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

Abstract

The present invention relates to the field of battery technology, and discloses a battery cell detection method, a battery cell detection device and a battery cell correction method. The battery cell detection method comprises: obtaining an end face image of a battery cell, identifying two characteristic areas corresponding to two polarity tabs one to one, determining a reference point of the end face center according to the end face image, and the two characteristic areas are arranged on both sides of the reference point; rotating the end face image so that the arrangement direction of the two characteristic areas forms a set angle with a reference line, and the reference line passes through the reference point, and first preliminarily adjusting the angle of the end face image so that theoretically, the two tabs with opposite polarities are centered between two prohibited areas, and the two will not overlap with the two prohibited areas when the alignment meets the requirements; judging whether the two characteristic areas overlap with the two prohibited areas, and if so, judging that the battery cell is unqualified, and preventing the battery cell with poor alignment from flowing out, and the two prohibited areas are located on the reference line and symmetrically distributed on both sides of the reference point.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a battery cell detection method, a battery cell detection device, and a battery cell deviation correction method. Background Art

[0002] During the production of cylindrical battery cells (such as top-flow cylindrical batteries), the positive and negative tabs are placed on the same side of the cell. However, during the winding process, the tabs may deviate from the ideal position, resulting in tab alignment that is not within an appropriate range. This can lead to safety issues such as cell short circuits, excessive internal resistance, and poor appearance. However, traditional technical solutions have difficulty effectively detecting tab alignment. Summary of the Invention

[0003] The invention discloses a battery cell detection method, a battery cell detection device and a battery cell deviation correction method, which are used for effectively detecting the alignment of tabs.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] In a first aspect, a method for detecting a battery cell is provided, wherein an end face of the battery cell is provided with tabs with opposite polarities; the method comprises: obtaining an end face image of the battery cell, identifying two characteristic areas corresponding one to one with the tabs of two polarities, and determining a reference point of the center of the end face based on the end face image, wherein the two characteristic areas are arranged on both sides of the reference point; rotating the end face image so that the arrangement direction of the two characteristic areas is at a set angle to a reference line, and the reference line passes through the reference point, and first preliminarily adjusting the angle of the end face image so that theoretically the two tabs of opposite polarity are centered between the two prohibited areas, and the two will not overlap with the two prohibited areas when the alignment meets the requirements; judging whether the two characteristic areas overlap with the two prohibited areas, and if so, judging that the battery cell is unqualified, wherein the two prohibited areas 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. Once two characteristic areas overlap with the prohibited area, it indicates that the two characteristic areas are at risk of being too close to each other and have poor alignment. These battery cells will be considered as seriously defective products and judged as unqualified, effectively screening out seriously defective products and preventing them from flowing out.

[0006] In a second aspect, a battery cell detection device is provided, wherein the end face of the battery cell is provided with tabs with opposite polarities; the battery cell detection device comprises: an image acquisition unit and a processing unit; the image acquisition unit is used to acquire the end face image of the battery cell, identify two characteristic areas corresponding to the two polarity tabs one to one, and determine the reference point of the end face center according to the end face image, wherein the two characteristic areas 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 characteristic areas is at a set angle to a reference line, and the reference line passes through the reference point, and judge whether the two characteristic areas overlap with two prohibited areas. If so, the battery cell is judged to be unqualified, wherein the two prohibited areas are located on the reference line and are symmetrically distributed on both sides of the reference point.

[0007] The advantages of the battery cell detection device and the above-mentioned battery cell detection method over the prior art are the same, and will not be repeated here.

[0008] In a third aspect, a cell correction method based on the cell detection method according to any one of the technical solutions 13 to 16 above comprises: when the absolute value of the difference between the initial angle and the set angle is greater than 0, controlling the driving component to drive the cell to rotate by the angle of the difference, and the rotation direction of the cell is the same as the rotation direction of the end face image, so as to perform preliminary correction on the cell, wherein the initial angle refers to the angle between the arrangement direction of the two feature areas before the end face image is rotated and the reference line; when the focus portions of the two feature areas are located on the same side of the reference point in the direction of the reference line, rotating the cell so that the focus portions of the two feature areas are equal in area or The corresponding circular angles are the same, so that the alignment deviation of the battery cell is dispersed to the two characteristic areas, so that the position deviation of the two characteristic areas is minimized; or, when the focus parts of the two characteristic areas are located on different sides of the reference point in the direction of the reference line, the battery cell is rotated to make the characteristic area areas of the four dangerous areas tend to be close, so that the alignment deviation of the battery cell is dispersed to the two characteristic areas, so that the position deviation of the two characteristic areas is minimized, so that the alignment deviation of the battery cell is dispersed to the two characteristic areas, so that the position deviation of the two characteristic areas is minimized; wherein, the focus part refers to the larger part of the overlapping part of each characteristic area with the dangerous areas on both sides. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 A schematic diagram of an end face image obtained in the battery cell detection method provided in an embodiment of the present application;

[0010] Figure 2A schematic diagram of identifying a characteristic area S in the battery cell detection method provided in an embodiment of the present application;

[0011] Figure 3 A schematic diagram showing a rotated end face image in a battery cell detection method provided in an embodiment of the present application;

[0012] Figure 4 Express Figure 3 Schematic diagram of region division of the image shown;

