JP2019153500A - Manufacturing method of strip electrode - Google Patents

Abstract

To restrain flexure occurring in a non-formation part.SOLUTION: A manufacturing method of strip electrode includes a step of pressing a strip collector foil, having an electrode mixture layer formed in the longitudinal direction, in the thickness direction of the electrode mixture layer, and a step of stretching a non-formation part, where the electrode mixture layer is not formed at both ends of the collector layer in the width direction but is exposed, by means of a stretching roll. The stretching roll has a first roll facing the electrode mixture layer formed on the collector foil and a pair of second and third rolls, placed at both ends of the first roll in the axial direction, and capable of changing the position of the revolving shaft independently for the non-formation part. Medial axis of the first roll is deviated from the medial axis of the pair of second and third rolls in the direction receding from the stretching collector foil, and before starting manufacture of strip electrode, different amounts of the first, second and third rolls are determined based on the curvature amount of the non-formation part, at the time of cutting the strip electrode, manufactured experimentally, with a prescribed length.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for manufacturing a strip electrode.

For example, a strip electrode used in a lithium ion secondary battery or the like has a configuration in which an electrode mixture layer is formed along the longitudinal direction on the surface of a strip-shaped current collector foil. Here, the current collector foil includes a formed portion where the electrode mixture layer is formed and a non-formed portion where the current collector foil is exposed at both ends in the width direction.
As disclosed in Patent Document 1, in such a method for manufacturing a strip electrode, the current collector foil on which the electrode mixture layer is formed is pressed in the thickness direction. By such a pressing step, the electrode mixture layer is compressed, and the electrode density of the manufactured strip electrode can be improved.

  However, in this pressing step, the formation portion where the electrode mixture layer is formed in the current collector foil extends, but the non-formation portion does not extend, so the current collector foil is curved as it is. Therefore, a step of stretching the non-formed part is necessary after the above-described pressing step. In the manufacturing method of the strip-shaped electrode disclosed in Patent Document 1, non-formation is performed by using a drawing roll having a small-diameter portion facing the electrode mixture layer formed in the forming portion and a large-diameter portion facing the non-forming portion. The part is extended.

JP 2014-116141 A

The inventor relates to a method for manufacturing a strip electrode in which a current collector foil having an electrode mixture layer formed thereon is pressed and then a non-formed portion where the electrode mixture layer is not formed in the current collector foil is stretched. I found.
When the non-formed part is drawn using the drawing roll disclosed in Patent Document 1, there arises a problem that the non-formed part at one end of the formed part and the non-formed part at the other end are unevenly curved. And there existed a possibility that the current collector foil might fracture | rupture starting from such a non-formation part, ie, the curved part which generate | occur | produced in the current collector foil.

  In addition, when the press amount of the formation part is increased in order to improve the electrode density, it is necessary to increase the stretch amount of the non-formation part accordingly. Thus, when the stretch amount of the non-formed part increases, the curvature of the non-formed part also increases.

  The present invention has been made in view of such circumstances, and when extending a non-formed part in which the electrode composite material layer is not formed in the current collector foil, a belt-like shape capable of suppressing the curvature generated in the non-formed part An electrode manufacturing method is provided.

  The method for producing a strip electrode according to the present invention includes a step of pressing a strip-shaped current collector foil in which an electrode mixture layer is formed along a longitudinal direction in a thickness direction of the electrode mixture layer, and the current collector foil. Stretching the non-formed part where the current collector foil is exposed without forming the electrode mixture layer at both ends in the width direction by a stretching roll, and the stretching method, A roll is disposed at both ends of the first roll in the axial direction of the first roll facing the electrode mixture layer formed on the current collector foil, and is opposed to the non-forming portion and independently positioned at the rotation axis. A pair of second rolls and third rolls that can be changed, and the central axis of the first roll extends with respect to the central axes of the pair of second rolls and third rolls. It is shifted in a direction away from the foil, and production of the strip electrode is started. Each of the first roll, the second roll, and the third roll based on the amount of bending of the non-formed part when the strip-like electrode manufactured on a trial basis is cut to a predetermined length before. Determine the amount of step.

