JP2018055812A - Collector load, manufacturing method of alkaline secondary battery with collector lead, and alkaline secondary battery manufactured by manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a collector load contributed to improvement of an efficient discharge property by suppressing occurrence of a welding defect, an alkaline secondary battery with the collector lead, and a manufacturing method of the alkaline secondary battery.SOLUTION: A collector lead 34 integrated in a nickel hydrogen secondary battery 1 includes: a rectangular top wall part 36; a pair of sidewall parts 42 and 44 extending from both side edges 38 and 40 of the tol wall part 36; and leg parts 50 and 52 connected to the sidewall parts 42 and 44 and located at positions facing the top wall part 36. The top wall part 36 has a curved shape protruding outsides and includes multiple top wall side projections 56. Each of the leg parts 50 and 52 has a curved shape protruding outsides and includes multiple leg part side projections 58. The top wall side projection 56 protrudes from an apex portion 36a of the curved shape in the top wall part 36, and the leg part side projection 58 protrudes from an apex portion 53 of the curved shape in the leg parts 50 and 52.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a current collecting lead, a method for producing an alkaline secondary battery including the current collecting lead, and an alkaline secondary battery produced by the production method.

  In alkaline secondary batteries, applications are expanding and batteries of a type that can be charged and discharged at a high rate have been developed. As such a battery, for example, a cylindrical alkaline secondary battery as shown below is known.

  The cylindrical alkaline secondary battery is formed by accommodating an electrode group together with an alkaline electrolyte in a bottomed cylindrical outer can and sealing the opening of the outer can with a sealing body including a positive electrode terminal.

  The electrode group described above is formed by spirally winding a positive electrode and a negative electrode that are overlapped with a separator interposed therebetween, and has a substantially cylindrical shape as a whole. Here, the positive electrode and the negative electrode are arranged so as to be slightly shifted from each other in the direction along the axis of the electrode group during the winding operation, and a separator of a predetermined size is provided between the positive electrode and the negative electrode. Is arranged at a predetermined position. In this state, the positive electrode, the separator, and the negative electrode are wound. As a result, the edge of the positive electrode protrudes spirally from one end surface side of the electrode group, and the edge of the negative electrode protrudes spirally from the other end surface side of the electrode group.

  A positive electrode current collector is welded to the protruding positive electrode edge, and a negative electrode current collector is welded to the protruding negative electrode edge. Thereby, the positive electrode current collector is electrically connected to the positive electrode in a wide range, and the negative electrode current collector is electrically connected to the negative electrode in a wide range, so that the current collection efficiency is improved. As a result, the battery can be charged / discharged at a high rate.

  As a procedure for assembling the cylindrical alkaline secondary battery, for example, an electrode group is first inserted into the outer can, and the inner surface of the bottom wall of the outer can and the negative electrode current collector are welded. Thereby, the outer can which also serves as the negative electrode terminal and the negative electrode are electrically connected. Next, one end of a positive electrode tab made of a thin metal plate is welded to a predetermined position of the positive electrode current collector. Furthermore, the other end of the positive electrode tab is welded to a predetermined position of the sealing body. As a result, the positive electrode terminal and the positive electrode are electrically connected. Thereafter, the sealing body is attached in a state where an insulating gasket is interposed in the upper end opening of the outer can, and the upper end opening of the outer can is caulked to seal the outer can. Thereby, a cylindrical alkaline secondary battery is formed.

  For the positive electrode tab as described above, a relatively long one is used in order to facilitate welding to the sealing body. Further, when the sealing body is attached to the upper end opening of the outer can, the positive electrode tab is accommodated in the outer can so as to bend between the sealing body and the electrode group. For this reason, the positive electrode tab is relatively thin so as to be easily bent.

  Incidentally, in recent years, higher performance is desired for alkaline secondary batteries, and in particular, it is desired to further improve the high-rate discharge characteristics so that a large current can be efficiently output.

  In order to improve the high rate discharge characteristics, it is necessary to make the internal resistance of the battery as low as possible. However, when a thin and long strip-like positive electrode tab as described above is used, the specific resistance of the positive electrode tab is high, and the positive electrode tab increases the internal resistance of the battery.

  Therefore, various attempts have been made to shorten the energization path as compared with the prior art in order to lower the internal resistance of the battery and to obtain a battery excellent in high rate discharge characteristics. For example, a battery as disclosed in Patent Document 1 is known as a battery in which measures for shortening the energization path are taken.

  In the battery represented by Patent Document 1, a current collecting lead is used instead of the positive electrode tab. The current collecting lead is formed by processing a metal plate material that is thicker than a conventional positive electrode tab into a shape that connects the positive electrode current collector and the sealing body as short as possible. Such a current collecting lead is interposed between the positive electrode current collector and the sealing body, and the positive electrode current collector, the current collecting lead and the sealing body are connected by resistance spot welding. Thereby, since an energization path can be shortened and an energization path can be made thick, the internal resistance of a battery reduces.

  Here, there are various shapes of current collecting leads, and examples thereof include a cylindrical current collecting lead 100 having a flat cross-sectional shape as shown in FIG. The current collecting lead 100 is disposed between the sealing body 102 and the positive electrode current collector 104. The current collecting lead 100 includes a flat top wall portion 106 positioned on the sealing body 102 side, side wall portions 112 and 114 extending from predetermined side edges 108 and 110 of the top wall portion 106, and top portions of the side wall portions 112 and 114. It has a flat bottom wall 120 that extends from the edges 116 and 118 opposite to the wall 106 and is positioned on the positive electrode current collector 104 side. A plurality of top wall side protrusions 124 are provided at predetermined positions on the outer surface of the top wall portion 106, and a plurality of bottom wall side protrusion portions 126 are provided at predetermined positions on the outer surface of the bottom wall portion 120. It has been.