[0013] Figure 5 express Figure 4 Position relationship diagram of the forbidden area D and the feature area S;

[0014] Figure 6 express Figure 4 Schematic diagram of the tangent position relationship of the characteristic area S;

[0015] Figure 7 A schematic diagram showing the positional relationship between the first midline and the second midline of the feature area S;

[0016] Figure 8 express Figure 4 Positional relationship diagram of the ideal area T and characteristic area S of the middle tab;

[0017] Figure 9 express Figure 4 Position relationship diagram of the middle tab danger area G and characteristic area S;

[0018] Figure 10 express Figure 3 Position relationship diagram of each characteristic area S and the corresponding virtual welding area W;

[0019] Figure 11 A flow chart showing an application scenario of the battery cell detection method and the battery cell deviation correction method provided in an embodiment of the present application;

[0020] Figure 12 express Figure 11 A schematic structural diagram of the image acquisition unit used in step S3;

[0021] Figure 13 express Figure 11 Schematic diagram of the structure of the image acquisition unit used in step S6. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] In order to have a clearer understanding of the cell detection method provided in the embodiment of the present application, its background is briefly introduced below. The cell of a cylindrical battery (such as a top-flow cylindrical battery) can be a wound cell, for example, by winding the positive electrode sheets and the negative electrode sheets that are alternately stacked in sequence to form a roughly cylindrical wound cell, wherein a diaphragm is provided between adjacent positive electrode sheets and negative electrode sheets for insulating the positive electrode sheets and the negative electrode sheets, and in order to form good insulation, the length of the diaphragm can be greater than the length of the positive electrode sheets and the negative electrode sheets.

[0024] refer to Figure 1 The end face 10 of the wound battery cell is provided with a tab P with opposite polarity, and the tab P may include a plurality of positive tabs P1 connected to the positive electrode sheet (refer to Figure 1 ) and multiple negative electrode tabs P2 connected to the negative electrode sheet, the positive electrode tab P1 and the negative electrode tab P2 are arranged on the same side of the battery cell; for example, the material of the positive electrode tab P1 can be copper, and the material of the negative electrode tab P2 can be aluminum, but not limited to this, the material of the positive electrode tab P1 and the negative electrode tab P2 can be adjusted as needed.

[0025] Before winding, the above multiple positive electrode tabs P1 (reference Figure 1 ) are sequentially spaced at the edge of the positive electrode sheet, and multiple negative electrode tabs P2 (reference Figure 1 ) are sequentially spaced at the edge of the negative electrode tab. After the battery cell is wound and formed, the multiple positive electrode tabs P1 corresponding to the positive electrode tabs from the inner layer to the outer layer should theoretically be aligned within a reasonable range, and the negative electrode tabs P2 should also meet similar requirements. However, during the actual winding process, the inner positive electrode tab P1 and the outer positive electrode tab P1 are prone to misalignment, which in turn causes the positive electrode tab P1 to gradually shift, and the alignment fails to meet the requirements. This may cause the distance between the positive electrode tab P1 and the negative electrode tab P2 to be too close, leading to safety issues such as battery cell short circuits, excessive internal resistance, and poor appearance.

[0026] In order to solve the above problems, the battery cell detection method provided in the embodiment of the present application includes: Figure 1 , obtain the end face image of the battery cell, and then refer to Figure 2, identify two characteristic regions S corresponding to the two polarity tabs P one to one, such as the two characteristic regions S are the positive characteristic region S1 corresponding to the positive tab P1, and the negative characteristic region S2 corresponding to the negative tab P2, and determine the reference point O at the center of the end face according to the end face image, wherein the two characteristic regions S are arranged on both sides of the reference point O, and the reference point O is used as a reference point in subsequent steps; reference Figure 3 , rotate the end face image so that the arrangement direction of the two characteristic areas S forms a set angle b with the reference line L1, and the reference line L1 passes through the reference point O. In this step, the angle of the end face image is first preliminarily adjusted so that theoretically the positive electrode tab P1 and the negative electrode tab P2 are centered between the two prohibited areas D. When the alignment meets the requirements, the two will not overlap with the two prohibited areas D; next, determine whether the two characteristic areas S overlap with the two prohibited areas D. If so, the battery cell is determined to be unqualified, wherein the two prohibited areas D are located on the reference line L1 and are symmetrically distributed on both sides of the reference point O, with the prohibited area D1 located to the left of the reference point O and the prohibited area D2 located to the right of the reference point O. The area adjacent to the reference line L1 is designated as a prohibited area D. Once the positive characteristic area S1 overlaps with at least one of the prohibited areas D1 and D2, or the negative characteristic area S2 overlaps with at least one of the prohibited areas D1 and D2, it means that the positive characteristic area S1 and the negative characteristic area S2 are at risk of being too close to each other. These battery cells are then deemed to be severely defective products and are judged as unqualified, effectively screening out severely defective products and preventing them from flowing out. After performing the aforementioned rotation of the end-face image and preliminarily adjusting the angle of the end-face image, the positive characteristic area S1 can be located above the reference L1, while the negative characteristic area S2 is located below the reference L1. Furthermore, an additional detection step can be added: judging whether the positive characteristic area S1 and the negative characteristic area S2 conform to the aforementioned rules based on the colors of the two characteristic areas S. If not, the battery cell is judged to be unqualified.