  In the method for manufacturing a strip electrode according to the present invention, before starting the manufacture of the strip electrode, based on the bending amount of the non-formed portion when the strip electrode manufactured on a trial basis is cut to a predetermined length, A step amount between one roll and each of the second roll and the third roll is determined. Therefore, the curvature which generate | occur | produces in a non-formation part can be suppressed.

  According to the present invention, it is possible to suppress the bending that occurs in the non-formed part.

3 is a plan view of a strip electrode 40. FIG. It is II-II sectional drawing of FIG. It is a side view of the manufacturing apparatus of the strip | belt-shaped electrode which concerns on embodiment. It is sectional drawing of the extending | stretching roll 30 which concerns on embodiment. It is a typical side view of the extending | stretching roll 30 which concerns on embodiment. It is a flowchart which shows a series of flows which determine the amount of level | step difference settings of the extending | stretching roll 30 concerning embodiment, especially the 2nd roll 32a and the 3rd roll 32b. It is a top view which shows the curvature amount of the non-formation part 41b1 when the strip | belt-shaped electrode 40 concerning embodiment is cut | disconnected by predetermined length and the sample of the strip | belt-shaped electrode 40 is manufactured. It is sectional drawing of the extending | stretching roll 300 which concerns on a comparative example. It is a typical side view of the extending | stretching roll 300 which concerns on a comparative example. It is the graph which compared and showed the change of the level | step difference by the position in the extending | stretching roll 30 which concerns on embodiment, and the extending | stretching roll 300 which concerns on a comparative example. It is a graph which shows an example of the calibration curve of curvature amount and level | step difference correction amount.

Embodiments of the present invention will be described below with reference to the drawings.
As a matter of course, the right-handed xyz orthogonal coordinates shown in FIGS. 1 and 2 and other drawings are convenient for explaining the positional relationship of the components. Usually, the z-axis positive direction is vertically upward, and the xy plane is a horizontal plane, which is common between the drawings.

<Embodiment>
<Configuration of strip electrode>
First, with reference to FIG. 1 and FIG. 2, the structure of the strip electrode manufactured by the strip electrode manufacturing apparatus according to the first embodiment will be described. FIG. 1 is a plan view of the strip electrode 40. 2 is a cross-sectional view taken along the line II-II in FIG. 1, and is also a cross-sectional view taken along the line II-II in FIG.

  The strip electrode 40 is a strip electrode for a positive electrode or a negative electrode used in, for example, a lithium ion secondary battery. As shown in FIGS. 1 and 2, the strip electrode 40 includes a current collector foil 41 and an electrode mixture layer 42. Here, the current collector foil 41 has a current collector at the both ends of the current collector foil 41 in the width direction (y-axis direction) and the forming portion 41a where the electrode material layer 42 is formed. Non-formation part 41b1 and 41b2 which foil 41 exposed are provided. As shown in FIG. 2, the electrode mixture layer 42 is formed on both surfaces of the current collector foil 41. However, the electrode mixture layer 42 may be formed on one surface of the current collector foil 41.

  As shown in FIG. 1, the electrode mixture layer 42 is formed in a band shape on the surface of the current collector foil 41 along the longitudinal direction (x-axis direction) of the belt-shaped current collector foil 41. On the other hand, at both ends of the current collector foil 41 in the width direction (y-axis direction), the current collector foil 41 is exposed in a strip shape along the longitudinal direction (x-axis direction). Therefore, the current collector foil 41 includes a forming portion 41a extending in a strip shape in the longitudinal direction (x-axis direction) corresponding to the electrode mixture layer 42, and a pair of non-forming portions extending substantially in parallel via the forming portion 41a. 41b1 and 41b2. That is, the strip electrode 40 has a configuration that is line-symmetric with respect to the center line CL. As an example, the width of the forming portion 41a is about 210 mm, and the width of the pair of non-forming portions 41b1 and 41b2 is about 15 mm.

