JP6151106B2 - Nickel metal hydride storage battery - Google Patents

Description

  The present invention relates to a nickel-metal hydride storage battery, and more particularly to a cylindrical nickel-metal hydride storage battery.

  A cylindrical nickel-metal hydride storage battery is known as one of alkaline storage batteries. This nickel metal hydride storage battery is manufactured as follows, for example. First, a negative electrode provided with a negative electrode mixture layer containing a hydrogen storage alloy capable of occluding and releasing hydrogen as a negative electrode active material, and a positive electrode provided with a positive electrode mixture layer containing nickel hydroxide as a positive electrode active material The electrode group is formed by being wound in a spiral shape with a gap therebetween. The obtained electrode group is housed in a sealed state together with an alkaline electrolyte in a bottomed cylindrical container. In this way, a nickel metal hydride storage battery is obtained.

  Such nickel metal hydride storage batteries are used in various applications such as various portable devices and hybrid electric vehicles because they have higher capacity and better environmental safety than nickel cadmium storage batteries. It has become. As described above, it has been desired that the nickel-metal hydride storage battery has a long life so that it can be used stably for a longer period of time by finding various uses.

  One of the factors that adversely affect the life of the nickel-metal hydride storage battery is deterioration due to exposure of the hydrogen storage alloy to high temperatures. For example, when the battery is charged / discharged, the constituent members of each part of the battery generate electric resistance and generate heat, so that the temperature inside the battery becomes high. As described above, when the inside of the battery becomes high temperature, the corrosion reaction of the hydrogen storage alloy by the electrolytic solution further proceeds, so that the hydrogen storage alloy deteriorates. When the hydrogen storage alloy deteriorates, it becomes difficult to make the battery reaction proceed well, and the battery life is exhausted.

  From the viewpoint of extending the life of nickel-metal hydride storage batteries, it is known to take measures such as increasing the particle size of the hydrogen storage alloy particles in order to improve the corrosion resistance of the hydrogen storage alloy. In particular, in a cylindrical battery, when heat is generated during charging / discharging, the central portion of the battery is likely to accumulate heat and becomes relatively high temperature, so that the corrosion reaction of the hydrogen storage alloy in the central portion of the battery is likely to proceed. For this reason, increasing the particle size of the hydrogen storage alloy particles in the center of the battery is performed (for example, see Patent Document 1).

JP 2009-211970

  By the way, during the production of the electrode group, the positive electrode mixture layer on the radially inner surface of the electrode group in the positive electrode is compressed in the direction along the circumferential direction of the electrode group, as the positive electrode, the separator, and the negative electrode are wound. May rise locally toward the inner negative electrode. Thus, the raised portion of the positive electrode mixture layer becomes a protrusion having a relatively sharp tip. Such protrusions partially press the separator toward the negative electrode side. At this time, if the negative electrode contains hydrogen storage alloy particles having a large particle size, the unevenness on the surface of the negative electrode becomes large, so that the separator sandwiched between the negative electrode having a large surface unevenness and the positive electrode having protrusions breaks through. It becomes easy to be done. As a result, a short circuit failure of the battery may occur. As described above, when a hydrogen storage alloy having a large particle size is distributed in the center of the battery, that is, in the center of the electrode group, the center of the electrode group has a large curvature, so that the bending condition is tight. Short circuit failure is more likely to occur.

  In order to avoid such a short circuit failure, it is conceivable to reduce the particle size of the hydrogen storage alloy particles. However, if the particle size of the hydrogen storage alloy particles is reduced, the corrosion resistance of the hydrogen storage alloy with respect to the alkaline electrolyte is lowered, and the life of the battery is shortened. In other words, there is a problem that if the short circuit failure of the battery is suppressed, the life of the battery is sacrificed to some extent, and if the life of the battery is extended, the occurrence rate of the short circuit failure is increased.

  The present invention has been made based on the above circumstances, and an object of the present invention is to provide a nickel-metal hydride storage battery that can achieve both reduction in the occurrence rate of short-circuit failure of the battery and extension of the battery life. There is to do.

  In order to achieve the above object, according to the present invention, a container, a positive electrode and a negative electrode are wound in a state of sandwiching a separator, and the electrode is housed in a sealed state with an alkaline electrolyte in the container. A strip-shaped negative electrode core having a first surface located on the radially outer side of the electrode group and a second surface located on the radial inner side of the electrode group, and the negative electrode core The first negative electrode mixture layer formed on the first surface and the second negative electrode mixture layer formed on the second surface of the negative electrode core, and hydrogen contained in the first negative electrode mixture layer There is provided a nickel-metal hydride storage battery characterized in that the average particle size of the storage alloy particles is smaller than the average particle size of the hydrogen storage alloy particles contained in the second negative electrode mixture layer.

