Secondary battery

Abstract

To provide a secondary battery capable of preventing friction between a lid body and a housing when an electrode body is inserted into the housing, and suppressing deterioration in battery performance caused by compression collapse of an electrode body end face.SOLUTION: A secondary battery includes: a casing 11 having an opening; an electrode body 20 housed in the casing 11; a bag body that is disposed inside the casing 11 and insulates between the casing 11 and the electrode body 20; and a lid body 12 that seals the opening of the casing 11. The electrode body 20 is formed by laminating a positive electrode material and a negative electrode material via a separator. The bag body is formed of an insulating film and has bent overlapping portions 45a, 45b, 46a, 46b formed by bending and overlapping the insulating film. The bent overlapping portions 45a, 45b, 46a, 46b are formed on at least part of both end side surfaces facing end surfaces 24a, 24b in parallel to a lamination direction in the electrode body 20.SELECTED DRAWING: Figure 6

Description

Technical Field

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

Background Art

[0002] Conventionally, as a secondary battery used in an electric vehicle having a motor as a drive source, such as an electric vehicle or a hybrid vehicle, for example, a secondary battery disclosed in Patent Document 1 has been proposed.

[0003] The secondary battery described in Patent Document 1 includes a wound body formed by winding a positive electrode foil, a negative electrode foil, and a separator in a stacked state, a case in which the wound body is accommodated, a current collecting component joined to the wound body, an electrode component joined to the current collecting component, a lid to which the current collecting component and the electrode component are attached, and an insulating film accommodated in the case in a state of being assembled in a bag shape so as to wrap the wound body. In this secondary battery, the wound body is crushed into a flat shape and has a flat portion with a flat surface when viewed in a direction orthogonal to the winding direction, and curved portions with a curved surface above and below the flat portion. And, in this secondary battery, a part of the insulating film is folded at a position facing a portion extending from the boundary between one surface of the flat portion of the wound body and the lower curved portion to the tip of the lower curved portion, and has an overlapping portion where the thickness is increased compared to other portions.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Here, in the secondary battery described in Patent Document 1, when inserting the wound body or the insulating film into the case, if the overlapping portion of the insulating film contacts the case, a pressing force acts on one surface of the flat portion of the wound body. As a result, the wound body is inserted into the case in an inclined state. Therefore, the lid to which the current collecting component joined to the wound body is attached is also inclined in the same manner, and there is a possibility that the lid and the case rub against each other and metal foreign matter is generated. And when the generated metal foreign matter enters the case, the metal foreign matter can cause a short circuit.

[0006] Further, in the secondary battery described in Patent Document 1, when the wound body shakes due to an external disturbance or the like, the surface of the flat portion or the surface of the bent portion of the wound body is prevented from contacting the case by the buffering effect of the overlapping portion, while the end faces of the wound body (the surfaces at both ends in the winding direction) collide with the inner wall of the case. As a result, the foil ends gathered at the end faces of the wound body are compressed and crushed, making it difficult for the electrolytic solution to enter the inside of the wound body (between the electrode foils), and thus the battery performance may deteriorate.

[0007] That is, in the secondary battery described in Patent Document 1, there is a possibility that the lid and the case rub against each other and metal foreign matter is generated when the wound body is inserted into the case, and there is also a possibility that the battery performance deteriorates due to the compression and crushing of the end faces of the wound body.

[0008] The present invention has been made in view of the above circumstances, and an object thereof is to provide a secondary battery that can prevent rubbing between the lid and the case when the electrode body is inserted into the housing, and can suppress a decrease in battery performance caused by compression and crushing of the end faces of the electrode body.

Means for Solving the Problems

[0009] The characteristic configuration of the secondary battery according to the present invention for achieving the above object is a housing having an opening, an electrode body housed in the housing, a bag body disposed inside the housing and insulating between the housing and the electrode body, and a lid for sealing 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, and is attached to the lid body via a battery terminal. The bag body is made of an insulating film, has a bent overlapping portion formed by bending and overlapping the insulating film, and the bent overlapping portion is formed at least in part on both end side surfaces facing the end surface parallel to the lamination direction in the electrode body.

