Secondary battery, connection type battery, and battery pack

Abstract

The present invention increases the capacity of a secondary battery. This secondary battery comprises: a positive electrode sheet having a positive electrode current collector and a positive electrode active material layer; a negative electrode sheet having a negative electrode current collector; and a separator positioned between the positive electrode sheet and the negative electrode sheet in the thickness direction.

Description

Secondary battery, connected battery, and battery pack

[0001] The present disclosure relates to a secondary battery and a connected battery including a plurality of secondary batteries.

[0002] Patent Document 1 discloses a power storage cell in which a positive electrode and a negative electrode are laminated via a separator. The positive electrode includes a positive electrode active material layer and a positive electrode current collector that holds the positive electrode active material layer, and the negative electrode includes a negative electrode active material layer and a negative electrode current collector that holds the negative electrode active material layer. The positive electrode current collector and the negative electrode current collector include a support layer containing a resin material and a conductive layer having conductivity superior to that of the support layer.

[0003] Japanese Patent No. 7461518

[0004] A secondary battery according to one aspect of the present disclosure is a secondary battery, including a positive electrode current collector having a first side surface, a first main surface and a second main surface connected to the first side surface, and at least one positive electrode active material layer positioned on at least one of the first main surface and the second main surface; a negative electrode sheet having a negative electrode current collector having a second side surface, a third main surface and a fourth main surface connected to the second side surface; and a separator positioned between the positive electrode sheet and the negative electrode sheet.

[0005] This is a cross-sectional view and a plan view showing an example of a flat-shaped secondary battery according to one embodiment of a secondary battery. This is a cross-sectional view showing an example of a folded secondary battery according to one embodiment of a secondary battery. This is a cross-sectional view showing an example of the secondary battery shown in Figure 1 being folded. This is a diagram showing the positional relationship between the negative electrode sheet and the separator in the plan view of the secondary battery shown in Figure 1. This is a cross-sectional view showing another example of the secondary battery, showing an example of the secondary battery being folded. This is a schematic perspective view showing another example of a folded secondary battery according to one embodiment of a secondary battery. This is a schematic diagram and a schematic perspective view showing an example of the formation process of yet another example of a folded secondary battery according to one embodiment of a secondary battery. This is a cross-sectional view showing an example of a connected-type battery according to one embodiment of a secondary battery. This is a cross-sectional view and a plan view showing an example of a flat-shaped secondary battery according to another embodiment of a secondary battery. This is a cross-sectional view showing an example of a flat-shaped secondary battery and a cross-sectional view showing an example of a folded secondary battery according to yet another embodiment of a secondary battery. This is a perspective view showing an example of a module according to one embodiment. This is a cross-sectional view taken along the line XII-XII of the module shown in Figure 11. This is a schematic cross-sectional view showing a part of the module shown in Figure 12. Figure 11 shows a perspective view of an example of an external electrode, and a cross-sectional view taken along the line XIV-XIV showing a part of the external electrode. Figure 21 shows a perspective view of an example of a module. Figure 32 shows a plan view of a specific example of a control board. Figure 41 shows a cross-sectional view taken along the line XVII-XVII of module 400 shown in Figure 11. Figure 41 shows a diagram illustrating another example of the positional relationship between the secondary battery and the voltage detection terminal. Figure 5 shows a cross-sectional view of another example of a connected battery according to one embodiment. Figure 6 shows a cross-sectional view of yet another example of a connected battery according to one embodiment. Figure 7 shows a cross-sectional view of an example of a unit cell according to one embodiment. Figure 8 shows a cross-sectional view of an example of a secondary battery according to one embodiment. Figure 9 shows a cross-sectional view of an example of a secondary battery module according to one embodiment. Figure 10 shows a cross-sectional view of an example of a secondary battery module according to one embodiment. Figure 11 shows a cross-sectional view of a unit cell according to one embodiment, different from the example shown in Figure 21.

[0006] [Embodiment 1] Figure 1 is a cross-sectional view and a plan view showing an example of a flat-shaped secondary battery 1. Reference numeral 501 in Figure 1 is a cross-sectional view of the secondary battery 1 taken along the line I-I, as shown by reference numeral 502 in Figure 1. Reference numeral 502 in Figure 1 is a plan view of the secondary battery 1 when viewed through the positive electrode sheet 10 and the separator 30. That is, reference numeral 502 indicates a plan view of the negative electrode sheet 20. If, in reference numeral 502, the negative electrode active material layer 22 and the second resin layer 23 of the negative electrode sheet 20 are replaced with the positive electrode active material layer 12 and the first resin layer 13 of the positive electrode sheet 10, then reference numeral 502 indicates a plan view of the positive electrode sheet 10.

[0007] Examples of secondary battery forms include the flat secondary battery shown in Figure 1, and the folded secondary battery shown in Figures 2, 6, and 7. The folded secondary battery is a flat secondary battery shown in Figure 1 that has been folded.

[0008] <Basic internal structure of a secondary battery> The secondary battery 1 is a battery that can be charged or discharged by electrically connecting to external electrodes 201, 202 (see Figure 2). For example, the secondary battery 1 may be installed in energy storage devices for homes, base stations, industrial equipment, vehicles (e.g., electric vehicles, ships, airplanes), robots such as drones, medical devices, tools, small home appliances, or smartphones.

[0009] As shown in Figure 1, the secondary battery 1 may be flattened. The secondary battery 1 may comprise a positive electrode sheet 10, a negative electrode sheet 20, and a separator 30 located between the positive electrode sheet 10 and the negative electrode sheet 20. For example, a flattened secondary battery 1 may be formed by bonding the positive electrode sheet 10 and the negative electrode sheet 20 with the separator 30 in between.

[0010] The positive electrode sheet 10 is a sheet-like member that functions as the positive electrode of the secondary battery 1. The positive electrode sheet 10 may have a positive electrode current collector 11 and a positive electrode active material layer 12. The positive electrode current collector 11 may have a first main surface 111, a second main surface 112, and a first side surface 113. The first main surface 111 and the second main surface 112 are surfaces connected to the first side surface 113. The positive electrode current collector 11 is a surface on which the positive electrode active material layer 12 can be provided. In this embodiment, the positive electrode active material layer 12 is located only on the first main surface 111.

[0011] The negative electrode sheet 20 is a sheet-like member that functions as the negative electrode of the secondary battery 1. The negative electrode sheet 20 may have a negative electrode current collector 21 and a negative electrode active material layer 22 facing the positive electrode active material layer 12. The negative electrode current collector 21 may have a third main surface 211, a fourth main surface 212, and a second side surface 213. The third main surface 211 and the fourth main surface 212 are surfaces connected to the second side surface 213, respectively. The negative electrode current collector 21 is a surface on which the negative electrode active material layer 22 can be provided. In this embodiment, the negative electrode active material layer 22 is located only on the third main surface 211.

[0012] In this embodiment, the first main surface 111 on which the positive electrode active material layer 12 is located and the third main surface 211 on which the negative electrode active material layer 22 is located face each other, and the separator 30 is located between the first main surface 111 and the third main surface 211 that face each other. Thus, the secondary battery 1 of this embodiment has a structure in which the positive electrode active material layer 12 is located on one side of the positive electrode current collector 11 and the negative electrode active material layer 22 is located on one side of the negative electrode current collector 21.

[0013] The positive electrode current collector 11 may be, for example, aluminum foil. The negative electrode current collector 21 may be, for example, copper foil. Both the positive electrode current collector 11 and the negative electrode current collector 21 may be carbon coated. In this embodiment, the sizes of the positive electrode current collector 11 and the negative electrode current collector 21 in plan view (i.e., the size of the main surface on which the positive electrode active material layer 12 or the negative electrode active material layer 22 is located) are the same, but they may be different. The term "same" as used in relation to the configuration may include differences due to manufacturing tolerances.

[0014] The positive electrode current collector 11 and the negative electrode current collector 21 may have a resin layer (not shown) as a base material. For example, the positive electrode current collector 11 may have a configuration in which metal foils such as aluminum foil are positioned on both sides of the resin layer. Also, for example, the negative electrode current collector 21 may have a configuration in which metal foils such as copper foil are positioned on both sides of the resin layer.

[0015] The positive electrode active material layer 12 is a layer containing a positive electrode active material. The positive electrode active material may be, for example, lithium cobaltate, lithium nickelate, lithium iron phosphate, or lithium manganeseate. The negative electrode active material layer 22 is a layer containing a negative electrode active material. The negative electrode active material may be, for example, graphite, lithium titanate, silicon, or silicon monoxide. The positive electrode active material layer 12 and the negative electrode active material layer 22 may contain a conductive additive. The conductive additive may be, for example, carbon black or acetylene black. Furthermore, the positive electrode active material layer 12 and the negative electrode active material layer 22 may be coated onto the positive electrode current collector 11 and the negative electrode current collector 21, respectively.

[0016] In this embodiment, the positive electrode sheet 10 comprises a plurality of positive electrode active material layers 12 spaced apart from each other. The negative electrode sheet 20 comprises a plurality of negative electrode active material layers 22 spaced apart from each other. Each of the plurality of positive electrode active material layers 12 faces each of the plurality of negative electrode active material layers 22. In this embodiment, as shown by reference numeral 502, the plurality of negative electrode active material layers 22 are arranged in a row along the X-axis direction, which is the longitudinal direction of the secondary battery 1, and is perpendicular to the thickness direction of the flat secondary battery 1 (the Z-axis direction in Figure 1). The plurality of positive electrode active material layers 12 are also arranged in a row along the X-axis direction. However, the plurality of positive electrode active material layers 12 and the plurality of negative electrode active material layers 22 may be arranged, for example, along the Y-axis direction, which is the short direction of the secondary battery 1.

[0017] Furthermore, while the positive electrode sheet 10 may have multiple positive electrode active material layers 12, the negative electrode sheet 20 may have a single negative electrode active material layer. In this case, each of the multiple positive electrode active material layers 12 will face the single negative electrode active material layer. Conversely, while the negative electrode sheet 20 may have multiple negative electrode active material layers 22, the positive electrode sheet 10 may have a single positive electrode active material layer. In this case, each of the multiple negative electrode active material layers 22 will face the single positive electrode active material layer.

[0018] The separator 30 may function as an insulating member that insulates the positive electrode current collector 11 and the negative electrode current collector 21. The separator 30 may be made of, for example, a sheet-like nonwoven fabric, a porous material, or a solid electrolyte. When a porous material is used as the separator 30, specifically, a porous film made of a thermoplastic resin with a melting point of about 80°C to 140°C may be used. As the thermoplastic resin, for example, polyolefin polymers such as polypropylene and polyethylene, or polyethylene terephthalate may be used. In addition, a conductive material may be included in the material constituting the separator 30. In this case, the reliability of the secondary battery 1 is improved.

[0019] The separator 30 may have an adhesive layer (not shown). For example, the adhesive layer may be located along the outer periphery of the separator 30 on the surface facing the positive electrode sheet 10 or the surface facing the negative electrode sheet 20. The adhesive layer may be located along the outer periphery of the separator 30 on both the surface facing the positive electrode sheet 10 and the surface facing the negative electrode sheet 20.

[0020] The secondary battery 1 may have an electrolyte. The electrolyte may be a lithium salt, which is the electrolyte, dissolved in a non-aqueous solvent. The non-aqueous solvent may be a carbonate-based solvent. The carbonate-based solvent may be dimethyl carbonate, propylene carbonate, or both dimethyl carbonate and propylene carbonate. In addition, the carbonate-based solvent may contain other solvents as long as it contains at least one of dimethyl carbonate and propylene carbonate. Examples of other solvents include ethylene carbonate, γ-butyrolactone, dimethoxyethane, diethyl carbonate, tetrahydrofuran, and triethylene glycol dimethyl ether. The electrolyte may be lithium hexafluoride phosphate or lithium bis(fluorosulfonyl)imide (LiFSI).

[0021] The electrolyte may be filled inside the secondary battery 1, or it may be impregnated and held in the separator 30. Alternatively, the electrolyte may be impregnated and held in the positive electrode active material layer 12 and the negative electrode active material layer 22. In this embodiment, the secondary battery 1 is described as having an electrolyte, but the secondary battery 1 may have, for example, a gel electrolyte instead of an electrolyte.

[0022] The secondary battery 1 may have a solid electrolyte instead of an electrolyte solution and a gel electrolyte. In this case, the layer containing the solid electrolyte functions as a separator 30.

[0023] <Resin Layers> As shown in Figure 1, the positive electrode sheet 10 further comprises a first resin layer 13. The negative electrode sheet 20 further comprises a second resin layer 23.

[0024] In this embodiment, the second resin layer 23 is located on the third main surface 211, around a plurality of negative electrode active material layers 22 along the outer edge of the negative electrode current collector 21 in a plan view, and between two adjacent negative electrode active material layers 22. Reference numeral 502 indicates an example of a region where the second resin layer 23 is provided. In this embodiment, the first resin layer 13 is located on the first main surface 111, around a plurality of positive electrode active material layers 12 along the outer edge of the positive electrode current collector 11 in a plan view, and between two adjacent positive electrode active material layers 12. This allows the inside of the secondary battery 1 to be sealed, so that the secondary battery 1 can maintain a liquid-tight relationship with the electrolyte. The first resin layer 13 and the second resin layer 23 may be, for example, porous films.

