JP2024037418A - Power storage device and method for manufacturing the power storage device - Google Patents

Abstract

An object of the present invention is to provide a power storage device and a method for manufacturing the power storage device that suppresses exposure of a voltage detection line from a seal portion and prevents wrinkles in a current collector. A power storage device 1 includes a current collector 7, a positive electrode active material layer 8, a negative electrode active material layer 9, a frame-shaped first resin part 4a, a frame-shaped second resin part 4b, and a second frame-shaped resin part 4b. The voltage detection wire 6 has a contact portion 6a that is in contact with the second main surface 7b, and the contact portion 6a is covered by the second resin portion 4b that is thermally welded to the second main surface 7b. 6 and a plurality of electrode units 14 are stacked. In the power storage device 1, the thickness of the first resin portion 4a is smaller than the thickness of the second resin portion 4b. [Selection diagram] Figure 1

Description

The present invention relates to a power storage device and a method of manufacturing the power storage device.

As a power storage device, for example, a bipolar secondary battery described in Patent Document 1 is known. The bipolar secondary battery described in Patent Document 1 uses a bipolar electrode, in which a positive electrode layer is formed on one side of a current collector made of rectangular SUS foil and a negative electrode layer is formed on the other side, as a separator. It has a structure in which a plurality of electrolyte layers holding an electrolyte are stacked in between and arranged in series. BACKGROUND ART In a bipolar secondary battery, a single cell layer is formed by a laminated structure in which an electrolyte layer is sandwiched between a positive electrode layer and a negative electrode layer, and a plurality of single cell layers are further laminated to form a battery element.

The current collector has an extending portion that extends further outward than the positive electrode layer and the negative electrode layer. A sealing material is disposed in the extending portion so as to surround the outside of the positive electrode layer and the negative electrode layer. The sealing material insulates the current collectors of adjacent bipolar electrodes from each other. The sealing material is adhered to the current collector.

A lead wire for voltage measurement is provided on one side of the current collector. The tip of this lead wire is glued to the current collector. The tip of the lead wire is covered with a sealing material. The tip of the lead wire is bonded to the current collector after the tip of the lead wire is placed or inserted into the cavity provided in the sealing material, and then the current collector, the tip of the lead wire, and the sealing material are bonded together. This is done by applying pressure to the stacked laminates in the stacking direction.

Japanese Patent Application Publication No. 2008-117626

When covering the lead wire with a sealing material, it is preferable that the thickness of the sealing material is sufficiently large so that the lead wire is not exposed from the sealing material.
On the other hand, thermal welding is a method for joining the sealing material to the current collector. In this case, as the thickness of the sealing material increases, the shrinkage force transmitted to the current collector due to contraction of the sealing material after thermal welding increases, and thus wrinkles are more likely to occur in the current collector.

A power storage device for solving the above problems includes a current collector made of metal foil, a positive electrode active material layer provided on a first main surface of the current collector, and a positive electrode active material layer provided on the first main surface and the current collector. A negative electrode active material layer provided on a second main surface located opposite in the thickness direction of the body, and a negative electrode active material layer heat-welded to the current collector on the first main surface so as to surround the positive electrode active material layer. a frame-shaped resin part that is thermally welded to the current collector on the second main surface so as to surround the negative electrode active material layer; A voltage detection line having a contact portion in contact with one of the main surfaces, the contact portion being covered by one resin portion thermally welded to the one main surface. A power storage device comprising a plurality of laminated electrode units comprising a detection line, the other resin being thermally welded to the one main surface and the other main surface located opposite in the thickness direction of the current collector. The gist is that the thickness of the resin portion is smaller than the thickness of the one resin portion.

In such a configuration, by increasing the thickness of one of the resin parts, it is possible to suppress the voltage detection line from being exposed from the resin part. The thickness of the other resin part is not made the same as the thickness of the one resin part, but is made smaller. Therefore, compared to the case where the thickness of the other resin part is the same as the thickness of one resin part, the shrinkage force transmitted to the current collector due to shrinkage after the other resin part is thermally welded to the current collector. Since the current collector can be made smaller, wrinkles are less likely to occur on the current collector. Therefore, even though the thickness of one of the resin parts is increased in order to prevent the voltage detection line from being exposed from the resin part, the generation of wrinkles in the current collector can be suppressed.

The above power storage device may have a configuration in which a burr protrudes from only the one main surface at an edge of the current collector, and the burr is embedded inside the one resin portion.
In such a configuration, the burr formed on the edge of the current collector is buried inside one resin part that is thicker than the other resin part that is thermally welded to the other main surface of the current collector. Therefore, it is possible to prevent burrs from being exposed from the resin part, and it is also possible to prevent the voltage detection line from being exposed from the resin part.

Regarding the above power storage device, if the direction in which the plurality of electrode units are stacked is defined as the stacking direction, then the one resin part provided in one of the electrode units adjacent to the stacking direction, and the stacking A spacer made of an insulator may be provided between the other resin portion of the other electrode unit of the electrode units adjacent in the direction.

In such a configuration, the spacer can ensure a gap necessary to ensure insulation between the current collectors. Therefore, the thickness of the resin part can be reduced compared to the case where there is no spacer. Since the thickness of the other resin portion can also be reduced, it is possible to further suppress the occurrence of wrinkles in the current collector, and it is also possible to ensure insulation between the current collectors adjacent to each other in the stacking direction.

A method for manufacturing a power storage device to solve the above problems includes a current collector made of metal foil, a positive electrode active material layer provided on a first main surface of the current collector, and a positive electrode active material layer provided on a first main surface of the current collector. Heat is applied to the current collector on the first main surface so as to surround the negative electrode active material layer provided on the second main surface located opposite in the thickness direction of the current collector and the positive electrode active material layer. a frame-shaped resin part that is welded; a frame-shaped resin part that is heat-welded to the current collector on the second main surface so as to surround the negative electrode active material layer; A voltage detection line having a contact portion in contact with one of the second main surfaces, the contact portion being covered by one resin portion thermally welded to the one main surface. A method for manufacturing a power storage device in which a plurality of electrode units are laminated, comprising: a voltage detection line that is connected to the first main surface; A precursor of the resin part that is thermally welded to the other main surface located opposite in the thickness direction of the electric body, the precursor of the other resin part having a smaller thickness than the precursor of the one resin part. and temporarily fix the precursor of the one resin part to the one main surface so as to sandwich the contact part with the one main surface, and the precursor of the other resin part to the other main surface. A temporary fixing step of temporary fixing to the main surface, and heating only from the precursor side of the other resin part to thermally weld the precursor of the one resin part and the precursor of the other resin part to the current collector. The gist is to have a thermal welding step.

