light source 02 has a channel in the middle for light to be transmitted to the camera 03. Here, the light source 02 can be a 0° blue ring light source so that the edge of the standing tab P can reflect light, thereby facilitating the identification of the characteristic region S of the tab P. The distance from the light source 02 to the end face 10 can be between 5mm and 20mm, for example, 5mm, 10mm, 15mm, and 20mm. If the distance is too close, it may cause interference between the light source 02 and the tab P, making it difficult for the camera 03 to capture the edge of the tab P. If the distance is too large, the light from the light source 02 will have difficulty illuminating the edge of the tab P.

[0063] When performing the above-described cell detection method in step S6, an image acquisition unit as shown in Figure 13 can be used. Referring to Figure 13, the difference between the image acquisition unit shown in Figure 12 and the one shown in Figure 13 is that the camera 03 can be an industrial FA (Factory Automation) lens, and the light source 02 is a spherical integrating light source, so that the light can evenly illuminate the end face 10 of the cell 01, and the flattened tab P can reflect light evenly.

[0064] Furthermore, in steps S3 and S6, the overall offset trend of the tab P can be statistically determined based on the detection results of multiple cells, and this offset trend can be fed back to the winding mechanism for adaptive correction.

[0065] Obviously, those skilled in the art can make various modifications and variations to the embodiments of the present invention without departing from the spirit and scope of the invention. Therefore, if these modifications and variations fall within the scope of the claims of the present invention and their equivalents, the present invention also intends to include these modifications and variations.

Claims

1. A method of detecting a battery cell, the method comprising: The end face of the battery cell is provided with tabs of opposite polarity; The method includes: The end face image of the battery cell is acquired, and two feature regions corresponding to the two polarities are identified one-to-one. The reference point of the end face center is determined based on the end face image, wherein the two feature regions are located on both sides of the reference point. Rotate the end face image so that the arrangement direction of the two feature regions forms a set angle with the reference line, and the reference line passes through the reference point; If it is determined whether the two feature regions overlap with the two prohibited regions, the battery cell is deemed unqualified. The two prohibited regions are located on the reference line and are symmetrically distributed on both sides of the reference point.

2. The method of claim 1, wherein, Each prohibited area is a sector centered on the reference point and with the reference line as the axis of symmetry, and the circumferential angle corresponding to the prohibited area is between 5° and 20°.

3. The method of claim 1, wherein, The set included angle is between 85° and 95°.

4. The method of claim 1, wherein, The arrangement direction of the two feature regions refers to the direction of the line connecting the centroids of the two feature regions.

5. The method of claim 1, wherein, Determining the reference point based on the end face image specifically includes: The contour of the end face is identified, and the center of the circumcircle or the center of the incircle of the contour of the end face is used as the reference point.

6. The method of claim 1, wherein, Each of the aforementioned feature regions has two tangent lines passing through the reference point; The method further includes: Determine whether the angle between each tangent line and the reference line is within the first threshold range; if not, determine that the battery cell is unqualified. Determine whether the included angle between adjacent tangents of two feature regions is within a second threshold range; if not, determine that the battery cell is unqualified. Determine whether the included angle between the two tangents of each feature region is within the range of a third threshold. If not, the battery cell is determined to be unqualified.

7. The method of claim 6, wherein, The first threshold range is greater than or equal to 17.5° and less than or equal to 22.5°; The second threshold range is greater than or equal to 35° and less than or equal to 55°; The third threshold range is greater than or equal to 35° and less than or equal to 55°.

8. The method of claim 1, wherein, Each of the feature regions has an inner peripheral edge close to the reference point and an outer peripheral edge away from the reference point, and has a first center line and a second center line, wherein the first center line is the line connecting the reference point and the midpoint of the inner peripheral edge, and the second center line is the line connecting the reference point and the midpoint of the outer peripheral edge; The method further includes: Determine whether the angle between the first and second midlines of each of the aforementioned feature regions is within the range of the fourth threshold. If not, the battery cell is determined to be unqualified.

9. The method of claim 8, wherein, The fourth threshold range is greater than or equal to 0° and less than or equal to 20°.

10. The method of claim 1 to 9, wherein, The method further includes: Determine whether the area of ​​each of the aforementioned feature regions is within the range of the fourth threshold. If not, the battery cell is deemed unqualified. The two aforementioned ideal electrode regions are symmetrically distributed on both sides of the reference line, and each of the aforementioned ideal electrode regions is spaced apart from the prohibited regions on both sides in the circumferential direction. The circumferential direction is the direction surrounding the reference point.

11. The method of claim 10, wherein, Each of the ideal electrode regions is a sector centered at the reference point, with a corresponding circumferential angle between 40° and 50°, wherein the axis of symmetry of the ideal electrode region is perpendicular to the reference line.

12. The method of claim 10, wherein, The fourth threshold range is greater than or equal to 80% and less than or equal to 100%.

