Secondary battery

Abstract

Provided is a secondary battery that can improve construction efficiency. The secondary battery has an electrode laminate in which electrode elements are laminated in a sheet shape, and an exterior body that houses the electrode laminate inside; the exterior body has a cylindrical laminate film exterior body that covers at least both end surfaces in the lamination direction of the electrode laminate and a pair of opposing side surfaces, and an inner cover that is disposed at an opening of the laminate film exterior body; the inner cover has a protruding portion that extends from an outer peripheral portion thereof toward the interior of the exterior body, and at least a portion of the electrode laminate is present in a region surrounded by the protruding portion; in the lamination direction, the thickness of the inner cover is smaller than the thickness of the electrode laminate; the outer peripheral portion of the inner cover and the laminate film exterior body that overlaps the outer peripheral portion of the inner cover are joined, thereby sealing the electrode laminate inside the exterior body.

Description

Technical Field

[0001] This invention relates to secondary batteries. Background Technology

[0002] Previously, secondary batteries have been developed that consist of electrode elements and an outer casing housing them. The outer casing is typically made of materials such as aluminum cans or laminated films. In the case of a laminated film, the electrode elements are sealed inside the outer casing by thermal fusion. Patent documents 1-3, for example, disclose batteries using laminated film outer casings.

[0003] Prior technology literature

[0004] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2001-283798

[0006] [Patent Document 2] Japanese Patent Application Publication No. 2015-116706

[0007] [Patent Document 3] Japanese Patent Application Publication No. 2013-131427 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] In the technologies described in Patent Documents 1-3, an outer casing with two overlapping laminated films is used to house electrode elements. The outer periphery of the outer casing is then thermally fused together to create a battery in which the electrode elements are sealed inside the outer casing. In such batteries, a thermally fused sealing portion exists at the outer periphery. To meet predetermined conditions such as strength and moisture permeability, the sealing portion requires a certain sealing width. Therefore, this becomes a significant factor reducing the structural efficiency of the battery.

[0010] Therefore, in view of the above facts, the purpose of this disclosure is to provide a secondary battery that can improve construction efficiency.

[0011] Methods for solving problems

[0012] As a means to solve the above-mentioned problems, this disclosure provides a secondary battery having an electrode stack having stacked sheet-like electrode elements and an outer casing housing the electrode stack inside; the outer casing has a cylindrical laminated film outer casing covering at least two end faces and a pair of opposing side faces of the electrode stack in the stacking direction, and an inner cover disposed in an opening of the laminated film outer casing; the inner cover has a protrusion extending from its outer periphery into the interior of the outer casing, and at least a portion of the electrode stack is present in the area surrounded by the protrusion; in the stacking direction, the thickness of the inner cover is smaller than the thickness of the electrode stack; the outer periphery of the inner cover and the laminated film outer casing overlapping the outer periphery of the inner cover are joined, thereby sealing the electrode stack inside the outer casing.

[0013] In the aforementioned secondary battery, the electrode laminate may have a laminate of a current collector, a positive electrode layer, an electrolyte layer, and a negative electrode layer, and an electrode terminal connected to the current collector; the inner cover has a through hole through which the power supply terminal passes, and the electrode terminal passes through the through hole and protrudes outward; in the area sandwiched by the protrusion, the current collector and the electrode terminal are connected. Alternatively, at least a portion of the protrusion may have a gently sloping concave shape. Furthermore, the laminated film outer casing is formed by molding a single laminated film into a cylindrical shape.

[0014] Invention Effects

[0015] The secondary battery disclosed herein can improve structural efficiency. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a secondary battery 100.

[0017] Figure 2 This is a cross-sectional view of a case where multiple secondary batteries 100 are stacked.

[0018] Figure 3 (A) is a top view of a conventional secondary battery. Figure 3 (B) is a top view of the secondary battery 100.

[0019] Figure 4 This is an example of a traditional method for manufacturing secondary batteries.

[0020] Figure 5 This is an example of a manufacturing method for a secondary battery 100.

[0021] Figure 6 This is a cross-sectional view of a conventional secondary battery (top) and secondary battery 100 (bottom) focusing on the electrode terminal side.

[0022] Figure 7 (A) is a schematic diagram of the laminated outer casing 21 with the sealing part S bent to the side. Figure 7(B) is a schematic diagram of the laminated outer casing 21 with side bonding.