In such a manufacturing method, by making the thickness of one precursor larger than the thickness of the other precursor, the voltage detection line is prevented from being exposed from one resin part formed from one precursor. can. Further, in the thermal welding step, since heating is performed only from the other precursor side, the shrinkage force transmitted to the current collector due to contraction after one precursor is thermally welded to the current collector can be reduced. Moreover, the shrinkage force transmitted to the current collector due to shrinkage after the other precursor is thermally welded to the current collector can also be reduced. Therefore, the current collector is less likely to wrinkle.

According to the present invention, while suppressing exposure of the voltage detection line from the seal portion, wrinkles are less likely to occur in the current collector.

FIG. 2 is a cross-sectional view of a power storage device. FIG. 2 is a perspective view of a power storage device. FIG. 3 is a cross-sectional view showing the power storage device from a second resin part. FIG. 3 is a cross-sectional view showing an enlarged voltage detection line. FIG. 3 is a cross-sectional view showing a temporary fixing step in the method for manufacturing a power storage device. FIG. 2 is a cross-sectional view showing a thermal welding step in a method for manufacturing a power storage device. FIG. 7 is a partially enlarged view showing another example of the power storage device.

An embodiment of a power storage device and a method for manufacturing the power storage device will be described below with reference to FIGS. 1 to 6. The power storage device of this embodiment is used, for example, as a battery for various vehicles such as a forklift, a hybrid vehicle, and an electric vehicle.

<Power storage device>
As shown in FIGS. 1 to 4, power storage device 1 is a bipolar battery, and is a lithium ion secondary battery. Note that the power storage device 1 is not limited to a lithium ion secondary battery, and may be a nickel hydride secondary battery, an electric double layer capacitor, or the like.

The power storage device 1 includes a plurality of bipolar electrodes 2, a plurality of separators 3, a positive terminal terminal electrode 23, a negative terminal terminal electrode 24, a plurality of spacers 12, a sealing part 16, a positive terminal conductive plate 21, and a negative terminal conductive plate 21. A plate 22 is provided.

<Bipolar electrode>
Each of the plurality of bipolar electrodes 2 includes a current collector 7, a positive electrode active material layer 8, and a negative electrode active material layer 9. The current collector 7 is made of metal foil. The current collector 7 has a rectangular sheet shape. Further, the direction along the long sides of the current collector 7 is defined as the width direction X, and the direction along the short sides of the current collector 7 is defined as the depth direction Y.

The current collector 7 has a first main surface 7a facing one direction in the thickness direction of the current collector 7, and a second main surface 7b facing the other direction in the thickness direction of the current collector 7. The first main surface 7a and the second main surface 7b are surfaces perpendicular to the thickness direction of the current collector 7. The current collector 7 is constructed by integrating a rectangular sheet-shaped positive electrode current collector 7c and negative electrode current collector 7d. The first principal surface 7a of the current collector 7 is constituted by one surface of the positive electrode current collector 7c, and the second principal surface 7b is constituted by one surface of the negative electrode current collector 7d.

The positive electrode current collector 7c and the negative electrode current collector 7d are chemically inert electrical currents that continue to flow through the positive electrode active material layer 8 and the negative electrode active material layer 9 during discharging or charging of the lithium ion secondary battery. It is a conductor. The material constituting the positive electrode current collector 7c and the negative electrode current collector 7d is a metal material.

The positive electrode current collector 7c and the negative electrode current collector 7d are metal foils. The positive electrode current collector 7c and the negative electrode current collector 7d may be, for example, aluminum foil, copper foil, nickel foil, titanium foil, or stainless steel foil. The positive electrode current collector 7c and the negative electrode current collector 7d may be alloy foils of the above metals. The positive electrode current collector 7c of this embodiment is an aluminum foil. The negative electrode current collector 7d of this embodiment is a copper foil. The integration of the positive electrode current collector 7c and the negative electrode current collector 7d means that the surface of the positive electrode current collector 7c on the opposite side to the first main surface 7a and the negative electrode current collector 7d on the opposite side to the second main surface 7b are integrated. This is done by bonding the surfaces of the

Note that the current collector 7 is not limited to the form in which the positive electrode current collector 7c and the negative electrode current collector 7d are integrated, and may be formed of a single sheet of metal foil (current collector foil). Even when the current collector 7 is formed of a single sheet of metal foil, the material forming the current collector 7 is, for example, aluminum foil, copper foil, nickel foil, titanium foil, or stainless steel foil. In addition, when the current collector 7 is formed of one sheet of metal foil, the surface facing one direction in the thickness direction of the metal foil becomes the first main surface 7a, and the surface facing the other direction in the thickness direction of the metal foil becomes the first main surface 7a. This becomes the second main surface 7b.

The positive electrode active material layer 8 is provided on the first main surface 7 a of the current collector 7 , and the negative electrode active material layer 9 is provided on the second main surface 7 b of the current collector 7 .
In a plan view from the thickness direction of the current collector 7, the positive electrode active material layer 8 is formed in the center of the first main surface 7a of the current collector 7. The peripheral edge of the first main surface 7a of the current collector 7 in plan view is a positive electrode uncoated region 71 where the positive electrode active material layer 8 is not provided. The positive electrode uncoated region 71 is arranged so as to surround the positive electrode active material layer 8 in plan view. In plan view, the negative electrode active material layer 9 is formed in the center of the second main surface 7b of the current collector 7. The peripheral edge of the second main surface 7b of the current collector 7 in plan view is a negative electrode uncoated region 72 where the negative electrode active material layer 9 is not provided. The negative electrode uncoated region 72 is arranged so as to surround the negative electrode active material layer 9 in plan view.

For example, the negative electrode active material layer 9 is formed to be one size larger than the positive electrode active material layer 8. In plan view, the entire region where the positive electrode active material layer 8 is formed is located within the region where the negative electrode active material layer 9 is formed.

The positive electrode active material layer 8 includes a positive electrode active material that can insert and release lithium ions as charge carriers. Examples of the positive electrode active material include polyanionic compounds such as olivine-type lithium iron phosphate (LiFePO ₄ ), lithium composite metal oxides having a layered rock salt structure, and metal oxides having a spinel structure. The positive electrode active material used is one that can be used as a positive electrode active material for lithium ion secondary batteries.

The negative electrode active material layer 9 includes a negative electrode active material that can insert and release charge carriers such as lithium ions. The negative electrode active material is not particularly limited and can be used as long as it is a single substance, alloy, or compound that can insert and release charge carriers such as lithium ions. For example, examples of the negative electrode active material include Li, carbon, a metal compound, an element that can be alloyed with lithium, or a compound thereof. Examples of carbon include natural graphite, artificial graphite, hard carbon (hardly graphitizable carbon), and soft carbon (easily graphitizable carbon). Examples of artificial graphite include highly oriented graphite and mesocarbon microbeads. Examples of elements that can be alloyed with lithium include silicon and tin.

