JP2015220118A - Alkali secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alkali secondary battery arranged so that the internal short circuit caused in the event of contact between an outer can and a positive electrode can be prevented.SOLUTION: A nickel hydrogen secondary battery 1 comprises: an outer can 2; a sealing material 14 sealing an opening of the outer can 2, to which a positive electrode terminal 22 is electrically connected; an alkaline electrolyte; an electrode group 4 composed of a positive electrode 6 and a negative electrode 8 wound in spiral form via separators 10 and enclosed in the outer can 2 together with the alkaline electrolyte; and a positive electrode collector 28 interposed between the sealing material 14 and the electrode group 4 and serving to cause an electric current to pass through the positive electrode terminal 22 and the positive electrode 6. The positive electrode collector 28 has a connection disk 27. The electrode group 4 has an upper end edge portion 32 opposed to the connection disk 27 and composed of an end edge portion of the positive electrode 6 protruding toward the side of the connection disk. Upper end edge portions 32 of portions of the positive electrode 6 except its outermost peripheral portion are resistance-welded to the connection disk 27. The outermost peripheral end edge portion Z of the outermost peripheral portion of the positive electrode 6 is covered with an insulative material 50.

Description

  The present invention relates to an alkaline secondary battery.

  A cylindrical nickel-hydrogen secondary battery is known as a kind of alkaline secondary battery. In this nickel-metal hydride secondary battery, an electrode group formed by spirally winding a positive electrode and a negative electrode that are stacked with a separator sandwiched between them is placed on a bottomed cylindrical outer can that includes a negative electrode terminal. It is accommodated together with the electrolytic solution, and the upper end opening of the outer can is formed by sealing with a lid plate provided with a positive electrode terminal. In recent years, such nickel metal hydride secondary batteries have been widely used as power sources for mobile phones, electric tools, electric vehicles, and the like.

  Here, in a battery used for an electric tool or the like, it is desired to have a good high rate discharge characteristic so that a large current can be output efficiently. In order to obtain such good high rate discharge characteristics, it is necessary to reduce the internal resistance of the battery as much as possible. Therefore, in order to reduce the internal resistance of the battery, measures are taken to electrically connect the positive electrode and the positive electrode terminal with a positive electrode current collector interposed therebetween. As a battery including such a positive electrode current collector, for example, a battery disclosed in Patent Document 1 is known.

  In a battery represented by Patent Document 1, a positive electrode current collector including a disk-shaped connection disk and a strip-shaped positive electrode lead formed integrally with the connection disk is used. In such a positive electrode current collector, the connection disk is bonded to the protruding end edge of the positive electrode protruding from one end side of the electrode group, and the positive electrode lead is bonded to the lid plate. Since the lid plate described above is electrically connected to the positive electrode terminal, the positive electrode and the positive electrode terminal are electrically connected via the positive electrode current collector and the lid plate. As described above, since the connection disk of the positive electrode current collector and the protruding edge of the protruding positive electrode are in contact with each other in a relatively wide range, the internal resistance of the battery is low, and thus high rate discharge characteristics are good. It becomes a state.

  Here, in order to prevent the connection disk of the positive electrode current collector from coming into contact with the inner wall of the outer can including the negative electrode terminal, the outer diameter dimension of the connection disk is usually smaller than the outer diameter dimension of the electrode group. The projecting edge portion of the portion other than the outermost peripheral portion of the positive electrode, that is, the projecting end edge portion (hereinafter referred to as the inner end) located on the radially inner side of the electrode group from the projecting end edge portion of the outermost peripheral portion of the positive electrode Only the edge).

  The connection between the connection disk of the positive electrode current collector and the protruding end edge of the positive electrode is performed by resistance welding. Specifically, the connection disc of the positive electrode current collector is placed on the inner end edge portion of the protruding edge portion of the positive electrode projecting from one end side of the electrode group and along the axial direction of the electrode group. In this state, current is applied between the connecting disk and the positive electrode to perform welding.

