JP2017208294A - Inspection method of electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection method of an electrode, capable of stably acquiring a coating width in an intermittent coating.SOLUTION: In a case where a tip position of a projection part 50 of a coating part 19 is not detected by an image dimension measurement device, an arbitrary point of an X- direction and a Y-direction in the coating part 19 is set as reference points X0 and Y0 to an image obtained by the image dimension measurement device. In the image, approximate curve lines L1 and L2 of a function of the position of the X-direction and the Y-direction are formed with end part regions 51a and 51b sandwiching the tip of the projection part 50 in the image in the X-direction. An intersection point near the reference points X0 and Y0 in the Y-direction from the intersection points of the approximate curve lines L1 and L2 measured corresponding to each of the end part regions 51a and 51b is set as a position of the tip of the projection part 50.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a method for inspecting an electrode formed by cutting an electrode material provided alternately with a coating portion and an exposed portion.

  For example, vehicles such as EV (Electric Vehicle) and PHV (Plug in Hybrid Vehicle) are equipped with a power storage device for storing electric power used by a motor as a drive source. As such a power storage device, for example, a secondary battery such as a lithium ion secondary battery or a nickel hydride secondary battery is known. The secondary battery includes an electrode assembly in which positive and negative electrodes each having an active material layer are layered. As the structure of the electrode assembly, a long positive electrode and a negative electrode of a certain length are wound in a cylindrical shape in an overlapping state, and a large number of positive and negative electrodes having a substantially rectangular shape are alternately arranged. A stacked type is known.

  For example, an electrode such as a lithium ion secondary battery includes an active material layer on both surfaces of a rectangular current collector, and an uncoated portion and a tab formed by a portion where the current collector is exposed. is there.

  As an example of a method for producing such an electrode, first, a paste-like active material mixture is applied to the surface of a long current collector in the longitudinal direction of the long current collector to form an electrode material. As the coating method, continuous coating and intermittent coating are known, and in the case of continuous coating, a coating portion is formed continuously in the longitudinal direction of the long current collector. As a method of intermittent coating, for example, there is a method using a reverse coater type coating apparatus (for example, see Patent Document 1).

  When forming an intermittent coating part using a reverse coater type coating device, a long current collector is conveyed by a backing roll, an active material mixture is applied to the outer peripheral surface of the coating roll by a doctor roll, and the backing is applied. The active material mixture is transferred to the long current collector at the transfer position where the roll and the coating roll come into contact. On the other hand, when forming the exposed portion, the long current collector is exposed as it is without transferring the active material mixture by separating the backing roll from the coating roll.

  As another intermittent coating method, there is a method using a slit die (for example, see Patent Document 2). When a slit die is used, the active material mixture is discharged from the discharge port by opening the flow path to which the active material mixture is supplied in the slit die, and the active material mixture is then applied to the long current collector. Apply to form the coated part. On the other hand, by blocking the flow path in the slit die, the discharge of the active material mixture is stopped, and the long current collector is exposed as it is to form an exposed portion. Thereafter, the electrode material is punched into an electrode shape. As a result, an active material layer is formed from the coated portion, an uncoated portion and a tab are formed from the exposed portion, and an electrode is manufactured.

JP 2003-260931 A JP 2007-66744 A

  The manufactured secondary battery needs to satisfy the value determined by design in terms of battery capacity. The battery capacity can be measured in an inspection process after the secondary battery is assembled. However, after assembling, it is found that the battery capacity does not satisfy the predetermined value, and if it is determined as a defective product, the secondary battery itself is discarded, resulting in a large loss. Therefore, in the electrode manufacturing process, the amount of the active material layer that directly affects the battery capacity is also inspected. Specifically, the area (or coating width) and thickness of the coating part or active material layer are measured simultaneously or separately, and an electrode having a predetermined value or less is regarded as a defective product. As a method for detecting the coating width, for example, the coating portion is directly inspected by an optical detection device.