The positive electrode active material layer 8 and the negative electrode active material layer 9 contain a conductive agent, a binder, an electrolyte (a polymer matrix, an ion-conductive polymer, a liquid electrolyte, etc.), and an ion-conductive material to improve electrical conductivity, as necessary. It may contain other components such as an electrolyte supporting salt (lithium salt) to increase the electrolyte. The types of other components contained in the positive electrode active material layer 8 and the negative electrode active material layer 9 and their blending ratio are not particularly limited.

Examples of the conductive aid include acetylene black, carbon black, and graphite. Examples of the binder include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, alkoxysilyl group-containing resins, Examples include acrylic resins such as poly(meth)acrylic acid, styrene-butadiene rubber, carboxymethylcellulose, alginates such as sodium alginate and ammonium alginate, water-soluble cellulose ester crosslinked products, and starch-acrylic acid graft polymers. These binders may be used alone or in combination. As the solvent or dispersion medium, for example, water, N-methyl-2-pyrrolidone, etc. are used.

<Electrode unit>
The electrode unit 14 includes a current collector 7, a positive electrode active material layer 8 provided on a first main surface 7a of the current collector 7, and a negative electrode active material layer 8 provided on a second main surface 7b of the current collector 7. A material layer 9, a first resin portion 4a thermally welded to the current collector 7 on the first main surface 7a, and a second resin portion thermally welded to the current collector 7 on the second main surface 7b. 4b. Further, the electrode unit 14 includes a voltage detection line 6 connected to the current collector 7. Further, the electrode unit 14 includes a resin protruding portion 4c that connects the first resin portion 4a and the second resin portion 4b, which are thermally welded to both sides of the current collector 7, on the outside of the outer edge 7g of the current collector 7. It is equipped with Note that the seal portion 4 is formed by the first resin portion 4a, the second resin portion 4b, and the protruding portion 4c. That is, the electrode unit 14 includes a bipolar electrode 2, a seal portion 4, and a voltage detection line 6.

<Seal part>
The seal portion 4 has a rectangular frame shape when viewed from the thickness direction of the current collector 7. The seal portion 4 is made of resin. The seal portion 4 is formed of, for example, an acid-modified polyolefin-based resin that is mainly composed of a polyolefin-based resin and has an acid-modified group. When viewed from the thickness direction of the current collector 7, the first resin portion 4a has a rectangular frame shape, and the first resin portion 4a is arranged inside the outer edge 7g of the current collector 7. The first resin portion 4a is continuously provided over the entire circumference of the positive electrode uncoated region 71 on the first main surface 7a of the current collector 7. The first resin portion 4 a located in the positive electrode uncoated region 71 is arranged to surround the positive electrode active material layer 8 .

When viewed from the thickness direction of the current collector 7, the second resin portion 4b has a rectangular frame shape and is disposed inside the outer edge 7g of the current collector 7. The second resin portion 4b is continuously provided over the entire circumference of the negative electrode uncoated region 72 on the second main surface 7b of the current collector 7. The second resin portion 4b located in the negative electrode uncoated area 72 is arranged to surround the negative electrode active material layer 9.

As shown in FIG. 4, the dimension of the first resin part 4a in the thickness direction of the current collector 7 is called thickness L1, and the dimension of the second resin part 4b in the thickness direction of the current collector 7 is called thickness L1. It is called L2. The thickness L1 of the first resin part 4a is smaller than the thickness L2 of the second resin part 4b. Therefore, the second resin part 4b is one resin part, and the first resin part 4a is the other resin part. Further, the second main surface 7b is one main surface to which the second resin part 4b is thermally welded, and the first main surface 7a is the other main surface to which the first resin part 4a is thermally welded.

As shown in FIG. 1, the protruding portion 4c is a portion of the seal portion 4 that protrudes from the outer edge 7g. The protruding portion 4c is a portion of the seal portion 4 that does not overlap with the current collector 7 in the thickness direction of the current collector 7.

The protruding portion 4c is arranged so as to surround the current collector 7 when viewed from the thickness direction of the current collector 7, and has a rectangular frame shape. The protruding portion 4c is a portion of the seal portion 4 other than the first resin portion 4a and the second resin portion 4b, and is a portion protruding from the outer edge 7g of the current collector 7. That is, the protruding portion 4c is a portion of the seal portion 4 that extends outward from the outer edge 7g of the current collector 7 from each of the first resin portion 4a and the second resin portion 4b.

<Voltage detection line>
The voltage detection line 6 is a thin plate-like member. The material of the voltage detection line 6 is, for example, a highly conductive material such as copper, aluminum, or stainless steel (SUS).

As shown in FIG. 4, the thickness of the voltage detection line 6 is smaller than the thickness L2 of the second resin portion 4b. The contact portion 6a, which is a part of the voltage detection line 6, is a portion near one end of the voltage detection line 6 in the longitudinal direction. The contact portion 6a is joined to the negative electrode uncoated area 72 of the second main surface 7b of the current collector 7. Thereby, the voltage detection line 6 is electrically connected to the current collector 7. The voltage detection line 6 is used to measure the voltage of the bipolar electrode 2. The contact portion 6a is in contact with the second main surface 7b of the first main surface 7a and the second main surface 7b.

The second resin portion 4b contacts the contact portion 6a from the side opposite to the contact surface with the second main surface 7b of the contact portion 6a, and also contacts the contact portion 6a from both sides of the contact portion 6a in the depth direction Y. are doing. Further, the second resin portion 4b is thermally welded to the second main surface 7b on the side closer to the negative electrode active material layer 9 than the contact portion 6a in the width direction X. Furthermore, as shown in FIG. 1, the portion of the voltage detection line 6 other than the contact portion 6a passes through the protruding portion 4c in the width direction X. A protruding portion 4c is in contact with a portion of the voltage detection line 6 other than the contact portion 6a. Thereby, the contact portion 6a of the voltage detection line 6 is covered with the second resin portion 4b of the seal portion 4. The end of the voltage detection line 6 on the side opposite to the contact portion 6a in the longitudinal direction projects to the outside of the seal portion 4.

As shown in FIG. 4, the thickness of the voltage detection line 6 is preferably smaller than the thickness L2 of the second resin portion 4b. When the thickness L2 of the second resin part 4b is larger than the thickness of the voltage detection line 6, it is preferable that the voltage detection line 6 is exposed from the second resin part 4b in the thickness direction of the current collector 7. is suppressed.

<Electrode group>
As shown in FIG. 1, the electrode group 10 includes a plurality of electrode units 14, a positive terminal electrode 23, and a negative terminal electrode 24. The electrode group 10 includes a plurality of electrode units 14 stacked together with a spacer 12 interposed therebetween, and a positive terminal electrode 23 and a negative terminal electrode 24 stacked on one end and the other end of the plurality of electrode units 14, respectively, with the spacer 12 interposed therebetween. It is formed by Therefore, the electrode group 10 includes a plurality of spacers 12. Note that the direction in which the plurality of electrode units 14, the plurality of spacers 12, the positive terminal electrode 23, and the negative terminal electrode 24 are laminated corresponds to the thickness direction of the current collector 7. The direction in which a plurality of electrode units 14 are stacked with spacers 12 in between is simply referred to as "stacking direction Z."