[0023] Figure 8 The top view (top), front view (bottom left), and side view (bottom right) of the inner cover 22 are shown. Figure 8 (A) is a diagram of the inner cover 22 disposed on the side where the electrode terminal 12 is located. Figure 8 (B) is a diagram of the inner cover 22 disposed on the side where the electrode terminal 12 is not provided.

[0024] [Label Explanation]

[0025] 10 Electrode Laminates

[0026] 11-layered structure

[0027] 12 electrode terminals

[0028] 12a Positive extreme particle

[0029] 12b negative extreme particle

[0030] 20 outer body

[0031] 21-Laminated Outer Pack

[0032] 21a Opening

[0033] 22 Inner Lid

[0034] 22a Through hole

[0035] 22b Protrusion

[0036] Part 22c

[0037] Part 22d

[0038] 22e concave part (concave shape)

[0039] 22f Bottom edge

[0040] 22g hypotenuse

[0041] R constraint plate

[0042] S Sealing part

[0043] C Connection part Detailed Implementation

[0044] The secondary battery disclosed herein is characterized by an electrode stack having laminated sheet-like electrode elements and an outer casing housing the electrode stack therein; the outer casing has a cylindrical laminated film outer casing covering at least two end faces and a pair of opposing side faces of the electrode stack in the stacking direction, and an inner cover disposed in the opening of the laminated film outer casing; the inner cover has a protrusion extending from its outer periphery into the interior of the outer casing, and at least a portion of the electrode stack is present in the area surrounded by the protrusion; in the stacking direction, the thickness of the inner cover is smaller than the thickness of the electrode stack; the electrode stack is sealed inside the outer casing by the engagement of the outer periphery of the inner cover and the laminated film outer casing overlapping the outer periphery of the inner cover.

[0045] The secondary battery disclosed herein has an inner cover with a predetermined protrusion on its outer periphery. At least a portion of an electrode laminate is located in the area surrounded by the protrusion, and the outer periphery of the inner cover and the laminated film outer casing are joined together. That is, the area surrounded by the protrusion overlaps with the joined portion (sealing portion), and at least a portion of the electrode laminate is located in this area. Therefore, the secondary battery of this disclosure utilizes the interior of the sealing portion, which was previously not effectively usable, thereby improving construction efficiency. Furthermore, by improving construction efficiency, the volumetric energy density of the battery can also be increased.

[0046] Hereinafter, the secondary battery of this disclosure will be described in detail using a secondary battery 100 as one embodiment. Figure 1 This is an overview diagram of a secondary battery (model 100). Figure 1 For convenience, the secondary battery 100 with the inner cover 22 removed is shown in the image. Figure 2 This is a cross-sectional view of a case where multiple secondary batteries 100 are stacked.

[0047] like Figure 1 , Figure 2 As shown, the secondary battery 100 has an electrode stack 10 with stacked sheet-like electrode elements and an outer casing 20 that houses the electrode stack 10 inside.

[0048] <Electrode Stack 10>

[0049] The electrode stack 10 comprises a stack 11 consisting of a positive current collector, a positive electrode layer, an electrolyte layer, a negative electrode layer, and a negative current collector stacked sequentially, as well as electrode terminals 12. The aforementioned electrode elements refer to the positive current collector, the positive electrode layer, the electrolyte layer, the negative electrode layer, and the negative current collector.

[0050] The number of electrode elements stacked in the laminate 11 is not particularly limited and can be appropriately set according to the desired battery performance. Preferably, a laminate 11 is used in which multiple positive current collectors, positive electrode layers, electrolyte layers, negative electrode layers, and negative current collectors are stacked respectively.

[0051] Known metal foils can be used as both positive and negative current collectors. Examples include metal foils made of Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, and stainless steel.

[0052] The positive electrode layer includes at least a positive electrode composite material layer. As for the positive electrode active material, there are no particular limitations as long as it is a positive electrode active material that can be used in lithium-ion all-solid-state batteries. Examples include lithium cobalt oxide, lithium nickel oxide (NCA-based active material), lithium manganese oxide, and lithium nickel cobalt manganese oxide. Furthermore, the positive electrode layer may arbitrarily contain a solid electrolyte, a conductive additive, or a binder. Examples of solid electrolytes include oxide solid electrolytes and sulfide solid electrolytes. Examples of conductive additives include carbon materials such as acetylene black, Ketjen black, and fumed carbon fiber (VGCF). Examples of binders include butadiene rubber (BR), butene rubber (IIR), and polyvinylidene fluoride (PVdF). The content of these additives in the positive electrode layer and the thickness of the positive electrode layer can remain the same as before.

