JP2007005196A - Alkaline battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an alkaline battery capable of surely preventing leak of electrolytic solution even during preservation for a long period of time. <P>SOLUTION: The alkaline battery is provided with an outer package can 1 opening at an upper end, a polyamide-based resin sealing body 7 sealing an open upper end part 1a of the outer package can 1, an anode collecting rod 6 plugged into the outer package can 1 in a state inserted into an insertion hole 11 fitted to the sealing body 7, and alkaline electrolytic solution contained in the outer package can 1. The sealing body 7 is molded so that a gate part 19 is positioned on a top face of the sealing body 7. The surroundings of a lower end part of the insertion hole in the sealing body 7 are covered with a sealant 17 stable against the alkaline electrolytic solution. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an alkaline battery that hardly causes leakage of an electrolyte even after long-term storage.

  Patent Documents 1 to 4 include a resin-made sealing body that seals the upper end of the opening of the cylindrical outer can, and a current collecting rod that is inserted into the outer can in a state of being inserted through the insertion hole in the central portion of the sealing body. An alkaline battery having an electrolyte solution contained in an outer can is disclosed.

  Further, in Patent Document 2, a sealing agent is interposed between the inner peripheral surface of the insertion hole of the sealing body and the outer peripheral surface of the current collector rod in order to prevent leakage of the electrolytic solution. The current collector rod is inserted into the insertion hole of the sealing body after the entire body is covered with a surfactant film.

JP-A-6-325768 (FIGS. 1 and 4) Japanese Patent Laid-Open No. 7-45261 (FIG. 1-2) Japanese Patent Laying-Open No. 2002-198815 (paragraph numbers 0018-0019, FIG. 1) Japanese Patent Laying-Open No. 2004-134168 (FIG. 1)

  When the sealing body is molded, the molten resin is injected into the cavity of the mold through the gate. The molded sealing body has a molten resin injection part (gate portion) and the periphery thereof for molding. The accompanying residual stress is withheld. For this reason, cracks (fissures) are likely to occur around the gate portion. As a countermeasure, as shown in Patent Document 4, a sealant is arranged around the gate portion and the gate portion so that even if a crack occurs, the crack is closed with the sealant. Are known.

  In Patent Document 4, the gate portion is located in the vicinity of the lower end portion of the insertion hole, and therefore residual stress is retained in the vicinity of the lower end portion of the insertion hole. In this insertion hole, the current collecting rod is press-fitted in order to improve the adhesion to the current collecting rod, and since the current collecting rod is inserted from the upper side of the insertion hole, a stress is applied around the lower end of the insertion hole. Concentration occurs. That is, in Patent Document 4, the residual stress overlaps with the stress concentration, and a large stress is generated around the lower end portion of the insertion hole.

  As the resin forming the sealing body, a polyamide resin is selected from the viewpoints of liquid leakage resistance and mechanical strength. However, the polyamide resin is easily dehydrated and embrittled over time, and has strong alkaline electrolysis. Since the liquid embrittles over time, the sealing body is liable to cause fine cracks when the battery is stored for a long time.

  For this reason, in patent document 4, when a battery is stored for a long time, there exists a possibility that a big crack may arise in a sealing body combined with the said stress. In this case, the crack cannot be sufficiently blocked by the sealant.

  Accordingly, an object of the present invention is to provide an alkaline battery that can reliably prevent leakage of an electrolyte even when stored for a long period of time.

  As shown in FIGS. 1 and 2, the present invention includes an outer can 1 having an upper end opened, a resin sealing body 7 that seals the upper end of the outer can 1, and an insertion hole 11 provided in the sealing body 7. It has a current collecting rod 6 inserted into the outer can 1 in the inserted state, and an electrolyte solution accommodated in the outer can 1, and the sealing body 7 has a molten resin injection portion 19 on the upper surface of the sealing body 7. The sealing agent 17 which is stable with respect to electrolyte solution covers the periphery of the lower end part of the insertion hole 11 in the sealing body 7. The current collecting rod 6 may be a negative electrode current collecting rod or a positive electrode current collecting rod.

  Specifically, the lower end portion of the insertion hole 11 of the sealing body 7 has an inner diameter larger than that of the intermediate portion of the insertion hole 11, so that the non-contact portion 16 that does not contact the current collector rod 6 is removed from the lower surface of the sealing body 7. The sealant 17 covers the periphery of the lower end portion of the insertion hole 11 including the inside of the non-contact portion 16.

  The sealing agent 17 is preferably a pitch-based sealing agent from the viewpoints of low cost, ease of application, less impurities, and no residual stress due to application.

  The thickness of the sealant 17 is preferably 10 μm or more. If the thickness dimension of the sealant 17 is smaller than 10 μm, the generated crack cannot be reliably covered with the sealant 17. Although it is preferable that the thickness of the sealant 17 is large, the cost increases as the sealant 17 is increased, and the internal capacity of the battery is reduced by the amount of the sealant 17.

