Method for manufacturing power storage device, and power storage device

Abstract

This method for manufacturing a power storage device comprises: a step for alternately laminating an electrode foil and separators, and causing at least a part of an active-material uncoated portion of the laminated electrode foil to protrude from end portions of the separators in a direction along a short side of the electrode foil; a step for bending at least a part of the active-material uncoated portion at a plurality of locations to form a plurality of extension portions extending in a direction intersecting the electrode foil so as to cover the separators when viewed from the direction along the short side of the electrode foil; and a step for laser-welding the active-material uncoated portion and a current collector plate by irradiating an outer surface of the current collector plate with laser light in a state in which an inner surface of the current collector plate is in contact with a part of the active-material uncoated portion that is outside the plurality of extension portions in the direction along the short side of the electrode foil.

Description

Method for manufacturing an electricity storage device, and electricity storage device

[0001] This disclosure relates to a method for manufacturing an electricity storage device, and to an electricity storage device. This disclosure claims priority to Japanese Patent Application No. 2024-147207, filed on August 29, 2024, the contents of which are incorporated herein by reference.

[0002] Patent Document 1 discloses a joining method in which positive and negative electrode plates are stacked with a separator interposed therebetween to form a spirally wound electrode assembly, and current collector plates are joined by laser welding to a protruding portion of a positive electrode current collector protruding from one end of the electrode assembly in the axial direction of the spiral and a protruding portion of a negative electrode current collector protruding from the other end. In Patent Document 1, one end of the electrode assembly in the axial direction of the spiral is pressed, thereby bending the protruding portion of the positive electrode current collector at one end of the axial direction of the spiral and the protruding portion of the negative electrode current collector at the other end in the radial direction of the spiral to form flat portions. In Patent Document 1, a laser is irradiated from the outer surface of the current collector plate outside the axial direction of the spiral, with the positive electrode current collector plate and the negative electrode current collector plate pressed parallel to the flat portions, to laser-weld the protruding portion of the positive electrode current collector to the current collector plate and also laser-weld the protruding portion of the negative electrode current collector to the current collector plate.

[0003] Japanese Patent Application Publication No. 2011-129328

[0004] In the joining method described in Patent Document 1, the laser beam may reach the inside of the electrode plate assembly in the non-bent portions of the flat portion, potentially causing the separator to melt. Furthermore, in Patent Document 1, there are no bent portions of the current collector between each welding point and the separator. Therefore, even if laser welding is performed in the bent portions of the flat portion, if the laser beam penetrates the welding point or spatter occurs, the spatter or heat may reach the separator, potentially causing the separator to melt. If the separator melts, there is a risk of an internal short circuit or self-discharge failure.

[0005] An object of aspects of the present disclosure is to provide a method for manufacturing an electricity storage device that can suppress melting of the separator, and an electricity storage device.

[0006] A method for manufacturing an electricity storage device according to one aspect of the present disclosure includes the steps of alternately stacking electrode foils and separators and causing at least a portion of an uncoated portion of the stacked electrode foil to protrude from an end of the separator in a direction along a short side of the electrode foil; bending at least a portion of the uncoated portion of the active material at multiple locations to form multiple extensions that extend in a direction intersecting the electrode foil so as to cover the separator when viewed from the direction along the short side of the electrode foil; and irradiating the outer surface of the current collector with laser light while contacting the inner surface of the current collector with portions of the uncoated portion of the active material that are outward of the multiple extensions in the direction along the short side of the electrode foil, thereby laser-welding the uncoated portion of the active material to the current collector.

[0007] According to an aspect of the present disclosure, it is possible to provide a method for manufacturing an electricity storage device that can suppress melting of the separator, and an electricity storage device.

[0008] FIG. 1 is a cross-sectional view showing a schematic configuration of an electricity storage device according to a first embodiment. FIG. 2 is a cross-sectional view of a laminate in which an element according to the first embodiment is unfolded. FIG. 3 is a plan view of the laminate shown in FIG. 2. FIG. 3 is a side view showing the laminate shown in FIG. 2 in a spirally wound state. FIG. 4 is a cross-sectional view of a joint between a negative electrode active material uncoated portion and a negative electrode current collector plate according to the first embodiment. FIG. 5 is a view showing a joint between an active material uncoated portion and a current collector plate in the absence of compression. FIG. 6 is a view showing a joint between an active material uncoated portion and a current collector plate in the presence of compression. FIG. 7 is a flowchart of a method for manufacturing an electricity storage device according to the first embodiment. FIG. 8 is a process diagram of the method for manufacturing an electricity storage device according to the first embodiment. FIG. 9 is a cross-sectional view taken along the central axis a of the element according to the first embodiment. FIG. 10 is a view showing the amount of compression according to the first embodiment. FIG. 11 is a view showing a laser welding process according to a comparative example. FIG. 12 is a view showing a laser welding process according to the first embodiment. FIG. 13 is a process diagram of a method for manufacturing an electricity storage device according to a second embodiment.

