Battery and battery unit

Abstract

A battery 1 comprises: an electrode assembly 10 that has a positive electrode mixture layer 11a, a negative electrode mixture layer 11b, and a first current collector 12; and a second current collector 20 that accommodates the electrode assembly 10 and that is electrically connected to the positive electrode mixture layer 11a. The second current collector 20 has a shape obtained by bending one sheet member SH which has a first opening 23. The first current collector 12 is provided with a body part 12a that is electrically connected to the negative electrode mixture layer 11b inside the second current collector 20 and a protruding part 12b that protrudes from the body part 12a, that passes through the first opening 23, and that is exposed from the second current collector 20.

Description

Batteries and battery units

[0001] The present disclosure relates to batteries and battery units.

[0002] Patent Document 1 discloses a sheet-type secondary battery as an example of a battery. The battery in Patent Document 1 includes an internal electrode having a positive electrode and a negative electrode, an exterior body that houses the internal electrode, a first external lead, and a second external lead. The first external lead is attached to the outer surface of the exterior body by a first connecting means and electrically connected to the positive electrode. The second external lead is attached to the outer surface of the exterior body by a second connecting means and electrically connected to the negative electrode.

[0003] Patent No. 6893575

[0004] In the battery of Patent Document 1, the external lead and the internal electrode (electrode assembly) are electrically connected via the above-mentioned connection means that penetrates the exterior member and the internal lead inside the exterior member, etc. The size of the internal electrode (electrode assembly) relative to the size of the exterior member is limited by the connection means and the internal lead, etc. On the other hand, there is a demand for increasing the size of the electrode assembly relative to the size of the exterior member, thereby increasing the battery capacity (so-called energy density) relative to the size of the exterior member.

[0005] The present disclosure has been made in view of the above, and has an object to provide a battery and a battery unit that can increase the battery capacity relative to the size of the exterior member.

[0006] The battery of the present disclosure comprises an electrode assembly having a first electrode, a second electrode having a different potential from the first electrode, and a current collector, and an exterior member that houses the electrode assembly and is electrically connected to the first electrode, the exterior member having a shape formed by folding a single sheet member having an opening, and the current collector comprising a main body portion that is electrically connected to the second electrode inside the exterior member, and a protrusion portion that protrudes from the main body portion, penetrates the opening, and is exposed from the exterior member.

[0007] The battery of the present disclosure also comprises an electrode assembly having a first electrode, a second electrode having a different potential from the first electrode, and a current collector, and an exterior member that houses the electrode assembly and is in contact with the first electrode, wherein the exterior member has a shape formed by folding a single sheet member having an opening, and the current collector comprises a main body portion that is in contact with the second electrode inside the exterior member, and a protrusion portion that protrudes from the main body portion, penetrates the opening, and is exposed from the exterior member.

[0008] The battery unit of the present disclosure includes two of the above-described batteries, and the two batteries are stacked in a state where the exterior members of the two batteries are in contact with each other.

[0009] According to the battery and battery unit of the present disclosure, it is possible to increase the battery capacity relative to the size of the exterior member.

[0010] FIG. 1 is a plan view of a battery according to an embodiment of the present disclosure. FIG. 2 is a side view of the battery shown in FIG. 1. FIG. 3 is a cross-sectional view of the battery taken along line III-III shown in FIG. 1. FIG. 4 is a plan view of an electrode assembly. FIG. 5 is a cross-sectional view of the battery taken along line V-V shown in FIG. 1. FIG. 6 is a plan view of a sheet member before a second current collector is formed. FIG. 7 is a view showing a first opening provided in a battery according to a first modified embodiment of the present disclosure. FIG. 8 is a view showing a first opening provided in a battery according to a second modified embodiment of the present disclosure. FIG. 9 is a plan view of a resin member used in the manufacturing process of a battery according to a third modified embodiment of the present disclosure. FIG. 10 is a cross-sectional view of the resin member taken along line X-X shown in FIG. 9. FIG. 11 is a plan view of a sheet member before a second current collector is formed in a battery according to a fourth modified embodiment of the present disclosure. FIG. 12 is a plan view of a battery according to a fifth modified embodiment of the present disclosure. FIG. 13 is a cross-sectional view of the battery taken along line XIII-XIII shown in FIG. 12. Fig. 14 is a plan view of the sheet member before the second current collector shown in Fig. 13 is formed. Fig. 15 is a cross-sectional view of a battery according to a sixth modified example of the embodiment of the present disclosure. Fig. 16 is a cross-sectional view of a battery unit according to an embodiment of the present disclosure. Fig. 17 is a cross-sectional view of a battery unit according to a modified example of the embodiment of the present disclosure.

