JP2021057174A - Electrode assembly - Google Patents

Abstract

To provide an electrode assembly capable of suppressing damage of an active material layer.SOLUTION: In an electrode assembly 12, a cathode electrode 20 is wound in such a manner that a first face 22a in which a first cathode active material layer 24 is disposed intermittently becomes an inner peripheral surface and a second face 22b in which a second cathode active material layer 25 is disposed intermittently becomes an outer peripheral surface. The electrode assembly 12 comprises: a central lamination part 12a in which a cathode coated portion 28 is laminated flatly; and a first end side lamination part 12b and a second end side lamination part 12c which are positioned at both sides of the central lamination part 12a and in which a cathode exposure portion 29 is laminated in a bent state. The second cathode active material layer 25 includes: a cathode main part 26 which is overlapped with the first cathode active material layer 24 in a view in a thickness direction of a cathode metal foil 21; and a cathode protrusion part 27 which protrudes outside from the first cathode active material layer 24 and of which the thickness is reduced from the cathode main part 26 to the cathode exposure part 29. An active material density in the cathode protrusion part 27 is lower than an active material density in the cathode main part 26.SELECTED DRAWING: Figure 2

Description

The present invention relates to an electrode assembly in which an electrode having a long sheet-shaped current collector and an active material layer intermittently arranged on both sides of the current collector is wound.

Patent Document 1 describes a secondary battery including an electrode assembly in which a long sheet-shaped positive electrode and a long sheet-shaped negative electrode are wound via a separator, and a case for accommodating the electrode assembly. It is disclosed. The positive electrode and the negative electrode are a long sheet-shaped current collector, a first active material layer intermittently arranged on the first surface of the current collector, and a side opposite to the first surface of the current collector. It has a second active material layer intermittently arranged on the second surface of the above. The positive electrode and the negative electrode are wound so that the first surface is the inner peripheral surface and the second surface is the outer peripheral surface.

The electrode assembly is a flat wound body having a flat portion and a pair of side portions located on both sides of the flat portion. In the flat portion, the coated portion in which the first active material layer and the second active material layer are arranged in the current collector is laminated flat. On each side, the exposed portion, which is the exposed portion of the current collector, is laminated in a curved state.

JP-A-2007-26786

In the electrode assembly of Patent Document 1, in order to improve the capacity of the battery, it is effective to extend the dimensions of the flat portion to both sides. It will be large. Therefore, in order to improve the capacity of the battery while avoiding the increase in size of the case, the dimensions of the flat portion are extended to both sides, and the dimensions of the individual exposed portions are shortened in the longitudinal direction of the current collector. Therefore, it is necessary to shorten the side part.

By the way, when the active material layer expands due to the charging and discharging of the secondary battery, the size of the flat portion in the stacking direction of the coated portion increases. Then, the exposed portion is pulled on both sides in the stacking direction and deforms so as to approach a linear shape from a curved shape. At this time, if the size of the exposed portion is short, the exposed portion bends and extends from both ends of the coated portion at an angle close to a right angle. In this case, the first active material layer may be crushed by the current collector at both ends of the coated portion, and a part of the first active material layer may be damaged.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an electrode assembly capable of suppressing damage to an active material layer.

The electrode assembly for solving the above problems includes a long sheet-shaped current collector, a first active material layer intermittently arranged on the first surface of the current collector, and the current collector. The positive electrode and the negative electrode having the second active material layer intermittently arranged on the second surface opposite to the first surface of the above, the first surface serves as an inner peripheral surface, and the second surface becomes the inner peripheral surface. Is wound through a separator so as to be an outer peripheral surface, and a flat coating portion in which the first active material layer and the second active material layer are arranged in the current collector are laminated flatly. An electrode assembly having a portion and a pair of side portions that are located on both sides of the flat portion and are laminated in a state in which the exposed portion, which is an exposed portion of the current collector, is curved. When viewed from the thickness direction of the current collector, the second active material layer protrudes outward from the main portion overlapping the first active material layer and the first active material layer, and The gist is that it has a protruding portion that becomes thinner from the main portion toward the exposed portion, and the active material density in the protruding portion is lower than the active material density in the main portion.

According to this, since the density of the active material in the protruding portion is lower than the density of the active material in the main portion, the protruding portion can be deformed so as to be curved. When the main part expands and the size of the flat part in the stacking direction of the coated part increases, the exposed part is provided with a protruding part, so that the exposed part is at an angle close to a right angle from both ends of the coated part. Bending is suppressed. Further, since the protruding portion is deformed according to the expansion of the main portion, the exposed portion is less likely to be pulled on both sides in the laminating direction of the coated portion. As a result, it is suppressed that the first active material layer is crushed by the current collector at both ends of the coated portion.

When the first active material layer is also provided on the opposite side of the protruding portion when viewed from the thickness direction of the current collector, a part of the first active material layer also constitutes a side portion. .. In this case, when the first active material layer expands, a compressive force acts on a portion of the first active material layer that constitutes a side portion, so that the first active material layer may fall off. On the other hand, the first active material layer is not provided on the opposite side of the protruding portion, that is, the first active material layer does not form a side portion, so that the first active material layer is expanded. Dropout is suppressed. Therefore, damage to the active material layer can be suppressed.

Further, with respect to the electrode assembly, it is preferable that the dimension of the protruding portion is longer than that of the protruding portion located on the inner peripheral side of the electrode assembly.
The degree of curvature of the exposed portion is tighter as the exposed portion is located on the inner peripheral side in the electrode assembly, and is gentler as the exposed portion is located on the outer peripheral side in the electrode assembly. Therefore, the force with which the current collector tries to crush the first active material layer at both ends of the coated portion is larger toward the inner peripheral side and smaller toward the outer peripheral side in the electrode assembly. For this reason, by increasing the size of the protruding portion toward the protruding portion located on the inner peripheral side, it is possible to further prevent the exposed portion from bending at an angle close to a right angle from both ends of the coated portion. Therefore, damage to the active material layer can be further suppressed.

Further, regarding the electrode assembly, it is preferable that only the second active material layer located on the innermost circumference of the electrode assembly has the protruding portion.
The degree of curvature of the exposed portion is tighter as the exposed portion is located on the inner peripheral side in the electrode assembly, and is gentler as the exposed portion is located on the outer peripheral side in the electrode assembly. Therefore, the force with which the current collector tries to crush the first active material layer at both ends of the coated portion is larger toward the inner peripheral side and smaller toward the outer peripheral side in the electrode assembly. Therefore, by providing the protruding portion only on the second active material layer located on the innermost circumference, the force for crushing the first active material layer is maximized, and the first one located on the innermost circumference. Damage to the active material layer can be further suppressed. In addition, the amount of the active material layer material used can be reduced as compared with the case where the protruding portion is provided in all the second active material layers. Therefore, the cost required for the electrode can be suppressed.

Further, with respect to the electrode assembly, both ends of the second active material layer of the positive electrode are located inside the both ends of the second active material layer of the negative electrode, and the second end of the negative electrode is provided. The active material layer of No. 1 preferably has the protruding portion.

In the coated portion of the negative electrode, the portion located outside the coated portion of the positive electrode tends to be curved toward the center in the stacking direction of the coated portion, so that the second active material layer is pulled. Although stress acts, cracking of the second active material layer can be suppressed by deforming the protruding portion having a lower active material density than the main portion.

According to the present invention, damage to the active material layer can be suppressed.

An exploded perspective view of the secondary battery. The plan view of the electrode assembly of 1st Embodiment. (A) is a plan view of the positive electrode, (b) is a sectional view of the positive electrode, and (c) is an enlarged sectional view of the positive electrode. (A) is a plan view of the negative electrode, (b) is a sectional view of the negative electrode, and (c) is an enlarged sectional view of the negative electrode. The cross-sectional view which shows the manufacturing method of the positive electrode. The cross-sectional view which shows the manufacturing method of the positive electrode. The plan view of the electrode assembly of 2nd Embodiment. (A) is a cross-sectional view of the electrode of the third embodiment, and (b) and (c) are enlarged cross-sectional views of the electrode of the third embodiment. The plan view of the electrode assembly of 3rd Embodiment.

(First Embodiment)
Hereinafter, the first embodiment in which the electrode assembly is embodied will be described with reference to FIGS. 1 to 6.
As shown in FIG. 1, the secondary battery 10 as a power storage device includes a rectangular parallelepiped case 11, an electrode assembly 12 housed in the case 11, and an electrolytic solution (not shown) housed in the case 11. The case 11 has a bottomed tubular case body 13 and a plate-shaped lid 14 that closes the opening 13a of the case body 13. The case body 13 and the lid 14 are made of metal such as aluminum. The case body 13 was erected from a rectangular bottom wall 13b, a pair of long side walls 13c erected from a pair of long side edges of the bottom wall 13b, and a pair of short side edges of the bottom wall 13b. It has a pair of short side walls 13d. The lid 14 has a rectangular shape. Therefore, the secondary battery 10 of the present embodiment is a square battery having a square appearance. Further, the secondary battery 10 of the present embodiment is a lithium ion secondary battery.

As shown in FIG. 2, the electrode assembly 12 includes a positive electrode 20 as a long sheet-shaped positive electrode, a negative electrode 30 as a long sheet-shaped negative electrode, and two long sheet-shaped negative electrodes. It is formed by winding the separator 40 of the above. The electrode assembly 12 is a flat roll having a flat portion formed by laminating a positive electrode 20, a negative electrode 30, and a separator 40 in a flat manner, and a pair of side portions located on both sides of the flat portion. It is an electrode.