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the present embodiments, a lithium ion capacitor (LIC) will be described as an example of an electricity storage device. The electricity storage device of the present embodiments has a structure in which an electric double layer capacitor serves as a positive electrode and a lithium ion battery serves as a negative electrode.

[0010] In the following description, expressions indicating relative or absolute arrangements, such as "parallel," "orthogonal," "center," and "coaxial," do not only mean such arrangements or states in the strict sense, but also include arrangements or states in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. In the drawings used in the following description, the scale of each component may be changed as appropriate to make each component recognizable.

[0011] <Electricity storage device> Fig. 1 is a cross-sectional view showing a schematic configuration of an electricity storage device 1 according to a first embodiment. Fig. 2 is a cross-sectional view of a laminate in which elements 3 according to the first embodiment are developed. Fig. 3 is a plan view of the laminate shown in Fig. 2. Fig. 4 is a side view showing the laminate shown in Fig. 2 in a spirally wound state. Referring to Figs. 1 to 4 together, the electricity storage device 1 includes a casing 2, elements 3, current collector plates 4, terminal plates 5, and an electrolyte solution 6.

[0012] The casing 2 is made of a metal such as aluminum (for example, aluminum alone or an alloy). The casing 2 has a cylindrical shape with a bottom. The casing 2 defines an accommodation space 7 that accommodates the element 3, the current collector plate 4, and the electrolyte 6. A terminal plate 5 is attached to an opening 8 of the casing 2 by drawing or the like. The opening 8 of the casing 2 is closed by the terminal plate 5.

[0013] The element 3 includes a plurality of electrode foils 9 and a plurality of separators 10. The element 3 is formed in a cylindrical shape that can be accommodated in the accommodation space 7 of the casing 2. The element 3 is accommodated in the accommodation space 7 together with an electrolyte 6. The central axis a (see FIG. 1 ) of the element 3 extends along the central axis of the casing 2 when accommodated in the accommodation space 7 of the casing 2.

[0014] The element 3 includes a positive electrode foil 9P and a negative electrode foil 9N as electrode foils 9. In the following description, the direction in which the central axis a of the element 3 (see FIG. 1 ) extends will be referred to as the central axis direction Da. The side of the central axis direction Da on which the opening 8 of the casing 2 is located will be referred to as the first central axis direction side Da1. The side of the central axis direction Da opposite to the side on which the opening 8 of the casing 2 is located will be referred to as the second central axis direction side Da2.

[0015] The positive electrode foil 9P includes an aluminum layer 12 made of aluminum (e.g., aluminum alone or an alloy), and a positive electrode active material layer 13 formed by applying an active material to each of the front and back surfaces of the aluminum layer 12. The negative electrode foil 9N includes a copper layer 14 made of copper or the like (e.g., copper alone or an alloy), and a negative electrode active material layer 15 formed by applying an active material to each of the front and back surfaces of the copper layer 14. Each of the aluminum layer 12 and the copper layer 14 has a thickness of, for example, 6 μm or more and 20 μm or less.

[0016] Each of the positive electrode foil 9P and the negative electrode foil 9N has a rectangular shape in a plan view in the unfolded state shown in Fig. 3. Short sides 16, 17 of each of the positive electrode foil 9P and the negative electrode foil 9N extend in the central axis direction Da. Long sides 18, 19 of each of the positive electrode foil 9P and the negative electrode foil 9N extend in a direction perpendicular to the central axis direction Da in a plan view in the unfolded state shown in Fig. 3. In the example shown in the figure, the dimension of the long side 18 of the positive electrode foil 9P is smaller than the dimension of the long side 19 of the negative electrode foil 9N, and the dimension of the short side 16 of the positive electrode foil 9P is equal to (specifically, slightly smaller than) the dimension of the short side 17 of the negative electrode foil 9N.

[0017] The separator 10 is made of an electrically insulating material that maintains electrical insulation between at least the electrodes of the power storage device 1. The separator 10 is made of, for example, polypropylene resin. The separator 10 is sheet-shaped. The separator 10 is disposed between the positive electrode foil 9P and the negative electrode foil 9N. The separator 10 is disposed so as to sandwich the negative electrode foil 9N.

[0018] The separator 10 has a rectangular shape in a plan view in the unfolded state shown in FIG. 3 . The short sides 20 of the separator 10 extend in the central axis direction Da. The long sides 21 of the separator 10 extend in a direction perpendicular to the central axis direction Da in a plan view in the unfolded state shown in FIG. 3 . The dimension of the long sides 21 of the separator 10 is larger than the dimension of the long sides 18 of the positive electrode foil 9P and the dimension of the long sides 19 of the negative electrode foil 9N. The dimension of the short sides 20 of the separator 10 is larger than the dimension of the short sides 16 of the positive electrode foil 9P and the dimension of the short sides 17 of the negative electrode foil 9N. The separator 10 has a thickness of, for example, 18 μm or more and 22 μm or less.