[0053] The electrolyte layer includes at least a solid electrolyte. There are no particular limitations on the type of solid electrolyte, as long as it is suitable for use in lithium-ion all-solid-state batteries. For example, the same type of electrolyte used in the positive electrode layer can be used. Furthermore, the electrolyte layer may arbitrarily include a binder. The type of binder can be the same as that used in the positive electrode layer. The content of these binders in the electrolyte layer and the thickness of the electrolyte layer can remain the same as before.

[0054] The negative electrode layer includes at least a negative electrode active material. As for the negative electrode active material, there are no particular limitations as long as it can be used in lithium-ion all-solid-state batteries. Examples include metallic active materials such as Li and Si, carbon active materials such as graphite, and Li₄Ti₅O₂. 12 The active material is an oxide. Additionally, the negative electrode layer can arbitrarily contain a solid electrolyte, conductive additives, or a binder. The types of solid electrolyte, conductive additives, and binders can be the same as those used for the positive electrode layer. Their content in the negative electrode layer and the thickness of the negative electrode layer can remain the same as before.

[0055] The manufacturing methods for the positive electrode layer, electrolyte layer, and negative electrode layer are not particularly limited and can be employed using known methods. For example, in the case of manufacturing the positive electrode layer, the material constituting the positive electrode layer is mixed with a solvent to form a slurry, which is then applied to a substrate or a positive current collector and dried to manufacture the positive electrode layer. The electrolyte layer and negative electrode layer can also be manufactured using the same methods. Then, the positive current collector, positive electrode layer, electrolyte layer, negative electrode layer, and negative current collector are sequentially laminated to form a laminate 11.

[0056] Electrode terminals 12 are used to electrically connect the laminate 11 to external devices. For example... Figure 1 As shown, the electrode stack 10 has two electrode terminals 12 (positive terminal 12a and negative terminal 12b), with the positive terminal 12a connected to a positive current collector and the negative terminal 12b connected to a negative current collector. Furthermore, each electrode terminal 12 protrudes outward through a through-hole 22a in one inner cover 22. Known metallic materials can be used as the material for the electrode terminals 12.

[0057] <Exterior body 20>

[0058] The outer casing 20 has a cylindrical laminated film outer casing 21 covering two end faces and a pair of opposing side faces of the electrode laminate 10 in the lamination direction, and an inner cover 22 disposed in the opening 21a of the laminated film outer casing 21. Furthermore, the inner cover 22 has a protrusion 22b extending from its outer periphery into the interior of the outer casing 20, and at least a portion of the electrode laminate 10 is located in the area surrounded by the protrusion 22b. By employing such an outer casing 20, the secondary battery 100 can improve its structural efficiency.

[0059] Here, the "side surface" of the electrode stack 10 refers to the surface formed by the outer edge of the stacked electrode elements. Furthermore, in this specification, the stacking direction of the electrode stack 10 is referred to as the stacking direction, the direction along the long side as the long side direction, and the direction along the short side as the short side direction. In this case, the protrusion 22b protrudes in the long side direction. At this time, "the protrusion 22b extending from the outer periphery of the inner cover 22 into the interior of the outer casing 20" refers to the portion (parts 22c and 22d described later) that protrudes from both ends in the stacking direction and both ends in the short side direction of the inner cover in the long side direction, respectively, and these portions are connected at their ends. In other words, it can be referred to as a single protrusion 22b that protrudes integrally from the outer periphery of the inner cover 22.

[0060] Figures 3-6 A diagram comparing a conventional secondary battery with secondary battery 100 is shown. Figure 3 In the diagram, (A) is a top view of a conventional secondary battery, and (B) is a top view of the secondary battery 100. Figure 4 This is an example of a traditional method for manufacturing secondary batteries. Figure 5 This is an example of a manufacturing method for a secondary battery 100. Figure 6 This is a cross-sectional view of a conventional secondary battery (top) and secondary battery 100 (bottom) focusing on the electrode terminal side.

[0061] like Figure 4As shown, a conventional secondary battery is fabricated as follows. First, a lower laminate with a predetermined space in the center is prepared, and an electrode stack is housed within this space. Next, an upper laminate with the same shape as the lower laminate is placed on top of the lower laminate cover, and the overlapping outer peripheries of these laminates are joined together. The secondary battery fabricated in this way is as follows: Figure 3 , Figure 4 As shown, a sealing portion S exists on the outer periphery (four sides) of the secondary battery. The sealing portion S is required to weld two laminated films together and seal the electrode laminate internally. A certain sealing width is needed to meet predetermined conditions such as strength and moisture permeability. Therefore, such a sealing portion becomes a significant factor reducing the structural efficiency of the secondary battery. Furthermore, to form such a sealing portion, the laminated films require predetermined embossing.

