Secondary battery

Abstract

To provide a secondary battery capable of suppressing the generation of a short circuit between a housing and an electrode body caused in an isolation metal piece.SOLUTION: A secondary battery comprises: a housing 11 having an opening; an electrode body 20 housed in the housing 11; a bag body 40 that is arranged inside the housing 11, and insulates between the housing 11 and the electrode body 20; and a lid sealing the opening of the housing 11. The electrode body 20 is formed by laminating, via a separator, a positive electrode material and a negative electrode material. The bag body 40 is formed of insulation films and includes an overlapped part 49b where the insulation films overlap an end side surface part 48b that is opposite to an end surface 20b parallel to a lamination direction in the electrode body 20. The overlapped part 49b is formed of: an electrode body side film 44b in which a penetration hole 45b that is opened to the front and back is formed; and a housing body side film 46b in which the penetration hole is not formed at a position which overlaps the penetration hole 45b formed in the electrode body side film 44b in a direction view orthogonal to the end side surface of the bag body 40.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a secondary battery. [Background technology]

[0002] Conventionally, in electric vehicles, hybrid vehicles, and other electrically powered vehicles using a motor as a drive source, secondary batteries such as nickel-metal hydride batteries and lithium-ion batteries have been used as power sources. As this type of secondary battery, for example, the secondary battery disclosed in Patent Document 1 has been proposed.

[0003] The secondary battery described in Patent Document 1 includes a rectangular parallelepiped battery can with an opening, a lid that seals the opening of the battery can, a power generating element group arranged in a space defined by the battery can and the lid, and an insulating cover that electrically insulates the battery can from the power generating element group. In addition, in this secondary battery, the power generating element group is formed by winding a laminate of a positive electrode plate, a negative electrode plate, and a separator into a flat shape, and a through hole is formed in the insulating cover in a portion facing the side surface (long side surface) of the power generating element group. In this secondary battery, the through hole is formed in the insulating cover, so that the electrolyte can communicate between the inside and outside of the insulating cover via the through hole, and free liquid that does not directly affect the battery function can be reduced. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-198663 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, when a through hole is formed in a portion of an insulating bag (insulating cover) facing a side surface of an electrode body (group of power generating elements) as in the secondary battery described in Patent Document 1, the liberated liquid can be reduced, but the following problems arise.

[0006] That is, as in the secondary battery described in Patent Document 1 above, a through hole is formed in the part facing the side of the electrode body, so that a loose metal piece or the like may connect the casing (battery can) and the electrode body through the through hole, potentially causing a short circuit between the two.

[0007] In addition, when the electrode body is a laminated body as in the secondary battery described in Patent Document 1, the gas generated in the electrode body is more likely to escape to the outside of the electrode body from a pair of end faces parallel to the lamination direction of the electrode body than from the side faces constituting the outermost peripheral surface of the electrode body. Therefore, even if a through hole is formed in a portion facing the side face of the electrode body as in the secondary battery described in Patent Document 1, the gas generated from the end face of the electrode body is less likely to escape to the outside of the bag body, and the bag body is easily damaged by the force of the generated gas, resulting in a portion where no film exists between the housing and the electrode body. Therefore, the secondary battery described in Patent Document 1 has a problem that a short circuit between the housing and the electrode body due to free metal pieces or the like is more likely to occur.

[0008] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a secondary battery that can suppress the occurrence of short circuits between the casing and the electrode body caused by loose metal pieces or the like. [Means for solving the problem]

[0009] The secondary battery according to the present invention, which achieves the above object, has the following characteristic configuration: A housing having an opening; An electrode assembly housed in the housing; A bag body disposed inside the housing and insulating the housing from the electrode body; and a cover that seals the opening of the housing, The electrode body is formed by laminating a positive electrode material and a negative electrode material with a separator interposed therebetween, The bag body is It is made of an insulating film, The electrode body has an overlapping portion formed by the insulating film overlapping an end side surface portion opposite to an end surface parallel to a lamination direction of the electrode body, The overlapping portion is an electrode body side film having through holes opening on the front and back sides; The point is that, when viewed in a direction perpendicular to the end side surface of the bag body, the bag body comprises a housing side film in which no through hole is formed at a position overlapping with the through hole formed in the electrode body side film.