[0011] Hereinafter, embodiments will be described in detail with reference to the drawings. Note that the present disclosure is not limited to these embodiments. Each embodiment is an example, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible.

[0012] The X direction shown in the drawings corresponds to the width direction of the battery 1, the Y direction corresponds to the depth direction of the battery 1, and the Z direction corresponds to the height direction of the battery 1. The X, Y, and Z directions are perpendicular to one another. In the X direction, the side indicated by the arrow is the +X side, and the side opposite the +X side is the -X side. In the Y direction, the side indicated by the arrow is the +Y side, and the side opposite the +Y side is the -Y side. In the Z direction, the side indicated by the arrow is the +Z side, and the side opposite the +Z side is the -Z side. Note that the X, Y, and Z directions are merely examples, and the present disclosure is not limited to these directions. In this specification, "planar view" refers to viewing an object along the Z direction.

[0013] Fig. 1 is a plan view of a battery 1 according to an embodiment of the present disclosure. Fig. 2 is a side view of the battery 1 shown in Fig. 1. Fig. 3 is a cross-sectional view of the battery 1 taken along line III-III shown in Fig. 1.

[0014] The battery 1 is a secondary battery. The battery 1 is, for example, a lithium battery. The battery 1 has a flat shape. The battery 1 includes an electrode assembly 10.

[0015] Fig. 4 is a plan view of the electrode assembly 10. As shown in Figs. 3 and 4, the electrode assembly 10 includes two electrode bodies 11 and a first current collector 12 (corresponding to a "current collector"). The electrode bodies 11 and the first current collector 12 are each sheet-shaped.

[0016] The electrode body 11 includes a positive electrode composite layer 11a (corresponding to a "first electrode"), a negative electrode composite layer 11b (corresponding to a "second electrode") that has a different potential from the positive electrode composite layer 11a, and a separator 11c. The positive electrode composite layer 11a, the negative electrode composite layer 11b, and the separator 11c are each in the form of a rectangular sheet in a plan view. The positive electrode composite layer 11a and the negative electrode composite layer 11b are stacked with the separator 11c interposed between them. The two electrode bodies 11 are arranged on opposite sides of the first current collector 12.

[0017] The positive electrode composite layer 11a contains a lithium-containing composite oxide (e.g., lithium cobalt oxide, lithium nickel oxide, lithium iron phosphate, etc.). The positive electrode composite layer 11a may also contain a ternary positive electrode material (e.g., NMC, NCA, etc.). The negative electrode composite layer 11b contains lithium titanate. The negative electrode composite layer 11b may also contain silicon oxide and graphite, or a mixture of silicon oxide and graphite.

[0018] The first current collector 12 is electrically conductive. The first current collector 12 is made of copper. The first current collector 12 integrally has a main body 12a and a protruding portion 12b. The main body 12a is a rectangular sheet in plan view. The main body 12a is electrically connected to the negative electrode composite material layer 11b. Specifically, the main body 12a is sandwiched between the two electrode bodies 11, and the negative electrode composite material layers 11b of the two electrode bodies 11 come into contact with each other and are electrically connected.

[0019] Protruding portion 12b has a strip shape protruding from main body portion 12a and functions as a negative electrode terminal that is electrically connected to negative electrode composite material layer 11b.

[0020] The battery 1 further includes a second current collector 20 (corresponding to an "exterior member").

[0021] The second current collector 20 houses the electrode assembly 10. Specifically, the two electrode bodies 11 and the main body 12a are disposed inside the second current collector 20. The protruding portion 12b penetrates a first opening 23 (described below) of the second current collector 20 and is exposed from the second current collector 20. In other words, the protruding portion 12b protrudes to the outside of the second current collector 20. The second current collector 20 houses an electrolyte solution. In this way, the second current collector 20 functions as an exterior member of the battery 1.

