Electrode plate

Abstract

The electrode sheet (20) comprises a collector plate (18) and a mixture sheet (6), and the mixture sheet (6) is composed of a dry electrode mixture and is laminated on the surface of the collector plate (18). The mixture sheet (6) has a window section (6b) surrounded by the dry electrode mixture over the entire circumference, and the collector plate (18) is exposed at the window section (6b). In a cross-section orthogonal to the direction in which the collector plate (18) and the mixture sheet (6) extend, the angle formed by the side wall of the mixture sheet (6) in the window (6b) and the surface of the collector plate (18) is 75-105 DEG.

Description

Technical Field

[0001] The present disclosure relates to an electrode sheet. Background Art

[0002] Patent document 1 describes a device that supplies particles to the gap between a pair of compression rollers, compresses the particles into a sheet to form a coating, and laminates the coating on a substrate. The device includes a stepped roller with a blade on the circumference, and removes a portion of the coating with the stepped roller. In addition, Patent document 1 describes the use of the device to manufacture a functional sheet used for a storage device such as a secondary battery or a capacitor. In addition, a collector plate is exemplified as a substrate, and an electrode mixture is exemplified as a coating.

[0003] [Prior art literature]

[0004] [Patent Document]

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-017962 Summary of the invention

[0006] [Problems to be solved by the invention]

[0007] When the electrode sheet is manufactured by laminating the electrode mixture sheet on the current collector plate using the above-mentioned apparatus, the exposed portion of the current collector plate can be formed by removing a portion of the electrode mixture sheet. The exposed portion can be used as a connection portion for a current collector lead, etc.

[0008] There is a constant demand for improving the quality of power storage devices. As a result of intensive research, the present inventors have found that there is room for improvement in the quality of conventional power storage devices.

[0009] The present disclosure has been made in view of such circumstances, and an object of the present disclosure is to provide a technology for improving the quality of a power storage device.

[0010] [Technical solutions for solving technical problems]

[0011] One scheme of the present disclosure is an electrode sheet. The electrode sheet includes a collector plate and a mixture sheet, the mixture sheet is composed of a dry electrode mixture and is stacked on the surface of the collector plate. The mixture sheet has a window portion surrounded by the dry electrode mixture all around, and the collector plate is exposed at the window portion. In a cross section orthogonal to the extension direction of the collector plate and the mixture sheet, the angle between the side wall of the mixture sheet in the window portion and the surface of the collector plate is greater than 75° and less than 105°.

[0012] Any combination of the above-mentioned constituent elements and any conversion of the expressions of the present disclosure between methods, apparatuses, systems, etc. are also effective as aspects of the present disclosure.

[0013] Effects of the Invention

[0014] According to the present disclosure, it is possible to improve the quality of the power storage device. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of a molding device for a mixed drug sheet according to an embodiment.

[0016] Figure 2 It is an exploded perspective view of the forming unit.

[0017] Figure 3 is a cross-sectional view of the forming unit.

[0018] Figure 4 (A) is a top view of the electrode sheet. Figure 4 (B) is along Figure 4 Cross-sectional view of line A-A of (A).

[0019] Figure 5 (A) is a top view of the electrode sheet to which the current collecting lead is joined. Figure 5 (B) is an enlarged cross-sectional view of the window portion. DETAILED DESCRIPTION

[0020] Hereinafter, with reference to the accompanying drawings, the present disclosure will be described based on a preferred embodiment. The embodiments do not limit the present disclosure, but are merely illustrative, and all the features and combinations described in the embodiments are not the substantive contents of the present disclosure. The same or equivalent components, members, and processes shown in the drawings are marked with the same figure numerals, and repeated descriptions are appropriately omitted. In addition, the scales or shapes of the various parts shown in the figures are set for ease of description and are not to be interpreted restrictively unless otherwise specified. In addition, when the terms "first", "second", etc. are used in this specification or claims, unless otherwise specified, the terms do not indicate any order or importance, and are only used to distinguish a certain structure from other structures. In addition, in each of the drawings, a part of the components that are not important in describing the embodiments will be omitted from display.