  Although not shown, the strip electrode 40 is cut along the center line CL in a subsequent process and divided into two. Then, a wound electrode body is manufactured by laminating and winding four pieces of the divided negative electrode strip, the separator, the divided positive electrode strip, and the separator in this order. In the wound electrode body, the positive electrode terminal is joined to the non-forming portions 41b1 and 41b2 of the strip electrode for the positive electrode, and the negative electrode terminal is joined to the non-forming portions 41b1 and 41b2 of the strip electrode for the negative electrode. For example, a porous film having a three-layer laminated structure of PE (polyethylene) / PP (polypropylene) / PE (polyethylene) can be used for the separator.

The case where the strip electrode 40 is for a positive electrode will be described. As the current collector foil 41, for example, an aluminum foil can be used. As the positive electrode active material constituting the electrode mixture layer 42, for _{example, LiCoO 2, LiMnO 2, LiMn} 2 O 4, LiNiO 2, LiNi x Co (1-x) O 2, and LiNi _x Co _y Mn _{(1- xy)} A lithium-containing composite oxide such as O ₂ is included (wherein 0 <x <1, 0 <y <1). The composition of the electrode material for the positive electrode active material layer is not particularly limited, and a known composition can be applied.

  The electrode mixture layer 42 can contain, for example, a conductive material such as carbon powder and a binder such as polyvinylidene fluoride (PVdF) as a solid content in addition to the above positive electrode active material. Furthermore, a dispersing agent such as carboxymethyl cellulose Na salt (CMC) can be included as a solid content as necessary. As a solvent constituting the electrode mixture layer 42, water, N-methyl-2-pyrrolidone (NMP), or the like can be used.

  The case where the strip electrode 40 is for a negative electrode will be described. As the current collector foil 41, for example, a copper foil can be used. Examples of the negative electrode active material constituting the electrode mixture layer 42 include transition metal oxide / transition metal nitride capable of doping / dedoping of carbon such as graphite, metallic lithium, lithium alloy, and lithium ions. / Transition metal sulfides and combinations thereof. The composition of the electrode material for the negative electrode active material layer is not particularly limited, and a known composition can be applied.

  For example, the electrode mixture layer 42 may contain a binder such as a styrene-butadiene copolymer (SBR) as a solid content in addition to the negative electrode active material. Furthermore, a dispersing agent such as carboxymethyl cellulose Na salt (CMC) can be included as a solid content as necessary. As a solvent constituting the electrode mixture layer 42, water or the like can be used.

<Overall configuration of strip electrode manufacturing apparatus>
Next, with reference to FIG. 3, the whole structure of the manufacturing apparatus and manufacturing method of the strip | belt-shaped electrode which concerns on 1st Embodiment is demonstrated. FIG. 3 is a side view of the strip electrode manufacturing apparatus according to the first embodiment. As shown in FIG. 3, the strip electrode manufacturing apparatus according to this embodiment includes a pair of press rolls 11, 12, three guide rolls 21 to 23, and a stretching roll 30.

  First, as shown in FIG. 3, a current collector foil 41 on which an electrode mixture layer 42 is formed by coating, transfer, or the like is carried into the manufacturing apparatus from the negative x-axis direction, and a pair of press rolls 11, 12. Is pressed in the thickness direction. As an example, the diameter of the press rolls 11 and 12 is about 400 mm, and a hydraulic press having a pressurization capacity of 30 to 50 t can be used. By this pressing step, the electrode mixture layer 42 is compressed, and the electrode density of the produced strip electrode 40 can be improved.

  Here, as described above, FIG. 2 is a cross-sectional view taken along the line II-II of FIG. In FIG. 2, the press rolls 11 and 12 are also virtually shown by a two-dot chain line along with a cross-sectional view of the strip electrode 40. As shown in FIG. 2, when the current collector foil 41 on which the electrode mixture layer 42 is formed is pressed, the forming portion 41 a in the current collector foil 41 is compressed in the thickness direction (z-axis direction) and in the x-axis direction. To grow. On the other hand, the non-forming portions 41b1 and 41b2 are not compressed in the thickness direction (z-axis direction), and thus do not extend in the x-axis direction. Therefore, as it is, the current collector foil 41 composed of the forming portion 41a and the non-forming portions 41b1 and 41b2 is curved.