[0025] Specifically, as shown by reference numeral 502, the second resin layer 23 is located in the entire region of the third main surface 211 where the negative electrode active material layer 22 is not located. Similarly, the first resin layer 13 is located in the entire region of the first main surface 111 where the positive electrode active material layer 12 is not located. In this embodiment, the length in the X-axis direction of the outer peripheral regions of the first resin layer 13 and the second resin layer 23 is the same as the length in the X-axis direction of the positive electrode current collector 11 and the negative electrode current collector 21, respectively, but they may be different. Also in this embodiment, the length in the Y-axis direction of the outer peripheral regions of the first resin layer 13 and the second resin layer 23 is longer than the length in the Y-axis direction of the positive electrode current collector 11 and the negative electrode current collector 21, respectively, but they may be the same or shorter.

[0026] The first resin layer 13 may be bonded to the first main surface 111. The first resin layer 13 may be bonded to the first main surface 111 in both a first resin region located around the plurality of positive electrode active material layers 12 along the outer edge of the positive electrode current collector 11 in a plan view, and a second resin region located between two adjacent positive electrode active material layers 12. Either the first resin region or the second resin region may be bonded to the first main surface 111. It is sufficient that at least a portion of the first resin region is bonded to the first main surface 111, and at least a portion of the second resin region is bonded to the first main surface 111.

[0027] The second resin layer 23 may also be bonded to the third main surface 211. The second resin layer 23 may have both a third resin region located around the multiple negative electrode active material layers 22 along the outer edge of the negative electrode current collector 21 in a plan view, and a fourth resin region located between two adjacent negative electrode active material layers 22, both of which may be bonded to the third main surface 211. Either the third resin region or the fourth resin region may be bonded to the third main surface 211. It is sufficient that at least a portion of the third resin region is bonded to the third main surface 211, and at least a portion of the fourth resin region is bonded to the third main surface 211.

[0028] Furthermore, as shown by reference numeral 501, the negative electrode active material layer 22 has a second contact surface 221 that contacts the negative electrode current collector 21 and a second opposing surface 222 that faces the separator 30. As shown by reference numeral 502, the area of ​​the second opposing surface 222 may be larger than the area of ​​the second contact surface 221. In this embodiment, the second opposing surface 222 is in contact with the separator 30, but it does not have to be in contact.

[0029] The second resin layer 23 has a fourth contact surface 231 that contacts the third main surface 211, a fourth opposing surface 232 that faces the separator 30, and a fourth side surface 233 that connects the fourth contact surface 231 and the fourth opposing surface 232. The fourth side surface 233 defines a second opening 234 for bringing the negative electrode active material layer 22 into contact with the negative electrode current collector 21. In this embodiment, the negative electrode active material layer 22 is located inside the second opening 234 and is part of the fourth opposing surface 232, so as to cover the entire periphery of the second opening 234 in a plan view. The negative electrode active material layer 22 may also be located on the fourth opposing surface 232 so as to cover a portion of the periphery of the second opening 234.

[0030] Because the area of ​​the second opposing surface 222 is larger than the area of ​​the second contact surface 221, the area of ​​the second resin layer 23 on the third main surface 211 can be increased. As a result, the entire area of ​​the negative electrode current collector 21 corresponding to the second opening 234 can be used for charging or discharging. However, the negative electrode active material layer 22 does not have to cover the fourth opposing surface 232.

[0031] The positive electrode active material layer 12 also has a first contact surface 121 (a region corresponding to the second contact surface 221) that contacts the positive electrode current collector 11, and a first opposing surface 122 (a region corresponding to the second opposing surface 222) that faces the separator 30. The area of ​​the first opposing surface 122 may be larger than the area of ​​the first contact surface 121. In this embodiment, the first opposing surface 122 is in contact with the separator 30, but it does not have to be in contact.

[0032] The first resin layer 13 has a third contact surface 131 that contacts the first main surface 111, a third opposing surface 132 that faces the separator 30, and a third side surface 133 that connects the third contact surface 131 and the third opposing surface 132. The third side surface 133 defines a first opening 134 for bringing the positive electrode active material layer 12 into contact with the positive electrode current collector 11. In this embodiment, the positive electrode active material layer 12 is located inside the first opening 134 and is part of the third opposing surface 132, so as to cover the entire periphery of the first opening 134 in a plan view. However, the positive electrode active material layer 12 may be located on the third opposing surface 132 so as to cover a part of the periphery of the first opening 134.

[0033] Because the area of ​​the first opposing surface 122 is larger than the area of ​​the first contact surface 121, the area of ​​the first resin layer 13 on the first main surface 111 can be increased. As a result, the entire area of ​​the positive electrode current collector 11 corresponding to the first opening 134 can be used for charging or discharging. However, the positive electrode active material layer 12 does not have to cover the third opposing surface 132.

[0034] In a plan view, the separator 30 may cover the entirety of the first resin layer 13 and the positive electrode active material layer 12, as well as the entirety of the second resin layer 23 and the negative electrode active material layer 22. In this case, the separator 30 superimposes itself on the entirety of the first resin layer 13 and the second resin layer 23, becoming a single component that seals the positive electrode active material layer 12 and the negative electrode active material layer 22. Therefore, the airtightness of the positive electrode active material layer 12 and the negative electrode active material layer 22 is improved.

[0035] The first resin layer 13 and the second resin layer 23 are bonded to the positive electrode current collector 11 or the negative electrode current collector 21 on one side. Furthermore, on the other side, the first resin layer 13 and the second resin layer 23 are bonded to each other, with or without the separator 30. These bonded areas are liquid-tight to prevent leakage of the liquid components in the positive electrode active material layer 12 and the negative electrode active material layer 22.

[0036] Furthermore, the secondary battery 1 may also include an alumina layer instead of the first resin layer 13 and the second resin layer 23.

[0037] Furthermore, as shown by reference numeral 501, the secondary battery 1 may include a third resin layer 35. The third resin layer 35 improves the sealing performance inside the secondary battery 1, so that the secondary battery 1 can hold the electrolyte more liquid-tightly.

[0038] The third resin layer 35 may be located in at least a portion of the outer edges of the positive electrode current collector 11 and the negative electrode current collector 21. In this embodiment, the third resin layer 35 is located in the region of the outer edges of the positive electrode current collector 11 and the negative electrode current collector 21 other than the adhesive layer 40 provided by the positive electrode current collector 11 and the negative electrode current collector 21. Specifically, the third resin layer 35 extends along the Y-axis direction at both ends of the positive electrode current collector 11 and the negative electrode current collector 21 in the X-axis direction. In this embodiment, the third resin layer 35 is bonded to the first resin layer 13 and the second resin layer 23, respectively, but is not limited to this, and may also be bonded to the first main surface 111 and the third main surface 211, respectively.

[0039] The degree of adhesion between the first resin layer 13 and the second resin layer 23 and the member to which these resin layers are bonded (i.e., the degree to which the inside of the secondary battery 1 is sealed) may differ depending on the bonding location. Similarly, the degree of adhesion between the third resin layer 35 and the member to which the third resin layer is bonded may also differ depending on the bonding location.

[0040] Furthermore, the first resin layer 13 is located in the entire region of the first main surface 111 other than the region where the positive electrode active material layer 12 is located, although a part of this region may be missing. The first resin layer 13 may have through holes in a part of its outer peripheral region that penetrate between the positive electrode active material layer 12 and the outer edge of the positive electrode sheet 10. The first resin layer 13 may have through holes in a part of its outer peripheral region that extends in the X-axis direction.

[0041] The second resin layer 23 is located in the entire region of the third main surface 211 other than the region where the negative electrode active material layer 22 is located, although a part of that region may be missing. The second resin layer 23 may have through holes in a part of its outer peripheral region that penetrate between the negative electrode active material layer 22 and the outer edge of the negative electrode sheet 20. The second resin layer 23 may have through holes in a part of its outer peripheral region that extends in the X-axis direction.

[0042] The first resin layer 13 and the second resin layer 23 have through holes, which allows gas generated inside the secondary battery 1 to be released to the outside of the secondary battery 1. Only one of the first resin layer 13 or the second resin layer 23 may have through holes, or neither the first resin layer 13 nor the second resin layer 23 may have through holes. Furthermore, the first resin layer 13 and the second resin layer 23 may have through holes only during the manufacturing of the secondary battery 1. In other words, the secondary battery 1 as a finished product may not have through holes.

[0043] <Adhesive Layer> The secondary battery 1 may include an adhesive layer 40 that adheres the positive electrode sheet 10 and the negative electrode sheet 20. The adhesive layer 40 may be located on at least a portion of the surface of the positive electrode sheet 10 facing the negative electrode sheet 20, or on at least a portion of the surface of the negative electrode sheet 20 facing the positive electrode sheet 10. The adhesive layer 40 may also be located on both the positive electrode sheet 10 and the negative electrode sheet 20. In this case, the adhesive layer 40 located on the positive electrode sheet 10 and the adhesive layer 40 located on the negative electrode sheet 20 may or may not face each other when the positive electrode sheet 10 and the negative electrode sheet 20 are facing each other.

[0044] In the present embodiment, as shown by reference numeral 502, the adhesive layer 40 extends along the X-axis direction at both ends of the second resin layer 23 in the Y-axis direction. In the present embodiment, also in the first resin layer 13, the adhesive layer 40 extends along the X-axis direction at both ends of the first resin layer 13 in the Y-axis direction. In the present embodiment, the adhesive layer 40 is located in the region where the first resin layer 13 protrudes from the positive electrode current collector 11 and in the region where the second resin layer 23 protrudes from the negative electrode current collector 21.

[0045] The first resin layer 13 may have a first adhesive layer (not shown) that adheres to the positive electrode current collector 11 at the third contact surface 131. The first resin layer 13 is adhered to the first main surface 111 by the first adhesive layer. And the first resin layer 13 has the adhesive layer 40 at the third opposing surface 132. Therefore, in the present embodiment, the first resin layer 13 has adhesive layers on both the third contact surface 131 and the third opposing surface 132. Regarding the second resin layer 23, it may have a second adhesive layer (not shown) that adheres to the negative electrode current collector 21 at the fourth contact surface 231. The second resin layer 23 is adhered to the third main surface 211 by the second adhesive layer. And the second resin layer 23 has the adhesive layer 40 at the fourth opposing surface 232. Therefore, in the present embodiment, the second resin layer 23 has adhesive layers on both the fourth contact surface 231 and the fourth opposing surface 232.

[0046] As the material of the first adhesive layer and the material of the second adhesive layer, the material of the adhesive layer 40 may be used, or different materials may be used. Also, as the bonding method of the adhesive layer 40 to the first resin layer 13, the bonding method of the first adhesive layer may be used, or different methods may be used. Regarding the second resin layer 23, as the bonding method of the adhesive layer 40 to the second resin layer 23, the bonding method of the second adhesive layer may be used, or different methods may be used.

[0047] <Folding structure> Figure 2 is a cross-sectional view showing an example of the secondary battery 1 in a folded state. Figure 3 is a cross-sectional view showing an example of the state of the secondary battery 1 shown in Figure 1 during the folding process. The cross-sections shown in Figures 2 and 3 show the cross-section shown in Figure 1. The secondary battery 1 may be used in the folded state shown in Figure 2.

[0048] As shown in Fig. 2, the secondary battery 1 is folded, and may have at least one bending portion 3 and a plurality of flat portions 2 that are connected to the bending portion 3 and adjacent to each other. By folding a part of the flat secondary battery 1 to fold the secondary battery 1, the secondary battery 1 having the bending portion 3 and the flat portion 2 is formed. With the flat secondary battery 1 described above, the capacity can be increased. And by making the secondary battery 1 into a folded shape, the capacity can be increased in a compact form.

[0049] By bending one part of the flat secondary battery 1, the folded secondary battery 1 has one bending portion 3 and two flat portions 2. By bending the flat secondary battery 1 at two places, the folded secondary battery 1 has two bending portions 3 and three flat portions 2. Thus, by bending n places (n is a natural number) of the flat secondary battery 1, the folded secondary battery 1 has n bending portions 3 and n + 1 flat portions 2.

[0050] When the flat secondary battery 1 is bent multiple times, the second main surfaces 112 of the positive electrode current collector 11 face each other, and the fourth main surfaces 212 of the negative electrode current collector 21 face each other, and by alternately making valley folds, the folded secondary battery 1 is formed. Such a fold may be referred to as a zigzag fold.

[0051] In the example of Fig. 2, the number of flat portions 2 is five, but it is not limited to this. The number of flat portions 2 can be arbitrarily set, and it may be an odd number (but three or more) or an even number (but two or more).

[0052] Each flat portion 2 is adjacent in the thickness direction of the folded secondary battery 1. In the flat secondary battery 1 shown in Fig. 1, its outer peripheral portion is not covered with a resin layer. Therefore, since no resin layer is interposed between two adjacent flat portions 2 in the thickness direction, the flat portions 2 are adjacent to each other. Thus, compared with the case where the resin layer is interposed, the volume of the folded secondary battery 1 can be reduced. As a result, the energy density of the secondary battery 1 can be increased.

