JP2005056675A - Cylindrical alkaline battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cylindrical alkaline battery suitable for high capacity and having superior cycle characteristics. <P>SOLUTION: This cylindrical alkaline battery is housed in the outer package can, and is formed by spirally winding a band-like negative core body 46 and a negative electrode 26 including hydrogen storage alloy layers (active material layers) 48, 50 retained by the negative core body 46 as well as a positive electrode via a separator. In the cylindrical alkaline battery, the electrode group in which the outermost peripheral part consisting of the negative electrode 26 is contacted with the peripheral wall of the exterior can and which is arranged at the outside of the outer end of the positive electrode via a separator is provided. The negative electrode 26 has a main body part 52 wound inside the electrode group, a thin walled part 56 in which the thickness of the hydrogen storage alloy layer 50 is smaller than the main body part 52 and the amount of hydrogen storage alloy contained per unit volume of the hydrogen storage alloy layers 48, 50 is larger than the main body part 52, and a boundary part 54 which is formed between the main body 52 and the thin walled part 56 and in which the thickness in the longitudinal direction of the hydrogen storage alloy layers 48, 50 is varied. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a cylindrical alkaline storage battery suitable for high capacity.

Examples of the alkaline storage battery include a nickel cadmium secondary battery and a nickel metal hydride secondary battery, depending on the type of active material contained. These alkaline storage batteries each have a strip-shaped negative electrode and a positive electrode with a separator in between. There is a cylindrical type in which a group of electrodes wound in a spiral shape is housed in a cylindrical outer can.
In this type of cylindrical alkaline storage battery, the negative electrode capacity is larger than the positive electrode capacity in order to reduce the oxygen gas generated during overcharge and prevent the internal pressure from rising. An increase in the amount of substances is required, and various proposals have been made to meet this requirement (see, for example, Patent Document 1).

The cylindrical alkaline storage battery disclosed in Patent Literature 1 is positioned on the outermost periphery of the electrode group, and the volume of the negative electrode portion that contributes less to the battery reaction is made thinner than other portions, thereby increasing the volume efficiency and increasing the efficiency. It is considered that the capacity is achieved.
JP-A-4-206474

However, in the cylindrical alkaline storage battery of Patent Document 1, as the thinned portion of the negative electrode is made thinner for higher capacity, the oxygen gas that is generated during charging and flows between the electrode group and the outer peripheral wall of the outer can, It will not be fully reduced in the thin part. Therefore, since the internal pressure is likely to increase during charging due to the thinning and the cycle characteristics deteriorate, this battery has a problem that it is difficult to achieve both high capacity and cycle characteristics.
An object of the present invention is to solve the above problems and to provide a cylindrical alkaline storage battery suitable for increasing the capacity and having good cycle characteristics.

  In order to achieve the above-described object, in the invention of claim 1, a conductive cylindrical outer can, and the outer can are accommodated together with an alkaline electrolyte, and are held by the strip-shaped negative electrode core and the negative electrode core. The negative electrode including the active material layer and the positive electrode are wound in a spiral shape so that the negative electrode is positioned on the outermost periphery through a separator, and the outermost peripheral portion made of the negative electrode is in contact with the peripheral wall of the outer can and the separator A cylindrical alkaline storage battery including an electrode group disposed outside the outer end of the positive electrode, the negative electrode includes a main body wound inside the electrode group, and an outermost periphery of the electrode group A thin-walled portion that is wound as a portion, the thickness of the active material layer is smaller than that of the main-body portion, and the amount of active material contained per unit volume of the active-material layer is large, and the main-body portion and the thin-walled portion Formed between and said negative As viewed in the longitudinal direction of the core is characterized by and a boundary portion having a thickness varying in the active material layer.

  In the above configuration, since the negative electrode has a thin portion, the cylindrical alkaline storage battery is suitable for increasing the capacity. On the other hand, the amount of active material contained per unit volume of the active material layer is larger in the thin part than in the main part, and the thin part efficiently reduces oxygen gas that has entered the can between the electrode group and the outer peripheral wall of the outer can. Therefore, an increase in internal pressure is suppressed during charging. Therefore, this cylindrical alkaline storage battery has good cycle characteristics because even if the thinned portion is thinned for high capacity, an increase in internal pressure and a decrease in alkaline electrolyte based thereon are prevented.

  Further, in the above-described configuration, the amount of the active material contained per unit volume of the active material layer is larger in the thin part than in the main body part, so that the permeability of the alkaline electrolyte is lowered in the thin part. Therefore, according to this configuration, by reducing the amount of the alkaline electrolyte contained in the thin-walled portion, the amount of the alkaline electrolyte is reduced as a whole while ensuring the amount of the alkaline electrolyte necessary for the battery reaction. The capacity can be increased.