JP-A 63-4562

  In the electrode group as described above, the inner edge of the positive electrode is fixed because it is welded to the connection disk of the positive electrode current collector. However, the protruding edge part excluding the inner edge part of the positive electrode, that is, the protruding edge part of the outermost peripheral part of the positive electrode (hereinafter referred to as the outermost peripheral edge part) is welded to the connection disk of the positive electrode current collector. Because it is not, it is a little easier to move than the inner edge. For this reason, when some force is applied to the outermost peripheral edge of the positive electrode and the outermost peripheral edge is deformed and comes into contact with the outer can, an internal short circuit may occur. In addition, when the connecting disc of the positive electrode current collector is pressed with a strong force during the resistance welding described above, a force is applied in the axial direction of the electrode group, and the electrode group is slightly deformed radially outward. To do. When such deformation occurs, the outermost peripheral edge of the positive electrode slightly falls toward the radially outer side of the electrode group. When the electrode group in this state is inserted into the outer can, the outermost peripheral edge of the positive electrode may come into contact with the inner wall of the outer can, which may cause an internal short circuit of the battery.

  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 can prevent an internal short circuit caused by contact between an outer can and a positive electrode. is there.

  In order to achieve the above object, according to the present invention, a bottomed cylindrical outer can including a negative terminal and a sealing body in which a positive terminal is electrically connected and the upper end opening of the outer can is sealed. And a positive electrode and a negative electrode laminated via a separator and wound in a spiral shape, and a cylindrical electrode group housed together with an alkaline electrolyte in the outer can, and between the sealing body and the electrode group And a positive electrode current collector that energizes the positive electrode terminal and the positive electrode, the positive electrode current collector has a disk-shaped connection disk, and the electrode group includes the connection circle The edge of the positive electrode facing the plate has a protruding edge that protrudes toward the connection disk, and the protruding edge of the portion other than the outermost periphery of the positive electrode is resistance welded to the connection disk And the projecting edge portion of the outermost peripheral portion of the positive electrode is covered with an insulating material. There is provided.

  Preferably, the protruding edge portion of the portion other than the outermost peripheral portion of the positive electrode is configured such that both side surfaces are covered with an insulating material.

  Moreover, it is preferable that the protruding end edge portion includes a strip-shaped metal thin plate extending along the entire region.

  In the alkaline secondary battery according to the present invention, since the protruding end edge portion of the outermost peripheral portion of the positive electrode is covered with the insulating material, even if the protruding end edge portion of the outermost peripheral portion of the positive electrode comes into contact with the outer can, The occurrence of a short circuit can be prevented.

It is sectional drawing which fractured | ruptured and showed the cylindrical nickel-hydrogen secondary battery which concerns on this invention partially. It is sectional drawing which expanded and showed the inside of the circle | round | yen II of FIG. It is the top view shown roughly in the state which expand | deployed the positive electrode integrated in the nickel-hydrogen secondary battery of FIG.

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, for example, a case where the present invention is applied to an AA size cylindrical nickel-hydrogen secondary battery (hereinafter referred to as a battery) 1 shown in FIG. 1 will be described as an example. To do.

  As shown in FIG. 1, 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 the bottom wall 38 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).

  The opening 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 packing 18 is disposed on the outer periphery of the cover plate 16 so as to surround the cover plate 16. The insulating packing 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 packing 18 cooperate with each other to seal the opening of the outer can 2. Here, the lid plate 16 has a central through hole 16a at the center, and a valve body 20 in which rubber and a metal plate are bonded to each other so as to close the central through hole 16a on the outer surface of the lid plate 16. Has been placed. 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. A compression coil spring 24 that urges the valve body 20 toward the cover plate 16 is accommodated in the positive terminal 22. The positive electrode terminal 22 has a gas vent hole (not shown).

  Normally, the central through hole 16a is hermetically closed by the valve body 20. On the other hand, when gas is generated in the outer can 2 and its internal pressure increases, the compression coil spring 24 is compressed by the internal pressure through the valve body 20 and the central through hole 16a is opened. As a result, from the inside of the outer can 2 Gas is released to the outside through the central through hole 16 a and the gas vent hole of the positive electrode terminal 22. That is, the central through hole 16a, the valve body 20 and the vent hole of the positive terminal 22 form a safety valve for the battery.

  The electrode group 4 includes a strip-like positive electrode 6, a negative electrode 8, and a separator 10, and a charge / discharge reaction proceeds between the positive electrode 6 and the negative electrode 8 through an alkaline electrolyte impregnated in the positive electrode 6, the negative electrode 8, and the separator 10. Let

  The electrode group 4 is wound in a spiral shape with the separator 10 sandwiched between the positive electrode 6 and the negative electrode 8, and has a cylindrical shape.