  Here, the current collecting lead 100 is designed in advance so as to be preferentially crushed in order to prevent excessive stress from being applied to the positive electrode current collector and the electrode group under the resistance spot welding and the caulking process of the sealing body. Has been. For example, the corners of the side edges 108 and 110 and the end edges 116 and 118 are eliminated to form a round shape. Thereby, the flexibility of the current collecting lead 100 is improved, and the current collecting lead 100 is more easily deformed than the sealing body 102 and the positive electrode current collector 104.

  In the battery manufacturing process, an electrode group to which the positive electrode current collector 104 is welded is inserted into an outer can, and a current collecting lead 100 is placed on the positive electrode current collector 104 of the electrode group. A sealing body 102 is placed on the lead 100. At this time, in the current collecting lead 100, the top wall side protruding portion 124 of the top wall portion 106 contacts the sealing body 102, and the bottom wall side protruding portion 126 of the bottom wall portion 120 contacts the positive electrode current collector 104. When the sealing body 102, the current collector lead 100, and the positive electrode current collector 104 are resistance spot welded, the welding current is concentrated on the top wall side protrusion 124 and the bottom wall side protrusion 126, and these top wall side protrusions. The periphery including 124 and the bottom wall side protrusion 126 is melted to form a weld. Thereby, the sealing body 102, the current collection lead 100, and the positive electrode current collector 104 are connected. Thereafter, the sealing body 102 is attached to the opening of the outer can by caulking the opening edge of the outer can.

  During resistance spot welding or during caulking of the sealing body, stress is applied in a direction along the axial direction of the battery, and the sealing body 102, the current collector lead 100, the positive electrode current collector 104, and the electrode group are pressed. . At this time, as described above, since the current collecting lead 100 is preferentially crushed and the flexibility is enhanced so as to relieve stress, the positive electrode current collector does not press the electrode group more than necessary, and the internal Generation | occurrence | production of a short circuit can be suppressed.

Japanese Patent No. 3547931

  By the way, in the pressurizing process at the time of resistance spot welding or in the caulking process of the sealing body, excessive compressive stress may be applied to the current collecting lead 100, and the degree of crushing of the current collecting lead 100 may increase. Specifically, as shown in FIG. 7B, excessive compressive stress acting in the directions of the arrows G and H near the edge portions such as the side edges 108 and 110 and the end edges 116 and 118 of the current collecting lead 100 is present. When applied, a force is applied to the current collecting lead 100 in the directions shown by the arrows I, J, M, and N, and the central portions of the top wall portion 106 and the bottom wall portion 120 are bent inwardly in a bow shape. Confirmed to happen. Since the forces in the directions shown by arrows I, J, M, and N act as shear stress on the welded portion, there is a possibility that the welded portion is cracked due to this deformation, and the weld is detached to cause poor welding. .

  When welding failure occurs in this way, the energization path becomes narrow and the internal resistance of the battery increases. As a result, the high rate discharge characteristics of the battery are hindered.

  The present invention has been made based on the above circumstances, and its object is to include a current collecting lead that suppresses the occurrence of poor welding and contributes to an improvement in high-rate discharge characteristics, and this current collecting lead. An object of the present invention is to provide an alkaline secondary battery and a method for producing the alkaline secondary battery.

  In order to achieve the above object, according to the present invention, a rectangular top wall portion, a pair of side wall portions extending from both side edges of the top wall portion, and the side wall portions are connected to and opposed to the top wall portion. A bottom wall portion positioned at a position, wherein the top wall portion has a curved shape protruding outward and has a plurality of top wall side protrusions, and the bottom wall portion And has a plurality of bottom wall-side protrusions, and the top wall-side protrusions protrude from the apex portion of the curved shape of the top wall, and The wall-side protruding portion is provided with a current collecting lead that protrudes from a curved top portion of the bottom wall portion.

  Moreover, according to the present invention, the current collecting lead preparing step for preparing the current collecting lead described above, and the electrode group preparing step for preparing the electrode group in which the positive electrode and the negative electrode are overlapped and wound in a spiral shape through the separator. The electrode group is housed in an outer can, the current collector lead is placed on the positive electrode current collector of the electrode group, and the sealing body including the positive electrode terminal is placed on the current collector lead A process, a welding step of resistance spot welding the positive electrode current collector, the current collector lead and the sealing body, and a sealing step of caulking and attaching the sealing body to the outer can, and sealing the outer can; There is provided a method of manufacturing an alkaline secondary battery in which the current collecting lead is compressed and the top wall portion and the bottom wall portion are flattened by the welding step and the sealing step.

  Furthermore, according to the present invention, an alkaline secondary battery produced by the above-described method for producing an alkaline secondary battery, comprising a bottomed cylindrical outer can including a negative terminal, a positive terminal, and the outer can A cylindrical electrode group that is wound together with an alkaline electrolyte in the outer can, in which a sealing body that seals the upper end opening of the electrode, a positive electrode and a negative electrode are overlapped via a separator and wound in a spiral shape And a positive electrode current collector connected to an edge portion of the positive electrode protruding from one end surface of the electrode group, and a current collector lead connecting the positive electrode current collector and the sealing body, The current collecting lead includes a top wall portion having a rectangular shape in plan view, a pair of side wall portions extending from both side edges of the top wall portion, a bottom connected to the side wall portion and positioned at a position facing the top wall portion. And the top wall portion is flat. A plurality of welds being connected to said sealing body, said bottom wall forms a flat, a plurality of welds are connected to the positive electrode current collector, the alkaline secondary battery is provided.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of a welding defect can be suppressed and the current collection lead which contributes to the improvement of a high rate discharge characteristic can be provided.

