JP2018045994A - Cylindrical alkaline secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cylindrical alkaline secondary battery which is superior in high-rate discharge characteristic, and less in the occurrence of internal short circuit.SOLUTION: A nickel hydrogen secondary battery 1 comprises: an exterior can 2; a sealing body 14 including a positive electrode terminal 22, and serving to seal an opening of the exterior can 2; an electrode group 4 arranged by putting together and spirally winding a positive electrode 6 and a negative electrode 8 with a separator 10 arranged therebetween, and encased in the exterior can 2 together with an alkali electrolyte solution; a positive electrode current collector 28 connected to a positive electrode connecting edge portion 32 protruding from one end face of the electrode group 4; and a collector lead 34 which connects the positive electrode current collector 28 to the sealing body 14. When a material constituting the collector lead 34 is defined as "a" material, and a material constituting the positive electrode current collector 28 is defined as "b" material, a deformation resistance A of the "a" material, and a deformation resistance B of the "b" material satisfy the relation represented by: A<B.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a cylindrical alkaline secondary battery.

  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 ribbon made of a metal thin plate is welded to a predetermined position of the positive electrode current collector. Further, the other end of the positive electrode ribbon 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 ribbon 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 ribbon is accommodated in the outer can so as to bend between the sealing body and the electrode group. For this reason, a comparatively thin thing is used for a positive electrode ribbon so that it may be bent easily.

  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 the above-described thin and long strip-like positive electrode ribbon is used, the specific resistance of the positive electrode ribbon is high, and the positive electrode ribbon causes the internal resistance of the battery to increase.

  Therefore, various studies 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 measure using a current collecting lead that is thicker and shorter than a conventional positive electrode ribbon is taken. Specifically, when the battery of Patent Document 1 is assembled, a current collecting lead having a predetermined shape as shown in FIG. 1 of Patent Document 1 is welded onto the positive electrode current collector. Next, the sealing body is disposed at the opening of the outer can through an insulating gasket, and the battery is sealed by caulking the opening edge of the outer can inward to assemble the battery. At the time of sealing, the current collecting lead and the sealing body are in contact with each other. Thereafter, the current collector lead and the sealing body of the positive electrode are resistance spot welded by energizing between the positive electrode terminal and the negative electrode terminal of the battery.

  Since the battery of Patent Document 1 can weld the current collecting lead and the sealing body after sealing the outer can, it is necessary to weld the current collecting lead and the sealing body before sealing the outer can. Disappears. This makes it possible to easily attach the sealing body to the opening of the outer can even if the current collecting lead is short. Thus, if the current collecting lead is shortened, the energization path can be shortened, so that the internal resistance of the battery can be reduced. Further, since the battery of Patent Document 1 does not need to bend the current collecting lead in the outer can, it is possible to use the current collecting lead having a large thickness. Thus, if the thickness of the current collecting lead is increased, the energization path can be increased, and this can also reduce the internal resistance of the battery.

  Thus, since the battery of patent document 1 becomes low in internal resistance of a battery compared with the conventional battery, it is excellent in the high rate discharge characteristic.

Japanese Patent No. 3547931

  By the way, when the upper end opening edge of the outer can is caulked and the sealing body is attached to the outer can, or when the current collector, the current collecting lead and the sealing body are resistance spot welded, the battery has an axial direction. Compressive stress is applied. When such compressive stress is applied, the current collector is deformed and presses the electrode group. If it does so, in a battery, there exists a possibility that the edge part of the positive electrode of a electrode group or a negative electrode may bend | fold, and an internal short circuit will be caused.

  The present invention has been made based on the above circumstances, and an object of the present invention is to provide an alkaline secondary battery that is excellent in high-rate discharge characteristics and has few occurrences of internal short circuits. .

  To achieve the above object, according to the present invention, a bottomed cylindrical outer can 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, A negative electrode is overlapped via a separator and wound in a spiral shape, and is a cylindrical electrode group housed together with an alkaline electrolyte in the outer can, and an end of the positive electrode protruding from one end surface of the electrode group A current collector connected to an edge; and a current collector lead that connects the current collector and the sealing body; and a material constituting the current collector lead is a material, and the current collector is Provided is a cylindrical alkaline secondary battery in which the relationship between the deformation resistance A of the material a and the deformation resistance B of the material b satisfies the relationship A <B when the material constituting the material is material b. The

  In order to satisfy the relationship of A <B, it is preferable that the thickness of the b material is larger than the thickness of the a material.

  In order to satisfy the relationship of A <B, it is preferable that the hardness of the material b is higher than the hardness of the material a.

  In order to satisfy the relationship of A <B, the material a is preferably pure Ni and the material b is preferably Ni-plated steel.

  More preferably, the current collecting lead includes a rectangular top wall portion connected to the sealing body, a side wall portion extending from a predetermined side edge of the top wall portion toward the current collector, and the side wall. A leg portion provided at a leading edge of the portion and connected to the current collector, wherein a length of the side wall portion in a direction from the top wall portion to the leg portion is the sealing body and the current collector. The length is approximately the same as that between the body.

