Patent Publication Number: US-2023155260-A1

Title: Energy storage device and method for manufacturing energy storage device

Description:
TECHNICAL FIELD 
     The present invention relates to an energy storage device and a method for manufacturing an energy storage device. 
     BACKGROUND ART 
     Japanese Patent No. 4509242 (Patent Literature 1) discloses a secondary battery. In this secondary battery, an electrode body is sealed in a bag formed using a laminated film (see Patent Literature 1) . 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Patent No. 4509242 
     SUMMARY OF INVENTION 
     Technical Problem 
     In the secondary battery disclosed in Patent Literature 1 above, a seal portion is provided on a surface of the laminated film that has a large area. Because the seal portion is a region where portions of the film are overlaid on each other, the seal portion is thicker than the other regions. When another secondary battery is stacked on the surface provided with the seal portion, the upper secondary battery may become inclined at the seal portion. As a result, unevenness in the distribution of pressure applied to the lower secondary battery increases. When a plurality of secondary batteries are arranged side-by-side in the lateral direction such that the surfaces provided with the seal portions are in contact with adjacent secondary batteries, unevenness in the distribution of pressures applied by the adjacent secondary batteries also increases. 
     The present invention was made to resolve such issues, and aims to provide an energy storage device that is capable of suppressing unevenness in the distribution of pressure applied to adjacent energy storage devices when a plurality of energy storage devices are stacked, and a method for manufacturing the energy storage device. 
     Solution to Problem 
     An energy storage device according to an aspect of the present invention includes an electrode body and an outer packaging. The outer packaging seals the electrode body. The outer packaging is constituted by a film-like outer packaging member. The outer packaging includes a first sealing portion that is sealed by joining surfaces that face each other in a state in which the outer packaging member is wrapped around the electrode body. A base portion of the first sealing portion is formed at a boundary between a first surface and a second surface of the outer packaging. The first surface has a larger area than the second surface. The first sealing portion does not overlap the first surface in a plan view. 
     In this energy storage device, the first sealing portion does not overlap the first surface having a large area in a plan view. That is, the first sealing portion is not present on the first surface having a large area. Therefore, even when other energy storage devices are disposed on the first surface or disposed side-by-side, the other energy storage devices do not become inclined. As a result, according to this energy storage device, when a plurality of energy storage devices are stacked, it is possible to suppress unevenness in the distribution of pressure applied to adjacent energy storage devices. Also, in this energy storage device, the base portion of the first sealing portion is present on the boundary between the first surface and the second surface of the outer packaging. Therefore, according to this energy storage device, when the first sealing portion is placed on the second surface, it is possible to secure a wider joining width of the first sealing portion, compared to a case where the base portion of the first sealing portion is present on the second surface. 
     In the energy storage device, the first sealing portion may be bent so as to be in contact with the second surface. 
     In the energy storage device, the first sealing portion may cover substantially the entire second surface in a state in which the first sealing portion is bent so as to be in contact with the second surface. 
     According to this energy storage device, it is possible to secure a wider joining width of the first sealing portion due to the first sealing portion covering substantially the entire second surface. 
     The energy storage device may further include an electrode terminal that is electrically connected to the electrode body, in which the outer packaging may further include a second sealing portion sealed in a state of holding the electrode terminal, a portion of the electrode terminal may be located outside the outer packaging, and a base portion of the portion of the electrode terminal may be located at a position at approximately half of the thickness of the energy storage device in a thickness direction of the energy storage device. 
     In this energy storage device, a portion of the electrode terminal located outside the outer packaging is located at a position at approximately half of the thickness of the energy storage device in the thickness direction of the energy storage device. Therefore, according to this energy storage device, it is possible to further reduce the difference between the longest distance and the shortest distance out of the distances between the electrode terminal and each of the plurality of electrodes included in the electrode body, compared to a case where this portion is located at substantially the same position as the first surface in the thickness direction of the energy storage device, for example. 
     In the energy storage device, a region where a joining force between the surfaces is strong and a region where the joining force between the surfaces is weak may be located side-by-side along the boundary in the first sealing portion. 
     In the energy storage device, a thin region and a thick region may be located side-by-side along the boundary in the first sealing portion. 
     The energy storage device may further include an electrode terminal that is electrically connected to the electrode body, in which the first sealing portion may be sealed in a state of holding the electrode terminal. 
     The energy storage device may further include an electrode terminal that is electrically connected to the electrode body and a lid body to which the electrode terminal is attached, in which the outer packaging may further include a second sealing portion sealed in a state of being joined to the lid body. 
     In the energy storage device, the lid body may include a first surface facing the electrode body and a second surface that is opposite to the first surface, and the second sealing portion may include a portion where the outer packaging and the second surface are joined together. 
     The energy storage device may further include a lid body, in which the outer packaging may further include a second sealing portion sealed in a state of being joined to the lid body, the lid body may include a metal portion that is a portion where a metal layer is exposed on a surface of the lid body or that is a portion made of a metal material, and the metal portion and the electrode body may be welded to each other. 
     The energy storage device may further include an electrode terminal that is electrically connected to the electrode body, in which the outer packaging may further include an extending portion that protrudes outward and a second sealing portion sealed in a state in which the electrode terminal is held by the extending portion. 
     In the energy storage device, a direction extending along the boundary may be a direction orthogonal to a machine direction of the outer packaging member. 
     In the energy storage device, when the first sealing portion is bent along the boundary, the direction extending along the boundary is a direction orthogonal to the machine direction of the outer packaging member. Therefore, according to this energy storage device, even when a crease is formed in the direction orthogonal to the machine direction of the outer packaging member, the outer packaging member is unlikely to rupture, and thus, it is possible to reduce the likelihood that the first sealing portion ruptures due to the first sealing portion being bent. 
     An energy storage device according to another aspect of the present invention includes an electrode body, an electrode terminal that is electrically connected to the electrode body, and an outer packaging that seals the electrode body. The outer packaging is constituted by a film-like outer packaging member, and includes a long side and a short side in a plan view. The electrode terminal is disposed along the long side. 
     An energy storage device according to another aspect of the present invention includes an electrode body and an outer packaging. The outer packaging seals the electrode body. In the outer packaging, the outer packaging member is constituted by a film-like outer packaging member. The outer packaging includes a piece in which peripheral edges of surfaces that face each other are joined together in a state in which the outer packaging is wrapped around the electrode body. A base portion of the piece is formed at a boundary between surfaces of the outer packaging. A space in which the surfaces that face each other are not joined is formed in the piece. In the piece, a region in which the surfaces that face each other are joined together and a region in which the surfaces that face each other are not joined are located side-by-side in a vicinity of the boundary. 
     Gas may be generated inside the outer packaging. In this energy storage device, the space is formed in the piece, and the region in which the surfaces that face each other are joined together and the region in which the surfaces that face each other are not joined are located side-by-side in a vicinity of the boundary. Therefore, according to this energy storage device, gas can be discharged from the outer packaging through the piece by unsealing the outer packaging with use of the piece. Then, by unsealing the outer packaging, a degassed energy storage device can be manufactured. 