1 is a partial cross-sectional view showing a cylindrical nickel-metal hydride secondary battery according to the present invention. It is the top view which showed the positive electrode electrical power collector. It is the perspective view which showed the current collection lead. It is sectional drawing along the IV-IV line in FIG. It is the top view which showed the intermediate product of the current collection lead. It is the schematic which showed the process of the deformation | transformation of the current collection lead concerning this invention. It is the schematic which showed the process of the deformation | transformation of the conventional current collection lead | read | reed.

  Hereinafter, an alkaline secondary battery including a current collecting lead according to the present invention will be described with reference to the drawings.

  As an alkaline secondary battery according to an embodiment to which the present invention is applied, an AA-sized cylindrical nickel-hydrogen secondary battery (hereinafter referred to as a battery) 1 shown in FIG. 1 will be described as an example.

  The battery 1 includes an outer can 2 having a bottomed cylindrical shape with an open upper end. The outer can 2 has conductivity, and its bottom wall functions as a negative electrode terminal. In the outer can 2, an electrode group 4 is accommodated together with a predetermined amount of an alkaline electrolyte (not shown).

  As shown in FIG. 1, the opening 3 of the outer can 2 is closed by a sealing body 14. The sealing body 14 includes a disc-shaped lid plate 16 having conductivity, a valve body 20 disposed on the lid plate 16, and a positive electrode terminal 22. A ring-shaped insulating gasket 18 is disposed on the outer periphery of the cover plate 16 so as to surround the cover plate 16, and the insulating gasket 18 and the cover plate 16 are formed by caulking the opening edge 17 of the outer can 2. 2 is fixed to the opening edge 17. That is, the cover plate 16 and the insulating gasket 18 cooperate with each other to seal the opening 3 of the outer can 2. Here, the lid plate 16 has a central through hole 19 in the center, and a rubber valve body 20 is disposed on the outer surface of the lid plate 16 so as to close the central through hole 19. Furthermore, a flanged cylindrical positive terminal 22 is electrically connected to the outer surface of the cover plate 16 so as to cover the valve body 20. The positive terminal 20 presses the valve body 18 toward the cover plate 16. Further, the positive electrode terminal 22 has a gas vent hole 23 on a side surface.

  Normally, the central through hole 19 is airtightly closed by the valve body 20. On the other hand, if gas is generated in the outer can 2 and its internal pressure increases, the valve body 20 is compressed by the internal pressure, and the central through hole 19 is opened. As a result, gas is released from the outer can 2 to the outside through the central through hole 19 and the gas vent hole 23 of the positive terminal 22. That is, the central through hole 19, the valve body 20, and the gas vent hole 23 of the positive electrode terminal 22 form a safety valve for the battery 1.

  The electrode group 4 includes a strip-like positive electrode 6, a negative electrode 8, and a separator 10, which are wound in a spiral shape with the separator 10 sandwiched between the positive electrode 6 and the negative electrode 8. That is, the positive electrode 6 and the negative electrode 8 are overlapped with each other via the separator 10. Such an electrode group 4 has a cylindrical shape as a whole.

  In this electrode group 4, the edge of the positive electrode 6 is exposed in a spiral shape from one end surface, and the edge of the negative electrode 8 is exposed in a spiral shape from the other end surface. Here, the exposed edge of the positive electrode 6 is defined as a positive electrode connection edge 32, and the exposed edge of the negative electrode 8 is defined as a negative electrode connection edge (not shown). A positive electrode current collector 28 and a negative electrode current collector (not shown), which will be described later, are welded to the exposed positive electrode connection edge 32 and negative electrode connection edge.

  The negative electrode 8 has a conductive negative electrode core having a strip shape, and a negative electrode mixture is held in the negative electrode core.

  The negative electrode core is made of a band-shaped metal material in which a large number of through holes (not shown) penetrating in the thickness direction are distributed. For example, a punching metal sheet can be used as such a negative electrode core.

  The negative electrode mixture is not only filled in the through hole of the negative electrode core, but also held in layers on both surfaces of the negative electrode core.

  The negative electrode mixture includes particles of a hydrogen storage alloy, a conductive material, a binder, and the like. Here, the hydrogen storage alloy is an alloy capable of storing and releasing hydrogen, which is a negative electrode active material, and a hydrogen storage alloy generally used in nickel-hydrogen secondary batteries is preferably used. The above-described binder serves to bind the particles of the hydrogen storage alloy and the conductive material to each other and at the same time bind the negative electrode mixture to the negative electrode core. Here, as the conductive material and the binder, those generally used in nickel-hydrogen secondary batteries are preferably used.

  The negative electrode 8 can be manufactured as follows, for example.

  First, a hydrogen storage alloy powder composed of hydrogen storage alloy particles, a conductive material, a binder, and water are kneaded to prepare a paste of a negative electrode mixture. The obtained paste of the negative electrode mixture is applied to the negative electrode core and dried. After drying, the negative electrode core body to which the negative electrode mixture containing hydrogen storage alloy particles and the like is attached is subjected to roll rolling and cutting to obtain an intermediate product of the negative electrode. The intermediate product of this negative electrode has a rectangular shape as a whole. And about the predetermined | prescribed edge part which should become a negative electrode connection edge part in this intermediate product of a negative electrode, removal of a negative mix is performed. As a result, the predetermined edge portion becomes the negative electrode connection edge portion in which the negative electrode core is exposed. In this way, the negative electrode 8 having the negative electrode connection edge is obtained. Here, the method for removing the negative electrode mixture is not particularly limited, but for example, the removal is preferably performed by applying ultrasonic vibration. Note that the negative electrode mixture is still held in the region other than the negative electrode connection edge.