[0022] 1, 2, and 3, the second current collector 20 has a rectangular shape in a plan view. Specifically, the periphery of the second current collector 20 has a rectangular shape in a plan view, and has a first side S1, a second side S2, a third side S3, and a fourth side S4. It goes without saying that the shape of the second current collector 20 is not limited to a rectangular shape in a plan view, and the periphery of the second current collector 20 may have any shape as long as it has at least the first side S1 in a plan view.

[0023] The second current collector 20 is electrically conductive. The second current collector 20 is made of, for example, aluminum. The second current collector 20 has a shape in which a single sheet member SH is folded. The second current collector 20 has a folded portion B formed by folding the sheet member SH.

[0024] The bent portion B corresponds to the first side S1. That is, the bent portion B extends along the Y direction. The bent portion B corresponds to the range in which the battery 1 is visible in a side view of the battery 1 shown in FIG. 2 , viewed from the first side S1 along a direction (X direction) perpendicular to both the first side S1 and the thickness direction of the battery 1.

[0025] Furthermore, in a plan view of the second current collector 20, the peripheral portions of the folded sheet members SH come into contact with and overlap each other at portions of the peripheral portion of the second current collector 20 that correspond to the second side S2, the third side S3, and the fourth side S4. The overlapping portions of the sheet members SH are joined by, for example, laser welding.

[0026] The two-dot chain line in FIG. 1 indicates the position of the joint portion J of the second current collector 20. The position of the joint portion J is located outside the electrode body 11 and the main body portion 12a of the first current collector 12 in a plan view of the battery 1. Furthermore, as described above, the first side S1 corresponds to the folded portion B. Therefore, in a plan view of the second current collector 20, the entire peripheral portion of the second current collector 20 is sealed. This prevents the electrolyte from leaking from the peripheral portion of the second current collector 20. Furthermore, the joint portion J formed by laser welding is conductive.

[0027] Joining by laser welding can reduce the width of the joint J compared to joining using an adhesive member, for example. Therefore, in the case of joining by laser welding, the internal volume of the second current collector 20 and the volume of the electrode body 11 can be increased compared to joining using an adhesive member. Therefore, the battery capacity (so-called energy density) relative to the size of the second current collector 20 that functions as an exterior member can be increased.

[0028] 3, second current collector 20 is in contact with and electrically connected to each of positive electrode composite layers 11a of two electrode assemblies 10. That is, second current collector 20 functions as a positive electrode terminal.

[0029] 1, 2, and 3, the outer surface of the second current collector 20 includes a first main surface 21 and a second main surface 22. The first main surface 21 and the second main surface 22 are flat. The first main surface 21 and the second main surface 22 may include protrusions and recesses, or may be curved.

[0030] The first main surface 21 and the second main surface 22 are located on opposite sides of the electrode assembly 10. Specifically, the first main surface 21 and the second main surface 22 face opposite sides in the Z direction. The plan view of the first main surface 21 is the same as the plan view of the battery 1.

[0031] Fig. 5 is a cross-sectional view of the battery 1 taken along line VV shown in Fig. 1. As shown in Figs. 2, 3, and 5, the second current collector 20 has a first opening 23 (corresponding to "opening") and a second opening 24.

[0032] The first opening 23 and the second opening 24 are located at the bent portion B. The protruding portion 12b of the first current collector 12 passes through the first opening 23. The first opening 23 and the second opening 24 have a shape that extends along the direction in which the bent portion B extends (Y direction). In other words, the longitudinal direction of the first opening 23 and the second opening 24 is the same as the direction in which the bent portion B extends (Y direction). The first opening 23 and the second opening 24 are spaced apart from the joint portion J.

[0033] Furthermore, both longitudinal ends of the peripheries of the first opening 23 and the second opening 24 are arc-shaped, which prevents the second current collector 20 from tearing at the first opening 23 and the second opening 24.

[0034] 1, 2, 3, and 5, the battery 1 further includes a first insulating member 30 (corresponding to the "insulating member") and a second insulating member 40. The first insulating member 30 and the second insulating member 40 are made of a thermoplastic resin having electrical insulating properties.

[0035] The first insulating member 30 is disposed between the protruding portion 12b and the second current collector 20, and electrically insulates the protruding portion 12b from the second current collector 20. The first insulating member 30 also seals the first opening 23. Specifically, the first insulating member 30 is joined to the periphery of the first opening 23 on the inside of the second current collector 20. The protruding portion 12b penetrates the first insulating member 30, and the protruding portion 12b and the first insulating member 30 are joined together. This prevents the electrolyte from leaking from the first opening 23. The first insulating member 30, the second current collector 20, and the protruding portion 12b are joined together by thermal welding.