[0027] Combine Figure 4 and Figure 5 In a specific embodiment, each forbidden area D is a sector with the reference point O as the center and the reference line L1 as the axis of symmetry. Figure 5In the figure, both are fan-shaped and symmetrical about the reference line L1. Theoretically, after the battery cell is wound, multiple positive electrode tabs P1 form a fan-shaped area with the reference point O as the center of the circle, and multiple negative electrode tabs P2 also form a fan-shaped area with the reference point O as the center of the circle. Therefore, the two characteristic areas S are theoretically fan-shaped; the prohibited area D is also fan-shaped and is set in the above manner. The two prohibited areas D can theoretically be located exactly in the middle of the positive characteristic area S1 and the negative characteristic area S2, and adapt to the fan-shaped shape of the characteristic area S, which has a relatively balanced warning effect on the two characteristic areas S. The so-called "theoretically" refers to the situation where the positive electrode tab P1 and the negative electrode tab 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°, etc. If the circumferential angle corresponding to the prohibited area D is too large, the characteristic area S will enter the prohibited area D too easily, causing the battery cells that actually meet the performance requirements to be eliminated. If the circumferential angle corresponding to the prohibited area D is too small, the two characteristic areas S will be close enough, and the positive electrode tab P1 and the negative electrode tab P2 will be prone to short circuit, but the characteristic area S will still not enter the prohibited area D, resulting in the outflow of defective products.

[0028] In a specific embodiment, the 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 areas S is close to perpendicular to the reference line L1 or completely perpendicular to the reference line L1. Therefore, each feature area S is theoretically located in the center of the two prohibited areas D to avoid one side of the feature area S being too tilted toward the reference line L1 and too easily entering the prohibited area D.

[0029] 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 characteristic region S1 and the centroid K2 of the negative characteristic region S2 is used as the arrangement direction of the positive characteristic region S1 and the negative characteristic region S2.

[0030] refer to Figure 2When identifying the two characteristic regions S, due to the redundant length of the separator between the positive and negative pole pieces, the redundant portion covers the end face 10 of the battery 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 characteristic regions S is chosen as the arrangement direction of the two characteristic regions S, it is difficult to determine the position of the inscribed rectangles. However, when determining the centroid K, the offset errors of the different edges of the characteristic region S have equal probability and can offset each other. In theory, the position offset of the centroid K is smaller. Therefore, the position of the centroid K can be determined more accurately. The line connecting the two centroids K can more accurately reflect the arrangement direction of the two characteristic regions S, and the characteristic region S is less likely to tilt to one side.

[0031] In a 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 a circumscribed circle or an inscribed circle of the contour M of the end face 10 as the reference point O. Due to various errors during the winding process of the battery cell, the contour M of the end face 10 may not be a perfect circle. Therefore, using the center of the circumscribed circle or 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.

[0032] In a specific embodiment, each feature region S has two tangent lines passing through the reference point O, for example, Figure 6 , the positive characteristic region S1 has a tangent L6 and a tangent L7 passing through the reference point O, and the negative characteristic region S2 has a tangent L9 and a tangent L10 passing through the reference point O; the above method also includes: judging whether the angle between each tangent and the reference line L1 is within the first threshold range, if not, the battery cell is judged to be unqualified, if the angle between the tangent L6 and the reference line L1 is too small, or the angle between the tangent L7 and the reference line L1 is too large, it indicates that the positive characteristic region S1 is too inclined to one side of the tangent L6, and the judgment method of the tangent L9 and the tangent L10 is similar.

[0033] Determine whether the angle between adjacent tangents of two characteristic regions S is within the second threshold range. If not, the battery cell is determined to be unqualified. For example, if the angle between the tangent L7 of the positive characteristic region S1 and the tangent L9 of the negative characteristic region S2 is too small, it indicates that the positive characteristic region S1 and the negative characteristic region S2 are too close, and a short circuit between the positive electrode tab P1 and the negative electrode tab P2 is likely to occur. Therefore, the battery cell is determined to be unqualified. Determine whether the angle between the two tangents of each characteristic region S is within the third threshold range. If not, the battery cell is determined to be unqualified. For example, if the angle between the tangent L6 and the tangent L7 of the positive characteristic region S1 is too large, it indicates that the misalignment between the positive electrode sheets of different layers of the positive characteristic region S1 may be too large. If the angle between the tangent L6 and the tangent L7 is too small, it indicates that the area of ​​the positive characteristic region S1 that can be used for welding the current collecting plate is too small. Therefore, the battery cell is determined to be unqualified, which can prevent the outflow of defective products.

[0034] In a 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°, etc.; 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°, etc.