     A method for manufacturing an energy storage device according to another aspect of the present invention is a manufacturing method for manufacturing an energy storage device from an unfinished product. The unfinished product includes an electrode body and an outer packaging. The outer packaging seals the electrode body. The outer packaging is constituted by a film-like outer packaging member. The outer packaging includes a piece in which peripheral edges of surfaces that face each other are joined together in a state in which the outer packaging member is wrapped around the electrode body. A base portion of the piece is formed at a boundary between surfaces of the outer packaging. A space in which the surfaces that face each other are not joined is formed in the piece. In the piece, a region in which the surfaces that face each other are joined together and a region in which the surfaces that face each other are not joined are located side-by-side in a vicinity of the boundary. The manufacturing method includes a step of unsealing the outer packaging with use of the piece and discharging gas from the outer packaging, and a step of resealing the outer packaging by joining the surfaces that face each other together in at least a portion of the piece. 
     According to the method for manufacturing an energy storage device, a degassed energy storage device can be manufactured by discharging gas via the piece and resealing the outer packaging. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to provide an energy storage device that is capable of suppressing unevenness in the distribution of pressure applied to lower energy storage devices when a plurality of energy storage devices are stacked on each other, and a method for manufacturing the energy storage device. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a perspective view schematically showing an energy storage device according to Embodiment 1. 
         FIG.  2    is a plan view schematically showing the energy storage device. 
         FIG.  3    is a side view schematically showing the energy storage device. 
         FIG.  4    is a diagram showing, from one lateral side, a state in which an outer packaging member is wrapped around an electrode body during the manufacturing of the energy storage device according to Embodiment 1. 
         FIG.  5    is a diagram showing, from below, a state in which an outer packaging member is wrapped around an electrode body during the manufacturing of the energy storage device according to Embodiment 1. 
         FIG.  6    is a diagram schematically showing a portion of a cross-section taken along VI-VI in  FIG.  2   . 
         FIG.  7    is a diagram illustrating a method for forming a second sealing portion. 
         FIG.  8    is a flowchart showing a procedure for manufacturing the energy storage device according to Embodiment 1. 
         FIG.  9    is a plan view schematically showing an energy storage device according to Embodiment 2. 
         FIG.  10    is a side view schematically showing an energy storage device. 
         FIG.  11    is a perspective view schematically showing a lid body. 
         FIG.  12    is a diagram showing a first example in which a lid body and an electrode terminal are formed as a single body. 
         FIG.  13    is a diagram showing a second example in which a lid body and an electrode terminal are formed as a single body. 
         FIG.  14    is a flowchart showing a procedure for manufacturing the energy storage device according to Embodiment 2. 
         FIG.  15    is a flowchart showing another procedure for manufacturing the energy storage device according to Embodiment 2. 
         FIG.  16    is a diagram showing, from one lateral side, a state in which an outer packaging member is wrapped around an electrode body in Embodiment 3. 
         FIG.  17    is a diagram showing, from below, a state in which the outer packaging member is wrapped around the electrode body, and a lid body is attached to the outer packaging member in Embodiment 3. 
         FIG.  18    is a flowchart showing a procedure for manufacturing the energy storage device according to Embodiment 3. 
         FIG.  19    is a plan view schematically showing an energy storage device according to Embodiment 4. 
         FIG.  20    is a side view schematically showing the energy storage device according to Embodiment 4. 
         FIG.  21    is a diagram showing, from one lateral side, a state in which outer packaging members are wrapped around an electrode body in a variation. 
         FIG.  22    is a perspective view schematically showing an energy storage device according to a variation. 
         FIG.  23    is a perspective view schematically showing a lid body according to a variation and an electrode terminal attached to the lid body. 
         FIG.  24    is a perspective view schematically showing an energy storage device to which the lid body shown in  FIG.  23    is attached. 
         FIG.  25    is a front view schematically showing a lid body according to another variation. 
         FIG.  26    is a front view schematically showing a lid body according to yet another variation. 
         FIG.  27    is a plan view schematically showing an energy storage device according to another variation. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that, in the drawings, identical or corresponding portions have been assigned the same reference numerals, and their explanation is not repeated. 
     1. Embodiment 1 
     1-1. Configuration of Energy Storage Device 
       FIG.  1    is a perspective view schematically showing an energy storage device  10  according to Embodiment 1.  FIG.  2    is a plan view schematically showing the energy storage device  10 .  FIG.  3    is a side view schematically showing the energy storage device  10 . Note that an arrow UD direction indicates the thickness direction of the energy storage device  10 , and an arrow LR direction indicates the width direction of the energy storage device  10  in  FIGS.  2  and  3   . Also, an arrow FB direction indicates the depth direction of the energy storage device  10 . The directions that are respectively indicated by the arrows UD, LR, and FB are the same in the following diagrams. 
     Referring to  FIGS.  1 ,  2 , and  3   , the energy storage device  10  includes an electrode body  200 , an outer packaging  100 , and a plurality (two) of electrode terminals  300 . The electrode body  200  includes electrodes (positive and negative electrodes) and a separator that constitute an energy storage member such as a lithium-ion battery, a capacitor, or an all-solid-state battery. The shape of the electrode body  200  is a substantially rectangular parallelepiped. Note that a “substantially rectangular parallelepiped” includes a solid that can be regarded as a rectangular parallelepiped by modifying the shape of a portion of the outer surface thereof, for example, in addition to a perfect rectangular parallelepiped. 
     The electrode terminal  300  is a metal terminal used for inputting and outputting power in the electrode body  200 . One end part of the electrode terminal  300  is electrically connected to an electrode (a positive electrode or negative electrode) included in the electrode body  200 , and the other end part protrudes outward from an end edge of the outer packaging  100 . 
     A metal material constituting the electrode terminal  300  is aluminum, nickel, copper, or the like, for example. If the electrode body  200  is a lithium-ion battery, for example, the electrode terminal  300  to be connected to a positive electrode is usually made of aluminum or the like, and the electrode terminal  300  to be connected to a negative electrode is usually made of copper, nickel, or the like. 
     The outer packaging  100  is constituted by a film-like outer packaging member  101  ( FIG.  4    or the like), and seals the electrode body  200 . In the energy storage device  10 , the outer packaging  100  is formed by wrapping the outer packaging member  101  around the electrode body  200  and sealing the open portion. 
     There is a method for forming an accommodating portion (recess) for accommodating the electrode body  200  in the outer packaging member  101  through cold molding, for example. However, it is not always easy to form a deep accommodating portion using such a method. If a deep storage portion (recess) (e.g., a molding depth of 15 mm) is to be formed through cold molding, pinholes or cracks may form in the outer packaging member, and battery performance may deteriorate. On the other hand, the outer packaging  100  seals the electrode body  200  due to the outer packaging member  101  being wrapped around the electrode body  200 , and thus can easily seal the electrode body  200  regardless of the thickness of the electrode body  200 . Note that, in order to reduce the dead space between the electrode body  200  and the outer packaging member  101  in order to increase the volumetric energy density of the energy storage device  10 , it is preferable that the outer packaging member  101  is wrapped around the electrode body  200  so as to be in contact with the outer surface of the electrode body  200 . Further, in an all-solid-state battery, the space between the electrode body  200  and the outer packaging member  101  also needs to be eliminated from the viewpoint that high pressure needs to be evenly applied from the outer surface of the battery in order to exhibit battery performance, and thus it is preferable that the outer packaging member  101  is wrapped around the electrode body  200  so as to be in contact with the outer surface of the electrode body  200 . 
     The outer packaging member  101  is a laminate (laminated film) having a base material layer, a barrier layer, and a heat-sealable resin layer in the stated order, for example. Note that the outer packaging member  101  need not include all of these layers, and a barrier layer need not be included, for example. That is, the outer packaging member  101  need only be made of a flexible material that can be easily bent, and may also be constituted by a resin film, for example. Note that the outer packaging member  101  is preferably heat-sealable. 
