Cylindrical battery and method for manufacturing the same

Abstract

To improve the short circuit quality on a positive electrode plate.SOLUTION: A cylindrical battery (2) includes an electrode body (22) formed by winding laminated positive electrode plate (24), separator (28), and negative electrode plate (26), the positive electrode plate (24) includes a positive electrode substrate (4), a positive electrode active material (5) provided on the surface of the positive electrode substrate (4), a positive electrode lead (30) connected to the exposed portion (4ex) of the positive electrode substrate (4), and an insulating tape (6) that covers the exposed portion (4ex), and the side edges on both sides in the winding direction (X) of the insulating tape (6) have an angular difference (θ) with respect to the axial direction (Z) of the electrode body (22).SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a cylindrical battery with improved short-circuit quality and a method for manufacturing the same.

Background Art

[0002] As a typical cylindrical battery, a cylindrical alkaline storage battery is widely known. Among them, nickel-hydrogen batteries have been in increasing demand in recent years due to reasons such as large capacity and cleanness.

[0003] The above-mentioned cylindrical battery includes a bottomed cylindrical outer can with one end open. An electrode body is housed inside the outer can together with an alkaline electrolyte. The electrode body is formed by winding a positive electrode plate and a negative electrode plate spirally through a separator. To seal the outer can, a lid material is arranged at the open end of the outer can, and the part on the open end side of the outer can is caulked so as to restrain the outer peripheral part of the lid material.

[0004] Here, for example, Patent Document 1 discloses a secondary battery adopting the above-described configuration. In the secondary battery, a positive electrode active material is applied to both surfaces of a positive electrode substrate of the positive electrode plate, and one end of a positive electrode lead is welded and connected at an exposed part where the positive electrode substrate is partially exposed. Then, the exposed part is covered with an insulating tape together with the positive electrode lead to ensure insulation.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the conventional technology described above, the insulating tape provided on the surface of the positive electrode active material coated on the positive electrode substrate is rectangular in shape. Therefore, when the positive electrode plate is wound, a load is applied to the layer of positive electrode active material along the side edges on both sides of the insulating tape, which may cause exposure cracks that expose the positive electrode substrate and impair the insulating properties.

[0007] The present invention was made based on the above circumstances, and its objective is to provide a cylindrical battery with improved short-circuit quality and a method for manufacturing the same. [Means for solving the problem]

[0008] To achieve the above objective, the cylindrical battery of the present invention includes an electrode body formed by winding stacked positive electrode plates, a separator, and a negative electrode plate, wherein the positive electrode plate comprises a positive electrode substrate, a positive electrode active material provided on the surface of the positive electrode substrate, a positive electrode lead connected to the exposed portion of the positive electrode substrate, and an insulating tape covering the exposed portion, and the side edges of the insulating tape on both sides in the winding direction have an angular difference with respect to the axial direction of the electrode body.

[0009] Furthermore, in order to achieve the above objective, the present invention provides a method for manufacturing a cylindrical battery, which includes an electrode body formed by winding stacked positive electrode plates, a separator, and a negative electrode plate, and comprises an active material coating step of providing a positive electrode active material on the surface of a positive electrode substrate, a lead connection step of connecting a positive electrode lead to an exposed portion of the positive electrode substrate, and an insulation step of covering the exposed portion with insulating tape, wherein in the insulation step, an angular difference with respect to the axial direction of the electrode body is provided at the side edges on both sides of the insulating tape in the winding direction. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a cylindrical battery in which the short-circuit quality at the positive electrode plate is improved, and a method for manufacturing the same. [Brief explanation of the drawing]

[0011] [Figure 1]This is a perspective view showing a cylindrical battery according to one embodiment, partially cut open. [Figure 2] This is a diagram of the positive electrode plate. [Figure 3] This is a side view of the positive electrode plate. [Figure 4] This is a development diagram of a positive electrode plate with a second form of insulating tape. [Figure 5] This is a diagram of a positive electrode plate with conventional insulating tape. [Figure 6] This table shows the number of exposed cracks in cylindrical batteries using each type of insulating tape. [Modes for carrying out the invention]

[0012] A cylindrical battery 2 according to one embodiment will be described below with reference to the drawings.