  By the way, compared with the continuous coating, there are many portions where the coating width cannot be partially detected by the optical detection device for the coating portion formed by intermittent coating. As a result of examining the corresponding part, a chevron-shaped protruding part with a sharp tip is formed at the edge of the coating part, and it is particularly needle-shaped or the active material mixture is scattered near the tip. It was. In such a state, it is presumed that the optical detection device could not detect (determine) the boundary of the coating part.

  The above problems were observed especially in intermittent coating. In intermittent coating, coated portions and exposed portions are alternately formed, and coating and non-coating of the active material mixture are repeated. Specifically, when a reverse coater type coating device is used, the backing roll and coating roll are always in contact with continuous coating, whereas intermittent coating repeats contact and non-contact. Is likely to occur. For this reason, due to this vibration, chattering (stick-slip phenomenon) is likely to occur in intermittent coating, and a mountain-shaped protruding portion may be formed at the edge of the coated portion.

  An object of the present invention is to provide an electrode inspection method capable of stably obtaining a coating width even in intermittent coating.

  The electrode inspection method for solving the above-described problems includes a coating part formed by applying an active material mixture along the longitudinal direction of the long current collector, and the long current collector exposed. In an inspection method of an electrode formed by cutting an electrode material having an exposed portion alternately in a longitudinal direction of the long current collector, a direction along a boundary between the coated portion and the exposed portion is an X direction. A direction along the surface direction of the coating part and perpendicular to the X direction is a Y direction of the coating part, and an edge of the coating part located at a boundary with the exposed part is a first end. An edge and an edge of the coating part existing on the opposite side of the first edge are defined as a second edge, and the first edge and the second edge are shortest along the Y direction. When the dimension of a straight line connected by a distance is the coating width, the first edge is detected when the coating portion is detected by an optical detection device for detection of the coating width. When the position of the tip of the protruding portion that exists and protrudes in the Y direction cannot be detected, reference points X0 and Y0 are set in the coated portion in the image obtained by the optical detection device, and the protruding For the end region sandwiching the tip of the part in the X direction, create an approximate curve of a function of the position in the X direction and the position in the Y direction, and among the intersections of the approximate curves obtained for each end region, The gist is to calculate an intersection point close to the reference point Y0 in the Y direction as the position of the tip of the protrusion.

  According to this, when application and non-coating of the active material mixture are repeated by intermittent coating, vibration is likely to occur, and due to vibration, chatter is likely to occur in intermittent coating, and the coating part In some cases, a mountain-shaped protrusion is formed on the edge of the. When the position of the tip of the protrusion cannot be detected by the optical detection device, a reference point on the coating portion and an arbitrary point on each end region are acquired from the image obtained by the optical detection device. An approximate curve along each end region is obtained from these points, and an intersection point close to the reference point among the intersection points of these approximate curves is used as the coordinates of the tip of the protrusion. As a result, the position of the protrusion can be calculated using the obtained image, and the coating width can be obtained stably.

In the electrode inspection method, the approximate curve along the end region has an arc shape.
According to this, two intersection points of two approximate curves can be derived, and the intersection point close to the reference point can be set as the position of the tip of the protruding portion.

Regarding the electrode inspection method, the electrode is preferably a positive electrode.
According to this, the coated part that becomes the active material layer of the positive electrode is often harder than the coated part of the negative electrode, and after the electrode material for the positive electrode is manufactured, the electrode material can be wound up. For this purpose, it is necessary that the coating part and the exposed part are alternately present. For this reason, in the manufacturing method of a positive electrode, application | coating of an active material mixture will be performed by intermittent coating. In the case of intermittent coating, since application and non-coating of the active material mixture are repeated, vibration is likely to occur, and a protrusion is likely to be formed due to vibration. However, since the position of the tip of the protrusion can be calculated by the electrode inspection method, the inspection method of the present embodiment is more preferably applied for the inspection of the positive electrode.