     The base material layer included in the outer packaging member  101  is a layer for imparting heat resistance to the outer packaging member  101  and suppressing the formation of pinholes that may form during processing or distribution. The base material layer is constituted including at least either a stretched polyester resin layer or a stretched polyamide resin layer, for example. Because the base material layer includes at least either the stretched polyester resin layer or the stretched polyamide resin layer, it is possible to protect the barrier layer during processing of the outer packaging member  101  and to suppress rupture of the outer packaging member  101 , for example. Also, from the viewpoint of increasing the tensile elongation of the outer packaging member  101 , the stretched polyester resin layer is preferably a biaxially stretched polyester resin layer, and the stretched polyamide resin layer is preferably a biaxially stretched polyamide resin layer. Furthermore, from the viewpoint of improving piercing strength and impact strength, the stretched polyester resin layer is more preferably a biaxially stretched polyethylene terephthalate (PET) film, and the stretched polyamide resin layer is more preferably a biaxially stretched nylon (ONy) film. Note that the base material layer may be constituted including both the stretched polyester resin layer and the stretched polyamide resin layer. From the viewpoint of film strength, the thickness of the base material layer is preferably in a range of 5 to 300 µm, and more preferably in a range of 20 to 150 µm, for example. 
     Also, the barrier layer included in the outer packaging member  101  is constituted by an aluminum foil, for example, from the viewpoint of moisture resistance, workability such as extensibility, and cost. From the viewpoint of packaging suitability and pinhole resistance when packaging the electrode body  200 , the aluminum foil preferably contains iron. The iron content in the aluminum foil is preferably in a range of 0.5 to 5.0 mass%, and more preferably in a range of 0.7 to 2.0 mass%. Because the iron content is 0.5 mass% or more, the outer packaging member  101  has packaging suitability, and high pinhole resistance and extensibility. Further, because the iron content is 5.0 mass% or less, the outer packaging member  101  is highly flexible. 
     From the viewpoint of barrier properties, pinhole resistance, and packaging suitability, the thickness of the barrier layer is preferably in a range of 15 to 100 µm, and more preferably in a range of 30 to 80 µm, for example. When the barrier layer has a thickness of 15 µm or more, the outer packaging member  101  is less likely to rupture even when stress is applied due to a packaging process. When the barrier layer has a thickness of 100 µm or less, it is possible to reduce an increase in the mass of the outer packaging member  101  and to suppress a decrease in the gravimetric energy density of the energy storage device  10 . 
     Also, if the barrier layer is an aluminum foil, in order to prevent dissolution and corrosion, it is preferable that a corrosion resistance film is provided on at least the surface of the barrier layer that is opposite to the base material layer. Corrosion resistance films may be provided on both sides of the barrier layer. Here, a corrosion resistance film refers to a thin film that is formed by subjecting the surface of the barrier layer to hydrothermal transformation treatment such as boehmite treatment, chemical conversion treatment, anodizing treatment, plating such as nickel or chromium plating, or corrosion prevention treatment for applying a coating agent thereto, so as to impart corrosion resistance (e.g., acid resistance and alkali resistance) to the surface of the barrier layer. Specifically, the corrosion resistance film refers to a film for improving the acid resistance of the barrier layer (acid resistance film), a film for improving the alkali resistance of the barrier layer (alkali resistance film), or the like. One type of treatment for forming the corrosion resistance film may be performed, or two or more types of treatments for forming the corrosion resistance film may be performed in combination. Further, the film may have multiple layers instead of a single layer. Also, among these treatments, the hydrothermal transformation treatment and the anodizing treatment are treatments in which the surface of a metal foil is dissolved using a treatment agent so as to form a metal compound having high corrosion resistance. Note that these treatments may be included in the definition of chemical conversion treatment. Also, if the barrier layer has a corrosion resistance film, the barrier layer includes the corrosion resistance film. 
     When the outer packaging member  101  is molded, the corrosion resistance film exhibits the effects of preventing delamination between the barrier layer (e.g., an aluminum alloy foil) and the base material layer, preventing the surface of the barrier layer from being dissolved and corroded due to hydrogen fluoride generated in a reaction between an electrolyte and moisture, in particular, if the barrier layer is an aluminum alloy foil, preventing aluminum oxide present on the surface of the barrier layer from being dissolved and corroded, improving the adhesiveness (wettability) of the surface of the barrier layer, preventing delamination between the base material layer and the barrier layer during heat sealing, and preventing delamination between the base material layer and the barrier layer during molding. 
     Also, the heat-sealable resin layer included in the outer packaging member  101  is a layer that imparts sealing properties to the outer packaging member  101  through heat sealing. Examples of the heat-sealable resin layer include a polyolefin-based resin and a resin film made of an acid-modified polyolefin-based resin obtained by graft-modifying a polyolefin-based resin using an acid such as maleic anhydride or the like. From the viewpoint of sealing properties and strength, the thickness of the heat-sealable resin layer is preferably in a range of 20 to 300 µm, and more preferably in a range of 40 to 150 µm, for example. 
     The outer packaging member  101  preferably has a layer having one or more cushion functions (referred to as “cushion layer” hereinafter) outward of the heat-sealable resin layer, more preferably outward of the barrier layer. The cushion layer may be laminated outward of the base material layer, or the base material layer may have the function of the cushion layer. If the outer packaging member  101  has a plurality of cushion layers, the plurality of cushion layers may be adjacent to each other, or may be laminated with the base material layers, the barrier layers, or the like interposed therebetween. 
     A material constituting the cushion layer can be selected from materials having cushion properties. Examples of the material having cushion properties include rubber, non-woven fabric, and a foam sheet. Examples of rubber include natural rubber, fluororubber, and silicone rubber. The rubber hardness is preferably in a range of about 20 to 90. The material constituting the non-woven fabric preferably has high heat resistance. If the cushion layer is constituted by non-woven fabric, the lower limit of the thickness of the cushion layer is preferably 100 µm, more preferably 200 µm, and even more preferably 1000 µm. If the cushion layer is constituted by non-woven fabric, the upper limit of the thickness of the cushion layer is preferably 5000 µm and more preferably 3000 µm. Preferable ranges for the thickness of the cushion layer are 100 µm to 5000 µm, 100 µm to 3000 µm, 200 µm to 3000 µm, 1000 µm to 5000 µm, or 1000 µm to 3000 µm. Specifically, the thickness of the cushion layer is most preferably in a range of 1000 µm to 3000 µm. 
     If the cushion layer is constituted by rubber, the lower limit of the thickness of the cushion layer is preferably 0.5 mm. If the cushion layer is constituted by rubber, the upper limit of the thickness of the cushion layer is preferably 10 mm, more preferably 5 mm, and even more preferably 2 mm. If the cushion layer is constituted by rubber, preferable ranges for the thickness of the cushion layer are 0.5 mm to 10 mm, 0.5 mm to 5 mm, or 0.5 mm to 2 mm. . 
     If the outer packaging member  101  has a cushion layer, the cushion layer functions as a cushion. Therefore, the outer packaging member  101  is prevented from being damaged by impact when the energy storage device  10  falls, or during handling of the energy storage device  10  while manufacturing the energy storage device  10 . 
       FIG.  4    is a diagram showing, from one lateral side, a state in which the outer packaging member  101  is wrapped around the electrode body  200  during the manufacturing of the energy storage device  10 . As shown in  FIG.  4   , the outer packaging member  101  is wrapped around the electrode body  200 . In this case, the outermost layer of the electrode body  200  need not be an electrode, and may be protective tape or a separator, for example. The first sealing portion  110  is formed by heat-sealing surfaces (heat-sealable resin layers) of the outer packaging member  101  that face each other in a state in which the outer packaging member  101  is wrapped around the electrode body  200 . 
     A base portion of the first sealing portion  110  is located on a side  135  of the outer packaging  100 . The side  135  is formed at the boundary between a first surface  130  and a second surface  140 , which has a smaller area than the first surface  130 . That is, it can be said that the base portion of the first sealing portion  110  is formed at the boundary between the first surface  130  and the second surface  140 , and is not present on either the first surface  130  or the second surface  140 . In the energy storage device  10 , the first sealing portion  110  is bent at the side  135  toward the second surface  140 . In the energy storage device  10 , the first sealing portion  110  is in contact with the second surface  140 , and covers substantially the entire second surface  140 . Note that “substantially the entire second surface 140” refers to a region having 75% or more of the area of the second surface  140 . 