  Therefore, as shown in FIG. 3, after the current collector foil 41 on which the electrode mixture layer 42 is formed is pressed by the press rolls 11 and 12, the non-formed portions 41 b 1 and 41 b 2 of the current collector foil 41 are stretched by the stretching roll 30. To do. Therefore, the current collector foil 41 with the electrode mixture layer 42 pressed by the press rolls 11 and 12 is guided to the stretching roll 30 by the guide roll 21. By the guide roll 21, the conveying direction of the current collector foil 41 with the electrode mixture layer 42 is changed from the x-axis positive direction to the z-axis negative direction and the x-axis negative direction.

  Thus, the non-formation part 41b1 and 41b2 of the current collection foil 41 are extended | stretched with the extending | stretching roll 30, and the strip | belt-shaped electrode 40 is manufactured. In the example of FIG. 3, the transport direction of the strip electrode 40 that has passed through the stretching roll 30 is changed from the x-axis positive direction to the z-axis positive direction by the guide roll 22, and further, the guide roll 23 changes the z-axis positive direction. To x-axis positive direction.

  Note that the order of the stretching process by the stretching roll 30 and the pressing process by the press rolls 11 and 12 may be reversed. As a matter of course, the number and arrangement of the guide rolls 21 to 23 for changing the transport direction are not limited to the example shown in FIG. 3 and may be determined as appropriate.

<Detailed Configuration of Stretching Roll 30>
Next, with reference to FIG. 4, FIG. 5, the detailed structure of the extending | stretching roll 30 which concerns on 1st Embodiment is demonstrated. FIG. 4 is a cross-sectional view of the stretching roll 30 according to the first embodiment. FIG. 5 is a schematic side view of the stretching roll 30 according to the first embodiment. The strip electrode manufacturing apparatus according to the first embodiment has one feature in the configuration of the stretching roll 30. As shown in FIG. 4, the stretching roll 30 includes a first roll 31 that faces the electrode mixture layer 42 formed in the forming portion 41 a and a non-forming portion that is formed at both ends in the width direction of the forming portion 41 a. The second roll 32a facing the non-formed part 41b1 at one end (y-axis positive side) and the third roll 32b facing the non-formed part 41b2 at the other end (y-axis negative side) are provided. In addition, although the 2nd roll and the 3rd roll are paired, it can rotate independently, respectively.

  As shown in FIG. 4, the first roll 31 has a hollow cylindrical shape whose longitudinal direction is the y-axis direction. By making the first roll 31 have a hollow structure, the weight can be reduced. However, the first roll 31 may not have a hollow structure. Bearings B <b> 1 a and B <b> 1 b are fitted into through holes provided at the center of both bottom surfaces of the first roll 31. A shaft (first shaft) S1 extending in the y-axis direction is fitted into the bearings B1a and B1b. That is, the first roll 31 can rotate about the shaft S1 which is fixed and does not rotate, as the rotation axis. FIG. 4 shows the central axis A1 of the shaft S1. For example, when the electrode mixture layer 42 contacts the first roll 31, the first roll 31 rotates.

  As shown in FIG. 4, the pair of second roll 32 a and third roll 32 b are disposed at both ends of the first roll 31 in the direction of the central axis A <b> 1 (y-axis direction). As an example, the diameters of the second roll 32 a and the third roll 32 b are approximately the same as the diameter of the first roll 31. Each of the pair of second roll 32a and third roll 32b has a cylindrical shape whose longitudinal direction is the y-axis direction. A bearing B2a is fitted into the inner peripheral surface of the second roll 32a. A cylindrical shaft S2a extending in the y-axis direction is fitted into the bearing B2a.

  Similarly, as shown in FIG. 4, a bearing B2b is fitted into the inner peripheral surface of the third roll 32b. A cylindrical shaft S2b extending in the y-axis direction is fitted into the bearing B2b. That is, the second roll 32a and the third roll 32b can rotate about the shafts S2a (second shaft) and S2b (third shaft) that can change the position of the rotation axis and do not rotate. Here, the shafts S2a and S2b each have an independent central axis, the shaft S2a has a central axis A2, and the shaft S2b has a central axis A3. That is, the second roll 32a and the third roll 32b can rotate independently of each other. As shown in FIG. 4, the non-formation part 41b contacts the 2nd roll 32a and the 3rd roll 32b, and the 2nd roll 32a and the 3rd roll 32b rotate.