  According to this aspect, the particle size of the hydrogen storage alloy particles contained in the first negative electrode mixture layer formed on the radially outer surface of the electrode group in the negative electrode opposed to the radially inner surface of the electrode group in the positive electrode is Since the particle size of the hydrogen storage alloy particles contained in the second negative electrode mixture layer formed on the radially inner surface of the electrode group in the negative electrode is smaller than that of all the hydrogen storage alloy particles, one having a large particle size is used. Compared with the case, the problem that the raised portion of the positive electrode mixture layer of the positive electrode breaks through the separator is less likely to occur with the winding operation. And since the particle size of the hydrogen storage alloy particle contained in a 2nd negative mix layer is comparatively large, it is excellent in the corrosion resistance with respect to alkaline electrolyte. That is, in this aspect, hydrogen storage alloy particles having a relatively small particle size that contributes to prevention of the occurrence of short-circuiting are disposed in the portion where short-circuiting is likely to occur, and the other particle portions have relatively large particle sizes with excellent corrosion resistance. Larger hydrogen storage alloy particles are arranged. Thereby, generation | occurrence | production of the short circuit of a battery can be suppressed, and also the lifetime of a battery can be extended.

  The negative electrode core is preferably a non-porous metal sheet.

  In this embodiment, the hydrogen storage alloy particles contained in the first negative electrode mixture layer on the first surface side of the negative electrode core and the hydrogen storage alloy contained in the second negative electrode mixture layer on the second surface side of the negative electrode core. It is possible to reliably prevent the particles from being mixed with each other. As a result, there is no inconvenience that hydrogen storage alloy particles with a large particle size exist on the first surface side and hydrogen storage alloy particles with a small particle size exist on the second surface side, so the incidence of short circuit failure is more The battery life will be longer.

  Preferably, the negative electrode core is a metal sheet having a hole area ratio represented by a ratio of the area of through holes per unit area of the negative electrode core of 10% or less.

  In the case of this aspect, the negative electrode mixture to the negative electrode core is suppressed to some extent while mixing the hydrogen storage alloy particles on the first surface side of the negative electrode core and the hydrogen storage alloy particles on the second surface side of the negative electrode core to each other. The binding property of the layer is increased.

  The nickel-metal hydride storage battery according to the present invention is an excellent battery that can achieve both a reduction in the occurrence rate of short-circuit defects in the battery and a longer battery life.

It is the perspective view which fractured | ruptured and showed the nickel hydride storage battery which concerns on one Embodiment of this invention. It is sectional drawing which showed roughly the state which apply | coated the 1st negative mix paste on the 1st surface of the negative electrode core. It is sectional drawing which showed roughly the state which apply | coated 1st negative mix paste on the 1st surface of the negative electrode core, and apply | coated 2nd negative mix paste on the 2nd surface of the negative electrode core. It is the figure which showed schematically the aspect which rolls the laminated body obtained by laminating | stacking a negative electrode, a separator, and a positive electrode, and forms an electrode group.

Hereinafter, a nickel metal hydride storage battery (hereinafter simply referred to as a battery) 2 according to the present invention will be described with reference to the drawings.
The battery 2 is, for example, an AA size cylindrical battery shown in FIG.

  As shown in FIG. 1, the battery 2 includes an outer can 10 having a bottomed cylindrical shape with an open upper end. The outer can 10 has conductivity, and its bottom wall 35 functions as a negative electrode terminal. In the opening of the outer can 10, a disc-shaped cover plate 14 having conductivity and a ring-shaped insulating packing 12 surrounding the cover plate 14 are arranged. The insulating packing 12 caulks the opening edge 37 of the outer can 10. It is fixed to the opening edge 37 of the outer can 10 by processing. That is, the lid plate 14 and the insulating packing 12 cooperate with each other to airtightly close the opening of the outer can 10.

  Here, the cover plate 14 has a central through hole 16 in the center, and a rubber valve body 18 that closes the central through hole 16 is disposed on the outer surface of the cover plate 14. Further, a flanged cylindrical positive terminal 20 is fixed on the outer surface of the cover plate 14 so as to cover the valve body 18, and the positive terminal 20 presses the valve body 18 toward the cover plate 14. The positive electrode terminal 20 has a gas vent hole (not shown).

