Secondary battery and method for manufacturing the same

Abstract

To restrain damage to a separator and restrain short-circuit between electrodes.SOLUTION: A secondary battery 10 includes a wound body 30 including a positive electrode sheet 50 that has a positive electrode coated region W2 in which a positive electrode current collector 51 is coated with a positive electrode active material layer 52, and a positive electrode uncoated region M2 formed at one end of the positive electrode current collector 51 in an electrode body width direction D and uncoated with the positive electrode active material layer 52, a negative electrode sheet 40 having a negative electrode coated region W1 in which a negative electrode current collector 41 is coated with a negative electrode active material layer 42 in the electrode body width direction D in a region wider than the positive electrode coated region W2, and a negative electrode uncoated region M1 formed at the other end of the negative electrode current collector 41 in the electrode body width direction D and uncoated with the positive electrode active material layer 42, and a separator 45 that is formed so as to protrude from the negative electrode active material layer 42 to one side in the electrode body width direction D, has a high density region 45B having a higher density than the end portion in the electrode body width direction D, has a positive electrode current collector 51 collected thereon, and is bent at one side of the high density region 45B in the electrode body width direction D.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a secondary battery and a method for manufacturing the secondary battery.

Background Art

[0002] In a secondary battery, it is known to bundle wound or laminated electrodes for each polarity and collect the current collectors.

[0003] Patent Document 1 discloses a technique in which a negative electrode active material is applied to the surface of a negative electrode sheet in a thickness and range such that a curved surface formed by a separator bent in a state where a positive electrode tab portion is bundled does not contact the negative electrode sheet of a non-tab end coating portion.

[0004] By the way, in a secondary battery, it is preferable to suppress breakage of the separator and suppress short-circuiting between electrodes.

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 suppress breakage of the separator and suppress short-circuiting between electrodes.

Means for Solving the Problems

[0007] The secondary battery according to the first aspect of the present invention includes a positive electrode sheet having a positive electrode coating region where a positive electrode active material layer is coated on a positive electrode current collector, and a positive electrode uncoated region formed at one end in the electrode body width direction of the positive electrode current collector and where the positive electrode active material layer is not coated; a negative electrode sheet having a negative electrode coating region where a negative electrode active material layer is coated on a negative electrode current collector wider than the positive electrode coating region in the electrode body width direction, and a negative electrode uncoated region formed at the other end in the electrode body width direction of the negative electrode current collector and where the negative electrode active material layer is not coated; and a separator disposed between the positive electrode sheet and the negative electrode sheet and protruding outward in the electrode body width direction from the negative electrode coating region, the separator having a high-density region formed to protrude from the negative electrode active material layer toward one side in the electrode body width direction and having a higher density than the end in the electrode body width direction, and the positive electrode current collector being a current collector foil bent on one side in the electrode body width direction of the high-density region.

[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, the high-density region is formed at least on the outer side in the thickness direction of the electrode body.

[0009] The secondary battery according to the third aspect of the present invention is the secondary battery according to the first aspect or the second aspect of the present invention, and the high-density region is formed with a higher density on the outer side in the thickness direction of the electrode body than on the inner side in the thickness direction of the electrode body.

[0010] The manufacturing method of the secondary battery according to the fourth aspect of the present invention includes a positive electrode coated region where a positive electrode active material layer is coated on a positive electrode current collector, and a positive electrode uncoated region formed at one end of the positive electrode current collector in the electrode body width direction, where the positive electrode active material layer is not coated, a positive electrode sheet having the same, a negative electrode coated region where a negative electrode active material layer is coated on a negative electrode current collector wider than the positive electrode coated region in the electrode body width direction, and a negative electrode uncoated region formed at the other end of the negative electrode current collector in the electrode body width direction, where the negative electrode active material layer is not coated, a negative electrode sheet having the same, and a separator disposed between the positive electrode sheet and the negative electrode sheet and protruding outward in the electrode body width direction from the negative electrode coated region, an electrode body forming step of forming an electrode body in which the same are laminated or wound, a high-density region forming step of applying heat from the outside in the thickness direction of the electrode body to a region of the separator on one side in the electrode body width direction from the negative electrode active material layer to form a high-density region having a higher density than the end in the electrode body width direction of the separator, and a current collecting step of current collecting the positive electrode current collector in which the high-density region is formed.