[0019] At least a portion of the active material uncoated portion 11 protrudes beyond the end of the separator 10 in a direction along the short sides 16, 17 of the electrode foil 9. The direction along the short sides 16, 17 of the electrode foil 9 corresponds to the central axis direction Da. The element 3 has, as the multiple active material uncoated portions 11, a negative electrode active material uncoated portion 11N on a first side Da1 in the central axis direction and a positive electrode active material uncoated portion 11P on a second side Da2 in the central axis direction.

[0020] The positive electrode active material uncoated portion 11P protrudes in the direction along the short side 16 of the positive electrode foil 9P toward the second side Da2 in the central axis direction beyond the end of the separator 10. In the element 3, the positive electrode foil 9P is arranged so as to be shifted toward the second side Da2 in the central axis direction relative to the separator 10, so that the positive electrode active material uncoated portion 11P protrudes from the end of the separator 10 toward the second side Da2 in the central axis direction.

[0021] The negative electrode active material uncoated portion 11N protrudes in the direction along the short side 17 of the negative electrode foil 9N toward the first side Da1 in the central axis direction beyond the end of the separator 10. In the element 3, the negative electrode foil 9N is arranged offset toward the first side Da1 in the central axis direction with respect to the separator 10, so that the negative electrode active material uncoated portion 11N protrudes from the end of the separator 10 toward the first side Da1 in the central axis direction.

[0022] 2 to 4 , the element 3 is formed in a spiral shape around a central axis a by winding a stack of multiple electrode foils 9 and multiple separators 10 around, for example, a cylindrical roller R. Each of the positive electrode foil 9P, negative electrode foil 9N, and separator 10 constituting the element 3 has a spiral shape when viewed from the central axis direction Da.

[0023] A separator 10 is provided on the outer peripheral surface of the cylindrical element 3. An adhesive tape T or the like is wound around each of the edge portions on the first side Da1 in the central axis direction and the second side Da2 in the central axis direction of the outer peripheral surface of the cylindrical element 3. This prevents the end portion 25 of the separator 10 from spreading outward in the radial direction around the central axis a.

[0024] FIG. 5 is a cross-sectional view of a joint between a negative electrode active material uncoated portion 11N and a negative electrode current collector plate 4N according to the first embodiment. Referring also to FIG. 5 , the energy storage device 1 includes alternately stacked electrode foils 9 and separators 10, a laminated portion 45 (see FIG. 2 ) in which at least a portion of the active material uncoated portion 11 of the stacked electrode foils 9 protrudes beyond the end of the separator 10 in a direction along the short sides 16 and 17 of the electrode foils 9, and a current collector plate 4 having an inner surface 27 fixed to the active material uncoated portion 11 via a weld 26. The example in FIG. 5 schematically illustrates the joint between the negative electrode active material uncoated portion 11N and the negative electrode current collector plate 4N as the joint between the active material uncoated portion 11 and the current collector plate 4. Although not shown, the joint between the positive electrode active material uncoated portion 11P and the positive electrode current collector plate 4P is also configured similarly to the example in FIG. 5 .

[0025] Active material uncoated portion 11 has a plurality of extending portions 61, 62 extending in directions V1, V2 intersecting electrode foil 9 so as to cover separator 10 when viewed from a direction along short sides 16, 17 of electrode foil 9. Inner surface 27 of current collector plate 4 is fixed via welds 26 to a portion of active material uncoated portion 11 that is outer than the plurality of extending portions 61, 62 in the direction along short sides 16, 17 of electrode foil 9.

[0026] The multiple extending portions 61, 62 extend in directions V1, V2 (corresponding to directions intersecting the electrode foil 9) intersecting the central axis direction Da so as to cover the separator 10 when viewed from a direction along the short sides 16, 17 of the electrode foil 9. The example in Figure 5 shows a schematic configuration of the multiple extending portions 61, 62 on the negative electrode active material uncoated portion 11N side. Although not shown, the multiple extending portions 61, 62 on the positive electrode active material uncoated portion 11P side are also configured in the same manner as the example in Figure 5.

[0027] The plurality of extending portions 61, 62 are arranged midway in the central axis direction Da (corresponding to the direction along the short sides 16, 17 of the electrode foil 9) in the active material uncoated portion 11. The laminated portion 45 forms a spirally wound cylindrical body 46 (see FIG. 4 ).

