Cylindrical rechargeable battery

Abstract

To provide a cylinder-shaped secondary battery in which a cylinder-shaped electrode group arranged by winding positive and negative electrode plates is fixed to an outer can with a simple structure.SOLUTION: A cylinder-shaped secondary battery 1 comprises: a bottomed cylinder-shaped outer can 10; an electrode group 12 formed by winding around a positive electrode plate 16 and a negative electrode plate 18 through a separator 20 and contained in the outer can together with a liquid electrolyte; and a negative electrode collector 21 disposed between a bottom 10A of the outer can and the electrode group and serving to electrically connect the negative electrode plate to the outer can. In the negative electrode plate making a side of the electrode group, an end edge part 18A on a negative electrode collector side is larger, in thickness, than a part other than the end edge part. The outer can has a thickened part of which the inner diameter of the side in the vicinity of the bottom is smaller than other parts. An end edge part of the electrode group is fixed to the outer can by the thickened part.SELECTED DRAWING: Figure 1

Description

Technical Field

[0004] , , ,

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

Background Art

[0002] Generally, an alkaline storage battery is manufactured as follows. First, a separator is interposed between a positive electrode plate and a negative electrode plate, and these are wound in a spiral shape to form a substantially cylindrical electrode group. A negative electrode current collector is welded to the negative electrode side of the electrode group. Next, the electrode group is housed in a bottomed outer can, and a welding rod is passed through a central hole from which the core of the electrode group has been removed, and the negative electrode current collector is welded to the bottom of the outer can. In this way, by resistance welding, the electrode group is fixed to the current collector and further fixed to the outer can, thereby electrically connecting and fixing the electrode group to the outer can. Thereafter, a positive electrode current collector having a current collecting lead is welded to the positive electrode side of the electrode group, and the outer can is filled with an electrolytic solution. Further, the current collecting lead is welded to a sealing body, and the sealing body is attached to the opening of the outer can via an insulating gasket and caulked to seal the outer can (see Japanese Patent Application Laid-Open No. 2003-168415).

Prior Art Documents

[0005] Therefore, as described in Japanese Patent Publication No. 2005-129433, for example, a configuration was proposed in which the current collector is formed into a bottomed cylindrical shape and attached to cover the negative electrode side of the electrode group, while a groove extending in the circumferential direction is formed on the side surface of the battery case, and the groove is brought into contact with the side surface of the current collector to fix the electrode group to the battery case. However, there were concerns that the shape of the current collector was complex and that the number of steps in battery manufacturing would increase.

[0006] The objective of the present invention is to provide a cylindrical secondary battery that has a simple structure while ensuring secure fixation of the electrode group to the outer casing. [Means for solving the problem]

[0007] To achieve the above objective, the cylindrical secondary battery of the present invention comprises a cylindrical outer casing including one closed end as the bottom; an electrode group housed together with an electrolyte in the outer casing, each consisting of a strip-shaped positive electrode plate and a negative electrode plate superimposed with a separator in between, and wound in a spiral shape around the width direction of the positive electrode plate and the negative electrode plate as the axis, with the outermost surface of the spiral winding being the negative electrode plate; and a plate-shaped negative electrode current collector positioned between the bottom of the outer casing and the electrode group, in contact with the bottom and in contact with the negative electrode plate, wherein the thickness of the edge of the negative electrode plate on the negative electrode current collector side is greater than the thickness of the remaining portion, and at least one of the edge of the negative electrode plate and the edge of the negative electrode current collector constituting the outermost surface is in contact with and fixed to the inner circumferential surface extending in the axial direction of the outer casing. [Effects of the Invention]

