Power storage device

Abstract

To provide a power storage device that can reduce the local application of a load on a wound electrode body.SOLUTION: A power storage device includes a wound electrode body having a winding axis extending in a predetermined direction and configured in such a way that a multilayer body including a band-shaped positive electrode, a band-shaped negative electrode, and a band-shaped separator is wound spirally around the winding axis, and a case that accommodates an electrolyte solution and the wound electrode body. The wound electrode body includes an outer peripheral surface facing the case. Each of the positive electrode and the negative electrode includes a coated part where an active material is coated, and a non-coated part where the active material is not coated. In the wound electrode body, a concave part that is depressed from the outer peripheral surface side toward the winding axis is formed by the non-coated part, and a thick part is formed in the multilayer body by folding at least one of the negative electrode, the positive electrode, and the separator on the outer peripheral surface side. The thick part is provided at a position that fills the concave part.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present disclosure relates to a power storage device.

Background Art

[0002] Conventionally, as disclosed in Japanese Patent Application Laid-Open No. 4-206341 (Patent Document 1), a battery including a wound electrode body configured by winding, in a state where first and second strip-shaped electrodes having electrode active materials formed on both surfaces of a strip-shaped current collector are laminated via a strip-shaped separator, in a spiral shape along its length direction is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the wound electrode body, there are uncoated portions where the active material is not coated at the start and / or end of winding. Further, in order to attach tabs or improve the liquid injection property, an uncoated portion may be provided between the coated portions. Due to such uncoated portions, recesses may occur on the outer peripheral surface of the wound electrode body. When the wound electrode body with a recess on the outer peripheral surface is housed in a case, there is a risk that a local load is applied to the wound electrode body.

[0005] The present disclosure provides a power storage device capable of reducing the application of a local load to the wound electrode body.

Means for Solving the Problems

[0006] According to an aspect of the present disclosure, a power storage device includes a wound electrode body configured by winding a laminate including a wound shaft extending in a predetermined direction, a strip-shaped positive electrode, a strip-shaped negative electrode, and a strip-shaped separator around the wound shaft, a case that houses an electrolytic solution and the wound electrode body, and the wound electrode body includes an outer peripheral surface facing the case. Each of the positive electrode and the negative electrode has a coated portion coated with an active material and an uncoated portion not coated with the active material. In the wound electrode body, a recess recessed from the outer peripheral surface side toward the wound shaft side is formed by the uncoated portion. In the wound electrode body, on the outer peripheral surface side, a film thickness portion is formed in the laminate by folding at least one of the negative electrode, the positive electrode, and the separator. The film thickness portion is provided at a position filling the recess.

[0007] According to the above configuration, the recess caused by the uncoated portion can be filled by the film thickness portion formed by at least one of the positive electrode, the negative electrode, and the separator. Therefore, the outer peripheral surface of the wound electrode body can be made less uneven. As a result, compared with a configuration not provided with the film thickness portion, it is possible to reduce the application of a local load to the wound electrode body.

[0008] Preferably, the length of the separator around the wound shaft is longer than that of the negative electrode and the positive electrode. The film thickness portion is formed only by the separator among the positive electrode, the negative electrode, and the separator. According to the above configuration, the film thickness portion can be formed only by the separator.

[0009] Preferably, the uncoated portion extends in a predetermined direction. The film thickness portion is formed by folding the separator so as to fit into the recess in the circumferential direction of the outer peripheral surface.

[0010] According to the above configuration, the outer peripheral surface of the wound electrode body can be made less uneven.

[0011] Preferably, the film thickness portion is welded to the recess.

[0012] According to the above configuration, the film thickness portion can be fixed. Therefore, compared with the configuration in which the film thickness portion is not fixed, it is possible to further reduce the application of a local load to the wound electrode body.

Effect of the Invention

[0013] According to the present disclosure, in the power storage device, it is possible to reduce the application of a local load to the wound electrode body.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following description, the same members are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

[0016] FIG. 1 is a cross-sectional view of the power storage device. As shown in FIG. 1, the power storage device 10 includes a wound electrode body 100 and a case 200. The wound electrode body 100 includes a strip-shaped positive electrode 110, a strip-shaped negative electrode 120, a strip-shaped separator 130, a positive electrode tab lead 140, and a negative electrode tab lead 150.

[0017] FIG. 2 is a perspective view of the wound electrode body 100. As shown in FIG. 2, the wound electrode body 100 has a winding axis Ax extending in the Z direction (a predetermined direction). The wound electrode body 100 is formed by spirally winding a laminate including a strip-shaped positive electrode 110, a strip-shaped negative electrode 120, and a strip-shaped separator 130 around the winding axis Ax. Specifically, the separator 130 includes a first separator 132 and a second separator 134. The laminate is formed by stacking the negative electrode 120, the first separator 132, the positive electrode 110, and the second separator 134 in this order. The laminate is wound in the direction of arrow D in FIG. 3 (corresponding to the longitudinal direction L of the laminate).