[0010] According to the above characteristic configuration, the housing-side film in which no through hole is formed is overlapped on the outside of the electrode-side film in which a through hole is formed, so that at least one film is present between the housing and the electrode, making it difficult for a free metal piece or the like to connect the housing and the electrode through the through hole. According to the above characteristic configuration, the end side surface facing the end face of the electrode body through which the generated gas is likely to escape has an overlapping portion with a through hole formed therein. This makes it easier for the generated gas to escape from the bag body through the through hole. This prevents the bag body from being damaged by the force of the gas, or the overlap from opening due to the force of the gas, resulting in the creation of a portion where no film is present between the housing and the electrode body. Therefore, a secondary battery having the above-mentioned characteristic configuration can suppress the occurrence of a short circuit between the casing and the electrode assembly caused by loose metal pieces or the like.

[0011] Further characteristic configurations of the secondary battery according to the present invention are as follows: The electrode body has a flat shape, the electrode body side film is formed by folding an end portion of the insulating film constituting one of a pair of side surface portions of the bag body facing a side surface of the electrode body, the housing-side film is formed by folding an end portion of the insulating film that constitutes the other of the pair of side surface portions of the bag body, The electrode body side film and the housing side film are bonded to each other at a position closer to the end of the electrode body side film than the through hole formed in the electrode body side film.

[0012] According to the above-mentioned characteristic configuration, the electrode body side film and the housing side film are bonded to each other, which makes it easier to prevent the overlap from opening up due to the force of gas, resulting in the creation of a portion where no film is present between the housing and the electrode body. According to the above characteristic configuration, the through hole is formed at a position closer to the end of the housing-side film than the adhesive part, which results in a structure in which the flow of gas to the outside that has passed through the through hole is less likely to be impeded by the adhesive part, making it easier to prevent the bag body from being damaged by the force of the gas, or the overlap from being opened by the force of the gas, resulting in the creation of a portion where no film is present between the housing and the electrode body.

[0013] Further characteristic configurations of the secondary battery according to the present invention are as follows: At least one of the mutually opposing surfaces of the electrode body side film and the housing side film has one or a plurality of protrusions formed thereon protruding toward the other surface.

[0014] According to the above-mentioned characteristic configuration, the adhesion between the electrode body side film and the housing side film at the overlapping portion can be suppressed, and a gap can be secured between the insulating films. This makes it easier for the generated gas to escape to the outside of the bag body, making it easier to prevent the bag body from being damaged by the force of the gas, or the overlap from opening up due to the force of the gas, resulting in the creation of a portion where no film is present between the housing and the electrode body.

[0015] Further characteristic configurations of the secondary battery according to the present invention are as follows: The housing side film has a through hole that opens to the front and back at a position that does not overlap with the through hole formed in the electrode body side film when viewed in a direction perpendicular to the end side surface.

[0016] According to the above characteristic configuration, through holes are also formed in the housing-side film located on the outer side of the overlapping portion. This makes it easier for the generated gas to escape to the outside of the bag body compared to a case in which through holes are formed only in the electrode body-side film. Therefore, a secondary battery having the above characteristic configuration makes it easier to prevent the overlapping film from opening up due to the force of the gas, resulting in the creation of a portion where no film is present between the housing and the electrode body. Effect of the Invention

[0017] As described above, according to the secondary battery of the present invention, it is possible to suppress the occurrence of a short circuit between the casing and the electrode assembly caused by free metal pieces or the like. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is an exploded perspective view of a secondary battery according to an embodiment. [Diagram 2] 1 is a cross-sectional view showing a schematic configuration of a secondary battery according to an embodiment. [Diagram 3] FIG. 4 is a development view of an insulating film that constitutes the bag body. [Figure 4] 13 is a side view of the bag body as viewed from the other side in the X-axis direction. FIG. [Diagram 5] FIG. 5 is an enlarged cross-sectional view of a portion VV of FIG. [Figure 6] FIG. 3 is a cross-sectional view taken along the line VI-VI in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, a secondary battery according to an embodiment of the present invention will be described with reference to the drawings. In the following, an embodiment in which the secondary battery is a lithium ion secondary battery will be described as an example. In addition, in the following, each description and each drawing will be appropriately simplified in order to clarify the description.