<Positive terminal electrode and negative terminal electrode>
The positive terminal electrode 23 is located at one end of the electrode group 10 in the stacking direction Z. The negative terminal electrode 24 is located at the other end of the electrode group 10 in the stacking direction Z. The positive terminal electrode 23 includes a current collector 7 and a positive active material layer 8 provided on the first main surface 7a of the current collector 7.

The positive terminal electrode 23 is configured in the same manner as the bipolar electrode 2 except that the negative active material layer 9 is not provided on the second main surface 7b of the current collector 7. Therefore, the positive terminal electrode 23 includes a first resin portion 4a that is thermally welded to the current collector 7 on the first main surface 7a, and a first resin portion 4a that is thermally welded to the current collector 7 on the second main surface 7b. 2 resin part 4b. Furthermore, the positive terminal electrode 23 has a resin protruding part that connects the first resin part 4a and the second resin part 4b, which are thermally welded to both sides of the current collector 7, on the outside of the outer edge 7g of the current collector 7. It is equipped with 4c. In the positive terminal electrode 23, the seal portion 4 is formed by the first resin portion 4a, the second resin portion 4b, and the protruding portion 4c. In addition, the positive terminal electrode 23 includes a voltage detection line 6. The contact portion 6a of the voltage detection line 6 is joined to the negative electrode uncoated area 72 of the second main surface 7b of the current collector 7. The voltage detection line 6 is used to measure the voltage of the positive terminal electrode 23.

The negative terminal electrode 24 includes a current collector 7 and a negative active material layer 9 provided on the second main surface 7b of the current collector 7. The negative terminal electrode 24 is configured in the same manner as the bipolar electrode 2 except that it does not have the positive active material layer 8 on the first main surface 7a of the current collector 7. Therefore, the negative terminal electrode 24 includes a first resin part 4a that is thermally welded to the current collector 7 on the first main surface 7a, and a second resin part 4a that is thermally welded to the current collector 7 on the second main surface 7b. 2 resin part 4b. Furthermore, the negative terminal electrode 24 has a resin protruding part that connects the first resin part 4a and the second resin part 4b, which are thermally welded to both sides of the current collector 7, on the outside of the outer edge 7g of the current collector 7. It is equipped with 4c. In the negative terminal electrode 24, the seal portion 4 is formed by the first resin portion 4a, the second resin portion 4b, and the protruding portion 4c. In addition, the negative terminal electrode 24 includes a voltage detection line 6. The contact portion 6a of the voltage detection line 6 is joined to the negative electrode uncoated area 72 of the second main surface 7b of the current collector 7. The voltage detection line 6 is used to measure the voltage of the negative terminal electrode 24.

Note that the current collector 7 used for the positive terminal electrode 23 and the negative terminal electrode 24 may be formed of a different material, shape, and thickness from the current collector 7 used for the bipolar electrode 2. The second main surface 7b of the current collector 7 of the positive terminal electrode 23 faces one outer side in the stacking direction Z of the electrode group 10. The first main surface 7a of the current collector 7 of the negative terminal electrode 24 faces the other outer side in the stacking direction Z.

<Spacer>
Spacers 12 are arranged between adjacent electrode units 14 in the stacking direction Z, between electrode units 14 and positive terminal electrodes 23 adjacent in the stacking direction Z, and between electrode units 14 and negative terminal electrodes 24 adjacent in the stacking direction Z. is set between. The spacer 12 overlaps the seal portion 4 in the stacking direction Z.

The spacer 12 includes a second resin part 4b, which is one resin part of one of the electrode units 14 adjacent to each other in the stacking direction Z, and a second resin part 4b, which is the other resin part of the other electrode unit 14. 1 resin part 4a. Further, the spacer 12 is arranged between the second resin part 4b of the electrode unit 14 and the first resin part 4a of the positive terminal electrode 23 between the electrode unit 14 and the positive terminal electrode 23 that are adjacent to each other in the stacking direction Z. is provided in between. Further, the spacer 12 is arranged between the first resin part 4a of the electrode unit 14 and the second resin part 4b of the negative terminal electrode 24 between the electrode unit 14 and the negative terminal electrode 24 adjacent to each other in the stacking direction Z. is provided in between.

The spacer 12 has a rectangular frame shape when viewed from the stacking direction Z. The spacer 12 is made of an insulator. Specifically, the spacer 12 is made of resin. The spacer 12 is made of, for example, the same polyolefin resin as the seal portion 4 as a main component, but is formed of an unacid-modified polyolefin resin that does not have an acid-modified group.

The spacer 12 has a first spacer part 12a and a second spacer part 12b. The first spacer portion 12a is formed between adjacent electrode units 14 in the stacking direction Z, with a second resin portion 4b thermally welded to the current collector 7 of one electrode unit 14 and a second resin portion 4b thermally welded to the current collector 7 of the other electrode unit 14. It is provided between the first resin part 4a and the first resin part 4a which is thermally welded. Moreover, the first spacer part 12a has a second resin part 4b thermally welded to the current collector 7 of the electrode unit 14 between the electrode unit 14 and the positive terminal electrode 23 that are adjacent to each other in the stacking direction Z, and a positive terminal terminal The electrode 23 is provided between the electrode 23 and the first resin portion 4a thermally welded to the current collector 7. Further, the first spacer part 12a is arranged between the electrode unit 14 and the negative terminal electrode 24 adjacent to each other in the stacking direction Z, and the first resin part 4a, which is thermally welded to the current collector 7 of the electrode unit 14, and the negative terminal terminal It is provided between the electrode 24 and the second resin part 4b thermally welded to the current collector 7.

Therefore, between the adjacent current collectors 7 in the stacking direction Z, the first spacer portion 12a has a second resin portion 4b thermally welded to one current collector 7 and a second resin portion 4b thermally welded to the other current collector 7. It is provided between the first resin part 4a and the first resin part 4a. Both surfaces of the first spacer portion 12a in the stacking direction Z may be in contact with the first resin portion 4a or the second resin portion 4b, or may be separated from the first resin portion 4a or the second resin portion 4b.

The second resin part 4b is thermally welded to one current collector 7 of adjacent current collectors 7 in the stacking direction Z, the first resin part 4a is thermally welded to the other current collector 7, and the second resin part 4a is thermally welded to the other current collector 7. The first spacer part 12a sandwiched between the resin part 4b and the first resin part 4a is arranged between the negative electrode current collector 7d of one current collector 7 and the negative electrode current collector 7d of the other current collector 7 among the adjacent current collectors 7 in the stacking direction Z. A distance is maintained between the current collector 7 and the positive electrode current collector 7c for insulation. In this way, the first spacer portion 12a, the first resin portion 4a, and the second resin portion 4b suppress short circuit between the positive electrode current collector 7c and the negative electrode current collector 7d.