     That is, in the energy storage device  10 , the first sealing portion  110  is not formed on the first surface  130  having a large area. The first surface  130  is flatter than in a case where a sealing portion such as the first sealing portion  110  is in contact with the first surface  130 . Therefore, even when another energy storage device  10  is mounted on the first surface  130 , the other energy storage device  10  does not become inclined. As a result, according to the energy storage device  10 , it is possible to suppress unevenness in the distribution of pressure applied to a lower energy storage device  10  when a plurality of the energy storage devices  10  are stacked on each other. In other words, if a module is formed by stacking a plurality of energy storage devices  10  on each other, it is possible to prevent the first sealing portion  110  from being disposed on a surface (the first surface  130 ) that is adjacent to the adjacent energy storage device  10 . Further, in an all-solid-state battery, such a configuration is also preferable from the viewpoint that high pressure needs to be evenly applied from the outer surface of the battery in order to exhibit battery performance. 
     Also, in the energy storage device  10 , the base portion of the first sealing portion  110  is located on the side  135  of the outer packaging  100 . Therefore, according to the energy storage device  10 , it is possible to secure a wider joined region of the first sealing portion  110 , compared with a case where the base portion of the first sealing portion  110  is located on the second surface  140  (e.g., the center portion of the second surface  140  in the arrow UD direction). Note that the joined region of the first sealing portion  110  need not be the entire region of the first sealing portion  110 , and may be a portion of the first sealing portion  110  such as only the vicinity of the base portion of the first sealing portion  110 , for example. 
     Further, in the energy storage device  10 , substantially the entire second surface  140  is covered by the first sealing portion  110 . That is, in the energy storage device  10 , the length of the first sealing portion  110  in the arrow UD direction is longer than in a case where the first sealing portion  110  covers only half or less of the second surface  140  (see  FIG.  3   ). Therefore, according to the energy storage device  10 , it is possible to secure a wide joined region of the first sealing portion  110 . Further, because substantially the entire second surface  140  is covered by the first sealing portion  110 , the energy storage device  10  is stabilized, even when the energy storage device  10  is placed upright such that the second surface  140  is in contact with the mounting surface. That is, the energy storage device  10  is unlikely to become inclined with respect to the mounting surface. Thus, such a configuration is effective when a plurality of energy storage devices  10  are arranged side-by-side to form a module, for example. 
       FIG.  5    is a diagram showing, from below, a state in which the outer packaging member  101  is wrapped around the electrode body  200  during the manufacturing of the energy storage device  10 . As shown in  FIG.  5   , in the energy storage device  10 , the direction extending along the side  135  is the TD (Transverse Direction) of the outer packaging member  101 , and the direction orthogonal to the side  135  is the MD (Machine Direction) of the outer packaging member  101 . That is, the direction extending along the side  135  is the direction (TD) orthogonal to the machine direction (MD) of the outer packaging member  101 . 
     In the energy storage device  10 , the first sealing portion  110  is bent along the side  135 , and the direction extending along the side  135  is a direction orthogonal to the machine direction of the outer packaging member  101 . Therefore, according to this energy storage device  10 , even when a crease is formed in the direction orthogonal to the machine direction of the outer packaging member  101 , the outer packaging member  101  is unlikely to rupture, and thus, it is possible to reduce the likelihood that the first sealing portion  110  ruptures due to the first sealing portion  110  being bent. 
     The machine direction (MD) of the outer packaging member  101  corresponds to the rolling direction (RD) of the metal foil (aluminum alloy foil or the like) in the barrier layer included in the outer packaging member  101 . The TD of the outer packaging member  101  corresponds to the TD of the metal foil. The rolling direction (RD) of the metal foil can be determined based on rolling marks. 
     Also, a sea-island structure can be confirmed by observing multiple cross-sections of the heat-sealable resin layer of the outer packaging member  101  using an electron microscope, and the direction that is parallel to the cross-section where the average diameter of the islands in the direction that is perpendicular to the thickness direction of the heat-sealable resin layer (also referred to as the “length direction of the heat-sealable resin layer” hereinafter) is the maximum can be determined as the MD. If the MD of the outer packaging member  101  cannot be specified using the rolling marks on the metal foil, the MD can be specified using this method. 
     Specifically, the sea-island structure was checked by observing electron micrographs of a cross-section in the length direction of the heat-sealable resin layer and cross-sections (ten cross-sections in total), which are obtained by changing the angle at increments of 10 degrees from the direction parallel to the cross-section in the length direction to the direction perpendicular to the cross-section in the length direction. Then, with regard to each island on the cross-sections, the island diameter d is measured using the linear distance connecting the two ends in the direction perpendicular to the thickness direction of the heat-sealable resin layer. Then, the average of the dimeters d of the top 20 islands from the largest diameter is calculated for each cross-section. The direction that is parallel to the cross-section having the largest average of the island dimeters d is then determined as the MD. 
       FIG.  6    is a diagram schematically showing a portion of a cross-section taken along VI-VI in  FIG.  2   . As shown in  FIG.  6   , the second sealing portion  120  is sealed in a state in which the outer packaging  100  holds the electrode terminal  300 . 
       FIG.  7    is a diagram illustrating a method for forming the second sealing portion  120 . As shown in  FIG.  7   , the second sealing portion  120  is formed by folding the outer packaging member  101 , and heat-sealing the surfaces (heat-sealable resin layers) of the outer packaging member  101  that face each other. Note that, although not shown in  FIG.  7   , the electrode terminal  300  is located between the surfaces of the outer packaging member  101  that face each other. Note that an adhesive film for adhering to both metal and resin may be disposed between the electrode terminal  300  and the outer packaging member  101 . 
     Referring to  FIG.  6    again, the electrode body  200  includes a plurality of electrodes  210  (a positive electrode and a negative electrode). A current collector  215  extending from each electrode  210  is connected to the electrode terminal  300 . In the energy storage device  10 , a portion of the electrode terminal  300  located outside the outer packaging  100  is located at a position at substantially half of the thickness of the energy storage device  10  in the thickness direction of the energy storage device  10 . That is, a length L2 is approximately half of the length L1. Note that “approximately half of the thickness of the energy storage device 10” refers to being in a range of 35% to 65% of the thickness of the energy storage device  10 . 
     Therefore, according to the energy storage device  10 , it is possible to reduce the difference between the longest distance and the shortest distance out of the distances between the electrode terminal  300  and each of the plurality of electrodes  210 , compared with a case where the electrode terminal  300  is located at substantially the same position as the first surface  130  in the thickness direction of the energy storage device  10 . 
     1-2. Method for Manufacturing Energy Storage Device 
       FIG.  8    is a flowchart showing a procedure for manufacturing the energy storage device  10 . The steps shown in  FIG.  8    are performed by an apparatus for manufacturing the energy storage device  10 , for example. 
     The manufacturing apparatus wraps the outer packaging member  101  around the electrode body  200  (step S 100 ). The manufacturing apparatus forms the first sealing portion  110  by heat-sealing surfaces (the heat-sealable resin layers) of the outer packaging member  101  that face each other (step S 110 ). Accordingly, an unfinished product shown in  FIGS.  4  and  5    is obtained. 
     The manufacturing apparatus bends the first sealing portion  110  such that the first sealing portion  110  comes into contact with the second surface  140  (step S 120 ). The manufacturing apparatus forms the second sealing portion  120  by folding the outer packaging member  101  in a state in which the electrode body  200  is accommodated, and heat-sealing the surfaces (the heat-sealable resin layers) of the outer packaging member  101  that face each other (step S 130 ). Accordingly, the energy storage device  10  is completed. 
     1-3. Characteristics 
     As described above, in the energy storage device  10  according to Embodiment 1, the first sealing portion  110  is bent toward the second surface  140  having a smaller area. That is, the first sealing portion  110  is not present on the first surface  130  having a larger area. Therefore, even when another energy storage device  10  is placed on the first surface  130 , the other energy storage device  10  does not become inclined. As a result, according to the energy storage device  10 , it is possible to suppress unevenness in the distribution of pressure applied to a lower energy storage device  10  when a plurality of the energy storage devices  10  are stacked on each other. Further, if this energy storage device  10  is used in an all-solid-state battery, a packaging form of the present invention is preferable because high pressure needs to be evenly applied from the outer surface of the battery in order to exhibit battery performance. Also, in the energy storage device  10 , the base portion of the first sealing portion  110  is located on the side  135  of the outer packaging  100 . Therefore, according to the energy storage device  10 , when the first sealing portion  110  is placed on the second surface  140 , it is possible to secure a wider joining width of the first sealing portion  110 , compared to a case where the base portion of the first sealing portion  110  is present on the second surface  140 . 