[0020] [Overview of secondary battery 1] Fig. 1 is an exploded perspective view of a secondary battery according to this embodiment. Fig. 2 is a cross-sectional view showing a schematic configuration of the secondary battery according to this embodiment. In the following description, the direction parallel to the height direction of the secondary battery 1 is defined as the Z-axis direction, the direction parallel to the longitudinal direction of the electrode body 20 is defined as the X-axis direction, and the direction parallel to the thickness direction of the electrode body 20 is defined as the Y-axis direction. The Z-axis direction is parallel to the up-down direction, and the X-axis and Y-axis directions are perpendicular to each other and parallel to the horizontal direction.

[0021] 1 and 2, the secondary battery 1 includes a battery case 10 consisting of a case body 11 and a sealing plate 12, metal battery terminals PS and NS, an electrode body 20, a pouch 40, etc. The secondary battery 1 is a sealed secondary battery in which the electrode body 20, a portion of the battery terminals PS and NS, the pouch 40, etc. are accommodated inside the case body 11, the opening of the case body 11 is sealed with the sealing plate 12, and an electrolyte is injected into the inside of the case body 11.

[0022] [Configuration of battery case 10] As shown in Fig. 1 and Fig. 2, a battery case 10 of this embodiment is composed of a case body 11 with an open top, and a sealing plate 12 that seals the opening of the case body 11. In the battery case 10 of this embodiment, the case body 11 and the sealing plate 12 are both made of aluminum, but are not limited to this. Various metals and alloys can be used as materials for the case body 11 and the sealing plate 12. In this embodiment, the case body 11 corresponds to the "casing" and the sealing plate 12 corresponds to the "lid".

[0023] In this embodiment, the case body 11 has a substantially rectangular parallelepiped shape. The case body 11 has a pair of side walls 11a provided opposite to each other along the longitudinal direction (X-axis direction), a pair of end side walls 11b connecting the ends of the side walls 11a in the longitudinal direction (X-axis direction), and a bottom portion 11c closing the bottom.

[0024] The sealing plate 12 has a shape corresponding to the shape of the opening of the case body 11, and is configured to be able to seal the opening of the case body 11. The sealing plate 12 is made of a flat plate member having a generally rectangular shape when viewed in the Z-axis direction. A positive electrode terminal PS is disposed on one end side in the longitudinal direction of the sealing plate 12 (one end side in the X-axis direction), and a negative electrode terminal NS is disposed on the other end side in the longitudinal direction (the other end side in the X-axis direction). The sealing plate 12 is joined to the case body 11 by welding or the like so as to close the opening of the case body 11.

[0025] [Configuration of electrode body 20] The electrode body 20 is formed by stacking positive and negative electrode materials with a separator interposed therebetween, and is housed in the case body 11. In this embodiment, the electrode body 20 is formed of a wound body in which long strip-shaped positive and negative electrode materials are stacked with a similar strip-shaped separator interposed therebetween, wound, and compressed into a flat shape. As shown in Figs. 1 and 2, the electrode body 20 of this embodiment is substantially rectangular when viewed in the thickness direction (Y-axis direction), and a positive electrode terminal joint 21 in which the positive electrode material is collected is formed at one end side in the longitudinal direction (X-axis direction) when viewed in the thickness direction, and a negative electrode terminal joint 22 in which the negative electrode material is collected is formed at the other end side. The structure of the electrode body 20 is not particularly limited, and various structures used in general sealed secondary batteries can be adopted. In addition, the materials used for the positive and negative electrode materials are not particularly limited, but in this embodiment, aluminum is used for the positive electrode material and copper is used for the negative electrode material.

[0026] The electrode body 20 is housed in the case body 11 in a position in which the thickness direction and the longitudinal direction are parallel to the horizontal direction while being housed inside the bag body 40 described later. The electrode body 20 and the case body 11 are insulated by the bag body 40, which will be described in detail later.

[0027] [Positive and negative electrode configurations] In this embodiment, the secondary battery 1 includes a positive external terminal 25 and a negative external terminal 26 as external terminals, and a positive current collector terminal 27 and a negative current collector terminal 28 as current collector terminals, with the positive external terminal 25 and the positive current collector terminal 27 constituting a positive terminal PS, and the negative external terminal 26 and the negative current collector terminal 28 constituting a negative terminal NS. The secondary battery 1 of this embodiment also includes a positive electrode insulating member 29, a negative electrode insulating member 30, a positive electrode gasket 31, and a negative electrode gasket 32.