The second spacer portion 12b is sandwiched between the protruding portions 4c between adjacent electrode units 14 in the stacking direction Z. The second spacer portion 12b is sandwiched between the protruding portion 4c between the electrode unit 14 and the positive terminal electrode 23 that are adjacent to each other in the stacking direction Z, and is also sandwiched between the electrode unit 14 and the negative terminal electrode that are adjacent to each other in the stacking direction Z. 24 and is sandwiched by a protruding portion 4c. The second spacer portion 12b extends from the first spacer portion 12a to the outside of the electrode group 10, and is located so as to surround the first spacer portion 12a. The second spacer portion 12b is a portion of the spacer 12 that extends from the first spacer portion 12a to the outside of the outer edge 7g of the current collector 7.

<Separator>
In the electrode group 10, the electrode units 14 adjacent to each other in the stacking direction Z are such that the negative electrode active material layer 9 of one electrode unit 14 and the positive electrode active material layer 8 of the other electrode unit 14 face each other with the separator 3 in between. It is laminated as shown. Further, in the electrode group 10, the electrode unit 14 and the positive terminal electrode 23 that are adjacent to each other in the stacking direction Z are such that the negative active material layer 9 of the electrode unit 14 and the positive active material layer 8 of the positive terminal electrode 23 overlap the separator 3. They are stacked so as to face each other. In the electrode group 10, the electrode unit 14 and the negative terminal electrode 24 that are adjacent to each other in the stacking direction Z are such that the positive active material layer 8 of the electrode unit 14 and the negative active material layer 9 of the negative terminal electrode 24 are connected to the separator 3. They are stacked so as to face each other.

The separator 3 is arranged between the positive electrode active material layer 8 and the negative electrode active material layer 9. The separator 3 is a member that separates the positive electrode active material layer 8 and the negative electrode active material layer 9 to prevent short circuits due to contact between the two electrodes, and allows charge carriers such as lithium ions to pass through. Therefore, the separator 3 has a larger area than the positive electrode active material layer 8 and the negative electrode active material layer 9, and covers the entire surface thereof. The edge of the separator 3 is fixed to one of the first resin part 4a and the second resin part 4b by heat welding or the like. In this embodiment, the edge of the separator 3 is fixed to the second resin part 4b.

The separator 3 is, for example, a porous sheet or nonwoven fabric containing a polymer that absorbs and retains liquid electrolyte. Examples of the electrolyte impregnated into the separator 3 include a liquid electrolyte containing a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent, or a polymer gel electrolyte containing an electrolyte held in a polymer matrix.

In this embodiment, a liquid electrolyte is used as the electrolyte. As the electrolyte salt of the liquid electrolyte, known lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN(FSO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ and the like can be used. Further, as the nonaqueous solvent, known solvents such as cyclic carbonates, cyclic esters, chain carbonates, chain esters, and ethers can be used. Note that two or more of these known solvent materials may be used in combination. Examples of the material constituting the separator 3 include polypropylene, polyethylene, polyolefin, and polyester. The separator 3 may have a single layer structure or a multilayer structure. The multilayer structure may have, for example, an adhesive layer, a ceramic layer as a heat-resistant layer, etc.

<Voltage detection line in electrode group>
As shown in FIGS. 1, 2, and 3, among two current collectors 7 adjacent to each other in the stacking direction Z, the voltage detection line 6 connected to one current collector 7 is connected to the other current collector 7. The position in the depth direction Y is different from that of the voltage detection line 6 connected to. Therefore, when the electrode group 10 is viewed from the stacking direction Z, the voltage detection line 6 joined to one current collector 7 and the current collector 7 joined to the other current collector 7 are different from each other in the stacking direction. It does not overlap with Z. The voltage detection line 6 connected to one current collector 7 is different from the voltage detection line 6 connected to another current collector 7 with the other current collector 7 in between in the depth direction Y. It's the same.

<Positive current-carrying plate and negative current-carrying plate>
The positive electrode current-carrying plate 21 and the negative electrode current-carrying plate 22 are made of a material with excellent conductivity. As the material constituting the positive electrode current-carrying plate 21 and the negative electrode current-carrying plate 22, for example, metal materials such as aluminum, copper, and stainless steel can be used. The electrode group 10 is arranged between the positive electrode current-carrying plate 21 and the negative electrode current-carrying plate 22 in the stacking direction Z.

The positive current-carrying plate 21 is disposed on the second main surface 7b of the positive terminal electrode 23 and is electrically connected to the current collector 7 of the positive terminal electrode 23. The negative current-carrying plate 22 is disposed on the first main surface 7 a of the negative terminal electrode 24 and is electrically connected to the current collector 7 of the negative terminal electrode 24 . Each of the positive electrode current-carrying plate 21 and the negative electrode current-carrying plate 22 is provided with a terminal (not shown). The power storage device 1 performs charging and discharging through terminals provided on the positive electrode current-carrying plate 21 and the negative electrode current-carrying plate 22. Further, another power storage device 1 may be connected in series or in parallel via the positive electrode current-carrying plate 21 and the negative electrode current-carrying plate 22.

<Sealing part>
The sealing part 16 is arranged so as to surround the positive electrode active material layer 8 and the negative electrode active material layer 9 of the plurality of bipolar electrodes 2, the positive electrode terminal electrode 23, and the negative electrode terminal electrode 24. The sealing portion 16 is formed by welding a portion of the sealing portion 4 and a portion of the spacer 12 that are adjacent to each other in the stacking direction Z to each other. For example, in the seal portion 4 and the spacer 12, a portion of the protruding portion 4c of the seal portion 4 closer to the outer circumferential surface and a portion of the spacer 12 closer to the outer circumferential surface of the second spacer portion 12b are welded. . Examples of the method of welding the seal portion 4 and the spacer 12 to form the seal portion 16 include known welding methods such as contact or non-contact thermal welding and ultrasonic welding. Note that the resins constituting the seal portion 4 and the spacer 12 have the same main component that accounts for 90% by mass of the total weight.

<Internal space>
In the electrode group 10, an internal space S is located between adjacent current collectors 7 in the stacking direction Z. Specifically, the internal space S is between the current collectors 7 of the electrode units 14 adjacent in the stacking direction Z, and between the current collectors 7 of the electrode units 14 and the positive terminal electrode 23 adjacent in the stacking direction Z. It is located between the current collectors 7 of the electrode unit 14 and the negative terminal electrode 24 that are adjacent in the stacking direction Z. More specifically, the internal space S includes a positive electrode current collector 7c and a negative electrode current collector 7d that are adjacent to each other in the stacking direction Z, a first resin part 4a that is thermally welded to the positive electrode current collector 7c, and a negative electrode current collector. It is divided into a second resin part 4b thermally welded to the body 7d, a first spacer part 12a, and a sealing part 16. One internal space S is defined for each set of a positive electrode current collector 7c and a negative electrode current collector 7d that are adjacent to each other in the stacking direction Z. In the internal space S, a positive electrode active material layer 8, a negative electrode active material layer 9, a separator 3, and an electrolyte (not shown) are arranged. In this embodiment, a liquid electrolyte as an example of an electrolyte is arranged in the internal space S. The liquid electrolyte is, for example, a so-called electrolyte solution containing a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.