3 (a), 3 (b), and 3 (c) show the positive electrode 20 before winding. As shown in FIG. 3A, the positive electrode electrode 20 has a positive electrode metal foil 21 as a long sheet-shaped current collector. The positive electrode metal foil 21 of the present embodiment is an aluminum foil. The positive electrode metal leaf 21 has a rectangular positive electrode main body 22 and a plurality of positive electrode tabs 23 protruding from one edge along the longitudinal direction of the positive electrode main body 22. The longitudinal direction of the positive electrode main body 22 corresponds to the longitudinal direction of the positive electrode 20, and the lateral direction of the positive electrode main body 22 corresponds to the lateral direction of the positive electrode 20.

As shown in FIG. 3B, the positive electrode 20 includes a plurality of first positive electrode active material layers 24 as first active material layers existing on the first surface 22a of the positive electrode main body 22, and the positive electrode main body 22. It has a plurality of second positive electrode active material layers 25 as a second active material layer existing on the second surface 22b, which is a surface opposite to the first surface 22a. The first positive electrode active material layer 24 is intermittently arranged with respect to the positive electrode main body 22. The plurality of first positive electrode active material layers 24 are arranged at intervals in the longitudinal direction of the positive electrode main body 22. Further, the second positive electrode active material layer 25 is intermittently arranged with respect to the positive electrode main body 22. The plurality of second positive electrode active material layers 25 are arranged at intervals in the longitudinal direction of the positive electrode main body 22.

The first positive electrode active material layer 24 and the second positive electrode active material layer 25 are each rectangular. The longitudinal direction of the first positive electrode active material layer 24 and the second positive electrode active material layer 25 coincides with the longitudinal direction of the positive electrode main body 22, and the lateral direction of the first positive electrode active material layer 24 and the second positive electrode active material layer 25. Is the same as the lateral direction of the positive electrode main body 22. The longitudinal dimension of each second positive electrode active material layer 25 is longer than the longitudinal dimension of each first positive electrode active material layer 24, and the lateral dimension of each second positive electrode active material layer 25 is each second. 1 The dimensions of the positive electrode active material layer 24 in the lateral direction are substantially the same.

As shown in FIG. 3C, the thickness of the first positive electrode active material layer 24 is substantially uniform in the entire longitudinal direction of the first positive electrode active material layer 24. In addition, "the thickness of the first positive electrode active material layer 24 is substantially uniform" includes a state in which the thickness of the first positive electrode active material layer 24 varies within an allowable range. The permissible range is a range that is permissible in the design of the positive electrode 20 and is a so-called manufacturing tolerance. The longitudinal dimensions of the first positive electrode active material layer 24 are substantially the same for all the first positive electrode active material layers 24.

The first positive electrode active material layer 24 has a first main surface 24a facing the first surface 22a of the positive electrode main body 22, and a second main surface 24b which is a surface opposite to the first main surface 24a. Further, the first positive electrode active material layer 24 has connecting surfaces 24c connected to the second main surface 24b and the first surface 291 of the positive electrode exposed portion 29, which will be described later, at both ends of the first positive electrode active material layer 24 in the longitudinal direction. .. The connecting surface 24c constitutes the longitudinal end of the first positive electrode active material layer 24.

The second positive electrode active material layer 25 has a rectangular positive electrode main portion 26 in which the thickness of the second positive electrode active material layer 25 is substantially uniform in the longitudinal direction of the second positive electrode active material layer 25. In addition, "the thickness of the second positive electrode active material layer 25 is substantially uniform" includes a state in which the thickness of the second positive electrode active material layer 25 varies within an allowable range. The permissible range is a range that is permissible in the design of the positive electrode 20 and is a so-called manufacturing tolerance.

In the present embodiment, the positive electrode main portion 26 is composed of a portion of the second positive electrode active material layer 25 that overlaps with the first positive electrode active material layer 24 when the positive electrode electrode 20 is viewed from the thickness direction of the positive electrode main body portion 22. Has been done. That is, the positive electrode main portion 26 overlaps with the second main surface 24b of the first positive electrode active material layer 24 when the positive electrode electrode 20 is viewed from the thickness direction of the positive electrode main body portion 22 of the second positive electrode active material layer 25. It is composed of parts. When the connection surface 24c of the first positive electrode active material layer 24 is extended in the thickness direction of the positive electrode main body 22 in a state where the positive electrode electrode 20 is not wound and is stretched flat, the second positive electrode active material layer 25 Let the virtual surface formed in the above be the virtual end surface S. The virtual end face S constitutes end faces located at both ends of the positive electrode main portion 26 in the longitudinal direction.

Further, the second positive electrode active material layer 25 has a positive electrode protruding portion 27 that protrudes from the virtual end face S in the longitudinal direction of the positive electrode main body 22 and gradually becomes thinner as the distance from the virtual end face S increases. In other words, the positive electrode protruding portion 27 protrudes from the longitudinal end of the first positive electrode active material layer 24 when viewed from the thickness direction of the positive electrode main body portion 22, and the positive electrode is exposed from the end of the first positive electrode active material layer 24. This is a portion where the thickness gradually decreases toward the portion 29. The positive electrode protruding portion 27 exists on both outer sides of the virtual end surface S of the positive electrode main portion 26 in the longitudinal direction of the positive electrode main body portion 22. However, of the pair of virtual end faces S of the positive electrode main portion 26 closest to the first end 20a of the positive electrode 20, on the outside of the virtual end face S closer to the first end 20a and on the second end 20b of the positive electrode 20. Of the pair of virtual end faces S of the closest positive electrode main portion 26, the positive electrode protruding portion 27 does not exist outside the virtual end face S closer to the second end 20b. Of the pair of edges of the positive electrode protruding portion 27 along the lateral direction of the second positive electrode active material layer 25, the edge portion on the side away from the positive electrode main portion 26 is the longitudinal end of the second positive electrode active material layer 25. Consists of. As will be described later, in the pair of side portions of the electrode assembly 12, the positive electrode protruding portion 27 has an arc shape.

The dimensions of the positive electrode main portion 26 in the longitudinal direction of the second positive electrode active material layer 25 are substantially the same for all the second positive electrode active material layers 25. Further, in the present embodiment, the dimensions of the positive electrode protruding portion 27 in the longitudinal direction of the second positive electrode active material layer 25 are substantially the same for all the second positive electrode active material layers 25. Therefore, the dimensions of the second positive electrode active material layer 25 in the longitudinal direction are substantially the same for all the second positive electrode active material layers 25. Further, the density of the active material in the positive electrode protruding portion 27 is lower than the density of the active material in the positive electrode main portion 26. Therefore, the hardness of the positive electrode protruding portion 27 is lower than the hardness of the positive electrode main portion 26.

The second positive electrode active material layer 25 has a first main surface 25a facing the second surface 22b of the positive electrode main body 22, and a second main surface 25b which is a surface opposite to the first main surface 25a. The first main surface 25a is composed of a surface of the positive electrode main portion 26 and the positive electrode protruding portion 27 facing the second surface 22b of the positive electrode main body portion 22. The second main surface 25b is composed of a surface of the positive electrode main portion 26 opposite to the surface of the positive electrode main body 22 facing the second surface 22b. Further, the second positive electrode active material layer 25 has connecting surfaces 25c connected to the first main surface 25a and the second surface 292 of the positive electrode exposed portion 29 at both ends in the longitudinal direction of the second positive electrode active material layer 25. As will be described later, in the pair of side portions of the electrode assembly 12, the connecting surface 25c is a curved surface.

The angle formed by the first surface 22a of the positive electrode main body 22 and the connecting surface 24c of the first positive electrode active material layer 24 is defined as α1. The angle α1 is substantially the same for all the first positive electrode active material layers 24. In this embodiment, the angle α1 is about 90 degrees. Further, the angle formed by the second surface 22b of the positive electrode main body 22 and the connecting surface 25c of the second positive electrode active material layer 25 is defined as α2. The angle α2 is substantially the same for all the second positive electrode active material layers 25. The angle α2 is smaller than the angle α1.

As shown in FIGS. 3A and 3B, the positive electrode electrode 20 has a positive electrode coating portion 28 as a coating portion and a positive electrode exposed portion 29 as an exposed portion. The positive electrode coating portion 28 is sandwiched between the first positive electrode active material layer 24, the positive electrode main portion 26 of the second positive electrode active material layer 25, and the first positive electrode active material layer 24 and the positive electrode main portion 26 in the positive electrode main body portion 22. It consists of the part that has been removed. The positive electrode exposed portion 29 is a portion where the positive electrode main body portion 22 is exposed between the first positive electrode active material layers 24. In other words, the positive electrode exposed portion 29 is a portion where at least the first surface 22a of the positive electrode main body portion 22 is exposed. In the positive electrode exposed portion 29, the first surface 22a of the positive electrode main body 22 is exposed, and both the portion where the positive electrode protruding portion 27 is arranged on the second surface 22b and both the first surface 22a and the second surface 22b are exposed. It is composed of parts. The first surface 291 of the positive electrode exposed portion 29 corresponds to the portion of the first surface 22a of the positive electrode main body 22 that constitutes the positive electrode exposed portion 29, and the second surface 292 of the positive electrode exposed portion 29 is the positive electrode main body 22. Corresponds to the portion of the second surface 22b of the above, which constitutes the positive electrode exposed portion 29. In the present embodiment, the positive electrode electrode 20 has six positive electrode coating portions 28 and five positive electrode exposed portions 29. The positive electrode coating portion 28 and the positive electrode exposed portion 29 are alternately present in the longitudinal direction of the positive electrode electrode 20.