[0021] Figure 1 It is a schematic diagram of a forming device 1 for a composite sheet 6 of an embodiment. The forming device 1 for the composite sheet 6 includes a support roller 2 and a forming roller 4. The support roller 2 supports the composite sheet 6 with a circumferential surface 2a. As an example, the composite sheet 6 is a strip that is longer in the conveying direction, and is monolithicized into a plurality of electrode sheets after being stacked on a collector plate, and is used in a storage device such as a secondary battery or a capacitor. The composite sheet 6 is formed, for example, in the following manner. That is, a powder of a dry electrode mixture as a raw material of the composite sheet 6 is supplied from a known storage portion such as a hopper to a gap between a pair of compression rollers. The pair of compression rollers rotate in opposite directions to each other, and compress the dry electrode mixture supplied to the gap into a sheet. Thus, the composite sheet 6 is formed.

[0022] The composite sheet 6 is continuously fed out from the gap between the pair of compression rollers. The support roller 2 is located on the downstream side of the pair of compression rollers, and supports the composite sheet 6 with the circumferential surface 2a while conveying the composite sheet 6 to the downstream side by its own rotation. Alternatively, the composite sheet 6 may be extended to a target thickness during conveyance.

[0023] The dry electrode mixture contains an electrode active material and contains a conductive agent and a binding material (binder) as needed. In the case of a general lithium-ion secondary battery, regarding the electrode active material, when it is a positive electrode, it is lithium cobaltate or lithium iron phosphate, etc., and when it is a negative electrode, it is graphite, etc. In addition, the conductive agent is graphite, carbon black, acetylene black, etc. The binding material is polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), etc. In addition, regarding the dry electrode mixture, the content of the solvent is less than 5% by mass, or less than 3% by mass, and then 0% by mass relative to the entire mass of the dry electrode mixture. Therefore, the drying furnace of the mixture sheet 6 can be omitted. In addition, it can also be that the dry electrode mixture contains a very small amount of solvent to the extent that the drying furnace can be omitted.

[0024] The posture of the forming roller 4 is determined so that the rotation axis is parallel to the rotation axis of the support roller 2. Furthermore, the peripheral surface 4a is opposite to the peripheral surface 2a of the support roller 2 at a predetermined interval. In addition, the forming roller 4 rotates together with the support roller 2. The support roller 2 and the forming roller 4 rotate in opposite directions. As an example, the support roller 2 and the forming roller 4 rotate at the same rotation speed.

[0025] The forming roller 4 has a forming unit 7 on the circumferential surface 4a, and the forming unit 7 is composed of a cutting clamp 8, a removal pad 10 and an elastic body 12. The forming roller 4 rotates together with the support roller 2, and presses the cutting clamp 8 against the composite sheet 6 supported by the support roller 2. As a result, the composite sheet 6 is partially cut. In addition, the forming roller 4 makes the cut portion 6a of the composite sheet 6 adhere to the surface of the removal pad 10 and pulls it away from the composite sheet 6. Since the cut portion 6a is removed, a through hole is formed in the composite sheet 6 that penetrates the composite sheet 6 in the thickness direction. The through hole constitutes the window portion 6b.

[0026] Figure 2 It is an exploded perspective view of the forming unit 7. Figure 3 is a cross-sectional view of the forming unit 7. Figure 3 In the figure, the illustration of the compound tablet 6 is omitted. Figure 2As shown, the cutting jig 8 is frame-shaped. The cutting jig 8 of this embodiment is a rectangular frame-shaped, and has the first cutting blade 14a to the fourth cutting blade 14d combined into a rectangular shape. The first cutting blade 14a and the second cutting blade 14b are arranged at a predetermined interval along the circumferential direction of the forming roller 4, and extend in the axial direction of the forming roller 4. In the rotation direction A of the forming roller 4, the first cutting blade 14a is located at the front end side, and the second cutting blade 14b is located at the rear end side. The third cutting blade 14c and the fourth cutting blade 14d are arranged at a predetermined interval along the axial direction of the forming roller 4, and extend in the circumferential direction of the forming roller 4. The blade tips of the first cutting blade 14a and the second cutting blade 14b extend in a straight line. The blade tips of the third cutting blade 14c and the fourth cutting blade 14d extend in a curved shape parallel to the peripheral surface 4a. Each blade faces the radial outer side of the forming roller 4. In addition, the cutting jig 8 can also be a frame-shaped such as a rounded rectangle, a perfect circle, an ellipse, etc.