  Also, regarding the electrode inspection method, after the electrode material is cut into the shape of the electrode to form an electrode precursor and before the electrode is laminated, the position of the tip of the protruding portion is detected. preferable.

  According to this, the coating part of an electrode precursor is a site | part used as an active material layer of an electrode as it is. Therefore, for example, immediately after coating the active material mixture on the long metal foil, it is more stable than the case where the inspection is performed before the coating width is changed by performing the subsequent pressing process or cutting process. Coating width can be obtained.

  According to the present invention, a coating width can be stably obtained even in intermittent coating.

The perspective view which shows a positive electrode. The partial top view which shows the state by which intermittent coating was carried out. The schematic diagram which shows the state which forms an electrode precursor. The top view which shows an electrode precursor. The figure which expands and shows the 1st edge of the coating part containing a protrusion part. The figure which shows the method of detecting the front-end | tip of a protrusion part using an approximated curve.

Hereinafter, an embodiment in which an electrode inspection method is embodied will be described with reference to FIGS.
Although not shown, the secondary battery as the power storage device is, for example, a lithium ion secondary battery. The secondary battery includes an electrode assembly, an electrolytic solution, and a case containing the electrode assembly and the electrolytic solution. The electrode assembly includes a plurality of positive electrodes as electrodes, a plurality of negative electrodes (not shown) as electrodes, and a plurality of separators (not shown). The positive electrode and the negative electrode overlap each other in a state of being insulated from each other by the separator.

  As shown in FIG. 1, the positive electrode 11 has a rectangular sheet shape. The positive electrode 11 includes a positive electrode current collector foil 12. The positive electrode current collector foil 12 is, for example, an aluminum foil. The positive electrode 11 includes a positive electrode active material layer 13 that covers both surfaces of the positive electrode current collector foil 12. The positive electrode 11 includes a positive electrode tab 14 having a shape protruding from one side of the positive electrode current collector foil 12. The positive electrode 11 includes a positive electrode uncoated portion 15 along the protruding side of the positive electrode tab 14. The positive electrode uncoated portion 15 is a portion where the positive electrode active material layer 13 is not present and the positive electrode current collector foil 12 is exposed.

  Although not shown, the negative electrode has a rectangular sheet shape. The negative electrode includes a negative electrode current collector foil. The negative electrode current collector foil is, for example, a copper foil. The negative electrode includes a negative electrode active material layer that covers both surfaces of the negative electrode current collector foil. The negative electrode includes a negative electrode tab having a shape protruding from one side of the negative electrode current collector foil.

Next, a method for manufacturing the positive electrode 11 will be described.
The manufacturing method of the positive electrode 11 includes a coating process, a drying process, a slit process, a pressing process, a vacuum drying process, a cutting process, and an inspection process.

  As shown in FIG. 2, in the coating process, the long metal foil 18 as a long current collector is conveyed in the longitudinal direction, and on both sides of the long metal foil 18 (only one side is shown in FIG. 2). On the other hand, the active material mixture is applied at intervals from a coating apparatus (not shown). As the coating apparatus, a reverse coater type coating apparatus may be used, or a slit die type coating apparatus may be employed. If intermittent coating is possible, the coating apparatus is not particularly limited. . As a result, the coating portions 19 of the active material mixture and the exposed portions 20 where the long metal foil 18 is exposed are alternately formed in the longitudinal direction of the long metal foil 18. Then, the coating parts 19 and the exposed parts 20 are alternately arranged in the longitudinal direction of the long metal foil 18. The active material mixture is a paste in which an active material, a conductive additive, and a binder (binder) are mixed and a solvent is added and kneaded.

  Further, in the coating process, the active material mixture is formed such that blank portions 21 are formed on both sides of each coating portion 19 in the short direction perpendicular to the longitudinal direction along the surface of the long metal foil 18. Is applied. And the electrode material 23 is formed by the coating part 19, the exposed part 20, and the blank part 21 being formed.