  According to the present invention, since the sealing body 7 is molded so that the molten resin injection portion 19 is located on the upper surface of the sealing body 7, the residual stress accompanying the molding of the sealing body 7 is caused by the lower end portion of the insertion hole 11. It is prevented from being held around. Therefore, the residual stress overlaps with the stress concentration generated around the lower end of the insertion hole 11 when the current collecting rod 6 is press-fitted from the upper side of the insertion hole 11, so that a large stress is generated around the lower end of the insertion hole 11. Is reduced, and a large crack is less likely to occur around the lower end portion of the insertion hole 11 accordingly.

  In addition, since the periphery of the lower end portion of the insertion hole 11 of the sealing body 7 is covered with the sealant 17, even if a certain amount of cracks are generated by storing the battery for a long period of time, the cracks can be reliably secured with the sealant 17. Can be blocked. Therefore, leakage of the electrolytic solution can be reliably prevented. Further, since the molten resin injection portion 19 is located on the upper surface of the sealing body 7, the residual stress is retained and the electrolyte does not come into contact with the molten resin injection portion 19 which is liable to generate cracks. It becomes difficult to occur.

  When the non-contact portion 16 is recessed from the lower surface of the sealing body 7 upward, the contact area between the current collector rod 6 and the insertion hole 11 is reduced by the amount of the non-contact portion 16 provided, and the press-fitting In this case, the contact resistance between the current collecting rod 6 and the insertion hole 11 is reduced. As a result, the occurrence of cracks around the lower end of the insertion hole 11 is further reduced.

(Example 1) The drawing shows Example 1 in which the present invention is applied to an AA alkaline battery (hereinafter simply referred to as a battery). As shown in FIG. 2, the battery is arranged in a bottomed cylindrical outer can 1 having an open upper end, a hollow cylindrical positive electrode 2 accommodated in the outer can 1, and a hollow portion of the positive electrode 2. Separator 3, a negative electrode 5 filled in the separator 3, a nail-shaped negative electrode current collector rod 6 inserted into the negative electrode 5, and an alkaline electrolyte mainly composed of an aqueous potassium hydroxide solution. The opening upper end 1 a side of the outer can 1 is sealed with a sealing body 7. A convex positive terminal portion 1 b is formed on the bottom of the outer can 1. The outer can 1 also serves as a positive electrode terminal.

  In the opening upper end 1a of the outer can 1, the sealing body 7, a metal negative electrode terminal plate 9 disposed on the upper opening of the outer can 1 through this, and the opening upper end 1a of the outer can 1 are provided. A flanged short cylindrical insulating plate 10 interposed between the tip and the negative terminal plate 9 is mounted. The insulating plate 10 is made of a highly insulating synthetic resin. The sealing body 7 is formed of a polyamide-based resin such as nylon 6 or nylon 66.

  The outer can 1 is formed of a killed steel plate and has an outer surface plated with a dull nickel plating. The outer can 1 has an opening upper end 1a having a thickness of 0.25 mm and a barrel having a thickness of 0.16 mm. The thickness dimension of the positive electrode terminal portion 1b of the outer can 1 is made thicker than the body portion, and the positive electrode terminal portion 1b is difficult to be dented even if the battery is accidentally dropped.

  The positive electrode 2 is made of 87.6: 6. Manganese dioxide, graphite, polytetrafluoroethylene powder, and 56 mass% potassium hydroxide aqueous solution (electrolytic solution) containing only 2.9 mass% of zinc oxide. It was formed with a positive electrode mixture prepared by mixing in a temperature environment of 50 ° C. at a mass ratio of 7: 0.2: 5.5. Separator 3 was formed into a cup shape in which the nonwoven fabric was stacked in three layers, wound in a cylindrical shape, bent at the bottom, and then heat-sealed to form a cup with the bottom closed.

  The negative electrode 5 is composed of a zinc alloy particle, sodium polyacrylate (sodium polyacrylate), polyacrylic acid, and a 33.5 mass% potassium hydroxide aqueous solution (electrolyte) containing 2.2 mass% of zinc oxide. ) With a mass ratio of 39: 0.2: 0.2: 18 to form a negative electrode mixture prepared in a gel form. The negative electrode current collecting rod 6 is formed by plating tin on brass.

  As shown in FIGS. 1 and 3, the sealing body 7 includes a boss portion 12 having an insertion hole 11 through which the negative electrode current collector rod 6 is inserted, an outer peripheral portion 13 in contact with the inner peripheral surface of the outer can 1, and the boss portion 12. It is comprised by the connection part 15 which connects the outer peripheral part 13 and seals between them. The sealing body 7 prevents leakage of the electrolytic solution to the outside, and insulates the negative electrode terminal plate 9 and the outer can 1 together with the insulating plate 10. The diameter of the boss 12 is 3 mm, and the diameter of the negative electrode current collector 6 is 1.45 mm.