Sealing portion 16 can suppress moisture from entering internal space S from the outside of power storage device 1 . Sealing portion 16 can suppress leakage of the liquid electrolyte accommodated in internal space S to the outside of power storage device 1 .

<Method for manufacturing power storage device>
Next, a method for manufacturing power storage device 1 will be described. Although the following explanation will be given using the bipolar electrode 2, the positive terminal electrode 23 and the negative terminal electrode 24 are also manufactured in the same manner.

The method for manufacturing power storage device 1 includes a temporary fixing process and a thermal welding process.
As shown in FIG. 5, the temporary fixing process is a process of temporarily fixing the first resin part precursor 17a and the second resin part precursor 17b to the bipolar electrode 2. Each of the first resin part precursor 17a and the second resin part precursor 17b has a rectangular frame shape when viewed from the thickness direction thereof. The first resin portion precursor 17a is temporarily fixed onto the first main surface 7a of the current collector 7. The second resin portion precursor 17b is temporarily fixed onto the second main surface 7b of the current collector 7. The first resin portion precursor 17a is a precursor of the first resin portion 4a that is thermally welded to the first main surface 7a as the other main surface. The second resin portion precursor 17b is a precursor of the second resin portion 4b that is thermally welded to the second main surface 7b as one main surface.

In the temporary fixing step, the first resin part precursor 17a and the second resin part precursor 17b are prepared, the first resin part precursor 17a is temporarily fixed to the first main surface 7a, and the second resin part precursor 17a is temporarily fixed to the first main surface 7a. This is a step of temporarily fixing the second resin portion precursor 17b to the second main surface 7b so as to sandwich the contact portion 6a of the voltage detection line 6 that is in contact with the main surface 7b with the second main surface 7b.

The method for temporarily fixing the first resin part precursor 17a and the second resin part precursor 17b to the current collector 7 is to use an adhesive if the resin part precursors 17a, 17b can be temporarily fixed to the current collector 7. Any method such as adhesion or welding may be used. By performing the temporary fixing step, the current collector 7 is sandwiched between the first resin part precursor 17a and the second resin part precursor 17b from both sides in the thickness direction of the current collector 7. A part of the outer edge side of each of the first resin part precursor 17a and the second resin part precursor 17b protrudes outward beyond the outer edge 7g of the current collector 7.

The thickness of the first resin portion precursor 17a is approximately the same as the thickness L1 of the first resin portion 4a. The first resin portion precursor 17a has a first end surface 171a and a second end surface 172a. The first end surface 171a is one end surface in the thickness direction of the first resin portion precursor 17a, and the second end surface 172a is the other end surface in the thickness direction of the first resin portion precursor 17a. The first resin portion precursor 17a is temporarily fixed to the first main surface 7a so as to surround the positive electrode active material layer 8. The first resin portion precursor 17a is temporarily fixed by joining the first end surface 171a to the first main surface 7a.

The thickness of the second resin portion precursor 17b is approximately the same as the thickness L2 of the second resin portion 4b. Therefore, the thickness of the first resin part precursor 17a is smaller than the thickness of the second resin part precursor 17b. The second resin portion precursor 17b has a first end surface 171b and a second end surface 172b. The first end surface 171b is one end surface in the thickness direction of the second resin portion precursor 17b, and the second end surface 172b is the other end surface in the thickness direction of the second resin portion precursor 17b. The second resin portion precursor 17b is temporarily fixed to the second main surface 7b so as to surround the negative electrode active material layer 9. The second resin portion precursor 17b is temporarily fixed by joining the first end surface 171b to the second main surface 7b.

Before temporarily fixing the second resin portion precursor 17b on the second main surface 7b, the voltage detection line 6 is joined to the second main surface 7b to form a contact portion 6a. The second resin part precursor 17b has a second main surface such that the contact part 6a of the voltage detection line 6 is sandwiched between the second main surface 7b and a part of the first end surface 171b of the second resin part precursor 17b. After being placed on 7b, it is temporarily fixed.

Next, a heat welding process is performed. As shown in FIG. 6, the thermal welding process is a process of thermally welding the first resin part precursor 17a and the second resin part precursor 17b to the current collector 7 of the bipolar electrode 2. Specifically, the thermal welding step is a step of thermally welding the first resin portion precursor 17a and the second resin portion precursor 17b to the current collector 7 by heating only from the first resin portion precursor 17a side. be.

Thermal welding of the first resin part precursor 17a and the second resin part precursor 17b to the current collector 7 may be performed using the sealer 13, for example. The sealer 13 is, for example, an impulse sealer having a heater wire 13a. The sealer 13 has a rectangular frame shape. The sealer 13 has a first sealer portion 131 that contacts the second end surface 172a of the first resin portion precursor 17a, and a second sealer portion 132 that contacts the second end surface 172b of the second resin portion precursor 17b. The sealer 13 has a heater wire 13a in a portion of the first sealer portion 131 that is in contact with the second end surface 172a of the first resin portion precursor 17a.

In the thermal welding process, the sealer 13 is brought into contact with the first resin part precursor 17a and the second resin part precursor 17b from both sides of the current collector 7 in the thickness direction. That is, the first sealer part 131 is brought into contact with the second end surface 172a of the first resin part precursor 17a, and the second sealer part 132 is brought into contact with the second end surface 172b of the second resin part precursor 17b. Therefore, the second end surface 172a of the first resin part precursor 17a temporarily fixed to the first main surface 7a of the current collector 7 and the second resin part temporarily fixed to the second main surface 7b of the current collector 7 The sealer 13 comes into contact with the second end surface 172b of the portion precursor 17b.

In the sealer 13, only the first sealer part 131 in contact with the first resin part precursor 17a is heated by the heater wire 13a, and the first resin part precursor 17a is heated only from the second end surface 172a side. Then, the first resin portion precursor 17a receives heat from the first sealer portion 131 from the second end surface 172a, and the heat is transferred from the second end surface 172a side toward the first end surface 171a. Furthermore, after heat is transferred from the first end surface 171a of the first resin portion precursor 17a to the current collector 7, heat is transferred from the current collector 7 to the first end surface 171b of the second resin portion precursor 17b. The first resin part precursor 17a and the second resin part precursor 17b to which the heat has been transferred thermally expand.