     2. Embodiment 2 
     In the energy storage device  10  according to Embodiment 1 above, the second sealing portion  120  is formed by folding the outer packaging member  101  and heat-sealing the surfaces of the outer packaging member  101  that face each other. However, the shape of the second sealing portion  120  and the method for forming the second sealing portion  120  are not limited to this. Note that the following mainly describes portions that are different from those in Embodiment 1, and portions that are used in common with Embodiment 1 will not be described. 
     2-1. Configuration of Energy Storage Device 
       FIG.  9    is a plan view schematically showing an energy storage device  10 X according to Embodiment 2.  FIG.  10    is a side view schematically showing the energy storage device  10 X.  FIG.  11    is a perspective view schematically showing a lid body  400 . 
     Referring to  FIGS.  9 ,  10 , and  11   , the outer packaging  100 X is configured by fitting the lid body  400  against opening portions at the two ends of the outer packaging member  101  wrapped around the electrode body  200 . The second sealing portion  120 X is formed by heat-sealing the outer packaging member  101  and the lid body  400  in a state in which the lid body  400  is fitted against the opening portions. 
     The lid body  400  is a tray-shaped member having a bottom and a rectangular shape in a plan view, and is formed by cold molding the outer packaging member  101 , for example. Note that the lid body  400  need not be constituted by the outer packaging member  101 , and may be a metal molded article or resin molded article. In the energy storage device  10 X, the lid body  400  is disposed such that the bottom side of the lid body  400  is located inside the outer packaging  100 X. Note that, in the energy storage device  10 X, the bottom side of the lid body  400  need not be located inside the outer packaging  100 X. In the energy storage device  10 X, the bottom side of the lid body  400  may be located outside the outer packaging  100 X. 
     Also, in a state in which the electrode body  200  is accommodated, an electrode terminal  300  passes the lid body  400  and the outer packaging member  101  and protrudes outward of the outer packaging  100 X. That is, the lid body  400  and the outer packaging member  101  are heat-sealed in a state in which the electrode terminal  300  is held therebetween. Note that, in the energy storage device  10 X, the position at which the electrode terminal  300  protrudes outward need not be located between the lid body  400  and the outer packaging member  101 . The electrode terminal  300  may protrude outward from a hole formed in any one of the six surfaces of the outer packaging  100 X, for example. In this case, a slight gap between the outer packaging  100 X and the electrode terminal  300  is filled with resin, for example. 
     Also, in the energy storage device  10 X, the lid body  400  and the electrode terminal  300  are provided as separate bodies. However, the lid body  400  and the electrode terminal  300  need not be provided as separate bodies. The lid body  400  and the electrode terminal  300  may be formed as a single body, for example. 
       FIG.  12    is a diagram showing a first example in which the lid body  400  and the electrode terminal  300  are formed as a single body. As shown in  FIG.  12   , in the first example, the electrode terminal  300  is heat-sealed to the side surface of the lid body  400  in advance. Note that, if the lid body  400  is constituted by the outer packaging member  101 , an adhesive film for adhering to both metal and resin may be disposed between the lid body  400  and the electrode terminal  300 . 
       FIG.  13    is a diagram showing a second example in which the lid body  400  and the electrode terminal  300  are formed as a single body. As shown in  FIG.  13   , in the second example, the electrode terminal  300  passes through the hole formed in the bottom portion of the lid body  400 . A slight gap at the hole in the bottom surface of the lid body  400  is filled with resin, for example. 
     Also, in the energy storage device  10 X, a gas valve may be attached to the second sealing portion  120 X or the hole formed in any one of the six surfaces of the outer packaging  100 X, for example. The gas valve is constituted by a check valve or break valve, for example, and is configured to reduce pressure inside the outer packaging  100 X when the pressure inside the outer packaging  100 X rises due to gas generated inside the energy storage device  10 X. 
     2-2. Method for Manufacturing Energy Storage Device 
       FIG.  14    is a flowchart showing a procedure for manufacturing the energy storage device  10 X. The steps shown in  FIG.  14    are performed by an apparatus for manufacturing the energy storage device  10 X, for example. 
     The manufacturing apparatus wraps the outer packaging member  101  around the electrode body  200  (step S 200 ). The manufacturing apparatus forms the first sealing portion  110  by heat-sealing surfaces (the heat-sealable resin layers) of the outer packaging member  101  that face each other (step S 210 ). Accordingly, an unfinished product shown in  FIGS.  4  and  5    is obtained. 
     The manufacturing apparatus bends the first sealing portion  110  such that the first sealing portion  110  comes into contact with the second surface  140  (step S 220 ). The manufacturing apparatus places the electrode body  200  in the unfinished product obtained in step S 220 , and attaches the lid body  400  to opening portions at the two ends thereof (step S 230 ). The manufacturing apparatus forms the second sealing portion  120 X by heat-sealing the outer packaging member  101  and the lid body  400  (step S 240 ). Accordingly, the energy storage device  10 X is completed. 
     2-3. Characteristics 
     In the energy storage device  10 X according to Embodiment 2, the first sealing portion  110  is also bent toward the second surface  140  having a smaller area. Therefore, according to the energy storage device  10 X, it is possible to suppress unevenness in the distribution of pressure applied to a lower energy storage device  10 X when a plurality of the energy storage devices  10 X are stacked on each other. 
     2-4. Other Characteristics 
     Note that, in the energy storage device  10 X according to Embodiment 2, the first sealing portion  110  need not be bent toward the second surface  140  having a smaller area. The first sealing portion  110  may be bent toward the first surface  130  having a larger area. Also, the base portion of the first sealing portion  110  need not be located on a side  135  of the outer packaging  100 X. The base portion of the first sealing portion  110  may be located on a surface of the outer packaging  100 X other than the lid body  400 . Even in this case, the energy storage device  10 X according to Embodiment 2 has the following characteristics, for example. 
     The energy storage device  10 X includes an electrode body (electrode body  200 ) and an outer packaging (outer packaging  100 X) that seals the electrode body (electrode body  200 ). The outer packaging (outer packaging  100 X) is wrapped around the electrode body (electrode body  200 ), and includes an outer packaging member (outer packaging member  101 ) provided with openings at the two end parts thereof and a lid body (lid body  400 ) that seals the openings. 
     In the energy storage device  10 X, the second sealing portion  120 X is not formed by heat-sealing surfaces of the outer packaging member  101  that face each other as in Example 1 (see  FIG.  7   ). In the energy storage device  10 X, the openings in the outer packaging member  101  wrapped around the electrode body  200  are sealed by the lid body  400 . That is, the second sealing portion  120 X is formed at a portion where the lid body  400  and the outer packaging member  101  overlap each other (see  FIGS.  9  and  10   ). According to such a configuration, the size of the region of the second sealing portion  120 X can be easily reduced by adjusting a depth L3 ( FIG.  11   ) of the lid body  400 . 
     Also, in the energy storage device  10 X, excessive load is not applied due to a corner C1 ( FIGS.  9  and  10   ) of the electrode body  200  in the outer packaging member  101  piercing the outer packaging member  101  at a position of the outer packaging member  101  where the corner C1 is covered. As described above, this is because, in the energy storage device  10 X, the second sealing portion  120 X is not formed by heat-sealing surfaces of the outer packaging member  101  that face each other as in Example 1. 
     Also, the procedure for manufacturing the energy storage device  10 X is not limited to the procedure shown in the flowchart in  FIG.  14   . The energy storage device  10 X may be manufactured using the procedure shown in the flowchart in  FIG.  15   , for example. 
       FIG.  15    is a flowchart showing another procedure for manufacturing the energy storage device  10 X according to Embodiment 2. The steps shown in  FIG.  15    are performed by an apparatus for manufacturing the energy storage device  10 X, for example. The manufacturing apparatus attaches, to the electrode body  200 , a member (e.g., the member shown in  FIGS.  12  and  13   ) in which the electrode terminal  300  and the lid body  400  are formed as a single body (step S 250 ). The electrode terminal  300  is welded to the electrode body  200 , for example. Then, the manufacturing apparatus wraps the outer packaging member  101  around the electrode body  200  (step S 260 ). The manufacturing apparatus forms the first sealing portion  110  by heat-sealing surfaces (the heat-sealable resin layers) of the outer packaging member  101  that face each other, and forms the second sealing portion  120 X by heat-sealing the outer packaging member  101  and the lid body  400  (step S 270 ). Accordingly, the energy storage device  10 X is completed. The energy storage device  10 X may also be manufactured using such a procedure. 