Effect of the Invention

[0011] In the secondary battery according to the first aspect of the present invention, a high-density region is formed so as to protrude from the negative electrode active material layer to one side in the electrode body width direction and having a higher density than the end in the electrode body width direction. By providing the same, the positive electrode current collector is current collected, the positive electrode current collector is bent in the positive electrode uncoated region, and when the separator is pushed by the bent positive electrode current collector, the separator is bent starting from the outside in the electrode body width direction of the high-density region. Therefore, the separator is bent outside the electrode body width direction of the negative electrode active material region and is not pressed against the edge formed at the end in the electrode body width direction of the negative electrode active material layer. As a result, breakage of the separator can be suppressed, and short circuit between electrodes can be suppressed.

[0012] In the secondary battery according to the second aspect of the present invention, since the high-density region is formed at least outside in the thickness direction of the electrode body, the high-density region is formed in a portion where breakage of the separator tends to occur during current collection of the positive electrode current collector. Therefore, breakage of the separator can be suppressed, and short circuit between electrodes can be suppressed.

[0013] In the secondary battery according to the third aspect of the present invention, in the high-density region, the density is higher on the outer side in the thickness direction of the electrode body than on the inner side in the thickness direction of the electrode body, so that the density of the portion where the separator is likely to be damaged during the lamination of the positive electrode current collector foil is increased. Therefore, it is possible to suppress the breakage of the separator and suppress the short circuit between the electrodes.

[0014] In the method for manufacturing a secondary battery according to the fourth aspect of the present invention, by laminating the positive electrode current collector in which the high-density region is formed, the positive electrode current collector is laminated, and the positive electrode current collector is bent in the uncoated region of the positive electrode. When the separator is pushed by the bent positive electrode current collector, the separator is bent starting from the outer side in the width direction of the electrode body in the high-density region. Therefore, the separator is bent on the outer side in the width direction of the electrode body in the negative electrode active material region and is not pressed against the edge formed at the end in the width direction of the electrode body of the negative electrode active material layer. As a result, it is possible to suppress the breakage of the separator and suppress the short circuit between the electrodes.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

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Figure 4

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Figure 9

Embodiments for Carrying Out the Invention

[0016] Hereinafter, the secondary battery according to the embodiment will be described with reference to the drawings. An example in which the secondary battery according to the embodiment is a lithium ion secondary battery will be described. In each figure, the arrow UP indicates the upper side in the vertical direction of the secondary battery 10, the arrow FR indicates the front side in the front-rear direction of the secondary battery 10, the arrow LH indicates the left side in the left-right direction of the secondary battery 10, and the arrow D indicates the electrode body width direction.

[0017] [Configuration of Secondary Battery 10] As shown in FIG. 1, the secondary battery 10 includes a lid assembly 20, a wound body (an example of an electrode body) 30, and a battery case 12.

[0018] [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 on the upper side of the lid member 21, and a negative electrode current collecting terminal 24 and a positive electrode current collecting terminal 25 provided on the lower side of the lid member 21.

[0019] [Wound Body 30] As shown in FIG. 2, the wound body 30 is formed in a flat shape by winding a negative electrode sheet 40, a positive electrode sheet 50, and two separators 45 in a stacked state.

[0020] [Negative Electrode Sheet 40] The negative electrode sheet 40 has a negative electrode coating region W1 and a negative electrode non-coating region M1.