  Moreover, it is preferable that the said side wall part is set as the structure containing the deformation | transformation acceleration | stimulation part which accelerates | stimulates local deformation, when a compressive stress is received in the direction in which the said collector and the said sealing body approach.

  Moreover, it is preferable that the current collector has a protrusion that protrudes toward the electrode group.

  Further, it is preferable that the protrusion is a burr provided at an edge of a notch formed on the plate surface of the current collector.

  ADVANTAGE OF THE INVENTION According to this invention, the cylindrical alkaline secondary battery which is excellent in the high rate discharge characteristic and few generation | occurrence | production of an internal short circuit 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 top view which showed the current collection component which integrated the positive electrode current collector and the current collection lead. FIG. 3 is a plan view schematically showing a slit-type positive electrode current collector. It is the side view which looked at the slit-type positive electrode collector in the arrow C direction in FIG. It is the top view which showed roughly the positive electrode connection edge part combined with a slit-type positive electrode collector. FIG. 3 is a plan view schematically showing a porous positive electrode current collector. It is the top view which showed roughly the positive electrode connection edge part combined with a porous positive electrode collector. It is the top view which showed the analysis result of the electric potential distribution obtained about the slit type positive electrode electrical power collector. It is the top view which showed the analysis result of the electric potential distribution obtained about the positive electrode connection edge part combined with the slit type positive electrode collector. It is the top view which showed the analysis result of the electric potential distribution obtained about the porous positive electrode collector. It is the top view which showed the analysis result of the electric potential distribution obtained about the positive electrode connection edge part combined with the porous positive electrode collector.

Hereinafter, an alkaline secondary battery 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. Further, the size of the positive electrode current collector 28 is smaller than the outer diameter size of the electrode group 4 and is large enough to cover the 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 substantially rectangular top wall portion 36 connected to the sealing body 14, and a pair of side wall portions extending from predetermined side edges 38 and 40 of the top wall portion 36. 42, 44 and leg portions 50, 52 extending from end edges 46, 48 of the side wall portions 42, 44 opposite to the top wall portion 36 and connected to the positive electrode current collector 28.

  The top wall portion 36 is provided with a circular through hole 54 at the center. The through hole 54 communicates with the central through hole 19 of the cover plate 16 when the current collecting lead 34 is connected to the sealing body 14. In addition, around the through hole 54, four protrusions 56 serving as welds are provided.

  The side wall portions 42 and 44 extend from both side edges 38 and 40 of the top wall portion 36, and the cross-sectional shape thereof is substantially straight as shown in FIG. Here, the length of the side wall portions 42 and 44 in the vertical direction in FIG. 4, that is, the length in the direction extending from the top wall portion 36 to the leg portions 50 and 52, is the sealing body 14 and the positive electrode current collector 28. It is set to be almost the same as the length between. Thereby, an energization path can be shortened and it contributes to reduction of internal resistance of a battery.

  The leg portions 50 and 52 extend from the end edges 46 and 48 of the side wall portions 42 and 44, and 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. These extending portions 50a, 50b, 52a, 52b are provided with protruding portions 58 protruding toward the positive electrode current collector 28 (see FIG. 4). This protrusion 58 also becomes a welded portion.

  Here, the protruding portion 56 and the protruding portion 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 protrusions 58 are provided on the legs 50 and 52.

  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 ribbon. 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, protrusions 56 and 58 are provided by pressing at a predetermined position around the through hole 54 and at predetermined positions on both ends of the planned leg portions 70 and 72.

  Thereafter, the portions of the virtual lines 80, 82, 84, 86 are bent to form the current collecting leads 34 as shown in FIG.

  Next, the procedure for assembling the battery 1 will be described.

  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. At this time, the current collecting lead 34 and the sealing body 14 are in contact with each other.

  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 welded portion, and the positive electrode current collector 28 and the positive electrode 6 The positive connection end edge 32 is connected. Further, in the leg portions 50 and 52 of the current collecting lead 34, the protruding portion 58 is disposed so as to contact the positive electrode current collector 28. When resistance spot welding is performed, the welding current concentrates on the portion of the protrusion 58, and a portion of the protrusion 58 is melted, so that the legs 50 and 52 of the current collecting lead 34 and the positive electrode current collector 28 are connected. Connected. Further, on the top wall portion 36 of the current collecting lead 34, the protruding portion 56 is disposed so as to contact the lid plate 16 of the sealing body 14. When resistance spot welding is performed, the welding current concentrates on the portion of the protruding portion 56, and a portion of the protruding portion 56 is melted to connect the top wall portion 36 of the current collecting lead 34 and the cover plate 16. .

  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.

  Here, main energization paths (paths through which current flows) between the current collecting lead 34 and the positive electrode current collector 28 and between the positive electrode current collector 28 and the positive electrode connecting edge 32 of the electrode group 4. Will be described.