[0010] According to the above characteristic configuration, when the electrode body and the bag body are inserted into the housing, repulsive forces derived from the bent overlapping portion of the bag body act on both end surfaces of the electrode body, and the relative position between the housing and the electrode body is adjusted so that the repulsive forces become uniform. Therefore, rubbing between the lid body and the housing can be prevented. Further, according to the above characteristic configuration, even if the electrode body moves in the housing due to an external disturbance or the like, the buffer effect of the bent overlapping portion of the bag body makes it difficult for the foil-shaped electrode material to be compressed and crushed due to the collision between the end surface of the electrode body and the housing. Therefore, it is also difficult for the problem that the electrolyte hardly penetrates into the electrode body and the battery performance deteriorates to occur.

[0011] A further characteristic configuration of the secondary battery according to the present invention is that an electrolyte is injected into the housing, and the bent overlapping portion is formed on both end side surfaces of the bag body such that the lower end thereof is positioned below the liquid level of the electrolyte in the state where the secondary battery is standing upright, and the upper end is positioned above the liquid level of the electrolyte.

[0012] According to the above characteristic configuration, the bent overlapping portion always contacts the end surface of the electrode body, and in the state where the secondary battery is standing upright, the lower end of the bent overlapping portion is in contact with the electrolyte. Therefore, the electrolyte is held between the films of the bent overlapping portion and between the bent overlapping portion and the end surface of the electrode body due to the interfacial tension. Therefore, it is easy to secure the contact area between the electrolyte and the end surface of the electrode body, and it is easy to effectively utilize the electrolyte.

[0013] A further characteristic configuration of the secondary battery according to the present invention is The bent overlapping part is formed over the entire vertical direction on both end side surfaces of the bag body.

[0014] According to the above characteristic configuration, repulsive forces act on the entire end surfaces of both the electrode body, so the relative position between the housing and the electrode body is easily adjusted, and rubbing between the lid body and the housing is more easily prevented. Also, the above-mentioned compressive collapse is less likely to occur over the entire end surface of the electrode body. Therefore, the problem of deterioration of battery performance is less likely to occur. Furthermore, the contact area between the electrolytic solution and the end surface of the electrode body is likely to increase. Therefore, the electrolytic solution can be utilized more effectively.

Effects of the Invention

[0015] As described above, according to the secondary battery of the present invention, rubbing between the lid body and the housing when the electrode body is inserted into the housing can be prevented, and a decrease in battery performance due to compressive collapse of the end surface of the electrode body can be suppressed.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying out the Invention

[0017] Hereinafter, a secondary battery according to an embodiment of the present invention will be described with reference to the drawings. In the following, a mode in which the secondary battery is a lithium-ion secondary battery will be described as an example. Also, in the following, for the sake of clarity, each description and each drawing are appropriately simplified.

[0018] 〔Outline of Secondary Battery 1〕 FIG. 1 is an exploded perspective view of the secondary battery according to the present embodiment. FIG. 2 is a cross-sectional view showing the schematic configuration of the secondary battery according to the present 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 vertical direction, the X-axis direction and the Y-axis direction are orthogonal to each other, and are parallel to the horizontal direction.

[0019] As shown in FIGS. 1 and 2, the secondary battery 1 includes a battery case 10 composed of a case body 11 and a sealing plate 12, metal battery terminals PS and NS, an electrode body 20, a bag body 40, and the like. The secondary battery 1 is a sealed secondary battery in which the electrode body 20, a part of the battery terminals PS and NS, the bag body 40, etc. are accommodated inside the case body 11, the opening of the case body 11 is sealed with the sealing plate 12, and then the electrolytic solution E is injected into the case body 11.

[0020] 〔Configuration of Battery Case 10〕 As shown in FIGS. 1 and 2, the battery case 10 of the present 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 the present embodiment, both the case body 11 and the sealing plate 12 are made of aluminum, but it is not limited thereto. Various metals and alloys can be used as the materials for the case body 11 and the sealing plate 12. In the present embodiment, the case body 11 corresponds to the "housing", and the sealing plate 12 corresponds to the "lid body".

[0021] In the present 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.

[0022] 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 composed of a flat plate member having a substantially rectangular shape when viewed in the Z-axis direction. On the sealing plate 12, a positive electrode battery terminal PS is disposed at one end in the longitudinal direction (one end in the X-axis direction), and a negative electrode battery terminal NS is disposed at the other end in the longitudinal direction (the other end in the X-axis direction). The sealing plate 12 is joined to the case body 11 by laser welding or the like so as to close the opening of the case body 11.

