JP7193363B2 - Storage element, method for manufacturing storage element - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electric storage element and a method for manufacturing an electric storage element.

BACKGROUND ART Laminated batteries and wound batteries, in which positive electrodes and negative electrodes are alternately laminated, are widely used as electric storage elements, as proposed in Patent Document 1, for example. An example of such a laminated battery is a lithium ion secondary battery. One of the features of the lithium ion secondary battery is that it has a large capacity compared to other types of stacked batteries. Lithium-ion secondary batteries having such characteristics are expected to spread further in various applications such as on-vehicle applications and stationary housing applications.

In a stacked battery represented by a lithium-ion secondary battery, power is extracted from an electrode body having a positive electrode and a negative electrode, so that the positive electrode and the negative electrode are separated from each other in the region where the electrode active material layer is not provided among the positive electrode and the negative electrode. A tab is attached to the electrode current collector for each electrode that is current collecting. The electrode bodies are accommodated in the exterior body with the tabs attached to the respective electrodes extending to the outside. Such an exterior body is formed by joining two exterior materials.

JP 2011-108624 A

2. Description of the Related Art In order to increase the capacity of an electrode body in a storage device, it is being considered to increase the size of the electrode body. In order to properly accommodate the enlarged electrode assembly, it is desired that the exterior material forming the exterior body has a sufficient thickness.

By the way, in the conventional electric storage element, both of the two exterior materials include a metal layer. When the exterior material forming the exterior body includes a metal layer, it is difficult to make the exterior material thick. Therefore, it is difficult to impart sufficient strength to the exterior body. If the strength of the exterior body is insufficient, the exterior body may bend due to the weight of the electrode body accommodated in the exterior body. The bending of the exterior body causes the electrode body accommodated in the exterior body to be distorted, and the function of the electric storage element may be impaired, for example, a short circuit may occur in the electrode body.

The present invention has been made in consideration of such points, and an object of the present invention is to suppress the bending of the exterior body.

The storage device of the present invention is
an exterior body having a first exterior material and a second exterior material;
an electrode body having a plurality of stacked electrodes accommodated in an accommodation space formed between the first exterior material and the second exterior material,
Of the first exterior material and the second exterior material, only the first exterior material includes a metal layer.

In the electric storage device of the present invention, the thickness of the second exterior material may be thicker than the thickness of the first exterior material.

In the electric storage device of the present invention, the second exterior material may have a thickness of 0.5 mm or more.

In the electric storage device of the present invention, the thickness of the second exterior material may be 3.0 mm or less.

In the electric storage device of the present invention, the second exterior material may include at least one of a polyethylene resin layer, a polypropylene resin layer, and a polyethylene terephthalate resin layer.

In the electric storage device of the present invention, the second exterior member has a peripheral edge portion and a bulging portion that is surrounded by the peripheral edge portion and bulges from the peripheral edge portion in a direction away from the first exterior member. good too.

In the electric storage element of the present invention, a first circumferential bent portion may be formed at a connecting portion between the peripheral portion and the bulging portion.

In the electric storage device of the present invention,
The bulging portion has a circumferential side wall portion connected to the peripheral edge portion and a ceiling wall portion connected to the side wall portion,
A circumferential second bent portion may be formed at a connection portion between the side wall portion and the ceiling wall portion.

In the electric storage device of the present invention,
a tab electrically connected to the electrode of the electrode body and extending out of the exterior body by passing between the first exterior material and the second exterior material;
The second exterior member may have a concave portion that accommodates the tab in a portion that faces the tab.

In the electric storage device of the present invention, the first exterior material may be flat at a portion forming the accommodation space.

In the electric storage device of the present invention, the electrode assembly may include a total of 20 or more electrodes.

The method for manufacturing an electric storage element of the present invention comprises:
a step of fabricating the first exterior material and the second exterior material such that only the first exterior material of the first exterior material and the second exterior material includes a metal layer;
disposing an electrode assembly including a plurality of stacked electrodes between the first packaging material and the second packaging material;
forming an exterior body by joining the first exterior material and the second exterior material.

The method for manufacturing an electric storage element of the present invention may further include an embossing step of embossing the second exterior material.

In the method for manufacturing an electric storage element of the present invention, the embossing step may include forming a bulging portion in the second exterior material.

In the method for manufacturing an electric storage element of the present invention, the embossing step includes electrically connecting the electrode and extending it to the outside of the exterior body by passing between the first exterior material and the second exterior material. Forming a recess in the second sheath for receiving a tab may be included.

In the method for manufacturing a power storage element of the present invention, in the embossing step, the electrode is electrically connected to the bulging portion of the second exterior material and the electrode and passes between the first exterior material and the second exterior material. At the same time, a recess for accommodating a tab extending out of the outer body may be formed at the same time.