[0008] According to the cylindrical secondary battery of the present invention, the electrode group can be connected or fixed to the negative electrode current collector and the outer casing without resistance welding. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view of a cylindrical nickel-metal hydride secondary battery according to one embodiment, showing a portion cut out and the battery unfolded. [Figure 2] This is a longitudinal cross-section of the outer can near the bottom. [Figure 3] This is an unfolded view of the negative electrode core contained within the negative electrode plate. [Figure 4] This is a plan view showing the negative electrode plate, separator, and positive electrode plate stacked together. [Figure 5] This is a cross-sectional view of the negative electrode side of the battery. [Figure 6] This is a cross-sectional view of the negative electrode side of a battery according to another embodiment. [Figure 7] This is a cross-sectional view of the negative electrode side of the battery, which is a modified example of the embodiment shown in Figure 5. [Modes for carrying out the invention]

[0010] Below, a nickel-metal hydride secondary battery (hereinafter simply referred to as "battery") as a cylindrical secondary battery according to one embodiment will be described with reference to the drawings.

[0011] Figure 1 shows, for example, an AA-sized cylindrical battery 1 with a height of 50.5 mm and an outer diameter of 14.5 mm. The battery 1 contains a group of approximately cylindrical electrodes 12 together with an alkaline electrolyte, housed in a bottomed cylindrical outer casing 10, and the opening of the outer casing 10 is sealed by a sealing body 24. The sealed end of the outer casing 10 functions as the positive electrode, and the outer surface of the outer casing 10 functions as the negative electrode.

[0012] The outer can 10 is formed into a cylindrical shape from nickel-plated steel sheet using a multi-stage press, with one end in the axial direction becoming the can bottom 10A and the other end being open. The outer can 10 has a side thickness of 0.15 to 0.2 mm and a can bottom 10A thickness of 0.3 to 0.35 mm, with the can bottom 10A being thicker than the side 10B.

[0013] Furthermore, as shown in Figure 2, the outer casing 10, before assembly as a battery 1, has a cylindrical thick-walled portion 10B1 on the bottom 10A side and a cylindrical side portion 10B2 that extends continuously with the thick-walled portion 10B1 toward the positive electrode side of the battery 1. The thick-walled portion 10B1 is cylindrical, with the edge 10a of the bottom 10A as one end of its width and a height H1 along the axial direction of the outer casing 10 from the edge 10a as the other end of its width. The thickness of the thick-walled portion 10B1 is formed to be thicker than the thickness of the side portion 10B2. Therefore, if the thick-walled portion protrudes further toward the central axis of the outer casing than the side portion, the inner diameter of the thick-walled portion of the outer casing will be smaller than the inner diameter of the side portion. The above-mentioned side thickness of 0.15 to 0.2 mm is the thickness of the side portion 10B2. Also, height H1 is an example of a second length.

[0014] Each electrode group 12 consists of a strip-shaped positive electrode plate 16, a negative electrode plate 18, and a separator 20. The electrode group 12 is wound in a spiral shape with the separator 20 interposed between the positive electrode plate 16 and the negative electrode plate 18, and has an overall substantially cylindrical shape. The outermost part of the electrode group 12, the so-called cylindrical side surface, is composed only of the negative electrode plate 18, and the positive electrode plate 16 is not exposed on the side surface. The negative electrode plate 18, which constitutes the outermost part of the electrode group 12, is in contact with the inner surface of the outer casing 10, thereby connecting the negative electrode plate 18 to the outer casing 10.

[0015] The positive electrode plate 16 consists of a conductive positive electrode substrate that extends in a strip shape in the longitudinal direction, has a porous structure, and has numerous voids, and a positive electrode mixture held in the voids and on the surface of the positive electrode substrate. The positive electrode substrate is plated with a metal such as nickel that exhibits conductivity, and the positive electrode mixture is filled into the plated positive electrode substrate. The positive electrode mixture includes positive electrode active material particles, a conductive material, a positive electrode additive, and a binder. When the positive electrode substrate coated with the positive electrode mixture is rolled, the positive electrode plate 16 is completed.