[0013] The cylindrical battery 2 is, for example, an AA-size nickel-metal hydride storage battery. More specifically, as shown in Figure 1, the cylindrical battery 2 includes an outer casing 10 which is a bottomed cylindrical container with an open top. The outer casing 10 is conductive, and its bottom wall 35 functions as a negative electrode terminal. A sealing body 11 is fixed to the opening of the outer casing 10. This sealing body 11 includes a lid plate 14 and a positive electrode terminal 20, sealing the outer casing 10 and providing the positive electrode terminal 20. The lid plate 14 is a conductive disc-shaped member. Inside the opening of the outer casing 10, the lid plate 14 and a ring-shaped insulating packing 12 surrounding the lid plate 14 are arranged, and the insulating packing 12 is fixed to the opening edge 37 of the outer casing 10 by crimping the opening edge 37 of the outer casing 10. That is, the lid plate 14 and the insulating packing 12 cooperate with each other to airtightly close the opening of the outer casing 10.

[0014] Here, the cover plate 14 has a central through-hole 16 in the center, and a rubber valve body 18 is positioned on the outer surface of the cover plate 14 to close the central through-hole 16. Furthermore, a metal positive electrode terminal 20, which is cylindrical in shape with a flange, is electrically connected to the outer surface of the cover plate 14 so as to cover the valve body 18. This positive electrode terminal 20 presses the valve body 18 toward the cover plate 14. A gas vent hole (not shown) is opened in the positive electrode terminal 20.

[0015] Under normal conditions, the central through-hole 16 is airtightly closed by the valve body 18. However, if gas is generated inside the outer casing 10 and the internal pressure increases, the valve body 18 is compressed by the internal pressure, opening the central through-hole 16. As a result, gas is released from inside the outer casing 10 to the outside through the central through-hole 16 and the gas vent hole (not shown) of the positive electrode terminal 20. In other words, the central through-hole 16, the valve body 18, and the positive electrode terminal 20 form a safety valve for the battery.

[0016] The outer casing 10 houses the electrode body 22. This electrode body 22 includes a strip-shaped positive electrode plate 24, a negative electrode plate 26, and a separator 28. Specifically, the positive electrode plate 24 and the negative electrode plate 26 are wound in a spiral shape with the separator 28 sandwiched in between. That is, the positive electrode plate 24 and the negative electrode plate 26 are superimposed on each other via the separator 28. The outermost periphery of the electrode body 22 is formed by a part (outermost periphery) of the negative electrode plate 26 and is in contact with the inner circumferential wall of the outer casing 10. In other words, the negative electrode plate 26 and the outer casing 10 are electrically connected to each other.

[0017] Inside the outer can 10, the positive electrode lead 30 extending from the positive electrode plate 24 is connected to the lid plate 14. Specifically, one end of the positive electrode lead 30 is connected to the positive electrode substrate 4 (to be described later) of the positive electrode plate 24, and the other end is welded to the lid plate 14. Therefore, the positive electrode terminal 20 and the positive electrode plate 24 are electrically connected to each other via the positive electrode lead 30 and the lid plate 14. A circular upper insulating member 32 is disposed between the lid plate 14 and the electrode body 22, and the positive electrode lead 30 extends through a slit 39 provided in the upper insulating member 32. Also, a circular lower insulating member 34 is disposed between the electrode body 22 and the bottom of the outer can 10.

[0018] Furthermore, a predetermined amount of an alkaline electrolytic solution (not shown) is injected into the outer can 10. The alkaline electrolytic solution is impregnated in the electrode body 22 and is mainly held by the separator 28. This alkaline electrolytic solution causes an electrochemical reaction (charge-discharge reaction) during charge and discharge between the positive electrode plate 24 and the negative electrode plate 26. As this alkaline electrolytic solution, an aqueous solution containing at least one of KOH, NaOH, and LiOH as a solute is preferably used.