  Normally, the central through hole 16 is hermetically closed by the valve body 18. On the other hand, if gas is generated in the outer can 10 and its internal pressure increases, the valve body 18 is compressed by the internal pressure and opens the central through hole 16. As a result, the central through hole 16 and the positive electrode terminal 20 are opened from the outer can 10. Gas is released to the outside through the vent holes. That is, the central through hole 16, the valve body 18, and the positive electrode terminal 20 form a safety valve for the battery.

  An electrode group 22 is accommodated in the outer can 10. Each of the electrode groups 22 includes a strip-like positive electrode 24, a negative electrode 26, and a separator 28, which are wound in a spiral shape with the separator 28 sandwiched between the positive electrode 24 and the negative electrode 26. That is, the positive electrode 24 and the negative electrode 26 are overlapped via the separator 28. The outermost periphery of the electrode group 22 is formed by a part of the negative electrode 26 (the outermost periphery) and is in contact with the inner peripheral wall of the outer can 10. That is, the negative electrode 26 and the outer can 10 are electrically connected to each other.

  In the outer can 10, a positive electrode lead 30 is disposed between the electrode group 22 and the lid plate 14. Specifically, the positive electrode lead 30 has one end connected to the positive electrode 24 and the other end connected to the lid plate 14. Therefore, the positive electrode terminal 20 and the positive electrode 24 are electrically connected to each other via the positive electrode lead 30 and the cover plate 14. A circular upper insulating member 32 is disposed between the cover plate 14 and the electrode group 22, and the positive electrode lead 30 extends through a slit 39 provided in the insulating member 32. A circular lower insulating member 34 is also disposed between the electrode group 22 and the bottom of the outer can 10.

  Further, a predetermined amount of alkaline electrolyte (not shown) is injected into the outer can 10. The alkaline electrolyte is impregnated in the electrode group 22 to advance a charge / discharge reaction between the positive electrode 24 and the negative electrode 26. The type of the alkaline electrolyte is not particularly limited. For example, an aqueous sodium hydroxide solution can be used, and the concentration of the alkaline electrolyte can be an appropriate charge / discharge reaction. There is no particular limitation.

  Examples of the material of the separator 28 include a polyamide fiber nonwoven fabric and a polyolefin fiber nonwoven fabric such as polyethylene and polypropylene.

The positive electrode 24 includes a conductive positive electrode core having a porous structure and a positive electrode mixture held in the pores of the positive electrode core.
The positive electrode mixture includes positive electrode active material particles, a conductive material, and a binder for binding the positive electrode active material particles and the conductive material to the positive electrode core. Moreover, you may add the various additive for improving the characteristic of a positive electrode as needed. As this additive, for example, yttrium oxide is preferably used.

  The positive electrode active material particles are nickel hydroxide particles or higher order nickel hydroxide particles. In addition, these nickel hydroxide particles may be dissolved in cobalt, zinc, cadmium or the like, or the surface may be coated with a cobalt compound.

  As the conductive material, cobalt monoxide, metallic cobalt, or the like can be used.

  As the binder, for example, carboxymethylcellulose, methylcellulose, PTFE (polytetrafluoroethylene) dispersion, HPC (hydroxypropylcellulose) dispersion, and the like can be used.

The positive electrode 24 can be manufactured as follows, for example.
First, a positive electrode mixture paste including a positive electrode active material powder composed of positive electrode active material particles, a conductive material, a binder, and water is prepared. The obtained positive electrode mixture paste is filled in 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 dimension. Thereby, the positive electrode 24 having a predetermined shape holding the positive electrode mixture is produced.

Next, the negative electrode 26 will be described.
The negative electrode 26 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 metal sheet. The metal sheet is a non-porous metal sheet in which no through holes are provided or a metal sheet in which a large number of through holes are distributed for a reason to be described later, and has an opening rate of 10%. It is preferable to use the following metal sheet.
Here, the hole area ratio is represented by the ratio of the area of the through holes per unit area when the metal sheet is viewed in plan. Here, the hole part punched out by punching the metal sheet was used as a through hole, and the part other than the hole part, that is, the part where the metal sheet between the through hole and the through hole remained was used as the bone part. In this case, the lower the hole area ratio, the lower the proportion of the through-holes, and the larger the bone area.