  Next, in a drying process (not shown), the electrode material 23 passes through the dryer. For example, hot air of about 80 degrees is supplied into the dryer. While the electrode material 23 passes through the inside of the dryer, most of the solvent contained in the coating unit 19 evaporates.

  In the slit process of the next process, the blank portions 21 on both sides in the short direction of the electrode material 23 are cut off. The next pressing step is performed by sandwiching and pressing the electrode material 23 with a pair of press rollers. The coating parts 19 are each compressed to a predetermined thickness. The pressed electrode material 23 is taken up on a take-up reel (not shown).

  The next vacuum drying step is performed to remove a slight amount of solvent remaining in the coating unit 19. The vacuum drying process is performed by placing the electrode material 23 taken up on the take-up reel in a drying furnace (not shown). And a vacuum drying process is performed by depressurizing the inside of a drying furnace and heating the coating part 19, and a little solvent which remains in the coating part 19 volatilizes, and a binder hardens | cures. In the next cutting step, the electrode material 23 is cut at regular intervals along the longitudinal direction, and the electrode material 23 is punched into the shape of the positive electrode 11.

  As shown in FIG. 3, in the cutting device 30 that performs the cutting process, the winding reel 31 after the vacuum drying process is set, and another winding for winding the electrode material 23 wound up on the winding reel 31 A take-up reel (not shown) is set. The take-up reel 31 is rotatably supported by a driving device (not shown). The cutting device 30 includes a cutting device 33 that punches the electrode material 23 into the shape of the positive electrode 11. The cutting device 33 is arranged downstream of the take-up reel 31 in the conveying direction of the electrode material 23.

  And in the cutting device 30, the electrode material 23 is conveyed by winding up the electrode material 23 wound up by the winding reel 31 with another winding reel. When the electrode material 23 is punched out by the cutting device 33, an electrode precursor 24 that is a precursor of the positive electrode 11 is formed.

  As shown in FIG. 4, the electrode precursor 24 has the same shape as the positive electrode 11. The electrode precursor 24 shows a state before undergoing the inspection process, and the electrode precursor 24 that has undergone the inspection process becomes the positive electrode 11. For this reason, the coating part 19 of the electrode precursor 24 has the same shape as the positive electrode active material layer 13, and the exposed part 20 of the electrode precursor 24 has the same shape as the positive electrode uncoated part 15 and the positive electrode tab 14. .

Next, the inspection process will be described.
As shown in FIG. 3, the inspection process is performed immediately after the electrode precursor 24 is formed by the cutting device 30. The inspection process is performed using an image dimension measuring device 40 as an optical detection device disposed on the downstream side of the cutting device 30 in the conveying direction of the electrode material 23. The inspection process is a process of measuring the coating width of the coating part 19 of the electrode precursor 24.

  In a secondary battery, the battery capacity needs to satisfy a value determined by design. In the manufacturing process of the positive electrode 11 and the negative electrode, the amount of the coating part 19 that directly affects the battery capacity is inspected, and an electrode below a predetermined value becomes a defective product. The inspection of the positive electrode 11 and the negative electrode is performed by calculating the coating width of the coating part 19 in the electrode precursor 24.

  As shown in FIG. 4, for the electrode precursor 24, the direction along the boundary between the coating part 19 and the exposed part 20 is defined as the X direction of the coating part 19. A direction along the surface direction of the coating unit 19 and perpendicular to the X direction is defined as a Y direction of the coating unit 19. Moreover, in the electrode precursor 24, the edge of the coating part 19 located on the boundary with the exposed part 20 is the first edge 19a and the edge of the coating part 19 existing on the opposite side of the first edge 19a. Let the edge be the second end edge 19b. In the coating part 19 of the electrode precursor 24, the dimension of a straight line connecting the first edge 19a and the second edge 19b along the Y direction at the shortest distance is defined as a coating width W.