  Next, the positive electrode 6 will be described.

  The positive electrode 6 includes a conductive positive electrode base material having a porous structure and having a large number of pores, and a positive electrode mixture held in the pores and on the surface of the positive electrode base material.

  As the positive electrode base material, for example, foamed nickel (nickel foam) can be used.

  The positive electrode mixture includes nickel hydroxide particles as positive electrode active material particles, a cobalt compound as a conductive material, a binder, and the like. The above-described binder serves to bind the nickel hydroxide particles and the conductive material to each other and simultaneously bind the positive electrode mixture to the positive electrode base material. Here, what is generally used for the nickel-hydrogen secondary battery is suitably used as the binder.

  The positive electrode 6 can be manufactured as follows, for example.

  First, a positive electrode mixture slurry containing a positive electrode active material powder composed of positive electrode active material particles, a conductive material, water, and a binder is prepared. The obtained positive electrode mixture slurry is filled in, for example, nickel foam and dried. After drying, the nickel foam filled with nickel hydroxide particles and the like is roll-rolled and then cut into a predetermined shape to obtain an intermediate product of the positive electrode. The intermediate product of this positive electrode has a rectangular shape as a whole. And about the predetermined | prescribed edge part which should become the positive electrode connection edge part 32 in this intermediate product of a positive electrode, the positive mix is removed and the positive electrode base material is exposed. Next, the edge part from which the positive electrode mixture has been removed is compressed in the thickness direction of the intermediate product of the positive electrode to become the positive electrode connection edge part 32. Since the positive electrode base material is in a dense state by being compressed in this manner, the positive electrode connection end edge portion 32 is easily welded. In this way, the positive electrode 6 having the positive electrode connection edge portion 32 is obtained. Here, the method for removing the positive electrode mixture is not particularly limited, but for example, it is suitably performed by applying ultrasonic vibration. It should be noted that the region other than the positive electrode connection edge portion 32 is still filled with the positive electrode mixture.

  Next, as the separator 10, for example, a polyamide fiber nonwoven fabric provided with a hydrophilic functional group, or a polyolefin fiber nonwoven fabric such as polyethylene or polypropylene provided with a hydrophilic functional group can be used.

  The positive electrode 6 and the negative electrode 8 produced as described above are spirally wound with the separator 10 interposed therebetween, whereby the electrode group 4 is formed. Specifically, during winding, the positive electrode 6 and the negative electrode 8 are arranged so as to be slightly shifted from each other in the direction along the axial direction of the electrode group 4, and between the positive electrode 6 and the negative electrode 8. The separator 10 having a predetermined size is disposed at a predetermined position, and the winding operation is performed in this state. As a result, a cylindrical electrode group 4 is obtained. As an aspect of the obtained electrode group 4, in one end side of the electrode group 4, the positive electrode connection edge 32 of the positive electrode 6 protrudes from the adjacent negative electrode 8 through the separator 10. On the other end side of the electrode group 4, the negative electrode connection edge portion of the negative electrode 8 is in a state of protruding from the adjacent positive electrode 6 with the separator 10 interposed therebetween.

  The electrode group 4 is formed by winding the positive electrode 6, the negative electrode 8, and the separator 10 with a core having a predetermined outer diameter, and the core is extracted after the winding operation. A through hole 9 is formed in the center of the electrode group 4.

  In the electrode group 4 as described above, the positive electrode current collector 28 is connected to one end side, and the negative electrode current collector is connected to the other end side.

  First, the negative electrode current collector is not particularly limited, and for example, a conventionally used disk-shaped metal plate is preferably used. The prepared negative electrode current collector is welded to the negative electrode connection edge on the other end side of the electrode group 4.

  Next, the positive electrode current collector 28 will be described.

  The positive electrode current collector 28 is a plate-like body made of a conductive material, and the shape in plan view is not particularly limited, and any shape such as a disk shape or a polygonal shape can be adopted. The size of the positive electrode current collector 28 is smaller than the outer diameter size of the electrode group 4 and can cover the entire positive electrode connection edge 32 of the positive electrode 6 protruding from one end side of the electrode group 4. Is set.

  In the present embodiment, as shown in FIG. 2, a plate material having a decagonal shape in plan view is used. Specifically, the positive electrode current collector 28 is a thin plate made of Ni-plated steel having a decagonal shape as a whole, and has a circular central through hole 29 at the center and six radially extending so as to surround the central through hole 29. The slit 30 is included. The slit 30 is preferably formed by punching, and a protrusion (burr) extending downward (on the electrode group 4 side) is generated at an edge portion of the slit 30.

  In the battery 1, as shown in FIG. 1, a current collecting lead 34 is interposed between the positive electrode current collector 28 and the sealing body 14, and this current collecting lead 34 is connected to the positive electrode 6 of the electrode group 4. The positive electrode current collector 28 and the sealing body 14 having the positive electrode terminal 22 are electrically connected.

  For example, as shown in FIG. 3, the current collecting lead 34 includes a top wall portion 36 connected to the sealing body 14, and a pair of side wall portions 42 and 44 extending from predetermined side edges 38 and 40 of the top wall portion 36. The side wall portions 42 and 44 have leg portions 50 and 52 as bottom wall portions extending from end edges 46 and 48 opposite to the top wall portion 36 and connected to the positive electrode current collector 28.

  The top wall portion 36 has a substantially rectangular shape in plan view, and a circular through hole 54 is provided at the center thereof. The through hole 54 is positioned at a position facing the central through hole 19 of the cover plate 16 when the current collecting lead 34 is connected to the sealing body 14. As shown in FIG. 4, the cross-sectional shape of the top wall portion 36 is a curved shape that protrudes outward as a whole. The curved apex portion 36 a is positioned substantially at the center of the top wall portion 36.