  As the above-mentioned metal sheet, a nickel-plated steel sheet is preferably used. Moreover, as a metal sheet | seat with which the through-hole was distributed, the punching metal sheet of a nickel plating steel plate is used suitably, for example.

  Here, when a non-porous metal sheet is used as the negative electrode core, the negative electrode mixture is held in layers on both surfaces of the metal sheet. On the other hand, when a punching metal sheet is used as the negative electrode core, the negative electrode mixture is not only held in layers on both sides of the punching metal sheet, but also filled into the through holes.

  The negative electrode mixture includes hydrogen storage alloy particles capable of storing and releasing hydrogen as a negative electrode active material, and further includes a conductive material and a binder. This 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 to the negative electrode core. Here, a hydrophilic or hydrophobic polymer or the like can be used as the binder, and carbon black or graphite can be used as the conductive material.

  The hydrogen storage alloy particles may be any particles as long as they can store hydrogen generated electrochemically in an alkaline electrolyte during battery charging, and can easily release the stored hydrogen during discharge. Such a hydrogen storage alloy is not particularly limited. For example, a rare earth-Ni-based hydrogen storage alloy, a rare-earth-Mg-Ni-based hydrogen storage alloy, or the like can be used.

Here, the hydrogen storage alloy particles are obtained, for example, as follows.
First, various metal raw materials are prepared to obtain a desired hydrogen storage alloy. And after measuring each metal raw material so that it may become a predetermined composition, these are mixed and the mixture of a metal raw material is obtained. Next, the mixture is melted in, for example, an induction melting furnace, and then cooled to an ingot. The obtained ingot is subjected to heat treatment by heating for 5 to 24 hours in an inert gas atmosphere at 900 to 1200 ° C. Thereafter, the ingot cooled to room temperature is pulverized to obtain hydrogen storage alloy particles. The obtained hydrogen storage alloy particles are sieved to select the hydrogen storage alloy particles having a desired particle size.

  In the present invention, first hydrogen storage alloy particles having an average particle size of the first particle size and second hydrogen storage alloy particles having an average particle size of the second particle size are selected. Here, the first particle size is smaller than the second particle size. Preferably, the average particle size (first particle size) of the first hydrogen storage alloy particles is 20 μm to 60 μm, and the average particle size (second particle size) of the second hydrogen storage alloy particles is 70 μm to 120 μm. To do. Here, the average particle diameter in the present invention means a particle diameter at an integrated value of 50% in a particle size distribution obtained by a laser diffraction / scattering method.

Next, the negative electrode 26 can be manufactured as follows, for example.
First, a first negative electrode mixture paste is prepared by kneading a hydrogen storage alloy powder composed of first hydrogen storage alloy particles, a conductive material, a binder, and water. Further, a hydrogen storage alloy powder composed of the second hydrogen storage alloy particles, a conductive material, a binder and water are kneaded to prepare a second negative electrode mixture paste.

  The obtained 1st and 2nd negative mix paste is apply | coated to the prepared metal sheet | seat as follows.

  As shown in FIG. 2, the metal sheet 40 has a first surface 42 and a second surface 44 opposite to the first surface 42. First, the first surface of the metal sheet 40. For example, the first negative electrode mixture paste 46 is applied to 42 using a die coater as a coating device. At this time, the first negative electrode mixture paste 46 is applied so that the thickness is, for example, 0.25 mm to 0.35 mm. Here, FIG. 2 schematically shows a state in which the first negative electrode mixture paste 46 is applied to the first surface 42 of the metal sheet 40. Next, the second negative electrode mixture paste 48 is applied to the second surface 44 of the metal sheet 40. At this time, the second negative electrode mixture paste 48 is applied so that the thickness is, for example, 0.25 mm to 0.35 mm. Also in this case, the coating operation is performed using a die coater as a coating apparatus. Here, FIG. 3 schematically shows a state where the first and second negative electrode mixture pastes 46 and 48 are respectively applied to the first surface 42 and the second surface 44 of the metal sheet 40.

  The first and second negative electrode mixture pastes 46 and 48 applied to the metal sheet 40 as described above are then subjected to a drying process by a drying device, and the negative electrode mixture containing hydrogen storage alloy particles and the like. Become a layer. After drying, the metal sheet holding the negative electrode mixture layer is roll-rolled and then cut into a predetermined dimension. Thereby, the negative electrode 26 having a predetermined shape holding the negative electrode mixture is produced.