[0053] As shown in Figure 2, the two outermost planar sections 2 in the secondary battery 1 are referred to as planar sections 2U1 and 2L1, respectively. As shown in Figure 2, the external electrode 201 is connected to the second main surface 112 of the positive electrode current collector 11 included in planar section 2U1. The external electrode 202 is connected to the fourth main surface 212 of the negative electrode current collector 21 included in planar section 2L1. Therefore, the secondary battery 1 does not require extension tabs for connecting to the external electrodes 201 and 202, nor does it require space for providing extension tabs.

[0054] In this embodiment, as shown in Figure 1, the secondary battery 1 may include a first region 5 and a second region 6. In this embodiment, the first region 5 is a region located between two adjacent positive electrode active material layers 12 on the first main surface 111. The second region 6 is a region located between two adjacent negative electrode active material layers 22 on the third main surface 211. That is, in this embodiment, the first region 5 is a region where no positive electrode active material layer 12 exists, and the second region 6 is a region where no negative electrode active material layer 22 exists.

[0055] As shown in Figure 3, in this embodiment, by folding the first region 5 and the second region 6, the folded secondary battery 1 (secondary battery 1 having a zigzag structure) shown in Figure 2 may have a folded portion 3 that includes the first region 5 and the second region 6. That is, in this embodiment, in the folded secondary battery 1, each planar portion 2 is a region that includes an electrode layer comprising one positive electrode active material layer 12 and one negative electrode active material layer 22 facing the positive electrode active material layer 12.

[0056] By folding the first region 5 and the second region 6, the flattened secondary battery 1 can be easily folded. In other words, the flattened secondary battery 1 is easy to fold. Furthermore, because the bent portion 3 includes the first region 5 and the second region 6, the width of the bent portion 3 can be reduced. Therefore, the width of the secondary battery 1 in the folded state can be reduced. Consequently, the volume of the secondary battery 1 in the folded state can be reduced compared to the case where the positive electrode active material layer 12 and the negative electrode active material layer 22 are located in the bent portion 3. The above width refers to the length in the direction perpendicular to the thickness direction of the secondary battery 1 in the cross-section of Figure 2.

[0057] The thickness of the positive electrode current collector 11 and the negative electrode current collector 21 included in the bent portion 3 may be thinner than the thickness of the positive electrode current collector 11 and the negative electrode current collector 21 included in the flat portion 2. This makes the positive electrode current collector 11 and the negative electrode current collector 21 more prone to rupture. For example, even if the secondary battery 1 catches fire due to some problem, the positive electrode current collector 11 and the negative electrode current collector 21 will rupture relatively quickly, thus reducing the possibility of the fire spreading.

[0058] Furthermore, in a plan view, the ends of the planar portions 2U1 and 2L1 may be formed to be shorter than the bent portion 3. In the manufacturing process of the secondary battery 1, the secondary battery 1 may be compressed from a direction parallel to the main surfaces of the positive electrode current collector 11 and the negative electrode current collector 21 in order to reduce the space of the bent portion 3. In that case, the formation of the ends of the planar portions 2U1 and 2L1 as described above reduces the possibility of the positive electrode current collector 11 of the planar portions 2U1 and 2L1 short-circuiting with the negative electrode current collector 21.

[0059] <Other Components> (Position of Separator) Figure 4 is a diagram showing the positional relationship between the negative electrode sheet 20 and the separator 30 in the plan view of the secondary battery 1 shown in Figure 1.

[0060] Reference numeral 301 indicates the surface size of the separator 30 and the position of the separator 30 on the negative electrode sheet 20 in this embodiment. In the example of reference numeral 301, the separator 30 faces the entire region of the second resin layer 23 on the negative electrode current collector 21, excluding the third resin layer 35. Also, the separator 30 faces the entire region of the first resin layer 13 on the positive electrode current collector 11, excluding the third resin layer 35.

[0061] On the other hand, as shown in reference numeral 302, the separator 30 may be sized to cover at least a portion of the third resin layer 35 and at least a portion of the adhesive layer 40 in a plan view. In this case, the separator 30 may be bonded to the first resin layer 13 and the second resin layer 23 via the adhesive layer 40. This further reduces the possibility of contact between the positive electrode sheet 10 and the negative electrode sheet 20, thereby improving the reliability of the secondary battery 1.

[0062] In this embodiment, the adhesive layer 40 is located outside the first main surface 111 and the third main surface 211 in a plan view. Therefore, in the example of reference numeral 302, the separator 30 may be bonded to the first resin layer 13 and the second resin layer 23 outside the positive electrode current collector 11 and the negative electrode current collector 21.

[0063] Furthermore, the separator 30 may cover the entire positive electrode current collector 11 and the entire negative electrode current collector 21 in a plan view.

[0064] (Metal layer) Figure 5 is a cross-sectional view showing another example of a secondary battery 1, and is a cross-sectional view showing an example of the secondary battery 1 in the process of being folded. As shown in Figure 5, the secondary battery 1 may be provided with a metal layer 45. Specifically, the secondary battery 1 may be provided with a metal layer 45 on the fourth main surface 212 of each negative electrode current collector 21 that constitutes each planar portion 2 that is in contact with each other. The metal layer 45 can improve the contact between the negative electrode current collectors 21 that are in contact with each other. It can also reduce the possibility of malfunctions such as electrical insulation due to corrosion of the negative electrode current collector 21.

[0065] The metal layer 45 does not have to be located on all of the multiple fourth main surfaces 212 that are in contact with each other, but may be located on only some of the multiple fourth main surfaces 212 that are in contact with each other. Alternatively, the metal layer 45 may be provided on the second main surface 112 of each positive electrode current collector 11 that constitutes each of the planar portions 2 that are in contact with each other.

[0066] (Active material layers on both sides of the current collector) In this embodiment, the positive electrode active material layer 12 is located on the first main surface 111 and not on the second main surface 112. Similarly, the negative electrode active material layer 22 is located on the third main surface 211 and not on the fourth main surface 212. However, this is not limited to this configuration, and the positive electrode active material layer 12 may be located on both the first and second main surfaces 111 and the second main surface 112, and the negative electrode active material layer 22 may be located on both the third and fourth main surfaces 211. That is, the secondary battery 1 may have a structure in which the positive electrode active material layer 12 is located on both sides of the positive electrode current collector 11 and the negative electrode active material layer 22 is located on both sides of the negative electrode current collector 21. Furthermore, the secondary battery 1 may have a structure in which the positive electrode active material layer 12 is located on both sides of the positive electrode current collector 11 and the negative electrode active material layer 22 is located on one side of the negative electrode current collector 21, or a structure in which the positive electrode active material layer 12 is located on one side of the positive electrode current collector 11 and the negative electrode active material layer 22 is located on both sides of the negative electrode current collector 21. Therefore, the positive electrode active material layer 12 only needs to be located on at least one of the first main surface 111 and the second main surface 112, and the negative electrode active material layer 22 only needs to be located on at least one of the third main surface 211 and the fourth main surface 212.

[0067] In this case, the first resin layer 13 may be located around a plurality of positive electrode active material layers 12 along the outer edge of the positive electrode current collector 11 in a plan view, and between two adjacent positive electrode active material layers 12, on at least one of the first main surface 111 and the second main surface 112. The second resin layer 23 may be located around a plurality of negative electrode active material layers 22 along the outer edge of the negative electrode current collector 21 in a plan view, and between two adjacent negative electrode active material layers 22, on the third main surface 211 and the fourth main surface 212.

[0068] Furthermore, the first region 5 may be a region located between two adjacent positive electrode active material layers 12 on at least one of the first main surface 111 and the second main surface 112. The second region 6 may be a region located between two adjacent negative electrode active material layers 22 on at least one of the third main surface 211 and the fourth main surface 212.

[0069] In a structure where positive electrode active material layers 12 are located on both sides of the positive electrode current collector 11 and negative electrode active material layers 22 are located on both sides of the negative electrode current collector 21, the folded secondary battery may be formed with a structure other than the zigzag structure shown in Figure 2.

[0070] Figure 6 shows another example of a folded secondary battery 1. As shown in Figure 6, a wound secondary battery 1 may be formed by valley-folding a flat secondary battery 1 on the positive electrode sheet 10 side or the negative electrode sheet 20 side. The wound secondary battery 1 may be a cylindrical secondary battery 1 as shown by reference numeral 511, or a cylindrical plate type secondary battery 1 as shown by reference numeral 512. The cylindrical plate type secondary battery 1 is a shape formed when two opposing points are pressed into a cylindrical secondary battery 1. As shown by reference numeral 512, the cylindrical plate type secondary battery 1 may have a straight section 7 and a curved section 8 at opposing positions when viewed from above.

[0071] Reference numeral 521 in Figure 7 is a schematic diagram showing an example of the formation process of another example of a folded secondary battery, and reference numeral 522 is a schematic perspective view of that other example. In Figure 7, the two secondary batteries 1 are referred to as the first secondary battery 1 and the second secondary battery 1, respectively.

[0072] As shown in reference numeral 521, the positive electrode sheet 10 of the flattened first secondary battery 1 and the negative electrode sheet 20 of the flattened second secondary battery 1 are bonded together at their ends. The ends are bonded together so that the long axis direction of the flattened first secondary battery 1 and the long axis direction of the flattened second secondary battery 1 are approximately perpendicular. In this state, the positive electrode sheet 10 side of the first secondary battery 1 is folded in a valley fold, and then the negative electrode sheet 20 side of the second secondary battery 1 is folded in a valley fold. After that, the negative electrode sheet 20 side of the first secondary battery 1 is folded in a valley fold, and then the positive electrode sheet 10 side of the second secondary battery 1 is folded in a valley fold. By alternately folding the first secondary battery 1 and the second secondary battery 1 in this way, a secondary battery 100 is formed in a state where two secondary batteries 1 are folded together, as shown in reference numeral 522.

[0073] (Voltage measurement via the bent portion) The bent portion 3 includes a first bent portion 3 that includes a positive electrode current collector 11 located on the side of the secondary battery 1, and a second bent portion 3 that includes a negative electrode current collector 21 located on the side of the secondary battery 1. By electrically connecting the positive electrode current collector 11 and the negative electrode current collector 21 to a voltmeter, the voltage between the positive electrode current collector 11 and the negative electrode current collector 21 can be measured. Therefore, voltage measurement can be easily performed without connecting extension tabs to each of the positive electrode current collector 11 and the negative electrode current collector 21.

[0074] (Charging and discharging via the bent portion) Alternatively, the external electrode 201 may be electrically connected to the positive electrode current collector 11 located on the side of the secondary battery 1 at the first bent portion 3, and the external electrode 202 may be electrically connected to the negative electrode current collector 21 located on the side of the secondary battery 1 at the second bent portion 3. In this case, the secondary battery 1 can be charged or discharged via its side.

[0075] The internal space of the first bent portion 3 may include a first support member (not shown) that supports the positive electrode current collector 11 located on the side surface of the secondary battery 1. The first support member may support the positive electrode current collector 11 when an external force is applied to it. For example, when bonding an external electrode 201 to the positive electrode current collector 11, the first support member supports the positive electrode current collector 11 from inside the first bent portion 3, making it easier to bond the external electrode 201 to the positive electrode current collector 11.

[0076] The internal space of the second bent portion 3 may also be provided with a second support member (not shown) that supports the negative electrode current collector 21 located on the side surface of the secondary battery 1. The second support member may support the negative electrode current collector 21 when an external force is applied to it. For example, when bonding an external electrode 202 to the negative electrode current collector 21, the second support member supports the negative electrode current collector 21 from inside the bent portion 3, making it easier to bond the external electrode 202 to the negative electrode current collector 21.

[0077] (Structure of the bent portion) In this embodiment, the positive electrode active material layer 12 and the negative electrode active material layer 22 are not located in the bent portion 3, but they may be located in the bent portion 3. In this case, the thickness of the bent portion 3 may be the same as the thickness of the flat portion 2, or it may be thinner than the thickness of the flat portion 2.

[0078] (Connection to external electrodes) The secondary battery 1 expands or contracts, for example, due to charging or discharging. The external electrodes 201 and 202 may be connected to the planar portions 2U1 and 2L1 so as to follow the expansion or contraction of the secondary battery 1.

[0079] Furthermore, when external electrodes 201 and 202 are connected to the bent portion 3, members capable of following the expansion or contraction of the secondary battery 1 may be connected to the flat portions 2U1 and 2L1.

[0080] (Another example of the negative electrode active material) The negative electrode active material may be metallic lithium. In this case, the negative electrode sheet 20 does not have to have a negative electrode active material layer 22. Therefore, in this case, the negative electrode sheet 20 does not have to have a second resin layer 23, and in the folded secondary battery 1, the bent portion 3 does not have to have a second region 6.

[0081] <Connected Battery> Figure 8 is a cross-sectional view showing an example of a connected battery 200. The connected battery 200 is a battery that comprises multiple rechargeable batteries 1 in a folded state. As shown in Figure 8, the connected battery 200 may have the planar portions 2 of two adjacent rechargeable batteries 1 connected to each other. This allows multiple rechargeable batteries 1 to be connected in series. In the example in Figure 8, the connected battery 200 has a structure in which two rechargeable batteries 1 are connected, but it is not limited to this, and may have a structure in which three or more rechargeable batteries 1 are connected.