[0027] The removal pad 10 is arranged in the frame of the cutting jig 8. Therefore, when viewed from the radial direction of the forming roll 4, the removal pad 10 is surrounded by the first cutting edge 14a to the fourth cutting edge 14d. The surface 10a of the removal pad 10 facing the support roll 2 has a larger surface roughness than the peripheral surface 2a of the support roll 2. For example, the arithmetic mean roughness Ra of the surface 10a is larger than the arithmetic mean roughness Ra of the peripheral surface 2a. The surface roughness of the surface 10a can be increased by a known roughening treatment such as sandblasting.

[0028] The elastic body 12 supports the removal pad 10. The elastic body 12 can be formed by a known spring or sponge. The elastic body 12 of the present embodiment is, for example, formed by a coil spring and is arranged between the cutting fixture 8 and the removal pad 10. The cutting fixture 8 has a base 16 in a frame. The end of the elastic body 12 on the cutting fixture 8 side is fixed to the base 16. The end of the elastic body 12 on the removal pad 10 side is fixed to the back of the removal pad 10. When the removal pad 10 is opposite to the support roller 2, the elastic body 12 applies force to the removal pad 10 toward the cutting portion 6a side by its own elastic force. In addition, when the removal pad 10 is separated from the support roller 2 due to the rotation of the support roller 2 and the forming roller 4, the removal pad 10 is pulled closer to the forming roller 4 side by its own elastic force. The elastic body 12 plays the same role as the ejection member of the die. In addition, the removal pad 10 itself may also have elasticity. In this case, the removal pad 10 also has the elastic body 12.

[0029] like Figure 3As shown, the front end of the cutting jig 8 in the rotation direction A of the forming roll 4 protrudes further toward the support roll 2 side than the front end of the removal pad 10. In addition, the rear end of the cutting jig 8 in the rotation direction A protrudes further toward the support roll 2 side than the rear end of the removal pad 10. That is, the blade tips of the first cutting blade 14a and the second cutting blade 14b protrude toward the support roll 2 side relative to the surface 10a of the removal pad 10. On the other hand, the middle portion of the removal pad 10 in the rotation direction A protrudes further toward the support roll 2 side than the middle portion of the cutting jig 8. That is, in at least a portion of the region including the middle point of the removal pad 10 in the rotation direction A, the surface 10a of the removal pad 10 protrudes further toward the support roll 2 side than the third cutting blade 14c and the fourth cutting blade 14d. As an example, the surface 10a of the removal pad 10 has a curved surface shape with a greater curvature than the peripheral surface 4a of the forming roll 4.

[0030] The forming unit 7 gradually approaches the peripheral surface 2a of the support roller 2 as the forming roller 4 rotates. And, first, the first cutting edge 14a is pressed against the composite sheet 6. The cutting jig 8 protrudes further than the removal pad 10 at the front end portion in the rotation direction A, so that the first cutting edge 14a can be more reliably brought into contact with the composite sheet 6. Since the first cutting edge 14a cuts the composite sheet 6, the starting point of the cut portion 6a is formed.

[0031] When the forming roller 4 rotates further, the surface 10a of the removal pad 10 abuts against the composite sheet 6, and the surface 10a is pressed against the composite sheet 6 by the force of the elastic body 12. In addition, the removal pad 10 is subjected to the reaction force of the composite sheet 6 and sinks into the frame of the cutting fixture 8. As a result, the third cutting edge 14c and the fourth cutting edge 14d are pressed against the composite sheet 6. The third cutting edge 14c and the fourth cutting edge 14d cut the composite sheet 6, and the cut portion 6a extends backward in the rotation direction A.

[0032] The cut portion 6a is gradually transferred to the surface 10a of the removal pad 10 from the front end side in the rotation direction A. By making the surface roughness of the surface 10a of the removal pad 10 larger than the surface roughness of the peripheral surface 2a of the support roller 2, it is possible to facilitate the transfer of the cut portion 6a to the removal pad 10. In addition, even if the surface 10a is pressed against the cut portion 6a by the elastic body 12, it is possible to facilitate the transfer of the cut portion 6a to the removal pad 10.

