Insulating holder and power storage device

Abstract

To prevent damage to an insulating holder in inserting an electrode body into a case body.SOLUTION: An insulating holder 10 disclosed herein is an insulating box-shaped body that accommodates an electrode body 20 of a power storage device. The insulating holder 10 comprises a planar rectangular bottom face part, a pair of front parts 14 extending upward from the bottom face part, and a pair of side parts 16 extending upward from the bottom face part. The insulating holder 10 is formed with corner parts 10C on the bottom face, and is formed with groove parts 19 near the corner parts 10C. According to such a configuration, when the corner parts 10C of the insulating holder 10 and the case body 34 interfere with each other, the insulating holder 10 is bent along the groove parts 19 and the corner parts 10C are deformed toward the inner side. As a result of this, the interference between the corner parts 10C of the insulating holder 10 and the case body 34 is resolved, which can prevent damage to the insulating holder 10 due to the friction with the case body 34.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The technology disclosed herein relates to an insulating holder and an electricity storage device using the insulating holder. [Background technology]

[0002] Electricity storage devices such as lithium-ion secondary batteries are used in a variety of fields. For example, an electricity storage device includes an electrode assembly, which is a power generation element, a metal case that houses the electrode assembly, and an insulating holder that is interposed between the electrode assembly and the case. The case of this type of electricity storage device also includes a box-shaped case body with an upper opening and a sealing plate that closes the upper opening. In manufacturing an electricity storage device with the above configuration, first, the electrode assembly is housed inside the insulating holder, which is an insulating box-shaped body. Next, the electrode assembly covered with the insulating holder is inserted into the case body through the upper opening. Then, the upper opening of the case body is sealed with the sealing plate. This completes the construction of an electricity storage device in which the electrode assembly and the insulating holder are housed inside the case.

[0003] Furthermore, an insulating holder for an electricity storage device is formed by folding a resin film. Patent Documents 1 to 7 are examples of prior art documents relating to such insulating holders. For example, the manufacturing method described in Patent Document 1 includes the steps of: preparing a film member that has been half-cut along a predetermined fold line; a long-side folding step of making a mountain fold along the fold line corresponding to the long side; a short-side folding step of making a mountain fold along the fold line corresponding to the first short side and a valley fold along the fold line corresponding to the perpendicular line; a diagonal folding step of making a mountain fold along the fold line corresponding to the diagonal line; an assembling step of inserting an electrode assembly into the folded film member; a wrapping step of wrapping the electrode assembly in the film member by making a mountain fold along the fold line corresponding to the second short side; and a step of housing the electrode assembly wrapped in the film member in a battery case. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-121496 [Patent Document 2] Japanese Patent Publication No. 2020-095836 [Patent Document 3] Japanese Patent Application Publication No. 2018-181435 [Patent Document 4] Japanese Patent Application Publication No. 2017-091792 [Patent Document 5] Patent Publication No. 2021-082464 [Patent Document 6] Japanese Patent Publication No. 2020-104186 [Patent Document 7] Japanese Patent Application Publication No. 2019-110036 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the manufacture of the above-described electricity storage device, when the electrode body is inserted into the case body, the insulating holder may be damaged due to friction with the case body. This may expose the electrode body, potentially causing electrical conduction between the electrode body and the case. Therefore, in the manufacture of electricity storage devices, a process is provided for detecting whether or not the insulating holder is damaged. An electricity storage device in which damage to the insulating holder is confirmed is then disposed of or recycled. However, if the above-described damage to the insulating holder occurs frequently, it may cause a significant decrease in production efficiency and yield.

[0006] The technology disclosed herein has been made in consideration of the above circumstances, and aims to provide a technology that suppresses damage to an insulating holder when an electrode body is inserted into a case body. [Means for solving the problem]

[0007] The insulating holder disclosed herein is an insulating box-shaped body that houses an electrode assembly of an electricity storage device. The insulating holder includes a rectangular bottom surface having a pair of first sides extending generally parallel to one another in the width direction and a pair of second sides extending generally parallel to one another in the depth direction, a pair of front surfaces extending upward in the height direction from each of the first sides, a pair of side surfaces extending upward in the height direction from each of the second sides, four third sides extending along the height direction at the boundaries between the front surface and the side surfaces, and four corners where the first, second, and third sides intersect. The insulating holder disclosed herein also includes a groove formed near at least one of the four corners.