  First, the positive electrode current collector 28 is simplified to assume a circular model as a whole, and the positive electrode connection edge 32 of the electrode group 4 is also simplified to assume a concentric model.

  The modeled positive electrode current collector 28 is shown in FIG. In FIG. 7, the positive electrode current collector 28 is schematically shown to have only a half shape. The positive electrode current collector 28 has a circular shape as a whole, a central through hole 29 is provided at the center, and six slits 30 extending radially from the central through hole 29 are provided. ing. These slits 30 extend to the outer peripheral edge of the positive electrode current collector 28. Then, as shown in FIG. 8 which is a side view of the positive electrode current collector 28 as viewed in the direction of arrow C in FIG. 7, the longitudinal edge 66 of each slit 30 has a lower side (electrode group 4) in FIG. A protrusion (burr) 31 is provided so as to protrude in the direction of. The positive electrode current collector 28 is a slit type.

  In FIG. 7, it is schematically shown at which position of the positive electrode current collector 28 the position where the protrusion 58 of the current collecting lead 34 is welded (hereinafter referred to as the lead welding portion 68).

  In FIG. 7, the main energization paths are represented by thick arrows. As shown in FIG. 7, the main energization path is such that a current flows through the edge 66 of the slit 30 closest to the lead weld 68.

  Next, the modeled positive electrode connection edge 32 is shown in FIG. In FIG. 9, the positive electrode connection edge portion 32 is schematically shown to have only a half shape. As is clear from FIG. 9, the positive electrode connection end edge portion 32 is disposed concentrically.

  In FIG. 9, the positional relationship between the slit 30 of the positive electrode current collector 28 and the positive electrode connection edge 32 of the electrode group 4 is schematically shown. In FIG. 9, an area indicated by reference numeral 64 is a slit area where the slit 30 of the positive electrode current collector 28 is positioned. As shown in FIG. 9, the portion 67 corresponding to the edge 66 in the slit region 64 and the positive electrode connection end edge 32 intersect with each other at relatively many points from the radially inner side to the outer side of the electrode group 4. Yes. A protrusion (burr) 31 is formed on the edge 66 of the slit 30, and a portion where the protrusion (burr) 31 and the positive electrode connecting edge portion 32 are in contact with each other is a welded portion. For this reason, the positive electrode current collector 28 having the slits 30 including the protrusions (burrs) 31, that is, the slit-type positive electrode current collector 28 forms welds at many locations of the positive electrode connection edge portion 32. In FIG. 9, the main energization paths are represented by thick arrows. As shown in FIG. 9, the energization path from the positive electrode current collector 28 to the positive electrode connection end portion 32 extends from a number of intersecting portions in the slit 30 and the positive electrode connection end portion 32. That is, since the positive electrode current collector 28 and the positive electrode connection end edge portion 32 are in contact with each other at a relatively large number of points, the current input to and output from the positive electrode 6 flows in a relatively wide range, and the flow is , Will be relatively even.

  As described above, when the current flows relatively uniformly in a relatively wide range, the electric resistance value becomes low. As a result, the internal resistance value of the battery is kept low, and excellent high rate charge / discharge characteristics are exhibited.

  Here, for comparison, for example, main energization paths in the case of using a porous positive electrode current collector 88 as shown in FIG. 10 will be described. The porous positive electrode current collector 88 includes a large number of circular through holes 92 dispersed in place of the slits 30, and each through hole 92 has protrusions (burrs) formed along the periphery thereof. ing.

  FIG. 10 is a plan view corresponding to FIG. 7, and is a plan view schematically showing where the lead welded portion 68 is positioned in the porous positive electrode current collector 88. In FIG. 10, the main energization paths are represented by thick arrows. As shown in FIG. 10, the main energization path is such that a current flows through the portion of the through hole 92 closest to the lead welded portion 68.

  Next, FIG. 11 is a plan view corresponding to FIG. 9, and schematically shows the positional relationship between the through hole 92 of the porous positive electrode current collector 88 and the positive electrode connection edge 32 of the electrode group 4. It is the shown top view. In FIG. 11, a region indicated by reference numeral 94 is a through hole region where the through hole 92 is positioned. Here, a portion where the protrusion (burr) formed on the periphery of the through hole 92 and the positive electrode connection end edge portion 32 are in contact with each other is a welded portion. As shown in FIG. 11, several of the through-hole regions 94 are positioned on the positive electrode connection edge 32 positioned on the outer peripheral side of the electrode group 4, and Several are positioned on the positive electrode connection edge 32 located on the inner peripheral side of the electrode group 4. In FIG. 11, main energization paths are represented by thick arrows. As shown in FIG. 11, the energization path from the positive electrode current collector 88 to the positive electrode connection end edge 32 extends from a portion where the peripheral edge of the through hole 92 and the positive electrode connection end edge 32 intersect. In the case of the porous positive electrode current collector 88, the number of locations where one through-hole region 94 intersects the positive electrode connection end edge 32 is the same as that of one slit region 64 in the slit type positive electrode current collector 28. The number is smaller than the number of points intersecting the edge 32. That is, there are relatively few places where the positive electrode current collector 88 and the positive electrode connection edge portion 32 are in contact with each other. For this reason, the current inputted to and outputted from the positive electrode 6 flows in a relatively narrow range, and the flow is relatively biased.