[0028] The positive electrode external terminal 25 and the negative electrode external terminal 26 are terminals for external connection, and are disposed on the front surface (upper surface) side of the sealing plate 12, and are located outside the case body 11. The positive electrode current collector terminal 27 and the negative electrode current collector terminal 28 are terminals for inputting and outputting electric power from the electrode body 20, and are disposed on the rear surface (lower surface) side of the sealing plate 12. In this embodiment, the positive electrode external terminal 25 and the positive electrode current collector terminal 27 are made of aluminum, and the negative electrode external terminal 26 and the negative electrode current collector terminal 28 are made of copper, but the materials of the external terminals 25, 26 and the current collector terminals 27, 28 are not particularly limited, and various metals and alloys having good conductivity can be used.

[0029] In this embodiment, the positive electrode insulating member 29, the negative electrode insulating member 30, the positive electrode gasket 31, and the negative electrode gasket 32 ​​are all members made of an insulating material, and in this embodiment, PFA resin is used as the material for these members.

[0030] Although detailed description will be omitted, in the secondary battery 1 of this embodiment, the positive electrode external terminal 25 and the negative electrode external terminal 26 are insulated from the sealing plate 12 by a positive electrode gasket 31 and a negative electrode gasket 32, respectively, and the positive electrode current collector terminal 27 and the negative electrode current collector terminal 28 are insulated from the sealing plate 12 by a positive electrode insulating member 29 and a negative electrode insulating member 30, respectively.

[0031] [Detailed configuration of bag body 40] Next, the bag body 40 will be described. Fig. 3 is a development view of the insulating film F constituting the bag body 40, Fig. 4 is a side view of the bag body 40 seen from the other side in the X-axis direction, and Fig. 5 is an enlarged cross-sectional view of the VV portion of Fig. 4. Fig. 6 is a cross-sectional view of the VI-VI portion of Fig. 2, and is a view for explaining the action and effect of the bag body 40.

[0032] 1 and 2, the bag body 40 has an opening at the top, and is disposed inside the case body 11 so that the opening faces the opening side of the case body 11. The bag body 40 accommodates the electrode body 20 therein, and insulates the case body 11 from the electrode body 20.

[0033] Specifically, the bag body 40 of this embodiment includes a pair of side portions 42a, 42b provided opposite to each other along the longitudinal direction (X-axis direction), a pair of end side portions 48a, 48b provided opposite to each other along the lateral direction (Y-axis direction), and a bottom surface portion 43 connecting the ends of the side portions 42a, 42b and the end side portions 48a, 48b located on the opposite side (lower side in the Z-axis direction) from the side where the opening is located. The electrode body 20 is accommodated inside the bag body 40 such that the side surface 20a, which is the long side surface of the electrode body 20, faces the side portions 42a, 42b, and both end surfaces 20b in the longitudinal direction (X-axis direction) of the electrode body 20 face the end side portions 48a, 48b. In this embodiment, the end surface 20b of the electrode body 20 corresponds to the "end surface parallel to the stacking direction in the electrode body".

[0034] In this embodiment, the bag body 40 is formed by folding a sheet of insulating and flexible resin insulating film F. Note that the insulating film F in this embodiment is a polypropylene film having a substantially square shape in a plan view, but is not limited thereto.

[0035] As shown in FIG. 3, the insulating film F has a rectangular first forming portion 41 which forms side portions 42a, 42b and a bottom portion 43, second forming portions 44a, 44b and third forming portions 46a, 46b which are arranged on both longitudinal sides (both sides in the X-axis direction) of the first forming portion 41 and form end side portions 48a, 48b, and complementary portions 50a, 50b which are respectively arranged between the second forming portion 44a and the third forming portion 46a on one longitudinal side and between the second forming portion 44b and the third forming portion 46b on the other longitudinal side.