[0008] As described above, the box-shaped insulating holder has four corners on the bottom side. As will be described in detail later, the corners of this insulating holder tend to interfere with the case body when inserted into the case body, frequently resulting in damage due to friction. In contrast, the insulating holder disclosed herein has grooves formed near the corners. As a result, when the corners of the insulating holder interfere with the case body, the insulating holder bends along the grooves, causing the corners to deform toward the inside of the insulating holder. As a result, interference between the corners of the insulating holder and the case body is eliminated, thereby preventing damage to the insulating holder due to friction with the case body.

[0009] In one aspect of the insulating holder disclosed herein, grooves are formed on the bottom, front, and side surfaces, so that the grooves surround the corners, making it easier to deform the corners toward the inside of the insulating holder when the corners interfere with the case body.

[0010] In one aspect of the insulating holder disclosed herein, the grooves are formed on the outer surface of the insulating holder, which makes it easier for the insulating holder to bend along the grooves.

[0011] In one aspect of the insulating holder disclosed herein, the grooves are not formed in the corners, which prevents the strength of the corners from decreasing.

[0012] In one embodiment of the insulating holder disclosed herein, the shortest distance from the corner to the groove is 1 mm to 3 mm, which makes it possible to effectively prevent damage to the electrode body and the insulating holder.

[0013] In one aspect of the insulating holder disclosed herein, the remaining thickness in the groove is 10 μm to 100 μm, which makes it possible to more effectively prevent damage to the insulating holder.

[0014] Another aspect of the technology disclosed herein provides an electricity storage device. The electricity storage device disclosed herein includes an electrode assembly, a case that houses the electrode assembly, and an insulating holder that is interposed between the electrode assembly and the case. The case of this electricity storage device includes a box-shaped case body with an upper opening and a sealing plate that closes the upper opening. The upper opening of the electricity storage device disclosed herein is a substantially rectangular opening with rounded corners in a plan view. The insulating holder is an insulating holder having the above-described configuration. An electricity storage device with such a configuration can prevent damage to the insulating holder. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view schematically illustrating the appearance of a secondary battery according to one embodiment. [Figure 2] FIG. 2 is a vertical cross-sectional view schematically showing the internal structure of the secondary battery shown in FIG. [Figure 3] FIG. 3 is a plan view of the case body shown in FIG. [Figure 4] FIG. 4 is a perspective view schematically illustrating an insulating holder according to one embodiment. [Figure 5] FIG. 5 is an enlarged perspective view of the insulating holder shown in FIG. 4 as viewed from the bottom side. [Figure 6] FIG. 6 is a cross-sectional plan view illustrating the positional relationship between the case body and the insulating holder in the manufacture of a secondary battery according to one embodiment. [Figure 7] FIG. 7 is a plan view of a film that constitutes the insulating holder according to this embodiment. [Figure 8]FIG. 8 is a partially enlarged plan view of the film shown in FIG. [Figure 9] FIG. 9 is an enlarged perspective view of an insulating holder according to another embodiment, as viewed from the bottom side. [Figure 10] FIG. 10 is a cross-sectional plan view illustrating the positional relationship between the case body and the insulating holder in the conventional manufacturing method of a secondary battery. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, some preferred embodiments of the technology disclosed herein will be described with reference to the drawings. It should be noted that matters other than those specifically mentioned in this specification that are necessary for implementing the technology disclosed herein can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The technology disclosed herein can be implemented based on the contents disclosed in this specification and common technical knowledge in the relevant field. In this specification, the expression "A to B" indicating a range includes not only the meaning of "A or more and B or less," but also the meanings of "greater than A" and "less than B."

[0017] In this specification, the term "electricity storage device" refers to a concept that encompasses devices in which charge and discharge reactions occur as charge carriers move between a pair of electrodes (positive and negative electrodes) via an electrolyte. That is, the electricity storage device in the technology disclosed herein encompasses secondary batteries such as lithium-ion secondary batteries, nickel-metal hydride batteries, and nickel-cadmium batteries, as well as capacitors such as lithium-ion capacitors and electric double-layer capacitors.