[0035] 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 a line connecting the reference point O and the midpoint of the inner peripheral edge, and the second center line is a line connecting the reference point O and the midpoint of the outer peripheral edge; for example, referring to Figure 7The positive electrode characteristic 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, and both the inner peripheral edge V1 and the outer peripheral edge V2 are close to an arc shape. The line connecting the reference point O and the inner peripheral edge V1 forms a first center line L4, and the line connecting the reference point O and the outer peripheral edge V2 forms a second center line L5. The above method also includes: determining whether the angle between the first center line and the second center line of each characteristic region S is within a fourth threshold range. If not, the battery cell is determined to be unqualified. If the angle between the first center line L4 and the second center line L5 of the above-mentioned positive electrode characteristic region S1 is too large, it indicates that during the winding process of the battery cell, the positional deviation between the outer ring positive electrode tab P1 and the inner ring positive electrode tab P1 is large, that is, the alignment is poor. Therefore, this type of battery cell is determined to be unqualified, which can prevent the outflow of defective products. Among them, 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 value of the fourth threshold range is too large, it may cause the battery cell with poor alignment of the tab P to flow out.

[0036] In a specific embodiment, the method further includes: determining whether the ratio of the area of ​​each characteristic region S to the area of ​​the corresponding ideal tab region T is within a fourth threshold range, and if not, determining that the battery cell is unqualified, wherein 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 areas D on both sides in the circumferential direction, and the circumferential direction is the direction around the reference point O. For example, reference Figure 4 and Figure 8 The positive electrode ideal tab region T1 corresponding to the positive electrode characteristic region S1 and the negative electrode ideal tab region T2 corresponding to the negative electrode characteristic region S2 are symmetrically distributed on both sides of the reference line L1. The positive electrode ideal tab region T1 is circumferentially spaced apart from the prohibited region D1 and the prohibited region D2, respectively. The negative electrode ideal tab region T2 is circumferentially spaced apart from the prohibited region D1 and the prohibited region D2, respectively. The degree of overlap between the positive electrode characteristic region S1 and the positive electrode ideal tab region T1 is determined by determining the ratio 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 significantly from the positive electrode ideal tab region T1, and the battery cell is deemed unqualified, thus preventing the discharge of defective batteries.

[0037] In a specific embodiment, each ideal tab region T is a sector with a reference point O as its center. When there is no deviation between the inner and outer tabs P, the characteristic region S is a sector. The sector structure of the ideal tab region T serves as a standard pattern for comparison with the characteristic region S, effectively providing feedback on the degree of deviation of the characteristic pattern. The circumferential angle corresponding to the ideal tab region T is between 40° and 50°, for example, 40°, 45°, and 50°, wherein the axis of symmetry of the ideal tab region T is perpendicular to the reference line L1. The positive electrode ideal tab region T1 and the negative electrode ideal tab region T2 can both be patterns symmetrical about a vertical line L3, which passes through the reference point O and is perpendicular to the reference line L1.

[0038] In a 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%. If the lower limit of the fourth threshold range is too small, it may result in the inability to reject cells with a large deviation between the characteristic area S and the ideal tab area T, resulting in the outflow of defective products.

[0039] In a specific embodiment, the method further includes: determining whether the area ratio of each characteristic region S to the area ratio of the corresponding dangerous region G is within a fifth threshold range; if not, determining that the battery cell is unqualified, wherein a dangerous region G is set at adjacent positions on both sides of each prohibited region D in the circumferential direction, and the circumferential direction is the direction surrounding the reference point O. For example, referring to Figure 4 and Figure 9 , with reference point O as the origin, reference line L1 as the horizontal axis, and vertical line L3 as the vertical axis, forming a coordinate system. The four danger zones G are: danger zone G1 in the first quadrant, danger zone G2 in the second quadrant, danger zone G3 in the third quadrant, and danger zone G4 in the fourth quadrant. Taking the positive characteristic region S1 as an example, if too much of the positive characteristic region S1 lies within danger zone G1 or danger zone G2, i.e., if the area occupies too large a proportion, this indicates that at least one side of the positive characteristic region S1 is too close to the negative characteristic region S2, which could easily cause a short circuit. Such cells will be judged as unqualified, thus preventing the outflow of defective products.

[0040] In a specific embodiment, each danger zone G is a sector with the reference point O as the center, and the corresponding circumferential angle is between 5° and 20°, for example, 5°, 10°, 15°, and 20°. If the circumferential angle is too small, the characteristic area S is likely to occupy too large an area in the danger zone G, and the characteristic area S is likely to enter the prohibited area D, causing batteries that meet the use requirements to be judged as unqualified, resulting in waste. If the circumferential angle is too large, it will occupy too much space in the prohibited area D or the ideal area T of the tab, causing qualified batteries to be classified as defective, or failing to effectively eliminate defective batteries.

[0041] In a 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 value is set too high, defective products whose two feature areas S are too close to each other may not be eliminated.

[0042] 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 the two dangerous areas G on the same side of the reference line L1 and is arranged adjacent to the dangerous area G. The three-level areas of the ideal tab area T, the dangerous area G that allows partial occupation and the prohibited area D that is absolutely prohibited from occupation are used to judge whether the characteristic area S is in a suitable position step by step. This can avoid excessive elimination of battery cells that meet the use requirements and avoid the outflow of battery cells that do not meet the use requirements, and can achieve a better balance between the two.