[0036] Bend lines (valley fold lines) L1, L2 are formed at the boundaries between the first forming portion 41 and the second forming portions 44a, 44b, the third forming portions 46a, 46b, and the complementary portions 50a, 50b. Cut lines C1, C2, C3, and C4 are formed between the second forming portions 44a, 44b and the third forming portions 46a, 46b, and the complementary portions 50a, 50b, and cut lines C5, C6 along the X-axis direction are formed at the center of each of the complementary portions 50a, 50b in the Y-axis direction.

[0037] In each of the second forming portions 44a, 44b, a plurality of first through holes 45a, 45b opening to the front and back are formed at intervals along the Y-axis direction. In this embodiment, each of the third forming portions 46a, 46b also has a plurality of second through holes 47a, 47b opening to the front and back, similarly formed at intervals along the Y-axis direction.

[0038] In this embodiment, each of the third forming portions 46a, 46b has a large number of protrusions 52 (see FIG. 5) formed on the surface S2.

[0039] The bag body 40 is formed by folding the insulating film F along the folding lines L1 and L2 while making cuts in the insulating film F along the cutting lines C1, C2, C3, C4, C5, and C6. Specifically, the second forming parts 44a, 44b and the third forming parts 46a, 46b, which face each other with the complementary parts 50a, 50b in between, are overlapped with each other so that the second forming parts 44a, 44b are on the inside and the third forming parts 46a, 46b are on the outside, and each complementary part 50a, 50b is positioned on the inside of the second forming parts 44a, 44b. Then, in this state, the overlapped second forming parts 44a, 44b and the third forming parts 46a, 46b are bonded to each other. This results in the formation of a bag body 40 having two side portions 42a, 42b and a bottom portion 43 consisting of the first forming portion 41, and two end side portions 48a, 48b consisting of the second forming portions 44a, 44b and the third forming portions 46a, 46b (see Figure 1).

[0040] Next, the detailed configuration of the bag body 40 will be described with reference to Figures 4 and 5. Note that the bag body 40 of this embodiment has a structure in which one side and the other side in the longitudinal direction (X-axis direction) are approximately plane-symmetrical, so the other side in the X-axis direction will be described below as an example. Also, in Figures 4 and 5, the configuration on the other side in the Z-axis direction is denoted by a reference symbol, and the corresponding configuration on one side in the X-axis direction is also denoted by a reference symbol.

[0041] As shown in Fig. 4, the end side surface portions 48a, 48b of the bag body 40 have overlapping portions 49a, 49b formed by the second forming portions 44a, 44b and the third forming portions 46a, 46b overlapping with each other. The second forming portions 44a, 44b and the third forming portions 46a, 46b are located on both sides in the X-axis direction of the first forming portion 41 forming the side surface portions 42a, 42b, and are folded along the folding lines L1, L2 to overlap with each other to form the end side surface portions 48a, 48b. In other words, the second forming portions 44a, 44b are formed by folding an end portion of the insulating film F constituting one side surface portion 42a of the pair of side surface portions 42a, 42b of the bag body 40, and the third forming portions 46a, 46b are formed by folding an end portion of the insulating film F constituting the other side surface portion 42b of the pair of side surface portions 42a, 42b of the bag body 40. In this embodiment, the portions of the insulating film F that correspond to the second forming portions 44a, 44b correspond to the "electrode body side film", and the portions that correspond to the third forming portions 46a, 46b correspond to the "casing side film".

[0042] The overlapping portions 49a, 49b of the bag body 40 are portions where the second forming portions 44a, 44b and the third forming portions 46a, 46b overlap when viewed in the X-axis direction. The overlapping portions 49a, 49b have four first through holes 45a, 45b formed in the second forming portions 44a, 44b and four second through holes 47a, 47b formed in the third forming portions 46a, 46b and arranged at positions that do not overlap with the first through holes 45a, 45b when viewed in a direction perpendicular to the end side surface (when viewed in the X-axis direction). In other words, the overlapping portion 49a has the second forming portions 44a, 44b (electrode body side film) in which the first through holes 45a, 45b opening to the front and back are formed, and the third forming portions 46a, 46b (housing side film) in which the second through holes 47a, 47b are formed in positions that do not overlap the first through holes 45a, 45b formed in the second forming portions 44a, 44b when viewed in a direction perpendicular to the end side surface of the bag body 40. Note that the first through holes 45a, 45b and the second through holes 47a, 47b in this embodiment are holes with approximately rectangular openings, and four are formed in each of the second forming portions 44a, 44b and the third forming portions 46a, 46b, but the shape and number of the openings are not particularly limited.