ADVANTAGE OF THE INVENTION According to this invention, the bending of an exterior body can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining an embodiment of the present invention and is a perspective view showing a power storage element; FIG. 2 is a plan view showing an electrode assembly housed inside the exterior body of the electric storage device of FIG. 1. FIG. FIG. 3 is a cross-sectional view along line III-III of FIG. 1 of FIG. FIG. 4 is a cross-sectional view of the exterior body of the storage element taken along line IV-IV in FIG. 5 is a side view of the exterior body of the electric storage element of FIG. 1. FIG.

An embodiment of the present invention will be described below with reference to the drawings. In addition, in the drawings attached to this specification, for the convenience of easy understanding, the scale, the ratio of vertical and horizontal dimensions, etc. are changed and exaggerated from those of the real thing.

In this specification, the terms "plate", "sheet" and "film" are not to be distinguished from each other based only on the difference of names.

In addition, terms such as "parallel", "perpendicular", "identical", length and angle values, etc. that specify shapes and geometric conditions and their degrees used in this specification are strictly It shall be interpreted to include the extent to which similar functions can be expected without being bound by the meaning.

1 to 5 are diagrams for explaining an embodiment of a storage device according to the present invention. FIG. 1 is a perspective view showing a specific example of a power storage device. As shown in FIG. 1, the electric storage element 1 includes an exterior body 7, an electrode body 5 housed in a housing space 7a formed by the exterior body 7, and an electrode body 5 connected to the electrode body 5 so as to move from the inside of the exterior body 7 to the outside. and a tab 6 extending to the 2 is a plan view showing the electrode body 5 included in the storage element 1, and FIG. 3 is a cross-sectional view taken along line III-III of FIG. As shown in FIGS. 2 and 3, the electrode body 5 has a plurality of first electrodes 10 and second electrodes 20 stacked in the first direction d1. In the example shown in FIG. 1, the electric storage device 1 has a flat shape that is thin in a first direction d1 that is the thickness direction as a whole, and has a second direction d2 that is the longitudinal direction and a lateral direction. It spreads in the third direction d3. The first direction d1, the second direction d2 and the third direction d3 are non-parallel to each other, and in the illustrated example, the first direction d1, the second direction d2 and the third direction d3 are orthogonal to each other.

An example in which the storage element 1 is a stacked battery, specifically a lithium ion secondary battery will be described below. In this example, the first electrode 10 constitutes the positive electrode 10X and the second electrode 20 constitutes the negative electrode 20Y. However, as can be understood from the description of the effects described below, the embodiment described here is not limited to the lithium ion secondary battery, and the first electrode 10 and the second electrode 20 are It can be widely applied to the storage device 1 that is alternately laminated in the first direction d1. Moreover, the electric storage element 1 is not limited to a laminated battery, and may be, for example, a wound battery. Even when the storage element 1 is a wound battery, the first electrode 10 and the second electrode 20 are stacked in the first direction d1.

Each component of the storage device 1 will be described below.

First, the electrode body 5 will be explained. As shown in FIGS. 2 and 3, the electrode body 5 includes a positive electrode 10X (first electrode 10), a negative electrode 20Y (second electrode 20), and a separator 30 disposed between the positive electrode 10X and the negative electrode 20Y. ,have. As shown in FIG. 3, the positive electrodes 10X and the negative electrodes 20Y are alternately stacked along the first direction d1. The electrode body 5 includes, for example, a total of 20 or more plate-shaped positive electrodes 10X and negative electrodes 20Y. The electrode body 5 has a flat shape as a whole, is thin in the first direction d1, and extends in a second direction d2 and a third direction d3 that are non-parallel to the first direction d1. In the illustrated example, the second direction d2 and the third direction d3 are orthogonal to the first direction d1. The thickness of the electrode body 5, that is, the length along the first direction d1 is, for example, 4 mm or more and 20 mm or less.

In the non-limiting example shown in FIG. 2, the positive electrode 10X and the negative electrode 20Y are plate-like electrodes having a substantially rectangular contour. A second direction d2 non-parallel to the first direction d1 is the longitudinal direction of the positive electrode 10X and the negative electrode 20Y, and a third direction d3 non-parallel to both the first direction d1 and the second direction d2 is the positive electrode 10X and the negative electrode 20Y. 20Y in the lateral direction (width direction). As shown in FIG. 2, the positive electrode 10X and the negative electrode 20Y are staggered in the second direction d2. More specifically, the plurality of positive electrodes 10X are arranged closer to one side in the second direction d2, and the plurality of negative electrodes 20Y are arranged closer to the other side in the second direction d2. As shown in FIG. 2, the positive electrode 10X and the negative electrode 20Y overlap in the first direction d1 at the center in the second direction d2.