  As shown in the schematic side view of FIG. 5, in FIG. 5, at positions P <b> 1 to P <b> 3 where the non-forming portion 41 b 2 is in contact with the third roll 32 b, there is a step so that the first roll 31 is recessed from the third roll 32 b. Is provided. FIG. 4 is a cross-sectional view at a position P2 where the step is maximized. As shown in FIG. 4, at the position P2, this level difference is larger than the thickness of the electrode mixture layer 42 after the pressing process. Therefore, the non-forming part 41b2 can be brought into contact with the third roll 32b and stretched with a predetermined tension.

  Here, in the schematic side view of FIG. 5, the third roll 32b has been described, but the same applies to the second roll. In P1 to P3 where the non-forming portion 41b1 is in contact with the second roll 32a, a step is provided so that the first roll 31 is recessed from the second roll 32a. FIG. 4 is a cross-sectional view at a position P2 where the step is maximized. As shown in FIG. 4, at the position P2, this level difference is larger than the thickness of the electrode mixture layer 42 after the pressing process. Therefore, the non-forming part 41b1 can be brought into contact with the second roll 32a and stretched with a predetermined tension.

  Furthermore, since the 2nd roll 32a and the 3rd roll 32b can each rotate independently, as shown in FIG. 4, for example, the level | step difference of the 1st roll 31 and the 2nd roll 32a is 1st. Compared with the step between the roll 31 and the third roll 32b, the step can be provided so as to be more concave. The formation of the step between the second roll 32a and the third roll 32b is arbitrary, and can be set so as to suppress the bending at the non-forming portions 41b1 and 41b2. This will be described later with reference to FIG.

  Here, as shown in FIGS. 4 and 5, in the stretching roll 30 according to the present embodiment, the rotation axis (center axis A1) of the first roll 31 and the rotation axis (center axis A2) of the second roll 32a are used. It is shifted. Similarly, the rotation axis (center axis A1) of the first roll 31 and the rotation axis (center axis A3) of the third roll 32b are shifted. As shown in FIG. 4, the second roll 32a includes a motor M1, and the third roll 32b includes a motor M2. Since the motor M1 and the motor M2 independently control the positions of the second shaft and the third shaft, which are the rotation axes of the second roll 32a and the third roll 32b, respectively, the second roll 32a and the third roll 32b The position of the rotating shaft can be shifted independently of each other. The motor M1 and the motor M2 are servo motors, for example.

  As shown in FIG. 5, the central axis of the first roll 31 with respect to the central axis A <b> 2 of the second roll 32 a and the central axis A <b> 3 of the third roll 32 b in the direction away from the forming portion 41 a where the first roll 31 extends. Shift A1. That is, the concave step of the first roll 31 with respect to the second roll 32a and the third roll 32b is gradually increased from the position P1 to the position P2, and the concave step is gradually decreased from the position P2 to the position P3. To do. Here, the position P1 is a position where the non-forming part 41b1 enters the second roll 32a and the non-forming part 41b2 enters the third roll 32b. The position P3 is a position where the non-forming part 41b1 is separated from the second roll 32a and the non-forming part 41b2 is detached from the third roll 32b. With such a configuration, when the non-forming portions 41b1 and 41b2 are stretched, the non-forming portions 41b1 and 41b2 can be independently stretched. be able to.