  As shown in FIG. 3, the image dimension measuring device 40 used in the inspection process measures the coating width W of the coating part 19 of the electrode precursor 24. The image dimension measuring device 40 includes a measuring unit 41 that acquires an image of the coating unit 19 of the electrode precursor 24, and a control unit 42 that is signal-connected to the measuring unit 41. Image information measured by the measurement unit 41 is input to the control unit 42.

  By the way, as shown in FIG. 5, the 1st edge 19a of the coating part 19 may be formed with the protrusion part 50 of the shape which protruded in the mountain shape along the Y direction. The cause of the protrusion 50 being formed is presumed to be due to the vibration phenomenon in the coating process. It is presumed that the distance between the coating device and the long metal foil 18 changes due to the generated vibration during the coating process, and the angled protrusion 50 is formed on the first edge 19a of the coating part 19. The

  The protrusion 50 has a shape that becomes narrower toward the tip, or a phenomenon called “flying” in which the active material mixture is scattered near the tip of the protrusion 50, and the coating portion 19 is applied by the image size measuring instrument 40. And the exposed portion 20 cannot be detected, and the coating width W of the coating portion 19 may not be detected. When the coating width W including the position of the tip of the protrusion 50 cannot be measured, a step of detecting the position of the tip of the protrusion 50 as a coordinate is performed.

  As shown in FIG. 6, the protrusion 50 includes a first end region 51a on one side connected to the tip in the protruding direction, and a second end region 51b on the other side connected to the tip. . The first end region 51a and the second end region 51b are each deformed in an arc shape toward the tip of the protruding portion 50 along the Y direction.

Next, a method for detecting the position of the tip of the protrusion 50 will be described.
First, the control unit 42 sets an arbitrary reference point X0 in the X direction at a position close to the first edge 19a among the positions on the coating unit 19. Moreover, the position of the Y direction in the reference | standard point X0 among the positions on the coating part 19 is set with the reference | standard point Y0. Thereby, an arbitrary reference point (X0, Y0) is set on the coating part 19. The reference point is acquired from the image of the coating unit 19 measured by the measuring unit 41 of the image dimension measuring device 40.

  Next, the control unit 42 determines any two points (Xr1, Yr1), (Xr2, Yr2) separated from the reference point Y0 in the Y direction with respect to the first end region 51a from the image measured by the measurement unit 41. ) To get. Then, the control unit 42 applies a first regression analysis method (typically, the least square method) to these two points (Xr1, Yr1) and (Xr2, Yr2) to obtain a first approximate curve L1 approximated to an arc. Ask. The first approximate curve L1 is elliptical along the arc of the first end region 51a.

  Similarly, the control unit 42 acquires arbitrary two points (Xb1, Yb1) and (Xb2, Yb2) that are separated from the reference point Y0 in the Y direction with respect to the second end region 51b. Then, the control unit 42 applies a first regression analysis method (typically, the least square method) to these two points (Xb1, Yb1) and (Xb2, Yb2) to obtain a second approximate curve L2 approximated to an arc. Ask. The second approximate curve L2 has an elliptical shape along the arc of the second end region 51b.

  Next, the control unit 42 sets the intersection closer to the reference point (X0, Y0) among the intersections of the trajectory of the first approximate curve L1 and the trajectory of the second approximate curve L2 to the tip of the protrusion 50. Coordinates (Xc, Yc). Thereby, with respect to the tip of the protrusion 50, the dimension in the X direction from the reference point X0 and the dimension T2 in the Y direction from the reference point Y0 are acquired, and the position of the protrusion 50 is detected.

  Next, the control unit 42 measures the dimension T1 in the Y direction from the second edge 19b to the reference point shown in FIG. 5 and the Y direction from the reference point Y0 to the tip of the protrusion 50 shown in FIG. The coating width W of the coating part 19 including the tip of the protruding part 50 is calculated by adding the dimension T2.