[0082] In Figure 8, the two secondary batteries 1 are referred to as the upper secondary battery 1U and the lower secondary battery 1L, respectively. The two outermost planar sections 2 of the upper secondary battery 1U are referred to as planar sections 2U1 and 2L1, respectively. The two outermost planar sections 2 of the lower secondary battery 1L are referred to as planar sections 2U2 and 2L2, respectively. In addition, of the multiple bent sections 3 located on the outermost side in the thickness direction of the connected battery 200 (i.e., the stacking direction of the secondary batteries 1), the two bent sections 3 of the upper secondary battery 1U are referred to as bent sections 3U11 and 3U12, respectively. Of the multiple bent sections 3, the two bent sections 3 of the lower secondary battery 1L are referred to as bent sections 3L21 and 3L22, respectively.

[0083] In the example shown in Figure 8, the fourth main surface 212 of the negative electrode current collector 21 of the planar section 2L1 and the second main surface 112 of the positive electrode current collector 11 of the planar section 2U2 are connected to adjacent planar sections 2L1 and 2U2. In addition, external electrodes 201 and 202 are connected to each of the two planar sections 2U1 and 2L2 located on the outermost part of the connected battery 200.

[0084] Therefore, the connected battery 200 does not require extension tabs for connecting to external electrodes 201 and 202, nor does it require space for providing extension tabs. In addition, the connected battery 200 does not require extension tabs for connecting each of the multiple secondary batteries 1, nor does it require space for providing such extension tabs.

[0085] Furthermore, each of the multiple secondary batteries 1 in the connected battery 200 may have an odd number of planar sections 2. This allows two adjacent current collectors to become the positive electrode current collector 11 and the negative electrode current collector 21. Therefore, a connected battery 200 can be formed by simply stacking multiple secondary batteries 1 in series.

[0086] In the example shown in Figure 8, the upper secondary battery 1U and the lower secondary battery 1L are each equipped with five flat sections 2. Therefore, the current collector located on the outermost edge of the secondary battery 1 in the flat sections 2U1 and 2U2 is the positive electrode current collector 11, and the current collector located on the outermost edge of the secondary battery 1 in the flat sections 2L1 and 2L2 is the negative electrode current collector. Consequently, in the flat sections 2L1 and 2U2, the positive electrode current collector 11 and the negative electrode current collector 21 are adjacent to each other.

[0087] (Addition of pressing force) In the connected battery 200, a pressing force may be applied to each of the two outermost planar sections 2. That is, a pressing force may be applied to the main surface of the current collector included in each of the two planar sections 2. In the example of Figure 8, a pressing force may be applied to both the second main surface 112 of the positive electrode current collector 11 included in planar section 2U1 and the fourth main surface 212 of the negative electrode current collector 21 included in planar section 2L2. However, a pressing force may be applied to only one of the planar section 2U1 and the planar section 2L2. By applying a pressing force to at least one of the planar section 2U1 and the planar section 2L2, the possibility of adjacent secondary batteries 1 shifting relative to each other can be reduced.

[0088] Furthermore, a pressing force in the thickness direction may be applied to each of the multiple bent portions 3 located on the outermost side in the thickness direction of the connected battery 200. In the example of Figure 8, a pressing force may be applied to the bent portions 3U11 and 3U12. In addition, a pressing force may be applied to the bent portions 3L21 and 3L22.

[0089] However, if the two secondary batteries 1 located on the outermost side in the thickness direction of the connected battery 200 are referred to as the first outer battery and the second outer battery, then pressing force may be applied only to the bent portion 3 of the first outer battery among the plurality of bent portions 3 located on the outermost side. Alternatively, pressing force may be applied only to the bent portion 3 of the second outer battery among the plurality of bent portions 3. In the example of Figure 8, pressing force may be applied only to at least one of the bent portions 3U11 and 3U12. Alternatively, pressing force may be applied only to at least one of the bent portions 3L21 and 3L22. Applying pressing force to at least one bent portion 3 located on the outermost side in the thickness direction of the connected battery 200 can also reduce the possibility of adjacent secondary batteries 1 shifting relative to each other.

[0090] Furthermore, the pressing force may be applied only to the bent portion 3, or it may be applied to both the flat portion 2 and the bent portion 3.

[0091] (Other Connections) In this embodiment, a connected battery 200 in which two adjacent secondary batteries 1 in a folded state are directly connected has been described, but the invention is not limited to this, and the two adjacent secondary batteries 1 may be electrically connected via a metal layer. In the example of Figure 8, adjacent planar portions 2L1 and 2U2 may be electrically connected via a metal layer. This reduces the possibility of corrosion of the secondary batteries 1.

[0092] Furthermore, although this embodiment describes a connected battery 200 in which the planar portions 2 of two adjacent secondary batteries 1 are connected, the invention is not limited to this, and the sides of multiple secondary batteries 1 in a folded state, i.e., the bent portions 3, may be connected to each other. The external electrodes 201 and 202 may be electrically connected to the bent portion 3 of the outermost secondary battery 1. In this configuration as well, adjacent secondary batteries 1 may be electrically connected via a metal layer.

[0093] Other configurations in which multiple secondary batteries 1 are connected in series include, for example, the connected battery 200A shown in Figure 19 and the connected battery 200B shown in Figure 20. Figure 19 is a cross-sectional view of the connected battery 200A, and Figure 20 is a cross-sectional view of the connected battery 200B. In Figures 19 and 20, the external electrodes 201 and 202 are described as the external electrode 203. The connected batteries 200A and 200B may be just one example of a configuration when mounted in large-scale equipment.

[0094] As shown in Figure 19, the connected battery 200A may be configured in which multiple secondary batteries 1 are connected in multiple stages via external electrodes 203. In the connected battery 200A, the planar portions 2 of adjacent secondary batteries 1 may be electrically connected via the external electrodes 203 in the thickness direction of the folded secondary batteries 1. Multiple secondary batteries 1 connected in this series may be arranged in a direction perpendicular to the thickness direction via an insulating member 205.

[0095] As shown in Figure 20, the connected battery 200B may have a configuration in which multiple secondary batteries 1 are connected in multiple stages via an insulating member 205. In the connected battery 200B, the sides of adjacent secondary batteries 1, i.e., the bent portions 3, may be electrically connected in a direction perpendicular to the thickness direction of the folded secondary battery 1. Multiple secondary batteries 1 connected in this series may be arranged side by side in the thickness direction via an insulating member 205.

[0096] In this embodiment, connected-type batteries 200, 200A, and 200B were described, in which multiple folded secondary batteries 1 are connected in series. However, the connected-type battery 200 is not limited to this, and may have a structure in which multiple folded secondary batteries 1 are connected in parallel. Alternatively, multiple flat secondary batteries 1 may be connected in series or in parallel.

[0097] Furthermore, when a secondary battery 1, in which positive electrode active material layers 12 are located on both sides of the positive electrode current collector 11 and negative electrode active material layers 22 are located on both sides of the negative electrode current collector 21, is folded to form a connected battery, in addition to the configuration shown in Figure 2, the configurations shown in Figure 6 and Figure 7 can also be adopted. Similarly, when a secondary battery 1 equipped with a negative electrode sheet 20 that does not have a negative electrode active material layer 22 is folded to form a connected battery, the configurations shown in Figure 2, Figure 6 and Figure 7 can also be adopted.

[0098] Furthermore, each secondary battery 1 may have an insulating layer between the positive electrode current collector 11 and the negative electrode current collector 21. The insulating layer may be formed to be longer than the positive electrode current collector 11 and the negative electrode current collector 21. This reduces the possibility of a short circuit occurring between the areas where the positive electrode current collectors 11 are welded together and the negative electrode current collector 21, and between the areas where the negative electrode current collectors 21 are welded together and the positive electrode current collector 11.

[0099] For example, the first resin layer 13 and the second resin layer 23 may function as insulating layers by extending between the positive electrode current collector 11 and the negative electrode current collector 21. Alternatively, the separator 30 may function as an insulating layer by extending between the positive electrode current collector 11 and the negative electrode current collector 21. Furthermore, the secondary battery 1 may also have an insulating layer separate from the first resin layer 13, the second resin layer 23, and the separator 30.

[0100] Furthermore, the first resin layer 13, the second resin layer 23, and the separator 30 may each function as an insulating layer by extending between the positive electrode current collector 11 and the negative electrode current collector 21. In this case, the distance over which the first resin layer 13 and the second resin layer 23 extend may be longer than the distance over which the separator 30 extends. That is, in a plan view, the first resin layer 13 and the second resin layer 23 may extend beyond the separator 30.

[0101] [Embodiment 2] Another embodiment of the present disclosure is described below. For convenience of explanation, components having the same function as those described in the above embodiments are denoted by the same reference numerals, and their descriptions are not repeated.

[0102] Figure 9 shows a cross-sectional view and a plan view of an example of a flattened secondary battery 1A. Reference numeral 531 in Figure 9 is a cross-sectional view of the secondary battery 1A taken along the line VII-VII, as shown by reference numeral 532 in Figure 9. Reference numeral 532 in Figure 9 is a plan view of the secondary battery 1A when viewed through the positive electrode sheet 10A and the separator 30. That is, reference numeral 532 indicates a plan view of the negative electrode sheet 20A. If, in reference numeral 532, the negative electrode active material layer 22 and the second resin layer 23 of the negative electrode sheet 20A are replaced with the positive electrode active material layer 12 and the first resin layer 13 of the positive electrode sheet 10A, then reference numeral 532 indicates a plan view of the positive electrode sheet 10A.

[0103] The secondary battery 1A differs from the secondary battery 1 in that it is equipped with a positive electrode sheet 10A and a negative electrode sheet 20A in place of the positive electrode sheet 10 and negative electrode sheet 20 of the secondary battery 1.

[0104] The negative electrode sheet 20A may include a second resin layer 23 located around the negative electrode active material layer 22 along the outer edge of the negative electrode current collector 21 in a plan view, on at least one of the third main surface 211 and the fourth main surface 212. In this embodiment, the negative electrode sheet 20A includes the second resin layer 23 on the third main surface 211. Reference numeral 532 indicates an example of a region where the second resin layer 23 is provided. As shown in reference numeral 532, in the negative electrode sheet 20A of this embodiment, the second resin layer 23 is not located between two adjacent negative electrode active material layers 22. Therefore, in this embodiment, as shown in reference numeral 531, the negative electrode active material layer 22 does not cover the second resin layer 23 between two adjacent negative electrode active material layers 22. At the position where the negative electrode active material layer 22 is in contact with the second resin layer 23, it may or may not cover the second resin layer 23.

[0105] The positive electrode sheet 10A may also have a first resin layer 13 located around the positive electrode active material layer 12 along the outer edge of the positive electrode current collector 11 in a plan view, on at least one of the first main surface 111 and the second main surface 112. In this embodiment, the positive electrode sheet 10A has a first resin layer 13 on the first main surface 111. That is, in the positive electrode sheet 10A of this embodiment as well, the first resin layer 13 is not located between two adjacent positive electrode active material layers 12. Therefore, in this embodiment, as shown by reference numeral 531, the positive electrode active material layer 12 does not cover the first resin layer 13 between two adjacent positive electrode active material layers 12. At the position where the positive electrode active material layer 12 is in contact with the first resin layer 13, it may be positioned to cover the first resin layer 13, or it may not cover the first resin layer 13.

[0106] In this manner, the first resin layer 13 is bonded along the outer edge of the positive electrode current collector 11, and the second resin layer 23 is bonded along the outer edge of the negative electrode current collector 21. Therefore, the inside of the secondary battery 1A can be sealed, and the secondary battery 1A can maintain a liquid-tight relationship with the electrolyte.

[0107] Furthermore, by folding the flat secondary battery 1A, a folded secondary battery 1A can be formed having at least one bent portion 3 and a plurality of adjacent planar portions 2 connected to the bent portion 3. Therefore, the capacity of the secondary battery 1A can also be increased. In addition, by connecting a plurality of folded secondary batteries 1A, a connected battery comprising such plurality of secondary batteries 1A can be formed.

[0108] (Number of active material layers) In this embodiment, the positive electrode current collector 11 has a plurality of positive electrode active material layers 12, and the negative electrode current collector 21 has a plurality of negative electrode active material layers 22, but is not limited to this. The positive electrode current collector 11 may have one positive electrode active material layer 12, and the negative electrode current collector 21 may have one negative electrode active material layer 22. That is, the positive electrode current collector 11 may have at least one positive electrode active material layer 12, and the negative electrode current collector 21 may have at least one negative electrode active material layer 22.

[0109] The size of one negative electrode active material layer 22 in a plan view may be, for example, large enough to cover all of the multiple negative electrode active material layers 22 shown in Figure 9 (i.e., multiple negative electrode active material layers 22 arranged at a distance from each other). Similarly, one positive electrode active material layer 12 may be, for example, large enough to cover all of the multiple positive electrode active material layers 12 (i.e., multiple positive electrode active material layers 12 arranged at a distance from each other).

[0110] (Additional notes regarding Embodiment 2) As described above, secondary battery 1A has the same structure as secondary battery 1 of Embodiment 1, except that the first resin layer 13 is not located between two adjacent positive electrode active material layers 12, and the second resin layer 23 is not located between two adjacent negative electrode active material layers 22. Therefore, the contents described in Embodiment 1 can also be applied to secondary battery 1A, except for the description of the first resin layer 13 that is not located between two adjacent positive electrode active material layers 12, and the description of the second resin layer 23 that is not located between two adjacent negative electrode active material layers 22. Furthermore, it can also be applied to connected batteries that consist of multiple secondary batteries 1A.