[0023] 〔Configuration of the electrode body 20〕 The electrode body 20 is formed by laminating a positive electrode material and a negative electrode material with a separator interposed therebetween, and is housed in the case body 11. The electrode body 20 of the present embodiment is configured as a wound body obtained by winding a long strip-shaped positive electrode material and a negative electrode material in a laminated state with a strip-shaped separator interposed therebetween and compressing it into a flat shape. As shown in FIGS. 1 and 2, the electrode body 20 is substantially rectangular in a thickness direction view (Y-axis direction view), and a positive electrode terminal bonding portion 21 where the positive electrode material is collected and foiled is formed on one end side in the longitudinal direction (X-axis direction) in the thickness direction view, and a negative electrode terminal bonding portion 22 where the negative electrode material is collected and foiled is formed on the other end side. Note that the structure of the electrode body 20 is not particularly limited, and various structures used in general sealed secondary batteries can be adopted. Also, aluminum is used for the positive electrode material and copper is used for the negative electrode material.

[0024] The electrode body 20 is housed inside the case body 11 in a posture where the thickness direction and the longitudinal direction are parallel to the horizontal direction while being housed inside the bag body 40 described later. Although details will be described later, the electrode body 20 is insulated from the case body 11 by the bag body 40.

[0025] 〔Configuration of Positive Electrode Side and Negative Electrode Side〕 In the present embodiment, the secondary battery 1 includes a positive electrode external terminal 25 and a negative electrode external terminal 26 as external terminals, and a positive electrode current collecting terminal 27 and a negative electrode current collecting terminal 28 as current collecting terminals. The positive electrode battery terminal PS is composed of the positive electrode external terminal 25 and the positive electrode current collecting terminal 27, and the negative electrode battery terminal NS is composed of the negative electrode external terminal 26 and the negative electrode current collecting terminal 28. Note that in the present embodiment, the positive electrode external terminal 25 and the positive electrode current collecting terminal 27 are made of aluminum, and the negative electrode external terminal 26 and the negative electrode current collecting terminal 28 are made of copper. However, the materials of the respective external terminals 25, 26 and the respective current collecting terminals 27, 28 are not particularly limited, and various metals and alloys having good conductivity can be used.

[0026] Also, in the present embodiment, the secondary battery 1 has a positive electrode insulating member 29, a negative electrode insulating member 30, a positive electrode gasket 31, and a negative electrode gasket 32, all of which are made of insulating materials. In the present embodiment, a PFA resin is used as the insulating material, but it is not limited thereto.

[0027] Although detailed description is omitted, in the secondary battery 1 of the present embodiment, the positive electrode external terminal 25 and the negative electrode external terminal 26 and the sealing plate 12 are insulated by the positive electrode gasket 31 and the negative electrode gasket 32, respectively, and the positive electrode current collecting terminal 27 and the negative electrode current collecting terminal 28 and the sealing plate 12 are insulated by the positive electrode insulating member 29 and the negative electrode insulating member 30, respectively. Further, each current collecting terminal 27, 28 has connection portions 27a, 28a, and the connection portions 27a, 28a are joined to the terminal joining portions 21, 22.

[0028] 〔Configuration of the bag body 40〕 Next, the bag body 40 will be described in detail. FIG. 3 is a cross-sectional view of the III-III portion in FIG. 2. FIG. 4 is a developed view of the insulating film F constituting the bag body 40. FIG. 5 is a schematic view showing a state when the electrode body 20 is inserted into the case body 11, and FIG. 6 is a schematic view showing a state in which the contact area between the electrolytic solution E and the end faces 24a, 24b of the electrode body 20 is increased.

[0029] As shown in FIGS. 1 to 3, the bag body 40 has an opening at the upper part and is disposed inside the case body 11 such that the opening faces the opening side of the case body 11. Further, the bag body 40 houses the electrode body 20 therein and insulates between the case body 11 and the electrode body 20.

[0030] Specifically, the bag body 40 of the present embodiment includes a pair of side surface portions 41a and 41b provided to face each other along the longitudinal direction (X-axis direction), a pair of end side surface portions 42a and 42b provided to face each other along the short side direction (Y-axis direction), and a bottom surface portion 43 located on the side opposite to the side where the opening is located (lower side in the Z-axis direction). Further, each of the end side surface portions 42a and 42b includes end side surface pieces 44a and 44b, and bending overlapping portions 45a, 45b, 46a, and 46b. Inside the bag body 40, the side surfaces 23a and 23b, which are the long side surfaces of the electrode body 20, face the side surface portions 41a and 41b, and the electrode body 20 is accommodated such that both end surfaces 24a and 24b in the longitudinal direction (X-axis direction) of the electrode body 20 face the end side surface portions 42a and 42b. That is, the end side surface portions 42a and 42b of the bag body 40 face the end surfaces 24a and 24b parallel to the stacking direction in the electrode body 20. In the present embodiment, the end side surface portions 42a and 42b correspond to the "end side surfaces".