  Further, as is apparent from FIG. 3, four top wall side protrusions 56 serving as welding points are provided on the outer peripheral surface of the top wall portion 36 around the through hole 54. And these top wall side protrusion parts 56 protrude rather than the curved vertex part 36a. That is, as shown in FIG. 4, the imaginary line L1 connecting the tip 56a of the right top wall side projection 56 and the tip 56a of the left top wall projection 56 is from the apex portion 36a of the top wall 36. Is also located on the outside.

  As described above, the side wall portions 42 and 44 extend from both side edges 38 and 40 of the top wall portion 36, and leg portions 50 and 52 extend from the end edges 46 and 48 of the side wall portions 42 and 44, respectively. Yes. As shown in FIG. 4, the side edges 38 and 40 and the end edges 46 and 48 are rounded with corners eliminated. For this reason, the side wall parts 42 and 44 have comprised the curved shape which cross-sectional shape swells outside as a whole.

  The leg portions 50 and 52 are positioned at positions facing the top wall portion 36. Moreover, the leg parts 50 and 52 have the extension parts 50a, 50b, 52a, and 52b extended in the direction along the longitudinal direction of the side wall parts 42 and 44, as shown in FIG. These extending portions 50 a, 50 b, 52 a, 52 b extend outward from the position facing the top wall portion 36, so that when the current collecting lead 34 is connected to the positive electrode current collector 28, It works to increase stability. The overall cross-sectional shape of the legs 50, 52 including these extending portions 50a, 50b, 52a, 52b is a curved shape that protrudes outward as shown in FIG. Here, a shape obtained by extending the tip of the leg 50 and the tip of the leg 52 is indicated by a virtual line 51. The curved vertex portion 53 of the leg portions 50 and 52 imaginary by the virtual line 51 is positioned substantially at the center of the leg portions 50 and 52.

  Moreover, the leg side protrusion part 58 used as a welding point is provided in the outer peripheral surface of these extension part 50a, 50b, 52a, 52b (refer FIG. 4). These leg-side protrusions 58 protrude from the curved vertex portion 53. That is, as shown in FIG. 4, an imaginary line L2 connected to the tip 58a of the right leg-side projection 58 and the tip 58a of the left leg-side projection 58 is the apex portion 53 of the legs 50, 52. It is positioned outside.

  Here, the top-wall-side protrusion 56 and the leg-side protrusion 58 are formed by, for example, pressing. Note that reference numeral 60 in FIG. 3 indicates a recess formed on the back side of the protrusion 58 when the leg 50 is provided on the leg 50, 52.

  Further, the top wall side protrusion 56 is preferably formed in a portion close to the apex portion 36 a, and the leg side protrusion 58 is preferably formed in a portion close to the apex portion 53. By doing in this way, it is easy to make the state which the top wall side projection part 56 and the leg part side projection part 58 protruded rather than the vertex part 36a and the vertex part 53, respectively.

  The current collecting lead 34 can be manufactured as follows, for example.

  First, by processing a metal thin plate, a current collector lead intermediate product 62 made of a thin plate having a substantially H-shaped plan view as shown in FIG. 5 is prepared. In addition, this thin plate is sufficiently thick compared with the conventional positive electrode tab. In the intermediate product 62, the long portions positioned on both sides are leg portion planned regions 70 and 72 that become the leg portions 50 and 52. The regions that continue to the inside of the planned leg portions 70 and 72 are the side wall portions 74 and 76 that become the side walls 42 and 44. A region sandwiched between the side wall portion planned region 74 and the side wall portion planned region 76 is a top wall portion planned region 78 that becomes the top wall portion 36.

  Further, the intermediate product 62 is provided with a through hole 54 at the center of the planned top wall region 78 by punching.

  Next, the top wall side protrusion 56 and the leg side protrusion 58 are provided by pressing at a predetermined position around the through-hole 54 and at both ends of the planned leg portions 70 and 72.

  Thereafter, the virtual lines 80, 82, 84, 86 are bent so that the side edges 38, 40 and the edges 46, 48 are rounded, and the top wall planned area 78 and the planned leg 70 are formed. , 72 are bent so as to have a curved shape, thereby forming a current collecting lead 34 as shown in FIG.

  In this embodiment, a gap is provided between the leg portion 50 and the leg portion 52, and the bottom wall portion is divided into two. However, the present invention is not limited to this aspect, and The part 50 and the leg part 52 may be connected to each other, and the leg part 50 and the leg part 52 may be integrated into one bottom wall part.

  Next, a method for manufacturing the battery 1 will be described.

  First, the current collector lead 34 manufactured as described above is prepared, and the electrode group 4 as described above is prepared.

  And after connecting a negative electrode collector to the other end side of the electrode group 4, the said electrode group 4 is accommodated in an exterior can. Then, the negative electrode current collector is resistance spot welded to the bottom wall of the outer can.

  Next, a predetermined amount of alkaline electrolyte is injected into the outer can 2. The alkaline electrolyte injected into the outer can 2 is held in the electrode group 4, and most of the alkaline electrolyte is held in the separator 10. This alkaline electrolyte advances an electrochemical reaction (charge / discharge reaction) during charge / discharge between the positive electrode 6 and the negative electrode 8. As the alkaline electrolyte, an alkaline electrolyte containing at least one of KOH, NaOH, and LiOH as a solute is preferably used.

  Next, the positive electrode current collector 28 is placed on one end side of the electrode group 4, and the current collector lead 34 is further placed on the positive electrode current collector 28. In this state, the sealing body 14 is disposed through the insulating gasket 18 in the upper end opening of the outer can 4.