[0018] 1. Structure of secondary batteries Hereinafter, a secondary battery equipped with an insulating holder will be described as one embodiment of the technology disclosed herein. FIG. 1 is a perspective view schematically illustrating the appearance of a secondary battery according to one embodiment. FIG. 2 is a longitudinal sectional view schematically illustrating the internal structure of the secondary battery shown in FIG. 1. FIG. 3 is a plan view of the case body shown in FIG. 1. FIG. 4 is a perspective view schematically illustrating an insulating holder according to one embodiment. FIG. 5 is an enlarged perspective view as seen from the insulating holder shown in FIG. 4. FIG. 6 is a plan view illustrating the positional relationship between the case body and the insulating holder during the manufacture of a secondary battery according to this embodiment. In the drawings, the symbol X indicates the width direction, the symbol Y indicates the depth direction, and the symbol Z indicates the height direction. Furthermore, the symbols L, R, F, Rr, U, and D indicate left, right, front, rear, up, and down, respectively. However, these directions are defined for convenience of explanation and are not intended to limit the installation manner of the insulating holder or the electricity storage device during use or manufacture.

[0019] 1 and 2, the secondary battery 1 according to this embodiment includes an electrode assembly 20, a case 30, and an insulating holder 10. Each of these components will be described below.

[0020] (1) Case The case 30 is a flat, box-shaped container having an internal space 30a. The internal space 30a of the case 30 accommodates the electrode assembly 20. The case 30 is preferably made of a metal member having a certain level of strength or greater. Examples of materials for the case 30 include metal materials such as aluminum and aluminum alloys. The case 30 includes a case main body 34 and a sealing plate 32.

[0021] (a) Case body The case body 34 is a box-shaped body having an upper opening 34a. Specifically, the case body 34 includes a bottom 34b that is a long rectangular plate-like member, a pair of first side walls 34c that extend upward D from long sides (sides along the width direction X) of the bottom 34b, and a pair of second side walls 34d that extend upward D from short sides (sides along the depth direction Y) of the bottom 34b. In other words, the first side walls 34c are side walls with a relatively large area. On the other hand, the second side walls 34d are side walls with a relatively small area.

[0022] As shown in FIG. 3 , the top surface of the case body 34 has a rectangular top opening 34a surrounded by a first side wall 34c and a second side wall 34d. Due to manufacturing constraints, a typical case body 34 has rounded portions 34r formed at the four corners of the top opening 34a. Specifically, the case body 34 is manufactured by rolling an ingot of metal material. The rolled case body 34 has a seamlessly integrated bottom 34b, first side wall 34c, and second side wall 34d, preventing leakage of gas or electrolyte from the boundaries between the wall surfaces. However, considering the rollability of metal materials, it is difficult to form the boundaries between the wall surfaces (e.g., the first side wall 34c and the second side wall 34d) at right angles in a case body 34 manufactured by roll forming. The rounded portions 34r also serve to reinforce the boundary between the first side wall 34c and the second side wall 34d. For these reasons, rounded portions 34r are formed at the four corners of the top opening 34a in a typical case main body 34. Although this does not limit the technology disclosed herein, an example of the radius of curvature R of the rounded portions 34r of the top opening 34a is approximately 2 mm to 3 mm.

[0023] (b) Sealing plate The sealing plate 32 is a plate-like member that closes the top opening 34a of the case body 34. Specifically, as shown in FIG. 2, the sealing plate 32 is fitted into the top opening 34a of the case body 34. In the manufacturing process of this secondary battery 1, a laser is irradiated onto the top surfaces of the sealing plate 32 and the case body 34 so as to straddle the boundary between the sealing plate 32 and the case body 34. This laser welding is performed along the entire outer periphery of the sealing plate 32 (the inner periphery of the case body 34). This seals the internal space 30a of the case 30.

[0024] An electrode terminal 40 is attached to the sealing plate 32. The electrode terminal 40 is a conductive member electrically connected to the electrode assembly 20 inside the case 30. In the secondary battery 1 shown in FIG. 2, an electrode terminal 40 is provided at each end of the sealing plate 32 in the width direction X. Of the pair of electrode terminals 40, one electrode terminal 40 (on the left side L in FIG. 2) is a positive electrode terminal 42 connected to the positive electrode of the electrode assembly 20. The other electrode terminal 40 (on the right side R in FIG. 2) is a negative electrode terminal 44 connected to the negative electrode of the electrode assembly 20. As shown in FIG. 2, the electrode terminal 40 is a structure combining multiple conductive members and extends along the height direction Z. Specifically, a current collecting member 40a constituting the lower end of the electrode terminal 40 is connected to the electrode assembly 20 inside the case 30. On the other hand, an external terminal 40b constituting the upper end of the electrode terminal 40 is exposed to the outside of the case 30. The current collecting member 40a and the external terminal 40b are electrically connected via a shaft portion (not shown) that penetrates the sealing plate 32.