In the present embodiment, the dimensions of the positive electrode coated portion 28 in the longitudinal direction of the positive electrode electrode 20 are substantially the same for all the positive electrode coated portions 28. On the other hand, the dimensions of the positive electrode exposed portion 29 in the longitudinal direction of the positive electrode electrode 20 are different for each positive electrode exposed portion 29. Specifically, the dimensions of each positive electrode exposed portion 29 are as small as the positive electrode exposed portion 29 near the first end 20a in the longitudinal direction of the positive electrode electrode 20, and as close as the positive electrode exposed portion 29 near the second end 20b in the longitudinal direction of the positive electrode 20. It's getting bigger. That is, the size of the positive electrode exposed portion 29 gradually increases from the positive electrode exposed portion 29 close to the first end 20a of the positive electrode electrode 20 to the positive electrode exposed portion 29 close to the second end 20b.

Each positive electrode tab 23 is a portion where the first positive electrode active material layer 24 and the second positive electrode active material layer 25 are not present and the positive electrode metal foil 21 is exposed. The shape of the positive electrode tab 23 is the same for all the positive electrode tabs 23, and is rectangular in this embodiment. Each positive electrode tab 23 protrudes from one edge of a portion of the positive electrode main body 22 that constitutes the positive electrode coating portion 28. That is, each positive electrode tab 23 is arranged at a position corresponding to each positive electrode coating portion 28 in the longitudinal direction of the positive electrode main body portion 22. Further, each positive electrode tab 23 includes a positive electrode tab 23 located near one end in the longitudinal direction of the first positive electrode active material layer 24 and the second positive electrode active material layer 25, and the first positive electrode active material layer 24 and the second positive electrode active material. The positive electrode tabs 23 located near the other end in the longitudinal direction of the layer 25 are arranged so as to be alternately present in the longitudinal direction of the positive electrode main body 22.

4 (a), 4 (b), and 4 (c) show the negative electrode 30 before winding. As shown in FIG. 4A, the negative electrode electrode 30 has a negative electrode metal foil 31 as a long sheet-shaped current collector. The negative electrode metal foil 31 of the present embodiment is a copper foil. The negative electrode metal foil 31 has a rectangular negative electrode main body 32 and a plurality of negative electrode tabs 33 protruding from one edge along the longitudinal direction of the negative electrode main body 32. The longitudinal direction of the negative electrode body 32 is the longitudinal direction of the negative electrode 30, and the lateral direction of the negative electrode body 32 is the lateral direction of the negative electrode 30. In the present embodiment, the longitudinal dimension of the negative electrode body 32 is longer than the longitudinal dimension of the positive electrode body 22, and the lateral dimension of the negative electrode body 32 is the lateral dimension of the positive electrode body 22. Longer than the dimensions.

As shown in FIG. 4B, the negative electrode 30 includes a plurality of first negative electrode active material layers 34 as the first active material layer existing on the first surface 32a of the negative electrode main body 32, and the negative electrode main body 32. It has a plurality of second negative electrode active material layers 35 as a second active material layer existing on the second surface 32b, which is a surface opposite to the first surface 32a. The first negative electrode active material layer 34 is intermittently arranged with respect to the negative electrode main body 32. The plurality of first negative electrode active material layers 34 are arranged at intervals in the longitudinal direction of the negative electrode main body 32. The second negative electrode active material layer 35 is intermittently arranged with respect to the negative electrode main body 32. The plurality of second negative electrode active material layers 35 are arranged at intervals in the longitudinal direction of the negative electrode main body 32.

The first negative electrode active material layer 34 and the second negative electrode active material layer 35 are each rectangular. The longitudinal direction of the first negative electrode active material layer 34 and the second negative electrode active material layer 35 coincides with the longitudinal direction of the negative electrode main body 32, and the lateral direction of the first negative electrode active material layer 34 and the second negative electrode active material layer 35. Is the same as the lateral direction of the negative electrode main body 32. The longitudinal dimension of each second negative electrode active material layer 35 is longer than the longitudinal dimension of each first negative electrode active material layer 34, and the lateral dimension of each second negative electrode active material layer 35 is each second. 1 The dimensions of the negative electrode active material layer 34 in the lateral direction are substantially the same. The dimensions of the first negative electrode active material layer 34 in the longitudinal direction and the lateral direction are substantially the same for all the first negative electrode active material layers 34, respectively. Further, as shown in FIG. 2, in the present embodiment, the longitudinal dimension of the first negative electrode active material layer 34 is longer than the longitudinal dimension of the first positive electrode active material layer 24, and the second negative electrode active material layer The longitudinal dimension of 35 is longer than the longitudinal dimension of the second positive electrode active material layer 25. The lateral dimension of the first negative electrode active material layer 34 is longer than the lateral dimension of the first positive electrode active material layer 24, and the lateral dimension of the second negative electrode active material layer 35 is the second positive electrode. It is longer than the lateral dimension of the active material layer 25.

As shown in FIG. 4C, the thickness of the first negative electrode active material layer 34 is substantially uniform in the entire longitudinal direction of the first negative electrode active material layer 34. In addition, "the thickness of the first negative electrode active material layer 34 is substantially uniform" includes a state in which the thickness of the first negative electrode active material layer 34 varies within an allowable range. The permissible range is a range that is permissible in the design of the negative electrode electrode 30, and is a so-called manufacturing tolerance.

The first negative electrode active material layer 34 has a first main surface 34a facing the first surface 32a of the negative electrode main body 32, and a second main surface 34b which is a surface opposite to the first main surface 34a. Further, the first negative electrode active material layer 34 has connecting surfaces 34c connected to the second main surface 34b and the first surface 391 of the negative electrode exposed portion 39 described later at both ends in the longitudinal direction of the first negative electrode active material layer 34. .. The connecting surface 34c constitutes the longitudinal end of the first negative electrode active material layer 34.

The second negative electrode active material layer 35 has a rectangular negative electrode main portion 36 in which the thickness of the second negative electrode active material layer 35 is substantially uniform in the longitudinal direction of the second negative electrode active material layer 35. The "thickness of the second negative electrode active material layer 35 is substantially uniform" includes a state in which the thickness of the second negative electrode active material layer 35 varies within an allowable range. The permissible range is a range that is permissible in the design of the negative electrode electrode 30, and is a so-called manufacturing tolerance.

In the present embodiment, the negative electrode main portion 36 is composed of a portion of the second negative electrode active material layer 35 that overlaps with the first negative electrode active material layer 34 when the negative electrode electrode 30 is viewed from the thickness direction of the negative electrode main body portion 32. Has been done. That is, the negative electrode main portion 36 overlaps with the second main surface 34b of the first negative electrode active material layer 34 when the negative electrode electrode 30 is viewed from the thickness direction of the negative electrode main body portion 32 of the second negative electrode active material layer 35. It is composed of parts. When the connection surface 34c of the first negative electrode active material layer 34 is extended in the thickness direction of the negative electrode main body 32 in a state where the negative electrode electrode 30 is not wound and is stretched flat, the second negative electrode active material layer 35 Let the virtual surface formed in the above be the virtual end surface S. The virtual end face S constitutes end faces located at both ends of the negative electrode main portion 36 in the longitudinal direction.

Further, the second negative electrode active material layer 35 has a protruding portion 37 that protrudes from the virtual end surface S in the longitudinal direction of the negative electrode main body portion 32 and gradually decreases in thickness as the distance from the virtual end surface S increases. In other words, the protruding portion 37 protrudes from the longitudinal end of the first negative electrode active material layer 34 when viewed from the thickness direction of the negative electrode main body 32, and the negative electrode exposed portion from the end of the first negative electrode active material layer 34. This is a portion where the thickness gradually decreases toward 39. The negative electrode protruding portion 37 exists on both outer sides of the virtual end surface S of the negative electrode main portion 36 in the longitudinal direction of the negative electrode main body portion 32. However, of the pair of virtual end faces S of the negative electrode main portion 36 closest to the first end 30a of the negative electrode electrode 30, the outer side of the virtual end face S closer to the first end 30a and the second end 30b of the negative electrode 30 Of the pair of virtual end faces S of the closest negative electrode main portion 36, the negative electrode protruding portion 37 does not exist outside the virtual end face S closer to the second end 30b. Of the pair of edges of the negative electrode protruding portion 37 along the lateral direction of the second negative electrode active material layer 35, the edge portion on the side away from the negative electrode main portion 36 is the longitudinal end of the second negative electrode active material layer 35. Consists of. As will be described later, in the pair of side portions of the electrode assembly 12, the negative electrode protruding portion 37 has an arc shape.