  Here, in the current collecting lead 34, the top wall side protruding portion 56 protrudes from the curved apex portion 36 a of the top wall portion 36, and the leg side protruding portion 58 is between the leg portions 50 and 52. It protrudes from the apex portion 53 of the curved shape virtually imagined. Therefore, as apparent from FIG. 6A schematically showing the current collecting lead 34 before deformation, the top wall side protrusion 56 and the sealing body 14 are in contact with each other, and the leg side protrusion 58 and the positive electrode are in contact with each other. The current collector 28 is in contact.

  Thereafter, a current is applied while pressing between the positive electrode terminal 22 and the negative electrode terminal of the battery 1 to perform resistance spot welding. As a result, the positive electrode connecting edge 32 of the positive electrode 6 and the positive electrode current collector 28 are welded, and the positive electrode current collector 28 and the legs 50 and 52 of the current collector lead 34 are welded. The wall portion 36 and the lid plate 16 of the sealing body 14 are welded.

  Then, the opening 3 of the outer can 2 is sealed by caulking the opening edge 17 of the outer can 2.

  Here, in the positive electrode current collector 28 as described above, the protrusions (burrs) at the edge portions of the slits 30 are arranged so as to abut on the positive electrode connection end edge portion 32 of the positive electrode 6. When resistance spot welding is performed, the welding current concentrates on the protrusion (burr) part, and a part of the protrusion (burr) part melts to become a welding point, and the positive electrode current collector 28 and the positive electrode 6 The positive connection end edge 32 is connected. In addition, in the leg portions 50 and 52 of the current collecting lead 34, the leg side protrusion 58 is in contact with the positive electrode current collector 28. When resistance spot welding is performed, the welding current concentrates on the leg-side projection 58, and a part of the leg-side projection 58 melts, and the legs 50, 52 of the current collecting lead 34 and the positive electrode A current collector 28 is connected. Further, in the top wall portion 36 of the current collecting lead 34, the top wall side protrusion 56 is in contact with the sealing body 14. When resistance spot welding is performed, the welding current concentrates on the top wall projection 56 and a part of the top wall projection 56 melts to form the top wall 36 of the current collecting lead 34 and the sealing body. 14 is connected.

  Here, if the top wall side protrusion 56 does not protrude beyond the curved apex portion 36a, the top wall side protrusion 56 does not contact the sealing body 14, and the leg side protuberance 58 has a curved apex portion. If it does not protrude from 53, the leg-side protrusion 58 does not contact the positive electrode current collector 28, and it becomes difficult to concentrate the welding current, and a good weld cannot be obtained. Therefore, the top wall side protruding portion 56 is protruded from the apex portion 36 a of the top wall portion 36, and the leg portion side protruding portion 58 is protruded from the apex portion 53 imaginary between the leg portion 50 and the leg portion 52. It is important to keep it in a stable state.

  As described above, the positive electrode 6 and the positive electrode terminal 22 are electrically connected via the positive electrode current collector 28, the current collector lead 34, and the lid plate 16, and the battery 1 is formed.

  In the resistance spot welding and the caulking process as described above, a compressive stress is applied to the battery 1 in a direction along the axis. Accordingly, compressive stress is also applied to the components constituting the battery 1 such as the electrode group 4, the positive electrode current collector 28, and the current collector lead 34. Here, when the current collecting lead 34 receives compressive stress in a direction in which the top wall portion 36 and the leg portions 50 and 52 approach each other (the arrow B direction extending in the direction of arrow A in FIG. 4), the current collecting lead 34 The portion 36 and the legs 50 and 52 are deformed and crushed in a direction approaching. As shown in FIG. 6A, the current collecting lead 34 according to the present invention has a curved shape in advance because the top wall portion 36 and the leg portions 50 and 52 are in the process of being crushed. As shown in b), the top wall 36 and the legs 50 and 52 are deformed and flattened. That is, the occurrence of deformation such that the central portion of the top wall portion 36 and the leg portions 50 and 52 bends like a conventional bow is suppressed. As a result, the shear stress on the welded portion is reduced, and it is difficult for the weld to come off, and the occurrence of poor welding can be suppressed. Therefore, according to the present invention, since the energization path can be maintained thick, the internal resistance of the battery can be reduced, and the high rate discharge characteristics of the battery can be improved. In addition, since the generation of cracks in the current collecting lead portion is suppressed, variation in resistance value among the batteries is suppressed. As a result, the stability of the quality of the obtained battery is improved.

  Before the current collecting lead 34 of the present invention is crushed, the top wall portion 36 and the leg portions 50 and 52 are curved as shown in FIG. Then, in the current collecting lead 34 of the present invention after being crushed, as shown in FIG. 6B, the top wall portion 36 and the leg portions 50 and 52 are flattened, and the leg portions 50 and 52 in the top wall portion 36 are flattened. And the inner surfaces of the leg portions 50 and 52 facing the top wall 36 extend substantially in parallel with each other. That is, the current collecting lead 34 of the present invention in the completed battery is not deformed so that the central portion bends like a bow, but as shown in FIG. 6B, the top wall portion 36 and the leg portion 50 are formed. , 52 are flattened.

  Here, in recent years, various devices have been miniaturized, and discharge at a high rate is required even for small devices. Under these circumstances, small batteries such as AA type (corresponding to R6 type, AA type) and AAA type (corresponding to R03 type, AA type) used for small devices are also at a higher rate. Discharge is required.