[0025] (2) Electrode body As shown in FIG. 2, the electrode assembly 20 is housed inside a case 30. In this embodiment, one electrode assembly 20 is housed inside the case 30. The number of electrode assemblies 20 is not particularly limited and may be plural. For example, the electrode assembly 20 is formed by laminating a positive electrode and a negative electrode with a separator interposed therebetween. The positive electrode includes a positive electrode core (e.g., aluminum foil) and a positive electrode active material layer applied to the surface of the positive electrode core. On the other hand, the negative electrode includes a negative electrode core (e.g., copper foil) and a negative electrode active material layer applied to the surface of the negative electrode core. The materials of the components (positive electrode, negative electrode, separator, etc.) that make up the electrode assembly 20 can be materials that can be used in general secondary batteries without particular limitation, and detailed description thereof will be omitted as they do not limit the technology disclosed herein.

[0026] A positive electrode connection portion 20A is provided on one side edge in the width direction X of the electrode body 20 shown in FIG. 2. A negative electrode connection portion 20B is provided on the other side edge of the electrode body 20. The positive electrode connection portion 20A is formed by bundling positive electrode cores that are not coated with a positive electrode active material layer. On the other hand, the negative electrode connection portion 20B is formed by bundling negative electrode cores that are not coated with a negative electrode active material layer. A positive electrode terminal 42 is connected to the positive electrode of the electrode body 20 via the positive electrode connection portion 20A. A negative electrode terminal 44 is connected to the negative electrode of the electrode body 20 via the negative electrode connection portion 20B.

[0027] In the secondary battery 1 according to this embodiment, an electrolyte solution permeates the inside of the electrode assembly 20 (between the positive and negative electrodes). The components of this electrolyte solution can be any that can be used in general secondary batteries without any particular restrictions, and detailed description thereof will be omitted as it does not limit the technology disclosed herein. A portion of the electrolyte solution may be present outside the electrode assembly 20 (between the electrode assembly 20 and the case 30) as excess electrolyte solution. This allows the excess electrolyte solution to be supplied to the inside of the electrode assembly 20 when the electrolyte solution decomposes inside the electrode assembly 20.

[0028] (3) Insulation holder The insulating holder 10 is an insulating member that covers the electrode assembly 20. In the manufactured secondary battery 1, the insulating holder 10 is interposed between the electrode assembly 20 and the case 30 (see FIGS. 2 and 6). This prevents electrical conduction between the case 30 and the electrode assembly 20. The insulating holder 10 according to this embodiment is formed by folding a film F (see FIG. 7) made of an insulating material. The material for the insulating holder 10 can be any conventionally known insulating material without any particular restrictions, and does not limit the technology disclosed herein. However, considering material costs and ease of molding, the insulating holder 10 is preferably made of a resin material such as polypropylene (PP) or polyethylene (PE). The thickness of the insulating holder 10 is preferably 75 μm to 200 μm, and more preferably 90 μm to 160 μm. This allows for a high level of both insulation and moldability.

[0029] 4, the insulating holder 10 according to this embodiment is a box-shaped body having an internal space for accommodating the electrode assembly 20. The detailed structure of the insulating holder 10 will be described below.

[0030] First, the bottom surface portion 12 of the insulating holder 10 shown in Fig. 4 is a flat, rectangular plate-like member. This bottom surface portion 12 has a pair of first sides 10X extending substantially parallel to each other in the width direction X and a pair of second sides 10Y extending substantially parallel to each other in the depth direction Y. In this specification, "substantially parallel" means that the angle formed by the pair of straight lines (sides) is 0.15° or less (preferably 0.1° or less, and more preferably 0.05° or less). As the angle formed by this pair of sides (first side 10X or second side 10Y) becomes smaller, the dimensional difference between the components when assembling the insulating holder 10 tends to become smaller.