[0016] The negative electrode plate 18 is an electrode containing a hydrogen storage alloy, and is composed of a strip-shaped conductive negative electrode core 19 and a negative electrode mixture held by the negative electrode core 19. As shown in FIG. 3, the negative electrode core 19 is made of a metal sheet having a large number of through holes formed in the thickness direction. The negative electrode core 19 is manufactured in a strip shape with the winding direction of the electrode group 12 as the longitudinal direction. In the present embodiment, the negative electrode core 19 is made of, for example, a metal sheet having a width of 59.5 mm and a thickness of 60 μm.

[0017] More specifically, the negative electrode core 19 is composed of strip-shaped non-porous portions A1 and A2 extending a predetermined width W from each of one end portion E1 and the other end portion E2 in the width direction, and a porous portion A3 located between the non-porous portions A1 and A2. In the present embodiment, W is 3.1 mm. Since the non-porous portions A1 and A2 have no through holes penetrating in the thickness direction, their surfaces are flat, and mechanical strength is imparted to the negative electrode core 19. A large number of through holes penetrating in the thickness direction are formed in the porous portion A3, and the negative electrode mixture is held not only on the surface of the negative electrode core 19 but also inside the through holes.

[0018] After the negative electrode mixture is applied to the negative electrode core 19, it is dried and roll-pressed. In the present embodiment, the thickness of the negative electrode plate 18 after rolling is 0.342 mm in the regions corresponding to the non-porous portions A1 and A2, and 0.334 mm in the region corresponding to the porous portion A3. That is, the thickness of the negative electrode plate corresponding to the non-porous portions A1 and A2 is thicker than the thickness of the negative electrode plate corresponding to the porous portion A3, and the difference is 8 μm. This is presumably because the negative electrode mixture applied to the negative electrode core 19 reduces the thickness in the porous portion A3 due to the filling of the mixture in the through holes during rolling, but in the non-porous portions A1 and A2, since there are no through holes, the compression ratio is smaller than that in the porous portion A3 even after rolling. Thus, the thickness of the non-porous portions A1 and A2 is thicker than the thickness of the porous portion A3.

[0019] The separator 20 is made of, for example, a non-woven fabric of polyolefin fibers to which a hydrophilic group is added.

[0020] For example, alkaline electrolytes such as potassium hydroxide aqueous solution, lithium hydroxide aqueous solution, sodium hydroxide aqueous solution, or mixtures thereof can be used.

[0021] The electrode group 12 assembled as described above is housed inside the outer casing 10 via a plate-shaped negative electrode current collector 21.

[0022] After housing the electrode group 12 in the outer casing 10, one end of the positive electrode current collector 22 is electrically connected to the positive electrode plate 16 near the opening of the outer casing 10, and the other end is welded to the inner surface of a conductive circular sealing body 24. The sealing body 24 has a gas vent hole 26 in the center, and a rubber valve body 28 is positioned on the outer surface of the sealing body 24 to close the gas vent hole 26. Furthermore, a flanged cylindrical positive electrode terminal 30 covering the valve body 28 is fixed to the outer surface of the sealing body 24, and the positive electrode terminal 30 presses the valve body 28 against the sealing body 24.

[0023] The sealing body 24 is located at the open end of the outer can 10, and an insulating gasket 32 ​​is sandwiched between the outer circumference of the sealing body 24 and the inner surface of the outer can 10. The sealing body 24 and the insulating gasket 32 ​​are fixed to the open end of the outer can 10 by crimping the portion of the outer can 10 on the open end side of the electrode group 12. The insulating gasket 32 ​​insulates and seals the space between the outer circumference of the sealing body 24 and the outer can 10.

[0024] Battery 1 is assembled as described above.