[0021] In the negative electrode coating region W1, a negative electrode active material is coated on both surfaces of a long strip-shaped negative electrode current collector 41 to form a negative electrode active material layer 42. The negative electrode coating region W1 is coated wider than a positive electrode coating region W2, which will be described later, in the electrode body width direction D. In the negative electrode uncoated region M1, the negative electrode active material is not coated and the negative electrode current collector 41 is exposed. The negative electrode uncoated region M1 is formed so as to protrude to the other side in the electrode body width direction D of the negative electrode coating region W1. In other words, the negative electrode uncoated region M1 is formed at the other end of the negative electrode current collector 41 in the electrode body width direction.

[0022] 〈Positive Electrode Sheet 50〉 The positive electrode sheet 50 has a positive electrode coating region W2 and a positive electrode uncoated region M2.

[0023] In the positive electrode coating region W2, a positive electrode active material is coated on both surfaces of a long strip-shaped positive electrode current collector 51 to form a positive electrode active material layer 52. The positive electrode coating region W2 is coated narrower than the negative electrode coating region W1 in the electrode body width direction D. In the positive electrode uncoated region M2, the positive electrode active material is not coated and the positive electrode current collector 51 is exposed. The positive electrode uncoated region M2 is formed so as to protrude to one side in the electrode body width direction D of the positive electrode coating region W2. In other words, the positive electrode uncoated region M2 is formed at one end of the positive electrode current collector 51 in the electrode body width direction.

[0024] As shown in FIGS. 2 and 3, the negative electrode sheet 40 in the negative electrode coating region W1, the positive electrode sheet 50 in the positive electrode coating region W2, and the separator 45 overlap to form a power generation unit 31. The negative electrode current collector 41 in the negative electrode uncoated region M1 is crushed and foil-collected in a state of overlapping to form a negative electrode current collecting portion 32. The positive electrode current collector 51 in the positive electrode uncoated region M2 is crushed and foil-collected in a state of overlapping to form a positive electrode current collecting portion 33.

[0025] As shown in FIG. 3, a negative electrode current collecting terminal 24 is connected to the negative electrode current collecting portion 32, and a positive electrode current collecting terminal 25 is connected to the positive electrode current collecting portion 33.

[0026] 〈Separator 45〉 The separator 45 is formed of a material whose density increases when heated, and is formed of a foamed material such as polypropylene or polyethylene, for example. 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. The separator 45 is provided so as to protrude outward in the electrode body width direction D from the negative electrode coating region W1 in a front view of looking at the front surface of the wound body 30 from the front.

[0027] As shown in FIG. 4, the separator 45 includes a high-density region 45B on one side in the electrode body width direction D. The high-density region 45B is a region having a higher density than the general portion 45A of the separator 45. The high-density region 45B is formed when the separator 45 is cooled after being heated.

[0028] In a front view, the high-density region 45B is formed so as to protrude from the negative electrode active material layer 42 to one side in the electrode body width direction D. In a front view, the high-density region 45B is formed so as to cover an edge 42A formed on one side in the electrode body width direction D of the negative electrode active material layer 42. The general portion 45A is a portion other than the high-density region 45B of the separator 45, and includes, for example, one end of the separator 45 in the electrode body width direction D, which is on one side in the electrode body width direction D rather than the high-density region 45B.

[0029] The high-density region 45B is formed at least outside in the thickness direction T of the wound body 30. The high-density region 45B is formed to have a higher density outside in the thickness direction T of the wound body 30 than inside in the thickness direction T of the wound body 30.

[0030] The separator 45 includes a bent portion 45C. The bent portion 45C is pressed by the positive electrode current collector 51 when the positive electrode current collector 51 is collected, and is bent on one side in the electrode body width direction D of the high-density region 45B.

[0031] (Battery case 12) As shown in FIG. 1, the battery 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 upper surface.

[0032] Inside the battery case 12, a wound body 30 to which a negative electrode current collector terminal 24 and a positive electrode current collector terminal 25 are joined is accommodated, and a lid member 21 is attached so as to close the opening of the battery case 12 by, for example, laser welding. Then, an electrolytic solution is injected into the battery case 12 from an injection port provided in the lid member 21.

[0033] In the secondary battery 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.

[0034] [Method for manufacturing the secondary battery 10] The secondary battery 10 is manufactured through an electrode body forming step, a high-density region forming step, and a current collector foil step.