In the invention of claim 2, the amount of active material contained per unit area of the active material layer of the thin-walled portion is 40% to 75% of the amount of active material contained per unit area of the active material layer of the main body portion. It is characterized by being.
In the configuration described above, the amount of active material contained per unit volume of the active material layer in the thin-walled portion is larger than the amount of active material contained per unit volume of the active material layer in the main body portion. The thinner the thin portion, the smaller the amount of active material contained per unit area of the thin portion than the amount of active material contained per unit area of the main body. Therefore, this cylindrical alkaline storage battery has an active material amount per unit area of the thin-walled portion within a range of 40% to 75% of the amount of active material contained per unit area of the main body portion. Although the portion is thinned, the amount of active material that contributes to the battery reaction with the positive electrode and the reduction reaction of the oxygen gas that has entered between the electrode group and the peripheral wall of the outer can is secured in the thin portion. Therefore, this cylindrical alkaline storage battery reliably achieves both high capacity and cycle characteristics.

According to a third aspect of the present invention, the negative electrode core is made of a punching metal, the active material layer is held on both surfaces of the negative electrode core, and the active material layer is held inside the negative electrode core at the thin portion. Is thicker than the active material layer held outside the negative electrode core.
In the configuration described above, the thickness of the active material layer held inside the negative electrode core that faces the positive electrode through the separator and contributes to both the battery reaction and the oxygen gas reduction reaction with the positive electrode, By making it thicker than the thickness of the active material layer held on the outside of the negative electrode core, which contributes exclusively to the reduction reaction of oxygen gas that has come into contact with the can and between the electrode group and the peripheral wall of the outer can, It efficiently balances capacity and cycle characteristics.

The invention according to claim 4 is characterized in that the outer end of the positive electrode and the boundary portion of the negative electrode are positioned at different circumferential positions of the electrode group.
In the configuration described above, the boundary between the outer periphery of the positive electrode and the negative electrode is positioned at different circumferential positions of the electrode group, so that when the electrode group is inserted into the outer can, the thin portion covering the outer side of the positive electrode outer end The bending is small, and the thin-walled portion can be bent without cracking or breaking. Therefore, this cylindrical alkaline storage battery has an increase in internal resistance due to cracks and breaks in thin-walled parts, heat generation during charging and discharging, or short-circuits that occur when cracks and breaks break through the separator and contact the positive electrode. It is prevented.

The invention according to claim 5 is characterized in that a length of the thin portion is 2.5 to 3.8 times an inner diameter of the outer can.
In the configuration described above, the outer end of the positive electrode and the boundary between the negative electrode are positioned at different circumferential positions of the electrode group, so although it is partial, the positive electrode is disposed on both sides of the thin part, The positive electrode may not be disposed outside the main body. In these cases, the amount of the active material that contributes to the battery reaction with the positive electrode may be excessive or insufficient, and the balance between the increase in capacity and the cycle characteristics may be lost. Therefore, in this cylindrical alkaline storage battery, the length of the thin wall portion falls within the range of 2.5 to 3.8 times the inner diameter of the outer can, thereby suppressing the excess and deficiency of the amount of active material, Higher capacity and cycle characteristics are more reliably achieved.

The invention according to claim 6 is characterized in that an inclination angle of the active material layer in the boundary portion is more than 0 degree and less than 10 degrees.
In the above-described configuration, the concentration of the active material layer at the boundary portion falls within the range of 0 ° <θ <10 ° so that the change in thickness is moderate, thereby preventing stress concentration during winding. The lack of strength at the boundary is resolved, and cracks and breaks are prevented from occurring at the boundary. Therefore, this cylindrical alkaline storage battery has an increase in internal resistance due to cracks and breaks at the boundary, heat generation during charging and discharging, or short-circuits that occur when cracks or breaks break through the separator and contact the positive electrode. It is prevented.

The invention according to claim 7 is characterized in that a mass per unit area of the negative electrode core in the boundary portion is larger than a mass per unit area of the negative electrode core in the main body.
In the above configuration, the negative electrode core is reinforced at the boundary so that the mass per unit area of the negative electrode core is larger at the boundary than at the main body and the thin wall, and thus cracked at the boundary during winding. And preventing breakage. Therefore, this cylindrical alkaline storage battery has increased internal resistance due to cracks and breaks at the boundary, heat generation during charging and discharging, or short-circuits that occur when cracks or breaks break through the separator and contact the positive electrode. It is more reliably prevented.