  However, in these small batteries, the current collector leads must be downsized compared to large batteries of D type (equivalent to R20 type, single type 1) or C type (equivalent to R14 type, single type 2). I must. As the current collector lead becomes smaller, the flexibility of the current collector lead decreases, so that when the compressive stress is applied in the axial direction of the battery, the current collector lead does not deform sufficiently and directly on the current collector. Stress is transmitted to. If it does so, a positive electrode electrical power collector will deform | transform and it will become easy to generate | occur | produce a short circuit by pressing an electrode group. Further, in a small battery, since the number of turns of the electrode group is small, the strength of the electrode group itself in the axial direction is also low. For this reason, in a small battery using a current collector lead that is simply miniaturized in order to obtain excellent high rate discharge characteristics, a short circuit due to deformation of the positive electrode current collector is more likely to occur than in a large battery. ing.

  For this situation, it is possible to improve the flexibility of the current collector lead by examining the thickness of the current collector lead and eliminating the corners of the side walls. confirmed. However, in such a countermeasure, when the amount of crushing of the current collecting lead is increased, the load is moved in the vertical direction by lowering the sealing body while the edge portion of the current collecting lead is in contact with the positive current collecting plate or the sealing plate. Since a load is applied, a deformation occurs such that the central part bends like a bow. As a result, the shear stress to the welded part increases, so that there is a problem that a defect in welding failure occurs with a high probability. .

  In the present invention, since the shape of the current collecting lead is a curved shape in which the portion facing the positive electrode current collector and the portion facing the sealing body protrude outward, even if compressive stress is applied to the current collecting lead, Can be prevented from deforming like a bow. Therefore, it is particularly effective for suppressing the occurrence of poor welding of a small battery excellent in high rate discharge characteristics, specifically, a battery having a diameter of 18 mm or less.

  Moreover, in the procedure of the manufacturing method of the battery 1 described above, the electrode group 4 and the positive electrode current collector 28 were welded after the electrode group 4 was accommodated in the outer can 2, but is not limited to this mode. The positive electrode current collector 28 may be welded to the electrode group 4 in advance.

[Example]
(1) Battery manufacturing

  Example 1

  A positive electrode 6, a negative electrode 8, and a separator 10 used for a general nickel metal hydride secondary battery were prepared. Each of the positive electrode 6, the negative electrode 8, and the separator 10 has a strip shape. With the separator 10 interposed between the prepared positive electrode 6 and negative electrode 8, it was wound in a spiral shape to form an AA size electrode group 4. At the time of winding, the positive electrode 6 and the negative electrode 8 are arranged so as to be slightly shifted from each other in the direction along the axial direction of the electrode group 4, and a separator is provided at a predetermined position between the positive electrode 6 and the negative electrode 8. 10 was placed and the winding operation was performed in this state to obtain a cylindrical electrode group 4. The obtained electrode group 4 is in a state in which the positive electrode connection edge 32 of the positive electrode 6 protrudes from the adjacent negative electrode 8 through the separator 10 on one end side of the electrode group 4. On the other end side, the negative electrode connecting edge of the negative electrode 8 is in a state of protruding from the adjacent positive electrode 6 with the separator 10 interposed therebetween.

  Next, a negative electrode current collector for AA size having a disk shape and comprising a thin plate of Ni-plated steel was prepared. This negative electrode current collector was welded to the negative electrode connection edge of the electrode group 4.

  Next, as shown in FIG. 2, the whole has a decagonal shape, and includes a circular central through hole 29 in the center and six slits 30 extending radially so as to surround the central through hole 29. A positive electrode current collector 28 for AA size was prepared. The positive electrode current collector 28 is made of a Ni-plated steel plate in which a thin steel plate is plated with Ni. The thickness of the positive electrode current collector 28 is 0.30 mm.

  Next, a Ni-plated steel sheet in which Ni plating was applied to a thin steel plate was prepared. The thickness of this Ni-plated steel sheet is 0.25 mm. Then, by punching the Ni-plated steel sheet, an approximately H-shaped current collecting lead intermediate product 62 as shown in FIG. 5 was manufactured. A through hole 54 was formed in the center of the intermediate product 62, and a top wall side protrusion 56 and a leg side protrusion 58 were formed at predetermined positions by pressing. And the current collection lead 34 as shown in FIG. 3 was formed by bending the part of the virtual lines 80, 82, 84, 86. Here, the top wall portion planned region 78 and the leg portion planned regions 70 and 72 are bent into curved shapes that protrude 0.4 mm toward the outside, respectively, and the top wall portion 36 and the legs 50 and 52 are formed. A curved shape was adopted.

  Next, the electrode group 4 to which the negative electrode current collector was welded was accommodated in a bottomed cylindrical outer can 4. And the inner surface of the bottom wall of the armored can 4 and the negative electrode collector were welded.

  Next, the positive electrode current collector 28 was placed on the electrode group 4, and the current collector lead 34 was further placed on the positive electrode current collector 28. In this state, the sealing body 14 was disposed at the upper end opening of the outer can 4 via the insulating gasket 18 to manufacture an intermediate product of the battery. And the intermediate product of this battery was set to the resistance spot welding machine, the compressive stress was applied to the axial direction of the battery, and resistance spot welding was performed. Thereafter, the opening edge 17 of the outer can 2 was caulked to seal the opening 3 of the outer can 2 to manufacture the battery 1. Note that compressive stress is also applied in the axial direction of the battery during caulking.

  Here, the height dimension of the space where the current collecting leads 34 are arranged has a design value of 1.5 mm and a tolerance of ± 0.4 mm. The total height of the current collecting lead was 1.9 mm. And it pressurized until the total height of a current collection lead became 1.1 mm by resistance spot welding and caulking.