As shown in FIG. 2, the length of the negative electrode 20Y (second electrode 20) along the third direction d3 (width direction) is the length of the positive electrode 10X (first electrode 10) along the third direction d3. Longer than length. In the illustrated example, the negative electrode 20Y extends from the positive electrode 10X to one side and the other side in the third direction d3. The thickness of the positive electrode 10X and the negative electrode 20Y, that is, the length in the first direction d1 is, for example, 80 μm or more and 200 μm or less, and the longitudinal direction, that is, the length along the second direction d2 is, for example, 200 mm or more and 950 mm or less, The length (width) along the lateral direction, that is, the third direction d3 is, for example, 70 mm or more and 350 mm or less.

As shown in FIG. 2, the positive electrode 10X (first electrode 10) includes a positive electrode current collector 11X (first electrode current collector 11) and a positive electrode active material layer provided on the positive electrode current collector 11X. 12X (first electrode active material layer 12). In the lithium ion secondary battery, the positive electrode 10X releases lithium ions during discharging and absorbs lithium ions during charging.

As shown in FIG. 2, the positive electrode current collector 11X has, as main surfaces, a first surface 11a and a second surface 11b facing each other. The cathode active material layer 12X is formed on both sides of the first surface 11a and the second surface 11b of the cathode current collector 11X. A plurality of positive electrodes 10X included in the electrode assembly 5 have a pair of positive electrode active material layers 12X provided on both sides of a positive electrode current collector 11X, and can be configured identically to each other.

The positive electrode current collector 11X and the positive electrode active material layer 12X can be produced by various manufacturing methods using various materials that can be applied to the power storage element 1 (lithium ion secondary battery). As an example, the positive electrode current collector 11X may be made of aluminum foil. The positive electrode active material layer 12X contains, for example, a positive electrode active material, a conductive aid, and a binding agent that serves as a binder. The positive electrode active material layer 12X is produced by applying a positive electrode slurry obtained by dispersing a positive electrode active material, a conductive aid, and a binder in a solvent onto the material forming the positive electrode current collector 11X and solidifying the slurry. can be As the positive electrode active material, for example, a lithium metal oxide compound represented by the general formula LiM _x O _y (where M is a metal, and x and y are the composition ratio of metal M and oxygen O) is used. Specific examples of the lithium metal oxide compound include lithium cobaltate, lithium nickelate, and lithium manganate. Alternatively, a lithium metal phosphate compound represented by the general formula LiMPO ₄ (where M is a metal) is used. Specific examples of lithium metal phosphate compounds include lithium iron phosphate, lithium manganese phosphate, and lithium cobalt phosphate. Acetylene black or the like may be used as the conductive aid. Polyvinylidene fluoride or the like may be used as the binder.

As shown in FIG. 2, the positive electrode current collector 11X (first electrode current collector 11) has a first end region a1 and a first electrode region b1. The positive electrode active material layer 12X (first electrode active material layer 12) is arranged only in the first electrode region b1 of the positive electrode current collector 11X. The first end region a1 and the first electrode region b1 are arranged in the second direction d2. The first end region a1 is located outside (to the left in FIG. 2) in the second direction d2 of the first electrode region b1. As shown in FIG. 2, the plurality of positive electrode current collectors 11X are joined and electrically connected in the first end region a1 by resistance welding, ultrasonic welding, sticking with tape, fusion bonding, or the like. . In the illustrated example, one tab 6 is electrically connected to the positive current collector 11X at the first end region a1. The tab 6 extends from the electrode body 5 in the second direction d2. On the other hand, as shown in FIG. 2, the first electrode region b1 is located in a region of the negative electrode 20Y facing a negative electrode active material layer 22Y described later. The width of the positive electrode 10X along the third direction d3 is narrower than the width of the negative electrode 20Y along the third direction d3. Such arrangement of the first electrode regions b1 can prevent deposition of lithium from the negative electrode active material layer 22Y.

Next, the negative electrode 20Y (second electrode 20) will be described. The negative electrode 20Y (second electrode 20) includes a negative electrode current collector 21Y (second electrode current collector 21) and a negative electrode active material layer 22Y (second electrode active material layer 22) provided on the negative electrode current collector 21Y. and have In the lithium ion secondary battery, the negative electrode 20Y absorbs lithium ions during discharging and releases lithium ions during charging.

As shown in FIG. 2, the negative electrode current collector 21Y has, as main surfaces, a first surface 21a and a second surface 21b facing each other. The negative electrode active material layer 22Y is formed on both sides of the first surface 21a and the second surface 21b of the negative electrode current collector 21Y. A plurality of negative electrodes 20Y included in the electrode body 5 have a pair of negative electrode active material layers 22Y provided on both sides of the negative electrode current collector 21Y, and can be configured identically to each other.

The negative electrode current collector 21Y and the negative electrode active material layer 22Y can be produced by various manufacturing methods using various materials that can be applied to the power storage element 1 (lithium ion secondary battery). As an example, the negative electrode current collector 21Y is made of copper foil, for example. The negative electrode active material layer 22Y contains, for example, a negative electrode active material made of a carbon material and a binder that functions as a binder. The negative electrode active material layer 22Y is formed by dispersing a negative electrode slurry in which a negative electrode active material such as carbon powder or graphite powder and a binder such as polyvinylidene fluoride are dispersed in a solvent to form the negative electrode collector 21Y. It can be made by coating on a material and solidifying it.