[0043] Specifically, in this embodiment, the first through holes 45a, 45b are disposed at positions relatively close to the ends E2 of the third forming portions 46a, 46b as viewed in the X-axis direction. Meanwhile, the second through holes 47a, 47b are disposed at positions relatively farther from the ends E2 than the first through holes 45a, 45b so as not to overlap with the first through holes 45a, 45b as viewed in the X-axis direction.

[0044] In this way, by forming the first through holes 45a, 45b and the second through holes 47a, 47b in the bag body 40, communication of the electrolyte between the inside and outside of the bag body 40 is possible through these through holes, thereby reducing free liquid that does not directly affect the battery function.

[0045] In the secondary battery 1 of this embodiment, the third forming portions 46a, 46b, in which no through holes are formed, overlap the outer sides of the second forming portions 44a, 44b in which the first through holes 45a, 45b are formed. This results in a state in which the insulating film F is present between the case body 11 and the electrode body 20. Therefore, even if a free metal piece occurs in the battery case 10, it is unlikely that the free metal piece will connect the case body 11 and the electrode body 20 through the first through holes 45a, 45b.

[0046] Furthermore, in the secondary battery 1 of this embodiment, overlapping portions 49a, 49b are formed on the end side surface portions 48a, 48b facing the end surface 20b of the electrode body 20 from which the generated gas is likely to escape to the outside, and the first through holes 45a, 45b and the second through holes 47a, 47b are formed in the overlapping portions 49a, 49b. As a result, as shown in FIG. 6, the gas that has escaped from the end surface 20b of the electrode body 20 passes through the first through holes 45a, 45b, and is likely to escape from the bag body 40 through the gap between the end E2 of the third forming portions 46a, 46b and the second forming portions 44a, 44b, or through the second through holes 47a, 47b. Therefore, the bag body 40 is unlikely to be damaged by the force of the gas, and a portion where the insulating film F does not exist between the case body 11 and the electrode body 20 is unlikely to be formed.

[0047] In this embodiment, the second forming portions 44a, 44b and the third forming portions 46a, 46b are welded to each other on the side of the end E1 of the second forming portions 44a, 44b from the first through holes 45a, 45b and on the side of the end E1 of the second forming portions 44a, 44b from the second through holes 47a, 47b. Specifically, in this embodiment, the end E1 side of the second forming portions 44a, 44b and the vicinity of the boundary with the first forming portion 41 in the third forming portions 46a, 46b are partially welded, and a plurality of (four in this embodiment) adhesive portions 53a, 53b are formed at intervals along the Z-axis direction. That is, the second forming portions 44a, 44b and the third forming portions 46a, 46b are bonded to each other on the side of the end portion E1 of the second forming portions 44a, 44b rather than the first through holes 45a, 45b formed in the second forming portions 44a, 44b. Note that the method for bonding the insulating films together is not limited to welding, and may be a method of bonding them using an adhesive or the like.

[0048] In this manner, in the secondary battery 1 of the present embodiment, the second forming parts 44a, 44b and the third forming parts 46a, 46b are bonded to the end E1 of the second forming parts 44a, 44b, rather than the first through-holes 45a, 45b formed in the second forming parts 44a, 44b. This makes it difficult for the overlap to open due to the force of gas, and makes it difficult for a portion where the insulating film F does not exist to be formed between the case body 11 and the electrode body 20. In addition, as shown in FIG. 6, the gas that has passed through the first through-holes 45a, 45b can flow out of the bag body 40 through the gap between the end E2 of the third forming parts 46a, 46b and the second forming parts 44a, 44b or the second through-holes 47a, 47b, and the flow of the gas to the outside is not easily hindered by the adhesive parts 53a, 53b, so that the gas easily flows out of the bag body 40. Therefore, the bag body 40 is less likely to be damaged by the force of the gas, and as described above, there are less likely to be any locations between the case body 11 and the electrode body 20 where the insulating film F is not present.