[0033] Then, when the forming roller 4 rotates further, the second cutting edge 14b is pressed against the composite sheet 6. The cutting jig 8 protrudes further than the removal pad 10 at the rear end portion in the rotation direction A, so that the second cutting edge 14b can be more reliably brought into contact with the composite sheet 6. Since the second cutting edge 14b cuts the composite sheet 6, the end point of the cut portion 6a is formed. As a result, the cut portion 6a becomes rectangular.

[0034] When the forming roller 4 rotates further, the removal pad 10 gradually leaves the peripheral surface 2a of the support roller 2. As a result, the cut portion 6a transferred to the removal pad 10 is pulled away from the composite sheet 6. When the removal pad 10 gradually leaves the peripheral surface 2a, the removal pad 10 is pulled toward the support roller 2 side via the cut portion 6a. However, the removal pad 10 is pulled toward the forming roller 4 side with a force stronger than the force pulled toward the support roller 2 side by the elastic body 12. As a result, the cut portion 6a can be pulled away from the composite sheet 6 more reliably.

[0035] The cutting jig 8 is fixed to the forming roller 4. Therefore, compared with the structure in which the cutting jig 8 is displaced in the radial direction of the forming roller 4, the structure of the forming unit 7 can be simplified. In addition, the maintenance of the forming roller 4 becomes easy. In addition, in the present embodiment, the window portion 6b is formed before the composite sheet 6 is stacked on the collector plate. Thus, the collector plate can be prevented from being cut by the cutting jig 8. Therefore, the quality of the power storage device can be improved.

[0036] The cut portion 6a cut off from the composite sheet 6 is peeled off and removed from the removal pad 10 at a predetermined position by a peeling mechanism (not shown). The forming unit 7 from which the cut portion 6a has been removed advances again to a position relative to the support roller 2 due to the rotation of the forming roller 4, and is provided for the cutting process of the composite sheet 6. Thus, a plurality of window portions 6b arranged at predetermined intervals along the conveying direction are formed in the composite sheet 6. As an example, each window portion 6b is arranged at the center of the width direction (direction orthogonal to the conveying direction) of the composite sheet 6.

[0037] Figure 1 The forming roller 4 shown in FIG. 4 has only one forming unit 7, but the number of the forming units 7 is not limited to one. Alternatively, the forming roller 4 may have a plurality of forming units 7 according to the intervals between the windows 6b formed in the composite sheet 6. In addition, the intervals between the windows 6b may be adjusted according to the intervals between the plurality of forming units 7 or according to the radius of the forming roller 4.

[0038] Figure 4 (A) is a top view of the electrode sheet 20 . Figure 4 (B) is along Figure 4 A cross-sectional view of the line AA of (A). The composite sheet 6 having the window portion 6b is transported to the downstream side by the support roller 2. Furthermore, the composite sheet 6 is stacked on the surface of the collector plate 18, and the electrode sheet 20 is obtained. The electrode sheet 20 is a continuum of a plurality of dry electrode sheets. As an example, the composite sheet 6 is stacked on both sides of the collector plate 18. In the case of a general lithium-ion secondary battery, the collector plate 18 is composed of aluminum foil or the like when it is a positive electrode, and is composed of copper foil or the like when it is a negative electrode. The collector plate 18 is exposed at the window portion 6b.

[0039] The entire circumference of each window portion 6b is surrounded by a dry electrode mixture. Therefore, the collector plate 18 is exposed in a dotted manner. In the previous electrode sheet, the exposed portion of the collector plate 18, that is, the uncoated portion of the electrode mixture, extends along the entire width direction of the electrode sheet. In contrast, in the electrode sheet 20 of the present embodiment, the exposed portion of the collector plate 18 extends only along a portion of the width direction of the electrode sheet 20. Thus, the amount of dry electrode mixture in each electrode sheet can be increased. Therefore, it is possible to seek a higher capacity of the storage device. In addition, the exposed portion of the collector plate 18 can be made smaller, so the safety of the storage device can also be improved.