[0031] In the present embodiment, the bag body 40 is formed by folding a single insulating film F having insulating properties and flexibility. In the present embodiment, the insulating film F is a polypropylene film having a substantially rectangular shape in plan view, but is not limited thereto.

[0032] As shown in FIG. 4, the insulating film F has a first forming portion F1 that forms the side surface portions 41a and 41b and the bottom surface portion 43 of the bag body 40, second and third forming portions F2 and F3 that form the respective end side surface pieces 44a and 44b, and fourth, fifth, sixth, and seventh forming portions F4, F5, F6, and F7 that form the respective bending overlapping portions 45a, 45b, 46a, and 46b.

[0033] The first forming portion F1 has a substantially rectangular shape in plan view, with both sides in the direction parallel to the short side direction forming the side surface portions 41a and 41b, and the center forming the bottom surface portion 43.

[0034] The second forming portion F2 is disposed at one side in the longitudinal direction and the center in the short side direction of the first forming portion F1, and the third forming portion F3 is disposed at the other side in the longitudinal direction and the center in the short side direction of the first forming portion F1.

[0035] The fourth forming part F4 and the fifth forming part F5 are arranged so as to sandwich the second forming part F2 on one longitudinal side of the first forming part F1. The sixth forming part F6 and the seventh forming part F7 are arranged so as to sandwich the third forming part F3 on the other longitudinal side of the first forming part F1.

[0036] At the boundary between the first forming part F1 and the second to seventh forming parts F2 to F7, bending lines (valley folding lines) L1, L2, L3, L4, L5, L6 are formed. Also, cut lines C1, C2 are formed between the second forming part F2 and the fourth and fifth forming parts F4, F5, and cut lines C3, C4 are formed between the third forming part F3 and the sixth and seventh forming parts F6, F7. Note that in the first forming part F1, bending lines (valley folding lines) L11, L12 are formed between the part forming the side faces 41a, 41b and the part forming the bottom face 43.

[0037] In addition, a plurality of bending lines (four for each forming part in this embodiment) L7, L8, L9, L10 parallel to the bending lines L1 to L6 are formed in the fourth to seventh forming parts F4 to F7. Note that the bending lines L7, L9 are mountain folding lines, and the bending lines L8, L10 are valley folding lines.

[0038] The bag body 40 is formed by making cuts in the insulating film F along the cut lines C1 to C4 and then folding the insulating film F along each of the bending lines L1 to L12.

[0039] Specifically, the folding lines L7 to L10 are folded at the fourth forming part F4 to the seventh forming part F7. Further, the second forming part F2, the fourth forming part F4, and the fifth forming part F5 are overlapped so that the fifth forming part F5 is located on one side and the fourth forming part F4 is located on the other side with the second forming part F2 in between. Furthermore, the third forming part F3, the sixth forming part F6, and the seventh forming part F7 are overlapped so that the seventh forming part F7 is located on one side and the sixth forming part F6 is located on the other side with the third forming part F3 in between. As a result, a bag body 40 is formed which includes two side surface parts 41a, 41b and a bottom surface part 43 formed by the first forming part F1, and an end side surface part 42a composed of an end side surface piece 44a formed by the second forming part F2 and folding overlapping parts 45a, 45b formed by the fourth and fifth forming parts F4, F5, and an end side surface part 42b composed of an end side surface piece 44b formed by the third forming part F3 and folding overlapping parts 46a, 46b formed by the sixth and seventh forming parts F6, F7 (see FIGS. 1 to 3). Note that the bag body 40 maintains its shape in a state where the forming parts are not adhered to each other (non-adhered state) when housed inside the case body 11. Therefore, in the present embodiment, when forming the bag body 40, the step of adhering the insulating film F to a predetermined part is unnecessary, and thus the steps required for manufacturing the bag body 40 can be reduced.