[0111] For example, a flat secondary battery 1 in which positive electrode active material layers 12 are located on both sides of the positive electrode current collector 11 and negative electrode active material layers 22 are located on both sides of the negative electrode current collector 21 can be applied to secondary battery 1A. When this secondary battery 1A is folded, it may be in the form of secondary battery 1 shown in Figures 2 and 6, or in the form of secondary battery 100 shown in Figure 7.

[0112] However, in this embodiment as well, a positive electrode active material layer 12 in which the area of ​​the first opposing surface 122 is larger than the area of ​​the first contact surface 121 may be bonded to the main surface of the positive electrode current collector 11. Alternatively, a negative electrode active material layer 22 in which the area of ​​the second opposing surface 222 is larger than the area of ​​the second contact surface 221 may be bonded to the main surface of the negative electrode current collector 21.

[0113] For example, if the positive electrode active material layer 12 is positioned to cover the first resin layer 13 in the region where it is in contact with the first resin layer 13, the area of ​​the first opposing surface 122 will be larger than the area of ​​the first contact surface 121. Similarly, if the negative electrode active material layer 22 is positioned to cover the second resin layer 23 in the region where it is in contact with the second resin layer 23, the area of ​​the second opposing surface 222 will be larger than the area of ​​the second contact surface 221.

[0114] For example, if a positive electrode active material layer 12 is provided, the positive electrode active material layer 12 may be located inside the first opening 134 and be part of the third opposing surface 132, covering at least a portion of the periphery of the first opening 134 in a plan view. In this case as well, the area of ​​the first opposing surface 122 will be larger than the area of ​​the first contact surface 121. Similarly, if a negative electrode active material layer 22 is provided, the negative electrode active material layer 22 may be located inside the second opening 234 and be part of the fourth opposing surface 232, covering a portion of the periphery of the second opening 234 in a plan view. In this case as well, the area of ​​the second opposing surface 222 will be larger than the area of ​​the second contact surface 221.

[0115] Furthermore, the positive electrode active material layer 12 and the negative electrode active material layer 22 may or may not be located in the bent portion 3. If the positive electrode active material layer 12 and the negative electrode active material layer 22 are located in the bent portion 3, the thickness of the bent portion 3 may be the same as the thickness of the flat portion 2, or it may be thinner than the thickness of the flat portion 2.

[0116] Furthermore, a flat secondary battery 1 without a negative electrode active material layer 22 can be applied to secondary battery 1A. When this secondary battery 1A is folded, it may take the form of secondary battery 1 shown in Figures 2 and 6, or the form of secondary battery 100 shown in Figure 7.

[0117] [Embodiment 3] Reference numeral 541 in Figure 10 is a cross-sectional view showing an example of a flattened secondary battery 1B. Reference numeral 542 in Figure 10 is a cross-sectional view showing an example of a folded secondary battery 1B. The cross-section shown in reference numeral 542 is the same as the cross-section shown in reference numeral 541.

[0118] As shown by reference numeral 541, the secondary battery 1B comprises a positive electrode sheet 10B and a negative electrode sheet 20B. The positive electrode sheet 10B has a positive electrode current collector 11 and a positive electrode active material layer 12 located on the first main surface 111 of the positive electrode current collector 11. The negative electrode sheet 20B has a negative electrode current collector 21 and a negative electrode active material layer 22 located on the third main surface 211 of the negative electrode current collector 21. In other words, it differs from the secondary battery 1 in that the positive electrode sheet 10B does not have a first resin layer 13 and the negative electrode sheet 20B does not have a second resin layer 23.

[0119] In the case of the positive electrode sheet 10B and the negative electrode sheet 20B, the positive electrode active material layer 12 may be located on the second main surface 112 of the positive electrode current collector 11, and the negative electrode active material layer 22 may be located on the fourth main surface 212 of the negative electrode current collector 21.

[0120] Furthermore, as shown in reference numeral 542, the secondary battery 1B may also have at least one bent portion 3 and a plurality of adjacent planar portions 2 connected to the bent portion 3 when folded. Therefore, the capacity of the secondary battery 1B can also be increased. In addition, by connecting a plurality of secondary batteries 1B in their folded state, a connected battery comprising such plurality of secondary batteries 1B can be formed.

[0121] (Additional notes regarding Embodiment 3) As described above, secondary battery 1B has the same structure as secondary battery 1 of Embodiment 1, except that it does not have the first resin layer 13 and the second resin layer 23. Therefore, the contents described in Embodiment 1 can also be applied to secondary battery 1B, except for the description regarding the first resin layer 13 and the second resin layer 23. Furthermore, it can also be applied to connected batteries that have multiple secondary batteries 1B.

[0122] For example, a flat secondary battery 1 in which positive electrode active material layers 12 are located on both sides of the positive electrode current collector 11 and negative electrode active material layers 22 are located on both sides of the negative electrode current collector 21 can be applied to secondary battery 1B. When secondary battery 1B is folded, it may be in the form of secondary battery 1 shown in Figures 2 and 6, or in the form of secondary battery 100 shown in Figure 7. The folded secondary battery 1B (including the form corresponding to secondary battery 100) may be provided with a resin layer that covers the entire outer circumference of secondary battery 1B.

[0123] However, in this embodiment as well, a positive electrode active material layer 12 in which the area of ​​the first opposing surface 122 is larger than the area of ​​the first contact surface 121 may be bonded to the main surface of the positive electrode current collector 11. Also, a negative electrode active material layer 22 in which the area of ​​the second opposing surface 222 is larger than the area of ​​the second contact surface 221 may be bonded to the main surface of the negative electrode current collector 21. Furthermore, in this embodiment as well, as described in Embodiment 2, a configuration comprising one positive electrode active material layer 12 and one negative electrode active material layer 22 may be provided.

[0124] Furthermore, a flat secondary battery 1 without a negative electrode active material layer 22 can be applied to secondary battery 1B. When secondary battery 1B is folded, it may take the form of secondary battery 1 shown in Figures 2 and 6, or the form of secondary battery 100 shown in Figure 7.

[0125] [Embodiment 4] <Module Configuration> A module 400 capable of housing at least one secondary battery will be described. Module 400 may house at least one of the flat secondary batteries 1, 1A, and 1B, or it may house at least one of the secondary batteries 1, 1A, and 1B in a folded state. Module 400 may also house the secondary battery 100 shown in Figure 7.

[0126] In this embodiment, the module 400 is described as housing multiple folded secondary batteries 1 connected to each other on a flat surface 2 (see Figure 2).

[0127] Figure 11 is a perspective view showing an example of module 400. Reference numeral 551 in Figure 11 is a perspective view of module 400 as seen from the third surface 4013, which will be described later, and reference numeral 552 is a perspective view of module 400 as seen from the fourth surface 4014, which will be described later. As shown in Figure 11, module 400 may include a case 401 and a lid 402. The size and shape of module 400 may be determined by the size, shape and connection configuration of the secondary battery housed in module 400.

[0128] The case 401 may be a component that covers a part of the secondary battery 1. The case 401 protects the secondary battery 1 housed in the module 400 from external impacts and the like. The case 401 may also be made of a corrosion-resistant material. The material of the case 401 may be, for example, metal.

[0129] The case 401 may include a first surface 4011, a second surface 4012 facing the first surface 4011, a third surface 4013 connected to the first surface 4011 and the second surface 4012, and a fourth surface 4014 facing the third surface. The first surface 4011, the second surface 4012, the third surface 4013, and the fourth surface 4014 define two openings facing each other. Through these openings, the secondary battery 1 can be inserted into the case 401 and removed from the case 401.

[0130] In this embodiment, the folded secondary battery 1 is located inside the case 401 such that the bent portion 3 (see Figure 2) faces the third surface 4013 and the fourth surface 4014, and the outermost flat portion 2 faces the first surface 4011 and the second surface 4012.

[0131] Furthermore, the case 401 may have a through hole 4015. The through hole 4015 is a member that penetrates the fastening portion 4031 of the external electrode 403, which will be described later.

[0132] The lid 402 may be a component that covers a part of the secondary battery 1. The lid 402 may be a component that covers two openings in the case 401. The connection between the case 401 and the lid 402 defines the external shape of the module 400 and defines the housing space for housing the secondary battery 1. The connection between the case 401 and the lid 402 may also seal the housing space. The lid 402 may be made of a corrosion-resistant material. The material of the lid 402 may be, for example, metal. The lid 402 may be welded to the case 401, for example.

[0133] Figure 12 is a cross-sectional view of module 400 shown in Figure 11, taken along the line XII-XII. Figure 13 is a schematic cross-sectional view showing a part of module 400 shown in Figure 12. As shown in Figure 12, module 400 may include external electrodes 403A, 403B and rigid members 404A, 404B. In the following description, when the external electrodes 403A, 403B are referred to collectively, they will simply be called external electrodes 403. When the rigid members 404A, 404B are referred to collectively, they will simply be called rigid members 404. Also, as shown in Figure 13, module 400 may include a pressurizing member 405.

[0134] The external electrode 403 is electrically connected to the secondary battery 1 and may be an electrode for charging or discharging (extracting current) the secondary battery 1. External electrodes 403A and 403B correspond to external electrodes 201 and 202 shown in Figure 2, respectively. The material of the external electrode 403 may be a metal such as aluminum or copper. The material may differ depending on the individual components of the external electrode 403, which will be described later.

[0135] The size, shape, and position of the external electrodes 403 are determined considering the size, shape, and position of the secondary battery 1 housed in the module 400. In this embodiment, as shown in Figure 12, multiple folded secondary batteries 1 are housed inside the module 400, connected to each other on the planar portion 2. In this state, the external electrodes 403A and 403B are positioned to be electrically connected to the planar portions 2 of the two outermost secondary batteries 1.

[0136] Reference numeral 561 in Figure 14 is a perspective view showing an example of an external electrode 403, and reference numeral 562 is a cross-sectional view taken along the line XIV-XIV showing a part of the external electrode 403 of reference numeral 561. As shown in reference numeral 561, the external electrode 403 may include a fastening portion 4031, a base portion 4032, a flexible portion 4033, and a current collecting portion 4034.

[0137] The fastening portion 4031 is a component that connects the module 400 to an external device. The base portion 4032 is the base of the fastening portion 4031. On the first surface 4011, the fastening portion 4031 and a part of the base portion 4032 protrude to the outside of the module 400. This allows the module 400 to be electrically connected to an external device. Therefore, it becomes possible to charge or discharge the secondary battery 1 via the external electrode 403.

[0138] The flexible portion 4033 is a member that connects the base portion 4032 and the current collector portion 4034, and is a member that has flexibility.

[0139] The current collector 4034 is a component that is electrically connected to the secondary battery 1 housed in the module 400. This enables charging or discharging of the secondary battery 1. In this embodiment, the current collector 4034 is electrically connected to the outermost planar portion 2 of the multiple secondary batteries 1 housed in the module 400.

[0140] The current collector 4034 may also function as a pressurizing unit that pressurizes the secondary battery 1 housed in the module 400. The current collector 4034 may be a member that applies a pressing force to each of the two outermost planar portions 2 described in Embodiment 1. This reduces the possibility of adjacent secondary batteries 1 shifting relative to each other.

[0141] As described above, the position of the external electrode 403 is determined according to the size of the secondary battery 1 housed in the module 400. By determining the position of the current collector 4034 so that it makes contact with the secondary battery 1 housed in the module 400, a pressing force can be applied to the secondary battery 1.

[0142] In this embodiment, the current collector 4034 is described as electrically contacting two planar portions 2 located on the outermost side of the connected secondary batteries 1, but is not limited to this. For example, the current collector 4034 may electrically contact two bent portions 3 located on the outermost side in the thickness direction of the connected secondary batteries 1. The current collector 4034 may contact only the planar portions 2, only the bent portions 3, or both. The contact positions between the current collector 4034 and the secondary battery 1 may differ between the external electrode 403A and the external electrode 403B. That is, the current collector 4034 may function as a pressurizing portion that applies pressure to at least one of the two planar portions 2, or as a pressurizing portion that applies pressure to at least one of the two bent portions 3.

[0143] The current collector 4034 may be plate-shaped. However, the shape of the current collector 4034 may be determined by which part of the secondary battery 1 it contacts.

[0144] The current collector 4034 is in contact with the secondary battery 1 housed in the module 400. The shape of the secondary battery 1 may change when charging or discharging. Therefore, a force associated with this change may be applied to the current collector 4034. The external electrode 403 is connected to the case 401. In this embodiment, as shown by reference numeral 562, the base portion 4032 is connected to the first surface 4011. Therefore, when a force due to a change in the shape of the secondary battery 1 is applied to the current collector 4034, it may be applied to the connection point between the base portion 4032 and the current collector 4034. In this embodiment, since the flexible portion 4033 is located at the connection point, the current collector 4034 can be displaced when such a force is applied to the current collector 4034. That is, the current collector 4034 can be displaced to follow the change in the shape of the secondary battery 1. Therefore, the possibility of damage to the connection point is reduced, and the connection between the base portion 4032 and the current collector 4034 can be maintained.