[0025] To fabricate the electrode group 12, when winding the positive electrode plate 16 and the negative electrode plate 18 with a separator 20 interposed therebetween between the two electrode plates 16 and 18, as shown in FIG. 4, for example, the negative electrode plate 18, the separator 20, and the positive electrode plate 16 are stacked in this order. At this time, while aligning the longitudinal directions of the negative electrode plate 18 and the positive electrode plate 16, after shifting the positive electrode plate 16 by a length L in one direction in the width direction with respect to the negative electrode plate 18, the positive electrode plate 16 and the negative electrode plate 18 are wound about its width direction, that is, with the longitudinal direction of the electrode plates 16 and 18 as the winding direction. Note that the length L is an example of the first length. Thereby, in the electrode group 12, from one end portion, the end portion E1 of the negative electrode plate 18 protrudes in a spiral shape, and from the other end portion, the edge portion of the positive electrode plate 16 protrudes in a spiral shape. The end portion E1 of the negative electrode plate 18 protruding in a spiral shape becomes the negative electrode side end portion 18A of the electrode group 12. Note that the winding shift length L is set to a length not exceeding the length W corresponding to the width of the non-porous portion A1 of the negative electrode plate 18 (L < W). This is because if the positive electrode plate 16 is shifted with respect to the negative electrode plate 18 by more than the width W of the non-porous portion A1, the mechanical strength of the entire electrode group 12 will be impaired.

[0026] The electrode group 12 assembled as described above is housed in the exterior can 10 such that the negative electrode side end portion 18A of the electrode group 12 contacts the can bottom 10A through the plate-shaped negative electrode current collector 21 having a thickness T0. At this time, as shown in FIG. 5, the negative electrode side end portion 18A of the electrode group 12 is in sliding contact with the inner peripheral surface of the thick portion 10B1 of the exterior can side surface 10B. Further, since the electrode group 12 is only wound in a spiral shape, a force acting radially outward of the exterior can 10 to unwind is applied to the inner peripheral surface of the exterior can 10. As a result, the electrode group 12 is fixed to the exterior can 10 and becomes immobile. Further, due to the electrode group 12 being fixed to the exterior can 10, the negative electrode current collector 21 positioned between the negative electrode side end portion 18A of the electrode group 12 and the can bottom 10A of the exterior can is also sandwiched and fixed between the inner peripheral surface of the exterior can 10 and the negative electrode side end portion 18A of the electrode group 12.

[0027] In this way, the negative electrode current collector 21 is fixed and immobile between the inner circumferential surface of the outer casing 10 and the negative electrode end 18A of the electrode group 12, so that the connection between the negative electrode current collector 21 and either the electrode group 12 or the outer casing 10 is maintained. Furthermore, the negative electrode current collector 21 is electrically connected to either the electrode group 12 or the outer casing 10, keeping the internal resistance of the battery 1 low and suppressing an increase in internal resistance.

[0028] Furthermore, after sealing the outer can 10 with the sealing body 24, the outer can 10 can be drawn from the bottom 10A toward the opening end in order to reduce the battery diameter. In this case, the inner diameter of the thick-walled portion 10B1 of the outer can becomes smaller, so the contact of the electrode group 12 by the thick-walled portion 10B1 can be made more secure. Also, when drawing the battery 1, the inner diameter of the outer can 10 before assembly may be equal in both the thick-walled portion and the side portion.

[0029] In the configuration of the battery 1 described above, the height H1 of the thickened portion is made smaller than the length L of the offset of the positive electrode plate 16 relative to the negative electrode plate 18. This height H1 is in the range of 0.5 mm to 2.0 mm. If the height H1 of the thickened portion 10B1 is less than 0.5 mm, it will be approximately the same as the thickness of the can bottom 10A (0.3 to 0.35 mm), and the contact area between the negative electrode end 18A and the thickened portion 10B1 will be small. Therefore, even if the outer can 10 is drawn, the effect of narrowing the diameter of the outer can 10 cannot be expected, and it may not be possible to fix the electrode group 12 to the outer can 10.