[0040] Next, the detailed configuration of the bag body will be described. As shown in FIGS. 1 to 3, the end side surface parts 42a, 42b of the bag body 40 have folding overlapping parts 45a, 45b, 46a, 46b formed by folding the fourth forming part F4 to the seventh forming part F7 a plurality of times on both sides in the X-axis direction with the respective end side surface pieces 44a, 44b in between. Further, in the bag body 40 of the present embodiment, the folding overlapping parts 45a, 45b, 46a, 46b are formed over the entire region in the vertical direction (Z-axis direction) of the respective end side surface parts 42a, 42b.

[0041] In addition, in the present embodiment, the fourth forming portion F4 and the sixth forming portion F6 are formed by bending the end portion of the insulating film F that constitutes one of the pair of side portions 41a and 41b of the bag body 40, i.e., the side portion 41b. On the other hand, the fifth forming portion F5 and the seventh forming portion F7 are formed by bending the end portion of the insulating film F that constitutes the other side portion 41a of the pair of side portions 41a and 41b of the bag body 40. That is, the end side portions 42a and 42b of the bag body 40 have a configuration in which the bending overlapping portions 45a, 45b, 46a, and 46b are arranged on both sides sandwiching the insulating film F (end side surface pieces 44a and 44b) that constitutes a part of the end side portions 42a and 42b. Further, each of the bending overlapping portions 45a, 45b, 46a, and 46b is formed by bending the end portion of the insulating film F that constitutes each side portion 41a and 41b a plurality of times.

[0042] In the present embodiment, each of the bending overlapping portions 45a, 45b, 46a, and 46b is formed by overlapping five layers of the insulating film F (see FIG. 3). Therefore, each of the end side portions 42a and 42b is composed of two bending overlapping portions 45a, 45b, 46a, and 46b and the end side surface pieces 44a and 44b made of one layer of the insulating film F, and the insulating film F is in a state of overlapping 11 layers respectively.

[0043] Furthermore, in the present embodiment, in a state where the secondary battery 1 is stationary with the sealing plate 12 facing upward (the state where the secondary battery is standing upright), the lower ends of each of the bending overlapping portions 45a, 45b, 46a, and 46b are located below the liquid level of the electrolytic solution E, and the upper ends are located above the liquid level of the electrolytic solution E. More specifically, in a state where the secondary battery 1 is standing upright, a plane parallel to the horizontal direction including the lowermost portion in each of the bending overlapping portions 45a, 45b, 46a, and 46b is located below the liquid level of the electrolytic solution E, and a plane parallel to the horizontal direction including the uppermost portion is located above the liquid level of the electrolytic solution E.

[0044] In the secondary battery 1 having the above configuration, when assembling the secondary battery 1, when inserting the electrode body 20 and the bag body 40 (insulating film F) into the case main body 11, as shown in FIG. 5, both end faces 24a and 24b of the electrode body 20 are bent and overlapped with the inner wall surface of the case main body 11. Parts 45a, 45b, 46a, and 46b are in a positioned state. Thereby, the repulsive forces derived from the bent overlapping parts 45a, 45b, 46a, and 46b act on the two end faces 24a and 24b of the electrode body 20. Therefore, the electrode body 20 is inserted into the case main body 11 while the relative position between the case main body 11 and the electrode body 20 is adjusted so that the repulsive force becomes uniform. As a result, rubbing between the sealing plate 12 and the case main body 11 is prevented.

[0045] Further, in the secondary battery 1 of the present embodiment, the bent overlapping parts 45a, 45b, 46a, and 46b are located over the entire vertical direction between the end faces 24a and 24b of the electrode body 20 and the case main body 11. Thereby, even if the electrode body 20 moves in a direction in which the end faces 24a and 24b come into contact with the inner wall surface of the case main body 11 due to an external disturbance or the like, due to the buffering effect of the bent overlapping parts 45a, 45b, 46a, and 46b, the end faces 24a and 24b of the electrode body 20 are prevented from colliding with the case main body 11 in the entire vertical direction, and it is difficult for the electrode material to be compressed and crushed. Therefore, the problem that the electrolyte E hardly enters the inside of the electrode body 20 due to the compression and collapse of the end faces 24a and 24b hardly occurs, and the problem of deterioration of battery performance caused by this hardly occurs.