  Thus, when the current flows in a relatively narrow range, the electrical resistance value increases. As a result, in the battery employing the porous positive electrode current collector 88, the internal resistance value cannot be suppressed lower than when the slit positive electrode current collector 28 is employed.

  As described above, when the slit-type positive electrode current collector 28 is used, the internal resistance value of the battery can be suppressed lower than that of the porous positive electrode current collector 88, and the high rate charge / discharge characteristics of the battery can be improved. ,preferable.

  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 (in the direction of arrow B extending in the direction of arrow A in FIG. 4), as shown in FIG. The portions 42 and 45 are bent sideways, and the top wall portion 36 and the leg portions 50 and 52 are deformed in a direction approaching. If the current collecting lead 34 is easily deformed in this way, it is possible to suppress deformation of the positive electrode current collector 28 and to suppress pressing of the electrode group 4. As a result, occurrence of an internal short circuit can be suppressed.

  In the present invention, the deformation resistance A of the current collecting lead 34 is set smaller than the deformation resistance B of the positive electrode current collector 28 in order to make the current collecting lead 34 easier to deform than the positive electrode current collector 28. That is, the relationship of A <B is satisfied. In this way, by balancing the deformation resistance between the current collecting lead 34 and the positive electrode current collector 28, the current collecting lead 34 and the positive electrode current collector in the process of caulking and resistance spot welding as described above. Even if compressive stress is applied to 28, the current collector lead 34 is preferentially deformed so that the positive electrode current collector 28 does not press the electrode group 4 more than necessary. Thereby, generation | occurrence | production of a short circuit can be suppressed.

  Here, the deformation resistance means a resistance force at the time of deformation, that is, a degree of force necessary for the deformation. If the material is the same, the deformation resistance depends on, for example, the thickness of the material. The thicker the thickness, the higher the deformation resistance. In addition, if the material is different, the deformation resistance depends on the characteristics of the material, for example, the hardness of the material, and the higher the hardness, the higher the deformation resistance.

  Preferably, the material constituting the positive electrode current collector 28 is made thicker than the material constituting the current collecting lead 34.

  Preferably, the hardness of the material constituting the positive electrode current collector 28 is made larger than the hardness of the material constituting the current collector lead 34.

  Preferably, pure Ni is used as a material constituting the current collector lead 34, and a steel plate having a carbon content of 0.01% by mass or more and 0.1% by mass or less as a material constituting the positive electrode current collector 28. Ni-plated steel with Ni plating is used. Pure Ni refers to high purity nickel having a purity of 99.5% or more.

  Preferably, the material constituting the positive electrode current collector 28 is an extremely low carbon steel having a carbon content of 0.001 mass% or more and 0.005 mass% or less as a material constituting the current collector lead 34. As described above, a Ni-plated steel obtained by performing Ni plating on a steel sheet having a carbon content of 0.01% by mass or more and 0.1% by mass or less is used.

  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 such a situation, the present invention preferentially deforms the current collector lead by balancing the deformation resistance between the positive electrode current collector and the current collector lead, and suppresses deformation of the positive electrode current collector. In this way, it is possible to avoid pressure on the electrode group, and in particular, a small battery excellent in high-rate discharge characteristics, specifically a battery having a diameter of 19 mm or less, more preferably a short circuit of a battery having a diameter of 18 mm or less. It is effective in suppressing the occurrence of

  Here, it is preferable that the side wall portions 42 and 44 include a deformation promoting portion that promotes deformation so that the current collecting lead 34 is more easily deformed when subjected to compressive stress. As an aspect which includes a deformation | transformation promotion part in the side wall parts 42 and 44, the aspect which provides a curved shape part in the side wall parts 42 and 44, or processes the side wall parts 42 and 44 itself into a curved shape is mentioned, for example. If the side wall portions 42 and 44 are curved in advance, the side wall portions 42 and 44 swell laterally when subjected to compressive stress, and the current collecting leads 34 are easily crushed in the compression direction. In order to obtain such an aspect, it is preferable to bend the side wall portions 74 and 76 so as to bend in the step of bending the intermediate product 62 of the current collecting lead 34.

  In addition, as a shape of a deformation | transformation acceleration | stimulation part, it is not limited to the above curved shape, You may employ | adopt other shapes which can accelerate | stimulate a deformation | transformation, such as a bending shape.

  In the assembly procedure of the battery 1 described above, the electrode group 4 is accommodated in the outer can 2 and the positive electrode current collector 28 is welded. However, the present invention is not limited to this mode. The electric body 28 may be welded.