[0031] Next, the insulating holder 10 has a pair of front portions 14. Each of the pair of front portions 14 is a rectangular plate-like member extending upward in the height direction Z from a respective first side 10X of the bottom surface portion 12. The pair of front portions 14 face each other across an internal space that houses the electrode assembly 20 (see FIG. 6). The insulating holder 10 also has a pair of side portions 16. Each of the pair of side portions 16 is a rectangular plate-like member extending upward in the height direction Z from a respective second side 10Y of the bottom surface portion 12. Like the front portions 14, the side portions 16 also face each other across an internal space. In addition, the insulating holder 10 has a third side 10Z formed at the boundary between the front portions 14 and the side portions 16. The third side 10Z is four ridges extending along the height direction Z. An opening 18 surrounded by the front portion 14 and the side portions 16 is formed in the upper surface of the insulating holder 10. When the electrode body 20 is accommodated in the internal space of the insulating holder 10, the electrode body 20 is inserted into the internal space through this opening 18.

[0032] Furthermore, the insulating holder 10 according to this embodiment includes a first locking portion 15 and a second locking portion 13. This prevents the insulating holder 10 from unfolding during the manufacture of the secondary battery 1. Specifically, the first locking portion 15 is a plate-like member formed continuously from the third edge 10Z on the front F side of the side surface portion 16, and extends along the height direction Z. Each of the first locking portions 15 is bent to cover both side edges in the width direction X of the front surface portion 14 on the front F side. This prevents the front surface portion 14 from rotating (unfolding) outward in the depth direction Y (toward the front F or the rear Rr). It is more preferable that the first locking portion 15 is heat-welded to the front surface portion 14 on the front F side. This more effectively prevents the insulating holder 10 from unfolding.

[0033] On the other hand, the second locking portions 13 are a pair of plate-like members extending upward from each of the second sides 10Y of the bottom surface portion 12. Each of the second locking portions 13 is bent so as to cover the lower portion of the side surface portion 16. This restricts the rotation (unfolding) of the side surface portion 16 toward the rear Rr in the depth direction Y. The second locking portions 13 can also suppress insulation failure caused by gaps occurring at the boundary (second sides 10Y) between the bottom surface portion 12 and the side surface portion 16. The second locking portions 13 may be heat-welded to the side surface portion 16. This more effectively prevents the insulating holder 10 from unfolding. On the other hand, considering manufacturing costs, it is preferable that the second locking portions 13 are not heat-welded to the side surface portion 16.

[0034] Here, four corners 10C are formed on the bottom side of the insulating holder 10, which is a box-shaped body. Each of these corners 10C is formed by the intersection of a first side 10X, a second side 10Y, and a third side 10Z. In the insulating holder 10 according to this embodiment, grooves 19 are formed near these corners 10C. Specifically, in the insulating holder 10 according to this embodiment, annular grooves 19 are formed around each of the four corners 10C, surrounding the corners 10C. This prevents damage to the insulating holder 10 due to friction with the case body 34 during the manufacturing process of the secondary battery 1. Below, we will explain the causes of damage to insulating holders in conventional secondary batteries, and then we will explain the damage prevention effect of the insulating holder 10 according to this embodiment.

[0035] FIG. 10 is a planar cross-sectional view illustrating the positional relationship between the case body and the insulating holder in the manufacture of a conventional secondary battery. As described above, rounded portions 134r are formed at the four corners of the top opening 134a of a typical case body 134. On the other hand, corners 110C are formed at the four corners of the bottom side of the box-shaped insulating holder 110. Here, in a typical secondary battery 100, from the viewpoint of improving battery performance, it is required to design the dimensions of each component so that the electrode assembly 120 and the side walls (first side wall 134c, second side wall 134d) of the case body 134 are close to each other. When the insulating holder 110 is designed to accommodate such an electrode assembly 120, the corners 110C of the insulating holder 110 may be located outside the rounded portions 134r of the case body 134 in a planar view, as shown in FIG. 10. In this case, when the electrode body 120 is inserted into the top opening 134a of the case body 134, the corner 110C of the insulating holder 110 interferes with the R portion 134r of the case body 134. If the electrode body 120 is further inserted in this state, the corner 110C of the insulating holder 110 will be damaged due to friction with the case body 134.