[0145] As shown by reference numeral 562, the case 401 may be provided with a gasket 406. The gasket 406 is positioned around the base portion 4032 that penetrates the through hole 4015 and is a component that seals the inside of the module 400. In this embodiment, the gasket 406 is positioned so as to sandwich the first surface 4011 that defines the through hole 4015 and is fixed to the first surface 4011 by a fastening member or the like. The gasket 406 may also be welded to the base portion 4032.

[0146] The material of the gasket 406 may be, for example, glass or resin. In this case, the gasket 406 may have the function of electrically insulating the case 401 from the external electrode 403.

[0147] The case 401 does not need to have a gasket 406 in the through hole 4015, as long as the inside of the module 400 can be sealed and the case 401 and the external electrode 403 can be electrically insulated. In this case, the case 401 and the external electrode 403 (in this embodiment, the first surface 4011 and the base portion 4032) may be directly connected. For example, the first surface 4011 and the base portion 4032 may be welded together.

[0148] The rigid member 404 is a member that absorbs forces generated by changes in the shape of the secondary battery 1. The rigid member 404 may be located at a distance from the lid 402. As a result, a space exists between the rigid member 404 and the lid 402. This space may function as a storage area for gas released from the secondary battery 1 housed in the module 400.

[0149] In this embodiment, the rigid member 404 is connected to the first surface 4011. The material of the rigid member 404 may be, for example, metal.

[0150] As shown in Figure 13, the pressurizing member 405 is located between the external electrode 403 and the rigid member 404, and pressurizes the secondary battery 1 housed in the module 400 via the external electrode 403. The pressurizing member 405 may also function as a member that follows the displacement of the external electrode 403 due to changes in the shape of the secondary battery 1. That is, the pressurizing member 405 may function as a member that absorbs the force generated by changes in the shape of the secondary battery 1 via the external electrode 403. The pressurizing member 405 may be, for example, a coil spring, a leaf spring, or a cushioning member.

[0151] Figure 13 illustrates a state in which the pressurizing member 405 is positioned between the external electrode 403B and the rigid member 404B, but a state in which the pressurizing member 405 is positioned between the external electrode 403A and the rigid member 404A can also be illustrated as in Figure 13. Furthermore, in this embodiment, the pressurizing member 405 is positioned between the external electrode 403B and the rigid member 404B, and also between the external electrode 403A and the rigid member 404A, but this is not limited to this. The pressurizing member 405 may be positioned only between the external electrode 403B and the rigid member 404B, or only between the external electrode 403A and the rigid member 404A.

[0152] The rigid member 404 absorbs the force applied to the pressurizing member 405. Furthermore, as described above, the rigid member 404 is spaced apart from the lid 402. Therefore, the possibility of the force being transmitted to the lid 402 causing damage to the connection between the lid 402 and the case 401 can be reduced.

[0153] In this embodiment, an external electrode 403 electrically connected to the current collector 4034 by a fastening portion 4031 has been described, but a rigid member 404 may also have the function of an external electrode 403. In this case, charging or discharging can be performed on the secondary battery 1 housed in the module 400 via the rigid member 404. In this case, the case 401, or the case 401 and lid 402, can have the same potential as the secondary battery 1. Therefore, modules 400 can be electrically connected to each other, for example, like dry cell batteries.

[0154] In this case, the fastening portion 4031 and the base portion 4032 may also be electrically connected to the rigid member 404. The rigid member 404 may be connected to the case 401 (for example, the first surface 4011) via the fastening portion 4031 and the base portion 4032. The current collector portion 4034 may also be connected to the rigid member 404 via the pressurizing member 405. The current collector portion 4034 and the pressurizing member 405 may be displaced in accordance with changes in the shape of the secondary battery 1 housed in the module 400.

[0155] As described above, the base portion 4032 is the base of the fastening portion 4031. On the other hand, the current collector portion 4034 in this embodiment is a plate-shaped member facing the flat portion 2. Therefore, as shown by reference numeral 561 in Figure 14, the connection point between the base portion 4032 and the current collector portion 4034 has a smaller area than the current collector portion 4034. If the thickness of the current collector portion 4034 and the connection point are constant, when the current received by the current collector portion 4034 from the secondary battery 1 flows to the connection point, the resistance at the connection point becomes greater than the resistance at the current collector portion 4034.

[0156] Unlike the current collector 4034, the rigid member 404 can be freely designed in terms of its thickness. Also, the pressurizing member 405 can be placed across the entire surface of both the current collector 4034 and the rigid member 404. Therefore, the resistance in the rigid member 404 caused by the current received by the current collector 4034 from the secondary battery 1 can be made smaller than the resistance at the connection point.

[0157] Furthermore, although this embodiment describes the module 400 as having a rigid member 404, the module 400 does not need to have a rigid member 404 if the possibility of damage to the connection between the case 401 and the lid 402 is low. In this case, the pressurizing member 405 may be located between the current collector 4034 and the lid 402.

[0158] Furthermore, in this embodiment, the first surface 4011 has a through hole 4015, but it is not limited to this, and any of the second to fourth surfaces 4012 to 4014 may have a through hole 4015, or at least one of the two covers 402 may have a through hole 4015. Depending on the positional relationship between the through hole 4015 and the current collector 4034, a conductive member may be positioned between the base portion 4032 connected to the fastening portion 4031 that penetrates the through hole 4015 and the flexible portion 4033 connected to the current collector 4034. The conductive member may be, for example, a metal plate.

[0159] For example, if two through holes 4015 through which each of the fastening portions 4031 of two external electrodes 403 passes are located in one lid 402, the following configuration may be used. In this description of the configuration, the two current collectors 4034 will be referred to as the first current collector 4034 and the second current collector 4034, respectively. Furthermore, the lid 402 on the side of the first current collector 4034 will have two through holes 4015. In this case, the flexible portion 4033 connected to the second current collector 4034 may be connected to the base portion 4032 to which the fastening portion 4031 is connected via a conductive member located along the inner wall of the case 401 (for example, the inner wall on the first surface 4011).

[0160] (Voltage measurement and temperature control of secondary battery) Figure 15 is a perspective view showing an example of module 400, illustrating the control board 407 and heater 408. Figure 16 is a plan view showing a specific example of the control board 407.

[0161] As shown in Figures 15 and 16, the module 400 may include a control board 407, a heater 408, a first connector 409, and a signal line cable 410. The control board 407 may be located on the inner wall of the case 401. In this embodiment, the control board 407 is located on the fourth surface 4014 facing the bent portion 3 of the secondary battery 1 housed in the module 400. The control board 407 may also be located on the third surface 4013. Furthermore, although the control board 407 is located on the inner wall of the case 401, it may also be located on the outside of the case 401, for example, on the outer wall of the case 401, as long as voltage detection and temperature measurement, as described later, are possible.

[0162] As shown in Figure 16, the control board 407 may include an insulating substrate 4071, a voltage detection terminal 4072, a thermistor 4073, an integrated circuit 4074, a second connector 4075, and a signal line 4076. The voltage detection terminal 4072, thermistor 4073, integrated circuit 4074, second connector 4075, and signal line 4076 are located on the insulating substrate 4071.

[0163] The voltage detection terminal 4072 is a component for detecting the voltage of the secondary battery 1 housed in the module 400. The material of the voltage detection terminal 4072 may be metal. The position of the voltage detection terminal 4072 is defined to correspond to the position of the bent portion 3 of the secondary battery 1 housed in the module 400. In this embodiment, it is positioned to contact at least a portion of the bent portion 3 of each of the connected secondary batteries 1.

[0164] Figure 17 is a cross-sectional view of module 400 shown in Figure 11, taken along the line XVII-XVII. Specifically, Figure 17 is a diagram illustrating the positional relationship between the secondary battery 1 and the voltage detection terminal 4072. For the sake of simplicity, Figure 17 shows four folded secondary batteries 1 connected and housed in module 400. Also, the pressurizing member 405, rigid member 404, lid 402, and heater 408 are omitted from the illustration.

[0165] As shown in Figure 17, in the folded state, the flat portions 2 of the secondary battery 1 are connected to each other. Furthermore, in the thickness direction of the multiple connected secondary batteries 1, the first bent portions 3 (bent portions 3 where the positive electrode sheet 10 is located on the outermost side) that include the positive electrode current collector 11 located on the side of the secondary battery 1 are located in the same row. On the other hand, in the same thickness direction, the second bent portion 3 (bent portion 3 where the negative electrode sheet 20 is located on the outermost side) that includes the negative electrode current collector 21 located on the side of the secondary battery 1 is located in the same row on the opposite side from the first bent portion 3.

[0166] In this state, the voltage detection terminal 4072 is positioned on the insulating substrate 4071 so as to face the bent portion 3 having a positive electrode sheet 10 and / or a negative electrode sheet 20 having different potentials. Alternatively, the voltage detection terminal 4072 may be positioned on the insulating substrate 4071 so as to face the current collecting portions 4034 of the external electrodes 403A and 403B. In this case, the voltage detection terminal 4072 does not need to be electrically connected to the bent portion 3 having the positive electrode sheet 10 to which the external electrode 403A is electrically connected, and to the bent portion 3 having the negative electrode sheet 20 to which the external electrode 403B is electrically connected.

[0167] In the example shown in Figure 17, one voltage detection terminal 4072 is in contact with the negative electrode sheet 20 of the second potential region AR2, which has a potential of Vo2; the negative electrode sheet 20 of the third potential region AR3, which has a potential of Vo3; and the negative electrode sheet 20 of the fourth potential region AR4, which has a potential of Vo4. Alternatively, one voltage detection terminal 4072 may be in contact with the current collector 4034 of the external electrode 403A of the first potential region AR1, which has a potential of Vo1; and the current collector 4034 of the external electrode 403B of the fifth potential region AR5, which has a potential of Vo5. In each of the first to fifth potential regions AR1 to AR5, it is sufficient that the voltage detection terminal 4072 is in contact with the bent portion 3 at any position within the region.

[0168] In the example shown in Figure 17, the voltage detection terminal 4072 is located only on the fourth surface 4014 side facing the negative electrode sheet 20. However, the voltage detection terminal 4072 may also be located only on the third surface 4013 side facing the positive electrode sheet 10.

[0169] In this embodiment, the integrated circuit 4074 measures the voltage between two adjacent voltage detection terminals 4072. As shown in Figure 16, one signal line 4076 is electrically connected to the two adjacent voltage detection terminals 4072, and this signal line 4076 is electrically connected to the integrated circuit 4074.

[0170] Furthermore, the voltage detection terminal 4072 may be equipped with a mechanism that follows changes in the shape of the secondary battery 1. For example, the voltage detection terminal 4072 may be equipped with a conductive portion that contacts the secondary battery 1 and a movable mechanism that can move the conductive portion in a direction substantially perpendicular to the surface of the insulating substrate 4071. The movable mechanism may be, for example, an elastic member.

[0171] The thermistor 4073 is an element for measuring the temperature of the secondary battery 1 housed in the module 400 or the temperature of its surroundings. In this embodiment, the thermistor 4073 is electrically connected to the integrated circuit 4074 via a signal line 4076. Therefore, the integrated circuit 4074 can measure the temperature of the secondary battery 1 or the temperature of its surroundings.

[0172] Module 400 may be equipped with, for example, a thermocouple or a radiation thermometer instead of the thermistor 4073. That is, module 400 may be equipped with a temperature measuring member capable of measuring the temperature of the secondary battery 1 housed in module 400 or the temperature of the surrounding area. Furthermore, the temperature measuring member may be located on the outer wall of case 401 or on an insulating member located inside case 401.

[0173] The integrated circuit 4074 is a circuit that performs various control or analysis functions. In this embodiment, the integrated circuit 4074 may measure the voltage of the secondary battery 1 housed in the module 400 based on a signal from the voltage detection terminal 4072. The integrated circuit 4074 may also measure the temperature of the secondary battery 1 or its surroundings based on a signal from the thermistor 4073. Furthermore, the integrated circuit 4074 may control the temperature of the heater 408, which will be described later, based on the measured temperature.

[0174] The second connector 4075 is a signal line terminal for connecting a plurality of signal lines 4076 located on the insulating substrate 4071 to an external terminal located outside the insulating substrate 4071. In this embodiment, the second connector 4075 electrically connects the integrated circuit 4074 to the first connector 409, which is the external terminal.

[0175] The heater 408 is a component that heats the secondary battery 1 housed in the module 400. The heater 408 is electrically connected to the integrated circuit 4074 via a signal line 4076. As shown in Figure 15, the heater 408 may be located on the inner walls of the third surface 4013 and the fourth surface 4014. The heater 408 may be located on the outer walls of the third surface 4013 and the fourth surface 4014, or on either the third surface 4013 or the fourth surface 4014. In addition, the heater 408 may be located on an insulating member located inside the case 401.

[0176] The heater 408 may be provided with a heater protection layer that surrounds the heater 408. The material of the heater protection layer may be, for example, resin. The heater protection layer only needs to be located at least between the secondary battery 1 housed in the module 400 and the heater 408, and between the case 401 and the heater 408. This allows the heater 408 to be electrically insulated from the secondary battery 1 and the case 401.

[0177] The first connector 409 is a signal line terminal for electrically connecting to the second connector 4075 via a signal line cable 410. The first connector 409 may be electrically connected to a connector provided by an external device. The first connector 409, the signal line cable 410, and the second connector 4075 allow signals from the control board 407 to be taken out of the module 400. The first connector 409 may also be mounted on the case 401 so as to seal the inside of the case 401.