[0019] Hereinafter, in each figure, while showing the axial direction Z of the cylindrical battery 2, the winding direction X of the electrode body 22, and the stacking direction Y (radial direction) of the electrode body 22, the positive electrode plate 24 of the present embodiment will be described in more detail.

[0020] FIG. 2 is a developed view of the positive electrode plate 24. FIG. 3 is a side view of the positive electrode plate 24 and represents a cross section taken along the line i-i in FIG. 2. The positive electrode plate 24 can be manufactured as follows. First, a conductive positive electrode substrate 4 (see FIG. 3) having a porous structure is prepared. The positive electrode substrate 4 can be, for example, a sheet-like nickel foam, a sheet of a nickel porous body, or the like.

[0021] Then, the positive electrode active material 5 is provided on both surfaces of the positive electrode substrate 4 (active material coating step). At this time, the positive electrode substrate 4 holds the positive electrode active material 5 in the pores and is covered with layers made of the positive electrode active material 5 on both surfaces.

[0022] Here, the positive electrode substrate 4 has an exposed portion 4ex for connecting the positive electrode lead 30 near the center in the longitudinal direction, i.e., in the winding direction X of the positive electrode plate 24. The exposed portion 4ex is a region on the surface of the positive electrode substrate 4 where the positive electrode active material 5 is not present, and is provided in a rectangular shape on both sides of the positive electrode substrate 4. Then, one end of the strip-shaped positive electrode lead 30 is connected to one of the exposed portions 4ex on both sides by welding (lead connection process).

[0023] Furthermore, the positive electrode plate 24 is provided with insulating tape 6 covering the exposed portion 4ex on both sides: the side where the positive electrode lead 30 is welded (welded side surface) and the opposite side (unwelded side surface) (insulation process). On the welded side surface, the insulating tape 6, made of polypropylene for example, is applied over the welded positive electrode lead 30. The insulating tape 6 of the first embodiment 6A shown in Figure 2 has a shape enclosed by a line segment connecting points a and b, and a substantially parabolic curve from point a through point c to point b. The upper part of the insulating tape 6 (line segment a-b) is set to a length of, for example, 14 mm and is provided so as to protrude from the positive electrode base 4 in the axial direction Z. The insulating tape 6 has a width in the axial direction Z (shortest distance between line segment a-b and point c) of, for example, 16 mm, and a thickness in the lamination direction Y is set to 0.055 mm.

[0024] Here, the insulating tape 6 has side edges (curves ac and bc) on both sides in the winding direction X that have an angular difference θ with respect to the axial direction Z at all points. In particular, in the first embodiment 6A, since the side edges of the insulating tape 6 follow a shape that is approximately parabolic, this angular difference θ continuously expands inward from both sides in the winding direction X of the insulating tape 6, and becomes θ = 90° at the bottom of the insulating tape 6.

[0025] As a result, the insulating tape 6 does not have side edges on both sides in the winding direction X that are parallel to the axial direction Z of the electrode body 22, and does not apply concentrated load to the layer of positive electrode active material 5 provided on the surface of the positive electrode substrate 4 when the positive electrode plate 24 is wound. Therefore, when the positive electrode plate 24 is wound together with the negative electrode plate 26 and the separator 28, the risk of exposure cracks that expose the positive electrode substrate 4 occurring in the positive electrode active material 5 can be reduced.

[0026] Furthermore, in this embodiment, the positive electrode lead 30 is positioned to straddle only one end (upper end) of the positive electrode base 4 in the axial direction Z (short side direction of the positive electrode base 4) of the electrode body 22, and consequently, the exposed portion 4ex is formed to be shorter than the positive electrode base 4 in the axial direction Z. Therefore, the bottom (point c) of the insulating tape 6 does not reach the other end (lower end) in the axial direction Z, thereby increasing the angle difference θ between the side edge of the insulating tape 6 and the axial direction Z, and further reducing the risk of exposure cracks.