  Comparative Example 1

  Example 1 except that when the current collecting lead is formed, the planned top wall region and the planned leg region are not processed into a curved shape, and the current collecting lead is a flat top wall and leg. A battery was manufactured in the same manner as described above.

(2) Evaluation of Battery The batteries of Example 1 and Comparative Example 1 were cut so that a longitudinal section could be observed, and a sample for observing the section was prepared.

  With respect to the obtained sample, the shape of the current collecting lead was observed.

  When the shape of the top wall part and the leg part was flat, it was determined to be good. For the battery of this good determination, a circle is indicated in the column of the shape determination in Table 1.

  On the other hand, when the shape of the top wall part and the leg part was bent like a bow, it was determined to be defective. About the battery of this defective determination, x mark was described in the column of the shape determination of Table 1.

  Moreover, about the obtained sample, the presence or absence of the crack of a weld part, etc. was confirmed.

  When there was no crack in the welded part, the welded part was judged to be good and a good judgment was made. For the battery of this good determination, a circle is indicated in the column of welded portion determination in Table 1.

  On the other hand, when the crack existed in the welded part, it was judged that the welded part was defective, and the defect was determined. About the battery of this defect determination, x mark was described in the column of the welding part determination of Table 1.

(3) Consideration (i) After the current collecting lead of Comparative Example 1 is assembled in the battery, that is, after being pressurized, the top wall and the leg are bent like a bow, and the shape determination becomes poor. ing. Moreover, the welded part is cracked and the welded part judgment is also poor. When the shape of the top wall portion and the leg portion of the current collecting lead before being incorporated into the battery is flat as in Comparative Example 1, when the compressive stress is applied during resistance spot welding or caulking, these top wall portion and Legs tend to bend like bows. As a result, a large shear stress acts on the weld and cracks occur in the weld. As described above, when a crack occurs in the welded portion, the internal resistance of the battery is increased, the high rate discharge characteristic is deteriorated, and the stability of the battery quality is hindered.

(Ii) After the current collecting lead of Example 1 is assembled into the battery, that is, after being pressurized, the top wall portion and the leg portion have a flat shape, and the shape determination is good. In addition, no crack is generated in the welded portion, and the welded portion is also judged as good. As in Example 1, when the shape of the top wall portion and the leg portion of the current collecting lead before being incorporated into the battery is a curved shape protruding outward, when subjected to compressive stress during resistance spot welding or caulking, These top walls and legs are flat. For this reason, it is hard to produce stress in the peeling direction or the shearing direction in the welded portion. As a result, no crack is generated in the welded portion, and the increase in the internal resistance of the battery is suppressed, and the high-rate discharge characteristics of the battery can be improved. In addition, the quality of the battery is stabilized.

(Iii) From the above, it can be said that bending the current collecting lead in advance as in the present invention is effective in suppressing the occurrence of poor welding and improving the high rate discharge characteristics of the battery.

  The present invention is not limited to the above-described embodiment and examples, and various modifications are possible. For example, the type of battery is not limited to a nickel-metal hydride secondary battery, but nickel-cadmium. A secondary battery, a lithium ion secondary battery, etc. may be sufficient.

DESCRIPTION OF SYMBOLS 1 Nickel metal hydride secondary battery 2 Exterior can 4 Electrode group 6 Positive electrode 8 Negative electrode 10 Separator 14 Sealing body 18 Insulating gasket 22 Positive electrode terminal 28 Positive electrode current collector 32 Positive electrode connection edge 34 Current collecting lead

Claims (3)

A rectangular top wall portion, a pair of side wall portions extending from both side edges of the top wall portion, and a bottom wall portion connected to the side wall portion and positioned at a position facing the top wall portion,
The top wall has a curved shape protruding outward and has a plurality of top wall side protrusions,
The bottom wall portion has a curved shape protruding outward, and has a plurality of bottom wall side protrusion portions,
The top wall side protruding portion protrudes from the apex portion of the curved shape in the top wall portion,
The bottom wall-side protruding part protrudes from the apex part of the curved shape in the bottom wall part,
Current collector lead. A current collecting lead preparing step for preparing the current collecting lead according to claim 1;
An electrode group preparation step of preparing an electrode group in which a positive electrode and a negative electrode are overlapped via a separator and wound in a spiral shape;
A setting step in which the electrode group is housed in an outer can, the current collecting lead is placed on the positive electrode current collector of the electrode group, and a sealing body including a positive electrode terminal is placed on the current collecting lead; ,
A welding step of resistance spot welding the positive electrode current collector, the current collector lead and the sealing body;
Caulking and attaching the sealing body to the outer can, and a sealing step of sealing the outer can;
With
The method of manufacturing an alkaline secondary battery, wherein the current collecting lead is compressed and the top wall portion and the bottom wall portion are flattened by the welding step and the sealing step. An alkaline secondary battery manufactured by the method for manufacturing an alkaline secondary battery according to claim 2,
A cylindrical outer can with a bottom including a negative electrode terminal;
A sealing body including a positive electrode terminal and sealing an upper end opening of the outer can;
A positive electrode and a negative electrode are overlapped via a separator and wound in a spiral shape, and a cylindrical electrode group housed together with an alkaline electrolyte in the outer can,
A positive electrode current collector connected to an edge portion of the positive electrode protruding from one end surface of the electrode group;
A current collecting lead for connecting the positive electrode current collector and the sealing body,
The current collecting lead is positioned at a position facing the top wall portion, connected to the side wall portion, a pair of side wall portions extending from both side edges of the top wall portion, and a top wall portion having a rectangular shape in plan view. Including a bottom wall,
The top wall portion is flat and connected to the sealing body by a plurality of welds,
The bottom wall portion is flat and connected to the positive electrode current collector by a plurality of welds.
Alkaline secondary battery.

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