[0036] The second insulating member 40 seals the second opening 24. Specifically, the second insulating member 40 is joined to the periphery of the second opening 24 on the inside of the second current collector 20. This prevents the electrolyte from leaking from the second opening 24. The second insulating member 40 and the second current collector 20 are joined by thermal welding.

[0037] As described above, when the protrusion 12b functions as the negative electrode terminal and the second current collector 20 functions as the positive electrode terminal, the battery 1 does not include a connecting member that electrically connects the positive electrode composite layer 11a to the positive electrode terminal and a connecting member that electrically connects the negative electrode composite layer 11b to the negative electrode terminal, as compared to when separate members are used for the positive electrode terminal and the negative electrode terminal. This reduces the number of parts in the battery 1, thereby reducing the cost of the battery 1. Furthermore, because the connecting member is not located inside the second current collector 20, the electrode body 11 can be made larger. This allows the battery capacity (so-called energy density) to be increased relative to the size of the second current collector 20, which functions as an exterior member.

[0038] Furthermore, as described above, the battery 1 has the first main surface 21 and the second main surface 22. Therefore, stacking multiple batteries 1 allows the multiple batteries 1 to be easily electrically connected in parallel. Specifically, the first main surface 21 of one battery 1 and the second main surface 22 of the other battery 1 come into contact with each other, allowing the two batteries 1 to be easily electrically connected in parallel.

[0039] Next, the process of forming the second current collector 20 and the process of housing the electrode assembly 10 in the second current collector 20 in the manufacturing process of the battery 1 will be described.

[0040] 6 is a plan view of the sheet member SH before the second current collector 20 is formed. The first direction D1 and the second direction D2 shown in FIG. 6 correspond to the longitudinal and lateral directions of the sheet member SH, and correspond to the X and Y directions of the battery 1.

[0041] First, the first opening 23 and the second opening 24 are formed in the sheet member SH by press working or the like. The first opening 23 and the second opening 24 are formed in the center of the sheet member SH in the first direction D1 so as to extend along the second direction D2. Next, the resin members R1 are arranged on both sides of each of the first opening 23 and the second opening 24 in the first direction D1.

[0042] Next, in the electrode assembly 10 shown in Fig. 4, a second resin member R2 is disposed so as to surround the base end portion of the protruding portion 12b. Furthermore, the protruding portion 12b is passed through a first opening 23 of the sheet member SH shown in Fig. 6. The sheet member SH is then folded, and the peripheral edges of the sheet member SH are joined by laser welding, thereby forming the second current collector 20 shown in Figs. 1, 2, and 3. At this time, the joining portion J shown in Fig. 1 is separated from the resin member R1 and the second resin member R2, and the resin member R1 and the second resin member R2 do not melt.

[0043] Furthermore, the electrolyte is injected into the second current collector 20 through the second opening 24. Subsequently, the electrode assembly 10 is charged and discharged, and gas generated from the electrode assembly 10 is released through the second opening 24.

[0044] Next, with the two resin members R1 and the second resin member R2 around the first opening 23 in contact with each other, the two resin members R1 and the second resin member R2 are thermally welded to the second current collector 20. At this time, the two resin members R1 and the second resin member R2 fuse together to form the first insulating member 30, sealing the first opening 23. Note that the two resin members R1 may also fuse together through direct contact.

[0045] As described above, two resin members R1 are arranged on both sides of the first opening 23, and the second resin member R2 is arranged around the protrusion 12b, so that the first opening 23 can be reliably sealed even when the protrusion 12b penetrates the first opening 23.

[0046] Furthermore, when the second resin member R2 is disposed around the protruding portion 12 b as described above, the distance between the second current collector 20 and the protruding portion 12 b can be made larger than when the second resin member R2 is not disposed around the protruding portion 12 b, and contact between the second current collector 20 and the protruding portion 12 b is suppressed during thermal welding. Note that the thermal welding to seal the first opening 23 may be performed before the electrolyte solution is injected inside the second current collector 20.

[0047] Furthermore, with the two resin members R1 around the second opening 24 in contact with each other, the two resin members R1 are thermally welded to the second current collector 20. At this time, the two resin members R1 are fused together to form the second insulating member 40, and the second opening 24 is sealed.