[0028] In the example of Figure 5, the active material uncoated portion 11 is composed of an inner end portion 60 that is located on the inner end side of the cylinder 46 in the central axis direction Da (the side opposite the collector plate 4 in the central axis direction Da) and extends along the central axis direction Da, an outer end portion 63 that is located on the outer end side of the central axis direction Da (the side toward the collector plate 4 in the central axis direction Da) and extends along the central axis direction Da, and a plurality of extension portions 61, 62 that are located between the inner end portion 60 and the outer end portion 63.

[0029] 5 , the multiple extension portions 61, 62 include a first extension portion 61 extending from the outer end of the inner end portion 60 in a first direction V1 intersecting the central axis direction Da, and a second extension portion 62 extending from the outer end of the first extension portion 61 in a second direction V2 intersecting the first direction V1. Although not shown, the multiple extension portions may further include a third extension portion extending from the outer end of the second extension portion 62 in a third direction intersecting the second direction V2, or may further include a fourth extension portion extending from the outer end of the third extension portion in a fourth direction intersecting the third direction. The configuration of the multiple extension portions can be changed depending on design specifications.

[0030] The current collector 4 is fixed to the active material uncoated portion 11 via a weld 26. In this embodiment, the multiple current collectors 4 include two current collectors 4: a positive current collector 4P and a negative current collector 4N. Each of the positive current collector 4P and the negative current collector 4N is formed in a flat plate shape with a circular outer edge centered on the central axis a. Each of the positive current collector 4P and the negative current collector 4N has an inner surface 27 facing the active material uncoated portion 11 in the central axis direction Da, and an outer surface 28 (the outer surface 28 is back-to-back with the inner surface 27) facing the opposite side of the inner surface 27 in the central axis direction Da.

[0031] The positive electrode current collector 4P is formed of, for example, the same metal material as the positive electrode active material uncoated portion 11P. The positive electrode current collector 4P is formed of, for example, aluminum alone or an alloy. The negative electrode current collector 4N is formed of, for example, the same metal material as the negative electrode active material uncoated portion 11N. The negative electrode current collector 4N is formed of, for example, copper alone or an alloy.

[0032] 1 and 5 , a convex portion 29 that protrudes inward in the central axis direction Da (toward the active material uncoated portion 11) is formed in the center of the current collector plate 4. A through-hole 30 that opens in the central axis direction Da is formed in the convex portion 29 of the current collector plate 4. A hollow portion 31 that has a circular cross section and extends in the central axis direction Da is formed in the center of the element 3. The convex portion 29 of the current collector plate 4 is inserted into the hollow portion 31 of the element 3.

[0033] Inner surface 27 of current collector 4 is fixed via weld 26 to a portion of active material uncoated portion 11 that is outer than multiple extending portions 61, 62 in the direction along short sides 16, 17 of electrode foil 9. Weld marks 40 are formed on outer surface 28 of current collector 4 at positions corresponding to welds 26 formed on inner surface 27. In other words, inner surface 27 of current collector 4 is fixed to the outer end of active material uncoated portion 11 via welds 26 that are laser-welded by irradiating outer surface 28 of current collector 4 with laser light.

[0034] The terminal plate 5 closes the opening 8 of the casing 2. The terminal plate 5 includes a terminal plate body 35, a pressure adjustment valve 36, and a sealing member 37. The terminal plate body 35 is cylindrical and smaller than the casing 2 when viewed in the central axis direction Da. A hole 35h opening in the central axis direction Da is formed in the center of the terminal plate body 35. The pressure adjustment valve 36 is disposed in the center of the terminal plate body 35. The pressure adjustment valve 36 adjusts the pressure of the storage space 7 via the hole 35h. The sealing member 37 is made of an elastic material such as rubber. The sealing member 37 seals the gap between the inner circumferential surface of the opening 8 of the casing 2 and the outer circumferential portion of the terminal plate body 35. After the electrolyte 6 is injected into the storage space 7 through the hole 35h in the terminal plate body 35, the pressure adjustment valve 36 is attached to the center of the terminal plate body 35 to close the hole 35h.

[0035] Fig. 6 is a diagram showing the joint between the uncoated active material portion and the current collector plate when no compression is applied. Fig. 7 is a diagram showing the joint between the uncoated active material portion and the current collector plate when compression is applied. The state shown in Fig. 6 corresponds to a state in which the outer end portion of the cylinder 46 in the central axis direction Da extends along the central axis direction Da (a state in which the uncoated active material portion 11 does not have multiple extension portions 61, 62). The state shown in Fig. 7 corresponds to a state in which the outer end portion of the cylinder 46 in the central axis direction Da buckles (a state in which the uncoated active material portion 11 has multiple extension portions 61, 62).

[0036] Buckling refers to a phenomenon in which a structure undergoes sudden deformation (large deflection) when compressed under a predetermined load (when the load is gradually applied). In the buckled state, the multiple extensions 61, 62 become densely intertwined due to buckling (see FIG. 7). Note that FIG. 5 is a schematic diagram illustrating a portion of the state shown in FIG. 7. Although FIG. 7 shows the state of the positive electrode side as an example, this technology is applicable to both positive and negative electrodes throughout.