The dimensions of the negative electrode main portion 36 in the longitudinal direction of the second negative electrode active material layer 35 are substantially the same for all the second negative electrode active material layers 35. Further, in the present embodiment, the dimensions of the negative electrode protruding portion 37 in the longitudinal direction of the second negative electrode active material layer 35 are substantially the same in all the second negative electrode active material layers 35. Therefore, the dimensions of the second negative electrode active material layer 35 in the longitudinal direction are substantially the same for all the second negative electrode active material layers 35. Further, the density of the active material in the negative electrode protruding portion 37 is lower than the density of the active material in the negative electrode main portion 36. Therefore, the hardness of the negative electrode protruding portion 37 is lower than the hardness of the negative electrode main portion 36.

The second negative electrode active material layer 35 has a first main surface 35a facing the second surface 32b of the negative electrode main body 32, and a second main surface 35b which is a surface opposite to the first main surface 35a. The first main surface 35a is composed of a negative electrode main portion 36 and a surface of the negative electrode protruding portion 37 facing the second surface 32b of the negative electrode main body portion 32. The second main surface 35b is composed of a surface of the negative electrode main portion 36 opposite to the surface of the negative electrode main body 32 that faces the second surface 32b. Further, the second negative electrode active material layer 35 has connecting surfaces 35c connected to the first main surface 35a and the second surface 392 of the negative electrode exposed portion 39 at both ends in the longitudinal direction of the second negative electrode active material layer 35. As will be described later, in the pair of side portions of the electrode assembly 12, the connecting surface 35c is a curved surface.

Let β1 be the angle formed by the first surface 32a of the negative electrode main body 32 and the connecting surface 34c of the first negative electrode active material layer 34. The angle β1 is substantially the same for all the first negative electrode active material layers 34. In this embodiment, the angle β1 is about 90 degrees. Further, the angle formed by the second surface 32b of the negative electrode main body 32 and the connecting surface 35c of the second negative electrode active material layer 35 is defined as β2. The angle β2 is substantially the same for all the second negative electrode active material layers 35. The angle β2 is smaller than the angle β1.

As shown in FIGS. 4A and 4B, the negative electrode electrode 30 has a negative electrode coating portion 38 as a coating portion and a negative electrode exposed portion 39 as an exposed portion. The negative electrode coating portion 38 is sandwiched between the first negative electrode active material layer 34, the negative electrode main portion 36 of the second negative electrode active material layer 35, and the first negative electrode active material layer 34 and the negative electrode main portion 36 in the negative electrode main body portion 32. It consists of the parts that have been removed. The negative electrode exposed portion 39 is a portion where the negative electrode main body portion 32 is exposed between the first negative electrode active material layers 34. In other words, the negative electrode exposed portion 39 is a portion where at least the first surface 32a of the negative electrode main body portion 32 is exposed. In the negative electrode exposed portion 39, the first surface 32a of the negative electrode main body 32 is exposed, and both the portion where the negative electrode protruding portion 37 is arranged on the second surface 32b and both the first surface 32a and the second surface 32b are exposed. It is composed of parts. The first surface 391 of the negative electrode exposed portion 39 corresponds to the portion of the first surface 32a of the negative electrode main body 32 that constitutes the negative electrode exposed portion 39, and the second surface 392 of the negative electrode exposed portion 39 is the negative electrode main body 32. Corresponds to the portion of the second surface 32b of the above, which constitutes the negative electrode exposed portion 39. In the present embodiment, the negative electrode electrode 30 has seven negative electrode coating portions 38 and six negative electrode exposed portions 39. The negative electrode coating portion 38 and the negative electrode exposed portion 39 are alternately present in the longitudinal direction of the negative electrode electrode 30.

In the present embodiment, the dimensions of the negative electrode coated portion 38 in the longitudinal direction of the negative electrode electrode 30 are substantially the same for all the negative electrode coated portions 38. On the other hand, the dimensions of the negative electrode exposed portion 39 in the longitudinal direction of the negative electrode electrode 30 are different for each negative electrode exposed portion 39. Specifically, the dimensions of each negative electrode exposed portion 39 are as small as the negative electrode exposed portion 39 near the first end 30a in the longitudinal direction of the negative electrode electrode 30, and as close as the negative electrode exposed portion 39 near the second end 30b in the longitudinal direction of the negative electrode 30. It's getting bigger. That is, the size of the negative electrode exposed portion 39 gradually increases from the negative electrode exposed portion 39 near the first end 30a of the negative electrode electrode 30 to the negative electrode exposed portion 39 near the second end 30b.

Each negative electrode tab 33 is a portion where the first negative electrode active material layer 34 and the second negative electrode active material layer 35 do not exist and the negative electrode metal foil 31 is exposed. The shape of the negative electrode tab 33 is the same for all the negative electrode tabs 33, and is rectangular in this embodiment. Each negative electrode tab 33 projects from one edge of a portion of the negative electrode main body 32 that constitutes the negative electrode coating portion 38. That is, each negative electrode tab 33 is arranged at a position corresponding to each negative electrode coating portion 38 in the longitudinal direction of the negative electrode main body portion 32. Further, each negative electrode tab 33 includes a negative electrode tab 33 located near one end in the longitudinal direction of the first negative electrode active material layer 34 and the second negative electrode active material layer 35, and the first negative electrode active material layer 34 and the second negative electrode active material. The negative electrode tabs 33 located near the other end in the longitudinal direction of the layer 35 are arranged so as to be alternately present in the longitudinal direction of the negative electrode main body 32.

As shown in FIG. 2, each separator 40 is interposed between the positive electrode 20 and the negative electrode 30. Each separator 40 is a porous membrane through which lithium ions can pass. The longitudinal dimension of each separator 40 is longer than the longitudinal dimension of the negative electrode main body 32, and the lateral dimension of each separator 40 is substantially the same as the lateral dimension of the negative electrode main body 32.

In the electrode assembly 12, one of the positive electrode 20, the two separators 40, the negative electrode 30, and the other of the two separators 40 are laminated in this order, with the winding shaft L as the axis. It is formed by being wound. The winding direction of the positive electrode 20, the negative electrode 30, and each separator 40 coincides with the longitudinal direction of the positive electrode 20, the negative electrode 30, and each separator 40. The electrode assembly 12 has a layered structure in which a positive electrode 20 and a negative electrode 30 are laminated via a separator 40. In the present embodiment, the electrode assembly 12 is housed in the case 11 so that the direction in which the winding shaft L extends coincides with the direction in which the bottom wall 13b of the case body 13 and the lid 14 face each other.

The positive electrode 20 and the negative electrode 30 are wound so that the first ends 20a and 30a are located on the winding start side and the second ends 20b and 30b are located on the winding end side. In other words, the first ends 20a and 30a of the positive electrode 20 and the negative electrode 30 are located on the innermost circumference of the electrode assembly 12, and the second ends 20b and 30b of the positive electrode 20 and the negative electrode 30 are the electrode assembly. It is located on the outermost circumference of 12. Therefore, among the plurality of positive electrode coating portions 28, the positive electrode coating portion 28 closest to the first end 20a of the positive electrode electrode 20 is the positive electrode coating portion 28 located on the innermost circumference, and the positive electrode 20 is the second. The positive electrode coating portion 28 closest to the two ends 20b is the positive electrode coating portion 28 located on the outermost periphery. Further, among the plurality of negative electrode coating portions 38, the negative electrode coating portion 38 closest to the first end 30a of the negative electrode electrode 30 is the negative electrode coating portion 38 located on the innermost circumference, and the second negative electrode electrode 30 is the second. The negative electrode coating portion 38 closest to the end 30b is the negative electrode coating portion 38 located on the outermost periphery.

Further, the positive electrode electrode 20 is wound so that the first surface 22a of the positive electrode main body 22 is the inner peripheral surface and the second surface 22b of the positive electrode main body 22 is the outer peripheral surface. Therefore, the first positive electrode active material layer 24 is located on the inner peripheral side, and the second positive electrode active material layer 25 is located on the outer peripheral side. The negative electrode electrode 30 is wound so that the first surface 32a of the negative electrode main body 32 is the inner peripheral surface and the second surface 32b of the negative electrode main body 32 is the outer peripheral surface. Therefore, the first negative electrode active material layer 34 is located on the outer peripheral side, and the second negative electrode active material layer 35 is located on the inner peripheral side.

The electrode assembly 12 has a central laminated portion 12a in which a positive electrode coating portion 28 and a negative electrode coating portion 38 are alternately laminated via a separator 40. In the central laminated portion 12a, the positive electrode coated portion 28 and the negative electrode coated portion 38 are respectively laminated flat. Therefore, the central laminated portion 12a constitutes a flat portion of the electrode assembly 12. The direction in which the positive electrode coating portion 28 and the negative electrode coating portion 38 are laminated is defined as the lamination direction.

In the central laminated portion 12a, in the positive electrode coating portion 28 and the negative electrode coating portion 38 adjacent to each other in the lamination direction, the first positive electrode active material layer 24 and the second negative electrode active material layer 35 face each other via the separator 40. Further, in the positive electrode coating portion 28 and the negative electrode coating portion 38 adjacent to each other in the stacking direction, the second positive electrode active material layer 25 and the first negative electrode active material layer 34 face each other via the separator 40.

In the present embodiment, the pair of connecting surfaces 24c of the first positive electrode active material layer 24 is a pair of the first negative electrode active material layer 34 in the longitudinal direction of the first positive electrode active material layer 24 and the first negative electrode active material layer 34. It is located inside the connecting surface 34c. That is, both ends of the first positive electrode active material layer 24 in the longitudinal direction are located inside the both ends of the first negative electrode active material layer 34 in the longitudinal direction. Further, both ends in the longitudinal direction of the second positive electrode active material layer 25 are located inside the both ends in the longitudinal direction of the second negative electrode active material layer 35.