[0018] Referring again to FIG. 1, the wound electrode body 100 includes an outer peripheral surface 160 facing the case 200. The separator 130 is provided between the positive electrode 110 and the negative electrode 120. The separator 130 separates the positive electrode 110 and the negative electrode 120 while allowing ions (such as lithium ions) to move between the positive electrode 110 and the negative electrode 120. The separator 130 includes the first separator 132 and the second separator 134 as described above.

[0019] The positive electrode 110 includes a positive electrode current collector foil and a positive electrode active material layer. The positive electrode active material layer is coated on a part of the positive electrode current collector foil. Thus, the positive electrode 110 includes a coated portion coated with the positive electrode active material and an uncoated portion where the positive electrode active material layer is not coated.

[0020] For the positive electrode current collector foil, for example, aluminum or the like is used. The positive electrode active material layer is formed by coating a positive electrode slurry on the surface of the positive electrode current collector foil and drying it. The positive electrode active material layer is in close contact with the separator 130.

[0021] The negative electrode 120 includes a negative electrode current collector foil and a negative electrode active material layer. The negative electrode active material layer is coated on a part of the negative electrode current collector foil. Thus, the negative electrode 120 includes a coated portion coated with the negative electrode active material and an uncoated portion where the negative electrode active material is not coated. The coated portion and the uncoated portion will be described later (FIG. 3).

[0022] For the negative electrode current collector foil, for example, a copper foil or the like is used. The negative electrode active material layer is formed by applying a negative electrode slurry onto the surface of the negative electrode current collector foil and drying it. The negative electrode active material layer is in close contact with the separator 130.

[0023] The positive electrode tab lead 140 is provided so as to protrude from the positive electrode current collector foil of the positive electrode 110 toward one side in the axial direction Z (the Z1 side). The negative electrode tab lead 150 is provided so as to protrude from the negative electrode current collector foil of the negative electrode 120 toward the other side in the axial direction Z (the Z2 side).

[0024] The case 200 houses the wound electrode body 100 and the electrolytic solution. The case 200 is also referred to as a "cell case". The case 200 has an outer peripheral surface 210, a first end portion 220, a second end portion 230, and an inner peripheral surface 240.

[0025] The outer peripheral surface 210 is cylindrical and is disposed outside in the radial direction R of the wound electrode body 100. The outer peripheral surface 210 is formed of copper, aluminum, or the like. The outer peripheral surface 210 is in contact with the negative electrode current collector foil of the negative electrode 120 provided on the outermost periphery of the wound electrode body 100.

[0026] The inner peripheral surface 240 extends from the first hole portion 221 to the second hole portion 231. The inner peripheral surface 240 is disposed inside in the radial direction R of the wound electrode body 100. The inner peripheral surface 240 has a core portion 241, a first insulating end portion 242, and a second insulating end portion 243.

[0027] The core portion 241 has a cylindrical outer shape. The core portion 241 is disposed inside in the radial direction R of the wound electrode body 100. From the viewpoint of heat dissipation, the core portion 241 is preferably formed of a metal such as copper or aluminum.

[0028] The power storage device 10 further includes a positive side insulating plate 300, a negative side insulating plate 400, and a CID (Current Interrupt Device) 500. The positive side insulating plate 300 and the negative side insulating plate 400 are housed in the case 200.

[0029] FIG. 3 is a diagram for explaining a coated portion and an uncoated portion. FIG. 3 shows the state of the positive electrode 110 before the laminate is wound. As shown in FIG. 3, the end S is the start side of winding. The end E1 is the end side of winding. In FIG. 3, the longitudinal direction of the positive electrode 110 is the left - right (horizontal) direction. The short - hand direction of the positive electrode 110 is not shown. The thickness direction of the positive electrode 110 is the up - down (vertical) direction.

[0030] The positive electrode 110 has a positive - electrode current - collecting foil 111 and a positive - electrode active - material layer 112. The positive - electrode active - material layer 112 is provided on both sides of the positive - electrode current - collecting foil 111. The positive - electrode active - material layer 112 on one side and the positive - electrode active - material layer 112 on the other side are provided at positions symmetric with respect to the positive - electrode current - collecting foil 111.