  Here, as apparent from FIG. 4, the negative electrode 26 includes a first negative electrode mixture layer 54 obtained by drying the first negative electrode mixture paste 46 on the first surface 42 side of the metal sheet 40, and a metal On the second surface 44 side of the sheet 40, there is a second negative electrode mixture layer 56 formed by drying the second negative electrode mixture paste 48. The particle size of the first hydrogen storage alloy particles 50 included in the first negative electrode mixture layer 54 is smaller than the particle size of the second hydrogen storage alloy particles 52 included in the second negative electrode mixture layer 56.

  In the negative electrode 26, as shown in FIG. 4, the side corresponding to the first surface 44 of the metal sheet 40 is the first surface 58, and the side corresponding to the second surface 44 of the metal sheet 40 is the second surface 60. To do. Here, in FIG. 4, the first hydrogen storage alloy particles 50 and the second hydrogen storage alloy particles 52 are not present only on the surface portions of the first negative electrode mixture layer 54 and the second negative electrode mixture layer 56. Although drawn, FIG. 4 schematically shows the configuration of the negative electrode 26, and the first hydrogen storage alloy particles 50 and the second hydrogen storage alloy particles 52 other than the surface portion are omitted. These particles are also present in the negative electrode mixture layer.

  When the non-porous metal sheet 40 is used as the metal sheet 40 as described above, the first negative electrode mixture paste 46 on the first surface 42 side and the second negative electrode mixture on the second surface 44 side are used by the metal sheet 40. It is isolated from the agent paste 48 and does not mix. Therefore, problems such as the presence of the second hydrogen storage alloy particles 52 on the first surface 42 side and the presence of the first hydrogen storage alloy particles 50 on the second surface 44 side are effectively prevented.

  In the present invention, a punching metal sheet having a large number of through holes can also be used as the metal sheet 40. In this case, since the negative electrode mixture layers 54 and 56 also enter the through holes, the binding property of the negative electrode mixture layers 54 and 56 to the metal sheet 40 is improved. By the way, when many through-holes exist in the metal sheet 40, the first negative electrode mixture paste 46 on the first surface 42 side and the second negative electrode mixture paste 48 on the second surface 44 side through these through holes. And touch. At this time, if the opening ratio of the punching metal sheet is defined to be 10% or less, the first negative electrode mixture paste 46 on the first surface 42 side and the second negative electrode mixture paste 48 on the second surface 44 side have through holes. The first negative electrode mixture paste 46 and the second negative electrode mixture paste 48 are mixed to form the surface of the first negative electrode mixture layer 54 (first surface 58). ) Side, the second hydrogen storage alloy particles 52 advance, and the first hydrogen storage alloy particles 50 advance to the surface (second surface 60) side of the second negative electrode mixture layer 56 on the second surface 60 side. There is no.

  On the other hand, when the hole area ratio of the punching metal sheet exceeds 10%, the range in which the first negative electrode mixture paste 46 and the second negative electrode mixture paste 48 are in contact with each other through the through holes is increased, and the mixing of these pastes is increased. Further, the second hydrogen storage alloy particles 52 are present on the surface (first surface 58) of the first negative electrode mixture layer 54, and the first hydrogen is present on the surface (second surface 60) of the second negative electrode mixture layer 56. There is a possibility that a problem that the occlusion alloy particles 50 are present may occur. Therefore, it is preferable to define the hole area ratio of the punching metal sheet to 10% or less. In addition, the lower limit value of the hole area ratio of the punching metal sheet may be a value exceeding 0%.

  The positive electrode 24 and the negative electrode 26 manufactured as described above are spirally wound with the separator 28 interposed therebetween, and are formed in the electrode group 22.

  At this time, in the negative electrode 26, the first negative electrode mixture layer 54 including the first hydrogen storage alloy particles 50 having a small particle size is positioned on the outside in the radial direction of the electrode group 22, and the second hydrogen storage alloy particles 52 having a large particle size. The second negative electrode material mixture layer 56 containing is disposed so as to be positioned on the radially inner side of the electrode group 22. That is, as shown in FIG. 4, the direction indicated by the arrow A corresponds to the radially outer side of the electrode group 22, and the direction indicated by the arrow B corresponds to the radially inner side of the electrode group 22. The first surface 58 is disposed on the A direction side and the second surface 60 is disposed on the arrow B direction side, and the winding operation is performed in this state.