  As described above, according to the cylindrical alkaline storage battery of the present invention, the thin-walled portion efficiently reduces the oxygen gas that has entered the can between the electrode group and the peripheral wall of the outer can. It is suppressed. Therefore, this cylindrical alkaline storage battery is suitable for high capacity and has a good cycle because even if the thin wall portion is thinned for high capacity, an increase in internal pressure and a decrease in alkaline electrolyte based thereon are prevented. It has characteristics and is suitable for various power sources such as transportation machines, machine tools, communication equipment, electrical / electronic equipment and toys, and has great industrial value.

A cylindrical nickel-hydrogen secondary battery (hereinafter referred to as battery A) according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings.
As shown in FIG. 1, the battery A includes an outer can 10 having a bottomed cylindrical shape with an open upper end, and the outer can 10 has conductivity and functions as a negative electrode terminal. In the opening of the outer can 10, a conductive cover plate 14 is disposed via a ring-shaped insulating packing 12, and the insulating packing 12 and the cover plate 14 are fixed in the opening by caulking the opening edge. Yes.

  The cover plate 14 has a gas vent hole 16 in the center, and a rubber valve element 18 is disposed on the outer surface of the cover plate 14 so as to close the gas vent hole 16. Further, a cap-shaped positive terminal 20 covering the valve body 18 is fixed on the outer surface of the cover plate 14, and the positive terminal 20 presses the valve body 18 against the cover plate 14. Accordingly, the outer can 10 is normally airtightly closed by the lid plate 14 together with the insulating packing 12 and the valve body 18. On the other hand, when gas is generated in the outer can 10 and its internal pressure increases, the valve body 18 is compressed and the gas is released from the outer can 10 through the gas vent hole 16. That is, the cover plate 14, the valve body 18, and the positive electrode terminal 20 form a safety valve.

A substantially cylindrical electrode group 22 is accommodated in the outer can 10 together with an alkaline electrolyte (not shown), and the outermost peripheral portion of the electrode group 22 is in direct contact with the peripheral wall of the outer can 10. The electrode group 22 includes a positive electrode 24, a negative electrode 26, and a separator 28. Examples of the alkaline electrolyte include a sodium hydroxide aqueous solution, a lithium hydroxide aqueous solution, a potassium hydroxide aqueous solution, and an aqueous solution obtained by mixing two or more of these. Etc.
Further, in the outer can, a positive electrode lead 30 is disposed between one end of the electrode group 22 and the lid plate 14, and both ends of the positive electrode lead 30 are connected to the positive electrode 24 and the lid plate 14. Therefore, the positive electrode terminal 20 and the positive electrode 24 are electrically connected via the positive electrode lead 30 and the lid plate 14. A circular 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 provided in the insulating member 32. A circular insulating member 34 is also disposed between the electrode group 22 and the bottom of the outer can 10.

Referring to FIG. 2, in the electrode group 22, the positive electrode 24 and the negative electrode 26 are alternately overlapped when viewed in the radial direction of the electrode group 22 with the separator 28 interposed therebetween.
More specifically, each of the electrode groups 22 includes a strip-like positive electrode 24, a negative electrode 26, and a separator 28. It is formed by winding. Therefore, one end (inner end) 36, 38 of the positive electrode 24 and the negative electrode 26 is positioned on the center side of the electrode group 22, while the other end (outer end) 40, 42 of the positive electrode 24 and the negative electrode 26 is the outer periphery of the electrode group 22. Is located on the side. The negative electrode 26 is longer than the positive electrode 24, extends in a spiral shape from the inside of the positive electrode inner end 36 to the outer side of the positive electrode outer end 40, and sandwiches the positive electrode 24 from both sides across the entire longitudinal direction via the separator 28. Yes. The separator 28 is not wound around the outermost periphery of the electrode group 22, and the negative electrode 26 forms the outermost periphery of the electrode group 22. In the outermost peripheral portion of the electrode group 22, the negative electrode 26 and the outer can 10 are electrically connected to each other, and the negative electrode outer end 42 is sufficient for the negative electrode 26 to cover the outside of the positive electrode outer end 40 through the separator 28. It is positioned in the vicinity of the positive electrode outer end 40, separated by a length. Since the core is pulled out after winding, a space 44 corresponding to the shape of the core exists in the center of the electrode group 22.

Examples of the material of the separator 28 include polyamide fiber nonwoven fabrics, and polyolefin fiber nonwoven fabrics such as polyethylene and polypropylene that are provided with hydrophilic functional groups.
Although not shown, the positive electrode 24 has a conductive positive electrode core having a strip shape, and a positive electrode mixture is held in the core. Examples of the positive electrode core include a foamed nickel base material having a porous structure. In the case of a foamed nickel base material, the positive electrode mixture is held in the communication hole of the foamed nickel base material.