[Example]
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 obtained by applying Ni plating to a steel thin plate having a carbon content of 0.04% by mass. The thickness of the positive electrode current collector 28 is 0.30 mm. The thickness value is shown in Table 1 as the thickness of the current collector.

  Next, a Ni-plated steel sheet was prepared by applying Ni plating to a steel sheet having a carbon content of 0.04 mass%. 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 projections 56 and 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. The value of the thickness of the Ni-plated steel sheet used for manufacturing the current collecting lead 34 is shown in Table 1 as the thickness of the current collecting lead.

  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, a pressure sensor was provided at the upper end of the electrode group 4 so that the compressive stress applied to the electrode group 4 could be measured. The signal line of this pressure sensor was led out through a hole opened at a predetermined position of the outer can 4 and connected to a measuring device for compressive stress. Then, the positive electrode current collector 28 was placed on the pressure sensor, and further, the current collector lead 34 was 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, and an intermediate product of a battery for stress measurement for measuring the compressive stress applied to the electrode group 4 was manufactured. The intermediate product of the battery for stress measurement was set in a resistance spot welder, and the same pressure as that during welding was applied in the axial direction of the battery for stress measurement without flowing a welding current. 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.

  The compressive stress applied to the electrode group 4 was measured through the pressurizing operation and the caulking process with the resistance spot welding machine. The maximum value among the measured values is shown in Table 1 as the maximum stress to the electrode group.

  For the positive electrode current collector 28 and the current collecting lead 34, a sample for resistance measurement was separately manufactured. Specifically, as shown in FIG. 6, a current collector lead 34 is placed on the positive electrode current collector 28, resistance spot welding is performed, and the positive electrode current collector 28 and the current collector lead 34 are integrated. Part 90 was manufactured. With respect to the current collecting component 90, the resistance value between the positive electrode current collector 28 and the current collecting lead 34 was measured. The resistance value is shown in Table 1 as the resistance value of the current collecting component.

Comparative Example 1
Instead of the current collecting lead, a conventional positive electrode ribbon made of Ni foil with a thickness of 0.01 mm was prepared, and this positive electrode ribbon was welded to the positive electrode current collector to form a current collecting component. A battery intermediate product for stress measurement was manufactured in the same manner as in Example 1 except that the thickness was 0.25 mm. Then, as in Example 1, the resistance value of the current collecting component and the maximum stress on the electrode group were measured.

Comparative Example 2
Except that the thickness of the positive electrode current collector was 0.25 mm and the thickness of the current collector lead was 0.30 mm, an intermediate product and a battery for stress measurement were collected in the same manner as in Example 1. Electric parts were manufactured. Then, as in Example 1, the resistance value of the current collecting component and the maximum stress on the electrode group were measured.

Comparative Example 3
Except that the thickness of the current collecting lead was 0.30 mm, an intermediate product of a battery for stress measurement and current collecting parts were produced in the same manner as in Example 1. Then, as in Example 1, the resistance value of the current collecting component and the maximum stress on the electrode group were measured.

Example 2
Stress measurement was carried out in the same manner as in Example 1 except that the thickness of the Ni-plated steel sheet of the positive electrode current collector was 0.40 mm and the thickness of the Ni-plated steel sheet of the current collector lead was 0.30 mm. Manufactured intermediate products and current collector parts for batteries. Then, as in Example 1, the resistance value of the current collecting component and the maximum stress on the electrode group were measured. Table 2 shows the current collector thickness, current collector lead thickness, current collector material, current collector lead material, current collector resistance, and maximum stress on the electrode group.

Example 3
The thickness of the positive electrode current collector was 0.40 mm, and as a material for the current collector lead, instead of a Ni-plated steel sheet in which Ni plating was applied to a steel thin plate having a carbon content of 0.04% by mass, An Ni-plated ultra-low carbon steel sheet in which a Ni-plated thin steel sheet having a carbon content of 0.001% by mass was prepared, and the thickness of this Ni-plated ultra-low carbon steel sheet was set to 0.00. A battery intermediate product and a current collecting part for stress measurement were manufactured in the same manner as in Example 1 except that the thickness was 30 mm. Then, as in Example 1, the resistance value of the current collecting component and the maximum stress on the electrode group were measured. Table 2 shows the current collector thickness, current collector lead thickness, current collector material, current collector lead material, current collector resistance, and maximum stress on the electrode group.

Example 4
The thickness of the positive electrode current collector was 0.40 mm, a pure Ni thin plate was prepared instead of the Ni-plated steel plate as the material of the current collector lead, and the thickness of the pure Ni thin plate was 0 An intermediate product of a battery for stress measurement and a current collecting part were produced in the same manner as in Example 1 except that the thickness was 30 mm. Then, as in Example 1, the resistance value of the current collecting component and the maximum stress on the electrode group were measured. Table 2 shows the current collector thickness, current collector lead thickness, current collector material, current collector lead material, current collector resistance, and maximum stress on the electrode group.