[0037] <Method of manufacturing an electricity storage device> Fig. 8 is a flowchart of a method of manufacturing an electricity storage device 1 according to the first embodiment. Fig. 9 is a process diagram of a method of manufacturing an electricity storage device 1 according to the first embodiment. Fig. 10 is a cross-sectional view taken along the central axis a of an element 3 according to the first embodiment. Fig. 11 is a diagram showing the amount of compression according to the first embodiment. Referring also to Figs. 8 to 11 , the method of manufacturing an electricity storage device 1 includes a step of protruding the active material uncoated portion 11 (step S01 shown in Fig. 8 ), a step of forming a plurality of extension portions 61, 62 (step S02 shown in Fig. 8 ), and a laser welding step (step S03 shown in Fig. 8 ).

[0038] In the step of causing the active material uncoated portions 11 to protrude (step S01 shown in FIG. 8 ), electrode foils 9 and separators 10 are alternately stacked, and at least a portion of the active material uncoated portions 11 of the stacked electrode foils 9 is caused to protrude from the end of the separator 10 in a direction along the short sides 16 and 17 of the electrode foils 9. For example, as shown in FIG. 3 , an aluminum positive electrode foil 9P is arranged so as to be offset toward the second side Da2 in the central axis direction relative to the separator 10, causing the positive electrode active material uncoated portions 11P to protrude from the end of the separator 10 toward the second side Da2 in the central axis direction. In addition, a copper negative electrode foil 9N is arranged so as to be offset toward the first side Da1 in the central axis direction relative to the separator 10, causing the negative electrode active material uncoated portions 11N to protrude from the end of the separator 10 toward the first side Da1 in the central axis direction.

[0039] In the step of protruding the uncoated active material portions 11, the electrode foils 9 and the separators 10 are alternately stacked and then spirally wound to form a cylindrical body 46. For example, the stack is spirally wound in the direction of the arrow shown in FIG. 2 to form a cylindrical body. Then, adhesive tape T (see FIG. 4) is wound around both ends of the separator 10 in the central axis direction Da that are exposed on the outer peripheral surface of the cylindrical body. After the step of protruding the uncoated active material portions 11, the process proceeds to the step of forming the plurality of extension portions 61, 62 (step S02 shown in FIG. 8).

[0040] In the step of forming the plurality of extensions 61, 62 (step S02 shown in FIG. 8 ), at least a portion of the active material uncoated portion 11 is bent at multiple locations to form the plurality of extensions 61, 62 extending in directions V1, V2 intersecting the electrode foil 9 so as to cover the separator 10 when viewed from the direction along the short sides 16, 17 of the electrode foil 9. In the step of forming the plurality of extensions 61, 62, the plurality of extensions 61, 62 are formed in the active material uncoated portion 11 midway along the direction along the short sides 16, 17 of the electrode foil 9. In the step of forming the plurality of extensions 61, 62, the outer end side portions of the cylinder 46 in the central axis direction Da are buckled.

[0041] 9, a pressing jig 50 is pressed against the outer end portion of the cylindrical body 46 in the central axis direction Da (the positive electrode active material uncoated portion 11P and the negative electrode active material uncoated portion 11N of the cylindrically formed element 3 shown in FIG. 10) from the outside in the central axis direction Da. This pressing jig 50 is formed, for example, in the shape of a cylinder with a bottom.

[0042] For example, the pressing jig 50 may be pressed against the outer end portion of the cylindrical body 46 in the central axis direction Da, one side at a time. For example, with the central portion of the cylindrical body 46 in the central axis direction Da clamped, the pressing jig 50 may be pressed against either the positive electrode active material uncoated portion 11P or the negative electrode active material uncoated portion 11N of the cylindrically formed element 3 from one side, and then the pressing jig 50 may be pressed against the other side. For example, multiple extension portions 61, 62 may be formed on either the positive electrode active material uncoated portion 11P or the negative electrode active material uncoated portion 11N, and then multiple extension portions 61, 62 may be formed on the other side. This allows the positive electrode active material uncoated portion 11P and the negative electrode active material uncoated portion 11N to be individually managed, thereby suppressing dimensional variations, positional misalignment, and the like.

[0043] The buckling load P satisfies formula (1) when n is the terminal condition coefficient, E is the modulus of longitudinal elasticity, I is the second moment of area, and l is the length of the portion to be buckled. As shown in Fig. 3 , the length l of the portion to be buckled corresponds to the length Da in the central axis direction of each of the positive electrode active material uncoated portion 11P and the negative electrode active material uncoated portion 11N.