[0046] Furthermore, in the present embodiment, the bent overlapping portions 45a, 45b, 46a, and 46b have their lower ends positioned below the liquid level of the electrolytic solution E and their upper ends positioned above the liquid level of the electrolytic solution E. As a result, as shown in FIG. 6, between the insulating films F constituting the bent overlapping portions 45a, 45b, 46a, and 46b, between the bent overlapping portions 45a, 45b, 46a, and 46b and the end side surface pieces 44a and 44b, and between the bent overlapping portions 45a, 45b, 46a, and 46b and the end faces 24a and 24b of the electrode body 20, the electrolytic solution E is held by the interfacial tension. Therefore, the contact area between the electrolytic solution E and the end faces 24a and 24b of the electrode body 20 is ensured, and the electrolytic solution E can be effectively utilized.

[0047] 〔Alternative Embodiment〕 〔1〕In the above embodiment, the aspect in which each end side surface portion 42a, 42b of the bag body 40 is composed of the end side surface pieces 44a, 44b and the two bent overlapping portions 45a, 45b, 46a, 46b has been described, but it is not limited to such an aspect. The bag body may be, for example, an aspect having a configuration as shown in FIGS. 7 to 9. FIGS. 7 to 9 are diagrams for explaining the configuration and effects of the bag body 50 according to an alternative embodiment. FIG. 7 is a developed view of the insulating film G constituting the bag body 50, FIG. 8 is a perspective view showing the bag body 50, and FIG. 9 is a cross-sectional view showing the periphery of the bent overlapping portions 57a, 57b of the bag body 50 of the secondary battery according to the alternative embodiment. Further, FIG. 10 is a schematic diagram showing a state in which the contact area between the end faces 24a, 24b of the electrode body 20 and the electrolytic solution E has increased in the secondary battery according to the alternative embodiment. In FIGS. 9 and 10, the same reference numerals as those in FIGS. 1 to 3 are given to the components of the secondary battery other than the bag body 50.

[0048] The bag body 50 according to another embodiment is formed by bending a single insulating film G shown in FIG. 7. The insulating film G has two rectangular side portions 51a and 51b, end side pieces 54a, 54b, 55a, 55b that are arranged on both longitudinal sides of each side portion 51a, 51b and constitute end side faces 52a, 52b, a bottom portion 53 that is arranged between the two side portions 51a, 51b, and supplementary portions 56a, 56b that are arranged between both longitudinal sides of the bottom portion 53 and the end side pieces 54a, 54b, 55a, 55b.

[0049] Bending lines (valley folding lines) M1, M2, M3, M4 are formed at the boundary portions between the two side portions 51a, 51b and the respective end side pieces 54a, 54b, 55a, 55b. Also, bending lines (valley folding lines) M5, M6 are formed at the boundary portions between each side portion 51a, 51b and the bottom portion 53. At the boundary portions between the respective end side pieces 54a, 54b, 55a, 55b and the supplementary portions 56a, 56b, bending lines (valley folding lines) M7, M8, M9, M10 are formed that extend from each side of the insulating film F corresponding to each of the end side pieces 54a, 54b, 55a, 55b toward the bending lines (valley folding lines) M1, M2, M3, M4 and form an angle of 45° with the corresponding bending lines (valley folding lines) M1, M2, M3, M4. Further, bending lines (mountain folding lines) M11, M12, M13, M14 are formed in the supplementary portions 56a, 56b so as to extend from both ends of the bending lines (valley folding lines) M5, M6. Also, bending lines (valley folding lines) M15, M16 are formed at the boundary portions between the bottom portion 53 and the supplementary portions 56a, 56b.

[0050] The bag body 50 is formed by folding the insulating film G along each folding line M1 to M16. Specifically, as shown in FIG. 8, the bag body 50 includes a pair of side surface portions 51a and 51b provided opposite to each other along the longitudinal direction (X-axis direction), a pair of end side surface portions 52a and 52b provided opposite to each other along the short side direction (Y-axis direction), and a bottom surface portion 53 connecting the lower ends of the side surface portions 51a and 51b and the end side surface portions 52a and 52b. Further, each of the end side surface portions 52a and 52b has folding overlapping portions 57a and 57b at its lower end side. In this bag body 50, the folding overlapping portions 57a and 57b are formed by overlapping end side surface pieces 54a, 54b, 55a, 55b and supplementary portions 56a, 56b, and as shown in FIG. 9, it is a portion where the insulating film G overlaps up to five layers at most.