[0030] On the other hand, if the height H1 of the thickened portion 10B1 exceeds 2.0 mm, the narrowed diameter of the thickened portion 10B1 pushes the negative electrode plate 18, which is located on the outermost periphery, toward the central axis of the outer can 10. This pushes the negative electrode plate 18 too close to the adjacent positive electrode plate 16, which may cause a short circuit between the electrode plates 16 and 18. Therefore, it is preferable that the height H1 of the thickened portion be in the range of 0.5 mm to 2.0 mm.

[0031] Thus, in the above embodiment, resistance welding is not used for connecting the negative electrode current collector 21 to the electrode group 12, nor for connecting the electrode group 12 to the outer casing 10, so the battery 1 can be assembled in fewer steps. In addition, the thick-walled portion 10B1 of the outer casing 10 is in direct contact with the non-perforated portion A1 of the negative electrode plate 18, and the non-perforated portion A1 of the negative electrode plate 18 has greater mechanical strength than the perforated portion A3 because it does not have through holes. Therefore, the electrode group 12 can be fixed to the outer casing 10 more securely.

[0032] Furthermore, by utilizing the difference in thickness between the non-perforated sections A1 and A2 and the perforated section A3 that occurs when creating the negative electrode plate 18, the axial movement of the electrode group 12 in the outer casing 10 is suppressed, and the electrode group 12 is fixedly connected to the outer casing 10, thus avoiding an increase in the number of manufacturing steps for the battery 1 compared to conventional methods.

[0033] Furthermore, since resistance welding is not performed, it is not necessary to insert a jig such as a welding rod into the center of the electrode group 12 after the electrode plates 16 and 18 have been wound, thus suppressing the occurrence of defective batteries 1 due to interference between the jig and the electrode plates 16 and 18.

[0034] Furthermore, when resistance welding the electrode group 12 to the outer casing 10, it was not possible to visually inspect the welded area even if welding defects occurred. However, by eliminating the need to check for the occurrence of such defects, the manufacturing process of the battery 1 can be reduced.

[0035] In the above embodiment, the side surface 10B of the outer can 10 has a thickened portion 10B1 and a side surface portion 10B2, and its thickness is configured to change along the axial direction from the bottom 10A. In a second embodiment different from the above embodiment, the outer can 10' can be configured such that the side surface 10B' has a constant thickness along the axial direction from the bottom 10A'. The second embodiment will be described below.

[0036] In the second embodiment, the components constituting the battery 1' are the same as in the above embodiment, except for the outer casing 10'.

[0037] After housing the electrode group 12 in the outer can 10', a groove 10G is formed circumferentially, as shown in Figure 7, at a height H2 that is longer than the thickness Tb of the outer can bottom 10A' and does not exceed the length (Tb+L) in the axial direction from the bottom 10A' of the outer can 10'. This is known as beading. As a result, in a cross section perpendicular to the axis of the outer can 10', the inner surface portion 10H of the outer can corresponding to the groove 10G abuts against and locks with the vicinity of the edge portion 18A of the negative electrode plate 18 that constitutes the side surface of the electrode group 12. Note that the groove 10G is an example of a recessed portion.

[0038] Furthermore, at this time, the inner diameter of the groove 10G formed on the inner surface 10H of the outer can is smaller than the diameter of the negative electrode end 18A of the electrode group 12. Therefore, the movement of the electrode group 12 in the axial direction of the outer can 10' is suppressed.

[0039] In the assembly of the battery 1' described above, resistance welding is not performed to connect the negative electrode current collector 21 to the negative electrode end 18A of the electrode group 12. Furthermore, resistance welding is not performed to fix the electrode group 12 to the outer casing 10' after it has been housed in the outer casing 10'. Instead of these two welding processes, the groove 10G of the outer casing 10 is brought into contact with the non-perforated portion A1 of the negative electrode plate, which becomes the negative electrode end 18A of the electrode group 12, thereby fixing the electrode group 12 to the bottom 10A of the outer casing 10' via the negative electrode current collector 21. This configuration suppresses movement of the negative electrode current collector 21 relative to the negative electrode end 18A of the electrode group 12. Therefore, movement of the electrode group 12 and the negative electrode current collector 21 relative to the outer casing 10' is also suppressed, preventing an increase in the AC resistance value of the battery 1.