Each of the first resin part precursor 17a and the second resin part precursor 17b is melted at the interface with the current collector 7, and the first resin part precursor 17a is thermally welded to the first main surface 7a. , the second resin portion precursor 17b is thermally welded to the second main surface 7b. Thereafter, when the first resin part precursor 17a is cooled, the first resin part precursor 17a contracts. Moreover, when the second resin part precursor 17b is cooled, the second resin part precursor 17b contracts. As a result, a first resin part 4a located on the first main surface 7a and a second resin part 4b located on the second main surface 7b are formed.

Further, in the first resin part precursor 17a and the second resin part precursor 17b, the portions that protrude outward from the outer edge 7g of the current collector 7 are thermally welded together. In addition, a protruding part 4c is formed in which a peripheral part of the first resin part 4a located on the first main surface 7a is connected to a peripheral part of the second resin part 4b located on the second main surface 7b. be done. As a result, a seal portion 4 is formed. Further, the second resin portion precursor 17b is thermally welded to the negative electrode current collector 7d on the side closer to the negative electrode active material layer 9 than the contact portion 6a of the voltage detection line 6. As a result, electrode unit 14 is formed. Note that when the current collector 7 provided with only the positive electrode active material layer 8 is subjected to the temporary fixing process and the thermal welding process, the positive terminal electrode 23 is formed. Furthermore, when the current collector 7 provided with only the negative electrode active material layer 9 is subjected to a temporary fixing process and a thermal welding process, a negative terminal electrode 24 is formed.

Next, as shown in FIG. 1, the positive terminal electrode 23, the negative terminal electrode 24, the plurality of electrode units 14, the plurality of separators 3, and the plurality of spacers 12 are sequentially stacked in the stacking direction Z. At this time, the separator 3 is interposed between the negative electrode active material layer 9 of one electrode unit 14 and the positive electrode active material layer 8 of the other electrode unit 14 among the electrode units 14 adjacent in the stacking direction Z. Moreover, the separator 3 is interposed between the negative electrode active material layer 9 of the electrode unit 14 disposed at one end in the stacking direction Z among the plurality of electrode units 14 and the positive electrode active material layer 8 of the positive electrode terminal electrode 23 . Furthermore, a separator 3 is interposed between the positive electrode active material layer 8 of the electrode unit 14 disposed at the other end in the stacking direction Z among the plurality of electrode units 14 and the negative electrode active material layer 9 of the negative electrode terminal electrode 24. . Thereby, the electrode group 10 is formed.

The spacer 12 is arranged between the seal portions 4 of adjacent electrode units 14 in the stacking direction Z, between the seal portions 4 of the electrode unit 14 and the positive terminal electrode 23 arranged at one end in the stacking direction Z, and between the seal portions 4 of the electrode units 14 adjacent to each other in the stacking direction Z. It is interposed between the electrode unit 14 disposed at the other end of Z and the seal portion 4 of the negative terminal electrode 24. The spacer 12 is arranged between the seal parts 4 so that the outer peripheral end of the spacer 12 and the outer peripheral end of the seal part 4 overlap. As a result, the protruding portion 4c and the portion of the spacer 12 that will become the second spacer portion 12b are positioned outside the electrode group 10.

Next, the seal portion 4 and the spacer 12 are welded together. Although not shown, the seal portion 4 and the spacer 12 may be welded together by non-contact welding using, for example, a non-contact heater. The non-contact heater is, for example, an infrared heater. In this case, the non-contact heater is opposed to the seal portion 4 and the spacer 12 from the outside of the electrode group 10 while being spaced apart in a direction intersecting the stacking direction Z. A portion of the seal portion 4 and a portion of the spacer 12 are heated and melted by the infrared rays irradiated from the non-contact heater. More specifically, a portion of the protruding portion 4c of the seal portion 4 closer to the outer peripheral surface facing the non-contact heater, and a portion of the second spacer portion 12b of the spacer 12 facing the non-contact heater. A part of the surface is melted.

When the seal portion 4 and the spacer 12 are melted by the non-contact heater, the seal portion 4 and the spacer 12 are welded to each other. More specifically, a portion of the protruding portion 4c of the seal portion 4 that is melted closer to the outer circumferential surface and a portion of the second spacer portion 12b of the spacer 12 that is melted closer to the outer circumferential surface are mutually connected. Weld. Thereby, the spacer 12 is integrated with the seal portion 4 and a seal portion 16 is formed. As a result, power storage device 1 is manufactured.

The functions and effects of this embodiment will be explained below.
(1) In the power storage device 1 of this embodiment, voltage is detected by making the thickness L2 of the second resin part 4b thermally welded to the second main surface 7b larger than the thickness L1 of the first resin part 4a. The wire 6 is prevented from being exposed from the second resin portion 4b. The thickness L1 of the first resin part 4a thermally welded to the first main surface 7a is not made equal to the thickness L2 of the second resin part 4b, but is made smaller. Therefore, compared to the case where the thickness L1 of the first resin part 4a is the same as the thickness L2 of the second resin part 4b, the shrinkage after the first resin part 4a is thermally welded to the current collector 7 Since the contraction force transmitted to the current collector 7 can be reduced, the current collector 7 is less likely to wrinkle. Therefore, even though the thickness L2 of the second resin part 4b is increased in order to prevent the voltage detection line 6 from being exposed from the second resin part 4b, the generation of wrinkles in the current collector 7 can be suppressed.

(2) In the power storage device 1 of this embodiment, the spacer 12 can ensure the gap necessary to ensure the insulation between the current collectors 7. Therefore, compared to the case without the spacer 12, the thickness L1 of the first resin part 4a and the thickness L2 of the second resin part 4b, which are necessary to ensure the insulation between the current collectors 7, can be made smaller. The thickness L1 of the first resin part 4a is smaller than the thickness L2 of the second resin part 4b. Therefore, by providing the spacer 12, the occurrence of wrinkles in the current collector 7 can be further suppressed, and the insulation between the current collectors 7 adjacent to each other in the stacking direction Z can also be ensured.

(3) In the method for manufacturing the power storage device 1 of the present embodiment, the voltage detection line 6 is formed in the second resin part precursor by making the thickness of the second resin part precursor 17b larger than the thickness of the first resin part precursor 17a. Exposure from the body 17b can be suppressed. In the thermal welding process, heating is performed only from the side of the first resin part precursor 17a, which is thinner than the second resin part precursor 17b. Therefore, by reducing the amount of heat input to the second resin part precursor 17b, the shrinkage force transmitted to the current collector 7 due to shrinkage after the second resin part precursor 17b is thermally welded to the current collector 7 is reduced. can. Therefore, since the second resin part precursor 17b, which is thicker than the first resin part precursor 17a, can suppress transmission of large contractile force to the current collector 7, wrinkles in the current collector 7 are less likely to occur.

Note that the above embodiment can be modified and implemented as follows. The above embodiment and the following modification examples can be implemented in combination with each other within a technically consistent range.