  The positive electrode mixture includes, for example, a positive electrode active material, an additive, and a binder. The positive electrode active material is not particularly limited, and examples thereof include nickel hydroxide particles or nickel hydroxide particles in which cobalt, zinc, cadmium or the like is dissolved. Examples of the additive include a conductive agent made of a cobalt compound, and examples of the binder include a hydrophilic or hydrophobic polymer.

  As shown in FIG. 3 and FIG. 4, the negative electrode 26 has a conductive negative electrode core 46 having a strip shape, and the negative electrode mixture 46 holds a negative electrode mixture. The negative electrode core 46 is made of a sheet-like metal material having a plurality of through-holes in the thickness direction, and examples thereof include a punching metal, a metal powder sintered body substrate, an expanded metal, and a nickel net. I can give you. In particular, a punched metal or a metal powder sintered body substrate obtained by molding and sintering a metal powder is suitable for the negative electrode core 46. In FIG. 1 and FIG. 2, the negative electrode core 46 is omitted for convenience of drawing.

Since the battery A is a nickel metal hydride secondary battery, the negative electrode mixture is composed of hydrogen storage alloy particles capable of storing and releasing hydrogen as a negative electrode active material and a binder. In the present invention, the hydrogen storage alloy is included in the active material for convenience.
The hydrogen storage alloy particles may be any particles that can store hydrogen generated electrochemically in an alkaline electrolyte when the battery A is charged and can easily release the stored hydrogen during discharge. Such a hydrogen storage alloy is not particularly limited, and examples thereof include AB ₅ type alloys such as LaNi ₅ and MmNi ₅ (Mm is a misch metal). In addition, examples of the binder include hydrophilic or hydrophobic polymers. Further, a conductive agent such as carbon black or Ni powder may be added as necessary. If a cadmium compound is used instead of the hydrogen storage alloy, the battery A can be a nickel cadmium secondary battery, but a nickel hydride secondary battery is suitable for improving the battery capacity.

  The negative electrode mixture described above is filled in the through holes of the negative electrode core body 46 and the negative electrode core body 46 is in the form of a sheet. (Mixture layer) is formed. Hereinafter, the layer of the negative electrode mixture that covers the inner surface of the negative electrode core 46 and faces the central axis side of the electrode group 22 is referred to as the inner hydrogen storage alloy layer 48 or the inner alloy layer 48, and the outer surface of the negative electrode core 46 is The layer of the negative electrode mixture that is covered and faces the outside of the electrode group 22 is referred to as an outer hydrogen storage alloy layer 50 or an outer alloy layer 50.

  In the negative electrode 26, the thickness T 2 of the inner alloy layer 48 is substantially constant when viewed in the longitudinal direction of the negative electrode core 46. On the other hand, the thickness of the outer alloy layer 50 varies between the negative electrode inner end 38 and the negative electrode outer end 42, and the negative electrode 26 has three regions with respect to the thickness of the outer alloy layer 50 as viewed in the longitudinal direction of the negative electrode core 46. In other words, the main body 52, the boundary 54, and the thin portion 56 are sequentially divided from the negative inner end 38 toward the negative outer end 42.

  The main body 52 is wound inside the electrode group 22, and the positive electrode 24 is disposed on both sides with the separator 28 interposed therebetween. The thickness of the outer alloy layer 50 in the main body 52 is approximately equal to the thickness T2 of the inner alloy layer 48.

  The boundary portion 54 is formed between the main body portion 52 and a thin-walled portion 56 to be described later, the thickness changes in the longitudinal direction of the negative electrode core 46, and the electrode group 22 when wound as the electrode group 22. When viewed in the circumferential direction, the positive electrode outer end 40 is positioned at a different position. In the present embodiment, the boundary portion 54 has a length L, and the thickness of the outer alloy layer 50 at the boundary portion 54 gradually decreases from the main body portion 52 toward the thin portion 56 at a substantially constant change rate, It changes from thickness T2 to thickness T1.

  When the negative electrode 26 is developed on a flat reference surface, the inclination angle of the surface of the outer alloy layer 50 in the boundary portion 54 with respect to the surface of the outer alloy layer 50 in the reference surface or the thin portion 56 is θ, The inclination angle θ is within a range of 0 ° <θ <10 ° as a preferred embodiment.