As shown in FIG. 2, the negative electrode current collector 21Y (second electrode current collector 21) has a second connection region a2 and a second electrode region b2. The negative electrode active material layer 22Y (second electrode active material layer 22) is laminated on the negative electrode current collector 21Y only in the second electrode region b2. The second connection regions a2 and the second electrode regions b2 are arranged in the second direction d2. The second electrode region b2 is located on one side (left side in FIG. 2) in the second direction d2 of the second connection region a2. As shown in FIG. 2, the plurality of negative electrode current collectors 21Y are joined and electrically connected in the second connection region a2 by resistance welding, ultrasonic welding, sticking with tape, fusion bonding, or the like. In the illustrated example, a tab 6 different from the tab connected to the positive current collector 11X is electrically connected to the negative current collector 21Y in the second connection region a2. The tab 6 extends from the electrode body 5 to the other side in the second direction d2.

As already described, the first electrode region b1 of the positive electrode 10X is located inside the region facing the second electrode region b2 of the negative electrode 20Y (see FIG. 2). That is, the second electrode region b2 extends over a region that includes the region facing the positive electrode active material layer 12X of the positive electrode 10X. The width of the negative electrode 20Y along the third direction d3 is wider than the width of the positive electrode 10X along the third direction d3. In particular, the one-side end portion 20a of the negative electrode 20Y in the third direction d3 is located on one side in the third direction d3 of the one-side end portion 10a of the positive electrode 10X in the third direction d3, and The other side end portion 20b in the third direction d3 is located on the other side in the third direction d3 than the other side end portion 10b in the third direction d3 of the positive electrode 10X.

Next, the separator 30 will be explained. As shown in FIG. 3, the separator 30 is positioned between the positive electrode 10X (first electrode 10) and the negative electrode 20Y (second electrode 20), and is spaced apart so that the positive electrode 10X and the negative electrode 20Y do not contact each other. there is The separator 30 has insulating properties, and prevents short circuit due to contact between the positive electrode 10X and the negative electrode 20Y. The separator 30 preferably has a high ion permeability (air permeability), a predetermined mechanical strength, and durability against the electrolytic solution, the positive electrode active material, the negative electrode active material, and the like. As such a separator 30, for example, a porous body or a non-woven fabric made of an insulating material can be used. More specifically, as the separator 30, a porous film made of a thermoplastic resin having a melting point of about 80 to 140.degree. C. can be used. Polyolefin polymers such as polypropylene and polyethylene, or polyethylene terephthalate can be used as the thermoplastic resin. The housing space 7 a of the exterior body 7 is filled with an electrolytic solution together with the electrode body 5 . By impregnating separator 30 made of a porous material or a non-woven fabric with the electrolyte, electrode active material layers 12 and 22 of electrodes 10 and 20 are kept in contact with the electrolyte.

The separator 30 is positioned, for example, between any two electrodes 10 and 20 adjacent in the first direction d1. Further, the separator 30 extends so as to cover the entire area of the positive electrode active material layer 12X of the positive electrode 10X in plan view. Similarly, the separator 30 extends so as to cover the entire region of the negative electrode active material layer 22Y of the negative electrode 20Y in plan view.

Next, tab 6 will be described. Tab 6 functions as a terminal in storage element 1 . A plan view showing the electrode body 5 included in the storage element 1 is shown in FIG. As shown in FIGS. 2 and 3, the tab 6 on one side (one side in the second direction d2) is electrically connected to the positive electrode 10X (first electrode 10) of the electrode body 5. As shown in FIGS. Similarly, the negative electrode 20Y (second electrode 20) of the electrode body 5 is electrically connected to the tab 6 on the other side (the other side in the second direction d2). As shown in FIGS. 1 and 2 , the pair of tabs extends out of the exterior body 7 from a housing space 7 a inside the exterior body 7 . The length of the tab 6 extending outside the exterior body 7 is, for example, 10 mm or more and 25 mm or less. Note that, as shown in FIG. 3, the tab 6 is located between the first exterior material 40 and the second exterior material 50 of the exterior body 7 described later, more specifically, between the insulating layer 42 of the first exterior material 40 and the second exterior material. It passes between the resin layer 52 of the exterior material 50 . Also, the space between the exterior body 7 and the tab 6 is sealed in the region where the tab 6 extends.