[0036] In contrast, in the insulating holder 10 according to this embodiment, as shown in Figures 5 and 6, a groove 19 is formed near the corner 10C. As a result, when the rounded portion 34r of the case body 34 interferes with the corner 10C of the insulating holder 10, the insulating holder 10 bends along the groove 19. At this time, the corner 10C of the insulating holder 10 deforms inward (in other words, toward the electrode body 20), eliminating interference with the rounded portion 34r of the case body 34. In this way, the insulating holder 10 according to this embodiment can prevent damage to the corner 10C due to friction with the case body 34.

[0037] 5, the insulating holder 10 according to this embodiment has grooves 19 formed in each of the bottom surface 12, front surface 14, and side surface 16. In other words, the grooves 19 in this embodiment are annular grooves 19 that surround the corners 10C. As a result, when the rounded portion 34r of the case body 34 interferes with the corners 10C of the insulating holder 10, each surface of the insulating holder 10 (the bottom surface 12, front surface 14, and side surface 16) bends along the grooves 19, making it easier to deform the corners 10C toward the inside of the insulating holder 10.

[0038] The position of the groove 19 is preferably determined taking into consideration the dimensions of the rounded portion 34r of the case body 34 and the electrode assembly 20. Specifically, the position of the groove 19 is preferably adjusted so that, in a plan view, the straight line L1 (see FIG. 6 ) connecting the groove 19 of the front portion 14 and the groove 19 of the side portion 16 is located outside the electrode assembly 20 and inside the rounded portion 34r of the case body 34. This prevents damage to the corner 10C due to friction with the case body 34 and prevents damage to the electrode assembly 20 due to contact with the deformed insulating holder 10 (corner 10C). For example, the shortest distance d1 from the corner 10C to the groove 19 is preferably 1 mm or more, more preferably 1.5 mm or more. This increases the amount of deformation of the insulating holder 10, thereby appropriately preventing damage to the corner 10C due to interference with the rounded portion 34r. On the other hand, the shortest distance d1 is preferably 3 mm or less, more preferably 2.5 mm or less. This effectively prevents damage to the electrode body 20 and the insulating holder 10.

[0039] Furthermore, the remaining thickness in the groove 19 (thickness of the insulating holder 10 - depth of the groove 19) is preferably 100 μm or less, more preferably 90 μm or less, even more preferably 80 μm or less, and particularly preferably 70 μm or less. As the remaining thickness in the groove 19 becomes smaller, deformation of the insulating holder 10 along the groove 19 becomes more likely to occur, which makes it possible to more effectively prevent damage to the corner 10C due to friction with the case body 34. On the other hand, the remaining thickness in the groove 19 is preferably 10 μm or more, more preferably 20 μm or more, even more preferably 30 μm or more, and particularly preferably 40 μm or more. This ensures sufficient strength in the groove 19, thereby preventing breakage of the insulating holder 10 starting from the groove 19.

[0040] Moreover, the groove 19 is preferably formed on the outer surface 10a of the insulating holder 10. This makes it easier for the insulating holder 10 to bend inward (toward the electrode body 20) along the groove 19 when the case body 34 interferes with the corner 10C, thereby more suitably preventing damage to the corner 10C due to friction with the case body 34.

[0041] It is preferable that the grooves are not formed in the corners 10C themselves. If grooves are formed in the corners 10C, the strength of the corners 10C will be significantly reduced, and there is a risk that the corners 10C will be damaged by friction with the case body 34 before the insulating holder 10 begins to deform along the grooves 19.

[0042] 2. Manufacturing method of insulating holder Next, a method for manufacturing the insulating holder 10 according to this embodiment will be described. Fig. 7 is a plan view of the film that constitutes the insulating holder according to this embodiment. Fig. 8 is a partially enlarged view of the film shown in Fig. 7.

[0043] When manufacturing the insulating holder 10 according to this embodiment, first, a film F as shown in FIG. 7 is prepared. As shown in FIG. 7, this film F has a planar rectangular bottom surface portion 12. A planar rectangular front surface portion 14 extends from both edges of the bottom surface portion 12 in the depth direction Y. A planar rectangular side surface portion 16 extends from both edges of one of the front surfaces 14 (the rear surface Rr in FIG. 7) in the width direction X. Next, a first locking portion 15 extends from the outer side edge of the side surface portion 16 in the width direction X. Furthermore, a second locking portion 13 extends from both edges of the bottom surface portion 12 in the width direction X. First to fourth ruled lines M1 to M4 are formed at the boundaries between the above-mentioned portions. These ruled lines can be formed by half-cutting, which partially thins the film F using a punching blade or the like.