[0062] On the other hand, such as Figure 5 As shown, the secondary battery 100 is manufactured as follows. First, a cylindrical laminated film outer casing 21 is prepared, and an electrode laminate 10 is housed inside it. Next, an inner cover 22 is placed at the opening 21a of the laminated film outer casing 21, and the outer periphery of the inner cover 22 and the laminated film outer casing 21 overlapping the outer periphery of the inner cover 22 are joined together. The joining method is not particularly limited and can be performed by known methods. For example, joining using heat fusion, joining using adhesives, joining using pressure bonding, joining using lasers, etc.

[0063] Here, the laminated film outer casing 21 is formed by shaping a single laminated film into a cylindrical shape, joining the two ends of the laminated film, and forming a sealing portion S on one side of the cylindrical structure. Specifically, the laminated film outer casing 21 is manufactured as follows: the laminated film is bent into a cylindrical shape, leaving areas at both ends that form the joining portions (sealing portions S), and the overlapping ends are joined. Therefore, the sealing portion S of the laminated film outer casing 21 is only on one side. In this way, by using a cylindrical laminated film outer casing 21, the number of sealing portions can be reduced. Alternatively, it can be as follows... Figure 7 (A) It is bent as shown, with the sealing portion S of the laminated outer casing 21 overlapping the side. This further improves the structural efficiency of the battery. Alternatively, it can be done as follows: Figure 7 (B) The two ends of the laminated outer casing 21 are overlapped and joined on the side. In this case, an adhesive layer needs to be provided on the surface of the inner end. This is because the joining requires adhesive layers to be applied to each other. As a result, the seal S no longer protrudes from the side, thus further improving the construction efficiency of the battery.

[0064] Furthermore, the inner cover 22 has a protrusion 22b extending from its outer periphery into the interior of the outer casing 20, and at least a portion of the electrode stack can be present in the area enclosed by the protrusion 22b. For example, a portion of the stack 11 (electrode element) and the electrode terminal 12 can be present in this area. Moreover, this area partially overlaps with the joint between the inner cover 22 and the laminated film outer casing 21, so by having at least a portion of the electrode stack in this area, the reduction in construction efficiency caused by the sealing portion is suppressed, thereby improving the overall construction efficiency of the secondary battery 100.

[0065] In addition, such as Figure 5 As shown, the inner cover 22 has a through hole 22a through which the power supply terminal 12 passes, and the electrode terminal 12 passes through the through hole 22a and protrudes outward. In this way, the secondary battery 100 can be positioned at a location separate from the sealing portion S in the stacking direction, thus suppressing the softening of the sealing portion S due to heat generated by the electrode terminal 12. In conventional secondary batteries, the electrode terminal is positioned inside the sealing portion S, which carries the risk of softening and peeling of the sealing portion due to heat generated by the electrode terminal. Therefore, conventional secondary batteries include cooling mechanisms to suppress heat generation. On the other hand, in the secondary battery 100, since the softening of the sealing portion S due to heat generated by the electrode terminal 12 can be suppressed, the cooling mechanism can be miniaturized or eliminated, and the battery structure can be scaled down. Therefore, the inner cover 22 not only improves construction efficiency but also contributes to the miniaturization of the battery.

[0066] The length (length in the protruding direction) of the protrusion 22b of the inner cover 22 is not particularly limited, as long as it is the same length as the width of the sealing portion S. Furthermore, in order to properly bond with the laminated outer casing 21, a predetermined adhesive layer (such as a tab film) can be provided on the outer periphery of the inner cover 22 and the surface of the protrusion 22b, and a predetermined surface treatment can also be performed. Therefore, embossing is not required at the bonding portion between the inner cover 22 and the laminated outer casing 21. Since embossing is not required, the size constraints of the outer casing 20 are reduced.