[0035] (Electrode body forming step) In the electrode body forming step, as shown in FIGS. 5 and 6, the wound body 30 is formed by laminating and winding a positive electrode sheet 50, a negative electrode sheet 40, and a separator 45.

[0036] (High-density region forming step) In the high-density region forming step, as shown in FIGS. 7 and 8, a heating member 60 heated to a predetermined temperature is pressed against the outer peripheral surface of the wound body 30 from the outside in the thickness direction T of the wound body 30, targeting a position where the inner end portion of the heating member 60 in the electrode body width direction D becomes the outer end portion of the negative electrode active material layer 42 in the electrode body width direction D, thereby applying heat to the separator 45. In other words, the heating member 60 is pressed against the outer peripheral surface of the wound body 30 from the outside in the thickness direction T of the wound body 30 in the region of the separator 45 on one side of the negative electrode active material layer 42 in the electrode body width direction D, thereby applying heat to the separator 45. As a result, the separator 45 against which the heating member 60 is pressed and the separator 45 in the vicinity thereof are heated. Then, by stopping the heating of the heating member 60, the separator 45 is cooled. As a result, the heated portion of the separator 45 contracts, and a high-density region 45B is formed so as to protrude from the negative electrode active material layer 42 toward one side in the electrode body width direction D.

[0037] [Current Collector Laminating Process] In the current collector laminating process, as shown in FIG. 9, the overlap of the positive current collector 51 in the uncoated positive electrode region M2 is sandwiched and crushed between a base (e.g., an anvil) 61 and the positive current collector terminal 25 for current collection lamination, and, for example, ultrasonic welding is performed by a horn 62, whereby the positive current collecting portion 33 is joined to the positive current collector terminal 25. At this time, as shown in FIG. 4, the separator 45 is pressed by the laminated positive current collector 51 and bends on one side in the electrode body width direction D of the high-density region 45B. Note that the positive current collector 51 may be laminated in a state where the heating member 60 whose heating has been stopped is pressed against the separator 45.

[0038] Also, the overlap of the negative current collector 41 in the uncoated negative electrode region M1 is sandwiched and crushed between the base 61 and the negative current collector terminal 24 for current collection lamination, and, for example, ultrasonic welding is performed by a horn 62, whereby the negative current collecting portion 32 is joined to the negative current collector terminal 24.

[0039] Then, the wound body 30 to which the negative current collector terminal 24 and the positive current collector terminal 25 are joined is accommodated inside the battery case 12, and the lid member 21 is attached, for example, by laser welding, so as to close the opening of the battery case 12. Then, the electrolytic solution is injected into the battery case 12 from the injection port provided in the lid member 21.

[0040] [Operation] Incidentally, when the positive current collector 51 is laminated, the positive current collector 51 is bent in the uncoated positive electrode region M2. Then, the separator 45 is bent by being pressed by the bent positive current collector 51. At this time, there is a problem that the separator 45 is damaged by being pressed against the edge 42A formed at the end in the electrode body width direction D of the negative electrode active material layer 42, resulting in a short circuit between the electrodes.

[0041] The secondary battery 10 of the embodiment includes a positive electrode sheet 50 having a positive electrode coating region W2 where a positive electrode active material layer 52 is coated on a positive electrode current collector 51, and a positive electrode uncoated region M2 formed at one end of the positive electrode current collector 51 in the electrode body width direction D where the positive electrode active material layer 52 is not coated; a negative electrode sheet 40 having a negative electrode coating region W1 where a negative electrode active material layer 42 is coated wider than the positive electrode coating region W2 in the electrode body width direction D on a negative electrode current collector 41, and a negative electrode uncoated region M1 formed at the other end of the negative electrode current collector 41 in the electrode body width direction D where the negative electrode active material layer 42 is not coated; and a separator 45 disposed between the positive electrode sheet 50 and the negative electrode sheet 40 and protruding outward from the negative electrode coating region W1 in the electrode body width direction D. The separator 45 is formed so as to protrude from the negative electrode active material layer 42 to one side in the electrode body width direction D and includes a high-density region 45B having a higher density than the end in the electrode body width direction D. The positive electrode current collector 51 is collected into a foil and bent on one side in the electrode body width direction D of the high-density region 45B. The secondary battery 10 includes a wound body 30 having the separator 45 (see FIG. 2).