The tab 6 has a conductive tab body portion 6a and a seal portion 6b provided on the tab body portion 6a. A portion of one tab 6 located on one side in the second direction d2 of the tab body portion 6a extends outside the exterior body 7 and is located on the other side of the tab body portion 6a in the second direction d2. is connected to the positive electrode 10X (first electrode 10). A portion of the other tab 6 located on the other side in the second direction d2 of the tab body portion 6a extends to the outside of the exterior body 7 and is located on one side of the tab body portion 6a in the second direction d2. is connected to the negative electrode 20Y (second electrode 20). The seal portion 6b surrounds the tab body portion 6a at the central portion of the tab body portion 6a in the second direction d2. The seal portion 6b is welded to the exterior body 7 to seal between the tab main body portion 6a and the exterior body 7. As shown in FIG. The seal portion 6b effectively prevents contact between the tab body portion 6a and the exterior body 7, particularly contact between the tab body portion 6a and the metal layer 41 of the first exterior material 40 in the exterior body 7.

The tab body portion 6a may be formed using aluminum, copper, nickel, nickel-plated copper, or the like. The thickness of the tab body portion 6a is, for example, 0.1 mm or more and 1 mm or less. Examples of the material for the sealing portion 6b include polypropylene, modified polypropylene, low-density polypropylene, ionomer, ethylene-vinyl acetate, and the like. The thickness of the seal portion 6b is, for example, 0.05 mm or more and 0.4 mm or less.

Next, the exterior body 7 will be described with reference to FIGS. 3 to 5. FIG. FIG. 4 is a cross-sectional view of storage element 1 taken along line IV-IV in FIG. 1, with electrode body 5 removed for simplification of the illustration. That is, FIG. 4 shows a cross-sectional view of the exterior body 7. As shown in FIG. FIG. 5 is a diagram of the electric storage element 1 of FIG. 1 observed from the second direction d2, with the tab 6 removed for simplification of the illustration. That is, FIG. 5 shows a side view of the exterior body 7 viewed from the second direction d2.

The exterior body 7 is a packaging body for sealing the electrode body 5 . The exterior body 7 forms an accommodation space 7 a for accommodating the electrode body 5 . The exterior body 7 hermetically seals the electrode body 5 and the electrolytic solution in a housing space 7a therein.

The accommodation space 7a has dimensions equal to or larger than the dimensions of the electrode body 5 so that the electrode body 5 can be accommodated therein. On the other hand, in order to increase the volumetric energy density of the electric storage element 1, it is preferable that the accommodation space 7a is small. Here, the volumetric energy density means the amount of power that can be supplied by the storage element per volume occupied by the storage element. Therefore, it is preferable that the dimensions of the housing space 7a are the same as the dimensions of the electrode assembly 5. As shown in FIG. In other words, the exterior body 7 is preferably in contact with the electrode body 5 that is housed therein. The accommodation space 7a is formed so as to have a shape that matches the shape of the electrode body 5 to be accommodated. In the illustrated example, the accommodation space 7a has a substantially rectangular parallelepiped shape. The accommodation space 7a has, for example, a length of 5 mm or more and 25 mm or less along the first direction d1, a length of 200 mm or more and 1000 mm or less along the second direction d2, and a length of 200 mm or more and 1000 mm or less along the third direction d3. is 70 mm or more and 400 mm or less.

In addition, the exterior body 7 has a first exterior material 40 and a second exterior material 50 . The housing space 7a is formed by joining the first exterior material 40 and the second exterior material 50 at a part of their peripheral edge portions. The first exterior material 40 and the second exterior material 50 may be joined by, for example, an adhesive layer having adhesiveness, or may be joined by welding. In the case of bonding with an adhesive layer, the adhesive layer preferably has insulating properties, chemical resistance, thermoplasticity, etc., in addition to adhesiveness. For example, polypropylene, modified polypropylene, low-density polypropylene, ionomer, ethylene - Vinyl acetate or the like can be used.

As shown in FIGS. 3 and 4 , the first exterior material 40 includes a metal layer 41 and an insulating layer 42 laminated on the metal layer 41 . In the illustrated example, the first exterior material 40 is an insulating coating provided on the surface of the metal layer 41, that is, on the surface of the metal layer 41 opposite to the surface on which the insulating layer 42 is laminated. A layer 43 is further included. On the other hand, the second exterior material 50 includes a resin layer 52 but does not include a metal layer. In other words, only the first exterior material 40 of the first exterior material 40 and the second exterior material 50 includes the metal layer 41 . The first exterior material 40 and the second exterior material 50 are arranged so that the insulating layer 42 side of the first exterior material 40 faces the second exterior material 50 . As shown in FIG. 3, the tab 6 passes between the insulating layer 42 of the first exterior material 40 and the second exterior material 50 in the second direction d2.

The first exterior member 40 is flat in the portion forming the accommodation space 7a. In other words, the first exterior member 40 does not have a bulging portion or a bent portion in the portion forming the accommodation space 7a.