The first end surface 121 of the electrode assembly 12 in the stacking direction is composed of the negative electrode coating portion 38 located at the first end in the stacking direction, and the second end surface 122 of the electrode assembly 12 in the stacking direction is the second in the stacking direction. It is composed of a negative electrode coating portion 38 located at two ends. The first end surface 121 and the second end surface 122 of the electrode assembly 12 are surfaces facing the long side wall 13c of the case body 13.

The positive electrode coating portion 28 located on the first end side in the stacking direction with respect to the winding shaft L and the positive electrode coating portion 28 located on the second end side in the stacking direction with respect to the winding shaft L are the positive electrode 20. Alternates in the longitudinal direction of. In other words, of the two positive electrode coated portions 28 adjacent to each other with the positive electrode exposed portion 29 sandwiched in the longitudinal direction of the positive electrode electrode 20, one positive electrode coated portion 28 is on the first end side in the stacking direction with respect to the winding shaft L. The other positive electrode coating portion 28 is located on the second end side in the stacking direction with respect to the winding shaft L.

Similarly, the negative electrode coating portion 38 located on the first end side in the stacking direction with respect to the winding shaft L and the negative electrode coating portion 38 located on the second end side in the stacking direction with respect to the winding shaft L It exists alternately in the longitudinal direction of the negative electrode 30. In other words, of the two negative electrode coated portions 38 adjacent to each other with the negative electrode exposed portion 39 sandwiched in the longitudinal direction of the negative electrode electrode 30, one of the negative electrode coated portions 38 is on the first end side in the stacking direction with respect to the winding shaft L. When located at, the other negative electrode coating portion 38 is located on the second end side in the stacking direction with respect to the winding shaft L.

In the electrode assembly 12, the positive electrode tabs 23 are arranged in a row in the stacking direction, and the negative electrode tabs 33 are arranged in a row in the stacking direction at a position different from the position where the positive electrode tabs 23 are arranged in a row. In the present embodiment, the positive electrode tabs 23 are arranged in a row in the stacking direction on one end side in the longitudinal direction of the positive electrode active material layers 24 and 25 and the negative electrode active material layers 34 and 35, and each negative electrode tab 33 is arranged in a row in the stacking direction. The active material layers 24 and 25 and the negative electrode active material layers 34 and 35 are lined up in a row in the stacking direction on the other end side in the longitudinal direction. As shown in FIG. 1, in the electrode assembly 12, a positive electrode tab group 15 in which a plurality of positive electrode tabs 23 arranged in a row are laminated, and a plurality of negative electrode tabs 33 arranged in a row at a position different from the positive electrode tab 23 are laminated. It also has a negative electrode tab group 16.

The electrode assembly 12 is centrally laminated with the first end-side laminated portion 12b located on one end side of the central laminated portion 12a in the longitudinal direction of the positive electrode active material layers 24 and 25 and the negative electrode active material layers 34 and 35. It has a second end-side laminated portion 12c located on the other end side of the portion 12a. The first end side laminated portion 12b constitutes one side portion of the electrode assembly 12 by being located on one side of the central laminated portion 12a, and the second end side laminated portion 12c is the central laminated portion 12a. By being located on the other side, the other side of the electrode assembly 12 is formed. The first end side laminated portion 12b and the second end side laminated portion 12c are portions in which the positive electrode exposed portion 29 and the negative electrode exposed portion 39 are alternately laminated via the separator 40. The first end side laminated portion 12b and the second end side laminated portion 12c face the long side wall 13c and the short side wall 13d of the case body 13.

The positive electrode exposed portion 29 constituting the first end side laminated portion 12b and the positive electrode exposed portion 29 forming the second end side laminated portion 12c exist alternately in the longitudinal direction of the positive electrode electrode 20. In other words, when one of the two positive electrode exposed portions 29 adjacent to each other with the positive electrode coated portion 28 sandwiched in the longitudinal direction of the positive electrode electrode 20 constitutes the first end side laminated portion 12b, the other The positive electrode exposed portion 29 constitutes the second end side laminated portion 12c.

Similarly, the negative electrode exposed portion 39 constituting the first end side laminated portion 12b and the negative electrode exposed portion 39 forming the second end side laminated portion 12c are alternately present in the longitudinal direction of the negative electrode electrode 30. In other words, when one of the two negative electrode exposed portions 39 adjacent to each other with the negative electrode coated portion 38 sandwiched in the longitudinal direction of the negative electrode electrode 30 constitutes the first end side laminated portion 12b, the other The negative electrode exposed portion 39 constitutes the second end side laminated portion 12c.

As described above, the positive electrode 20 and the negative electrode 30 are wound so that the first ends 20a and 30a are on the winding start side. Therefore, the dimension of the positive electrode exposed portion 29 in the longitudinal direction of the positive electrode electrode 20 is longer than that of the positive electrode exposed portion 29 located on the outer peripheral side of the first end side laminated portion 12b. Further, the dimension of the positive electrode exposed portion 29 in the longitudinal direction of the positive electrode electrode 20 is longer than that of the positive electrode exposed portion 29 located on the outer peripheral side of the second end side laminated portion 12c. The size of the negative electrode exposed portion 39 in the longitudinal direction of the negative electrode electrode 30 is longer than that of the negative electrode exposed portion 39 located on the outer peripheral side of the first end side laminated portion 12b. Further, the dimension of the negative electrode exposed portion 39 in the longitudinal direction of the negative electrode electrode 30 is longer than that of the negative electrode exposed portion 39 located on the outer peripheral side of the second end side laminated portion 12c.

The positive electrode exposed portion 29 has a flat portion 29a in the center along the longitudinal direction of the positive electrode main body 22, and connects the flat portions 29a and the positive electrode coating portion 28 on both sides of the flat portion 29a in the longitudinal direction of the positive electrode main body 22. It has a pair of curved portions 29b to be formed. The flat portions 29a of each positive electrode exposed portion 29 are laminated in the longitudinal direction of the positive electrode active material layers 24 and 25 and the negative electrode active material layers 34 and 35. Each curved portion 29b is curved so as to be convex in a direction away from the winding shaft L. Each curved portion 29b includes a positive electrode protruding portion 27 of the second positive electrode active material layer 25. That is, the positive electrode protruding portion 27 has an arc shape at the first end side laminated portion 12b or the second end side laminated portion 12c, and the connecting surface 25c is a curved surface. The degree of curvature of each curved portion 29b is as tight as the curved portion 29b of the positive electrode exposed portion 29 located on the inner peripheral side, and gentler as the curved portion 29b of the positive electrode exposed portion 29 located on the outer peripheral side.

The negative electrode exposed portion 39 has a flat portion 39a in the center along the longitudinal direction of the negative electrode main body 32, and connects the flat portions 39a and the negative electrode coating portion 38 on both sides of the flat portion 39a in the longitudinal direction of the negative electrode main body 32. It has a pair of curved portions 39b. The flat portion 39a of each negative electrode exposed portion 39 is laminated in the longitudinal direction of the positive electrode active material layers 24 and 25 and the negative electrode active material layers 34 and 35. Each curved portion 39b is curved so as to be convex in a direction away from the winding shaft L. Each curved portion 39b includes a negative electrode protruding portion 37 of the second negative electrode active material layer 35. That is, the negative electrode protruding portion 37 has an arc shape at the first end side laminated portion 12b or the second end side laminated portion 12c, and the connecting surface 35c is a curved surface. The degree of curvature of each curved portion 39b is as tight as the curved portion 39b of the negative electrode exposed portion 39 located on the inner peripheral side, and gentler as the curved portion 39b of the negative electrode exposed portion 39 located on the outer peripheral side.

As shown in FIG. 1, the secondary battery 10 includes a positive electrode terminal structure 17 and a negative electrode terminal structure 18 for extracting electricity from the electrode assembly 12. The positive electrode terminal structure 17 has a plate-shaped positive electrode conductive member 17a joined to the positive electrode tab group 15, and a rod-shaped positive electrode terminal 17b protruding from the positive electrode conductive member 17a. The negative electrode terminal structure 18 has a plate-shaped negative electrode conductive member 18a joined to the negative electrode tab group 16 and a rod-shaped negative electrode terminal 18b protruding from the negative electrode conductive member 18a. The positive electrode terminal 17b and the negative electrode terminal 18b each penetrate the lid 14 and project to the outside of the case 11 to connect the inside and outside of the case 11. A bus bar (not shown) that electrically connects the secondary batteries 10 to each other can be fixed to the positive electrode terminal 17b and the negative electrode terminal 18b. The secondary battery 10 includes an insulating ring 19 for insulating the lid 14 from the positive electrode terminal 17b or the negative electrode terminal 18b.

Here, among the electrode assembly 12 and the method for manufacturing the secondary battery 10 using the electrode assembly 12, the method for manufacturing the positive electrode 20 will be described with reference to FIGS. 5 and 6. Although the description of the method for manufacturing the negative electrode 30 is omitted, the negative electrode 30 is manufactured by the same method as the method for manufacturing the positive electrode 20.

First, as shown in FIG. 5, the active material is conveyed in the longitudinal direction to the first surface 210a and the second surface 210b of the long sheet-shaped metal foil material 210 as a current collector. The mixture 220 is applied intermittently.