[0049] Furthermore, in this embodiment, since the multiple adhesive parts 53a, 53b are formed at intervals along the Z-axis direction, the generated gas can pass between the multiple adhesive parts 53a, 53b. Therefore, as shown in Fig. 6, the gas that passes between the end E1 of the second forming parts 44a, 44b and the side surface part 42a can pass between the adhesive parts 53a, 53b, and then pass between the end E2 of the third forming parts 46a, 46b and the second forming parts 44a, 44b or through the second through holes 47a, 47b to go outside the bag body 40, making it easier for the gas to go out from the inside of the bag body 40 to the outside.

[0050] 5, in the secondary battery 1 of this embodiment, in the overlapping portions 49a, 49b, a number of protrusions 52 are formed on the surface S2 of the third forming portions 46a, 46b facing the second forming portions 44a, 44b. That is, in this embodiment, among the mutually opposing surfaces S1, S2 of the second forming portions 44a, 44b and the third forming portions 46a, 46b, a number of protrusions 52 protruding toward the surface S1 of the second forming portions 44a, 44b are formed on the surface S2 of the third forming portions 46a, 46b.

[0051] Therefore, in the secondary battery 1 of this embodiment, the second forming parts 44a, 44b and the third forming parts 46a, 46b are less likely to come into close contact with each other, and a gap is secured between the insulating films F. Therefore, the generated gas is more likely to escape to the outside of the bag body 40. Therefore, in the secondary battery 1, as described above, the bag body 40 is less likely to be damaged by the force of the gas, and a portion where the insulating film F is not present between the case body 11 and the electrode body 20 is less likely to occur. The shape and the amount of protrusion of the protrusion 52 are not particularly limited, and any shape and amount of protrusion that can prevent the second forming parts 44a, 44b and the third forming parts 46a, 46b from coming into close contact with each other and secure a gap between the insulating films F may be used.

[0052] As described above, according to the secondary battery 1 of this embodiment, it is difficult for free metal pieces or the like to connect the case body 11 and the electrode body 20 via the first through-holes 45a, 45b or the second through-holes 47a, 47b, and it is also difficult for a location where no insulating film F exists between the case body 11 and the electrode body 20 to occur. Therefore, according to the secondary battery 1 of this embodiment, it is possible to suppress the occurrence of a short circuit between the case body 11 and the electrode body 20 due to free metal pieces or the like.

[0053] [Another embodiment] [1] In the above embodiment, the through holes 45a, 45b, 47a, 47b are formed in both the second forming portions 44a, 44b and the third forming portions 46a, 46b (both the electrode body side film and the housing side film), but the present invention is not limited to such an embodiment. Of the electrode body side film and the housing side film, any embodiment may be used as long as a through hole is formed in at least the electrode body side film and a through hole is not formed in the housing side film at a position overlapping with the through hole of the electrode body side film when viewed in the X-axis direction.

[0054] [2] In the above embodiment, the first through holes 45a, 45b are arranged at a position relatively close to the end E2 of the third forming parts 46a, 46b when viewed in the X-axis direction, and the second through holes 47a, 47b are arranged at a position relatively far from the end E1 of the second forming parts 44a, 44b. However, the present invention is not limited to such an embodiment, and the first through holes 45a, 45b may be arranged at a position relatively close to the end E1 of the second forming parts 44a, 44b, and the second through holes 47a, 47b may be arranged at a position relatively far from the end E1. From the viewpoint of facilitating the discharge of gas that has passed through the first through holes 45a, 45b to the outside of the bag body 40, it is preferable to arrange the first through holes 45a, 45b at a position relatively close to the end E2 of the third forming parts 46a, 46b.

[0055] [3] In the above embodiment, the electrode body 20 is described as having a flat shape, but is not limited to such a shape. The electrode body 2 may have any shape as long as it has a laminated structure of a positive electrode material, a negative electrode material, and a separator.