13. The method of claim 1 to 12, wherein, The method further includes: Determine whether the area of ​​each of the aforementioned feature regions is within the range of the corresponding danger region. If not, the battery cell is deemed unqualified. Here, a danger region is set at the adjacent positions on both sides of each of the prohibited regions in the circumferential direction, where the circumferential direction is the direction surrounding the reference point.

14. The method of claim 13, wherein, Each of the aforementioned danger zones is a sector centered on the reference point, with the corresponding circumferential angle between 5° and 20°.

15. The method of claim 13, wherein, The fifth threshold range is greater than or equal to 0 and less than or equal to 50%.

16. The method of claim 13, wherein, When an ideal electrode area is provided between two prohibited areas, the ideal electrode area is located between two dangerous areas on the same side of the reference line and is adjacent to the dangerous areas.

17. The method of claim 1 to 16, wherein, The method further includes: Determine whether each virtual welding area is completely filled by the corresponding feature area. If not, the battery cell is determined to be unqualified. The two virtual welding areas are symmetrically arranged on both sides of the reference line and are spaced apart from the reference line.

18. An electric cell detection apparatus, characterized by comprising: The end face of the battery cell is provided with tabs of opposite polarity; The battery cell testing device includes: an image acquisition unit and a processing unit; The image acquisition unit is used to acquire an end face image of the battery cell, identify two feature regions that are one-to-one with the tabs of the two polarities respectively, and determine a reference point at the center of the end face based on the end face image, wherein the two feature regions are arranged on both sides of the reference point. The processing unit is used to adjust the end face image so that the arrangement direction of the two feature regions forms a set angle with the reference line, the reference line passes through the reference point, and determine whether the two feature regions overlap with the two prohibited regions. If so, the cell is determined to be unqualified. The two prohibited regions are located on the reference line and are symmetrically distributed on both sides of the reference point.

19. The battery cell detection apparatus of claim 18, wherein, Each of the aforementioned feature regions has two tangent lines passing through the reference point; The processing unit is also used for: Determine whether the angle between each tangent line and the reference line is within the first threshold range; if not, determine that the battery cell is unqualified. Determine whether the included angle between adjacent tangents of two feature regions is within a second threshold range; if not, determine that the battery cell is unqualified. Determine whether the included angle between the two tangents of each feature region is within the range of a third threshold. If not, the battery cell is determined to be unqualified.

20. The battery cell detection apparatus of claim 18, wherein, Each of the feature regions has an inner peripheral edge close to the reference point and an outer peripheral edge away from the reference point, and has a first center line and a second center line, wherein the first center line is the line connecting the reference point and the midpoint of the inner peripheral edge, and the second center line is the line connecting the reference point and the midpoint of the outer peripheral edge; The processing unit is also used for: Determine whether the angle between the first and second midlines of each of the aforementioned feature regions is within the range of the fourth threshold. If not, the battery cell is determined to be unqualified.

21. The battery cell detection apparatus of claim 18, wherein, The processing unit is also used for: Determine whether the area of ​​each of the aforementioned feature regions is within the range of the fourth threshold. If not, the battery cell is deemed unqualified. The two aforementioned ideal electrode regions are symmetrically distributed on both sides of the reference line, and each of the aforementioned ideal electrode regions is spaced apart from the prohibited regions on both sides in the circumferential direction. The circumferential direction is the direction surrounding the reference point.

22. The battery cell detection apparatus of claim 18, wherein, The processing unit is also used for: Determine whether the area of ​​each of the aforementioned feature regions is within the range of the corresponding danger region. If not, the battery cell is deemed unqualified. Here, a danger region is set at the adjacent positions on both sides of each of the prohibited regions in the circumferential direction, where the circumferential direction is the direction surrounding the reference point.

23. The battery cell detection apparatus of claim 18, wherein, The processing unit is also used for: Determine whether each virtual welding area is completely filled by the corresponding feature area. If not, the battery cell is determined to be unqualified. The two virtual welding areas are symmetrically arranged on both sides of the reference line and are spaced apart from the reference line.

24. A cell correction method based on the cell detection method according to any one of claims 13 to 16, characterized by, include: When the absolute value of the difference between the initial angle and the set angle is greater than 0, the control drive component drives the battery cell to rotate by the difference angle. The rotation direction of the battery cell is the same as the rotation direction of the end face image. The initial angle refers to the angle between the arrangement direction of the two feature regions of the end face image before rotation and the reference line. When the areas of interest in the two said feature regions are located on the same side of the reference point in the direction of the reference line, the cell is rotated so that the areas of the areas of interest in the two said feature regions are equal or their corresponding circumferential angles are the same; or... When the parts of interest of the two said feature regions are located on different sides of the reference point in the direction of the reference line, the cell is rotated so that the areas of the feature regions in the four said danger zones tend to be close; The "part of interest" refers to the larger portion of the overlapping area between each of the feature regions and the danger zones on both sides.

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