  Specifically, as shown in FIG. 4, two separators 28 are prepared, and a laminate is formed by laminating the separator 28, the positive electrode 24, the separator 28, and the negative electrode 26 in this order from the bottom. At this time, the negative electrode 26 is disposed so that the first surface 58 is on the upper side and the second surface 60 is on the positive electrode 24 side. And the winding core 62 is arrange | positioned at one edge part of the separator 28 of the lowest layer, the negative electrode 26 is made the outer side, the winding core 62 is rotated in the arrow C direction, and a laminated body is wound. Thereby, the electrode group 22 is formed. In the obtained electrode group 22, the first negative electrode mixture layer 54 containing the first hydrogen storage alloy particles 50 and the radially inner side surface 64 located on the radially inner side of the electrode group 22 in the positive electrode 24 are opposed to each other. The second negative electrode mixture layer 56 containing the second hydrogen storage alloy particles 52 and the radially outer surface 66 located on the radially outer side of the electrode group 22 in the positive electrode 24 are opposed to each other.

  For this reason, even if the radial inner side surface 64 of the positive electrode 24 locally rises due to the winding operation, the first hydrogen storage alloy particles 50 present in the corresponding part of the negative electrode 26 have a relatively small particle size. The unevenness of the first surface 58 of the negative electrode 26 (the surface of the first negative electrode mixture layer 54) becomes small and the separator 28 is difficult to break through. On the other hand, on the radially inner side (second negative electrode mixture layer 56) of the electrode group 22 in the negative electrode 26 that is not affected by the local bulge of the positive electrode 24, the second hydrogen storage alloy having a relatively large particle size and excellent corrosion resistance. Particles 52 can be present.

  The electrode group 22 thus obtained is accommodated in the outer can 10. Subsequently, a predetermined amount of alkaline electrolyte is injected into the outer can 10. Thereafter, the outer can 10 containing the electrode group 22 and the alkaline electrolyte is sealed by the cover plate 14 provided with the positive electrode terminal 20, and the battery 2 according to the present invention is obtained.

  As described above, in the battery 2 of the present invention, the first hydrogen storage alloy particles 50 included in the first negative electrode mixture layer 54 of the negative electrode 26 are the second hydrogen included in the second negative electrode mixture layer 56 of the negative electrode 26. The particle size is smaller than the occlusion alloy particles 52. The first negative electrode mixture layer 54 of the negative electrode 26 is located on the radially outer side of the electrode group 22, and the second negative electrode mixture layer 56 of the negative electrode 26 is located on the radially inner side of the electrode group 22. Therefore, the first negative electrode mixture layer 54 is opposed to the radially inner surface of the electrode group 22 in the positive electrode 24, and the second negative electrode mixture layer 56 of the negative electrode 26 is the radially outer surface of the electrode group 22 in the positive electrode 24. Relative to Therefore, even if the radially inner surface of the electrode group 22 in the positive electrode 24 rises toward the negative electrode 26, the surface (first surface 58) of the first negative electrode mixture layer 54 of the negative electrode 26 has small unevenness, so that the separator 28 is broken. Is suppressed and it is difficult to cause a short circuit. On the other hand, the radially outer surface of the electrode group 22 in the positive electrode 24 does not swell toward the second negative electrode mixture layer 56 side of the negative electrode 26, and a problem that breaks the separator 28 is unlikely to occur. For this reason, in the second negative electrode mixture layer 56 of the negative electrode 26, the second hydrogen storage alloy particles 52 having a particle diameter larger than that of the first hydrogen storage alloy particles 50 can be arranged. Since the second hydrogen storage alloy particles 52 have a large particle size, they are excellent in corrosion resistance against alkaline electrolyte and contribute to extending the life of the battery. Therefore, the nickel-metal hydride storage battery of the present invention is an excellent battery that can achieve both reduction in the occurrence rate of short circuit failure of the battery and extension of the battery life.

[Example]
1. Production of Battery Example 1
(1) Production of positive electrode A nickel foam having a basis weight of 400 g / cm ² and a thickness of about 2 mm was prepared.

  Next, 10 parts by mass of nickel positive electrode active material powder composed of nickel hydroxide particles, 0.01 parts by mass of cobalt monoxide powder as a conductive material, 0.003 parts by mass of carboxymethyl cellulose as a binder, and 5 parts by mass of water are mixed. Thus, a positive electrode mixture paste was prepared.

  The obtained positive electrode mixture paste was filled in the nickel foam described above. The nickel foam filled with the positive electrode mixture was dried and rolled. The nickel foam to which the positive electrode mixture that had been rolled was attached was cut into a predetermined shape and formed into a positive electrode 24 for AA size.