[0043] refer to Figure 10 In one specific embodiment, the method further includes determining whether each virtual welding area W is completely filled by the corresponding characteristic area S. If not, the battery cell is deemed unqualified. Two virtual welding areas W are symmetrically disposed on either side of a reference line L1 and spaced apart from the reference line L1. The virtual welding areas W include a positive electrode virtual welding area W1 corresponding to the positive electrode characteristic area S1 and a negative electrode virtual welding area W2 corresponding to the negative electrode characteristic area S2. If the virtual welding areas W are not completely filled by the characteristic area S, welding the current collector plate to the tab P may cause the separator welded to the end face 10 to short-circuit with the tab P and a pole piece of different polarity.

[0044] Based on the same inventive concept, an embodiment of the present application also provides a battery cell detection device, wherein the end face of the battery cell is provided with a pole ear P with opposite polarity; the battery cell detection device includes: an image acquisition unit and a processing unit; the image acquisition unit is used to acquire the end face image of the battery cell, identify two characteristic areas S corresponding one-to-one to the pole ears of two polarities, and determine the reference point O of the end face center according to the end face image, wherein the two characteristic areas 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 characteristic areas S is at a set angle b with the reference line L1, and the reference line L1 passes through the reference point O, and judge whether the two characteristic areas S overlap with the two prohibited areas D. If so, the battery cell is judged to be unqualified, wherein the two prohibited areas D are located on the reference line L1 and are symmetrically distributed on both sides of the reference point O. The area adjacent to the reference line L1 is designated as a prohibited area D. Once the positive characteristic area S1 overlaps with at least one of the prohibited areas D1 and D2, or the negative characteristic area S2 overlaps with at least one of the prohibited areas D1 and D2, it means that there is a risk that the positive characteristic area S1 and the negative characteristic area S2 are too close to each other. These battery cells will be treated as seriously defective products and judged as unqualified, effectively screening out seriously defective products and preventing them from flowing out.

[0045] In a specific embodiment, each feature region S has two tangent lines passing through the reference point O, for example, Figure 6 The positive characteristic region S1 has a tangent line L6 and a tangent line L7 passing through the reference point O, and the negative characteristic region S2 has a tangent line L9 and a tangent line L10 passing through the reference point O; the processing unit is further configured to:

[0046] Determine whether the angle between each tangent and the reference line L1 is within the first threshold range. If not, the battery cell is determined to be unqualified. If the angle between the tangent L6 and the reference line L1 is too small, or the angle between the tangent L7 and the reference line L1 is too large, it indicates that the positive characteristic area S1 is too inclined to one side of the tangent L6. The determination method of the tangent L9 and the tangent L10 is similar. Determine whether the angle between the adjacent tangents of the two characteristic areas S is within the second threshold range. If not, the battery cell is determined to be unqualified. For example, if the angle between the tangent L7 of the positive characteristic area S1 and the tangent L9 of the negative characteristic area S2 is too small, it indicates that the positive characteristic area S1 is too inclined to the side of the tangent L6. The determination method of the tangent L9 and the tangent L10 is similar. If the distance to the negative electrode characteristic area S2 is too close, a short circuit between the positive electrode tab P1 and the negative electrode tab P2 is likely to occur. Therefore, the battery cell is judged to be unqualified. It is judged whether the angle between the two tangents of each characteristic area S is within the third threshold range. If not, the battery cell is judged to be unqualified. For example, if the angle between the tangent L6 and the tangent L7 of the positive electrode characteristic area S1 is too large, it indicates that the misalignment between the positive electrode sheets of different layers in the positive electrode characteristic area S1 may be too large. If the angle between the tangent L6 and the tangent L7 is too small, it indicates that the area of ​​the positive electrode characteristic area S1 that can be used for welding the current collecting plate is too small. Therefore, the battery cell is judged to be unqualified, which can prevent the outflow of defective products.

[0047] 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 a line connecting the reference point O and the midpoint of the inner peripheral edge, and the second center line is a line connecting the reference point O and the midpoint of the outer peripheral edge; for example, referring to Figure 7 The positive electrode characteristic 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 an arc shape. The line connecting the reference point O and the inner peripheral edge V1 forms a first center line L4, and the line connecting the reference point O and the outer peripheral edge V2 forms a 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 characteristic region S is within a fourth threshold range. If not, the battery cell is determined to be unqualified. If the angle between the first center line L4 and the second center line L5 of the positive electrode characteristic region S1 is too large, it indicates that during the winding process of the battery cell, the positional deviation between the outer ring positive electrode tab P1 and the inner ring positive electrode tab P1 is large, that is, the alignment is poor. Therefore, this type of battery cell is determined to be unqualified, which can prevent the outflow of defective products. Among them, 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 value of the fourth threshold range is too large, it may cause the battery cell with poor alignment of the tab P to flow out.

[0048] In a specific embodiment, the processing unit is further configured to determine whether the ratio of the area of ​​each characteristic region S to the area of ​​the corresponding ideal tab region T is within a fourth threshold range; if not, the battery cell is determined to be unqualified, wherein 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, and the circumferential direction is the direction surrounding the reference point O. For example, with reference to Figure 4 and Figure 8 The positive electrode ideal tab region T1 corresponding to the positive electrode characteristic region S1 and the negative electrode ideal tab region T2 corresponding to the negative electrode characteristic region S2 are symmetrically distributed on both sides of the reference line L1. The positive electrode ideal tab region T1 is circumferentially spaced apart from the prohibited region D1 and the prohibited region D2, respectively. The negative electrode ideal tab region T2 is circumferentially spaced apart from the prohibited region D1 and the prohibited region D2, respectively. The degree of overlap between the positive electrode characteristic region S1 and the positive electrode ideal tab region T1 is determined by determining the ratio 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 significantly from the positive electrode ideal tab region T1, and the battery cell is deemed unqualified, thus preventing the discharge of defective batteries.