[0040] Furthermore, by utilizing the difference in thickness between the non-perforated sections A1 and A2 and the perforated section A3 that occurs when creating the negative electrode plate 18, the axial movement of the electrode group 12 in the outer casing 10 is suppressed, and the electrode group 12 is fixedly connected to the outer casing 10, thus avoiding an increase in the number of manufacturing steps for the battery 1 compared to conventional methods.

[0041] Furthermore, since resistance welding is not performed, it is not necessary to insert a jig such as a welding rod into the center of the electrode group 12 after the electrode plates 16 and 18 have been wound, thereby suppressing the occurrence of defective batteries 1' due to interference between the jig and the electrode plates 16 and 18.

[0042] Furthermore, when resistance welding the electrode group 12 to the outer casing 10', it was not possible to visually inspect the welded area even if welding defects occurred. However, by eliminating the need to check for the occurrence of such defects, the manufacturing process of the battery 1' can be reduced.

[0043] In the above embodiments, the negative electrode side of the electrode group is fixed by contacting it with the outer can 10. However, the same effect as in the above embodiments can be obtained by making the diameter of the negative electrode current collector 21 larger than the diameter of the electrode group and bringing it into contact with the side surface near the bottom of the outer can.

[0044] The battery size in the above embodiment is AA size, but the battery size is not limited to this. [Explanation of symbols]

[0045] 1 battery 10 outer cans 10A can bottom 12 electrode groups 16 Positive plate 18 Negative plate 18A Negative end 20 Separators 21 Negative electrode current collector

Claims

1. A cylindrical outer can with one closed end as the bottom, Each electrode group consists of a strip-shaped positive electrode plate and a negative electrode plate, superimposed with a separator in between, and wound in a spiral shape around the width direction of the positive electrode plate and the negative electrode plate as axes, with the outermost surface of the spiral winding being the negative electrode plate, and is housed together with the electrolyte in the outer container. A plate-shaped negative electrode current collector is positioned between the bottom of the outer can and the electrode group, and is in contact with the bottom and the negative electrode plate. Equipped with, The negative electrode plate has a thickness at the edge on the negative electrode current collector side that is thicker than the thickness of the remaining portion. At least one of the edges of the negative electrode plate constituting the outermost surface and the edge of the negative electrode current collector is fixed in contact with the inner surface extending in the axial direction of the outer casing. The outer can has a recessed portion on the side surface near the bottom that is recessed toward the axis of the outer can and extends in a linear fashion in the circumferential direction. A cylindrical secondary battery in which the electrode group is fixed to the outer casing by the edge of the negative electrode plate being locked in the axial direction to the recess inside the outer casing.

2. The cylindrical secondary battery according to claim 1, wherein the outer casing has an inner diameter of the side near the bottom that is smaller than the inner diameter of the remaining side.

3. The negative electrode plate consists of a strip-shaped core and a negative electrode mixture layer on which the negative electrode mixture is coated. The aforementioned core body is A flat, non-perforated portion is located at one end and the other end in the width direction, and extends in a winding direction intersecting the width direction, A perforated portion located between the non-perforated portions and having multiple through-holes that penetrate in the thickness direction of the core body into which the negative electrode mixture enters, A cylindrical secondary battery according to claim 1 or 2, having the following features.

4. The positive electrode plate is wound in a spiral shape around the negative electrode plate with a first length offset in the width direction, thereby forming the electrode group. The cylindrical secondary battery according to any one of claims 1 to 3, wherein the side surface of the outer casing has a thickened portion with a width extending from the bottom to a portion of a second length in the axial direction, and the second length is shorter than the first length and in the range of 0.5 mm to 2.0 mm.

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