Next, with reference to FIG. 6, a series of flows for setting the step amount of the stretching roll 30, particularly the second roll 32 a and the third roll 32 b before the start of the main production of the electrode will be described. FIG. 6 is a flowchart showing a series of flows for determining the step amount setting of the stretching roll 30 according to the embodiment, particularly the second roll 32a and the third roll 32b. Here, the “level difference” indicates the height of the level difference.
Before starting the production of the strip electrode, a sample of the strip electrode having a predetermined length is produced on a trial basis (step S1). Next, the bending amount is measured (step S2). When the bending amount is Nmm or less (step S3: YES), the production of the strip electrode is started (step S5). On the other hand, when the bending amount is larger than Nmm (step S3: NO), the setting of the step amount of the second roll 32a and the third roll 32b is changed (step S4), and the process returns to step S1. Steps S1 to S4 are repeated until the bending amount is Nmm or less. As an example, N = about 3 mm.

Details of step S1 to step S5 will be described below.
<Step S1: Production of strip electrode sample>
In step S1, a sample of the strip electrode 40 is manufactured as a test. The sample of the strip electrode 40 is formed by stretching the non-formed portions 41b1 and 41b2 in which the electrode mixture layer 42 is not formed on the current collector foil 41, cutting it at a predetermined length w, and further including the non-formed portion 41b1. It is manufactured by cutting in the longitudinal direction at the forming portion 41a located at the center including the non-forming portion 41b2. As an example, a sample of the strip electrode 40 is cut by a length of 2 m.

<Step S2: Measurement of bending amount>
In step S2, the amount of bending is measured. The amount of bending can be measured using, for example, a scale.
Here, with reference to FIG. 7, the “bending amount” in the present specification will be described.
FIG. 7 is a plan view showing the amount of curvature of the non-forming portion 41b1 when the strip electrode 40 according to the embodiment is cut to a predetermined length to produce a sample of the strip electrode 40. FIG.

In this specification, when the sample of the strip electrode 40 is manufactured as described above, the curvature generated in the non-forming portions 41b1 and 41b2 is defined as the “curvature amount”. More specifically, as shown in FIG. 7, the bending amount in which the center (w / 2) portion of the predetermined length w is curved with respect to the line connecting the both ends in the longitudinal direction of the cutting portion is the bending amount C. It is. As an example, when the predetermined length w is 2 m, a sample with a bending amount of about 3 mm is obtained. The strip electrode 40 may be cut by slitting or the like.
FIG. 7 is a diagram showing the amount of bending of the non-forming portion 41b1 on the second roll side, but the definition of the amount of bending of the non-forming portion 41b2 on the third roll side is the same.

<Step S3: Determination of bending amount>
In step S3, the measurement results of the bending amounts of the non-formed portions 41b1 and 41b2 in the manufactured sample of the strip electrode 40 are respectively determined. When the bending amounts of the non-forming portions 41b1 and 41b2 are both Nmm or less (step S3: YES), the process proceeds to step S5, and manufacturing of the strip electrode is started. N is an arbitrary value and can be set as appropriate depending on the desired accuracy. As an example, N = about 3 mm.

  On the other hand, when at least one of the bending amounts of the non-forming portions 41b1 and 41b2 is larger than Nmm (step S3: NO), the process proceeds to step S4, and the setting of the step amount of the second roll 32a and the third roll 32b is changed. Return to step S1.

<Step S4: Setting change of step amount of second roll and third roll>
In step S4, the setting change of the step amount of the stretching roll 30 is performed. Here, the reason why the non-formed portions 41b1 and 41b2 are curved is that the non-formed portions are not sufficiently stretched. Therefore, in order to extend the non-forming parts 41b1 and 41b2 more, the setting of the step amount of the second roll and the third roll is changed. In other words, the degree of contact of each roll with respect to each non-forming portion is changed by changing the level difference between the first roll 31 and the second roll 32a and the level difference between the first roll 31 and the third roll 32b. The tension is also changed.

For example, the step amount can be changed based on a calibration curve. An example of how to obtain the calibration curve used in step S4 will be described later. Here, the step amounts of the second roll 32a and the third roll 32b can be set independently. Accordingly, it is possible to independently set the step amount corresponding to the curvature amount of the manufactured sample of the strip electrode 40 for the second roll 32a and the third roll 32b.
After changing the step amount based on the calibration curve, the process returns to step S1. Steps S1 to S4 are repeated until the bending amount is equal to or less than the desired amount.