  Here, when the resistance value of the current collecting component exceeds 0.5 mΩ, the internal resistance of the battery as a whole becomes high, and the high rate discharge characteristics of the obtained battery are considered to be equivalent to the conventional one. About such a battery,-mark was described in the column of the judgment of Table 1 as a conventional product.

  If the resistance value of the current collecting component is 0.5 mΩ or less, the internal resistance of the battery as a whole can be kept low, and the high rate discharge characteristics of the battery obtained are excellent. Further, when the resistance value of the current collecting component is 0.25 mΩ or less, the high rate discharge characteristics of the obtained battery are further improved.

On the other hand, when the maximum stress on the electrode group exceeds 30.0 kgf / mm ² , the positive electrode current collector is greatly deformed, and the degree of pressure on the electrode group is increased. As a result, it is considered that the occurrence of an internal short circuit due to the bending of the positive electrode or the negative electrode increases. If the maximum stress on the electrode group is 30.0 kgf / mm ² or less, the degree of pressure on the electrode group due to deformation of the positive electrode current collector is within an allowable range, and the occurrence of internal short circuit due to bending of the positive electrode or negative electrode is suppressed. It is thought that it is done. Further, if the maximum stress to the electrode group is 20.0 kgf / mm ² or less, deformation of the positive electrode current collector is preferably suppressed, and if the maximum stress to the electrode group is 15.0 kgf / mm ² or less, It is more preferable because deformation of the positive electrode current collector can be further suppressed.

Therefore, although the resistance value of the current collecting component is 0.5 mΩ or less, the battery having a maximum stress exceeding 30.0 kgf / mm ² is excellent in high rate discharge characteristics, but the positive current collector is deformed. Since it is considered that this is likely to occur, it was judged as defective. About the battery of this defective determination, x mark was described in the determination column of Table 1.

For a battery in which the resistance value of the current collecting component is 0.5 mΩ or less and the maximum stress to the electrode group is 30.0 kgf / mm ² or less, while obtaining excellent high rate discharge characteristics, The deformation was also judged to be good to the extent that deformation could be suppressed to some extent. For the battery of this good determination, a Δ mark was written in the determination column of Table 1.

For a battery in which the resistance value of the current collecting component is 0.5 mΩ or less and the maximum stress on the electrode group is 20.0 kgf / mm ² or less, while obtaining excellent high rate discharge characteristics, It was determined that the deformation was suppressed. For the battery judged as good, a circle is shown in the judgment column of Table 1.

For a battery in which the resistance value of the current collecting component is 0.25 mΩ or less and the maximum stress to the electrode group is 15.0 kgf / mm ² or less, excellent high rate discharge characteristics can be obtained, and the positive electrode current collector can be obtained. Since the deformation of the electric body was further suppressed and the occurrence of an internal short circuit of the battery could be further suppressed, the best judgment was made. The battery of this best judgment is marked with a mark in the judgment column of Table 1.

[analysis]

  Regarding the battery having the same configuration as the battery of Example 3, the positive electrode current collector included therein was modeled as a slit-type positive electrode current collector as shown in FIG. 7 and the positive electrode connection end of the electrode group included therein The edges were modeled concentrically as shown in FIG. 9, and the potential distribution and the electrical resistance value were analyzed when a constant voltage was applied to the positive terminal of the battery.

  Here, in the analysis, the dimensions of each part of the slit-type positive electrode current collector were set as follows.

  The diameter D of the positive electrode current collector 28 is 15.00 mm, the diameter d of the central through hole 29 is 3.00 mm, the length L of the slit 30 is 3.75 mm, and the width W of the slit 30 is 1.20 mm (FIG. 7). reference). Further, the thickness T1 of the positive electrode current collector 28 is 0.40 mm, the length of the protrusion (burr) (the protruding length from the lower surface of the positive electrode current collector) P is 0.35 mm, and the thickness T2 of the protrusion (burr). Was 0.20 mm (see FIG. 8).

  In the analysis of the potential distribution, the degree of potential drop was visualized. The analysis result of the potential distribution obtained for the slit-type positive electrode current collector 28 is shown in FIG. FIG. 13 shows the analysis result of the potential distribution obtained for the positive electrode connection edge 32 combined with the slit-type positive electrode current collector 28. In FIGS. 12 and 13, the degree of potential drop is represented by gray shades. The darker the gray, the greater the potential drop, and the lighter the gray, the smaller the potential drop. That is, the resistance value increases as the gray is darker and the potential drop is larger. The method of expressing the degree of potential drop is the same for the results shown in FIGS.

  In the analysis of the electric resistance value, the electric resistance value of the positive electrode current collector 28 was determined. As a result, the electrical resistance value of the slit-type positive electrode current collector 28 was 0.0313 mΩ. Moreover, the electrical resistance value of the portion where the slit-type positive electrode current collector 28 and the positive electrode connection end edge portion 32 were combined was 0.0884 mΩ.