[0031] Specifically, the positive - electrode current - collecting foil 111 includes a coated portion 118 coated with a positive - electrode active material for forming the positive - electrode active - material layer 112 and an uncoated portion 119 where the positive - electrode active material is not coated. In this example, uncoated portions 119 exist at both ends in the longitudinal direction of the positive electrode 110. Also, in order to connect the positive - electrode tab lead 140 to the positive - electrode current - collecting foil 111, a part of the longitudinal direction of the positive electrode 110 is an uncoated portion (not shown).

[0032] Similarly, the negative electrode 120 has a negative - electrode current - collecting foil 121 and a negative - electrode active - material layer 122. The negative - electrode active - material layer 122 is provided on both sides of the negative - electrode current - collecting foil 121. The negative - electrode active - material layer 122 on one side and the negative - electrode active - material layer 122 on the other side are provided at positions symmetric with respect to the negative - electrode current - collecting foil 121.

[0033] Specifically, the negative - electrode current - collecting foil 121 includes a coated portion 128 coated with a negative - electrode active material for forming the negative - electrode active - material layer 122 and an uncoated portion 129 where the negative - electrode active material is not coated. In this example, uncoated portions 129 exist at both ends in the longitudinal direction of the negative electrode 120. Also, in order to connect the negative - electrode tab lead 150 to the negative - electrode current - collecting foil 121, a part of the longitudinal direction of the negative electrode 120 is an uncoated portion (not shown).

[0034] FIG. 4 is a diagram for explaining the layer structure of the wound electrode body 100. As described above, the wound electrode body 100 is formed by winding a laminate in which a negative electrode 120, a first separator 132, a positive electrode 110, and a second separator 134 are laminated in this order around a winding axis Ax in a spiral shape.

[0035] As shown in FIG. 4, the end S is the start side of winding of the negative electrode 120, the positive electrode 110, and the first and second separators 132 and 134. The end E1 is the end side of winding of the negative electrode 120, the positive electrode 110, and the second separator 134. The end E2 is the end side of winding of the first separator 132.

[0036] In this example, the length of the first separator 132 in the longitudinal direction (L direction) is longer than the lengths of the negative electrode 120, the second separator 134, and the positive electrode 110 in the longitudinal direction. Specifically, the length of the first separator 132 around the winding axis Ax is longer than that of the positive electrode 110, the negative electrode 120, and the second separator 134. The first separator 132 is longer than the positive electrode 110, the negative electrode 120, and the second separator 134 by a distance Ls in the longitudinal direction.

[0037] Note that the present invention is not limited to this, and the lengths of the first and second separators 132 and 134 around the winding axis Ax may be made longer than the length of the negative electrode 120 around the winding axis Ax and the length of the positive electrode 110 around the winding axis Ax. Also, the length of the negative electrode 120 around the winding axis Ax may be made longer than the lengths of the first and second separators 132 and 134 around the winding axis Ax and the length of the positive electrode 110 around the winding axis Ax. Furthermore, the length of the positive electrode 110 around the winding axis Ax may be made longer than the lengths of the first and second separators 132 and 134 around the winding axis Ax and the length of the negative electrode 120 around the winding axis Ax.

[0038] The uncoated portion 119 of the positive electrode 110 and the uncoated portion 129 of the negative electrode 120 extend in the Z direction (winding axis Ax direction) of FIG. 1. Specifically, both end portions in the short side direction of the positive electrode 110 are the uncoated portion 119 of the positive electrode 110. Similarly, both end portions in the short side direction of the negative electrode 120 are the uncoated portion 129 of the negative electrode 120.

[0039] FIG. 5 is a state transition diagram for explaining a part of the manufacturing process of the wound electrode body 100. As shown in state (A) of FIG. 5, by winding the above-described laminate around the winding shaft Ax, the first intermediate body 100_1 of the wound electrode body 100 is generated. At the stage where the first intermediate body 100_1 is generated by winding the laminate around the winding shaft Ax in this way, a recess 170 is formed in the first intermediate body 100_1 that is recessed from the outer peripheral surface 160 side toward the winding shaft Ax side by the uncoated portions 119, 129. Specifically, as shown in FIG. 3, since the thicknesses of the uncoated portions 119, 129 are thinner than the thicknesses of the coated portions 118, 128, the recess 170 is formed in the first intermediate body 100_1. In this example, in the direction from the recess 170 toward the winding shaft Ax, the uncoated portion 119 of the positive electrode 110 and the uncoated portion 129 of the negative electrode 120 at least partially overlap.

[0040] The recess 170 extends in the first intermediate body 100_1 from the upper end portion 191 on the positive-side insulating plate 300 (see FIG. 1) side to the lower end portion 192 on the negative-side insulating plate 400 side. In this example, in a side view of the wound electrode body 100, the recess 170 has a rectangular shape with the long side parallel to the winding shaft Ax.