     3. Embodiment 3 
     For the purpose of making the electrolytic solution permeate through the electrode body in the battery manufacturing step, for example, a step of aging the energy storage device that is temporarily sealed in an environment at a predetermined temperature for a predetermined period of time (referred to as an “aging step” hereinafter) is usually performed. Gas is generated by the electrode body  200  in the aging step, and this gas needs to be discharged to the outside of the battery. The energy storage device  10 X according to Embodiment 2 above is not provided with a mechanism for discharging the gas generated in the aging step at the final stage of the manufacturing of the energy storage device  10 X. An energy storage device  10 Y according to Embodiment 3 is provided with a mechanism for discharging the gas generated by the electrode body  200  at the final stage of the manufacturing of the energy storage device  10 Y. Note that the following mainly describes portions that are different from those in Embodiment 2, and portions that are used in common with Embodiment 2 will not be described. 
     3-1. Configuration of Energy Storage Device 
       FIG.  16    is a diagram showing, from one lateral side, a state in which an outer packaging member  101 Y is wrapped around the electrode body  200  during the manufacturing of the energy storage device  10 Y.  FIG.  17    is a diagram showing, from below, a state in which the outer packaging member  101 Y is wrapped around the electrode body  200  and the lid body  400  is attached to the outer packaging member  101 Y during the manufacturing of the energy storage device  10 Y. 
     As shown in  FIGS.  16  and  17   , a piece  150  is formed in a state in which the outer packaging member  101 Y is wrapped around the electrode body  200 . The piece  150  is formed by joining surfaces of the outer packaging member  101 Y that face each other in a state in which the outer packaging member  101 Y is wrapped around the electrode body  200 . More specifically, the piece  150  is formed by joining (heat-sealing) peripheral edges of the surfaces of the outer packaging member  101 Y that face each other in a state in which the outer packaging member  101 Y is wrapped around the electrode body  200 . That is, a first sealing portion  154  is formed at the peripheral edge of the piece  150 . 
     Also, a space  152  in which the surfaces of the outer packaging member  101 Y that face each other are not joined is formed in the piece  150 . Joined regions  151 , in which the surfaces of the outer packaging member  101 Y that face each other are joined, and an un-joined region  153 , in which the surfaces of the outer packaging member  101 Y that face each other are not joined, are alternatingly arranged in the vicinity of the side  135 . That is, a pattern of the joined regions  151  is formed along the side  135  in the piece  150 . 
     As a result of unsealing the outer packaging  100 Y by cutting off a portion of the piece  150 , the gas generated by the electrode body  200  is discharged from the outer packaging  100 Y. Note that the gas discharged to the outside of the outer packaging  100 Y here is not necessarily limited to gas generated by the electrode body  200 , and may be gas other than the gas generated by the electrode body  200 , such as air, water vapor, or hydrogen sulfide. 
     Then, the outer packaging  100 Y is placed in a sealed state again by heat-sealing portions including the vicinity of the side  135  in a belt shape. Accordingly, the energy storage device  10 Y is completed. In the completed energy storage device  10 Y, regions in which the surfaces of the outer packaging member  101 Y that face each other have a strong joining force are arranged along the side  135  alternatingly with regions in which the surfaces thereof that face each other have a weak joining force, in the vicinity of the side  135 . In other words, thin portions and thick portions are alternatingly arranged along the side  135  in the heat-sealing portion in the vicinity of the side  135 . This is because the un-joined region  153  is single-sealed, but the joined regions  151  are double-sealed by heat-sealing the vicinity of the side  135  again. 
     3-2. Method for Manufacturing Energy Storage Device 
       FIG.  18    is a flowchart showing a procedure for manufacturing the energy storage device  10 Y. The steps shown in  FIG.  18    are performed by an apparatus for manufacturing the energy storage device  10 Y, for example. 
     The manufacturing apparatus wraps the outer packaging member  101 Y around the electrode body  200  (step S 300 ). The manufacturing apparatus forms the first sealing portion  154  by heat-sealing peripheral edges of the surfaces (the heat-sealable resin layers) of the outer packaging member  101 Y that face each other (step S 310 ). The manufacturing apparatus forms a pattern of the joined regions  151  by heat-sealing the surfaces of the outer packaging member  101 Y that face each other in the vicinity of the side  135  (step S 320 ). 
     The manufacturing apparatus attaches the lid body  400  to opening portions at the two ends in a state in which the electrode body  200  is accommodated in the unfinished product obtained in step S 320  (step S 330 ). The manufacturing apparatus forms the second sealing portion  120 X by heat-sealing the outer packaging member  101 Y and the lid body  400  (step S 340 ). Then, the aging step is carried out. 
     The manufacturing apparatus degases the gas generated in the aging step by cutting the piece  150 , for example (step S 350 ). The manufacturing apparatus seals the outer packaging  100 Y again by heat-sealing the portion including the joined regions  151  of the piece  150  in a belt shape and removing the end edge portion (step S 360 ). Then, the energy storage device  10 Y is completed by bending the piece  150  toward the second surface  140 . 
     3-3. Characteristics 
     In the energy storage device  10 Y according to Embodiment 3, the piece  150  that includes the first sealing portion  154  is also bent toward the second surface  140  having a smaller area. Therefore, according to the energy storage device  10 Y, it is possible to suppress unevenness in the distribution of pressure applied to a lower energy storage device  10 Y when a plurality of the energy storage devices  10 Y are stacked on each other. If this energy storage device  10 Y is used in an all-solid-state battery, a packaging form of the present invention is preferable because high pressure needs to be evenly applied from the outer surface of the battery in order to exhibit battery performance. 
     4. Embodiment 4 
     In the energy storage device  10 X according to Embodiment 2 above, the position at which the electrode terminal  300  protrudes outward is located between the lid body  400  and the outer packaging member  101 . However, the position at which the electrode terminal  300  protrudes outward is not limited to this. Note that the following mainly describes portions that are different from those in Embodiment 2, and portions that are used in common with Embodiment 2 will not be described. 
     4-1. Configuration of Energy Storage Device 
       FIG.  19    is a plan view schematically showing an energy storage device 10XA according to Embodiment 4.  FIG.  20    is a side view schematically showing the energy storage device 10XA. An outer packaging  100 X of the energy storage device 10XA includes a pair of long sides 100XA and a pair of short sides 100XB in a plan view. The outer packaging  100 X is configured by fitting the lid body  400  against opening portions extending along the long sides 100XA of the outer packaging member  101  wrapped around the electrode body  200 . The second sealing portion  120 X is formed by heat-sealing the outer packaging member  101  and the lid body  400  in a state in which the lid body  400  is fitted against the opening portions. The lid body  400  is provided with a through-hole (not shown). Two electrode terminals  300  protrude from the through-hole in the lid body  400  to the outside the outer packaging  100 X. The two electrode terminals  300  have a shape extending along the long sides 100XA of the outer packaging  100 X. A slight gap between the through-hole and the electrode terminal  300  is filled with resin, for example. In Embodiment 4, the first sealing portion  110  is formed on one side of the two short sides 100XB. 
     The position of the lid body  400  from which the electrode terminal  300  protrudes in the thickness direction (the arrow UD direction) of the energy storage device 10XA can be suitably selected. In Embodiment 4, as shown in  FIG.  20   , the electrode terminals  300  protrude from substantially the center of the lid body  400  in the thickness direction of the energy storage device 10XA to the outside of the outer packaging  100 X. The length of the electrode terminal  300  in the depth direction (the arrow FB direction) of the energy storage device 10XA can be suitably selected. In Embodiment 4, the length of the electrode terminal  300  in the depth direction (the arrow FB direction) of the energy storage device 10XA is substantially the same as the length of the electrode body  200 . 
     4-2. Characteristics 
     In the energy storage device 10XA according to Embodiment 4, the electrode terminals  300  are disposed along the long sides 100XA having a long length in the depth direction, and thus a larger electrode terminal  300  can be used. Therefore, it is possible to provide a high-power energy storage device 10XA. 
     5. Variations 
     Although Embodiments 1 to 4 were described above, the present invention is not limited to Embodiments 1 to 4 above, and various modifications can be made without departing from the gist thereof. Hereinafter, variations will be described. 
     5-1 
     One outer packaging member is wrapped around the electrode body  200  in Embodiments 1 to 4 above. However, the number of outer packaging members wrapped around the electrode body  200  need not be one. Two outer packaging members may be wrapped around the electrode body  200 , for example. 