When the active material mixture 220 is applied to the second surface 210b of the metal foil material 210, the gradual increase portion 221 for sequentially thickening the active material mixture 220 in the longitudinal direction of the metal foil material 210 and the length of the metal foil material 210 A constant-thickness portion 222 in which the thickness of the active material mixture 220 is constant in the direction and a gradual reduction portion 223 in which the active material mixture 220 is sequentially thinned in the longitudinal direction of the metal foil material 210 are set. One end of the constant thickness portion 222 in the longitudinal direction of the metal leaf material 210 is continuous with the thickest portion of the gradually increasing portion 221 and the other end of the constant thickness portion 222 is continuous with the thickest portion of the gradually decreasing portion 223. ing. The constant thickness portion 222 overlaps with the active material mixture 220 coated on the first surface 210a of the metal foil material 210 when viewed from the thickness direction of the metal foil material 210, and the gradual increase portion 221 and the gradual decrease portion 223 are formed. When viewed from the thickness direction of the metal foil material 210, it protrudes from the active material mixture 220 coated on the first surface 210a of the metal foil material 210. The metal leaf material 210 coated with the active material mixture 220 on the first surface 210a and the second surface 210b passes through a dryer (not shown).

Next, as shown in FIG. 6, the metal leaf material 210 after passing through the dryer is passed between the pair of press rolls 50 having a constant gap 50a. As a result, the positive electrode 20 is formed. A part of the gradually increasing portion 221 and the gradually decreasing portion 223 is pressed to become the positive electrode protruding portion 27 at the positive electrode electrode 20, and the constant thickness portion 222 is pressed to become the positive electrode main portion 26 at the positive electrode electrode 20. Since the thickness of the gradually increasing portion 221 and the gradually decreasing portion 223 is thinner than that of the constant thickness portion 222, the load received by the gradually increasing portion 221 and the gradually decreasing portion 223 when passing between the pair of press rolls 50 is the load received by the constant thickness portion 222. Smaller than Therefore, the density of the active material in the positive electrode protruding portion 27 formed by the gradually increasing portion 221 and the gradually decreasing portion 223 is smaller than the density of the active material in the positive electrode main portion 26 formed by the constant thickness portion 222. Therefore, the hardness of the positive electrode protruding portion 27 formed by the gradually increasing portion 221 and the gradually decreasing portion 223 is lower than the hardness of the positive electrode main portion 26 formed by the constant thickness portion 222.

The operation of this embodiment will be described.
Since the density of the active material in the positive electrode protruding portion 27 is lower than the density of the active material in the positive electrode main portion 26, the positive electrode protruding portion 27 can be deformed so as to be curved. When the positive electrode main portion 26 expands and the size of the central laminated portion 12a in the stacking direction increases, the positive electrode exposed portion 29 is provided with the positive electrode protruding portion 27, so that the positive electrode exposed portion 29 becomes the positive electrode coating portion 28. Bending at an angle close to a right angle from both ends of the is suppressed. Further, since the positive electrode protruding portion 27 is deformed in accordance with the expansion of the positive electrode main portion 26, the positive electrode exposed portion 29 is less likely to be pulled to both sides in the stacking direction. As a result, it is suppressed that the first positive electrode active material layer 24 is crushed by the positive electrode main body 22 at both ends of the positive electrode coating portion 28.

When the first positive electrode active material layer 24 is also provided on the opposite side of the positive electrode protruding portion 27 when viewed from the thickness direction of the positive electrode metal foil 21, a part of the first positive electrode active material layer 24 is also the first end. The side laminated portion 12b or the second end side laminated portion 12c will be formed. In this case, when the first positive electrode active material layer 24 expands, a compressive force acts on a portion of the first positive electrode active material layer 24 that constitutes the first end side laminated portion 12b or the second end side laminated portion 12c. The first positive electrode active material layer 24 may fall off. On the other hand, in the present embodiment, the first positive electrode active material layer 24 is not provided on the opposite side of the positive electrode protruding portion 27, that is, the first positive electrode active material layer 24 is the first end side laminated portion 12b or the second. Since the end-side laminated portion 12c is not formed, the first positive electrode active material layer 24 is suppressed from falling off.

Since the density of the active material in the negative electrode protruding portion 37 is lower than the density of the active material in the negative electrode main portion 36, the negative electrode protruding portion 37 can be deformed so as to be curved. When the negative electrode main portion 36 expands and the size of the central laminated portion 12a in the stacking direction increases, the negative electrode exposed portion 39 is provided with the negative electrode protruding portion 37, so that the negative electrode exposed portion 39 becomes the negative electrode coating portion 38. Bending at an angle close to a right angle from both ends of the is suppressed. Further, since the negative electrode protruding portion 37 is deformed in accordance with the expansion of the negative electrode main portion 36, the negative electrode exposed portion 39 is less likely to be pulled to both sides in the stacking direction. As a result, it is suppressed that the first negative electrode active material layer 34 is crushed by the negative electrode main body 32 at both ends of the negative electrode coating portion 38.

When the first negative electrode active material layer 34 is also provided on the opposite side of the negative electrode protruding portion 37 when viewed from the thickness direction of the negative electrode metal foil 31, a part of the first negative electrode active material layer 34 is also the first end. The side laminated portion 12b or the second end side laminated portion 12c will be formed. In this case, when the first negative electrode active material layer 34 expands, a compressive force acts on a portion of the first negative electrode active material layer 34 that constitutes the first end side laminated portion 12b or the second end side laminated portion 12c. The first negative electrode active material layer 34 may fall off. On the other hand, in the present embodiment, the first negative electrode active material layer 34 is not provided on the opposite side of the negative electrode protruding portion 37, that is, the first negative electrode active material layer 34 is the first end side laminated portion 12b or the second. Since the end-side laminated portion 12c is not formed, the first negative electrode active material layer 34 is suppressed from falling off.

The effect of this embodiment will be described.
(1-1) The positive electrode protruding portion 27 prevents the positive electrode exposed portion 29 from bending at an angle close to a right angle from both ends of the positive electrode coating portion 28. Further, due to the deformation of the positive electrode protruding portion 27, the positive electrode exposed portion 29 is less likely to be pulled to both sides in the stacking direction. Therefore, it is possible to prevent the first positive electrode active material layer 24 from being crushed by the positive electrode main body 22 at both ends of the positive electrode coating portion 28. Further, since the first positive electrode active material layer 24 does not constitute the first end side laminated portion 12b or the second end side laminated portion 12c, the first positive electrode active material layer 24 is suppressed from falling off during expansion.

The negative electrode protruding portion 37 prevents the negative electrode exposed portion 39 from bending at an angle close to a right angle from both ends of the negative electrode coating portion 38. Further, due to the deformation of the negative electrode protruding portion 37, the negative electrode exposed portion 39 is less likely to be pulled to both sides in the stacking direction. Therefore, it is possible to prevent the first negative electrode active material layer 34 from being crushed by the negative electrode main body 32 at both ends of the negative electrode coating portion 38. Further, since the first negative electrode active material layer 34 does not constitute the first end side laminated portion 12b or the second end side laminated portion 12c, the first negative electrode active material layer 34 is suppressed from falling off during expansion.

(1-2) In the negative electrode coating portion 38, the portion located outside the both ends of the positive electrode coating portion 28 tends to be curved toward the center in the stacking direction, so that the second negative electrode active material layer 35 is pulled. Although stress acts, cracking of the second negative electrode active material layer 35 can be suppressed by deforming the negative electrode protruding portion 37 having a lower active material density than the negative electrode main portion 36.

(1-3) When the first positive electrode active material layer 24 is also provided on the opposite side of the positive electrode protruding portion 27 sandwiching the positive electrode main body portion 22, the first positive electrode active material is wound when the positive electrode electrode 20 is wound. When the compressive force acts on the portion of the layer 24 located on the opposite side of the protruding portion 27, the first positive electrode active material layer 24 may repel and it may be difficult to wind the positive electrode 20. On the other hand, in the present embodiment, since the first positive electrode active material layer 24 is not provided on the opposite side of the positive electrode protruding portion 27 sandwiching the positive electrode main body portion 22, the positive electrode electrode 20 can be easily wound. ..

Similarly, when the first negative electrode active material layer 34 is also provided on the opposite side of the negative electrode protruding portion 37 sandwiching the negative electrode main body portion 32, the first negative electrode active material layer 34 is formed when the negative electrode electrode 30 is wound. Since the compressive force acts on the portion of the negative electrode located on the opposite side of the protruding portion 37, the first negative electrode active material layer 34 may repel and it may be difficult to wind the negative electrode 30. On the other hand, in the present embodiment, since the first negative electrode active material layer 34 is not provided on the opposite side of the negative electrode protruding portion 37 sandwiching the negative electrode main body portion 32, the work of winding the negative electrode electrode 30 becomes easy. ..

(Second Embodiment)
Hereinafter, a second embodiment in which the electrode assembly is embodied will be described with reference to FIG. In the second embodiment, only the parts different from the first embodiment will be described, and the description of the same configuration as the first embodiment will be omitted.