[0041] Incidentally, as described with reference to FIG. 4, the longitudinal length of the first separator 132 is longer than the longitudinal length of the negative electrode 120, the longitudinal length of the first separator 132, and the longitudinal length of the positive electrode 110. Therefore, in the first intermediate body 100_1, only the rear end side (the winding end side) of the first separator 132 among the negative electrode 120, the positive electrode 110, and the first and second separators 132, 134 is left without being wound.

[0042] After the first intermediate body 100_1 is generated, as shown in state (B), the rear end side of the first separator 132 is folded back. Thereby, the second intermediate body 100_2 is generated. In this example, the rear end side of the first separator 132 is folded back inward. Specifically, the first separator 132 is folded into a mountain fold along a fold line parallel to the winding shaft Ax.

[0043] After the second intermediate body 100_2 is generated, the rear end side of the first separator 132 is further folded back. In this example, the rear end side of the first separator 132 is further folded back inward. Specifically, the first separator 132 is further folded into a valley fold along a fold line parallel to the winding axis Ax. More specifically, the first separator 132 is folded so as to fit into the recess 170 in the circumferential direction of the outer peripheral surface 160.

[0044] By folding the first separator 132, a film thickness portion 180 is formed in the wound laminate. In this example, the film thickness portion 180 is formed in the laminate by folding the first separator 132 back twice. For the sake of simplicity of explanation, the number of folds is set to two, but the number of folds may be one or three or more. The number of folds may be determined by the length of the first separator 132 and the length in the outer circumferential direction of the recess 170.

[0045] As shown in state (C), by accommodating the film thickness portion 180 in the recess 170, a third intermediate body 100_3 is formed. Next, in the state of the third intermediate body 100_3, the film thickness portion 180 is welded to the recess 170. By applying heat to the region P30 of the film thickness portion 180, the film thickness portion 180 is welded to the recess 170. In this example, as shown in state (D), heat is applied to a plurality of regions P31, P32, P33, P34 arranged in the vertical direction among the surface regions facing the outer periphery in the film thickness portion 180.

[0046] Through the above processing, a wound electrode body 100 is generated in which the film thickness portion 180 is provided at a position corresponding to the recess 170. The film thickness portion 180 is provided at a position filling the recess 170. It is preferable that the film thickness portion 180 fills the entire recess 170. However, it is not limited thereto, and at least a part of the recess 170 may be filled.

[0047] As described above, by applying heat only to the plurality of regions P31, P32, P33, P34, the thick film portion 180 is partially heat-welded to the concave portion 170. Therefore, the electrolytic solution can penetrate into the inside of the wound electrode body 100 from the non-welded portions. Therefore, the electrolytic solution is more likely to penetrate into the inside of the wound electrode body 100 than in the case where the thick film portion 180 is entirely heat-welded to the concave portion 170.

[0048] In addition, in the above description, the case where the first separator 132 is folded into a mountain fold along a fold line parallel to the winding axis Ax has been described as an example, but the present invention is not limited thereto. The first separator 132 may be folded into a valley fold along a fold line parallel to the winding axis Ax. The first separator 132 may be folded into a zigzag along a fold line parallel to the winding axis Ax.

[0049] <Advantages> (1) As described above, the power storage device 10 includes a wound electrode body 100 and a case 200 that houses the electrolytic solution and the wound electrode body 100. The wound electrode body 100 has a winding axis Ax extending in the Z direction, and is configured by winding a laminate including a strip-shaped positive electrode 110, a strip-shaped negative electrode 120, and a strip-shaped separator 130 in a spiral around the winding axis Ax.

[0050] The wound electrode body 100 includes an outer peripheral surface 160 facing the case 200. Each of the positive electrode 110 and the negative electrode 120 has a coated portion 118, 128 coated with an active material and an uncoated portion 119, 129 not coated with the active material.

[0051] In the wound electrode body 100, concave portions 170 recessed from the outer peripheral surface 160 side toward the winding axis Ax side are formed by the uncoated portions 119, 129. In the wound electrode body 100, a thick film portion 180 is formed in the laminate by folding back the separator 130 (the first separator 132 in this example) on the outer peripheral surface 160 side. The thick film portion 180 is provided at a position filling the concave portion 170.

[0052] According to such a configuration, the film thickness portion 180 formed by the separator 130 can fill the recesses 170 caused by the uncoated portions 119 and 129. Therefore, the outer peripheral surface 160 of the wound electrode body 100 can be made in a state with less unevenness. As a result, compared with a configuration not provided with the film thickness portion 180, it is possible to reduce the application of a local load to the wound electrode body 100.