<Step S5: Production of strip electrode>
Based on the level difference between the second roll and the third roll determined in step S4, the production of the strip electrode is started.
The above is a series of flows for determining the step amount of the stretching roll 30, in particular, the second roll 32a and the third roll 32b, before starting the electrode production. In the first sample manufacture of the strip electrode 40, each step can be started after the step amount of each roll is set to an arbitrary value, for example, 1 mm.

<Configuration of Stretching Roll 300 According to Comparative Example>
Next, with reference to FIG. 8, FIG. 9, the structure of the extending | stretching roll 300 which concerns on a comparative example is demonstrated. FIG. 8 is a cross-sectional view of a stretching roll 300 according to a comparative example. FIG. 9 is a schematic side view of a stretching roll 300 according to a comparative example. As shown in FIG. 8, the stretching roll 300 according to the comparative example includes a small diameter portion 310 facing the forming portion 41 a where the electrode mixture layer 42 is formed, and a pair of large diameter portions 320 facing the non-forming portion 41 b. Are integrally formed.

  As shown in FIG. 8, the stretching roll 300 has a cylindrical shape with the y-axis direction as the longitudinal direction. Bearings B <b> 1 a and B <b> 1 b are fitted in through-holes that penetrate the center portions of both bottom surfaces of the stretching roll 300 in the longitudinal direction (y-axis direction). A shaft S1 extending in the y-axis direction is fitted into the bearings B1a and B1b. That is, the stretching roll 300 can rotate about the shaft S1 as a rotation axis. FIG. 8 shows the central axis A1 of the shaft S1.

  As shown in the schematic side view of FIG. 9, in the stretching roll 300 according to the comparative example, naturally, the step between the small diameter portion 310 and the large diameter portion 320 is constant regardless of the positions P1 to P3. Here, FIG. 10 is a graph showing a comparison of the change in the level difference depending on the position in the stretching roll 30 according to the embodiment and the stretching roll 300 according to the comparative example. The horizontal axis indicates the position (P1 to P3) on the stretching roll, and the vertical axis indicates the step (mm).

  FIG. 8 is a cross-sectional view at position P2 shown in FIG. As shown in FIG. 8, the step between the small diameter portion 310 and the large diameter portion 320 is larger than the thickness of the electrode mixture layer 42 after the pressing process. Therefore, the non-forming parts 41b1 and 41b2 can be brought into contact with the large diameter part 320 and stretched with a predetermined tension.

  As shown in FIGS. 9 and 10, in the stretching roll 300 according to the comparative example, the step between the small diameter portion 310 and the large diameter portion 320 is constant regardless of the position. For this reason, when the non-forming portions 41b1 and 41b2 are extended, the non-forming portions 41b1 and 41b2 are rapidly extended, and curved portions are formed in the non-forming portions 41b1 and 41b2. And there existed a possibility that the current collection foil 41 might fracture | rupture starting from the curved part which generate | occur | produced in such a non-formation part 41b. When the pressing amount of the forming portion 41a is increased in order to improve the electrode density, it is necessary to increase the stretching amount of the non-forming portions 41b1 and 41b2 accordingly. Thus, when the stretch amount of the non-forming parts 41b1 and 41b2 increases, a curved part is likely to occur in the non-forming parts 41b1 and 41b2.

<Effect according to the embodiment>
On the other hand, as shown in FIGS. 5 and 10, in the stretching roll 30 according to the embodiment, when the non-forming portions 41b1 and 41b2 enter, the first roll 31 with respect to the second roll 32a and the third roll 32b. When the non-formed portions 41b1 and 41b2 are detached, the recessed step gradually decreases. Furthermore, the 2nd roll 32a and the 3rd roll 32b can rotate independently, respectively, and can set the amount of level | step differences each independently. With such a configuration, when the non-forming portions 41b1 and 41b2 are stretched, the non-forming portions 41b1 and 41b2 are gradually and independently stretched, so that the curved portions generated in the non-forming portions 41b1 and 41b2 are suppressed. Can do.