  The thin portion 56 is wound around the outer side of the electrode group 22 to form the outermost peripheral portion of the electrode group 22, covers the outer side of the positive electrode outer end 40 via the separator 28, and is in close contact with the peripheral wall of the outer can 10. The thickness T1 of the outer alloy layer 50 in the thin portion 56 is constant in the longitudinal direction of the negative electrode core 46, and is thinner than the thickness of the outer alloy layer 50 in the main body portion 52, that is, the thickness T2 of the inner alloy layer 48. . Therefore, in the thin portion 56, the inner alloy layer 48 is thicker than the outer alloy layer 50.

In addition, the length Xd of the thin part 56 is in the range of 2.5 times to 3.8 times the inner diameter d of the outer can 10 as a preferable aspect.
Thus, in the negative electrode 26, the thin portion 56 is thinner than the main body portion 52. In addition, the amount of hydrogen storage alloy particles contained per unit volume of the inner and outer alloy layers 48 and 50 in the thin portion 56 is included per unit volume of the inner and outer alloy layers 48 and 50 in the main body 52. More than the amount of hydrogen storage alloy particles.

In the negative electrode 26, as a preferred embodiment, the amount of hydrogen storage alloy contained per unit area of the thin portion 56 is in the range of 40% to 75% of the amount of hydrogen storage alloy contained per unit area of the main body portion 52. In.
Although the battery A described above can be manufactured by applying a normal method, an example of a method for manufacturing the negative electrode 26 will be described below.

  First, a paste of, for example, punching metal and negative electrode mixture to be the negative electrode core 46 is prepared, and the paste is applied to the punching metal so that the thin portion 56 is thin and the main portion 52 is thick. Wear and dry. Next, the punched metal holding the dried negative electrode mixture is compressed from both sides in the thickness direction through a gap between the pair of rolling rolls. During this rolling, the pressing force of the roll is variably controlled so as to be larger in the portion that becomes the thin portion 56 than in the portion that becomes the main body portion 52, and in the obtained negative electrode 26, the unit volume of the inner and outer alloy layers 48 and 50 is increased. The amount of the hydrogen storage alloy contained per hit is made larger in the thin portion 56 than in the main body portion 52. Then, the rolled product is cut into a predetermined size, and the strip-shaped negative electrode 26 is manufactured. The inclination angle θ of the boundary portion 54 can be adjusted by controlling the thickness of the paste to be applied, the roll pressing force, or the like.

  According to the battery A having the above-described configuration, the volume of the positive electrode 24 can be increased corresponding to the volume of the negative electrode 26 that is reduced by making the thin portion 56 thinner than the main body portion 52. By increasing the volume of the positive electrode 24, the amount of the positive electrode active material contained in the battery A is increased, so that the capacity of the battery A is increased.

  In the battery A, the amount of hydrogen storage alloy contained per unit volume of the inner and outer alloy layers 48 and 50 in the thin portion 56 is included per unit volume of the inner and outer alloy layers 48 and 50 in the main body 52. Since it is larger than the amount of hydrogen storage alloy, it has good cycle characteristics.

  In the battery A, the amount of hydrogen storage alloy contained per unit volume of the inner and outer alloy layers 48 and 50 is larger in the thin portion 56 than in the main body portion 52, in other words, the inner and outer alloy layers 48 and 50. Since the density of the hydrogen storage alloy is higher in the thin portion 56 than in the main body portion 52, the permeability of the alkaline electrolyte into the inner and outer alloy layers 48 and 50 is lower in the thin portion 52 than in the main portion 56. When the permeability of the alkaline electrolyte is lowered, the gas permeability is improved. Therefore, the oxygen gas permeability in the inner and outer alloy layers 48 and 50 is higher in the thin portion 56 than in the main body portion 52. Since oxygen gas permeability is high in this way, the inner and outer alloy layers 48, 50 contribute to the oxygen gas reduction reaction over the entire thickness of the thin portion 56, and the oxygen gas reduction capability is improved. The thin-walled portion 56 can efficiently reduce oxygen gas that is generated during charging and has entered between the electrode group 22 and the peripheral wall of the outer can 10. Therefore, in the battery A, the thin portion 56 is thinned to increase the capacity, and even when the amount of the hydrogen storage alloy contained in the thin portion 56 is reduced, an increase in internal pressure is prevented. Spills to the outside and decreases, and deterioration of cycle characteristics is prevented.

  The thin portion 56 is rolled with a larger pressing force than the main body portion 52, so that the particle size of the hydrogen storage alloy particles is smaller in the thin portion 56 than in the main body portion 52. Therefore, it is considered that an increase in the reaction area between the oxygen gas and the hydrogen storage alloy particles due to the reduction in the particle size of the hydrogen storage alloy particles contributes to the improvement of the oxygen gas reduction capability in the thin portion 56. It is done.