On the other hand, the second exterior member 50 forms a storage space 7a large enough to accommodate the electrode body 5, so as well shown in FIGS. and a bulging portion 60 bulged from the peripheral edge portion 54 in a direction surrounded by 54 and spaced apart from the first exterior member 40 . The bulging portion 60 is located in the central portion of the second exterior material 50 . A first bent portion 56 is formed at the connecting portion between the peripheral portion 54 and the bulging portion 60 . 4, the bulging portion 60 has a circumferential side wall portion 61 connected to the peripheral edge portion 54 and a ceiling wall portion 65 connected to the side wall portion 61. . A second circumferential bent portion 63 is formed at the connecting portion between the side wall portion 61 and the top wall portion 65 .

The metal layer 41 of the first exterior material 40 preferably has high gas barrier properties and moldability, and for example, aluminum foil, stainless steel foil, or the like can be used. The insulating layer 42 prevents electrical connection between the electrode body 5 housed in the housing space 7 a and the metal layer 41 . As the insulating layer 42, for example, polypropylene or the like can be used. The covering layer 43 is, for example, a thin nylon layer.

The second exterior material 50 may be a single layer, or may be a laminate of a plurality of resin layers. The second exterior material 50 preferably includes at least one of a polyethylene resin layer, a polypropylene resin layer, and a polyethylene terephthalate resin layer. That is, the resin layer 52 is preferably made of at least one of a polyethylene resin layer, a polypropylene resin layer, and a polyethylene terephthalate resin layer.

Furthermore, as shown in FIG. 5, the second exterior member 50 has a recess 58 in a portion facing the tab 6. As shown in FIG. The recess 58 has a shape corresponding to the tab 6 so that the tab 6 can be accommodated therein. For example, the recess 58 has a recessed shape that can accommodate a rectangular plate. The depth of the recess 58, that is, the length in the first direction d1 is preferably the same as the thickness of the tab 6. As shown in FIG. Specifically, the depth of the concave portion 58 is preferably 70% or more and 130% or less of the total thickness of the tab body portion 6a and the seal portion 6b of the tab 6, and is 90% or more and 110% or less. is more preferable.

The thickness of the second exterior material 50 is thicker than the thickness of the first exterior material 40 . As a specific example, the thickness of the first exterior material 40 is, for example, 0.1 mm or more and 0.3 mm or less, and the thickness of the second exterior material 50 is 0.5 mm or more and 3.0 mm or less.

Next, an example of a method for manufacturing the storage device 1 of the present embodiment will be described.

First, an electrode body 5 is prepared in which a plurality of first electrodes 10 and second electrodes 20 are alternately laminated and separators 30 are arranged between the first electrodes 10 and the second electrodes 20 . The tab 6 is electrically connected to the first electrode 10 on one side of the electrode body 5 in the second direction d2, and another tab 6 is electrically connected to the second electrode 20 on the other side in the second direction d2. do.

Also, the first exterior material 40 and the second exterior material 50 are produced. Of the first exterior material 40 and the second exterior material 50 to be manufactured, only the first exterior material 40 includes the metal layer 41 . The first exterior material 40 is produced by laminating an insulating layer 42 on a metal layer 41 made of, for example, aluminum foil. The second exterior material 50 is made of a resin layer 52 made of polyethylene, polypropylene, or polyethylene terephthalate, for example. The first exterior material 40 and the second exterior material 50 are formed in a flat plate shape.

Next, the second exterior material 50 is embossed. Since the second exterior material 50 does not include a metal layer and is composed of the resin layer 52, it can be easily embossed. The embossing forms the bulging portion 60 and the recessed portion 58 in the second exterior material 50 . The bulging portion 60 and the recessed portion 58 may be formed separately, but are preferably formed at the same time in order to reduce the manufacturing cost of the second exterior member 50 .

After that, the electrode body 5 is arranged between the first exterior material 40 and the second exterior material 50, and the peripheral edge portions of the first exterior material 40 and the second exterior material 50 are joined. The first exterior material 40 and the second exterior material 50 are arranged so that the insulating layer 42 side faces the second exterior material 50 . The electrode body 5 is housed in the housing space 7 a formed by the bulging portion 60 by joining the first exterior material 40 and the second exterior material 50 . Further, the seal portion 6 b of the tab 6 is joined to the first exterior member 40 while the tab 6 is accommodated in the recess 58 . The first exterior material 40 and the second exterior material 50 are joined by welding, for example, by applying heat and pressure to the peripheral edges of the first exterior material 40 and the second exterior material 50 . This heating and pressurization is carried out by heating the first exterior material 40 and the second exterior material 50 to 120° C. or more and 200° C. or less and pressurizing them to 0.2 MPa or more and 0.8 MPa or less for 1 second or more. It is done by maintaining for seconds or less.

Through the above steps, the storage device 1 as shown in FIG. 1 is manufactured.

By the way, as described above, the size of the electrode body may be increased in order to increase the capacity of the electrode body. When the size of the electrode body increases, the weight of the electrode body increases, so that the exterior body that accommodates the electrode body tends to bend. As a specific example, in a conventional electric storage element, if the weight of the electrode body exceeds 1 kg, the exterior body of the electric storage element is bent during transportation of the electric storage element. If the exterior body is bent, the electrode body accommodated in the exterior body will be distorted, and a short circuit may occur in the electrode body. In order to properly accommodate the electrode body and suppress distortion of the electrode body even if the electrode body becomes large, it is necessary to suppress the bending of the exterior body that houses the electrode body. Needs to be improved.

