Secondary battery

Abstract

To prevent damage of a separator, thereby preventing short-circuiting between electrodes.SOLUTION: A battery stack 1 comprises: a wound body 30 in which a positive electrode sheet 50, a negative electrode sheet 40, and a separator 45 disposed between the positive electrode sheet 50 and the negative electrode sheet 40 are wound, and which has an inclined part 35 that is inclined from a power generation part 31, formed into a flat shape, to the inner side in the thickness direction of the power generation part 31 so as to be connected to a current collecting part; a case 12 which houses the wound body 30 together with an electrolyte; and a first rib 73 having a tapered surface 73A whose pressing surface to be pressed against the inclined part 35 via the case 12 is inclined corresponding to the inclined part 35.SELECTED DRAWING: Figure 7

Description

Technical Field

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

Background Art

[0002] In a secondary battery, it is known that a wound body is housed in a case together with an electrolytic solution (see, for example, Patent Document 1).

[0003] Patent Document 1 discloses a wound lithium-ion secondary battery in which a wound electrode body is enclosed together with an electrolytic solution inside a flat rectangular case.

[0004] By the way, in a secondary battery, it is preferable to suppress the electrolytic solution from being pushed out in the winding axis direction.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In consideration of the above facts, an object of the present invention is to provide a secondary battery in which the electrolytic solution is suppressed from being pushed out in the winding axis direction.

Means for Solving the Problems

[0007] The secondary battery according to the first aspect of the present invention includes a wound body including a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet, the wound body being formed in a flat shape and having an inclined portion that is inclined inward in the thickness direction of the power generation portion and connected to a current collecting portion, a case in which the wound body is housed together with an electrolytic solution, and a first rib having a tapered surface that is inclined so that a pressing surface pressed against the inclined portion via the case corresponds to the inclined portion.

[0008] In the secondary battery according to the second aspect of the present invention, in the secondary battery according to the first aspect of the present invention, an exterior film covering the wound body is provided, and a folded portion where the exterior film is folded is formed at a portion corresponding to the inclined portion of the exterior film.

[0009] In the secondary battery according to the third aspect of the present invention, the secondary battery according to the first aspect or the second aspect of the present invention, and the width of the tapered surface is formed wider than the width of the folded portion.

[0010] In the secondary battery according to the fourth aspect of the present invention, the secondary battery according to any one of the first to third aspects of the present invention, and the first rib is provided on an intermediate member having a second rib that is pressed against the case to form a ventilation path.

[0011] In the secondary battery according to the fifth aspect of the present invention, the secondary battery according to any one of the first to fourth aspects of the present invention, and the first rib is intermittently provided in a direction orthogonal to the winding axis direction.

[0012] In the secondary battery according to the sixth aspect of the present invention, the secondary battery according to the fourth aspect of the present invention, and the height of the second rib is formed lower than the height of the highest portion of the first rib.

Advantages of the Invention

[0013] In the secondary battery according to the first aspect of the present invention, by having a tapered surface inclined so that the pressing surface corresponds to the inclined portion and providing a first rib that is pressed against the inclined portion via the case, the movement of the electrolytic solution in the winding axis direction is suppressed. Therefore, the electrolytic solution is suppressed from being pushed out in the winding axis direction. As a result, the unevenness of the salt concentration of the electrolytic solution is suppressed, and the high-rate deterioration of the secondary battery can be suppressed.

[0014] In the secondary battery according to the second aspect of the present invention, at a portion corresponding to the inclined portion of the exterior film, a folded portion where the exterior film is folded is formed, so that the thickness of the folded portion is increased compared to other portions. Therefore, the folded portion applies a pressing force to the inclined portion. As a result, the extrusion of the electrolytic solution in the winding axis direction is further suppressed.

[0015] In the secondary battery according to the third aspect of the present invention, the width of the tapered surface is formed wider than the width of the folded portion, so that the tapered surface is pressed against the entire width of the folded portion. Therefore, an appropriate pressing force is applied to the inclined portion by the folded portion. As a result, the extrusion of the electrolytic solution in the winding axis direction is appropriately suppressed.

[0016] In the secondary battery according to the fourth aspect of the present invention, the first rib is provided on an intermediate member having a second rib that is pressed against the case to form a ventilation path. Thus, the intermediate member suppresses the extrusion of the electrolytic solution in the winding axis direction and can form a ventilation path.