  In the battery A, since the permeability of the alkaline electrolyte is lowered at the thin portion 56 as described above, the amount of the alkaline electrolyte contained per unit volume of the inner and outer alloy layers 48 and 50 is reduced. Since the main body portion 52 is larger than the main body portion 52, it is suitable for further increasing the capacity.

  If the amount of the alkaline electrolyte contained in the outer can 10 is reduced, the volume of the positive electrode 24 can be increased and the battery capacity can be increased accordingly. However, as the amount of the alkaline electrolyte is decreased, the positive electrode 24 and the negative electrode 26 Since the battery reaction does not proceed smoothly, the battery capacity may be reduced. However, since the positive electrode 24 is disposed only on the inner side of the thin portion 56 through the separator 28, the thin portion 56 contributes less to the battery reaction than the main body portion 52 in which the positive electrode 24 is disposed on both sides. Requires a smaller amount of alkaline electrolyte than the body portion 52. Therefore, in the battery A, by reducing the permeability of the alkaline electrolyte and reducing the amount of the alkaline electrolyte contained in the thin portion 56, the amount of the alkaline electrolyte as a whole is ensured while ensuring the amount of the alkaline electrolyte necessary for the battery reaction. Weight loss is possible. Therefore, according to the battery A, it is possible to further increase the capacity.

  Further, in the battery A, the amount of the hydrogen storage alloy contained per unit area of the thin portion 56 is in the range of 40% to 75% of the amount of the hydrogen storage alloy contained per unit area of the main body portion 52. Capacitance and cycle characteristics are both balanced.

  As described above, the capacity of the battery A can be increased as the thin portion 56 is made thinner. On the other hand, the thin-walled portion 56 contributes to the battery reaction because the positive electrode 24 is disposed on the inner side through the separator 28, and reduces oxygen gas that has circulated between the electrode group 22 and the peripheral wall of the outer can 10. Thus, it has a function of returning to water and preventing an increase in the internal pressure of the battery A. Therefore, in the battery A, the amount of the hydrogen storage alloy contained per unit area of the thin portion 56 is set within the range of 40% to 75% of the amount of the hydrogen storage alloy contained per unit area of the main body portion 52, and the thin portion Although the thickness of 56 is reduced, the amount of the hydrogen storage alloy that contributes to the battery reaction and the reduction reaction of the oxygen gas that has circulated is secured, the capacity is increased, and the cycle characteristics are reduced by reducing the alkaline electrolyte due to the increase in internal pressure. It is possible to prevent deterioration.

  In the battery A, the thickness of the inner alloy layer 48 that faces the positive electrode 24 through the separator 28 and contributes to both the battery reaction and the oxygen gas reduction reaction is separated from the inner alloy layer 48 by the negative electrode core 46. The thickness of the outer alloy layer 50 that is opposed only to the peripheral wall of the outer can 10 and that contributes only to the reduction reaction of oxygen gas that has circulated between the electrode group 22 and the peripheral wall of the outer can 10 only. High capacity and cycle characteristics are efficiently achieved.

  Further, in the battery A, since the boundary portion 54 and the positive electrode outer end 40 are positioned at different circumferential positions of the electrode group 22, the occurrence of cracks and breaks in the thin portion 56 is prevented, thereby reducing the internal resistance. Increase, heat generation or short circuit based on the increase are prevented.

  Although the thin portion 56 covers the outside of the positive electrode outer end 40 via the separator 28, immediately after the electrode group 22 is wound, the positive electrode outer end 40 is stepped inside the thin portion 56 according to the thickness of the positive electrode 24. Is forming. In addition, this step becomes large when the boundary portion 54 and the positive electrode outer end 40 overlap with each other through the separator 28. On the other hand, although the cross-sectional shape of the electrode group 22 is substantially circular, it is maximized in the direction connecting the central axis and the positive electrode outer end 40, and when the electrode group 22 is inserted into the outer can 10, By the opening edge or the peripheral wall of the can 10, the can 10 is compressed most in the direction in which the diameter becomes maximum. For this reason, when the electrode group 22 is inserted, the thin-walled portion 56 is compressed and bent according to the shape of the step formed by the positive electrode outer end 40, but the boundary portion 54 and the positive electrode outer end 40 overlap each other and the step is large. In some cases, the bent thin portion 56 may be cracked or broken.