[0051] As shown in FIG. 10, in the secondary battery including this bag body 50, folding overlapping portions 57a and 57b are formed at the lower end sides of the respective end side surface portions 52a and 52b. In the state where the secondary battery is erected, the lower ends of the folding overlapping portions 57a and 57b are located below the liquid level of the electrolytic solution E, and the upper ends are located above the liquid level of the electrolytic solution E.

[0052] Therefore, similar to the above, when the electrode body 20 and the bag body 50 (insulating film G) are inserted into the case body 11, the relative positions of the case body 11 and the electrode body 20 are adjusted, so that rubbing between the sealing plate 12 and the case body 11 can be prevented. Further, due to the buffering effect of the folding overlapping portions 57a and 57b, compression collapse of the electrode material hardly occurs at the lower ends of the end faces 24a and 24b of the electrode body 20. In the state where the secondary battery is erected, between the insulating films G constituting the folding overlapping portions 57a and 57b (specifically, between the supplementary portions 56a and 56b and the respective end side surface pieces 54a, 54b, 55a, 55b) and between the folding overlapping portions 57a and 57b (specifically, the supplementary portions 56a and 56b) and the lower end sides of the end faces 24a and 24b of the electrode body 20, the electrolytic solution E is held by interfacial tension. Thus, the contact area between the electrolytic solution E and the end faces 24a and 24b of the electrode body 20 can be ensured, and the electrolytic solution E can be effectively utilized.

[0053] 〔2〕In the above embodiment, the folded overlapping portions 45a, 45b, 46a, and 46b are formed over the entire vertical direction (Z-axis direction) of the respective end side surfaces 42a and 42b. However, the present invention is not limited to such an embodiment. The folded overlapping portion may be formed in at least a part of the vertical direction of each end side surface. Even in such an embodiment, rubbing between the sealing plate and the case body can be prevented. Further, since the compression collapse of the electrode material can be prevented by the buffering effect of the folded overlapping portion, the occurrence of problems such as a decrease in battery performance can be suppressed.

[0054] 〔3〕In the above embodiment, the lower ends of the folded overlapping portions 45a, 45b, 46a, and 46b are located below the liquid level of the electrolytic solution E in the state where the secondary battery is erected, and the upper ends are located above the liquid level of the electrolytic solution E. However, the present invention is not limited to such an embodiment. From the viewpoints of preventing rubbing between the sealing plate and the case body and preventing compression collapse of the electrode material at the end face of the electrode body, the positions of the upper and lower ends of the folded overlapping portions 45a, 45b, 46a, and 46b are not particularly limited.

[0055] In addition, the configurations disclosed in the above embodiments (including other alternative embodiments, the same applies hereinafter) can be applied in combination with the configurations disclosed in other embodiments as long as no contradiction occurs. Further, the embodiments disclosed in this specification are merely examples, and the embodiments of the present invention are not limited thereto, and can be appropriately modified within the scope not departing from the object of the present invention.

Explanation of Reference Numerals

[0056] 1: Secondary battery 11: Case body (housing) 12: Sealing plate (lid) 20: Electrode body 23a, 23b: Side surface 24a, 24b: End face (end face parallel to the stacking direction) 40: Bag body 42a, 42b: End side surface portion (end side surface) 45a, 45b, 46a, 46b: Folded overlapping portion 50: Bag body 52a, 52b: End side faces (end side surfaces) 57a, 57b: Folded overlapping parts PS: Positive electrode battery terminal (battery terminal) NS: Negative electrode battery terminal (battery terminal) E: Electrolyte F: Insulating film G: Insulating film

Claims

1. A housing having an opening, An electrode body housed in the housing, A bag body disposed inside the housing and insulating between the housing and the electrode body, A lid body for sealing the opening of the housing, and is provided with, The electrode body is formed by laminating a positive electrode material and a negative electrode material via a separator, and is attached to the lid body via a battery terminal, The bag body is, Made of an insulating film, The insulating film has a bent overlapping portion formed by being bent and overlapped, The bent overlapping portion is formed on at least a part of both end side surfaces facing an end surface parallel to the stacking direction in the electrode body, a secondary battery.

2. An electrolytic solution is injected into the housing, The bent overlapping portion is formed on both end side surfaces of the bag body such that its lower end is located below the liquid level of the electrolytic solution in a state where the secondary battery stands upright and its upper end is located above the liquid level of the electrolytic solution, the secondary battery according to claim 1.

3. The bent overlapping portion is formed over the entire vertical direction on both end side surfaces of the bag body, the secondary battery according to claim 1 or 2.

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