[0049] In a specific embodiment, the processing unit is further configured to determine whether the area ratio of each characteristic region S to the area ratio of the corresponding dangerous region G is within a fifth threshold range; if not, the battery cell is determined to be unqualified, wherein a dangerous region G is set at adjacent positions on both sides of each prohibited region D in the circumferential direction, and the circumferential direction is the direction surrounding the reference point O. For example, referring to Figure 4 and Figure 9 , with reference point O as the origin, reference line L1 as the horizontal axis, and vertical line L3 as the vertical axis, forming a coordinate system. The four danger zones G are: danger zone G1 in the first quadrant, danger zone G2 in the second quadrant, danger zone G3 in the third quadrant, and danger zone G4 in the fourth quadrant. Taking the positive characteristic region S1 as an example, if too much of the positive characteristic region S1 lies within danger zone G1 or danger zone G2, i.e., if the area occupies too large a proportion, this indicates that at least one side of the positive characteristic region S1 is too close to the negative characteristic region S2, which could easily cause a short circuit. Such cells will be judged as unqualified, thus preventing the outflow of defective products.

[0050] In one specific embodiment, the processing unit is further configured to determine whether each virtual welding region W is completely filled by the corresponding characteristic region S. If not, the battery cell is deemed unqualified. The two virtual welding regions W are symmetrically disposed on either side of a reference line L1 and spaced apart from the reference line L1. If the virtual welding regions W are not completely filled by the characteristic region S, welding the current collector plate and the tab P may cause the separator welded to the end face 10 to short-circuit with the tab P and a pole piece of different polarity.

[0051] Based on the same inventive concept, an embodiment of the present application also provides a cell correction method based on the cell detection method provided in the above embodiment, and 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 the angle of the difference to perform preliminary correction on the cell, and the rotation direction of the cell is the same as the rotation direction of the end face image, wherein the initial angle refers to the angle between the arrangement direction of the two feature areas S before the end face image is rotated and the reference line L1; when the focus parts of the two feature areas 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 focus parts of the two feature areas S are equal in area or the corresponding circumferential angles are the same, thereby dispersing the alignment deviation of the cell to the two feature areas, so that the position deviation of the two feature areas is minimized as much as possible, and the circumferential angle corresponding to each focus part refers to the angle of the focus part passing through the reference point O. The angle between the line and the boundary of the corresponding dangerous area G, such as the angle d formed by the tangent L0 of the focus part of the positive characteristic area S located in the dangerous area G1 and the corresponding boundary of the dangerous area G1, is the circumferential angle corresponding to the focus part of the positive characteristic area S1; or, when the focus parts of two characteristic areas S are located on different sides of the reference point O in the direction of the reference line L1, the battery cell is rotated so that the areas of the characteristic areas S in the four dangerous areas G tend to be close, so that the alignment deviation of the battery cell is dispersed to the two characteristic areas, so that the position deviation of the two characteristic areas is minimized as much as possible; wherein, the focus part refers to the larger part of the overlapping part of each characteristic area S with the dangerous areas G on both sides, for example, the area of ​​the positive characteristic area S1 overlapping with the dangerous area G1 is larger than the area of ​​the overlapping area with the dangerous area G2, then the part of the positive characteristic area S1 overlapping with the dangerous area G1 is the focus part of the positive characteristic area S1.

[0052] For example, reference Figure 11 In a specific battery cell production line, the following steps are performed in sequence:

[0053] S1. Using a winding mechanism to wind a pole piece assembly to form a battery cell, the pole piece assembly includes positive pole pieces and negative pole pieces alternately arranged in sequence, with a separator provided between the positive pole pieces and the negative pole pieces, and the battery cell tabs P formed by winding stand on the end surface 10 of the battery cell without being flattened;

[0054] S2. unloading the wound battery cell to a conveying mechanism, such as a conveyor belt;

[0055] S3. After the battery cell is transferred to the first inspection station, the battery cell is inspected using the above-mentioned battery cell inspection method to determine whether the battery cell is qualified. If the battery cell is unqualified, step S31 is executed to discard the unqualified battery cell. Otherwise, step S4 is executed.

[0056] S4. Correct the battery cell using the battery cell correction method provided in the above embodiment, so that the tab P can be aligned with the leveling mechanism;

[0057] S5. Control the flattening mechanism to flatten the tab P. For example, the flattening structure having an arc-shaped notch gradually pushes down the tab P from the outer periphery toward the reference point O along the radial direction of the end face 10 of the battery cell. The tab P falls on the end face 10 of the battery cell to facilitate subsequent welding with the collecting plate.

[0058] S6. After the battery cell is transferred to the second inspection station, the battery cell is inspected using the above-mentioned battery cell inspection method to determine whether the battery cell is qualified. If the battery cell is unqualified, step S61 is executed to discard the unqualified battery cell. Otherwise, step S7 is executed.