In the coating unit 19, the coating width W is detected by the image size measuring device 40 at a portion where the protruding portion 50 does not exist. And the coating width W is detected over the whole X direction of the coating part 19. FIG.
Thereafter, the coating width W of the obtained coating part 19 is compared with a preset threshold value of the coating width W. The threshold value of the coating width W is a value of the coating width necessary to ensure a prescribed capacity for the positive electrode 11. If the detected coating width W has a coating width W less than the threshold value, the positive electrode 11 including the coating portion 19 is regarded as a defective product.

Thereafter, the positive electrode 11 and the negative electrode, which are regarded as non-defective products, are used, and the positive electrode 11 and the negative electrode are stacked in a state of being insulated from each other by a separator, thereby forming an electrode assembly.
According to the above embodiment, the following effects can be obtained.

  (1) When measuring the coating width W of the coating part 19 by the image size measuring instrument 40 in order to determine the quality of the positive electrode 11, the position of the tip of the protruding part 50 cannot be detected, and the coating width W is It may not be detected. In this case, a reference point on the coating unit 19 and two arbitrary points on each of the end regions 51a and 51b are acquired from the image obtained by the image size measuring device 40. From these points, approximate curves L1 and L2 along the end regions 51a and 51b are obtained, and the intersection point close to the reference point among the intersection points of these approximate curves L1 and L2 is the coordinates of the tip of the projection 50, and the projection 50 The position of the tip of is calculated. Therefore, even if the position of the tip of the protrusion 50 cannot be detected by the image size measuring instrument 40, the position of the tip of the protrusion 50 can be calculated and detected using the obtained image. Therefore, the position of the tip of the protruding portion 50 can be calculated and the coating width W can be obtained stably without providing a device other than the image size measuring instrument 40.

  (2) The approximate curves L1 and L2 along the end regions 51a and 51b are elliptical. For this reason, two intersections of the first approximate curve L1 and the second approximate curve L2 can be derived, and the intersection close to the reference point Y0 can be set as the position of the tip of the protruding portion 50.

  (3) The inspection method of this embodiment was applied to the positive electrode 11. The coating part 19 of the positive electrode 11 is often harder than the coating part of the negative electrode, and the coating part 19 and the exposed part 20 are alternately arranged so that the electrode material 23 for the positive electrode 11 can be wound. Must be present. For this reason, in the manufacturing method of the positive electrode 11, application | coating of an active material mixture will be performed by intermittent coating. In the case of intermittent coating, since active material mixture coating and non-coating are repeated, vibration is likely to occur, chatter due to vibration is likely to occur, and a mountain-shaped protrusion 50 is formed. Cheap. However, in this embodiment, since the position of the tip of the protrusion 50 can be calculated, the inspection method of this embodiment is more preferably applied to the positive electrode 11.

  (4) The inspection step is immediately after the electrode material 23 is punched into the shape of the positive electrode 11 to form the electrode precursor 24, and is performed before the electrodes are stacked. The coating part 19 of the electrode precursor 24 is a part that becomes the positive electrode active material layer 13 of the positive electrode 11 as it is. Therefore, for example, compared with the case where the inspection process is performed immediately after the active material mixture is applied to the long metal foil 18, the position of the tip of the protrusion 50 is calculated, and then the coating width W is detected with high accuracy. The quality of the positive electrode 11 can be determined with high accuracy.

In addition, you may change the said embodiment as follows.
In the embodiment, the detection of the coating width W of the coating part 19 is performed in the dimension T1 in the Y direction from the second edge 19b to the reference point, and in the Y direction from the reference point to the tip of the protrusion 50. However, the coating width W may be detected by other methods.

The approximate curves L1 and L2 along the end regions 51a and 51b of the protrusion 50 may be a perfect circle.
In the embodiment, the inspection process of the protrusion 50 is performed immediately after the electrode material 23 is punched into the shape of the electrode to form the electrode precursor 24. However, the timing of performing the inspection process may be changed as appropriate. For example, it may be immediately after the slitting process or the pressing process.