[0027] Figure 4 is an unfolded view of the positive electrode plate 24 having the insulating tape 6 of the second form 6B. The insulating tape 6 of the second form 6B has a different contour shape from the insulating tape 6 of the first form 6A described above, and more specifically, it is formed in a trapezoidal shape with straight side edges. That is, the side edges (line segments dg and ef) of the insulating tape 6 in the winding direction X are straight.

[0028] In this case, the angular difference θ between the side edge of the insulating tape 6 and the axial direction Z is preferably set in the range of 5 ≤ θ ≤ 25°, and here it is set to θ = 20.556°, for example. In addition, the insulating tape 6 of the second form 6B has an upper part (line segment d-e) of 14 mm, a lower part (line segment g-f) of 8 mm, and a width in the axial direction Z (shortest distance between line segments d-e and g-f) of 15 mm.

[0029] The positive electrode plate 24 having the insulating tape 6 of the second form 6B, when wound together with the negative electrode plate 26 and separator 28, similar to the first form 6A, can reduce the risk of exposure cracks occurring in the positive electrode active material 5 that expose the positive electrode substrate 4. In this case, the insulating tape 6 of the second form 6B covers a relatively smaller area of ​​the positive electrode active material 5 that contributes to charging and discharging compared to the first form 6A, thus suppressing a decrease in the discharge capacity of the cylindrical battery 2.

[0030] Figure 5 is an unfolded view of a positive electrode plate 24 having an insulating tape 6 of the conventional form 6C. The insulating tape 6 of the conventional form 6C differs in its contour shape from the insulating tape 6 of the first form 6A described above, and more specifically, it is formed in a rectangular shape with a width of 8 mm in the winding direction X and a width of 15 mm in the axial direction Z.

[0031] In a conventional positive electrode plate 24 having an insulating tape 6, the side edge of the insulating tape 6 in the winding direction X is parallel to the axial direction Z. As a result, when the positive electrode plate 24 is wound, exposed cracks CL are likely to occur in the layer of positive electrode active material 5 along these side edges, and there is a risk that the insulating properties will decrease as the positive electrode substrate 4 is exposed.

[0032] Next, the effects and benefits of the cylindrical battery 2 according to this disclosure will be explained through the verification results of the cylindrical battery 2 using each form of insulating tape 6. Figure 6 is a table showing the number of exposed cracks CL that occurred in the cylindrical battery 2 using each form of insulating tape 6.

[0033] In this verification, cylindrical batteries 2 for verification were fabricated with five different cell specifications as shown in Figure 6. For each cell specification of cylindrical battery 2, the insulating tape 6 used on the welded and unwelded surfaces of the positive electrode plate 24 was selected from combinations of the first form 6A, the second form 6B, and the conventional form 6C. The cylindrical battery 2 had a capacity design of 2600mAh, and 10,000 cells were fabricated for each cell specification.

[0034] Furthermore, charge-discharge tests were conducted at a rate of 0.1 / 0.2C on 10 cells of each of the fabricated cylindrical batteries 2 to measure their discharge capacity. In addition, CT inspections and disassembly inspections were performed on 100 cells of each of the cell specifications to confirm the number of short-circuit failures and exposed cracks.

[0035] As shown in Figure 6, in the comparative example where the positive electrode plate 24 had conventional insulating tape 6C on both sides, one cylindrical battery 2 developed a short-circuit failure, and exposed cracks were found in more than half of the 100 cells that underwent charge-discharge testing.

[0036] In contrast, in Examples 1 to 3, in which the insulating tape 6 of the second form 6B was used on at least one side of the positive electrode plate 24, although the discharge capacity was slightly reduced compared to the comparative example, no short-circuit failures occurred, and the number of exposed cracks was reduced to about half compared to the comparative example. Furthermore, in Example 4, in which the insulating tape 6 of the first form 6A was used on both sides of the positive electrode plate 24, it was confirmed that both short-circuit failures and the number of exposed cracks were reduced to zero.