  Therefore, in the battery A, the boundary portion 54 and the positive electrode outer end 40 are positioned at different circumferential positions of the electrode group 22 so as not to overlap each other, and when the electrode group 22 is inserted, a crack or breakage occurs in the thin portion 56. As a result, the electrical resistance of the negative electrode 26 increases due to the cracked or broken portion, and the internal resistance increases, or the cracked or broken portion breaks through the separator 28 and contacts the positive electrode 24 to cause a short circuit. It is prevented.

  In the battery A, since the length Xd of the thin portion 56 is in the range of 2.5 times to 3.8 times the inner diameter d of the outer can 10, higher capacity and cycle characteristics are further improved. It is definitely compatible.

  As described above, in the battery A, the boundary 54 between the positive electrode outer end 40 and the negative electrode 26 does not overlap with each other when viewed in the radial direction of the electrode group 22. 52 is positioned. Therefore, in any case, although it is partial, when the positive electrode 24 is not disposed outside the main body 52 as schematically shown in FIG. 5, or when the thin-walled portion 56 is schematically shown as shown in FIG. The positive electrode 24 may be disposed on both sides. In these cases, there is an excess or deficiency in the amount of the hydrogen storage alloy that contributes to the battery reaction with the positive electrode, and the balance between the increase in capacity and the cycle characteristics may be lost. Therefore, in the battery A, the length Xd of the thin portion 56 is set in the range of 2.5 to 3.8 times the inner diameter d of the outer can 10, so that the amount of hydrogen storage alloy is excessive or insufficient. Therefore, high capacity and cycle characteristics are more reliably achieved. In FIG. 5 and FIG. 6, the separator 28 is omitted.

Furthermore, in the battery A, since the inclination angle θ at the boundary portion 54 in the longitudinal direction of the negative electrode 26 is within the range of 0 ° <θ <10 °, a short circuit and an increase in internal resistance are further caused. It is definitely prevented.
In the boundary portion 54 where the thickness changes, compared to the main body portion 52 and the thin portion 56 each having a constant thickness, stress is locally concentrated at the time of winding, and the strength is likely to be insufficient. Therefore, by making the change in thickness so that the inclination angle θ falls within the range of 0 ° <θ <10 °, stress concentration is prevented and insufficient strength of the boundary portion 54 is eliminated. The occurrence of cracks and breaks in the boundary portion 54 is suppressed. As a result, in the battery A, not only in the case of the thin-walled portion 56, the boundary portion 54 is cracked or broken to increase the internal resistance, or the cracked or broken portion breaks through the separator 28 and contacts the positive electrode 24. Short-circuiting is also prevented.

The present invention is not limited to the above-described embodiment and can be variously modified. For example, in the thin portion 56, only the outer alloy layer 50 is not made thinner than the main body portion 52, but the inner portion Both outer alloy layers 48 and 50 may be thinned.
Then, instead of the sheet-like negative electrode core 46 having a through hole, a substrate having a porous structure as in the case of the positive electrode 24, for example, a foamed nickel substrate may be used for the negative electrode core. The hydrogen storage alloy layer is held by the negative electrode core in a state in which the framework of the foamed nickel base material extends in a network shape in the hydrogen storage alloy layer.

  Further, in the above-described embodiment, the inclination angle θ falls within a predetermined range in order to prevent the occurrence of cracks and the like in the boundary portion 54, but instead of or in addition to this, A negative electrode core in which the mass per unit area is larger at the boundary portion 54 than at the main body portion 52 and the thin portion 56 and the boundary portion 54 is reinforced may be used. More specifically, as shown in FIG. 7, the negative electrode core 60 in which the number of the through holes 58 is reduced at the boundary portion 54 compared to the main body portion 52 and the thin portion 56 to reduce the opening area of the through holes 58, As shown in FIG. 8, a negative electrode core 62 that is thicker at the boundary portion 54 than at the main body portion 52 and the thin portion 56 may be used. Or you may use the negative electrode core which made the diameter of the through-hole smaller in the boundary part 54 rather than the main-body part 52 and the thin part 56. FIG.

Examples 1-4, Comparative Example 1
1. Assembling of batteries As Examples 1 to 4 and Comparative Example 1, 100 AA-sized cylindrical nickel metal hydride secondary batteries having the configurations shown in FIGS. 1 to 4 were assembled.
Here, Table 1 is included in the negative electrodes 26 of Examples 1 to 4 and Comparative Example 1 per unit volume of the main body portion 52 and the thin portion 56, and the inner and outer alloy layers 48 and 50 of the main body portion 52. When the hydrogen storage alloy amount is 100, the hydrogen storage alloy amount included per unit volume of the inner and outer alloy layers 48 and 50 of the thin portion 56 is shown.