As shown in FIG. 7, in the second embodiment, only the second positive electrode active material layer 25 closest to the first end 20a of the positive electrode electrode 20 has the positive electrode protruding portion 27. That is, the five second positive electrode active material layers 25 other than the second positive electrode active material layer 25 closest to the first end 20a have the positive electrode main portion 26, but do not have the positive electrode protruding portion 27. Similarly, only the second negative electrode active material layer 35 closest to the first end 30a of the negative electrode electrode 30 has the negative electrode protruding portion 37. That is, the six second negative electrode active material layers 35 other than the second negative electrode active material layer 35 near the first end 30a have the negative electrode main portion 36, but do not have the negative electrode protruding portion 37.

The effect of this embodiment will be described. In the second embodiment, in addition to the effects (1-1) to (1-3) of the first embodiment, the following effects can be obtained.
(2-1) The degree of curvature of the positive electrode exposed portion 29 is as tight as the positive electrode exposed portion 29 located on the inner peripheral side in the electrode assembly 12, and as gentle as the positive electrode exposed portion 29 located on the outer peripheral side in the electrode assembly 12. .. Therefore, the force with which the positive electrode main body 22 tries to crush the first positive electrode active material layer 24 at both ends of the positive electrode coating portion 28 is larger toward the inner peripheral side and smaller toward the outer peripheral side in the electrode assembly 12. Therefore, by providing the positive electrode protruding portion 27 only on the second positive electrode active material layer 25 located on the innermost circumference, damage to the first positive electrode active material layer 24 located on the innermost circumference can be further suppressed. Further, the amount of the active material layer material used can be reduced as compared with the case where the positive electrode protruding portion 27 is provided in all the second positive electrode active material layers 25. Therefore, the cost of the positive electrode 20 can be suppressed.

The degree of curvature of the negative electrode exposed portion 39 is as tight as the negative electrode exposed portion 39 located on the inner peripheral side in the electrode assembly 12, and as gentle as the negative electrode exposed portion 39 located on the outer peripheral side in the electrode assembly 12. Therefore, the force with which the negative electrode main body 32 tries to crush the first negative electrode active material layer 34 at both ends of the negative electrode coating portion 38 is larger toward the inner peripheral side and smaller toward the outer peripheral side in the electrode assembly 12. Therefore, by providing the negative electrode protruding portion 37 on the second negative electrode active material layer 35 located on the innermost circumference, damage to the first negative electrode active material layer 34 located on the innermost circumference can be further suppressed. Further, the amount of the active material layer material used can be reduced as compared with the case where the negative electrode protruding portion 37 is provided in all the second negative electrode active material layers 35. Therefore, the cost of the negative electrode 30 can be suppressed.

(Third Embodiment)
Hereinafter, a third embodiment in which the electrode assembly is embodied will be described with reference to FIGS. 8 and 9. In the third embodiment, only the parts different from the first embodiment will be described, and the description of the same configuration as the first embodiment will be omitted.

As shown in FIG. 8A, in the third embodiment, the four second positive electrode active material layers 25 closer to the first end 20a of the positive electrode electrode 20 have the positive electrode protruding portion 27. That is, the two second positive electrode active material layers 25 near the second end 20b of the positive electrode electrode 20 have the positive electrode main portion 26, but do not have the positive electrode protruding portion 27. Similarly, only the four second negative electrode active material layers 35 closer to the first end 30a of the negative electrode electrode 30 have the negative electrode protruding portion 37. That is, the three second negative electrode active material layers 35 near the second end 30b of the negative electrode electrode 30 have the negative electrode main portion 36, but do not have the negative electrode protruding portion 37.

The dimensions of the positive electrode main portion 26 in the longitudinal direction of the second positive electrode active material layer 25 are substantially the same in all the second positive electrode active material layers 25 as in the first embodiment. On the other hand, the dimension X27 of the positive electrode protruding portion 27 in the longitudinal direction of the second positive electrode active material layer 25 is different for each second positive electrode active material layer 25.

FIG. 8B shows the second positive electrode active material layer 25 closest to the first end 20a of the positive electrode electrode 20 among the second positive electrode active material layer 25 having the positive electrode protruding portion 27, and FIG. 8C shows FIG. In the second positive electrode active material layer 25 having the positive electrode protruding portion 27, the second positive electrode active material layer 25 closest to the second end 20b of the positive electrode electrode 20 is shown. The dimension X27 of the positive electrode protruding portion 27 is as long as the second positive electrode active material layer 25 closest to the first end 20a of the positive electrode electrode 20 among the second positive electrode active material layer 25 having the positive electrode protruding portion 27, and is longer than that of the positive electrode 20. The second positive electrode active material layer 25, which is closest to the second end 20b, is shorter. That is, in the second positive electrode active material layer 25 having the positive electrode protruding portion 27, from the second positive electrode active material layer 25 closest to the first end 20a of the positive electrode electrode 20 to the second positive electrode active material layer 25 close to the second end 20b. The size X27 of the positive electrode protruding portion 27 gradually becomes shorter toward the direction.

Therefore, the dimensions of the second positive electrode active material layer 25 in the longitudinal direction also differ for each second positive electrode active material layer 25. The longitudinal dimension of the second positive electrode active material layer 25 is longer by the second positive electrode active material layer 25 closest to the first end 20a of the positive electrode electrode 20 among the second positive electrode active material layer 25 having the positive electrode protruding portion 27. The second positive electrode active material layer 25, which is closest to the second end 20b of the positive electrode 20, is shorter. That is, in the second positive electrode active material layer 25 having the positive electrode protruding portion 27, from the second positive electrode active material layer 25 closest to the first end 20a of the positive electrode electrode 20 to the second positive electrode active material layer 25 close to the second end 20b. The dimension of the second positive electrode active material layer 25 in the longitudinal direction gradually becomes shorter toward the direction.

The angle formed by the first surface 22a of the positive electrode body 22 and the connecting surface 24c is approximately the same for all the first positive electrode active material layers 24. On the other hand, the angle α2 formed by the second surface 22b of the positive electrode main body 22 and the connecting surface 25c is different for each second positive electrode active material layer 25. Specifically, the angle α2 is as small as the second positive electrode active material layer 25 closest to the first end 20a in the longitudinal direction of the positive electrode electrode 20 among the plurality of second positive electrode active material layers 25 having the positive electrode protruding portion 27, and the positive electrode is positive. The size of the second positive electrode active material layer 25, which is closest to the second end 20b in the longitudinal direction of the electrode 20, is larger. That is, in the plurality of second positive electrode active material layers 25 having the positive electrode protruding portion 27, the second positive electrode active material layer 25 closest to the first end 20a of the positive electrode electrode 20 to the second positive electrode active material closest to the second end 20b. The angle α2 gradually increases toward the layer 25. In the present embodiment, the angle α2 of the second positive electrode active material layer 25 closest to the first end 20a of the positive electrode 20 is 40 degrees, and the second positive electrode active material layer 25 closest to the second end 20b of the positive electrode 20. The angle α2 closer to the second end 20b in the above is 80 degrees. Therefore, the angle α2 is smaller than the angle α1.

Similarly, the dimensions of the negative electrode main portion 36 in the longitudinal direction of the second negative electrode active material layer 35 are substantially the same in all the second negative electrode active material layers 35 as in the first embodiment. On the other hand, the dimension X37 of the negative electrode protruding portion 37 in the longitudinal direction of the second negative electrode active material layer 35 differs for each second negative electrode active material layer 35. Specifically, the dimension X37 of the negative electrode protruding portion 37 is longer than that of the second negative electrode active material layer 35 having the negative electrode protruding portion 37, which is closest to the first end 30a of the negative electrode electrode 30, and the negative electrode. The second negative electrode active material layer 35, which is closest to the second end 30b of the electrode 30, is shorter. That is, in the second negative electrode active material layer 35 having the negative electrode protruding portion 37, from the second negative electrode active material layer 35 closest to the first end 30a of the negative electrode electrode 30 to the second negative electrode active material layer 35 close to the second end 30b. The size X37 of the negative electrode protruding portion 37 gradually becomes shorter as it goes toward it.

Therefore, the dimensions of the second negative electrode active material layer 35 in the longitudinal direction also differ for each second negative electrode active material layer 35. Specifically, the longitudinal dimension of the second negative electrode active material layer 35 is the second negative electrode active material layer closest to the first end 30a of the negative electrode electrode 30 among the second negative electrode active material layer 35 having the negative electrode protruding portion 37. It is as long as 35, and as short as the second negative electrode active material layer 35 closest to the second end 30b of the negative electrode 30. That is, in the second negative electrode active material layer 35 having the negative electrode protruding portion 37, from the second negative electrode active material layer 35 closest to the first end 30a of the negative electrode electrode 30 to the second negative electrode active material layer 35 close to the second end 30b. The dimension of the second negative electrode active material layer 35 in the longitudinal direction gradually becomes shorter toward the direction.