[0044] 8, the film F in this embodiment has three types of grooves, first grooves 19a to third grooves 19c. Of these, the first grooves 19a are formed in the side surface portions 16, the front surface portion 14, the bottom surface portion 12, and the second locking portion 13 so as to surround a first intersection N1 where the side edge 13a of the second locking portion 13, the first crease M1, the second crease M2, and the fourth crease M4 intersect. The second grooves 19b are formed in the second locking portion 13, the bottom surface portion 12, and the front surface portion 14 so as to surround a second intersection N2 where the side edge 13b of the second locking portion 13, the first crease M1, the fourth crease M4, and the side edge 14a of the front surface portion 14 intersect. The third groove 19c is formed in the first engaging portion 15 and the side surface portion 16 so as to surround a third intersection N3 where the side edge 15a of the first engaging portion 15, the third ruled line M3, and the bottom edge 16a of the side surface portion 16 intersect. As shown in FIG. 8, the first to third grooves 19a to 19c are generally annular grooves. Each of the first to third grooves 19a to 19c is formed to have a substantially identical radius. Similar to the ruled lines described above, the first to third grooves 19a to 19c can also be formed by half-cutting using a punching blade or the like.

[0045] The insulating holder 10 according to this embodiment is formed by folding the film F having the above-described configuration. Specifically, the film F is first folded along the first crease M1. This forms a rectangular bottom surface 12 in plan view and a pair of front surfaces 14 facing each other. The first crease M1 after folding becomes the first side 10X. Next, the film F is folded along the second crease M2. This forms a box-shaped insulating holder 10 with a pair of side surfaces 16 facing each other. The second crease M2 after folding becomes the third side 10Z. Next, the film F is folded along the third crease M3. This forms the first locking portion 15. The first locking portion 15 prevents the pair of front surfaces 14 from rotating outward in the depth direction Y (toward the front F or the rear Rr). The third crease M3 after folding becomes the third side 10Z. Next, the film F is folded along the fourth line M4. This forms the second locking portion 13. The second locking portion 13 restricts the pair of side surface portions 16 from rotating toward the rear Rr. The fourth line M4 after folding becomes the second side 10Y. Through the above steps, the insulating holder 10 is formed by folding the film F into a box shape. After molding, the insulating holder 10 has the first to third grooves 19a to 19c overlapping in the thickness direction. This forms an annular groove 19 surrounding the corner 10C of the insulating holder 10 (see FIG. 5).

[0046] 3. Other Embodiments One embodiment of the technology disclosed herein has been described above. Note that the technology disclosed herein is not limited to the above embodiment, and includes other embodiments with various configuration changes. Other examples of the embodiment of the technology disclosed herein will be described below.

[0047] (1) Groove shape As shown in Fig. 5, the insulating holder 10 according to the embodiment described above has an annular groove 19 formed to surround the corner 10C. However, the shape of the groove 19 is not limited to that of the embodiment described above. For example, as shown in Fig. 9, linear grooves 19 may be formed in each of the bottom surface 12, the front surface 14, and the side surface 16 so as to surround the corner 10C. Even when such a configuration is adopted, deformation of the insulating holder 10 occurs starting from each groove 19 when the corner 10C comes into contact with the case body, thereby preventing damage to the corner 10C.

[0048] (2) Surface forming the groove 5 and 9, in the above-described embodiment, grooves 19 are formed in each of the bottom surface 12, front surface 14, and side surface 16 so that the corner 10C is surrounded by the grooves 19. However, the grooves may be formed near the corners, and are not limited to the above-described embodiment. For example, the grooves may be formed in at least one of the bottom surface, front surface, and side surface of the insulating holder. Even with this configuration, damage to the corners can be suppressed because the insulating holder bends from the grooves when the corners come into contact with the case body. However, forming grooves 19 in each of the bottom surface 12, front surface 14, and side surface 16 as in the above-described embodiment makes the insulating holder 10 more susceptible to deformation, thereby more effectively suppressing damage to the corners.