  The negative electrode 8 has a conductive negative electrode core 40 having a strip shape, and a negative electrode mixture 42 is held on the negative electrode core 40 (see FIG. 2).

  The negative electrode core body 40 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. The negative electrode mixture 42 is not only filled in the through holes of the negative electrode core body 40 but also held in layers on both surfaces of the negative electrode core body 40.

  The negative electrode mixture 42 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 hydrogen storage alloy particles and the conductive material to each other and at the same time bind the negative electrode mixture 42 to the negative electrode core 40. Here, as the conductive material and the binder, those generally used in nickel-hydrogen secondary batteries are preferably used.

  As shown in FIG. 1, the lower end edge 34 of the negative electrode 8 protrudes from the adjacent positive electrode 6 on the lower end side of the electrode group 4. That is, the lower end edge 34 of the negative electrode 8 protrudes spirally on the lower end side of the electrode group 4.

Moreover, the negative electrode 8 can be manufactured as follows, for example.
First, a slurry of the negative electrode mixture 42 is prepared by kneading a hydrogen storage alloy powder composed of hydrogen storage alloy particles, a conductive material, a binder, and water. The obtained slurry of the negative electrode mixture 42 is applied to the negative electrode core body 40 and dried. After drying, the negative electrode core body 40 to which the negative electrode mixture 42 containing hydrogen storage alloy particles and the like is attached is subjected to roll rolling and cutting, whereby the negative electrode 8 is obtained.

Next, the positive electrode 6 will be described.
As shown in FIG. 2, the positive electrode 6 includes a conductive positive electrode base material 44 having a porous structure and a large number of holes, and a positive electrode mixture held in the holes and on the surface of the positive electrode base material 44. And a thin metal plate 46 attached to the end portion of the positive electrode base material 44.

  As the positive electrode substrate 44, 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 agent, a binder, and the like.
As the metal thin plate 46, for example, a nickel ribbon or the like can be used.

  As is apparent from FIG. 1, the upper end edge (protruding end edge) 32 of the positive electrode 6 protrudes from the adjacent negative electrode 8 on the upper end side of the electrode group 4. That is, the upper edge portion 32 of the positive electrode 6 protrudes in a spiral shape on the upper end side of the electrode group 4.

  Here, the upper edge portion 32 of the positive electrode 6 includes a compression portion 44a formed by compressing the upper portion of the positive electrode base material 44 in the thickness direction (the direction indicated by the arrow A in FIG. 2), as shown in FIG. And a thin metal plate 46 joined to the compression portion 44a. In addition, in this compression part 4a, in order to make it easy to weld, it is preferable to remove a positive mix beforehand.

  In the compression part 44a described above, as is apparent from FIG. 2, a step having a predetermined length X is generated between the first surface 44b of the positive electrode base material 44 and the joint surface 44c of the compression part 44a. Further, as shown in FIG. 3, the compression portion 44 a extends over the entire area in the longitudinal direction of the positive electrode 6 indicated by the arrow B, and in a direction along the vertical direction (width direction) of the positive electrode 6 indicated by the arrow C. It has a width of a predetermined length Y.

  The metal thin plate 46 is a strip having a rectangular cross section, has a thickness dimension equal to the above-described step length X, a longitudinal dimension equal to the longitudinal length of the positive electrode 6, and a widthwise dimension. The dimension is set to be equal to the length Y of the width of the compression portion 44a. As a result, the thin metal plate 46 matches the above-described step.

  When such a thin metal plate 46 is joined to the compression portion 44a, the upper end edge portion 32 of the positive electrode 6 is reinforced, which is preferable.

  In the present invention, of the upper end edge portion 32 of the positive electrode 6, a portion corresponding to a range corresponding to one turn of the outermost periphery of the positive electrode 6 indicated by reference symbol Z in FIG. 3 (hereinafter referred to as the outermost peripheral edge portion Z). ) Is covered with an insulating material 50. At the outermost peripheral edge Z, as shown in FIG. 2, the entire top surface 32 a and both side surfaces (first surface 32 b and second surface 32 c) of the upper edge 32 of the positive electrode 6 are covered with an insulating material 50. ing. On the other hand, as shown in FIG. 3, a portion excluding the outermost peripheral edge portion Z, that is, a portion corresponding to a range located on the radially inner side of the electrode group 4 with respect to the outermost peripheral edge portion Z (hereinafter referred to as an inner end). About the edge part W), the insulating material 50 does not cover the whole. At the inner edge W, at least the top surface 32a of the upper edge 32 is exposed. In FIG. 3, reference numeral 52 indicates the winding start end portion of the positive electrode 6, and reference numeral 54 indicates the winding end end portion of the positive electrode 6. When the positive electrode 6 is incorporated into the electrode group 4, the winding start end portion 52 side is located on the radially inner side of the electrode group 4, and the winding end end portion 54 side is located on the radially outer side of the electrode group 4.