  Further, in the embodiment in which the positive electrode current collector is changed from the slit-type positive electrode current collector 28 to the porous positive electrode current collector 88 shown in FIG. 10, the potential distribution analysis and the electrical resistance value analysis are performed in the same manner as described above. went. The analysis result of the potential distribution obtained for the porous positive electrode current collector 88 is shown in FIG. Further, FIG. 15 shows the analysis result of the potential distribution obtained for the positive electrode connection end portion 32 combined with the porous positive electrode current collector 88.

  Here, the dimensions of each part of the porous positive electrode current collector 88 are as follows: the positive electrode current collector 88 has a diameter D of 15.00 mm, the central through hole 29 has a diameter d of 3.00 mm, and the through hole 92 has a diameter dt of 1. 50 mm (see FIG. 10). The thickness T1 of the positive electrode current collector 88 is 0.40 mm, the length of the protrusion (burr) (the protruding length from the lower surface of the positive electrode current collector) P is 0.35 mm, and the thickness T2 of the protrusion (burr). Was 0.20 mm.

  As a result of the electrical resistance value, the electrical resistance value of the porous positive electrode current collector 88 was 0.0293 mΩ. Moreover, the electrical resistance value of the portion where the porous positive electrode current collector 88 and the positive electrode connection end edge portion 32 were combined was 0.1164 mΩ.

[Discussion]

(1) In Comparative Example 1 using a conventional positive electrode ribbon, the resistance value of the current collecting component is 0.95 mΩ, and Examples 1, 2, 3, 4 and Comparative Example 2 using current collecting leads are used. The value is higher than 3. That is, it can be seen that using the current collecting lead is superior in high rate discharge characteristics as compared with the conventional positive electrode ribbon. This is thought to be because the specific resistance of the current collector lead is low because the current path is shortened compared to the high specific resistance because the positive ribbon is thin and long. .

(2) As in Comparative Examples 2 and 3, when the thickness of the current collector is thinner than the thickness of the current collector lead, or when the thickness of the current collector is the same as the thickness of the current collector lead, go to the electrode group Is a high value exceeding 30.0 kgf / mm ² . Thus, when the thickness of the current collector is equal to or less than the thickness of the current collector lead, the deformation resistance of the current collector is smaller than the deformation resistance of the current collector lead, and when compressive stress is applied, The current collector is more easily deformed than the current collecting lead. For this reason, the current collector is deformed and a relatively large stress is applied to the electrode group. As a result, an internal short circuit is likely to occur.

(3) On the other hand, in Examples 1, 2, 3, and 4, in which the current collector is thicker than the current collector lead, the maximum stress on the electrode group is in Comparative Examples 2 and 3. It is a low value. Thus, when the thickness of the current collector is larger than the thickness of the current collector lead, the deformation resistance of the current collector lead is smaller than the deformation resistance of the current collector, and when compressive stress is applied, The current collecting lead is more easily deformed than the body. For this reason, the current collecting lead is preferentially deformed and deformation of the current collector is suppressed, so that the stress applied to the electrode group is relatively small. As a result, an internal short circuit is unlikely to occur.

(4) In Example 2, the material constituting the current collector is a thin plate made of Ni-plated steel, and the material constituting the current collector lead is also a thin plate made of the same Ni-plated steel. For this reason, the deformation resistance relating to the material is the same between the current collecting lead and the current collector.

(5) In Example 3, the material constituting the current collector is a thin plate made of Ni-plated steel, and the material constituting the current collector lead is Ni-plated ultra-low carbon obtained by applying Ni plating to a thin plate of ultra-low carbon steel It is made of steel. Ni-plated ultra-low carbon steel has a lower hardness than Ni-plated steel. For this reason, the deformation resistance related to the material of the current collector lead is smaller than the deformation resistance related to the material of the current collector, and when a compressive stress is applied, the current collector lead is more easily deformed than the current collector. For this reason, the current collecting lead is preferentially deformed and deformation of the current collector is suppressed, so that the stress applied to the electrode group is relatively small. This means that the value of the maximum stress of the electrode group in Example 3 is smaller than the value of the maximum stress to the electrode group in Example 2 in which the material of the current collector lead and the material of the current collector are the same. It is clear from Therefore, it is considered that Example 3 is less likely to cause an internal short circuit than Example 2.

(6) In Example 4, the material constituting the current collector is a thin plate made of Ni-plated steel, and the material constituting the current collector lead is a pure Ni thin plate. Pure Ni has a lower hardness than Ni-plated steel. For this reason, the deformation resistance related to the material of the current collector lead is smaller than the deformation resistance related to the material of the current collector, and when a compressive stress is applied, the current collector lead is more easily deformed than the current collector. For this reason, the current collecting lead is preferentially deformed and deformation of the current collector is suppressed, so that the stress applied to the electrode group is relatively small. This is because the value of the maximum stress of the electrode group in Example 4 is smaller than the value of the maximum stress to the electrode group in Example 2 in which the material of the current collector lead and the material of the current collector are the same. It is clear from Accordingly, it is considered that the internal short circuit is less likely to occur in the fourth embodiment than in the second embodiment.