[0044]

[0045] Since the buckling load P can be appropriately set by using formula (1), a more stable buckling state can be achieved (see FIG. 7). In this embodiment, the length l of the portion to be buckled is set to 5 mm or more.

[0046] The length l of the buckled portion may be, for example, 20 mm or less. In the electricity storage device 1, in order to maximize the capacity for the same volume, the active material coated portion (the portion coated with active material) may be made long and the active material uncoated portion (the portion not coated with active material) may be made short. Because the buckled portion corresponds to the active material uncoated portion, it is easier to maximize the capacity for the same volume compared to when the length l of the buckled portion exceeds 20 mm.

[0047] The compression amount shown in Figure 11 corresponds to the displacement between the outer end of the cylinder 46 in the central axis direction Da before compression and the outer end of the cylinder 46 in the central axis direction Da after compression. The smaller the compression amount, the less buckling occurs, and the greater the impact on the separator 10 (the degree of spatter and thermal impact). For example, the compression amount of the buckling portion is preferably 1.85 mm or more. This can suppress melting of the separator 10 compared to when the compression amount is less than 1.85 mm. After the process of forming the multiple extension portions 61, 62, the process proceeds to the laser welding process (step S03 shown in Figure 8).

[0048] In the laser welding step (step S03 shown in FIG. 8 ), active material uncoated portion 11 is laser welded to current collector plate 4. Specifically, in a state where inner surface 27 of current collector plate 4 is in contact with a portion of active material uncoated portion 11 that is more outer than multiple extension portions 61, 62 in the direction along short sides 16, 17 of electrode foil 9, laser light is irradiated onto outer surface 28 of current collector plate 4, thereby laser welding active material uncoated portion 11 to current collector plate 4.

[0049] The structure in which the active material uncoated portion 11 and the current collector plate 4 are joined by the method described above is housed in the casing 2 after the terminal plate body 35 is welded to the current collector plate 4. The casing 2 and the current collector plate 4P are then welded together, and the opening 8 of the casing 2 is closed with a sealing member 37. The electrolyte 6 is then injected through the hole 35h in the terminal plate body 35. The pressure adjustment valve 36 is then attached to the terminal plate body 35. With the above steps, the electricity storage device 1 is completed.

[0050] Fig. 12 is a diagram showing a laser welding process according to a comparative example. Fig. 13 is a diagram showing a laser welding process according to the first embodiment. The state shown in Fig. 12 corresponds to a state in which the outer end portion of the cylinder 46 in the central axis direction Da extends along the central axis direction Da (a state in which the active material uncoated portion 11 does not have multiple extension portions 61, 62). The state shown in Fig. 13 corresponds to a state in which the outer end portion of the cylinder 46 in the central axis direction Da is buckled (a state in which the active material uncoated portion 11 has multiple extension portions 61, 62).

[0051] In the comparative example, when the outer surface 28 of the current collector plate 4 is irradiated with laser light, there is a high possibility that the laser light will reach the separator 10. In this case, the separator 10 will melt (see FIG. 12).

[0052] In this embodiment, when laser light is irradiated onto the outer surface 28 of the current collector plate 4, the laser light is blocked by the multiple extensions 61, 62 before it reaches the separator 10. Furthermore, even if spatter occurs during laser welding, the multiple extensions 61, 62 can block the spatter and thermal effects. Therefore, the possibility of the separator 10 melting is low.

[0053] <Effects> As described above, the manufacturing method for the electricity storage device 1 of the present embodiment includes the steps of alternately stacking the electrode foils 9 and the separators 10 and causing at least some of the active material uncoated portions 11 of the stacked electrode foils 9 to protrude from the end of the separator 10 in a direction along the short sides 16, 17 of the electrode foil 9; bending at least some of the active material uncoated portions 11 at multiple locations to form multiple extension portions 61, 62 extending in directions V1, V2 intersecting the electrode foil 9 so as to cover the separator 10 when viewed from the direction along the short sides 16, 17 of the electrode foil 9; and irradiating the outer side 28 of the current collector plate 4 with laser light, while bringing the inner side 27 of the current collector plate 4 into contact with parts of the active material uncoated portions 11 that are more outer than the multiple extension portions 61, 62 in the direction along the short sides 16, 17 of the electrode foil 9, to laser-weld the active material uncoated portions 11 and the current collector plate 4. According to this method, multiple extensions 61, 62 are formed that extend in directions V1, V2 intersecting electrode foil 9 so as to cover separator 10 when viewed from the direction along short sides 16, 17 of electrode foil 9, thereby preventing laser light from reaching separator 10. Furthermore, even if spatter occurs when laser welding active material uncoated portion 11 and current collector plate 4, the multiple extensions 61, 62 can block the spatter and thermal effects. Therefore, a method for manufacturing electricity storage device 1 that can prevent separator 10 from melting can be provided.