[0042] By providing the high-density region 45B that is formed so as to protrude from the negative electrode active material layer 42 to one side in the electrode body width direction D and has a higher density than the end in the electrode body width direction D, the positive electrode current collector 51 is collected into a foil, the positive electrode current collector 51 is bent in the positive electrode uncoated region M2, and when the separator 45 is pressed by the bent positive electrode current collector 51, the separator 45 is bent starting from the outside in the electrode body width direction D of the high-density region 45B. Therefore, the separator 45 is bent outside the negative electrode active material region in the electrode body width direction D and is not pressed against an edge 42A formed at the end of the negative electrode active material layer 42 in the electrode body width direction D. As a result, breakage of the separator 45 can be suppressed, and short circuit between electrodes can be suppressed.

[0043] By the way, when the positive electrode current collector 51 is collected into a foil, the bending angle of the separator 45 becomes tighter on the outside in the thickness direction than on the inside in the thickness direction of the wound body 30. Therefore, the separator 45 is more likely to be damaged on the outside in the thickness direction than on the inside in the thickness direction of the wound body 30.

[0044] In the secondary battery 10 of the embodiment, the high-density region 45B is formed at least on the outer side in the thickness direction of the wound body 30.

[0045] Since the high-density region 45B is formed at least on the outer side in the thickness direction of the wound body 30, the high-density region 45B is formed in a portion where the separator 45 is likely to be damaged when the positive electrode current collector 51 is tabbed. Therefore, it is possible to suppress the breakage of the separator 45 and suppress a short circuit between the electrodes.

[0046] In the secondary battery 10 of the embodiment, the high-density region 45B is formed with a higher density on the outer side in the thickness direction of the wound body 30 than on the inner side in the thickness direction of the wound body 30.

[0047] Since the high-density region 45B is formed with a higher density on the outer side in the thickness direction of the wound body 30 than on the inner side in the thickness direction of the wound body 30, the density of a portion where the separator 45 is likely to be damaged when the positive electrode current collector 51 is tabbed is increased. Therefore, it is possible to suppress the breakage of the separator 45 and suppress a short circuit between the electrodes.

[0048] The manufacturing method of the secondary battery 10 according to the embodiment includes a positive electrode sheet 50 having a positive electrode coating region W2 where a positive electrode active material layer 52 is coated on a positive electrode current collector 51, and a positive electrode non - coating region M2 formed at one end of the positive electrode current collector 51 in the electrode body width direction D where the positive electrode active material layer 52 is not coated; a negative electrode sheet 40 having a negative electrode coating region W1 where a negative electrode active material layer 42 is coated on a negative electrode current collector 41 wider than the positive electrode coating region W2 in the electrode body width direction D, and a negative electrode non - coating region M1 formed at the other end of the negative electrode current collector 41 in the electrode body width direction D where the negative electrode active material layer 42 is not coated; and a separator 45 disposed between the positive electrode sheet 50 and the negative electrode sheet 40 and protruding outward from the negative electrode coating region W1 in the electrode body width direction D, and an electrode body forming step of forming a wound body 30 by winding them; a high - density region forming step of applying heat from the outside in the thickness direction of the wound body 30 to a region of the separator 45 on one side in the electrode body width direction D from the negative electrode active material layer 42 to form a high - density region 45B having a higher density than the end portion of the separator 45 in the electrode body width direction D; and a current collector collecting step of collecting the positive electrode current collector 51 on which the high - density region 45B is formed.