[0037] As described above, in the cylindrical battery 2 according to this disclosure, the side edge of the insulating tape 6 covering the exposed portion 4ex of the positive electrode plate 24 is formed to have an angular difference θ with respect to the axial direction Z. Therefore, when winding the positive electrode plate 24, concentrated load from the side edge of the insulating tape 6 to the layer of positive electrode active material 5 is mitigated, and the occurrence of exposed cracks can be suppressed. Accordingly, the cylindrical battery 2 according to this disclosure can improve the short-circuit quality of the positive electrode plate 24.

[0038] <Embodiments of the Invention> A first embodiment of the present invention is a cylindrical battery comprising an electrode body formed by winding stacked positive electrode plates, a separator, and a negative electrode plate, wherein the positive electrode plate comprises a positive electrode substrate, a positive electrode active material provided on the surface of the positive electrode substrate, a positive electrode lead connected to an exposed portion of the positive electrode substrate, and an insulating tape covering the exposed portion, and the side edges of the insulating tape on both sides in the winding direction have an angular difference with respect to the axial direction of the electrode body.

[0039] In the cylindrical battery according to the first embodiment, the insulating tape used to insulate the exposed portion of the positive electrode substrate connected to the positive electrode lead has an angular difference in the winding direction relative to the axial direction of the electrode body. As a result, in the cylindrical battery, concentrated load from the side edge of the insulating tape to the layer of positive electrode active material is alleviated when the positive electrode plate is wound, and the occurrence of exposed cracks can be suppressed. Therefore, the cylindrical battery according to this embodiment can improve the short-circuit quality of the positive electrode plate.

[0040] A second embodiment of the present invention is a cylindrical battery in which, in the first embodiment described above, the angle difference expands continuously inward from both sides in the winding direction of the insulating tape.

[0041] According to the second embodiment, since the side edges of the insulating tape have a shape that curves inward in the winding direction, the angular difference can be widened near the axial center of the positive electrode substrate, where cracks tend to expand if cracks occur in the positive electrode active material layer, thereby effectively suppressing the occurrence of exposed cracks.

[0042] A third embodiment of the present invention is a cylindrical battery in which the side edge of the insulating tape is straight, as in the first embodiment described above.

[0043] According to the third embodiment, the insulating tape is easy to form because it has a simple trapezoidal shape, and the area of ​​the positive electrode active material covered by the insulating tape is suppressed, thus suppressing a decrease in the discharge capacity of the cylindrical battery.

[0044] A fourth embodiment of the present invention is a cylindrical battery in which, in any of the first to third embodiments described above, the exposed portion of the positive electrode plate is shorter than the positive electrode substrate in the axial direction of the electrode body.

[0045] According to the fourth embodiment, by setting the axial width of the insulating tape to be shorter than that of the positive electrode substrate, the angular difference between the side edge of the insulating tape and the axial direction can be increased, thereby effectively suppressing the occurrence of exposed cracks.

[0046] A fifth embodiment of the present invention is a method for manufacturing a cylindrical battery including an electrode body in which stacked positive electrode plates, a separator, and a negative electrode plate are wound together, comprising: an active material coating step of providing a positive electrode active material on the surface of a positive electrode substrate; a lead connection step of connecting positive electrode leads to an exposed portion of the positive electrode substrate; and an insulation step of covering the exposed portion with insulating tape, wherein in the insulation step, an angular difference with respect to the axial direction of the electrode body is provided at the side edges on both sides of the winding direction of the insulating tape.

[0047] In the manufacturing method of a cylindrical battery according to the fifth embodiment, an insulating tape for insulating the exposed portion of the positive electrode substrate connected to the positive electrode lead is provided with an angular difference with respect to the axial direction of the electrode body at the side edge in the winding direction. This reduces concentrated load from the side edge of the insulating tape to the layer of positive electrode active material when the positive electrode plate is wound, and suppresses the occurrence of exposed cracks. Therefore, according to the manufacturing method of a cylindrical battery according to this embodiment, the short-circuit quality of the positive electrode plate can be improved.