[0054] In the present embodiment, in the step of forming the plurality of extension portions 61, 62, the plurality of extension portions 61, 62 are formed in the active material uncoated portion 11 midway along the short sides 16, 17 of the electrode foil 9. According to this method, the plurality of extension portions 61, 62 are formed in the active material uncoated portion 11 midway along the short sides 16, 17 of the electrode foil 9, and thus spatter and thermal influence can be blocked midway by the plurality of extension portions 61, 62. Therefore, melting of the separator 10 can be more effectively suppressed.

[0055] In this embodiment, in the step of protruding the active material uncoated portions 11, the electrode foils 9 and the separators 10 are alternately stacked and then spirally wound to form the cylindrical body 46. In the step of forming the plurality of extension portions 61, 62, the portion of the cylindrical body 46 on the outer end side in the central axis direction Da is buckled. According to this method, the portion of the cylindrical body 46 on the outer end side in the central axis direction Da is buckled, so that the plurality of extension portions 61, 62 are formed so as to be densely intertwined. This further enhances the effect of preventing spatter and thermal effects. This, in turn, more effectively suppresses melting of the separator 10.

[0056] In this embodiment, the length l of the portion to be buckled is set to 5 mm or more. This method reduces the buckling load P, making buckling easier. From the above formula (1), it can be seen that the buckling load P is inversely proportional to the square of the length l of the portion to be buckled. For example, a comparative example will be taken where the length l of the portion to be buckled is set to 2.5 mm. In this embodiment, the length l of the portion to be buckled is set to 5 mm or more, so the buckling load P is less than one-fourth of that in the comparative example, making buckling easier.

[0057] <Second embodiment> Fig. 14 is a process diagram of a method for manufacturing an electricity storage device according to a second embodiment. Hereinafter, the method for manufacturing an electricity storage device according to the second embodiment will be described with reference to Fig. 14. In Fig. 14, the same components as those in the above-described embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0058] In this embodiment, in the process of protruding the active material uncoated portion 11, the electrode foil 9 and the separator 10 are alternately stacked and then wound in a spiral to form a cylindrical body 46, and in the process of forming the multiple extension portions 61, 62, the portion of the cylinder 46 on the outer end side in the central axis direction Da is compressed in a tapered shape.

[0059] 14, a pressing jig 150 is pressed against the outer end portion of the cylindrical body 46 in the central axis direction Da (the positive electrode active material uncoated portion 11P and the negative electrode active material uncoated portion 11N of the cylindrically formed element 3 shown in FIG. 10) from the outside in the central axis direction Da. This pressing jig 150 is formed, for example, in the shape of a cylinder with a bottom and a tapered inner circumferential surface.

[0060] For example, the pressing jig 150 may be pressed against the outer end portion of the cylindrical body 46 in the central axis direction Da, one side at a time. For example, with the central portion of the cylindrical body 46 in the central axis direction Da clamped, the pressing jig 150 may be pressed against either the positive electrode active material uncoated portion 11P or the negative electrode active material uncoated portion 11N of the cylindrically formed element 3 from one side, and then the pressing jig 150 may be pressed against the other side. For example, multiple extension portions 61, 62 may be formed on either the positive electrode active material uncoated portion 11P or the negative electrode active material uncoated portion 11N, and then multiple extension portions 61, 62 may be formed on the other side. This allows the positive electrode active material uncoated portion 11P and the negative electrode active material uncoated portion 11N to be individually managed, thereby suppressing dimensional variations, positional misalignment, and the like.

[0061] After the process of forming the plurality of extension portions 61, 62, the process proceeds to the laser welding process. Then, after the terminal plate body 35 is welded to the current collector plate 4, the structure is housed in the casing 2, as in the above-described embodiment, to complete the electricity storage device.

[0062] In this embodiment, in the step of protruding the active material uncoated portions 11, the electrode foils 9 and the separators 10 are alternately stacked and then spirally wound to form the cylindrical body 46. In the step of forming the multiple extension portions 61, 62, the outer end portion of the cylindrical body 46 in the central axis direction Da is tapered and compressed. According to this method, the outer end portion of the cylindrical body 46 in the central axis direction Da is tapered and compressed, so that the multiple extension portions 61, 62 are formed to be more densely intertwined. This further enhances the effect of preventing spatter and thermal effects. Therefore, melting of the separator 10 can be more effectively suppressed.

[0063] <Modifications> In the above embodiment, the step of forming the multiple extension portions has been described with reference to an example in which multiple extension portions are formed in the uncoated portion of the active material along the short side of the electrode foil. However, this is not limiting. For example, multiple extension portions may be formed on the outer edge of the uncoated portion of the active material along the short side of the electrode foil. For example, multiple extension portions may not be formed in the uncoated portion of the active material along the short side of the electrode foil. The manner in which the multiple extension portions are formed can be changed according to design specifications.