○ Of the two current collectors 7 adjacent in the stacking direction Z, the voltage detection line 6 joined to one current collector 7 is in the depth direction Y with respect to the voltage detection line 6 joined to the other current collector 7. However, this is not the case. When the thickness of the positive electrode active material layer 8 and the negative electrode active material layer 9 is sufficiently large and the distance between adjacent current collectors 7 in the stacking direction Z is sufficiently large, there is a possibility that the voltage detection lines 6 will come into contact with each other. Therefore, all the voltage detection lines 6 may be arranged at the same position in the depth direction Y.

As shown in FIG. 7, when the burr 11 protrudes from the outer edge 7g of the current collector 7, it is preferable to thermally weld a thick resin portion to the protruding main surface of the burr 11. For example, the burr 11 protrudes only from the second main surface 7b. The burr 11 protrudes from the outer edge 7g of the current collector 7 when the metal foil material used as the material of the current collector 7 is cut. Here, by setting the cutting direction of the current collector 7 in one direction, the direction in which the burr 11 is formed can be controlled. For example, by changing the cutting direction of the current collector 7 so that the cutting tool is inserted into the current collector 7 from the first main surface 7a side, the burr 11 formed on the edge of the current collector 7 can be It protrudes only toward the second main surface 7b. A second resin portion 4b is thermally welded to the second main surface 7b from which the burr 11 protrudes. The thickness L2 of the second resin part 4b is larger than the thickness L1 of the first resin part 4a welded to the first main surface 7a. Note that the thickness L2 of the second resin portion 4b is set to be sufficiently larger than the maximum projected height of the burr 11. As a result, the burr 11 formed on the edge of the current collector 7 is embedded in the second resin part 4b, which is thicker than the first resin part 4a that is thermally welded to the first main surface 7a of the current collector 7. Therefore, the burr 11 can be prevented from being exposed from the second resin part 4b, and the voltage detection line 6 can also be prevented from being exposed from the second resin part 4b. In addition, when the protrusion height of the burr 11 is sufficiently smaller than the thickness of the first resin portion 4a, the burr 11 may protrude to the first main surface 7a at the outer edge 7g of the current collector 7.

Although the power storage device 1 is provided with the spacer 12 provided between the seal portions 4 adjacent to each other in the stacking direction Z, the present invention is not limited to this. Power storage device 1 does not need to include spacer 12.

○ The voltage detection line 6 may be provided so as to be in contact with the first main surface 7a of the current collector 7. In this case, in the electrode unit 14, the thickness of the first resin part 4a thermally welded to the first main surface 7a is made larger than the thickness of the second resin part 4b thermally welded to the second main surface 7b. . In this case, the thickness of the second resin part 4b heat-welded to the first main surface 7a, which is one main surface, and the second main surface 7b, which is the other main surface located opposite to the first main surface 7a, is the same as that of the first resin part. It becomes smaller than the thickness of 4a.

○ At least one of the first resin part precursor 17a and the second resin part precursor 17b may be divided into each side forming a rectangular frame. In this case, the sealer 13 is also divided into one side each. In the thermal welding step, each of the resin portion precursors 17a and 17b may be thermally welded to the four sides of the current collector 7 one side at a time, or all four sides may be thermally welded together at the same time. Further, after heat-welding each resin part precursor 17a, 17b to two parallel sides of the current collector 7, each resin part precursor 17a, 17b is attached to the remaining two sides. It may be heat welded.

The sealing portion 16 may be formed by welding the first resin portion 4a or the second resin portion 4b of the seal portion 4 to the first spacer portion 12a of the spacer 12.
○ At least one of the positive terminal electrode 23 and the negative terminal electrode 24 does not need to be provided with the voltage detection line 6.

Although the spacer 12 is made of insulating resin, it may be made of an insulator other than resin.

DESCRIPTION OF SYMBOLS 1... Power storage device, 4a... First resin part, 4b... Second resin part, 6... Voltage detection line, 6a... Contact part, 7... Current collector, 7a... First main surface, 7b... Second main surface, 8... Positive electrode active material layer, 9... Negative electrode active material layer, 11... Burr, 12... Spacer, 14... Electrode unit, 17a... First resin part precursor as a precursor, 17b... Second resin part as a precursor precursor.

Claims (4)

A current collector that is a metal foil,
a positive electrode active material layer provided on the first main surface of the current collector;
a negative electrode active material layer provided on a second main surface opposite to the first main surface in the thickness direction of the current collector;
a frame-shaped resin part that is thermally welded to the current collector on the first main surface so as to surround the positive electrode active material layer;
a frame-shaped resin part that is thermally welded to the current collector on the second main surface so as to surround the negative electrode active material layer;
A voltage detection line having a contact portion that is in contact with one of the first and second main surfaces, the voltage detection line being formed by one resin portion that is thermally welded to the one main surface. A power storage device including a plurality of laminated electrode units including a voltage detection line with the contact portion covered,
The thickness of the other resin part that is thermally welded to the one main surface and the other main surface located opposite in the thickness direction of the current collector is smaller than the thickness of the one resin part. Characteristic power storage device. The power storage device according to claim 1, wherein at an edge of the current collector, a burr protrudes from only the one main surface, and the burr is embedded inside the one resin portion. If the direction in which the plurality of electrode units are stacked is defined as the stacking direction, one of the electrode units adjacent to each other in the stacking direction includes one resin portion and the electrode adjacent to the stacking direction. The power storage device according to claim 1 or 2, wherein an insulating spacer is provided between the other electrode unit and the other resin portion of the unit. A current collector that is a metal foil,
a positive electrode active material layer provided on the first main surface of the current collector;
a negative electrode active material layer provided on a second main surface opposite to the first main surface in the thickness direction of the current collector;
a frame-shaped resin part that is thermally welded to the current collector on the first main surface so as to surround the positive electrode active material layer;
a frame-shaped resin part that is thermally welded to the current collector on the second main surface so as to surround the negative electrode active material layer;
A voltage detection line having a contact portion that is in contact with one of the first and second main surfaces, the voltage detection line being formed by one resin portion that is thermally welded to the one main surface. A method for manufacturing a power storage device in which a plurality of electrode units are stacked, the voltage detection line having the contact portion covered,
a precursor of the resin portion that is thermally welded to the one main surface; and a precursor of the resin portion that is thermally welded to the other main surface that is opposite to the one main surface in the thickness direction of the current collector. A precursor of the other resin part having a smaller thickness than the precursor of the one resin part is prepared, and a precursor of the one resin part is prepared so as to sandwich the contact part with the main surface of the one resin part. a temporary fixing step of temporarily fixing a precursor to the one main surface, and temporarily fixing a precursor of the other resin part to the other main surface;
A thermal welding step of thermally welding the precursor of the one resin portion and the precursor of the other resin portion to the current collector by heating only from the precursor side of the other resin portion. A method for manufacturing a power storage device.

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