       FIG.  21    is a diagram showing, from one lateral side, a state in which outer packaging members 101Z1 and 101Z2 are wrapped around the electrode body  200  during the manufacturing of an energy storage device according to a variation. As shown in  FIG.  21   , the electrode body  200  is covered by the outer packaging members 101Z1 and 101Z2. First sealing portions  110 Z are formed by joining opposing surfaces of the outer packaging members 101Z1 and 101Z2. In this example, the first sealing portions  110 Z are bent toward the second surfaces  140 Z, instead of toward the first surface  130 Z. Even with such a configuration, it is possible to achieve the effect of suppressing unevenness in the distribution of pressure applied to a lower energy storage device when a plurality of energy storage devices are stacked on each other. If this energy storage device is used in an all-solid-state battery, a packaging form of the present invention is preferable because high pressure needs to be evenly applied from the outer surface of the battery in order to exhibit battery performance. Note that the first sealing portions  110 Z need not be bent in this example. Also, in this variation, the sealing portions  110 Z may each be sealed in a state in which the sealing portion  110 Z holds a portion of an electrode terminal  300 . Further, in this variation, the first sealing portions  110 Z need not be formed on the side  135 Z, and may protrude outward from substantially the center of the second surfaces  140 Z in the thickness direction of the energy storage device. 
     5-2 
     Although the electrode body  200  is a so-called stack type in which a plurality of electrodes  210  are laminated in Examples 1 to 4 above, the form of the electrode bodies  200  is not limited to this. The electrode body  200  may be a so-called wrapping type in which the electrode body  200  is configured by wrapping a positive electrode and a negative electrode via a separator, for example. Also, the electrode body  200  may be configured by stacking a plurality of wrapping-type electrode bodies. 
     5-3 
     Also, in Embodiments 1 to 4 above, the second surface  140  is a flat surface extending downward from the first surface  130  at a substantially right angle. However, the form of the second surface  140  is not limited to this. Considering a case where the electrode body  200  is a wrapping type, and a flat surface and a curved surface are formed on an outer periphery of the electrode body, for example, it is presumed that the flat surface has a larger area than the curved surface, the first surface  130  covers the flat surface of the electrode body, and the second surface  140  covers the curved surface of the electrode body. In this case, the second surface  140  may also be constituted by the curved surface. In this case, a boundary portion where the second surface  140  extends downward from the first surface  130  serves as the side  135 . 
     5-4 
     Also, four joined regions  151  are formed in Embodiment 3. However, the number of positions at which the joined regions  151  are formed is not limited to this. The joined regions  151  may be formed at two positions in the vicinities of the two ends along the side  135 , at one position in the vicinity of the center of the side  135 , or at five or more positions, for example. 
     5-5 
     Although the electrode terminal  300  is disposed in the second sealing portion  120  in Embodiment 1, the position at which the electrode terminal  300  is disposed on the outer packaging  100  is not limited to this. As shown in  FIG.  22   , the electrode terminals  300  can be disposed in the first sealing portion  110 , for example. In other words, the first sealing portion  110  is sealed in a state in which the first sealing portion  110  holds the electrode terminals  300 . In this variation, at least one of the two electrode terminals  300  may be bent toward the second surface  140  or to the opposite side to the second surface  140 , or need not be bent so as to protrude outward from the side  135 . Because the electrode terminals  300  and the first sealing portion  110  can be easily sealed in this variation, the sealing performance of the outer packaging  100  can be improved. Also, the electrode body  200  can be easily accommodated in the outer packaging  100 . Note that, in this variation, the lid body  400  is fitted against the opening portions at the two ends of the outer packaging member  101  as in Embodiment 2, for example. The second sealing portion  120  is formed by heat-sealing the outer packaging member  101  and the lid body  400  in a state in which the lid body  400  is fitted against the opening portions. 
     5-6 
     Also, the configuration of the lid body  400  can be optionally changed in Embodiment 2.  FIG.  23    is a perspective view showing a lid body  500 , which is a variation of the lid body  400 . The lid body  500  has a plate shape, for example, and includes a first surface  500 A facing the electrode body  200  (see  FIG.  9   ), and a second surface  500 B that is opposite to the first surface  500 A. A hole  500 C that passes through the first surface  500 A and the second surface  500 B is formed at the center of the lid body  500 . A material constituting the lid body  500  is resin, for example. In this variation, it is preferable that an adhesive film  530  for adhering to both the electrode terminal  300  and the lid body  500  is attached to a predetermined range that includes a portion of the electrode terminal  300  that is joined to the lid body  500 . The lid body  500  may be constituted by a member that is divided into a first portion  510  and a second portion  520 , and the lid body  500  may be manufactured through joining them together such that the first portion  510  and the second portion  520  hold the electrode terminal  300  and the adhesive film  530 . Also, the lid body  500  may be manufactured by insert-molding the lid body  500  with respect to the electrode terminal  300  to which the adhesive film  530  is attached. Furthermore, it is preferable that the barrier layer is laminated on at least a portion of the surface of the lid body  500  in this variation. Alternatively, if the lid body  500  has a plurality of layers, a barrier layer may be formed on any layer. The material constituting the barrier layer is aluminum, for example. Note that, in this variation, if a gap is present between the adhesive film  530  and the hole  530 C, this gap is preferably filled with a resin material such as a hot melt, for example. 
     Also, in this variation, as shown in  FIG.  24   , a second sealing portion  120 X is formed by joining the outer packaging member  101  and the second surface  500 B of the lid body  500  together in a state in which the lid body  500  is fitted to the outer packaging  100 X. A means of joining the outer packaging member  101  and the second surface  500 B of the lid body  500  together is heat sealing, for example. In this variation, the outer packaging member  101  is joined to a wider range of the lid body  500 , and thus the sealing performance of the outer packaging  100 X is improved. 
       FIG.  25    is a front view of a lid body  600 , which is another variation of the lid body  400  in Embodiment 2 above. The lid body  600  includes a metal portion  610 , which is a portion where metal is exposed on the surface thereof, and the metal portion  610  and the electrode  210  of the electrode body  200  are welded to each other. The entire lid body  600  may be constituted by only the metal portion  610 , or the metal portion  610  may be formed on a portion of the lid body  600 . If the metal portion  610  is formed on only a portion, the lid body  600  is constituted by a material having a multilayer structure that includes a metal layer. If the lid body  600  is constituted by a material having a multilayer structure in which the metal layer is an intermediate layer, the metal portion  610  is a portion where a layer other than the metal layer is partially removed such that the metal layer is exposed. In the example shown in  FIG.  25   , the metal portion  610  of the lid body  600  functions as an electrode terminal, and thus space is not required between the lid body  600  and the electrode  210 . Therefore, it is possible to reduce the size of the energy storage device  10 X (see  FIG.  9   ) . 
       FIG.  26    is a front view of a lid body  700 , which is another variation of the lid body  400  in Embodiment 2 above. The lid body  700  includes a metal portion  710  made of a metal material and a non-metal portion  720  that is connected to the metal portion  710  and is made of a resin material. The metal portion  710  is welded to an electrode  210  of an electrode body  200 . In the example shown in  FIG.  26   , the metal portion  710  of the lid body  700  functions as the electrode terminal, and thus space is not required between the lid body  700  and the electrode  210 . Therefore, it is possible to reduce the size of the energy storage device  10 X (see  FIG.  9   ). 
     5-7 
     Also, in Embodiment 1 above, the second sealing portion  120  is formed by folding the outer packaging member  101  and heat-sealing the heat-sealable resin layers of the outer packaging member  101 . However, the method for forming the second sealing portion  120  is not limited to this.  FIG.  27    is a plan view schematically showing the energy storage device  10  having a second sealing portion  120 Y according to a variation. The outer packaging member  101  has extending portions  101 X that extend outward of the outer packaging  100 , and the second sealing portion  120 Y is formed by heat-sealing heat-sealable resin layers of the extending portions  101 X. In a portion of the extending portion  101 X where the electrode terminal  300  is disposed, the heat-sealable resin layers of the extending portion  101 X and the electrode terminal  300  are heat-sealed. According to this variation, the second sealing portions  120 Y can be strongly heat-sealed, and thus the sealing performance of the outer packaging  100  can be improved. Note that portions of the extending portions  101 X other than the portions heat-sealed together with the electrode terminals  300  may be cut as needed in this variation. Note that this variation can be applied to the variation shown in  FIG.  22   .  
     