[0056] [4] In the above embodiment, the second forming portions 44a, 44b and the third forming portions 46a, 46b are welded to each other on the side of the end E1 of the second forming portions 44a, 44b from the first through holes 45a, 45b and on the side of the end E1 of the second forming portions 44a, 44b from the second through holes 47a, 47b, but the present invention is not limited to such an embodiment. The adhesion points between the second forming portions 44a, 44b (electrode body side film) and the third forming portions 46a, 46b (housing side film) may be in any positions as long as they do not block the through holes formed therein. From the viewpoint of creating a structure in which the flow of gas that has passed through the first through holes 45a, 45b to the outside is less likely to be impeded by the adhesive portions 53a, 53b, it is preferable that the second forming portions 44a, 44b and the third forming portions 46a, 46b are adhered to the end portion E1 side of the second forming portions 44a, 44b rather than the first through holes 45a, 45b. In this case, for example, the adhesive points may be between the first through holes 45a, 45b and the second through holes 47a, 47b when viewed in the X-axis direction. Also, depending on the distance between the end side surface portions 48a, 48b of the bag body 40 and the inner surface of the end side wall 11b of the case body 11 and the width dimension (dimension in the Y-axis direction) of the third forming portions 46a, 46b, the second forming portions 44a, 44b and the third forming portions 46a, 46b may not be bonded to each other. That is, when the distance between the end side surface portions 48a, 48b of the bag body 40 and the inner surface of the end side wall 11b of the case body 11 is short or the width of the third forming portions 46a, 46b is large, even if the third forming portions 46a, 46b of the bag body 40 are opened so as to be separated from the second forming portions 44a, 44b, the third forming portions 46a, 46b are present at positions overlapping with the first through holes 45a, 45b as viewed in the X-axis direction, the second forming portions 44a, 44b and the third forming portions 46a, 46b may not be bonded to each other.

[0057] [5] In the above embodiment, a configuration in which a large number of protrusions 52 are formed on the surface S2 of the third forming parts 46a, 46b facing the second forming parts 44a, 44b in the overlapping parts 49a, 49b has been described, but the present invention is not limited to such a configuration. Any of a configuration in which protrusions are formed on the surface S1 of the second forming parts 44a, 44b facing the third forming parts 46a, 46b, a configuration in which protrusions are not formed on both the second forming parts 44a, 44b (electrode body side film) and the third forming parts 46a, 46b (housing side film) and a configuration in which protrusions are formed on both may be used.

[0058] In addition, the configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, provided no contradiction arises. Furthermore, the embodiments disclosed in this specification are illustrative, and the embodiments of the present invention are not limited thereto, and can be appropriately modified within the scope that does not deviate from the purpose of the present invention. [Explanation of symbols]

[0059] 1: Secondary battery 11: Case body (housing) 12: Sealing plate (lid body) 20: Electrode body 20a: Side 20b: End face 40: Bag body 42a: Side part (one side part) 42b: Side part (other side part) 44a, 44b: Second forming portion (electrode body side film) 45a, 45b: 1st through hole 46a, 46b: third forming portion (casing side film) 47a, 47b: 2nd through hole 48a, 48b: End side part 49a, 49b: overlapping portion 52: Protrusion E1: End (end of the film on the electrode body side) F: Insulating film

Claims

1. A housing having an opening; An electrode assembly housed in the housing; A bag body disposed inside the housing and insulating the housing from the electrode body; and a cover that seals the opening of the housing, The electrode body is formed by laminating a positive electrode material and a negative electrode material with a separator interposed therebetween, The bag body is It is made of an insulating film, The electrode body has an overlapping portion formed by the insulating film overlapping an end side surface portion opposite to an end surface parallel to a lamination direction of the electrode body, The overlapping portion is an electrode body side film having through holes opening on the front and back sides; a housing side film in which, when viewed in a direction perpendicular to the end side surface of the bag body, no through hole is formed in a position overlapping with the through hole formed in the electrode body side film.

2. The electrode body has a flat shape, the electrode body side film is formed by folding an end portion of the insulating film constituting one of a pair of side surface portions of the bag body facing a side surface of the electrode body, the housing-side film is formed by folding an end portion of the insulating film that constitutes the other of the pair of side surface portions of the bag body, The secondary battery according to claim 1 , wherein the electrode body side film and the case side film are bonded to each other at a position closer to an end of the electrode body side film than the through hole formed in the electrode body side film.

3. The secondary battery according to claim 1 , wherein at least one of the mutually opposing surfaces of the electrode body side film and the housing side film has one or more protrusions formed thereon that protrude toward the other surface.

4. The secondary battery according to any one of claims 1 to 3, wherein the housing side film has a through hole that opens to the front and back at a position that does not overlap with the through hole formed in the electrode body side film when viewed in a direction perpendicular to the end side surface.

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