The angle formed by the first surface 32a of the negative electrode main body 32 and the connecting surface 34c of β1 is substantially the same in all the first negative electrode active material layers 34. On the other hand, the angle β2 formed by the second surface 32b of the negative electrode main body 32 and the connecting surface 35c is different for each second negative electrode active material layer 35. Specifically, the angle β2 is as small as the second negative electrode active material layer 35 closest to the first end 30a in the longitudinal direction of the negative electrode electrode 30 among the plurality of second negative electrode active material layers 35 having the negative electrode protruding portion 37, and the negative electrode. The size of the second negative electrode active material layer 35, which is closest to the second end 30b in the longitudinal direction of the electrode 30, is larger. That is, in the plurality of second negative electrode active material layers 35 having the negative electrode protruding portion 37, the second negative electrode active material layer 35 closest to the first end 30a of the negative electrode electrode 30 to the second negative electrode active material closest to the second end 30b. The angle β2 gradually increases toward the layer 35. In the present embodiment, the angle β2 of the second negative electrode active material layer 35 closest to the first end 30a of the negative electrode 30 is 40 degrees, and the second negative electrode active material layer 35 closest to the second end 30b of the negative electrode 30. The angle β2 closer to the second end 30b is 80 degrees. Therefore, the angle β2 is smaller than the angle β1.

As shown in FIG. 9, the dimension X27 of the positive electrode protruding portion 27 is the second positive electrode active material layer 25 located on the inner peripheral side of the electrode assembly 12 among the second positive electrode active material layer 25 having the positive electrode protruding portion 27. The positive electrode of the second positive electrode active material layer 25 is as long as the protruding portion 27, and is as short as the protruding portion 27 of the second positive electrode active material layer 25 located on the outer peripheral side of the electrode assembly 12. The size X37 of the negative electrode protruding portion 37 is as long as the negative electrode protruding portion 37 of the second negative electrode active material layer 35 located on the inner peripheral side of the electrode assembly 12 among the second negative electrode active material layer 35 having the negative electrode protruding portion 37. The negative electrode of the second negative electrode active material layer 35 located on the outer peripheral side of the electrode assembly 12 is as short as the protruding portion 37.

The effect of this embodiment will be described. In the third embodiment, in addition to the effects (1-1) to (1-3) of the first embodiment, the following effects can be obtained.
(3-1) The degree of curvature of the positive electrode exposed portion 29 is as tight as the positive electrode exposed portion 29 located on the inner peripheral side in the electrode assembly 12, and as gentle as the positive electrode exposed portion 29 located on the outer peripheral side in the electrode assembly 12. .. Therefore, the force with which the positive electrode main body 22 tries to crush the first positive electrode active material layer 24 at both ends of the positive electrode coating portion 28 is larger toward the inner peripheral side and smaller toward the outer peripheral side in the electrode assembly 12. Therefore, by increasing the size X27 of the positive electrode protruding portion 27 as much as the positive electrode protruding portion 27 located on the inner peripheral side, the positive electrode exposed portion 29 can be bent at an angle close to a right angle from both ends of the positive electrode coating portion 28. More suppressed. Therefore, damage to the first positive electrode active material layer 24 can be further suppressed.

The degree of curvature of the negative electrode exposed portion 39 is as tight as the negative electrode exposed portion 39 located on the inner peripheral side in the electrode assembly 12, and as gentle as the negative electrode exposed portion 39 located on the outer peripheral side in the electrode assembly 12. Therefore, the force with which the negative electrode main body 32 tries to crush the first negative electrode active material layer 34 at both ends of the negative electrode coating portion 38 is larger toward the inner peripheral side and smaller toward the outer peripheral side in the electrode assembly 12. Therefore, by increasing the size X37 of the negative electrode protruding portion 37 as much as the negative electrode protruding portion 37 located on the inner peripheral side, the negative electrode exposed portion 39 can be bent at an angle close to a right angle from both ends of the negative electrode coating portion 38. More suppressed. Therefore, damage to the first negative electrode active material layer 34 can be further suppressed.

This embodiment can be modified and implemented as follows. The present embodiment and modified examples can be implemented in combination with each other within a technically consistent range.
○ The second positive electrode active material layer 25 may have a positive electrode protruding portion 27 only on one side of the positive electrode main portion 26 in the longitudinal direction of the positive electrode main body portion 22. Similarly, the second negative electrode active material layer 35 may have a negative electrode protruding portion 37 only on one side of the negative electrode main portion 36 in the longitudinal direction of the negative electrode main body portion 32.

○ In the positive electrode 20, the number of the second positive electrode active material layer 25 having the positive electrode protruding portion 27 may be changed as appropriate. Similarly, in the negative electrode electrode 30, the number of the second negative electrode active material layer 35 having the negative electrode protruding portion 37 may be appropriately changed.

○ If at least one of the plurality of second positive electrode active material layers 25 has a positive electrode protruding portion 27, the second negative electrode active material layer 35 does not have to have a negative electrode protruding portion 37. On the contrary, if at least one of the plurality of second negative electrode active material layers 35 has the negative electrode protruding portion 37, the second positive electrode active material layer 25 does not have to have the positive electrode protruding portion 27. ..

○ Depending on the coating conditions and the like, portions may be formed at both ends of the first positive electrode active material layer 24 in the longitudinal direction in which the thickness of the first positive electrode active material layer 24 becomes thinner toward the ends. In this case, the angle α1 formed by the first surface 22a of the positive electrode main body 22 and the connecting surface 24c of the first positive electrode active material layer 24 is smaller than 90 degrees. However, the angle α2 is smaller than the angle α1.

Similarly, depending on the coating conditions and the like, portions of the first negative electrode active material layer 34 in the longitudinal direction may be formed at both ends in the longitudinal direction so that the thickness of the first negative electrode active material layer 34 becomes thinner toward the ends. In this case, the angle β1 formed by the first surface 32a of the negative electrode main body 32 and the connecting surface 34c of the first negative electrode active material layer 34 is smaller than 90 degrees. However, the angle β2 is smaller than the angle β1.

○ The longitudinal dimension of the first positive electrode active material layer 24 does not have to be the same for all the first positive electrode active material layers 24 as long as it is shorter than the longitudinal dimension of the second positive electrode active material layer 25. Further, the longitudinal dimension of the first negative electrode active material layer 34 does not have to be the same in all the first negative electrode active material layers 34 as long as it is shorter than the longitudinal dimension of the second negative electrode active material layer 35.

○ The longitudinal dimension of the first negative electrode active material layer 34 may be the same as the longitudinal dimension of the first positive electrode active material layer 24, or may be smaller than the longitudinal dimension of the first positive electrode active material layer 24. Good. Further, the longitudinal dimension of the second negative electrode active material layer 35 may be the same as the longitudinal dimension of the second positive electrode active material layer 25, or smaller than the longitudinal dimension of the second positive electrode active material layer 25. May be good.

○ The positive electrode metal leaf 21 may be, for example, a woven or net-like sheet. Further, the negative electrode metal foil 31 may be, for example, a woven or net-like sheet.
○ The specific structures of the positive electrode terminal structure 17 and the negative electrode terminal structure 18 may be appropriately changed as long as electricity can be exchanged with the electrode assembly 12.

○ The secondary battery 10 may be a lithium ion secondary battery or another secondary battery. In short, it suffices as long as the ions move between the active material for the negative electrode and the active material for the negative electrode and transfer charges.

○ The power storage device can also be applied to a power storage device other than a secondary battery, such as a capacitor.

12 ... Electrode assembly, 12a ... Central laminated portion as a flat portion, 12b ... First end side laminated portion as a side portion, 12c ... Second end side laminated portion as a side portion, 20 ... Positive electrode, 21 ... Collection Positive electrode metal foil as an electric body, 22a ... 1st surface, 22b ... 2nd surface, 24 ... 1st positive electrode active material layer as the 1st active material layer, 25 ... 2nd positive electrode as the 2nd active material layer Active material layer, 27 ... Positive electrode protruding part as protruding part, 28 ... Positive electrode coating part as coating part, 29 ... Positive electrode exposed part as exposed part, 30 ... Negative electrode electrode, 31 ... Negative electrode metal as current collector Foil, 32a ... 1st surface, 32b ... 2nd surface, 34 ... 1st negative electrode active material layer as the first active material layer, 35 ... 2nd negative electrode active material layer as the 2nd active material layer, 37 ... Negative electrode protruding portion as a protruding portion, 38 ... Negative electrode coated portion as a coated portion, 39 ... Negative electrode coated portion as an exposed portion, 40 ... Separator.

Claims (4)

A long sheet-shaped current collector, a first active material layer intermittently arranged on the first surface of the current collector, and a second surface of the current collector opposite to the first surface. The positive electrode and the negative electrode having the second active material layer intermittently arranged in the above are wound through the separator so that the first surface becomes the inner peripheral surface and the second surface becomes the outer peripheral surface. Being done
In the current collector, a flat portion in which the first active material layer and the coated portion on which the second active material layer is arranged are laminated flatly, and
A pair of side portions that are located on both sides of the flat portion and are laminated in a state where the exposed portion, which is an exposed portion of the current collector, is curved.
It is an electrode assembly having
The second active material layer protrudes outward from the main portion overlapping the first active material layer and the first active material layer when viewed from the thickness direction of the current collector. Moreover, it has a protruding portion that becomes thinner from the main portion toward the exposed portion.
An electrode assembly characterized in that the density of the active material in the protruding portion is lower than the density of the active material in the main portion. The electrode assembly according to claim 1, wherein the dimension of the protruding portion is longer than that of the protruding portion located on the inner peripheral side of the electrode assembly. The electrode assembly according to claim 1, wherein only the second active material layer located on the innermost circumference of the electrode assembly has the protruding portion. Both ends of the second active material layer of the positive electrode are located inside the both ends of the second active material layer of the negative electrode.
The electrode assembly according to any one of claims 1 to 3, wherein the second active material layer of the negative electrode has a protruding portion.

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