  Here, the first surface 32 b and the second surface 32 c of the upper end edge portion 32 can be partially covered with the insulating material 50. Further, as shown in FIGS. 2 and 3, the insulating material 50 can also cover a range located below the lower end of the compression portion 44 a. Such an embodiment is preferable because the insulating property of the positive electrode 6 is improved and an internal short circuit with the adjacent negative electrode 8 can be further prevented.

  Here, the above-described insulating material 50 is not particularly limited, and examples thereof include a polypropylene insulating protective tape.

The positive electrode 6 can be manufactured as follows, for example.
First, a positive electrode mixture slurry containing a positive electrode active material powder made of nickel hydroxide 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 the positive electrode mixture containing nickel hydroxide particles and the like is roll-rolled and then cut to obtain a rectangular intermediate product of the positive electrode. Thereafter, the intermediate product is compressed in the thickness direction over the entire area of one end edge in the longitudinal direction to form a compressed portion 44a. Prior to the formation of the compression portion 44a, it is preferable to apply ultrasonic vibration to a portion where the compression portion 44a is to be formed to remove the positive electrode mixture retained in that portion.

  Thereafter, the above-described nickel ribbon as the metal thin plate 46 is welded to the compression portion 44 a to form the upper end edge portion 32. Next, an insulating protective tape made of polypropylene as the insulating material 50 is affixed to the entire portion corresponding to the outermost peripheral edge portion Z of the upper end edge portion 32. Thereby, the positive electrode 6 is obtained. In addition, although it is possible to affix an insulating protective tape also to the inner edge part W, in this case, an insulating protective tape is applied to a part of the first surface 32b and the second surface 32c in the inner edge part W. The top surface 32a is exposed.

  Next, as the separator 10, for example, a non-woven fabric made of polyamide fiber or a non-woven fabric made of polyolefin fiber such as polyethylene or polypropylene can be used.

  Here, as apparent from FIG. 1, the separator 10 is also projected to one end side (upper side in FIG. 1) and the other end side (lower side in FIG. 1) of the electrode group 4. The protruding length of the separator 10 is about half of the protruding lengths of the upper edge 32 of the positive electrode 6 and the lower edge 34 of the negative electrode 8. Thereby, generation | occurrence | production of the short circuit by the contact of the positive electrode 6 and the negative electrode 8 which mutually adjoin can be prevented effectively. In addition, as the separator 10, the strip | belt-shaped body of a size which can ensure protrusion length as mentioned above is prepared.

  The positive electrode 24 and the negative electrode 26 manufactured as described above are spirally wound with the separator 28 interposed therebetween, whereby the electrode group 22 is formed. Specifically, during winding, the positive electrode 6 and the negative electrode 8 are arranged 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, as described above. A 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 as shown in FIG. 1 is obtained. As an aspect of the obtained electrode group 4, on one end side (upper side in FIG. 1) of the electrode group 4, the upper end edge portion 32 of the positive electrode 6 protrudes from the adjacent negative electrode 8, and the other end side of the electrode group 4 In (lower side in FIG. 1), the lower edge 34 of the negative electrode 8 protrudes from the adjacent positive electrode 6. Further, the separator 10 also has an upper end edge 32 of the positive electrode 6 and a lower end edge of the negative electrode 8 on each of one end side (upper side in FIG. 1) of the electrode group 4 and the other end side (lower side in FIG. 1) of the electrode group 4. It protrudes by a length that is about half of the protruding length of the portion 34. In addition, in the upper end edge part 32 of the positive electrode 6, the entire outermost peripheral edge part Z is covered with the insulating material 50, and at least the top surface 32a is exposed at the inner edge part W.

  In the electrode group 4 as described above, the positive electrode current collector 28 is connected to one end side (upper side in FIG. 1), and the negative electrode current collector 36 is connected to the other end side (lower side in FIG. 1). Yes.