In order to improve the strength of the exterior material, it was considered to increase the thickness of the exterior material. However, in the conventional electric storage element, if the metal layer is formed thick in order to provide sufficient strength, the exterior material becomes heavy and becomes more difficult to process. As described above, when the metal layer is thickened, the workability and handleability of the electric storage element are greatly impaired. In a conventional electric storage device, two exterior materials forming an exterior body both include metal layers. Therefore, even if the thickness of any of the exterior materials is increased, the workability and handleability of the electric storage element are greatly impaired. As described above, it is difficult to impart sufficient strength to the exterior material in the conventional power storage element, and therefore, it is not possible to suppress the bending of the exterior body.

On the other hand, in power storage device 1 of the present embodiment, only first exterior material 40 of first exterior material 40 and second exterior material 50 includes metal layer 41 . In other words, the second exterior material 50 does not contain a metal layer, but contains only the resin layer 52 . Therefore, even if the thickness of the second exterior material 50 is increased, the handling of the electric storage element is less likely to be impaired. Therefore, the strength of the second exterior material 50 can be improved by increasing the thickness of the second exterior material 50 . That is, the bending of the exterior body 7 can be suppressed.

Moreover, since the first exterior material 40 includes the metal layer 41 , high gas barrier properties and moldability can be imparted to the first exterior material 40 without increasing the thickness of the first exterior material 40 . On the other hand, since the first exterior material 40 and the second exterior material 50 are joined together, the second exterior material 50 has sufficient strength, so that the first exterior material 40 is suppressed from bending. be. Therefore, if the second exterior material 50 has sufficient strength, the first exterior material 40 can be made thin. Since both the first exterior material 40 and the second exterior material 50 are not thickened, the thickness of the exterior body 7 can be reduced. That is, it is possible to suppress a decrease in the volumetric energy density of the storage element 1 .

Also, the thickness of the second exterior material 50 is thicker than the thickness of the first exterior material 40 . Therefore, the second exterior material 50 can have sufficient strength. Therefore, bending of the exterior body 7 can be suppressed.

Furthermore, the thickness of the second exterior material 50 is 0.5 mm or more. Therefore, the second exterior material 50 can have sufficient strength. Therefore, bending of the exterior body 7 can be suppressed.

Moreover, the thickness of the second exterior material 50 is 3.0 mm or less. Therefore, it is possible to prevent the volume energy density from decreasing due to the second exterior material 50 becoming too thick.

Furthermore, the second exterior material 50 includes at least one of a polyethylene resin layer, a polypropylene resin layer, and a polyethylene terephthalate resin layer. Since the polyethylene resin layer, the polypropylene resin layer, and the polyethylene terephthalate resin layer are resistant to the electrolytic solution, the strength of the second packaging material 50 is less likely to decrease even if the electrolytic solution is enclosed in the packaging body 7 . In addition, since the polyethylene resin layer, the polypropylene resin layer, and the polyethylene terephthalate resin layer can be easily made thick, the thickness of the second exterior material 50 can be easily increased to further improve the strength of the second exterior material 50. be able to. Therefore, bending of the exterior body 7 can be further suppressed.

The second exterior member 50 also has a peripheral edge portion 54 and a bulging portion 60 that is surrounded by the peripheral edge portion 54 and protrudes from the peripheral edge portion 54 in a direction away from the first exterior member 40 . By providing such a bulging portion 60 , the housing space 7 a can be formed in the exterior body 7 . In addition, by having the bulging portion 60, the strength of the second exterior member 50 can be further improved by its shape. Therefore, bending of the exterior body 7 can be further suppressed.

Furthermore, a circumferential first bent portion 56 is formed at the connecting portion between the peripheral edge portion 54 and the bulging portion 60 . By having the first bent portion 56, the strength of the second exterior member 50 can be further improved by its shape. Therefore, bending of the exterior body 7 can be further suppressed.

In addition, the bulging portion 60 has a circumferential side wall portion 61 connected to the peripheral edge portion 54 and a ceiling wall portion 65 connected to the side wall portion 61. A connection portion between the side wall portion 61 and the ceiling wall portion 65 A circumferential second bent portion 63 is formed at the end. By having the second bent portion 63, the strength of the second exterior member 50 can be further improved by its shape. Therefore, bending of the exterior body 7 can be further suppressed.

Furthermore, the second exterior member 50 has a concave portion 58 that accommodates the tab 6 in a portion that faces the tab 6 . The recess 58 allows the tab 6 to easily pass between the first sheath 40 and the second sheath 50 . Further, the strength can be further improved by the shape of the second exterior material 50 . Therefore, bending of the exterior body 7 can be further suppressed.