2. Battery cycle characteristic evaluation test Internal resistance (AC-IMP) and mass measurement For each of the obtained cylindrical nickel-hydrogen secondary batteries of Examples 1 to 4 and Comparative Example 1, initial charge and discharge were performed, and the battery mass was measured. . Next, each of these batteries was charged with ΔV at a current value of 1 It and then rested for 1 hour, and charging / discharging was performed until the battery voltage reached 1.0 V at a current value of 1 It. Discharging was performed 300 cycles. Then, after discharging at the 300th cycle, the internal resistance (mΩ) is measured for each battery at AC (1 kHz), the battery mass at this time is measured, and the difference from the previously measured battery mass is obtained and charged. The reduction amount (mg) of the battery mass (electrolytic solution) due to the discharge cycle was determined. The average value per 100 of these results is shown in Table 1.

From Table 1, the following is clear.
The thickness of the thin portion 56 is smaller than that of the main body portion 52, and the amount of hydrogen storage alloy contained per unit volume of the inner and outer alloy layers 48, 50 of the main body portion 52 is smaller than the inner and outer alloy layers 48, 50. In Examples 1 to 4, which are smaller than the amount of hydrogen storage alloy contained per unit volume, the internal resistance and the mass are larger than those of Comparative Example 1 in which the amounts of hydrogen storage alloy contained per unit volume of the main body 52 and the thin portion 56 are equal. Both reductions are good.

1 is a partially cutaway perspective view of a cylindrical nickel-metal hydride secondary battery according to an embodiment of the present invention. It is a cross-sectional view of the battery of FIG. It is the perspective view which expanded and showed the negative electrode used for the battery of FIG. It is a side view of the negative electrode of FIG. It is a schematic diagram of the electrode group for demonstrating the circumferential direction positional relationship of a positive electrode outer end and a negative electrode boundary part. It is a schematic diagram of the electrode group for demonstrating the circumferential direction positional relationship of a positive electrode outer end and a negative electrode boundary part. It is a top view of the negative electrode core used for the cylindrical nickel hydride secondary battery which concerns on other embodiment of this invention. It is sectional drawing of the negative electrode core used for the cylindrical nickel hydride secondary battery which concerns on other embodiment of this invention.

Explanation of symbols

26 Negative electrode 46 Negative electrode core body 48 Inner hydrogen storage alloy layer 50 Outer hydrogen storage alloy layer 52 Main body portion 54 Boundary portion 56 Thin portion

Claims (7)

A conductive cylindrical outer can;
The outer can is housed together with an alkaline electrolyte, and a negative electrode including a strip-shaped negative electrode core, an active material layer held on the negative electrode core, and a positive electrode are swirled so that the negative electrode is positioned on the outermost periphery through a separator. A cylindrical alkaline storage battery comprising an electrode group wound in a shape and having an outermost peripheral portion made of the negative electrode in contact with a peripheral wall of the outer can and disposed outside the outer end of the positive electrode through the separator In
The negative electrode is
A main body wound inside the electrode group;
Wound as the outermost peripheral part of the electrode group, compared with the main body part, the thickness of the active material layer is thin and a thin part with a large amount of active material contained per unit volume of the active material layer,
A cylindrical alkaline storage battery characterized by having a boundary portion formed between the main body portion and the thin-walled portion and changing the thickness of the active material layer in the longitudinal direction of the negative electrode core.   The amount of active material contained per unit area of the active material layer of the thin-walled portion is 40% to 75% of the amount of active material contained per unit area of the active material layer of the main body portion. Item 2. The cylindrical alkaline storage battery according to Item 1. The negative electrode core is made of a punching metal,
The active material layer is held on both sides of the negative electrode core,
3. The cylindrical shape according to claim 1, wherein an active material layer held inside the negative electrode core is thicker than an active material layer held outside the negative electrode core in the thin portion. Alkaline storage battery.   4. The cylindrical alkaline storage battery according to claim 1, wherein an outer end of the positive electrode and a boundary portion of the negative electrode are positioned at different circumferential positions of the electrode group. 5.   The cylindrical alkaline storage battery according to any one of claims 1 to 4, wherein a length of the thin portion is 2.5 to 3.8 times an inner diameter of the outer can.   The cylindrical alkaline storage battery according to any one of claims 1 to 5, wherein an inclination angle of the active material layer in the boundary portion is more than 0 degree and less than 10 degrees.   The cylindrical shape according to any one of claims 1 to 6, wherein a mass per unit area of the negative electrode core body in the boundary portion is larger than a mass per unit area of the negative electrode core body in the main body portion. Alkaline storage battery.

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