[0067] use Figure 6 The improvement effect of the construction efficiency of the inner cover 22 will be further explained. Figure 6 These are cross-sectional views of a conventional secondary battery (top) and secondary battery 100 (bottom) focusing on the electrode terminal side. Figure 6As shown, in conventional secondary batteries, the portion where the current collector and electrode terminals are connected (connection portion C) is bonded to the laminated film where only the electrode terminals are disposed internally. This is because the connection portion C in conventional secondary batteries has unevenness, making it difficult to form a sealing portion, and even if a sealing portion is formed, it is difficult to ensure airtightness. On the other hand, in the secondary battery 100, a sealing portion S is formed on the outer periphery of the inner cover 22 including the protrusion 22b and the protrusion 22b, and the current collector and electrode terminals 12 are connected in the area sandwiched by the protrusion 22b. That is, the connection portion C and the sealing portion S overlap when viewed in the lamination direction. Therefore, the interior of the sealing portion S can be effectively utilized, and the construction efficiency of the secondary battery 100 is improved compared to conventional secondary batteries. Figure 6 The length of X is the corresponding quantity.

[0068] In this way, the secondary battery 100 can improve construction efficiency compared to conventional secondary batteries. On the other hand, the secondary battery 100, due to the use of an external casing 20, will cause the following problems.

[0069] Typically, secondary batteries, such as Figure 2 Multiple electrodes are used in overlapping manner. In this case, a constraint plate R or similar device is used to apply a certain constraint pressure towards the interior in the stacking direction. This improves the adhesion of the electrode stack (electrode elements) and enhances battery performance. On the other hand, in the secondary battery 100, the outer periphery of the laminated film outer casing 21 and the inner cover 22 are joined, but it is anticipated that the thickness of the inner cover 22 may prevent the application of constraint pressure using the constraint plate R. Therefore, in the secondary battery 100, the thickness of the inner cover 22 is designed to be smaller than the thickness of the electrode stack. This allows the application of a certain constraint pressure to the electrode stack 10 using the constraint plate R or similar device. Preferably, the thickness of the inner cover 22 is as thick as possible. For example, it is preferable that the thickness difference between the inner cover 22 and the electrode stack 10 is in the range of 0.2 to 0.8 mm.

[0070] As described above, in the secondary battery 100, the thickness of the inner cover 22 is smaller than the thickness of the electrode laminate 10. However, in this case, the difference in their thicknesses can cause the laminate outer body 21 to twist or bend at the joint (sealing part S), potentially preventing proper heat welding of the inner cover 22 and the laminate. Therefore, to suppress these issues, the protrusion 22b can have a gentle (sloping, gradual) concave shape (recess 22e). Figure 8 The top view (top), front view (bottom left), and side view (bottom right) of the inner cover 22 are shown. Figure 8 (A) is a diagram of the inner cover 22 disposed on the side where the electrode terminal 12 is located. Figure 8 (B) is a diagram of the inner cover 22 disposed on the side where the electrode terminals 12 are not located. Additionally, in Figure 8In the middle, the dashed line represents the inner wall in perspective.

[0071] like Figure 8 As shown, the protrusion 22b has a portion 22c extending from both ends in the stacking direction of the inner cover 22 and a portion 22d extending from both ends in the short side direction. The inner cover 22 having such portions 22c and 22d is a component with a U-shaped cross-section in both the stacking direction and the short side direction. Furthermore, from the viewpoint of absorbing the difference in thickness, portion 22c has a gently sloping concave shape.

[0072] Here, the gently sloping concave shape (recess 22e) is not particularly limited as long as it is a concave shape that can absorb the excess portion of the laminate outer casing 21 based on the thickness difference between the inner cover 22 and the electrode laminate 10. For example, the following conditions can be cited: (1) The recess 22e is composed of a bottom edge 22f and two inclined edges 22g extending from both ends of the bottom edge 22f. (2) The angle Y formed by the bottom edge 22f and the inclined edges 22g is 90° or more and less than 180°. Preferably, it is 120° or more and less than 180°. (3) The length Z in the lamination direction from the bottom edge 22f to the end of the inclined edges 22g is greater than 0 and less than 1 / 5 of the thickness of the inner cover 22. Preferably, it is greater than 0 and less than 1 / 10 of the thickness of the inner cover.

[0073] Thus, the portions 22c of the protrusions 22b each have a gentle concave shape, which can absorb the excess portion of the laminated film outer body 21 based on the thickness difference between the inner cover 22 and the electrode laminate 10, and suppress the generation of distortion and deflection.

[0074] As the material for the outer casing 21 of the laminated film, any known laminated film can be used. For example, an aluminum laminated film. As for the inner cover 22, there are no particular limitations as long as it is made of a material that is airtight and difficult for moisture to pass through. For example, it can be a one-piece molded product of metal or resin and aluminum sheet.