Here, first, the negative electrode current collector 36 will be described.
The negative electrode current collector 36 is made of a metal disk. The outer diameter dimension of the negative electrode current collector 36 is substantially equal to the outer diameter dimension of the electrode group 4. As shown in FIG. 1, the negative electrode current collector 36 is, for example, subjected to resistance welding over the entire region of the lower end edge 34 of the negative electrode 8 projecting in a spiral shape on the other end side of the electrode group 4. Connected.

Next, the positive electrode current collector 28 will be described.
The positive electrode current collector 28 is entirely made of a conductive material, and includes a disk-shaped connection disk 27 and a positive electrode lead 26 formed integrally with the connection disk 27.
The connection disk 27 has an outer diameter smaller than the outer diameter of the electrode group 4, and as shown in FIG. 1, the connection disk 27 is formed on the inner edge W of the upper edge 32 protruding in a spiral shape. It is a disc with a size that only matches. The connection disk 27 is electrically connected only to the inner edge W of the upper edge 32 of the positive electrode 6 by, for example, resistance welding. That is, the connection disk 27 is not in contact with the outermost peripheral edge portion Z.

  As described above, the electrode group 4 to which the positive electrode current collector 28 and the negative electrode current collector 36 are attached is accommodated in the outer can 2. The negative electrode current collector 36 and the bottom wall of the outer can 2 are resistance welded, and the negative electrode 8 and the negative electrode terminal 38 are electrically connected. Since the outermost peripheral portion of the electrode group 4 is not covered with the separator 10 and is formed by a part of the negative electrode 8 (outermost peripheral portion), the negative electrode 8 is also in contact with the inner peripheral wall of the outer can 2. ing. That is, the negative electrode 8 is electrically connected to the outer can 2 (negative electrode terminal 38) also at the outermost peripheral portion.

  On the other hand, the tip of the positive electrode lead 26 extending from the connection disk 27 is resistance-welded to the lid plate 16 of the sealing body 14 and is electrically connected. Thereby, the positive electrode 6 and the positive electrode terminal 22 are electrically connected.

  In this manner, a predetermined amount of alkaline electrolyte is continuously injected into the outer can 2 containing the electrode group 4. Thereafter, the outer can 2 is sealed by the sealing body 14, whereby the battery 1 according to the present invention is obtained. The obtained battery 1 is subjected to an initial activation process and is in a usable state.

  As described above, in the battery 1 according to the present invention obtained as described above, the upper edge 32 of the positive electrode 6 protrudes, and only the inner edge W of the upper edge 32 is the positive electrode collector. The outer peripheral edge Z that is welded to the connection disk 27 of the electric body 28 and is not welded to the connection disk 27 is covered with an insulating material 50. For this reason, even if some force is applied to the outermost peripheral edge Z of the upper end edge 32 of the positive electrode 6, and the outermost peripheral edge Z of the upper end edge 32 comes into contact with the inner wall of the outer can 2, The operation can effectively prevent the occurrence of an internal short circuit.

  The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the type of battery is not limited to a nickel-hydrogen secondary battery, and a nickel-cadmium secondary battery. Or a lithium ion secondary battery.

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 Insulation packing 22 Positive electrode terminal 26 Positive electrode lead 27 Connection disk 28 Positive electrode collector 32 Upper end edge part 50 Insulation material (insulation protection tape) )
W Inner edge Z Outermost edge

Claims (3)

A cylindrical outer can with a bottom including a negative electrode terminal;
A sealing body that is electrically connected to the positive electrode terminal and seals the upper end opening of the outer can;
A positive electrode and a negative electrode are laminated 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 interposed between the sealing body and the electrode group and energizing the positive electrode terminal and the positive electrode;
The positive electrode current collector has a disk-shaped connection disk,
The electrode group has a protruding edge portion in which an edge portion of the positive electrode facing the connection disk protrudes toward the connection disk, and the protruding edge portion of a portion other than the outermost peripheral portion of the positive electrode Is an alkaline secondary battery, wherein the protruding end edge portion of the outermost peripheral portion of the positive electrode is covered with an insulating material.   2. The alkaline secondary battery according to claim 1, wherein both sides of the protruding edge portion of the positive electrode other than the outermost peripheral portion are covered with an insulating material.   The alkaline secondary battery according to claim 1, wherein the protruding end edge includes a strip-shaped metal thin plate extending along the entire region.

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