[0178] (Another example of the arrangement of the voltage detection terminal) Figure 18 is a diagram illustrating another example of the positional relationship between the secondary battery 1 and the voltage detection terminal 4072. Figure 18 is a cross-sectional view showing an example in which the positional relationship between the secondary battery 1 and the voltage detection terminal 4072 is different from the example shown in Figure 17.

[0179] As shown in Figure 18, in the folded secondary battery 1, the planar portions 2 are connected to each other. In the example of Figure 18, the first bent portion 3 and the second bent portion 3 are located in the same row in two adjacent secondary batteries 1. That is, in the thickness direction of the connected secondary batteries 1, the first bent portion 3 and the second bent portion 3 are located alternately. In other words, in the thickness direction, a row of bent portions in which the first bent portion 3 and the second bent portion 3 are located alternately faces the third surface 4013 and the fourth surface 4014, respectively.

[0180] In the example shown in Figure 18, one voltage detection terminal 4072 is in contact with the negative electrode sheet 20 of the second potential region AR2, the negative electrode sheet 20 of the third potential region AR3, and the negative electrode sheet 20 of the fourth potential region AR4, respectively. However, in the example shown in Figure 18, one potential region is formed by adjacent positive electrode sheets 10 and negative electrode sheets 20 in the thickness direction of the multiple connected secondary batteries 1. Therefore, it is sufficient for the voltage detection terminal 4072 to be in contact with either the positive electrode sheet 10 or the negative electrode sheet 20 in that potential region.

[0181] Furthermore, in the example shown in Figure 18, the potential region excluding both ends of the secondary battery 1 (the second potential region AR2 to the fourth potential region AR4 in the example shown in Figure 18) has a length approximately equal to the length of the two bent portions 3. Also, in the thickness direction of the multiple connected secondary batteries 1, the voltage detection terminals 4072 are alternately located on the third surface 4013 and the fourth surface 4014. Therefore, compared to the case where the secondary batteries 1 are connected as shown in Figure 17, the distance between two adjacent voltage detection terminals 4072 can be made larger. As a result, the design of the size and arrangement of the voltage detection terminals 4072 becomes easier.

[0182] <Other Module Components> In addition, module 400 may include the following components, for example.

[0183] For example, module 400 may have an insulating member inside. The insulating member may be located between, for example, two of the following members: - Between case 401 and lid 402 and secondary battery 1 housed in module 400. - Between secondary battery 1 and secondary battery 1. - Between secondary battery 1 and heater 408. - Between heater 408 and case 401. - Between at least a part of fastening portion 4031, base portion 4032 and flexible portion 4033 and case 401. - Between current collector portion 4034 and rigid member 404. - Between current collector portion 4034 and pressurizing member 405.

[0184] For example, module 400 may be equipped with a burst valve inside. This allows the internal pressure of module 400 to be controlled so that it does not rise above a certain value.

[0185] For example, the module 400 may have a function to release gas inside it to the outside of the module 400. To realize this function, for example, the case 401 or lid 402 may have a through hole that connects the inside and outside of the module 400. For example, when the secondary battery 1 is housed in the module 400 and the secondary battery 1 is performed for the first time (pre-charge), gas is released from the secondary battery 1. By having a through hole in the case 401, the gas generated during the first charge can be released to the outside of the module 400 through the through hole. If the through hole is used to release gas generated during the first charge to the outside of the module 400, the through hole may be closed after the first charge has been performed.

[0186] For example, module 400 may be equipped with a cooling member. The material of the cooling member may be a metal such as aluminum. The cooling member may be in the form of a plate. The cooling member may connect, for example, case 401 or lid 402 to the secondary battery 1 housed in module 400.

[0187] For example, module 400 may also be equipped with a handle. The handle may be located on a part of the outer wall of case 401 or lid 402. The handle makes it easier to carry module 400.

[0188] Alternatively, for example, adhesive may be located between the case 401 and / or the lid 402 and the secondary battery 1 housed in the module 400. The adhesive can be used to secure the secondary battery 1 to the case 401 and / or the lid 402.

[0189] For example, module 400 may also include a battery management system (BMS). The BMS may perform charge and discharge control for the secondary battery 1 and balancing control between the secondary batteries 1. The BMS may also detect leakage from the secondary battery 1 by monitoring voltage fluctuations of the secondary battery 1. If leakage is detected, the BMS may stop the charge and discharge operation of the secondary battery 1. Furthermore, during balancing control, the BMS may perform discharge control for the dischargeable secondary battery 1 via a resistor provided in the BMS, or it may perform discharge control for the secondary battery 1 via a heater 408. The BMS may be electrically connected to, for example, an integrated circuit 4074. The BMS may be located inside the case 401 or outside the case 401.

[0190] For example, module 400 may also include a BMS holder for holding the BMS. The BMS holder may be located inside or outside the case 401.

[0191] For example, module 400 may also include fastening members for securing module 400 to external equipment. The fastening members may be located on the outer wall of case 401 and / or lid 402. This secures module 400 to external equipment and improves the seismic and impact resistance of module 400.

[0192] For example, module 400 may also be equipped with a fuse. It may be located outside case 401. The fuse may be electrically connected to module 400 via a signal cable or the like. The fuse can interrupt the current when a large current flows through the signal cable or the like. If module 400 is equipped with a burst valve, the burst valve may also function as a fuse.

[0193] For example, module 400 may also be equipped with a circuit breaker. The circuit breaker may be located outside the case 401. The circuit breaker may be electrically connected to module 400 via a signal cable or the like. This allows the power to module 400 to be turned on and off.

[0194] For example, the module 400 may also have a connection section for electrically connecting to a power conditioner. The connection section may be located outside the case 401. The connection section may be electrically connected to the module 400 via a signal cable or the like. The connection section allows the module 400 to be electrically connected to the power conditioner.

[0195] For example, module 400 may also have feet. The feet may be located on the outer wall of case 401 and / or lid 402.

[0196] For example, module 400 may also be equipped with an earthing member. The earthing member may be an earthing terminal or an earthing cable. The earthing member may be located outside the case 401. The earthing member may be electrically connected to module 400 via a signal line cable or the like.

[0197] For example, module 400 may also include a thermal management system. The thermal management system may be electrically connected to, for example, integrated circuit 4074. The thermal management system may be located inside or outside case 401. The thermal management system enables temperature control of the secondary battery 1.

[0198] Alternatively, the modules 400 may be electrically connected to each other. For example, the outer walls of the modules 400 may be electrically connected to each other, similar to a dry cell battery.

[0199] The module 400 may also further include a balance circuit, a heater, various monitors, and signal lines. Examples of various monitors and signal lines include a thermistor, a voltage monitor, and wiring related thereto. Alternatively, the battery pack may consist of the module 400, a heating control circuit for controlling heating by the heater, a battery management unit (BMU) having output control and safety functions, and an outer casing housing them. The BMU may have the same functions as the control board 407 described above. Furthermore, the module 400 constituting the battery pack does not necessarily have to include the control board 407.

[0200] <Configuration of the external device on which the module is mounted> The external device on which the module 400 is mounted may include, for example, the following components. These components may be located, for example, in part of the housing of the external device.

[0201] For example, the external device may be equipped with a gasket. The gasket may be located, for example, in a part of the enclosure that defines the location where the module 400 is mounted (i.e., the mounting location of the module 400) in the external device. This reduces the possibility of liquid or dust entering the mounting location of the module 400.

[0202] For example, the external equipment may also be equipped with a gas duct. This allows the gas flow path to be specified within the external equipment.

[0203] For example, the external equipment may be equipped with a cleavage valve. The cleavage valve may be located in part of the housing that defines the mounting location of the module 400. For example, the external equipment may be equipped with a fire extinguishing agent. For example, the external equipment may be equipped with a fire spread reduction member that reduces the possibility of fire spreading from the module 400 to the components of the external equipment and / or from the components of the external equipment to the module 400.

[0204] For example, the external equipment may include a chassis. In this case, the external equipment may be, for example, an electric vehicle. The module 400 may be located in part of the chassis. In this case, the possibility of damage to the module 400 can be reduced.

[0205] For example, the external device may also be equipped with a total voltage connector. The total voltage connector is a connector for electrically connecting power lines from multiple modules 400 mounted on the external device to the electronic components of the external enclosure.

[0206] For example, the external device may also be equipped with a signal line connector. The signal line connector is a connector for electrically connecting signal line cables from multiple modules 400 mounted on the external device to the electronic components of the external enclosure.

[0207] The total voltage connector and signal line connector may be located in a part of the housing that defines the mounting location of module 400. This reduces the possibility of liquid or dust entering the mounting location of module 400.

[0208] For example, the external equipment may include a junction box and busbars to enable charge and discharge control of the secondary battery 1 housed in the module 400. The external equipment may also include insulating members to electrically isolate the components, including the module 400, from each other.

[0209] For example, the external equipment may have a rack for mounting the module 400. If the external equipment does not have a rack, multiple modules 400 may be arranged side by side on a plane or stacked on top of each other at the mounting location of the module 400.

[0210] [Embodiment 5] Figure 21 is a cross-sectional view showing an example of a unit cell 1C according to Embodiment 5. Multiple unit cells 1C are combined to form a secondary battery 1D, which will be described later. In the unit cell 1C, a single positive electrode active material layer 12 is surrounded by a first resin layer 13. Also, a single negative electrode active material layer 22 is surrounded on both sides by a second resin layer 23.

[0211] In unit cell 1C, the positive electrode current collector 11 extends in one direction relative to the positive electrode active material layer 12 in a plan view. The negative electrode current collector 21 extends in the opposite direction relative to the negative electrode active material layer 22 in a plan view to the direction in which the positive electrode current collector 11 extends.

[0212] Figure 27 shows another example of the unit cell 1C according to Embodiment 5, different from that shown in Figure 21. Figure 27 shows a plan view, a side view, and a cross-sectional view of the unit cell 1C. As shown in Figure 27, in the unit cell 1C, the first resin layer 13 may be located outside the positive electrode current collector 11. Also, the second resin layer 23 may be located outside the negative electrode current collector 21.

[0213] In this case, the first resin layer 13 may include a conductive member 13a. Also, a portion of the second resin layer 23 may include a conductive member 23a. The conductive members 13a and 23a may overlap at least a portion of the positive electrode current collector 11 and the negative electrode current collector 21 in a plan view. This makes it possible to extract power from a unit cell 1C in which the first resin layer 13 is located outside the positive electrode current collector 11 and the second resin layer 23 is located outside the negative electrode current collector 21.

[0214] The materials forming the conductive members 13a and 23a may be conductive resin or metal. In particular, the material forming the conductive member 13a may be aluminum, and the material forming the conductive member 23a may be copper.

[0215] Figure 22 is a cross-sectional view showing an example of a secondary battery 1D according to Embodiment 5. In the example shown in Figure 22, the secondary battery 1D is a stack cell composed of five unit cells 1C. However, the number of unit cells 1C that constitute the stack cell as a secondary battery 1D is not limited to five.

[0216] The number of unit cells 1C that constitute the stack cell as a secondary battery 1D may be odd. Furthermore, adjacent unit cells 1C may be connected to each other with the same positive electrode current collector 11 and negative electrode current collector 21. As a result, the current collectors located at both ends of the secondary battery 1D will be different from the positive electrode current collector 11 and the negative electrode current collector 21.

[0217] In the example shown in Figure 22, the positive electrode current collectors 11 of each unit cell 1C are ultrasonically welded to each other at the portion extending into the positive electrode active material layer 12. Similarly, the negative electrode current collectors 21 are ultrasonically welded to each other at the portion extending into the negative electrode active material layer 22. In Figure 22, the portions where the positive electrode current collectors 11 are ultrasonically welded to each other and the portions where the negative electrode current collectors 21 are ultrasonically welded to each other are indicated by dashed lines. The positive electrode current collectors 11 and the negative electrode current collectors 21 may be joined to each other by methods other than ultrasonic welding.

[0218] Furthermore, in the example shown in Figure 22, adjacent unit cells 1C are joined together such that the same positive electrode current collector 11 and negative electrode current collector 21 are in surface contact with each other. Therefore, the unit cells 1C are connected in parallel with each other.

[0219] Figure 23 is a cross-sectional view showing an example of a secondary battery module 1E according to Embodiment 5. In the example shown in Figure 23, the secondary battery module 1E is composed of three secondary batteries 1D. However, the number of secondary batteries 1D constituting the secondary battery module 1E is not limited to this.

[0220] In the example shown in Figure 23, each secondary battery 1D has one positive electrode current collector 11 and one negative electrode current collector 21 at both ends. In the secondary battery module 1E, the main surface of the positive electrode current collector 11 of one secondary battery 1D and the main surface of the negative electrode current collector 21 of an adjacent secondary battery 1D may be connected in a state of surface contact with each other. In this case, the secondary battery module 1E has a structure in which multiple secondary batteries 1D are connected in series. Alternatively, the connection between secondary batteries 1D may be such that the main surface of the positive electrode current collector 11 of one secondary battery 1D and the main surface of the positive electrode current collector 11 of an adjacent secondary battery 1D are connected in a state of surface contact with each other.