(2) Production of Negative Electrode As a negative electrode core, a non-porous nickel-plated steel sheet in which a cold-rolled steel sheet (SPCC steel sheet) with a thickness of 25 μm was plated with a nickel with a thickness of 1.5 μm was prepared.

Next, a hydrogen storage alloy having a composition of Nd _0.36 Sm _0.54 Mg _0.10 Ni _3.33 Al _0.17 was produced. The obtained hydrogen storage alloy is pulverized, and a first hydrogen storage alloy powder composed of first hydrogen storage alloy particles having an average particle diameter of 35 μm and a second hydrogen storage alloy composed of second hydrogen storage alloy particles having an average particle diameter of 100 μm. An alloy powder was prepared. Then, with respect to 10 parts by mass of the first hydrogen storage alloy powder, 0.005 parts by mass of carboxymethyl cellulose as a binder, 0.05 parts by mass of carbon black as a conductive material, and 2.5 parts by mass of water are added and kneaded. The first negative electrode mixture paste was prepared. On the other hand, with respect to 10 parts by mass of the second hydrogen storage alloy powder, 0.005 parts by mass of carboxymethyl cellulose as a binder, 0.05 parts by mass of carbon black as a conductive material, and 2.5 parts by mass of water are added and kneaded. Then, a second negative electrode mixture paste was prepared.

Next, the first negative electrode mixture paste was applied to the first surface of the non-porous nickel-plated steel sheet as the prepared negative electrode core so as to have a thickness of 0.29 mm using a die coater. Subsequently, the second negative electrode mixture paste was applied to the second surface of the nickel-plated steel sheet using a die coater so that the thickness was 0.29 mm.
After drying the first and second negative electrode mixture pastes, the non-porous nickel-plated steel sheet to which the hydrogen-absorbing alloy powder and the like were adhered was further rolled and cut to produce an AA-size negative electrode 26.

(3) Assembly of Nickel Metal Hydride Battery ^Two separators 28 made of a nonwoven fabric made of polypropylene fiber having a thickness of 0.1 mm (weight is 40 g / m ² ) were prepared. And these were laminated | stacked in order of the separator 28, the positive electrode 24, the separator 28, and the negative electrode 26 from the bottom, and the laminated body was formed. At this time, the negative electrode 26 was disposed with the first surface 58 on the upper side and the second surface 60 facing the positive electrode 24 side. And the winding core 62 was arrange | positioned at the one end of the separator 28 of the lowest layer, the negative electrode 26 was turned outside, and the above-mentioned laminated body was wound. Thereby, the spiral electrode group 22 was produced.

  Next, the obtained electrode group 22 was accommodated in the outer can 10. The outer can 10 has a bottomed cylindrical shape made of a cold-rolled steel plate with nickel plating. Then, 2.2 g of an alkaline electrolyte composed of a 30% by mass aqueous sodium hydroxide solution was injected into the outer can 10. Thereafter, the opening of the outer can 10 was closed with the cover plate 14 or the like, and the AA size cylindrical nickel-metal hydride storage battery 2 was assembled. This nickel metal hydride storage battery is referred to as battery a. And 1000 pieces of this battery a were manufactured.

Comparative Example 1
1000 nickel-metal hydride storage batteries (batteries b) were produced in the same manner as in Example 1 except that the conventional negative electrode as shown below was used.
The conventional negative electrode was manufactured as follows.
First, as a negative electrode core, a punching metal sheet formed by cold drilling steel plate (SPCC steel plate) having a thickness of 60 μm with a large number of through-holes having a diameter of 1 mm formed in a lattice shape and nickel plating having a thickness of 1.5 μm. Prepared. The punching metal sheet has a hole area ratio of 43%.

Subsequently, a hydrogen storage alloy having a composition of Nd _0.36 Sm _0.54 Mg _0.10 Ni _3.33 Al _0.17 is manufactured, and the obtained hydrogen storage alloy is pulverized to form hydrogen storage alloy powder comprising hydrogen storage alloy particles having an average particle size of 65 μm. Prepared. Then, with respect to 10 parts by mass of the hydrogen storage alloy powder, 0.005 part by mass of carboxymethyl cellulose as a binder, 0.05 part by mass of carbon black as a conductive material, and 2.5 parts by mass of water are added and kneaded. A negative electrode mixture paste was prepared.