[0048] A sixth embodiment of the present invention is a method for manufacturing a cylindrical battery, in which, in the fifth embodiment described above, the angle difference expands continuously inward from both sides in the winding direction of the insulating tape.

[0049] According to the sixth embodiment, since the side edges of the insulating tape have a shape that curves inward in the winding direction, the angular difference can be widened near the axial center of the positive electrode substrate where cracks tend to expand if cracks occur in the positive electrode active material layer, thereby effectively suppressing the occurrence of exposed cracks.

[0050] A seventh embodiment of the present invention is a method for manufacturing a cylindrical battery, wherein, in the fifth embodiment described above, the side edge of the insulating tape is in a straight shape.

[0051] According to the seventh embodiment, the insulating tape is easy to form because it has a simple trapezoidal shape, and the area of ​​the positive electrode active material covered by the insulating tape is suppressed, thus suppressing a decrease in the discharge capacity of the cylindrical battery.

[0052] An eighth embodiment of the present invention is a method for manufacturing a cylindrical battery, in which, in any of the fifth to seven embodiments described above, the exposed portion of the positive electrode plate is formed to be shorter than the positive electrode substrate in the axial direction of the electrode body.

[0053] According to the eighth embodiment, by setting the axial width of the insulating tape to be shorter than that of the positive electrode substrate, the angular difference between the side edge of the insulating tape and the axial direction can be increased, thereby effectively suppressing the occurrence of exposed cracks. [Explanation of Symbols]

[0054] 2 Cylindrical batteries 4 Positive electrode substrate 4ex exposed part 5 Cathode active material 6. Insulating tape 22 Electrode body 24 Positive electrode plate 30 Positive leads θ angle difference

Claims

1. The electrode body includes a stacked positive electrode plate, a separator, and a negative electrode plate wound together. The positive electrode plate comprises a positive electrode substrate, a positive electrode active material provided on the surface of the positive electrode substrate, a positive electrode lead connected to an exposed portion of the positive electrode substrate, and an insulating tape covering the exposed portion. A cylindrical battery wherein the side edges of the insulating tape on both sides in the winding direction have an angular difference from the direction along the axial direction of the electrode body when viewed from the stacking direction of the electrode body.

2. The cylindrical battery according to claim 1, wherein the angle difference expands continuously from both sides in the winding direction of the insulating tape toward the inside.

3. The cylindrical battery according to claim 1, wherein the side edge of the insulating tape is in a straight shape.

4. The cylindrical battery according to any one of claims 1 to 3, wherein the exposed portion of the positive electrode plate is shorter than the positive electrode substrate in the axial direction of the electrode body.

5. A method for manufacturing a cylindrical battery, which includes an electrode body in which stacked positive electrode plates, a separator, and a negative electrode plate are wound together, A process of coating an active material to provide a positive electrode active material on the surface of a positive electrode substrate, A lead connection step involves connecting a positive electrode lead to the exposed portion of the positive electrode substrate. The process includes an insulation step of covering the exposed portion with insulating tape, A method for manufacturing a cylindrical battery, wherein in the insulation step, the side edges on both sides of the winding direction of the insulating tape are given an angular difference from the direction along the axial direction of the electrode body when viewed from the stacking direction of the electrode body.

6. The method for manufacturing a cylindrical battery according to claim 5, wherein the angle difference expands continuously from both sides in the winding direction of the insulating tape toward the inside.

7. The method for manufacturing a cylindrical battery according to claim 5, wherein the side edge of the insulating tape is in a straight shape.

8. The method for manufacturing a cylindrical battery according to any one of claims 5 to 7, wherein the exposed portion of the positive electrode plate is formed to be shorter than the positive electrode substrate in the axial direction of the electrode body.

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