       
         
           
               
               
             
               
                 List of Reference Numerals 
               
             
            
               
                   10 ,  10 X, 10XA,  10 Y,  10 Z 
                 Energy storage device 
               
               
                   100 ,  100 X,  100 Y 
                 Outer packaging 
               
               
                   101 ,  101 Y, 101Z1, 101Z2 
                 Outer packaging member 
               
               
                   101 X 
                 Extending portion 
               
               
                   110 ,  110 Z,  154   
                 First sealing portion 
               
               
                   120 ,  120 X,  120 Y 
                 Second sealing portion 
               
               
                   130 ,  130 Z 
                 First surface 
               
               
                   135 ,  135 Z 
                 Side 
               
               
                   140 ,  140 Z 
                 Second surface 
               
               
                 
                   150 
                 
                 Piece 
               
               
                 
                   151 
                 
                 Joined region 
               
               
                 
                   152 
                 
                 Space 
               
               
                 
                   153 
                 
                 Un-joined region 
               
               
                 
                   200 
                 
                 Electrode body 
               
               
                 
                   210 
                 
                 Electrode 
               
               
                 
                   215 
                 
                 Current collector 
               
               
                 
                   300 
                 
                 Electrode terminal 
               
               
                   500 A 
                 First surface 
               
               
                   500 B 
                 Second surface 
               
               
                   400 ,  500 ,  700   
                 Lid body 
               
               
                   610 ,  710   
                 Metal portion 
               
               
                 C1 
                 Corner