  And this negative electrode mixture paste was apply | coated by the thickness of 0.25 mm, respectively on both surfaces of the prepared punching metal sheet using the die-coater. After the negative electrode mixture paste was dried, the punched metal sheet to which the hydrogen storage alloy powder or the like was attached was further rolled and cut to produce a conventional negative electrode for AA size.

2. Evaluation of Nickel Metal Hydride Battery (1) Incidence of short circuit failure A voltage of 100 V was applied to each of 1000 batteries a and 1000 batteries b, and the presence or absence of a short circuit at that time was examined. The number of short-circuited batteries was counted, the ratio of the short-circuited batteries out of 1000 batteries was determined, and the value is shown in Table 1 as the incidence of short-circuit defects.

(2) Discussion As is apparent from the results in Table 1, the incidence of short circuit failure in the battery b of Comparative Example 1 is 0.4%, whereas the incidence of short circuit failure in the battery a of Example 1 is It can be seen that the rate of occurrence of short circuit failure is improved by 0.2% in the battery a of Example 1 compared to the battery b of Comparative Example 1. This is because, in the battery a of Example 1, the average particle diameter of the first hydrogen storage alloy particles contained in the first negative electrode mixture layer of the negative electrode is contained in the second negative electrode mixture layer of the negative electrode. Since it is set smaller than the average particle diameter of the two hydrogen storage alloy particles, the first negative electrode mixture layer of the negative electrode has relatively small surface irregularities. And this 1st negative mix layer is arrange | positioned so as to oppose the radial inside of the electrode group in a positive electrode. For this reason, even if the inner side in the radial direction of the electrode group in the positive electrode rises to the negative electrode side as the electrode group is wound, the surface of the first negative electrode mixture layer of the corresponding negative electrode has small irregularities, so that the separator breaks. It is difficult to do. Thereby, the short circuit incidence rate of the battery a of Example 1 was suppressed low.

  Further, in the battery a of Example 1, the hydrogen storage alloy particles having a relatively large particle size are formed on the second negative electrode mixture layer of the negative electrode corresponding to the radially outer portion of the electrode group in the positive electrode, which is a portion where short-circuiting is difficult to occur. Could be placed. In other words, since the hydrogen storage alloy particles having a large particle size and excellent corrosion resistance to the alkaline electrolyte can be disposed in a place where short-circuiting is unlikely to occur, the battery a of Example 1 aims to extend the life of the battery while suppressing the occurrence of short-circuiting. It is possible.

2 Nickel metal hydride storage battery 10 Exterior can 12 Insulating packing 14 Cover plate 20 Positive electrode terminal 22 Electrode group 24 Positive electrode 26 Negative electrode 28 Separator 40 Metal sheet (negative electrode core)
42 1st surface 44 2nd surface 50 1st hydrogen storage alloy particle 52 2nd hydrogen storage alloy particle 54 1st negative electrode mixture layer 56 2nd negative electrode mixture layer

Claims (2)

A container, and a positive electrode and a negative electrode wound in a state of sandwiching a separator, and an electrode group housed in an airtight state together with an alkaline electrolyte in the container,
The negative electrode is formed on a first negative electrode core having a first surface located radially outside the electrode group and a second surface located radially inner of the electrode group, and a first surface of the negative electrode core. The first negative electrode mixture layer formed, and a second negative electrode mixture layer formed on the second surface of the negative electrode core,
The negative electrode core is made of a metal sheet,
The metal sheet is a non-porous metal sheet,
The nickel hydride storage battery, wherein an average particle diameter of the hydrogen storage alloy particles contained in the first negative electrode mixture layer is smaller than an average particle diameter of the hydrogen storage alloy particles contained in the second negative electrode mixture layer. A container, and a positive electrode and a negative electrode wound in a state of sandwiching a separator, and an electrode group housed in an airtight state together with an alkaline electrolyte in the container,
The negative electrode is formed on a first negative electrode core having a first surface located radially outside the electrode group and a second surface located radially inner of the electrode group, and a first surface of the negative electrode core. The first negative electrode mixture layer formed, and a second negative electrode mixture layer formed on the second surface of the negative electrode core,
The negative electrode core is made of a metal sheet,
The metal sheet is a metal sheet having an open area ratio represented by a ratio of the area of the through holes per unit area of the negative electrode core of 10% or less,
The nickel hydride storage battery, wherein an average particle diameter of the hydrogen storage alloy particles contained in the first negative electrode mixture layer is smaller than an average particle diameter of the hydrogen storage alloy particles contained in the second negative electrode mixture layer.

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