[0221] [Embodiment 6] Figure 24 is a cross-sectional view showing an example of a secondary battery 1F according to Embodiment 6. The secondary battery 1F differs from the secondary battery 1 in that the positive electrode current collector 11 and the first resin layer 13 are formed to be longer than the bent portion 3 in the outermost planar portion 2U1.

[0222] In the secondary battery 1F, the positive electrode current collector 11 and the first resin layer 13 of the flat portion 2U1 cover a part of the bent portion 3. At this time, the first resin layer 13 contacts the negative electrode current collector 21 that is exposed to the outside at the bent portion 3. Although not shown, in the flat portion 2L1, the negative electrode current collector 21 and the second resin layer 23 are formed to be longer than the bent portion 3 and cover a part of the bent portion 3. At this time, the second resin layer 23 contacts the positive electrode current collector 11 that is exposed to the outside at the bent portion 3. Therefore, when the bent portion 3 is compressed from a direction parallel to the main surfaces of the positive electrode current collector 11 and the negative electrode current collector 21, the possibility of the positive electrode current collector 11 and the negative electrode current collector 21 coming into contact with each other and short-circuiting is reduced.

[0223] [Embodiment 7] Figure 25 is a cross-sectional view showing an example of a secondary battery module 1G according to Embodiment 7. The secondary battery module 1G is composed of three secondary batteries 1, each having an even number of planar sections 2. All three secondary batteries 1 are configured such that the positive electrode current collector 11 is located in the outermost layer.

[0224] The negative electrode current collectors 21 of the three secondary batteries 1 are connected to each other by a conductor 50a. The positive electrode current collectors 11 of the three secondary batteries 1 are connected to each other by a conductor 50b.

[0225] The conductors 50a and 50b may each be, for example, part of the inner wall of the case housing the secondary battery module 1G. In this case, no additional members are required to connect the negative electrode current collectors 21 to each other, and the installation space for the secondary battery module 1G can be reduced.

[0226] Furthermore, the secondary battery module 1G may also include metal foil separate from the case that connects the negative electrode current collectors 21 or the positive electrode current collectors 11 of adjacent secondary batteries 1. In this case as well, the secondary batteries 1 can be connected in parallel within the secondary battery module 1G.

[0227] [Embodiment 8] Figure 26 is a cross-sectional view showing an example of a secondary battery module 1H according to Embodiment 8. The secondary battery module 1H comprises two secondary batteries 1J. The secondary batteries 1J are provided with an odd number of planar sections 2. Furthermore, in the secondary batteries 1J, the size of the planar sections 2U1 and 2L1 located at the outermost ends is half the size of the other planar sections 2. Therefore, in the secondary batteries 1J, both the positive electrode current collector 11 and the negative electrode current collector 21 are exposed to the outside at both ends. Consequently, parallel connection of secondary batteries 1J, each having an odd number of planar sections 2, becomes easy.

[0228] In this case, a step difference occurs at both ends of the secondary battery 1J between the areas where the flat sections 2U1 and 2L1 are present and the areas where they are not. In the secondary battery 1J, a conductive spacer may be placed in the area where the flat sections 2U1 and 2L1 are absent. This eliminates the step difference at both ends of the secondary battery 1J. Therefore, when applying pressure to the flat sections 2U1 and 2L1, the pressure can be applied uniformly.

[0229] Furthermore, in the planar portions 2U1 and 2L1, the first resin layer 13 and the second resin layer 23 may be formed to be longer than the positive electrode current collector 11 and the negative electrode current collector 21. This allows for a sufficiently wide distance between the positive electrode current collector 11 and the negative electrode current collector 21, ensuring insulation.

[0230] Furthermore, the flat sections 2U1 and 2L1 do not necessarily have to include the positive electrode active material layer 12 and the negative electrode active material layer 22. This makes it possible to reduce the step difference at both ends of the secondary battery 1J.

[0231] [Summary] A secondary battery according to Embodiment 1 of the present disclosure is a secondary battery comprising: a positive electrode sheet having a positive electrode current collector having a first side surface and a first main surface and a second main surface connected to the first side surface; and at least one positive electrode active material layer located on at least one of the first main surface and the second main surface; a negative electrode sheet having a negative electrode current collector having a second side surface and a third main surface and a fourth main surface connected to the second side surface; and a separator located between the positive electrode sheet and the negative electrode sheet.

[0232] In the secondary battery according to Embodiment 2 of the present disclosure, in Embodiment 1, the negative electrode sheet is located on at least one of the third main surface and the fourth main surface and has at least one negative electrode active material layer facing at least one positive electrode active material layer.

[0233] A secondary battery according to embodiment 3 of the present disclosure, in embodiment 1 or 2, is folded and has at least one bent portion and a plurality of planar portions connected to the bent portion and adjacent to each other.

[0234] A secondary battery according to Embodiment 4 of the present disclosure, in Embodiment 2, or Embodiment 3 which references Embodiment 2, wherein the positive electrode sheet comprises a plurality of positive electrode active material layers spaced apart from each other, the negative electrode sheet comprises a plurality of negative electrode active material layers spaced apart from each other, and each of the plurality of positive electrode active material layers faces each of the plurality of negative electrode active material layers.

[0235] A secondary battery according to Embodiment 5 of the present disclosure, in Embodiment 2, Embodiment 3 relating to Embodiment 2, or Embodiment 4, the positive electrode sheet comprises a first resin layer located around the positive electrode active material layer along the outer edge of the positive electrode current collector in a plan view on either the first main surface or the second main surface, and the negative electrode sheet comprises a second resin layer located around the negative electrode active material layer along the outer edge of the negative electrode current collector in a plan view on either the third main surface or the fourth main surface.

[0236] A secondary battery according to embodiment 6 of the present disclosure, in embodiment 4, the positive electrode sheet comprises a first resin layer located on either the first main surface or the second main surface, positioned around the plurality of positive electrode active material layers along the outer edge of the positive electrode current collector in a plan view, and positioned between two adjacent positive electrode active material layers, and the negative electrode sheet comprises a second resin layer located on either the third main surface or the fourth main surface, positioned around the plurality of negative electrode active material layers along the outer edge of the negative electrode current collector in a plan view, and positioned between two adjacent negative electrode active material layers.

[0237] A secondary battery according to Embodiment 7 of the present disclosure, in Embodiment 3 which references Embodiment 2, or in any of Embodiments 5 to 6 which reference Embodiment 3, wherein the positive electrode sheet comprises a plurality of positive electrode active material layers spaced apart from each other, the negative electrode sheet comprises a plurality of negative electrode active material layers spaced apart from each other, each of the plurality of positive electrode active material layers faces each of the plurality of negative electrode active material layers, and the bent portion includes a first region located between two adjacent positive electrode active material layers on either the first main surface or the second main surface, and a second region located between two adjacent negative electrode active material layers on either the third main surface or the fourth main surface.

[0238] A secondary battery according to embodiment 8 of the present disclosure, in embodiment 2, embodiment 3 referencing embodiment 2, or any of embodiments 4 to 7, wherein the positive electrode active material layer has a first contact surface that contacts the positive electrode current collector and a first opposing surface that faces the separator, the area of ​​which the first opposing surface is larger than the area of ​​the first contact surface, and the negative electrode active material layer has a second contact surface that contacts the negative electrode current collector and a second opposing surface that faces the separator, the area of ​​which the second opposing surface is larger than the area of ​​the second contact surface.

[0239] A connected battery according to aspect 9 of the present disclosure is a connected battery comprising a plurality of secondary batteries described in any of aspects 4 to 8, which reference aspects 3, 2 and 3, wherein the planar portions of two adjacent secondary batteries are connected to each other.

[0240] In the connected battery according to embodiment 10 of the present disclosure, in embodiment 9, each of the plurality of secondary batteries is provided with an odd number of planar portions as the plurality of planar portions.

[0241] [Additional Notes] The inventions described in this disclosure have been explained based on the drawings and embodiments. However, the inventions described in this disclosure are not limited to the embodiments described above. That is, the inventions described in this disclosure can be modified in various ways within the scope shown in this disclosure, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the inventions described in this disclosure. In other words, it should be noted that it is easy for those skilled in the art to make various modifications or alterations based on this disclosure. Furthermore, it should be noted that these modifications or alterations are included in the scope of this disclosure.

[0242] 1, 1A, 1B, 1D, 1F, 1J Secondary battery 2 Flat section 3 Bent section 5 First region 6 Second region 10, 10A, 10B Positive electrode sheet 11 Positive electrode current collector 12 Positive electrode active material layer 13 First resin layer 20, 20A, 20B Negative electrode sheet 21 Negative electrode current collector 22 Negative electrode active material layer 23 Second resin layer 30 Separator 111 First main surface 112 Second main surface 113 First side surface 121 First contact surface 122 First opposing surface 200, 200A, 200B Connected battery 211 Third main surface 212 Fourth main surface 213 Second side surface 221 Second contact surface 222 Second opposing surface

Claims

1. A secondary battery comprising: a positive electrode sheet having a positive electrode current collector having a first side surface and a first main surface and a second main surface connected to the first side surface, and at least one positive electrode active material layer located on at least one of the first main surface and the second main surface; a negative electrode sheet having a negative electrode current collector having a second side surface and a third main surface and a fourth main surface connected to the second side surface, and at least one negative electrode active material layer located on at least one of the third main surface and the fourth main surface and facing at least one positive electrode active material layer; and a separator located between the positive electrode sheet and the negative electrode sheet.

2. The secondary battery according to claim 1, wherein the positive electrode active material layer has a first opposing surface facing the separator, the area of ​​the separator is larger than the area of ​​the first opposing surface, and the separator covers the entire first opposing surface, and the negative electrode active material layer has a second opposing surface facing the separator, the area of ​​the separator is larger than the area of ​​the second opposing surface, and the separator covers the entire second opposing surface.

3. The secondary battery according to claim 1 or 2, wherein the positive electrode sheet comprises a first resin layer located around the positive electrode active material layer along the outer edge of the positive electrode current collector in a plan view on either the first main surface or the second main surface, and the negative electrode sheet comprises a second resin layer located around the negative electrode active material layer along the outer edge of the negative electrode current collector in a plan view on either the third main surface or the fourth main surface.

4. The secondary battery according to claim 3, wherein the separator has, in a plan view, a region that overlaps with the first resin layer and a region that overlaps with the second resin layer, the positive electrode active material layer is surrounded in a plan view by the region where the separator and the first resin layer overlap, and the negative electrode active material layer is surrounded in a plan view by the region where the separator and the second resin layer overlap.

5. The secondary battery according to claim 3 or 4, wherein the first resin layer has through holes in a part of its outer peripheral region that penetrate between the positive electrode active material layer and the outer edge of the positive electrode sheet, and the second resin layer has through holes in a part of its outer peripheral region that penetrate between the negative electrode active material layer and the outer edge of the negative electrode sheet.

6. The secondary battery according to any one of claims 1 to 5, wherein the secondary battery is folded and has at least one bent portion and a plurality of planar portions connected to the bent portion and adjacent to each other.

7. The secondary battery according to any one of claims 1 to 6, wherein the positive electrode sheet comprises a plurality of positive electrode active material layers spaced apart from each other, and each of the plurality of positive electrode active material layers faces the negative electrode active material layer.

8. The secondary battery according to claim 7, wherein the negative electrode sheet comprises a plurality of negative electrode active material layers spaced apart from each other, and each of the plurality of positive electrode active material layers faces each of the plurality of negative electrode active material layers.

9. The secondary battery according to claim 8, wherein the positive electrode sheet comprises a first resin layer located on either the first main surface or the second main surface, positioned around the plurality of positive electrode active material layers along the outer edge of the positive electrode current collector in a plan view, and positioned between two adjacent positive electrode active material layers, and the negative electrode sheet comprises a second resin layer located on either the third main surface or the fourth main surface, positioned around the plurality of negative electrode active material layers along the outer edge of the negative electrode current collector in a plan view, and positioned between two adjacent negative electrode active material layers.

10. The secondary battery according to claim 6, wherein the positive electrode sheet comprises a plurality of positive electrode active material layers spaced apart from each other, the negative electrode sheet comprises a plurality of negative electrode active material layers spaced apart from each other, each of the plurality of positive electrode active material layers faces each of the plurality of negative electrode active material layers, and the bent portion includes a first region located between two adjacent positive electrode active material layers on either the first main surface or the second main surface, and a second region located between two adjacent negative electrode active material layers on either the third main surface or the fourth main surface.

11. The secondary battery according to any one of claims 1 to 10, wherein an insulating layer is provided between the positive electrode current collector and the negative electrode current collector.

12. A connected battery comprising a plurality of secondary batteries as described in claim 6, wherein the planar portions of two adjacent secondary batteries are connected to each other.

13. The connected battery according to claim 12, wherein each of the plurality of secondary batteries comprises an odd number of planar sections as the plurality of planar sections.

14. The connected battery according to claim 12 or 13, wherein the plurality of secondary batteries include a first secondary battery and a second secondary battery adjacent to each other, and the main surface of the positive electrode current collector or the negative electrode current collector of the first secondary battery and the main surface of the positive electrode current collector or the negative electrode current collector of the second secondary battery are connected in surface contact with each other.

15. A battery pack comprising a connected battery according to any one of claims 12 to 14.

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