Further, the first exterior member 40 is flat in the portion forming the accommodation space 7a. Therefore, the electrode assembly 5 can be accommodated in the exterior body 7 without enlarging the exterior body 7 . That is, a decrease in volumetric energy density can be suppressed.

Furthermore, the electrode assembly 5 includes 20 or more electrodes 10 and 20 in total. Therefore, the electrode body 5 has a large weight. In such a case, the exterior body 7 becomes easy to bend. Therefore, by improving the strength of the second exterior member 50, the effect of suppressing the bending of the exterior body 7 can be particularly exhibited.

As described above, the power storage element 1 of the present embodiment is formed between the exterior body 7 having the first exterior material 40 and the second exterior material 50 and the first exterior material 40 and the second exterior material 50. and an electrode body 5 having a plurality of stacked electrodes 10 and 20 accommodated in the accommodation space 7a, and only the first exterior material 40 of the first exterior material 40 and the second exterior material 50 is a metal layer. 41 included. According to such a power storage device 1 , the strength of the second exterior material 50 can be improved by increasing the thickness of the second exterior material 50 . Therefore, bending of the exterior body 7 can be suppressed.

Aspects of the present invention are not limited to the above-described embodiments, but include various modifications that can be conceived by those skilled in the art, and effects of the present invention are not limited to the above-described contents. That is, various additions, changes, and partial deletions are possible without departing from the conceptual idea and spirit of the present invention derived from the content defined in the claims and equivalents thereof.

1 Storage Element 5 Electrode Body 6 Tab 7 Exterior Body 7a Housing Space 10 First Electrode 20 Second Electrode 30 Separator 40 First Exterior Material 41 Metal Layer 42 Insulation Layer 50 Second Exterior Material 52 Resin Layer 54 Peripheral Edge 56 First Fold Part 58 Recessed portion 60 Bulging portion 61 Side wall portion 63 Second bent portion 65 Ceiling wall portion

Claims (14)

an exterior body having a first exterior material and a second exterior material;
an electrode body having a plurality of stacked electrodes accommodated in an accommodation space formed between the first exterior material and the second exterior material,
Only the first exterior material of the first exterior material and the second exterior material includes a metal layer ,
The power storage device , wherein the second exterior member has a peripheral edge portion, and a protruding portion surrounded by the peripheral edge portion and protruding from the peripheral edge portion in a direction away from the first exterior member . 2. The power storage device according to claim 1, wherein the thickness of said second exterior material is thicker than the thickness of said first exterior material. 3. The electric storage device according to claim 1, wherein the thickness of said second exterior material is 0.5 mm or more. The power storage device according to any one of claims 1 to 3, wherein the thickness of the second exterior material is 3.0 mm or less. The power storage device according to any one of claims 1 to 4, wherein the second exterior material includes at least one of a polyethylene resin layer, a polypropylene resin layer, and a polyethylene terephthalate resin layer. The electric storage element according to any one of claims 1 to 5, wherein a first circumferential bent portion is formed at a connecting portion between the peripheral portion and the bulging portion. The bulging portion has a circumferential side wall portion connected to the peripheral edge portion and a ceiling wall portion connected to the side wall portion,
The electric storage element according to any one of claims 1 to 5, wherein a second circumferential bent portion is formed at a connecting portion between the side wall portion and the ceiling wall portion. a tab electrically connected to the electrode of the electrode body and extending out of the exterior body by passing between the first exterior material and the second exterior material;
The electric storage device according to any one of claims 1 to 7 , wherein the second exterior member has a concave portion that accommodates the tab in a portion that faces the tab. The electric storage device according to any one of claims 1 to 8 , wherein said first exterior material is flat in a portion forming said housing space. The electric storage element according to any one of claims 1 to 9 , wherein the electrode assembly includes a total of 20 or more electrodes. a step of fabricating the first exterior material and the second exterior material such that only the first exterior material of the first exterior material and the second exterior material includes a metal layer;
disposing an electrode assembly including a plurality of stacked electrodes between the first packaging material and the second packaging material;
A step of joining the first exterior material and the second exterior material to form an exterior body ,
A method for manufacturing an electric storage element , further comprising an embossing step of embossing the second exterior material . 12. The method of manufacturing a power storage element according to claim 11 , wherein said embossing step includes a step of forming a bulging portion in said second exterior material. The embossing step includes forming recesses for accommodating tabs electrically connected to the electrodes, passing between the first and second exterior materials and extending to the outside of the exterior body. 13. The method of manufacturing the electric storage element according to claim 11 , comprising the step of forming the second exterior material. In the embossing step, the electrode is electrically connected to the bulging portion of the second exterior material and the electrode, passes through between the first exterior material and the second exterior material, and extends to the outside of the exterior body. 14. The method of manufacturing an electric storage element according to any one of claims 11 to 13 , wherein the recess for accommodating the tab is formed at the same time.

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