[0017] In the secondary battery according to the fifth aspect of the present invention, the first ribs are intermittently provided in a direction orthogonal to the winding axis direction, so that gaps are formed between the first ribs. Therefore, the gaps between the first ribs can form a ventilation path that is discharged in the winding axis direction.

[0018] In the secondary battery according to the sixth aspect of the present invention, the height of the second rib is formed lower than the height of the highest portion of the first rib, so that the second rib is pressed against the power generation portion via the case, and the first rib is pressed against the inclined portion via the case. Therefore, while the second rib forms a ventilation path, the first rib can appropriately suppress the extrusion of the electrolytic solution in the winding axis direction.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0020] 〔First Embodiment〕 Hereinafter, a secondary battery according to the first embodiment will be described with reference to the drawings. The secondary battery according to the first embodiment is, for example, a lithium-ion secondary battery used as an in-vehicle power source for an electric vehicle, a hybrid vehicle, or the like. In each figure, the arrow UP indicates the upper side in the vertical direction of the secondary battery, the arrow FR indicates the front side in the front-rear direction of the secondary battery, and the arrow LH indicates the left side in the left-right direction of the secondary battery. Also, the arrow D indicates the winding axis direction of the winding body 30, and the arrow T indicates the thickness direction of the winding body 30.

[0021] [Configuration of Battery Stack 1] As shown in FIGS. 1 and 2, the battery stack 1 as a secondary battery includes a battery cell 10 and an intermediate member 70 interposed between the wide surfaces of the battery cell 10. In the battery stack 1, the battery cell 10 and the intermediate member 70 are alternately arranged in the front-rear direction.

[0022] The intermediate member 70 includes a spacer 71 disposed between the battery cells 10 in the front-rear direction, and end plates 72 disposed at both ends of the battery stack 1 in the front-rear direction.

[0023] The end plates 72 are disposed so as to sandwich the battery cells 10 and the spacer 71. And, for example, a restraining band (not shown) that restrains between the end plates 72 applies a restraining pressure that compresses in the front-rear direction to the battery stack 1.

[0024] [Configuration of Battery Cell 10] As shown in FIG. 3, the battery cell 10 includes a lid assembly 20, a wound body (an example of an electrode body) 30, an exterior film 60, and a case 12.

[0025] (Lid Assembly 20) The lid assembly 20 includes a lid member 21, a negative electrode external terminal 22 and a positive electrode external terminal 23 provided above the lid member 21, and a negative electrode current collecting terminal 24 and a positive electrode current collecting terminal 25 provided below the lid member 21.

[0026] (Wound Body 30) As shown in FIGS. 4 and 5, the wound body 30 is wound in a state where a negative electrode sheet 40, a positive electrode sheet 50, and two separators 45 are laminated, and is formed in a flat shape.

[0027] The negative electrode sheet 40 has a negative electrode active material layer 42 formed by coating both surfaces of a long strip-shaped negative electrode body 41 with a negative electrode active material. At the other end of the negative electrode sheet 40 in the winding axis direction, the negative electrode active material layer 42 is not formed, and the negative electrode body 41 is exposed.

[0028] The positive electrode sheet 50 has a positive electrode active material layer 52 formed by coating both surfaces of a long strip-shaped positive electrode body 51 with a positive electrode active material. At one end of the positive electrode sheet 50 in the winding axis direction, the positive electrode active material layer 52 is not formed, and the positive electrode body 51 is exposed.

[0029] The separator 45 is formed of an insulating material such as polypropylene or polyethylene. The separator 45 is disposed between the positive electrode sheet 50 and the negative electrode sheet 40 and insulates the positive electrode sheet 50 and the negative electrode sheet 40.

[0030] The wound body 30 configured as described above has, as shown in FIG. 4, a power generation part 31, a negative electrode current collecting part 32 as a current collecting part, and a positive electrode current collecting part 33 as a current collecting part.

[0031] The power generation part 31 is formed by laminating a region of the positive electrode sheet 50 where a positive electrode active material is coated to form a positive electrode active material layer 52, a region of the negative electrode sheet 40 where a negative electrode active material is coated to form a negative electrode active material layer 42, and the separator 45. The power generation part 31 has a function of storing the electrical energy of the battery cell 10.