[0048] As described above, the two resin members R1 are disposed on both sides of the second opening 24, thereby reliably sealing the second opening 24. Note that the heat welding for sealing the first opening 23 and the heat welding for sealing the second opening 24 may be performed simultaneously.

[0049] Next, a battery 1 according to a modification of the above embodiment will be described, focusing mainly on the differences from the battery 1 of the above embodiment.

[0050] For example, the electrode body 11 may be configured so that the positive electrode composite layer 11a is electrically connected to the first current collector 12 and the negative electrode composite layer 11b is electrically connected to the second current collector 20. In this case, the negative electrode composite layer 11b corresponds to the "first electrode" and the positive electrode composite layer 11a corresponds to the "second electrode." In this case, the second current collector 20 functions as the negative electrode terminal and the protrusion 12b functions as the positive electrode terminal. In this case, the material of the first current collector 12 may be aluminum, and the material of the second current collector 20 may be copper.

[0051] Furthermore, the first opening 23 and the second opening 24 may be located in a portion of the second current collector 20 other than the bent portion B.

[0052] Furthermore, the second current collector 20 does not have to include the second opening 24. In this case, the battery 1 does not include the second insulating member 40. In this case, the electrolyte is injected into the second current collector 20 through the first opening 23 during the manufacturing process of the battery 1, and gas generated from the electrode assembly 10 is released through the first opening 23.

[0053] 7 is a diagram showing the first opening 123 provided in the battery 1 according to a first modification of the embodiment of the present disclosure. In this first modification, the first opening 123 has a notch shape. When the first opening 123 has a notch shape, the opening area of ​​the first opening 123 can be made relatively small. Therefore, the first insulating member 30 can easily seal the first opening 123. Note that the second opening 24 may also have a notch shape.

[0054] 8 is a diagram showing a first opening 223 provided in a battery 1 according to a second modification of the embodiment of the present disclosure. In this second modification, the first opening 223 has a notch shape. Furthermore, both longitudinal ends of the first opening 223 are circular. This prevents the second current collector 20 from tearing at both longitudinal ends of the first opening 223. Note that the second opening 24 may have a notch shape and both longitudinal ends of the second opening 24 may be circular.

[0055] Fig. 9 is a plan view of a resin member R1 used in the manufacturing process of a battery 1 according to a third modified example of the embodiment of the present disclosure. Fig. 10 is a cross-sectional view of the resin member R1 taken along line XX shown in Fig. 9.

[0056] In the third modified example, one resin member R31 is disposed for each first opening 23. When disposed on the sheet member SH, the resin member R31 has an annular shape that surrounds the first opening 23 in a plan view of the sheet member SH. In other words, the resin member R31 has a through hole R31a that overlaps with the first opening 23 in a plan view of the sheet member SH.

[0057] The resin member R31 also has a groove R31b that overlaps the first opening 23 in a plan view of the sheet member SH and extends along the longitudinal direction of the first opening 23. The through hole R31a is located at the bottom of the groove R31b. The resin member R31 has the groove R31b, which allows the sheet member SH to be easily folded. The resin member R31 may also be disposed around the second opening 24 of the sheet member SH.

[0058] FIG. 11 is a plan view of the sheet member SH before the second current collector 20 is formed, which is included in the battery 1 according to the fourth modified example of the embodiment of the present disclosure.

[0059] In the fourth modified example, one resin member R41 is disposed in each of the first opening 23 and the second opening 24 of the sheet member SH. The resin member R41 has an annular shape in a plan view of the sheet member SH, and is disposed so that the first opening 23 or the second opening 24 is located inside the resin member R41.

[0060] Fig. 12 is a plan view of a battery 1 according to a fifth modified example of the embodiment of the present disclosure. Fig. 13 is a cross-sectional view of the battery 1 taken along line XIII-XIII shown in Fig. 12. Fig. 14 is a plan view of the sheet member SH before the second current collector 20 shown in Fig. 13 is formed.

[0061] The battery 1 of the fifth modified example does not include the second resin member R2. One resin member R51 is disposed in each of the first opening 23 and the second opening 24 of the sheet member SH. Furthermore, as shown in FIG. 13 , the resin member R51 is annular in plan view of the sheet member SH.