The long current collector may be other than a long metal foil, is a long shape, and may be a punching metal or a metal fiber having a three-dimensional structure.
○ Regarding the negative electrode, if the application process of the active material mixture is performed by intermittent coating, and the negative electrode has a structure including an uncoated portion along the edge of the active material layer, the negative electrode is manufactured. An inspection process may be provided.

The position of the reference point to be set and the positions of the two points on the end regions 51a and 51b may be changed as appropriate.
The optical detection device may be a device other than the image size measuring instrument 40, for example, a non-contact detection device using a capacitance, a piezoelectric element, a laser beam, and interference and combinations thereof, and a probe. It may be a contact type detecting device.

  The electrode material 23 may be configured to have the coating part 19 only on one side of the long metal foil 18. In this case, the positive electrode 11 includes a positive electrode active material layer 13 on one surface of the positive electrode current collector foil 12, and the negative electrode includes a negative electrode active material layer on one surface of the negative electrode current collector foil.

  ○ The positive electrode 11 and the negative electrode described above are provided with tabs having a shape protruding from one side in order to connect each electrode to an external terminal or the like, but are not limited to this. For example, one side of the electrode A structure in which an uncoated part having a certain width is formed along the line and the uncoated part is used for connection may be used.

(Circle) this invention is applicable also to secondary batteries other than a lithium ion secondary battery, such as a nickel metal hydride battery.
○ It can also be applied to power storage devices other than secondary batteries, such as capacitors.

Next, the technical idea that can be grasped from the above embodiment and other examples will be described below.
(1) A method for inspecting an electrode in which the electrode is for a power storage device.
(2) The method for inspecting an electrode in which the power storage device is a secondary battery.

  L1, L2 ... approximate curve, X0, Y0 ... reference point, W ... coating width, 11 ... positive electrode as electrode, 18 ... long metal foil as long current collector, 19 ... coating part, 19a ... 1st edge, 19b ... 2nd edge, 20 ... exposed part, 23 ... electrode material, 24 ... electrode precursor, 40 ... image dimension measuring device as an optical detection device, 50 ... projecting part, 51a, 51b ... end region.

Claims (4)

A coating portion formed by applying an active material mixture along the longitudinal direction of the long current collector, and an exposed portion of the long current collector exposed to the longitudinal direction of the long current collector In the inspection method of the electrode formed by cutting the electrode material alternately provided to,
The direction along the boundary between the coated part and the exposed part is the X direction, the direction along the surface direction of the coated part and perpendicular to the X direction is the Y direction of the coated part, and the exposed part The edge of the coating part located at the boundary of the first part is the first edge, and the edge of the coating part existing on the opposite side of the first edge is the second edge, in the Y direction When the coating width is a dimension of a straight line connecting the first edge and the second edge along the shortest distance along the line,
When the coating part is detected by an optical detection device for detecting the coating width, the position of the tip of the projecting part that exists in the first edge and projects in the Y direction cannot be detected. If
Set reference points X0, Y0 in the coating part in the image obtained by the optical detection device,
Regarding an end region sandwiching the tip of the protruding portion in the X direction, an approximate curve of a function of the position in the X direction and the position in the Y direction is created, and among the intersections of the approximate curves obtained for each end region A method of inspecting an electrode, wherein an intersection point close to the reference point Y0 in the Y direction is calculated as a position of a tip of the protruding portion.   The electrode inspection method according to claim 1, wherein the approximate curve along the end region has an arc shape.   The electrode inspection method according to claim 1, wherein the electrode is a positive electrode.   The position of the front-end | tip of the said protrusion part is detected after forming the electrode precursor by cut | disconnecting the said electrode material in the shape of the said electrode, and before laminating | stacking the said electrode. The electrode inspection method according to claim 1.

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