[0040] Figure 5 (A) is a plan view of the electrode sheet 20 to which the current collecting lead 22 is joined. Figure 5 (B) is an enlarged cross-sectional view of the window portion 6b. Figure 5 The cross section shown in (B) is a cross section of the electrode sheet 20 that is perpendicular to the extending direction of the collector plate 18 and the composite sheet 6, in other words, a cross section that is parallel to the normal line of the collector plate 18 and the composite sheet 6. Figure 5 In (B), one compound tablet 6 is omitted from illustration.

[0041] As an example, the electrode sheet 20 is Figure 5 As shown in (A), it is cut in the center in the width direction and divided into two. As a result, each window portion 6b is also divided into two. As a result, each rectangular window portion 6b will be in a state where three of them are surrounded by a dry electrode mixture. In addition, the collector lead 22 (collector ear) is joined to the portion of the collector plate 18 exposed from each divided window portion 6b by welding or the like. The exposed portion of the collector plate 18 to which the collector lead 22 is joined is covered by an insulating protective tape (not shown). Then, the electrode sheet 20 is cut between adjacent collector leads 22 and is singulated into a plurality of dry electrode sheets.

[0042] like Figure 5As shown in (B), in the cross section of the collector plate 18 and the mixture sheet 6 perpendicular to the extension direction, the angle θ1 formed by the side wall 6c (the side surface connecting the two main surfaces) of the mixture sheet 6 in the window portion 6b and the surface 18a of the collector plate 18 is greater than 75° and less than 105°. Preferably, the angle θ1 is 75° to 105° throughout the entire circumference of the window portion 6b. In addition, it is preferred that the angle θ1 is greater than 85° and less than 95°. By setting the angle θ1 formed by the side wall 6c and the surface 18a of the collector plate 18 to a substantially right angle of greater than 75° and less than 105°, it is possible to easily suppress poor bonding of the collector plate 18 and the collector lead 22 caused by interference from the dry electrode mixture. In addition, it is possible to easily suppress contact between the collector lead 22 and the dry electrode mixture. As a result, it is possible to seek to improve the quality of the power storage device. In particular, when the uncoated portion of the dry electrode mixture is in the form of dots, it becomes difficult to join the current collecting lead 22. Therefore, the quality improvement effect of the power storage device caused by setting the angle θ1 to be substantially a right angle is more likely to be exerted.

[0043] In addition, when the wet electrode mixture is used to form the mixture sheet, the boundary between the uncoated portion and the coated portion of the wet electrode mixture may be deformed due to the sagging of the wet electrode mixture. In addition, when the wet electrode mixture is intermittently applied to form the uncoated portion, the edge of the coated portion may become jagged. In this case, when the electrode sheet repeatedly expands and contracts due to the charging and discharging of the storage device, the separator may be damaged. Damage to the separator may cause an internal short circuit.

[0044] In contrast, in the present embodiment, the window portion 6b is formed by cutting the mixture sheet 6 composed of the dry electrode mixture with a cutting fixture 8. Therefore, the boundary between the uncoated portion and the coated portion of the dry electrode mixture will be difficult to deform, and the above-mentioned angle θ1 can be maintained almost at a right angle. In addition, the edge of the coated portion will become a straight line according to the shape of the cutting blade. Therefore, damage to the separator can also be suppressed. In addition, since the window portion 6b is formed by cutting using the cutting fixture 8, it is possible to suppress the edge of the coated portion from bulging in the thickness direction of the mixture sheet 6. Thus, it is also possible to suppress the following situation: when the electrode sheet repeatedly expands and contracts due to the charging and discharging of the storage device, the separator is damaged.

[0045] The above is a detailed description of the embodiments of the present disclosure. The aforementioned embodiments do not merely represent specific examples when implementing the present disclosure. The contents of the embodiments do not limit the technical scope of the present disclosure, and various design changes such as changes, additions, and deletions of constituent elements can be made without departing from the scope of the disclosed ideas specified in the claims. The new embodiment with design changes has the effects of the combined embodiments and the deformations. In the aforementioned embodiments, the contents that can be subjected to such design changes are emphasized by adding "in this embodiment", "in this embodiment", etc., but design changes are allowed even in the absence of such records. Any combination of constituent elements included in each embodiment is also valid as a scheme of the present disclosure. The shadows attached to the cross-sections of the accompanying drawings do not limit the material of the objects with shadows.