[0049] (3) Number of regions forming grooves In the insulating holder 10 according to the embodiment described above, as shown in FIG. 4, grooves 19 are formed near each of the four corners 10C. However, the number of grooves formed in the insulating holder does not limit the technology disclosed herein and can be changed as needed. For example, by adjusting the insertion position of the electrode body inside the case body, it is possible to make the case body and the insulating holder interfere with each other only at one end in the width direction. In this case, grooves need only be formed near the corners where interference with the case body occurs.

[0050] The technology disclosed herein has been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above. In other words, the technology disclosed herein encompasses the aspects described in items 1 to 7 below.

[0051] <Item 1> An insulating holder that is an insulating box-shaped body that houses an electrode assembly of an electricity storage device, a bottom surface portion having a rectangular shape in plan view, the bottom surface portion having a pair of first sides extending substantially parallel to one another in the width direction and a pair of second sides extending substantially parallel to one another in the depth direction; a pair of front portions extending upward in a height direction from each of the first sides; a pair of side surface portions extending upward in the height direction from each of the second sides; four third sides extending along the height direction at boundaries between the front portion and the side portion; four corners where the first side, the second side, and the third side intersect; It is equipped with An insulating holder having a groove formed near at least one of the four corners.

[0052] <Item 2> Item 2. The insulating holder according to item 1, wherein the grooves are formed in each of the bottom surface, the front surface, and the side surface.

[0053] <Item 3> 3. The insulating holder according to claim 1, wherein the groove is formed on an outer surface of the insulating holder.

[0054] <Item 4> 4. The insulating holder according to any one of items 1 to 3, wherein the groove is not formed in the corner.

[0055] <Item 5> 5. The insulating holder according to any one of items 1 to 4, wherein the shortest distance from the corner to the groove is 1 mm to 3 mm.

[0056] <Item 6> 6. The insulating holder according to any one of items 1 to 5, wherein the remaining thickness in the groove is 10 μm to 100 μm.

[0057] <Item 7> An electricity storage device comprising: an electrode body; a case that houses the electrode body; and an insulating holder that is interposed between the electrode body and the case, The case is a case body that is a box-shaped body having an upper opening; a sealing plate that closes the top opening; It is equipped with the top opening is a rectangular opening with rounded corners at its four corners, 7. An electricity storage device, wherein the insulating holder is the insulating holder according to any one of items 1 to 6. [Explanation of symbols]

[0058] 1 Secondary battery 10 Insulation holder 10C Corner 10X First Side 10Y 2nd side 10Z Third Side 12 Bottom part 13 Second locking portion 14 Front 15 First locking portion 16 Side part 19 Groove 20 Electrode body 30 cases 34 Case body 34a Top opening 34b bottom 34c 1st side wall 34d 2nd side wall 34r R section 40 electrode terminal

Claims

1. An insulating holder that is an insulating box-shaped body that houses an electrode assembly of an electricity storage device, a bottom surface portion having a rectangular shape in plan view, the bottom surface portion having a pair of first sides extending substantially parallel to one another in the width direction and a pair of second sides extending substantially parallel to one another in the depth direction; a pair of front portions extending upward in a height direction from each of the first sides; a pair of side surfaces extending upward in the height direction from each of the second sides; four third sides extending along the height direction at boundaries between the front portion and the side portion; four corners where the first side, the second side, and the third side intersect; It is equipped with a groove surrounding at least one of the four corners is formed in the vicinity of the corner; The insulating holder has a shortest distance from the corner to the groove of 1 mm to 3 mm.

2. 2. The insulating holder according to claim 1, wherein the grooves are formed in the bottom surface, the front surface, and the side surface.

3. 3. The insulating holder according to claim 1, wherein the groove is formed on an outer surface of the insulating holder.

4. 3. The insulating holder according to claim 1, wherein said groove is not formed in said corner portion.

5. 3. The insulating holder according to claim 1, wherein the remaining thickness of the groove is 10 μm to 100 μm.

6. An electricity storage device comprising: an electrode body; a case that houses the electrode body; and an insulating holder that is interposed between the electrode body and the case, The case is a case body that is a box-shaped body having an upper opening; a sealing plate that closes the top opening; It is equipped with the top opening is a rectangular opening with rounded corners in plan view, The electrical storage device, wherein the insulating holder is the insulating holder according to claim 1 or 2.

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