(7) As described above, the current collector lead is made thinner than the current collector, or the current of the current collector lead is made lower than that of the current collector. Maintaining excellent high rate discharge characteristics by balancing the deformation resistance of the current collector lead and the current collector so that the deformation resistance of the current lead is smaller than that of the current collector. However, it is possible to suppress the occurrence of an internal short circuit.

(8) From FIG. 12, which shows the analysis result of the potential distribution of the slit-type positive electrode current collector 28, the degree of gray change between the lead welded portion 68 and the slit 30 is almost equal for each slit. Recognize. From this, it can be said that, in the slit-type positive electrode current collector 28, the potential drop amount is almost equal for each slit, and the flowing current and the electric resistance value are almost equal. Further, from FIG. 13 showing the analysis result of the potential distribution obtained for the positive electrode connection edge 32 combined with the slit-type positive electrode current collector 28, the current flows in many turns in the positive electrode connection edge 32. It can be seen that the current flows almost evenly in one lap. From this, it can be said that when the slit-type positive electrode current collector 28 is used, the electric resistance value can be reduced.

(9) From FIG. 14 showing the analysis result of the potential distribution of the porous positive electrode current collector 88, the degree of gray change between the lead welded portion 68 and the through hole 92 varies for each through hole. I understand. From this, it can be said that in the porous positive electrode current collector 88, the potential drop amount is not uniform for each through-hole, and the flowing current and the electric resistance value are not uniform. Further, from FIG. 15 showing the analysis result of the potential distribution obtained for the positive electrode connection edge portion 32 combined with the porous positive electrode current collector 88, the through hole 92 exists in the positive electrode connection edge portion 32. It can be seen that the current flows only in the laps, and the current does not flow evenly in one lap. From this, it can be said that when the porous positive electrode current collector 88 is used, the effect of reducing the electrical resistance value is smaller than when the slit type positive electrode current collector 28 is used.

(10) The electrical resistance value of the slit-type positive electrode current collector 28 is 0.0313 mΩ, the electrical resistance value of the porous positive electrode current collector 88 is 0.0293 mΩ, and the electric resistance in the positive electrode current collector portion The values were almost the same for the slit type and the porous type. On the other hand, the electrical resistance value of the combined portion of the positive electrode current collector and the positive electrode connection edge is 0.1164 mΩ in the case of the porous type, whereas it is 0.0884 mΩ in the case of the slit type, The electric resistance value is lower. Therefore, there is no large difference in electrical resistance value between the positive electrode current collector and the slit type and the porous type, but when the positive electrode current collector and the positive electrode connection edge are combined, the slit type positive electrode current collector is used. It can be seen that the use of the electric body 28 can reduce the electric resistance value by 24%, and is advantageous in the effect of reducing the electric resistance value, compared to the case where the porous positive electrode current collector 88 is used. Since the slit-type positive electrode current collector 28 can be in contact with the positive electrode connection edge 32 at many places, it is possible to flow a current relatively uniformly in a relatively wide range. As a result, the electric resistance value can be reduced, which contributes to improvement of the high rate charge / discharge characteristics of the battery. In the slit-type positive electrode current collector 28, it is considered that the electrical resistance value can be further reduced by making the length of the slit as long as possible so that it can come into contact with the positive electrode connection edge 32 at more places. It is done.

  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 or the like may be used.

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 (8)

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 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 current collector and the sealing body,
When the material constituting the current collector lead is a material and the material constituting the current collector is b material, the relationship between the deformation resistance A of the material a and the deformation resistance B of the material b is A A cylindrical alkaline secondary battery satisfying the relationship <B.   2. The cylindrical alkaline secondary battery according to claim 1, wherein the thickness of the b material is larger than the thickness of the a material in order to satisfy the relationship of A <B.   2. The cylindrical alkaline secondary battery according to claim 1, wherein the hardness of the b material is higher than the hardness of the a material in order to satisfy the relationship of A <B.   2. The cylindrical alkaline secondary battery according to claim 1, wherein in order to satisfy the relationship of A <B, the material a is pure Ni and the material b is Ni-plated steel. The current collecting lead includes a rectangular top wall portion connected to the sealing body, a side wall portion extending from a predetermined side edge of the top wall portion toward the current collector, and a leading edge of the side wall portion And a leg connected to the current collector, and
The length in the direction from the top wall portion to the leg portion in the side wall portion is substantially the same as the length between the sealing body and the current collector. Cylindrical alkaline secondary battery.   The cylindrical alkali secondary according to claim 5, wherein the side wall includes a deformation promoting portion that promotes local deformation when subjected to a compressive stress in a direction in which the current collector and the sealing body approach each other. battery.   The cylindrical alkaline secondary battery according to claim 1, wherein the current collector has a protrusion protruding toward the electrode group.   The cylindrical alkaline secondary battery according to claim 7, wherein the protrusion is a burr provided at an edge of a notch formed on a plate surface of the current collector.