[0032] As shown in FIG. 6, the negative electrode current collecting part 32 is crushed and current collected in a state where the negative electrode electrode body 41 overlaps. The positive electrode current collecting part 33 is crushed and current collected in a state where the positive electrode electrode body 51 overlaps. A negative electrode current collecting terminal 24 is connected to the negative electrode current collecting part 32, and a positive electrode current collecting terminal 25 is connected to the positive electrode current collecting part 33.

[0033] As shown in FIGS. 3 and 6, by current collecting the negative electrode current collecting part 32 and the positive electrode current collecting part 33, an inclined part 35 is formed on the outer peripheral surface of the wound body 30.

[0034] The inclined part 35 is inclined and formed inward in the thickness direction of the wound body 30 in a top view. The inclined part 35 is inclined inward in the thickness direction of the wound body 30 from the power generation part 31 and connected to the negative electrode current collecting part 32 or the positive electrode current collecting part 33.

[0035] (Outer packaging film 60) As shown in FIG. 1, the exterior film 60 is formed of an insulating material, ensuring insulation between the wound body 30 and the case 12. The exterior film 60 is formed in a bag shape with an open top. The exterior film 60 is formed in a bag shape so as to cover the outer surfaces of the wound body 30 other than the upper surface. The exterior film 60 further covers a part of the negative electrode current collector terminal 24 and the positive electrode current collector terminal 25.

[0036] As shown in FIG. 6, a folded portion 62 is formed in a portion of the exterior film 60 corresponding to the inclined portion 35. The folded portion 62 may be formed on the outer edge connected to the power generation portion 31 of the inclined portion 35. The folded portion 62 is formed by folding a part of the exterior film 60, and its thickness is increased compared to other parts. Note that the folded portion 62 may be provided in a portion corresponding to the inclined portion 35 on the front surface and the rear surface of the wound body 30.

[0037] (Case 12) As shown in FIG. 1, the case 12 is made of, for example, aluminum, and is formed in a rectangular box shape that is long in the left - right direction with an open top.

[0038] Inside the case 12, the wound body 30 to which the negative electrode current collector terminal 24 and the positive electrode current collector terminal 25 are joined is accommodated in a state covered with the exterior film 60, and the lid member 21 is attached, for example, by laser welding, so as to close the opening of the case 12. And the electrolytic solution is injected into the case 12 from the injection port 21A provided in the lid member 21.

[0039] In the battery cell 10 configured as described above, the output of the wound body 30 is taken out from the negative electrode external terminal 22 and the positive electrode external terminal 23, and it is used as a power source for an electric vehicle, a hybrid vehicle, or the like.

[0040] [Configuration of the spacer 71] As shown in FIG. 6, the spacer 71 is formed in a rectangular plate shape with the front - rear direction as the plate - thickness direction. The spacer 71 includes a first rib 73 and a second rib 74.

[0041] The first rib 73 is formed to protrude rearward from the wide surface of the spacer 71. The first rib 73 is provided so as to extend from the upper end to the lower end of the spacer 71 at a position corresponding to the inclined portion 35. The first rib 73 is provided at a position corresponding to the overlapping portion 62.

[0042] The first rib 73 has a tapered surface 73A that is inclined via the case 12 such that the pressing surface pressed against the inclined portion 35 corresponds to the inclined portion 35. The tapered surface 73A is inclined so as to follow the inclination of the inclined portion 35. The tapered surface 73A may be inclined so as to follow the steepest inclination angle of the inclined portion 35.

[0043] The second rib 74 is formed to protrude rearward from the wide surface of the spacer 71. The second rib 74 is provided at a position corresponding to the power generation portion 31. In the winding axis direction, a plurality (four in the first embodiment) of the second ribs 74 are provided between the two first ribs 73. The second rib 74 has a flat surface 74A with a flat pressing surface that is pressed against the power generation portion 31 via the case 12.

[0044] The second rib 74 is pressed against the position corresponding to the power generation portion 31 of the case 12 to form the ventilation path 75 and restrain the battery cell 10. The height of the second rib 74 is formed lower than the height of the highest portion of the first rib 74. The height of the second rib 74 can also be the lowest height of the tapered surface 73A of the first rib 73. The width W1 of the tapered surface 73A is formed wider than the width W2 of the overlapping portion 62.