<How to obtain a calibration curve>
Hereinafter, an example of how to obtain the calibration curve used in step S4 of FIG. 6 will be described.
First, a lithium positive electrode was manufactured as a strip electrode. Specifically, the current collector foil 41 on which the electrode mixture layer 42 was formed was pressed in the thickness direction at a linear pressure of 1.0 t / cm using the press roll 11. The conveyance speed was 10 m / min, and the tension was 100N.

  Next, the step amount between the first roll 31 and the second roll 32a and the step amount between the first roll 31 and the third roll 32b were set to 1 mm as initial values, respectively, and the non-formed part was stretched. As the roll diameters of the first roll, the second roll, and the third roll, those having an inner diameter of 120 mm were used. Next, a strip electrode for condition setting was prepared. Specifically, the elongated strip electrode 40 was cut into 2 m in the longitudinal direction by slitting, and a plurality of strip electrodes for condition determination having a curvature amount of 3 mm, 6 mm, 8 mm, and 10 mm were prepared.

As a result of the evaluation by experiment, a step amount necessary for setting the bending amount of each condition setting strip electrode to 0 mm was obtained and plotted as a step correction amount in the graph of FIG. FIG. 11 is a graph showing an example of a calibration curve between the bending amount and the step correction amount.
For example, in the case of a strip electrode for conditioning with a bending amount of 3 mm, the step correction amount for setting the bending amount to 0 mm was 0.5 mm as shown in FIG. Similarly, in the case of a strip electrode for condition determination having a bending amount of 6 mm, the step correction amount for setting the bending amount to 0 mm was 1 mm as shown in FIG. In the case of the strip electrode for condition setting with a bending amount of 8 mm, the step correction amount for setting the bending amount to 0 mm was 1.2 mm as shown in FIG. In the case of the strip electrode for condition setting with a bending amount of 10 mm, the step correction amount for setting the bending amount to 0 mm was 1.5 mm as shown in FIG.

From the above results, a calibration curve represented by the following formula was obtained (R ² = 0.9919).
Step correction amount [mm] = 0.14 * curvature amount [mm] +0.104
That is, there is a linear relationship between the bending amount and the step amount. For example, in step S4 in FIG. 6, for example, when the bending amount is 6 mm, the step correction amount can be calculated as 1 mm using the calibration curve. Therefore, for example, when the bending amount is 6 mm, the bending amount can be reduced to 0 mm by adding 1 mm to the step.
When the level difference was determined before the actual production of the electrode using the calibration curve, the defect rate compared to the conventional method could be reduced by 20% or more. The defect rate in the present embodiment indicates, for example, a case where the bending amount is larger than 3 mm. For example, a strip electrode for condition setting is manufactured for each manufacturing lot, the amount of bending is investigated, and the amount of step in the actual manufacturing is determined.

  In addition, this invention is not limited to the said embodiment, It is possible to change suitably in the range which does not deviate from the meaning.

11, 12 Press rolls 21-23 Guide roll 30 Stretching roll 31 First roll 32a Second roll 32b Third roll 40 Strip electrode 41 Current collector foil 41a Forming part 41b1, 41b2 Non-forming part 42 Electrode mixture layer A1, A2 Center Axis B1a, B1b Bearing B2a, B2b Bearing S1, S2a, S2b Shaft

Claims (1)

A step of pressing the strip-shaped current collector foil in which the electrode mixture layer is formed along the longitudinal direction in the thickness direction of the electrode mixture layer;
Stretching the non-formed portion where the current collector foil is exposed without forming the electrode mixture layer at both ends in the width direction of the current collector foil, using a stretching roll. And
The stretching roll is
A first roll facing the electrode mixture layer formed on the current collector foil;
A pair of second rolls and third rolls that are disposed at both axial ends of the first roll and that are capable of independently changing the position of the rotary shaft, facing the non-forming portion;
The central axis of the first roll is shifted in a direction away from the extending current collecting foil with respect to the central axis of the pair of second roll and third roll,
Before starting production of the strip electrode, the first roll and the second roll based on the amount of bending of the non-formed part when the strip electrode manufactured on a trial basis is cut to a predetermined length. And determining a step amount from each of the third rolls,
A manufacturing method of a strip electrode.

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