[0059] S7. Use the cell correction method provided in the above embodiment to correct the cell so that the tab P can be rotated to the angle required for unloading. The correction mechanism used can be a cell picking robot arm.

[0060] Wherein, both step S3 and step S6 can be detected by CCD (Charge-Coupled Device).

[0061] When executing the above-mentioned battery cell detection method in step S3, the following method can be used: Figure 12 The image acquisition unit shown. 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 above-mentioned charge-coupled device and is positioned toward the end face 10 of the battery cell 01. The camera 03 and light source 02 can be coaxially arranged with the battery cell 01, and a channel is provided in the middle of the light source 02 for transmitting light to the camera 03. The light source 02 here can be a 0° blue annular light source so that the edge of the standing tab P can reflect light, thereby facilitating the identification of the characteristic area S of the tab P. The distance from the light source 02 to the end face 10 can be between 5 mm and 20 mm, for example, 5 mm, 10 mm, 15 mm, and 20 mm. If the distance is too close, interference between the light source 02 and the tab P may occur, 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 may have difficulty irradiating the edge of the tab P.

[0062] When executing the above-mentioned battery cell detection method in step S6, the following method can be used: Figure 13 The image acquisition unit shown. Figure 13 ,and Figure 12 The difference between the image acquisition units shown is that the camera 03 can use an industrial FA (Factory Automation) lens, and the light source 02 uses a spherical integrating light source, so that the light can evenly illuminate the end face 10 of the battery cell 01, so that the flattened tab P can evenly reflect light.

[0063] Furthermore, in step S3 and step S6, the overall deviation trend of the tab P can be statistically calculated based on the detection results of multiple battery cells, and the deviation trend can be fed back to the winding mechanism for adaptive deviation correction by the winding mechanism.

[0064] Obviously, those skilled in the art may make various changes and modifications to the embodiments of the present invention without departing from the spirit and scope of the present invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims and their equivalents, the present invention is intended to include such modifications and variations.

Claims

1. A battery cell detection method, characterized in that: The end faces of the battery core are provided with tabs with opposite polarities; The method comprises: Acquire an end face image of the battery cell, identify two characteristic regions corresponding to the tabs of two polarities, and determine a reference point at the center of the end face based on the end face image, wherein the two characteristic regions are located on either side of the reference point; Rotating the end face image so that the arrangement direction of the two characteristic regions forms a set angle with a reference line, and the reference line passes through the reference point; Determining whether the two characteristic areas overlap with two prohibited areas, and if so, determining that the battery cell is unqualified, wherein the two prohibited areas are located on the reference line and symmetrically distributed on both sides of the reference point; The determining of the reference point according to the end face image specifically includes: The contour of the end face is identified, and the center of the circumscribed circle or the center of the inscribed circle of the contour of the end face is used as the reference point.

2. The battery cell detection method according to claim 1, wherein: Each of the forbidden areas is a sector with the reference point as the center and the reference line as the axis of symmetry, and the circumferential angle corresponding to the forbidden area is between 5° and 20°.

3. The battery cell detection method according to claim 1, wherein: The set angle is between 85° and 95°.

4. The battery cell detection method according to claim 1, wherein: The arrangement direction of the two characteristic regions refers to the direction of the line connecting the centroids of the two characteristic regions.

5. The battery cell detection method according to claim 1, wherein: Each of the characteristic regions has two tangent lines passing through the reference point; The method further comprises: Determining whether the angle between each tangent line and the reference line is within a first threshold range, and if not, determining that the battery cell is unqualified; determining whether an angle between adjacent tangent lines of two characteristic regions is within a second threshold range, and if not, determining that the battery cell is unqualified; It is determined whether the angle between the two tangent lines of each characteristic region is within a third threshold range; if not, the battery cell is determined to be unqualified.

6. The battery cell detection method according to claim 5, characterized in that: 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°.

7. The battery cell detection method according to claim 1, characterized in that: Each of the characteristic 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 centerline and a second centerline, wherein the first centerline is a line connecting the reference point and the midpoint of the inner peripheral edge, and the second centerline is a line connecting the reference point and the midpoint of the outer peripheral edge; The method further comprises: It is determined whether the angle between the first center line and the second center line of each characteristic area is within a fourth threshold range; if not, the battery cell is determined to be unqualified.

8. The battery cell detection method according to claim 7, characterized in that: The fourth threshold range is greater than or equal to 0° and less than or equal to 20°.

9. The battery cell detection method according to any one of claims 1 to 8, characterized in that: The method further comprises: Determine whether the ratio of the area of ​​each of the characteristic regions to the area of ​​the corresponding ideal tab region is within a fourth threshold range; if not, determine that the battery cell is unqualified, wherein the two ideal tab regions are symmetrically distributed on both sides of the reference line, and each of the ideal tab regions is spaced apart from the prohibited regions on both sides in the circumferential direction, and the circumferential direction is the direction surrounding the reference point.

10. The battery cell detection method according to claim 9, characterized in that: Each of the ideal tab regions is a sector with the reference point as the center, and the corresponding circumferential angle is between 40° and 50°, wherein the symmetry axis of the ideal tab region is perpendicular to the reference line.