[0062] In addition, in a plan view of the sheet member SH, the peripheries of the first opening 23 and the second opening 24 are respectively located between the inner peripheral edge and the outer peripheral edge of the resin member R51. As a result, as shown in FIGS. 12 and 13 , when the resin member R51 and the second current collector 20 are thermally welded together, the first insulating member 530 formed by the resin member R51 is exposed outside the second current collector 20 beyond the first opening 23. This further prevents electrical connection between the second current collector 20 and the protrusion 12 b. Similarly to the first insulating member 530, the second insulating member 540 formed by the resin member R51 is exposed outside the second current collector 20 beyond the second opening 24.

[0063] 15 is a cross-sectional view of a battery 1 according to a sixth modification of the embodiment of the present disclosure. The battery 1 of the sixth modification further includes a third current collector 650 and a fourth current collector 660. The third current collector 650 and the fourth current collector 660 are electrically conductive.

[0064] Third current collector 650 is sandwiched between positive electrode composite layer 11 a and the inner surface of second current collector 20, and is electrically connected in contact with positive electrode composite layer 11 a and the inner surface of second current collector 20. Fourth current collector 660 is sandwiched between negative electrode composite layer 11 b and main body portion 12 a of first current collector 12, and is electrically connected in contact with negative electrode composite layer 11 b and main body portion 12 a.

[0065] 16 is a cross-sectional view of a battery unit 2 according to an embodiment of the present disclosure. The battery unit 2 includes a plurality of batteries 1.

[0066] The battery 1 is configured similarly to the battery 1 in the above embodiment. The battery unit 2 includes three batteries 1. Specifically, the battery unit 2 includes a first battery 1a, a second battery 1b, and a third battery 1c. Note that the electrode body 11 is omitted from the battery 1 shown in FIG. 11 . Hereinafter, when the first battery 1a, the second battery 1b, and the third battery 1c are described without distinction, they will be simply referred to as "batteries 1."

[0067] The number of batteries 1 included in the battery unit 2 is three, but it goes without saying that this is not limited to three. The number of batteries 1 included in the battery unit 2 is two or more. In other words, the battery unit 2 includes two batteries 1.

[0068] The first battery 1a, the second battery 1b, and the third battery 1c are stacked so as to be electrically connected in parallel. The second main surface 22 of the first battery 1a and the first main surface 21 of the second battery 1b are in contact with each other and electrically connected. Furthermore, the second main surface 22 of the second battery 1b and the first main surface 21 of the third battery 1c are in contact with each other and electrically connected.

[0069] In the battery unit 2, the plurality of batteries 1 are simply electrically connected in parallel without using any additional components, thereby enabling the battery unit 2 to be made smaller.

[0070] In addition, in two batteries 1 that contact each other, two second current collectors 20 are stacked between two electrode assemblies 10. This allows the thickness of the second current collectors 20 to be increased.

[0071] Furthermore, heat from the electrode assembly 10 is transferred to the second current collector 20 and dissipated to the outside. That is, in the battery unit 2, the second current collector 20 is disposed between the two electrode assemblies 10 and has a heat dissipation function of dissipating heat from the electrode assemblies 10. In this case, the temperature rise of the electrode assembly 10 can be suppressed compared to when a plurality of electrode assemblies 10 are housed in a single second current collector 20 while being stacked in contact with each other.

[0072] Next, a battery unit 2 according to a modification of the above embodiment will be described, focusing mainly on the differences from the battery unit 2 of the above embodiment.

[0073] 17 is a cross-sectional view of a battery unit 2 according to a modified example of the embodiment of the present disclosure. In the battery 1 shown in FIG. 17, the electrode body 11 is also omitted.

[0074] The battery unit 2 of this modified example further includes a plurality of insulating plates 770. The insulating plates 770 have electrical insulation properties. The insulating plates 770 are formed of, for example, electrically insulating resin or paper. The insulating plates 770 are arranged on the first main surface 21.

[0075] The insulating plate 770 is sandwiched between two adjacent batteries 1. Specifically, the insulating plate 770 is located between the first battery 1a and the second battery 1b, and between the second battery 1b and the third battery 1c. In this modification, the number of insulating plates 770 is two, but it goes without saying that this is not limited to two and will vary depending on the number of batteries 1 included in the battery unit 2.