[0046] The embodiment may be determined by the items described below.

[0047] [Item 1]

[0048] A device (1) for forming a composite tablet (6), comprising:

[0049] A support roller (2) supports a mixture sheet (6) composed of a dry electrode mixture with its peripheral surface (2a), and

[0050] A forming roller (4) having a frame-shaped cutting fixture (8) and a removal pad (10) arranged in the frame of the cutting fixture (8) on its circumferential surface (4a), the circumferential surface (4a) being opposed to the circumferential surface (2a) of the support roller (2) at a predetermined interval and rotating together with the rotation of the support roller (2);

[0051] The forming roller (4) presses the cutting jig (8) against the composite sheet (6), partially cutting the composite sheet (6), causing the cut portion (6a) to adhere to the surface (10a) of the removal pad (10), and then pulling it away from the composite sheet (6).

[0052] [Item 2]

[0053] The forming device (1) according to item 1, wherein:

[0054] The surface (10a) of the removal pad (10) has a greater surface roughness than the peripheral surface (2a) of the support roller (2).

[0055] [Item 3]

[0056] The molding device (1) according to item 1 or 2, wherein:

[0057] The forming roller (4) has an elastic body (12) that supports the removal pad (10).

[0058] [Item 4]

[0059] The molding device (1) according to any one of items 1 to 3, wherein:

[0060] The front end of the cutting jig (8) in the rotation direction (A) of the forming roller (4) protrudes toward the supporting roller (2) more than the front end of the removal pad (10);

[0061] The rear end of the cutting jig (8) in the rotation direction (A) protrudes toward the support roller (2) more than the rear end of the removal pad (10);

[0062] The middle portion of the removal pad (10) in the rotation direction (A) protrudes toward the support roller (2) more than the middle portion of the cutting jig (8).

[0063] [Item 5]

[0064] A method for forming a composite tablet (6), comprising:

[0065] A mixture sheet (6) composed of a dry electrode mixture is supported by a peripheral surface (2a) of a support roller (2);

[0066] A frame-shaped cutting jig (8) and a removal pad (10) arranged in the frame of the cutting jig (8) are provided on a peripheral surface (4a), and the peripheral surface (4a) causes a forming roller (4) facing the peripheral surface (2a) of a support roller (2) at a predetermined interval to rotate together with the support roller (2);

[0067] The cutting jig (8) is pressed against the compound sheet (6) to partially cut the compound sheet (6), and the cut portion (6a) is made to adhere to the surface (10a) of the removal pad (10) and is pulled away from the compound sheet (6).

[0068] [Item 6]

[0069] An electrode sheet (20) comprises a current collector plate (18) and a mixture sheet (6), wherein the mixture sheet (6) is composed of a dry electrode mixture and is laminated on the surface of the current collector plate (18);

[0070] In the electrode sheet (20),

[0071] The mixture sheet (6) has a window portion (6b) entirely surrounded by a dry electrode mixture, and the current collector (18) is exposed at the window portion (6b);

[0072] In a cross section perpendicular to the extension direction of the collector plate (18) and the composite sheet (6), an angle (θ1) formed by a side wall (6c) of the composite sheet (6) in the window portion (6b) and a surface (18a) of the collector plate (18) is greater than 75° and less than 105°.

[0073] [Industrial Applicability]

[0074] The present disclosure can be utilized for an electrode sheet.

[0075] [Explanation of Reference Numerals]

[0076] 1 forming device, 2 supporting roller, 4 forming roller, 6 compound sheet, 6a cutting portion, 6b window portion, 6c side wall, 8 cutting jig, 10 removal pad, 12 elastic body, 18 collector plate, 20 electrode sheet.

Claims

1. An electrode sheet comprising a current collector plate and a mixture sheet, wherein the mixture sheet is composed of a dry electrode mixture and is laminated on the surface of the current collector plate; In the electrode sheet, The mixture sheet has a window portion entirely surrounded by the dry electrode mixture, and the current collector is exposed at the window portion; In a cross section perpendicular to the extending direction of the current collector plate and the mixture sheet, an angle formed by a side wall of the mixture sheet in the window portion and a surface of the current collector plate is not less than 75° and not more than 105°.

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