11. The battery cell detection method according to claim 9, characterized in that: The fourth threshold range is greater than or equal to 80% and less than or equal to 100%.

12. The battery cell detection method according to any one of claims 1 to 11, characterized in that: The method further comprises: Determine whether the area ratio of each characteristic area to the area ratio of the corresponding dangerous area is within the fifth threshold range; if not, determine that the battery cell is unqualified, wherein each dangerous area is set at adjacent positions on both sides of the circumference of each prohibited area, and the circumference is the direction surrounding the reference point.

13. The battery cell detection method according to claim 12, characterized in that: Each of the dangerous areas is a sector with the reference point as the center, and the corresponding circumferential angle is between 5° and 20°.

14. The battery cell detection method according to claim 12, characterized in that: The fifth threshold range is greater than or equal to 0 and less than or equal to 50%.

15. The battery cell detection method according to claim 12, characterized in that: When an ideal tab area is provided between two prohibited areas, the ideal tab area is located between the two dangerous areas on the same side of the reference line and is provided adjacent to the dangerous area.

16. The battery cell detection method according to any one of claims 1 to 15, characterized in that: The method further comprises: It is determined whether each virtual welding area is completely filled by the corresponding characteristic area. If not, the battery cell is determined to be unqualified, wherein the two virtual welding areas are symmetrically arranged on both sides of the reference line and spaced apart from the reference line.

17. A battery cell detection device, characterized in that: The end faces of the battery core are provided with tabs with opposite polarities; The battery cell detection 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 characteristic regions corresponding to the tabs of two polarities, and determine a reference point at the center of the end face based on the end face image, wherein the two characteristic regions are located on both sides of the reference point. The determining of the reference point according to the end face image specifically includes: Identify the contour of the end face, and use the center of the circumscribed circle or the center of the inscribed circle of the contour of the end face as the reference point The processing unit is used to adjust the end face image so that the arrangement direction of the two characteristic areas is at a set angle with a reference line, and the reference line passes through the reference point, and determines whether the two characteristic areas overlap with two prohibited areas. If so, the battery cell is determined to be unqualified, wherein the two prohibited areas are located on the reference line and are symmetrically distributed on both sides of the reference point.

18. The battery cell detection device according to claim 17, characterized in that: Each of the characteristic regions has two tangent lines passing through the reference point; The processing unit is further configured to: Determining whether the angle between each tangent line and the reference line is within a first threshold range, and if not, determining that the battery cell is unqualified; determining whether an angle between adjacent tangent lines of two characteristic regions is within a second threshold range, and if not, determining that the battery cell is unqualified; It is determined whether the angle between the two tangent lines of each characteristic region is within a third threshold range; if not, the battery cell is determined to be unqualified.

19. The battery cell detection device according to claim 17, characterized in that: Each of the characteristic 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 centerline and a second centerline, wherein the first centerline is a line connecting the reference point and the midpoint of the inner peripheral edge, and the second centerline is a line connecting the reference point and the midpoint of the outer peripheral edge; The processing unit is further configured to: It is determined whether the angle between the first center line and the second center line of each characteristic area is within a fourth threshold range; if not, the battery cell is determined to be unqualified.

20. The battery cell detection device according to claim 17, characterized in that: The processing unit is further configured to: Determine whether the ratio of the area of ​​each of the characteristic regions to the area of ​​the corresponding ideal tab region is within a fourth threshold range; if not, determine that the battery cell is unqualified, wherein the two ideal tab regions are symmetrically distributed on both sides of the reference line, and each of the ideal tab regions is spaced apart from the prohibited regions on both sides in the circumferential direction, and the circumferential direction is the direction surrounding the reference point.

21. The battery cell detection device according to claim 17, characterized in that: The processing unit is further configured to: Determine whether the area ratio of each characteristic area to the area ratio of the corresponding dangerous area is within the fifth threshold range; if not, determine that the battery cell is unqualified, wherein each dangerous area is set at adjacent positions on both sides of the circumference of each prohibited area, and the circumference is the direction surrounding the reference point.

22. The battery cell detection device according to claim 17, characterized in that: The processing unit is further configured to: It is determined whether each virtual welding area is completely filled by the corresponding characteristic area. If not, the battery cell is determined to be unqualified, wherein the two virtual welding areas are symmetrically arranged on both sides of the reference line and spaced apart from the reference line.

23. A cell deviation correction method based on the cell detection method according to any one of claims 12 to 15, characterized in that: include: When the absolute value of the difference between the initial angle and the set angle is greater than 0, the driving component is controlled to drive the battery cell to rotate by the angle of the difference, and the rotation direction of the battery cell is the same as the rotation direction of the end face image, wherein the initial angle refers to the angle between the arrangement direction of the two characteristic areas of the end face image before rotation and the reference line; When the portions of interest in the two characteristic regions are located on the same side of the reference point in the direction of the reference line, rotating the battery cell so that the areas of interest in the two characteristic regions are equal or the corresponding circumferential angles are the same; or When the portions of interest in two characteristic regions are located on different sides of the reference point in the direction of the reference line, rotating the battery cell so that the areas of the characteristic regions in the four dangerous regions are close to each other; The focus portion refers to a larger portion of the overlapped portion between each of the feature regions and the dangerous regions on both sides.

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