[0076] Furthermore, in this modification, the tip of the protrusion 712b is located on the opposite side of the insulating plate 770 from the first main surface 21. The tip of the protrusion 712b overlaps the first main surface 21 and the second main surface 22 in a plan view of the battery 1. As a result, the tip of the protrusion 712b of the third battery 1c is in contact with and electrically connected to the second main surface 22 of the second battery 1b. Furthermore, the tip of the protrusion 712b of the second battery 1b is in contact with and electrically connected to the second main surface 22 of the first battery 1a. In this way, in the battery unit 2 of this modification, the three batteries 1 are electrically connected in series.

[0077] The present disclosure may also be implemented as a combination of the following configurations.

[0078] (1) A battery comprising: an electrode assembly having a first electrode, a second electrode having a potential different from that of the first electrode, and a current collector; and an exterior member that houses the electrode assembly and is electrically connected to the first electrode, wherein the exterior member is shaped by folding a single sheet member having an opening, and the current collector comprises: a main body portion that is electrically connected to the second electrode inside the exterior member; and a protrusion portion that protrudes from the main body portion, penetrates the opening, and is exposed from the exterior member.

[0079] (2) The battery according to (1), wherein the exterior member has a first main surface and a second main surface that are planar and located on opposite sides of the electrode assembly.

[0080] (3) The battery according to (1) or (2), wherein the exterior member has a bent portion where the sheet member is bent, and the opening is located at the bent portion.

[0081] (4) The battery according to any one of (1) to (3), further comprising an insulating member disposed between the exterior member and the protruding portion and sealing the opening.

[0082] (5) The battery according to any one of (1) to (4), wherein the exterior member has a joint portion where the overlapping portions of the sheet member are joined, and the joint portion is spaced apart from the opening.

[0083] (6) A battery comprising: an electrode assembly having a first electrode, a second electrode having a potential different from that of the first electrode, and a current collector; and an exterior member that houses the electrode assembly and is in contact with the first electrode, wherein the exterior member is shaped by folding a single sheet member having an opening, and the current collector comprises: a main body that is in contact with the second electrode inside the exterior member; and a protrusion that protrudes from the main body, penetrates the opening, and is exposed from the exterior member.

[0084] (7) A battery unit including two batteries according to any one of (1) to (6), wherein the two batteries are stacked in a state in which the exterior members of the two batteries are in contact with each other.

[0085] REFERENCE SIGNS LIST 1 Battery 2 Battery unit 10 Electrode assembly 11a Positive electrode composite layer (first electrode) 11b Negative electrode composite layer (second electrode) 11c Separator 12 First current collector (current collector) 12a Main body 12b Protrusion 20 Second current collector (exterior member) 21 First main surface 22 Second main surface 23 First opening (opening) 24 Second opening 30 First insulating member (insulating member) 40 Second insulating member B Folded portion J Joined portion SH Sheet member

Claims

1. A battery comprising: an electrode assembly having a first electrode, a second electrode having a different potential from the first electrode, and a current collector; and an exterior member that houses the electrode assembly and is electrically connected to the first electrode, wherein the exterior member is shaped by folding a single sheet member having an opening, and the current collector comprises: a main body that is electrically connected to the second electrode inside the exterior member; and a protrusion that protrudes from the main body, passes through the opening, and is exposed from the exterior member.

2. The battery according to claim 1, wherein the exterior member has planar first and second main surfaces located on opposite sides of the electrode assembly.

3. The battery according to claim 1 or 2, wherein the exterior member has a folded portion where the sheet member is folded, and the opening is located at the folded portion.

4. The battery according to any one of claims 1 to 3, further comprising an insulating member disposed between the exterior member and the protruding portion and sealing the opening.

5. The battery according to any one of claims 1 to 4, wherein the exterior member has a joint portion where the overlapping portions of the sheet member are joined, and the joint portion is spaced apart from the opening.

6. A battery comprising: an electrode assembly having a first electrode, a second electrode having a different potential from the first electrode, and a current collector; and an exterior member that houses the electrode assembly and is in contact with the first electrode, wherein the exterior member is shaped as a single folded sheet member having an opening, and the current collector comprises: a main body that is in contact with the second electrode inside the exterior member; and a protrusion that protrudes from the main body, passes through the opening, and is exposed from the exterior member.

7. A battery unit comprising two batteries according to any one of claims 1 to 6, the two batteries being stacked together with the exterior members of the two batteries in contact with each other.

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