[0053] The separator 130 is thin and it is difficult to obtain welding strength. However, by folding back the separator 130 as described above, good bonding strength with respect to the recess 170 of the film thickness portion 180 can be obtained.

[0054] Note that, by folding back at least one of the first and second separators 132 and 134 constituting the separator 130, the film thickness portion 180 may be formed. Furthermore, not limited to this, the film thickness portion 180 may be formed by folding back at least one of the positive electrode 110, the negative electrode 120, and the separator 130. For example, the film thickness portion 180 may be formed by folding back only the positive electrode 110 among the positive electrode 110, the negative electrode 120, and the separator 130. The film thickness portion 180 may be formed by folding back only the negative electrode 120. The film thickness portion 180 may be formed by folding back the positive electrode 110, the negative electrode 120, and the separator 130. Note that, when the film thickness portion 180 is formed by folding back the positive electrode 110, the negative electrode 120, and the separator 130, the longitudinal lengths of the positive electrode 110, the negative electrode 120, and the separator 130 (specifically, the first and second separators 132 and 134) may be substantially the same, different from FIG. 4. Even in such a case, similarly to the above, it is possible to reduce the application of a local load to the wound electrode body 100.

[0055] (2) As shown in FIG. 4, the separator 130 has a length around the winding axis Ax that is longer than the negative electrode 120 and the positive electrode 110. Therefore, the film thickness portion 180 can be formed only by the separator 130.

[0056] (3) As shown in FIG. 4, the uncoated portions 119 and 129 extend in the Z direction. As shown in FIG. 5, the film thickness portion 180 is formed by folding the separator 130 so as to fit into the concave portion 170 in the circumferential direction of the outer peripheral surface 160. According to such a configuration, the outer peripheral surface 160 of the wound electrode body 100 can be made into a state with less unevenness.

[0057] (4) As shown in the state (D) of FIG. 5, the film thickness portion 180 is welded to the concave portion 170. According to such a configuration, the film thickness portion 180 can be fixed. Therefore, it is not necessary to fix the film thickness portion 180 to the outer peripheral surface 160 using a tape.

[0058] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present disclosure is shown by the claims, and all modifications within the meaning and scope equivalent to the claims are intended to be included.

Explanation of Reference Numerals

[0059] 10 Power storage device, 100 Wound electrode body, 100_1 First intermediate body, 100_2 Second intermediate body, 100_3 Third intermediate body, 110 Positive electrode, 111 Positive electrode current collector foil, 112 Positive electrode active material layer, 118, 128 Coated portions, 119, 129 Uncoated portions, 120 Negative electrode, 121 Negative electrode current collector foil, 122 Negative electrode active material layer, 130 Separator, 132 First separator, 134 Second separator, 140 Positive electrode tab lead, 150 Negative electrode tab lead, 160, 210 Outer peripheral surface, 170 Concave portion, 180 Film thickness portion, 191 Upper end portion, 192 Lower end portion, 200 Case, 220 First end portion, 221 First hole portion, 230 Second end portion, 231 Second hole portion, 240 Inner peripheral surface, 241 Core portion, 242 First insulating end portion, 243 Second insulating end portion, 300 Positive side insulating plate, 400 Negative side insulating plate, Ax Winding axis, E1, E2, S End portions, P30, P31, P32, P33, P34 Regions.

Claims

1. A wound electrode body configured by winding a laminate including a winding shaft extending in a predetermined direction, a strip-shaped positive electrode, a strip-shaped negative electrode, and a strip-shaped separator in a spiral around the winding shaft; A case that houses an electrolytic solution and the wound electrode body, and The wound electrode body includes an outer peripheral surface facing the case, Each of the positive electrode and the negative electrode has a coated portion coated with an active material and an uncoated portion not coated with the active material, In the wound electrode body, An uncoated portion forms a recess recessed from the outer peripheral surface side toward the winding shaft side, and On the outer peripheral surface side, a film thickness portion is formed in the laminate by folding at least one of the negative electrode, the positive electrode, and the separator, The film thickness portion is provided at a position filling the recess, a power storage device.

2. The separator has a length around the winding shaft longer than that of the negative electrode and the positive electrode, The film thickness portion is formed only by the separator among the positive electrode, the negative electrode, and the separator, the power storage device according to claim 1.

3. The uncoated portion extends in the predetermined direction, The film thickness portion is formed by folding the separator so as to fit into the recess in the circumferential direction of the outer peripheral surface, the power storage device according to claim 2.

4. The film thickness portion is welded to the recess, the power storage device according to any one of claims 1 to 3.

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