[0045] [Operation of Battery Stack] The restraint of the battery cell 10 by the spacer 71 is performed after the activation of the battery cell 10. As shown in FIG. 7, when the battery cell 10 is restrained in the front-rear direction by the spacer 71, the tapered surface 73A of the first rib 73 presses the folded portion 62 through the case 12. The pressed folded portion 62 presses the inclined portion 35. Here, since the folded portion 62 is folded and its thickness is increased compared to other portions, the pressing force by which the folded portion 62 presses the inclined portion 35 is increased. Therefore, the movement of the electrolytic solution passing from the power generation portion 31 through the inclined portion 35 is suppressed.

[0046] Also, when the battery cell 10 is restrained in the front-rear direction by the spacer 71, the flat surface 74A of the second rib 74 presses the power generation portion 31 through the case 12. Further, an air passage 75 is formed by the second rib 74 that presses the power generation portion 31.

[0047] [Operation] By the way, during high-rate charge and discharge when a large current flows, the negative electrode sheet 40 expands and contracts. When the negative electrode sheet 40 expands, the electrolytic solution flows out from both ends in the winding axis direction to the outside of the wound body 30. When the electrolytic solution flows out to the outside of the wound body 30, unevenness occurs in the salt concentration of the electrolytic solution, and there is a problem of high-rate deterioration in which the internal resistance due to the deviation of the salt concentration increases.

[0048] The battery stack 1 of the first embodiment includes a positive electrode sheet 50, a negative electrode sheet 40, a separator 45 disposed between the positive electrode sheet 50 and the negative electrode sheet 40, a wound body 30 that is wound and has an inclined portion 35 that is inclined inward in the thickness direction of the power generation portion 31 and is connected to a current collector portion, a case 12 in which the wound body 30 is accommodated together with the electrolytic solution, and a first rib 73 having a tapered surface 73A that is inclined so that a pressing surface pressed against the inclined portion 35 corresponds to the inclined portion 35 through the case 12 (see FIG. 7).

[0049] The pressing surface has a tapered surface 73A inclined so as to correspond to the inclined portion 35, and includes a first rib 73 pressed against the inclined portion 35 via the case 12, thereby suppressing the movement of the electrolytic solution in the winding axis direction. Therefore, the electrolytic solution is suppressed from being pushed out in the winding axis direction. As a result, the unevenness in the salt concentration of the electrolytic solution is suppressed from occurring, and the high-rate deterioration of the secondary battery can be suppressed.

[0050] In the battery stack 1 of the first embodiment, an exterior film 60 covering the wound body 30 is provided, and a folded portion 62 where the exterior film 60 is folded is formed in a portion corresponding to the inclined portion 35 of the exterior film 60 (see FIG. 7).

[0051] Since a folded portion 62 where the exterior film 60 is folded is formed in a portion corresponding to the inclined portion 35 of the exterior film 60, the thickness of the folded portion 62 is made thicker than other portions. Therefore, the folded portion 62 applies a pressing force to the inclined portion 35. As a result, the electrolytic solution is further suppressed from being pushed out in the winding axis direction.

[0052] In the battery stack 1 of the first embodiment, the width of the tapered surface 73A is formed wider than the width of the folded portion 62 (see FIG. 7).

[0053] Since the width of the tapered surface 73A is formed wider than the width of the folded portion 62, the tapered surface 73A is pressed against the entire width of the folded portion 62. Therefore, the folded portion 62 appropriately applies a pressing force to the inclined portion 35. As a result, the electrolytic solution is appropriately suppressed from being pushed out in the winding axis direction.

[0054] In the battery stack 1 of the first embodiment, the first rib 73 is provided on an intermediate member 70 having a second rib 74 that is pressed against the case 12 to form a ventilation path 75 (see FIG. 7).

[0055] The first rib 73 is provided on an intermediate member 70 having a second rib 74 that presses against the case 12 to form a ventilation passage 75. Thus, the intermediate member 70 can suppress the electrolyte from being extruded in the winding axis direction and can form the ventilation passage 75.

[0056] In the battery stack 1 of the first embodiment, the height of the second rib 74 is formed lower than the height of the highest portion of the first rib 73 (see FIG. 7).