[0075] <Supplementary Matters>

[0076] The following provides supplementary explanation of the secondary battery of this disclosure. In the secondary battery 100 described above, an example using a solid-state battery was given; however, the secondary battery of this disclosure is not limited to this and may also be a liquid battery. In the case of using a liquid battery, known electrode elements can be used.

[0077] In the aforementioned secondary battery 100, the positive terminal 12a and the negative terminal 12b are respectively connected through the through hole 22a of one inner cover 22. However, the secondary battery disclosed herein is not limited to this. It may also be provided with one through hole in the inner cover, with one electrode terminal connected through the through hole of one inner cover and the other electrode terminal connected through the through hole of the other inner cover.

[0078] In the above-described secondary battery 100, an example of a laminated outer casing 21 made from a single laminated film was described. However, the secondary battery of this disclosure is not limited to this. A cylindrical laminated film can also be formed by overlapping two laminated films and thermally fusing the two ends. In this case, a predetermined inner cover is also used, thus improving the construction efficiency of the secondary battery of this disclosure.

[0079] In the aforementioned secondary battery 100, Figure 5 In this embodiment, the electrode stack 10 is housed within a cylindrical laminated film outer casing 21. However, it is not limited to this; alternatively, an electrode stack (electrode stack and inner cover) can be prepared, in which the electrode stack is wound around the laminated film and joined at the ends, thereby housing the electrode stack inside the cylindrical laminated film outer casing. Figure 5 In the method of housing the electrode stack inside a cylindrical laminated film outer casing, a predetermined gap is required between the laminated film outer casing and the electrode stack when housing the electrode stack. On the other hand, the method of housing the electrode stack inside the laminated film outer casing by winding the electrode stack around the laminated film has the advantage of not producing such a gap.

[0080] In the aforementioned secondary battery 100, a cylindrical laminated film outer casing 21 is used, covering the two end faces and a pair of opposing side faces of the electrode laminate 10 in the lamination direction. However, the secondary battery of this disclosure is not limited to this. A cylindrical laminated film covering at least the two end faces and a pair of opposing side faces of the electrode laminate in the lamination direction, i.e., a bottomed cylindrical laminated film covering five sides of the electrode laminate including the two end faces in the lamination direction, can also be used. Since such a laminated film has only one opening, only one inner cover is required.

[0081] In the aforementioned secondary battery 100, an example is shown where a gently sloping concave shape is provided at both ends of the portion 22c in the stacking direction. However, the secondary battery of this disclosure is not limited to this, as long as a gently sloping concave shape is provided at least a portion of the protrusion. That is, it may be a protrusion with one concave shape, or it may be a protrusion with a concave shape at each end of the stacking direction and at each end of the short side direction.

[0082] Industrial availability

[0083] The secondary battery disclosed herein can improve construction efficiency and is an important technology in the battery field from the perspective of battery miniaturization.

Claims

1. A secondary battery, comprising an electrode stack having stacked sheet-like electrode elements and an outer casing housing the electrode stack therein; The outer casing has a cylindrical laminated film outer casing that covers at least two end faces and a pair of opposite side faces in the stacking direction of the electrode laminate, and an inner cover disposed in the opening of the laminated film outer casing; The inner cover has a protrusion extending from its outer periphery into the interior of the outer body, and at least a portion of the electrode stack is present in the region surrounded by the protrusion. In a state where multiple secondary batteries are stacked and a constraint pressure is applied in the stacking direction, the thickness of the inner cover in the stacking direction is smaller than the thickness of the electrode stack. The outer periphery of the inner cover and the laminated outer body overlapping the outer periphery of the inner cover are joined, thereby sealing the electrode laminate inside the outer body.

2. The secondary battery as described in claim 1, The electrode stack comprises a stack of a current collector, a positive electrode layer, an electrolyte layer and a negative electrode layer, and an electrode terminal connected to the current collector; The inner cover has a through hole through which the electrode terminal passes, and the electrode terminal passes through the through hole and protrudes to the outside; In the area sandwiched by the protrusion, the current collector and the electrode terminal are connected.

3. The secondary battery as described in claim 1 or 2, At least a portion of the protrusion has a gently sloping concave shape.

4. The secondary battery as described in claim 1 or 2, The laminated film outer casing is formed by shaping a single laminated film into a cylindrical shape.

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