[0064] In the above embodiment, the step of forming the active material uncoated portion involves alternately stacking electrode foils and separators and then spirally winding them to form a cylindrical body, and the step of forming the multiple extension portions involves buckling the outer end portion of the cylinder in the central axis direction. However, this is not limited to this. For example, the manufacturing method of the present disclosure can be applied even when the cylinder is not spirally wound. For example, the manufacturing method of the present disclosure can be applied even when the outer end portion of the cylinder in the central axis direction is not buckled.

[0065] In the above embodiment, an example has been described in which the buckling load P satisfies formula (1) when the end condition coefficient is n, the longitudinal elastic modulus is E, the moment of inertia is I, and the length of the portion to be buckled is l. However, this is not limiting. For example, the buckling load may be set using a formula other than formula (1). The manner in which the buckling load is set can be changed depending on the design specifications.

[0066] In the above embodiment, the length l of the buckling portion is 5 mm or more, but this is not limiting. For example, the length l of the buckling portion may be less than 5 mm. The length l of the buckling portion can be changed depending on the design specifications.

[0067] In the above-described embodiment, a lithium ion capacitor (LIC) has been described as an example of the power storage device, but the present invention is not limited to this. For example, the power storage device may be a capacitor other than a lithium ion capacitor or a secondary battery. The configuration of the power storage device may be changed according to design specifications.

[0068] Although one embodiment has been described above with reference to the drawings, the specific configuration is not limited to that described above, and additions, omissions, substitutions, and other modifications to the configuration are possible within the scope of the present disclosure, and the above-described embodiments can also be combined as appropriate.

[0069] 1...electricity storage device, 4...current collector plate, 9...electrode foil, 10...separator, 11...active material uncoated portion, 26...welded portion, 27...inner surface, 28...outer surface, 45...laminated portion, 46...cylinder, 61...first extension portion, 62...second extension portion, Da...central axis direction (direction along the short side of the electrode foil), l...length of portion to be buckled, V1...first direction (direction intersecting the electrode foil), V2...second direction (direction intersecting the electrode foil)

Claims

1. A method for manufacturing an electricity storage device, comprising: a step of alternately stacking electrode foils and separators and causing at least some of the active material uncoated portions of the stacked electrode foils to protrude from the end of the separator in a direction along the short sides of the electrode foil; a step of bending at least some of the active material uncoated portions at multiple locations to form multiple extension portions that extend in a direction intersecting the electrode foil so as to cover the separator when viewed from the direction along the short sides of the electrode foil; and a step of irradiating the outer surface of the current collector plate with laser light, with the inner surface of the current collector plate in contact with parts of the active material uncoated portions that are outer than the multiple extension portions in the direction along the short sides of the electrode foil, to laser-weld the active material uncoated portions and the current collector plate.

2. The method for manufacturing an electric storage device according to claim 1, wherein in the step of forming the plurality of extension portions, the plurality of extension portions are formed midway along the short side of the electrode foil in the active material uncoated portion.

3. The method for manufacturing an electricity storage device according to claim 1 or 2, wherein in the step of protruding the uncoated active material portions, the electrode foils and the separators are alternately stacked and then spirally wound to form a cylindrical body, and in the step of forming the plurality of extension portions, portions of the cylindrical body on the outer end side in the central axis direction are buckled.

4. The method for manufacturing an electricity storage device according to claim 3, wherein the length l of the portion to be buckled is 5 mm or more.

5. A method for manufacturing an electric storage device according to claim 1 or 2, wherein in the step of protruding the uncoated active material portions, the electrode foils and the separators are alternately stacked and then spirally wound to form a cylindrical body, and in the step of forming the plurality of extension portions, the outer end portion of the cylinder in the central axis direction is compressed in a tapered shape.

6. An electricity storage device comprising: a lamination section having alternately stacked electrode foils and separators, in which at least a portion of an uncoated portion of the electrode foils protrudes beyond an end of the separator in a direction along a short side of the electrode foil; and a current collector plate having an inner surface fixed to the uncoated portion via a weld, wherein the uncoated portion has a plurality of extending portions extending in a direction intersecting the electrode foil so as to cover the separator when viewed from the direction along the short side of the electrode foil, and the inner surface of the current collector plate is fixed via the weld to a portion of the uncoated portion of the electrode foil that is outer than the plurality of extending portions in the direction along the short side of the electrode foil.

7. The electricity storage device according to claim 6, wherein the plurality of extension portions are arranged midway along the short sides of the electrode foil in the active material uncoated portion.

8. The electricity storage device according to claim 6 or 7, wherein the laminated portion forms a spirally wound cylindrical body.

9. The electricity storage device according to claim 8, wherein a portion of the cylindrical body on the outer end side in the central axis direction is formed in a tapered shape.

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