[0057] Since the height of the second rib 74 is formed lower than the height of the highest portion of the first rib 73, the second rib 74 presses against the power generation unit 31 via the case 12, and the first rib 73 presses against the inclined portion 35 via the case 12. Therefore, while the second rib 74 forms the ventilation passage 75, the first rib 73 can appropriately suppress the electrolyte from being extruded in the winding axis direction.

[0058] 〔Second Embodiment〕 The secondary battery of the second embodiment differs from the secondary battery of the first embodiment in that the configuration of the first rib is different. Note that, for the description of the same or equivalent parts as those described in the first embodiment, the same terms or the same reference numerals are used for the description.

[0059] As shown in FIG. 8, the first rib 173 is intermittently provided in a direction orthogonal to the winding axis direction. Note that the spacer 71 may not include a second rib. Further, the second rib may be provided to extend in the winding axis direction so as to be ventilated to the outside in the winding axis direction, or may be provided to extend upward from the lower end of the spacer 71 and then extend in the winding axis direction so as to be ventilated to the outside in the winding axis direction from below. In this case, the second rib can be provided so as to be ventilated from between the intermittently provided first ribs 173.

[0060] The first rib 173 is intermittently provided in the orthogonal direction orthogonal to the winding axis direction, so that a gap is formed between the first ribs 173. Therefore, the gap between the first ribs 173 can form the ventilation passage 75 discharged in the winding axis direction. As a result, the ventilation passage 75 can be formed while suppressing the electrolytic solution from being pushed out in the winding axis direction.

[0061] Regarding other configurations and effects, since they are substantially the same as those in the first embodiment, the description thereof will be omitted.

[0062] As described above, the secondary battery of the present invention has been described based on the first embodiment and the second embodiment. However, the specific configuration is not limited to these embodiments, and design changes and the like are allowed as long as the gist of the invention according to each claim of the claims is not deviated from.

[0063] In the first embodiment and the second embodiment, an example is shown in which the first rib is provided on the rear side of the spacer 71 to restrain the front side of the wound body 30. However, the first rib may also be provided on the front side of the spacer 71 to restrain the front side and the rear side of the wound body 30.

[0064] In the first embodiment and the second embodiment, an example is shown in which the overlapping portion 62 is formed in a portion corresponding to the inclined portion 35 on the front side of the wound body 30. However, the overlapping portion may also be formed in a portion corresponding to the inclined portion 35 on the rear side of the wound body.

[0065] In the first embodiment and the second embodiment, an example is shown in which the spacer 71 includes the second rib. However, the spacer may not include the second rib.

[0066] In the first embodiment, an example is shown in which the first rib 73 is provided so as to extend from the upper end to the lower end of the spacer 71 at a position corresponding to the inclined portion 35. However, the first rib may be partially provided at a position corresponding to the inclined portion 35.

[0067] In the first and second embodiments, an example in which the secondary battery is a battery stack has been shown. However, the secondary battery may be composed of one battery cell and a spacer that restrains the battery cell.

[0068] In the first and second embodiments, an example in which the secondary battery is a lithium-ion secondary battery has been shown. However, the secondary battery can be other batteries.

Explanation of Reference Signs

[0069] 1 Battery stack (an example of a secondary battery) 12 Case 31 Power generation part 35 Inclined part 40 Negative electrode sheet 50 Positive electrode sheet 60 Exterior film 70 Intermediate member 73A Tapered surface 73 First rib 74 Second rib 75 Ventilation path

Claims

1. A wound body comprising a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet, which are wound to form a flat power generation unit, and having an inclined portion that is inclined inward in the thickness direction of the power generation unit and connected to a current collection unit; A case in which the wound body is accommodated together with an electrolytic solution; A first rib having a tapered surface that is inclined so that a pressing surface pressed against the inclined portion corresponds to the inclined portion via the case; A secondary battery comprising the above.

2. An exterior film covering the wound body, and A folded portion where the exterior film is folded is formed at a portion corresponding to the inclined portion of the exterior film. The secondary battery according to Claim 1.

3. The width of the tapered surface is formed wider than the width of the folded portion. The secondary battery according to Claim 2.

4. The first rib is provided on an intermediate member having a second rib that is pressed against the case to form a ventilation path. The secondary battery according to Claim 1.

5. The first rib is intermittently provided in a direction orthogonal to the winding axis direction. The secondary battery according to Claim 1.

6. The height of the second rib is formed lower than the height of the highest portion of the first rib. The secondary battery according to Claim 4.

Images