[0049] By collecting the positive electrode current collector 51 on which the high - density region 45B is formed, the positive electrode current collector 51 is collected, the positive electrode current collector 51 is bent in the positive electrode non - coating region M2, and when the separator 45 is pushed by the bent positive electrode current collector 51, the separator 45 is bent starting from the outside in the electrode body width direction D of the high - density region 45B. Therefore, the separator 45 is bent outside the electrode body width direction D of the negative electrode active material region and is not pressed against the edge 42A formed at the end portion of the negative electrode active material layer 42 in the electrode body width direction D. As a result, breakage of the separator 45 can be suppressed, and short - circuit between electrodes can be suppressed.

[0050] As described above, the secondary battery and the manufacturing method of the secondary battery according to the present invention have been described based on the embodiment. However, the specific configuration is not limited to this embodiment, and design changes and the like are allowed as long as they do not deviate from the gist of the invention according to each claim of the claims.

[0051] In the embodiment, an example of a wound type in which the electrode body is wound in a state where the negative electrode sheet 40, the positive electrode sheet 50, and the separator 45 are laminated is shown. However, the electrode body may be of a laminated type in which the negative electrode sheet, the positive electrode sheet, and the separator are laminated.

[0052] In the embodiment, an example in which the secondary battery is a lithium-ion secondary battery is shown. However, the secondary battery can be other batteries.

Explanation of Reference Numerals

[0053] 10 Secondary battery 30 Wound body (an example of an electrode body) 41 Negative electrode current collector 42 Negative electrode active material layer 45 Separator 45B High-density region 50 Positive electrode sheet 51 Positive electrode current collector 52 Positive electrode active material layer D Electrode body width direction M1 Negative electrode uncoated region M2 Positive electrode uncoated region W1 Negative electrode coated region W2 Positive electrode coated region

Claims

1. A positive electrode sheet having a positive electrode coating region where a positive electrode active material layer is coated on a positive electrode current collector, and a positive electrode uncoated region formed at one end of the positive electrode current collector in the electrode body width direction, where the positive electrode active material layer is not coated; A negative electrode sheet having a negative electrode coating region where a negative electrode active material layer is coated wider than the positive electrode coating region in the electrode body width direction on a negative electrode current collector, and a negative electrode uncoated region formed at the other end of the negative electrode current collector in the electrode body width direction, where the negative electrode active material layer is not coated; A separator disposed between the positive electrode sheet and the negative electrode sheet, protruding outward in the electrode body width direction from the negative electrode coating region, A separator having a high-density region formed so as to protrude from the negative electrode active material layer to one side in the electrode body width direction and having a higher density than the end in the electrode body width direction; The positive electrode current collector is collected into a foil and bent on one side in the electrode body width direction of the high-density region; An electrode body comprising A secondary battery.

2. The high-density region is formed at least on the outer side in the thickness direction of the electrode body. The secondary battery according to Claim 1.

3. The high-density region is formed with a higher density on the outer side in the thickness direction of the electrode body than on the inner side in the thickness direction of the electrode body. The secondary battery according to Claim 1.

4. A positive electrode sheet having a positive electrode coating region where a positive electrode active material layer is coated on a positive electrode current collector, and a positive electrode uncoated region formed at one end of the positive electrode current collector in the electrode body width direction, where the positive electrode active material layer is not coated; A negative electrode sheet having a negative electrode coating region where a negative electrode active material layer is coated wider than the positive electrode coating region in the electrode body width direction on a negative electrode current collector, and a negative electrode uncoated region formed at the other end of the negative electrode current collector in the electrode body width direction, where the negative electrode active material layer is not coated; A separator disposed between the positive electrode sheet and the negative electrode sheet, protruding outward in the electrode body width direction from the negative electrode coating region; An electrode body forming step of forming an electrode body by laminating or winding; A high-density region forming step of applying heat from the outer side in the thickness direction of the electrode body to the region of the separator on one side in the electrode body width direction from the negative electrode active material layer to form a high-density region having a higher density than the end in the electrode body width direction of the separator; A foil collecting step of collecting the positive electrode current collector on which the high-density region is formed into a foil; A method for manufacturing a secondary battery including the above steps.

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