  A thin-walled portion 15a as an explosion-proof safety valve is formed on the inner peripheral side of the connecting portion 15 of the sealing body 7, and the thin-walled portion 15a breaks when the internal pressure of the battery becomes an abnormal level or more. The internal pressure of is released. A stress absorbing portion 15b is formed on the outer peripheral side of the connecting portion 15 of the sealing body 7, and a part of the stress acting on the connecting portion 15 when the upper end portion 1a of the outer can 1 is caulked and sealed. The stress absorbing portion 15b absorbs to prevent stress concentration on the thin portion 15a.

  The outer diameter of the rod-shaped portion 6 a of the negative electrode current collector rod 6 is larger than the inner diameter of the insertion hole 11 of the sealing body 7, and the rod-shaped portion 6 a of the negative electrode current collector rod 6 is press-fitted into the insertion hole 11. Specifically, (the outer diameter L1 of the rod-shaped portion 6a) / (the inner diameter L2 of the insertion hole 11) is set within a range of 1.01 to 1.05. When L1 / L2 is smaller than 1.01, the adhesiveness between the rod-shaped portion 6a of the negative electrode current collecting rod 6 and the inner peripheral surface of the insertion hole 11 of the sealing body 7 is lowered, and liquid leakage is likely to occur. When L1 / L2 is larger than 1.05, the rod-shaped portion 6a of the negative electrode current collector rod 6 is excessively pressed against the inner peripheral surface of the insertion hole 11 of the sealing body 7, and the boss portion 12 of the sealing body 7 is pressed. Cracks are likely to occur.

  The inner diameter of the upper end portion 11 a of the insertion hole 11 of the sealing body 7 is larger than the intermediate portion of the insertion hole 11, and when the negative electrode current collector rod 6 is press-fitted into the insertion hole 11, the larger diameter of the upper end portion of the negative electrode current collector rod 6. The portion 6b is fitted into the upper end portion 11a of the insertion hole 11 in a state in which the portion 6b slightly protrudes from the upper surface of the boss portion 12 or is substantially flush therewith. The large diameter portion 6b of the negative electrode current collector rod 6 is joined to the back surface of the central portion of the negative electrode terminal plate 9 by spot welding or the like.

  The lower end portion of the insertion hole 11 of the sealing body 7 has an inner diameter larger than that of the intermediate portion of the insertion hole 11, so that the non-contact portion 16 that does not contact the negative electrode current collector rod 6 extends upward from the lower surface of the boss portion 12. It is recessed and formed. The non-contact part 16 is formed from the lower surface of the boss part 12 to a height position of 0.7 mm. The upper end portion of the non-contact portion 16 is curved in an arc shape as shown in FIG. 3, and is connected to the middle portion of the insertion hole 11 in an obtuse angle shape. The non-contact portion 16 only needs to have a height of 0.5 mm or more from the lower surface of the boss portion 12.

  The contact area between the negative electrode current collector rod 6 and the insertion hole 11 is reduced by the amount of the non-contact portion 16 provided, and the contact resistance between the negative electrode current collector rod 6 and the insertion hole 11 during the press-fitting is reduced. In addition, since the upper end portion of the non-contact portion 16 is connected to the middle portion of the insertion hole 11 in an obtuse shape, stress concentration on the lower end of the insertion hole 11 is alleviated by the press-fitting.

  The lower surface of the boss part 12 and the inside of the non-contact part 16 are covered with a sealant 17 as shown in FIG. As the sealant 17, pitch-based sealants such as pitch, asphalt, tar, pine resin (rosin), etc., which are stable to alkaline electrolyte, and other fluorine-based resins are used. In Example 1, the sealant 17 used was one in which the pitch was dissolved in toluene to a concentration of 40% by weight.

  The thickness of the coating layer of the sealant 17 after drying is set to 0.1 mm. The internal space of the non-contact portion 16 is filled with a sealant 17, and the rod-shaped portion 6 a of the negative electrode current collector rod 6 is covered with the sealant 17 to the lower side of the boss portion 12. Thereby, even if a crack occurs on the lower surface of the boss portion 12 or the inner peripheral surface of the insertion hole 11, the crack is closed with the sealant 17. In addition, the thickness dimension of the sealing agent 17 should just be 10 micrometers or more.

  The sealant 17 is applied after the negative electrode current collector rod 6 is press-fitted into the insertion hole 11, but before the press-fitting, the rod-shaped portion 6 a of the negative electrode current collector rod 6, the lower surface of the boss portion 12, and the non-contact portion 16 The sealing agent 17 may be applied in advance. In this case, the sealant 17 is also interposed between the rod-shaped portion 6 a of the negative electrode current collector rod 6 and the inner peripheral surface of the intermediate portion of the insertion hole 11 of the sealing body 7.

  The gate for injecting the molten resin into the mold cavity in the molding of the sealing body 7 is set so as to be positioned on the upper surface of the sealing body 7. In other words, the sealing body 7 is located on the inner bottom surface of the upper end portion 11 a of the insertion hole 11 where the molten resin injection portion (gate portion) 19 is the upper surface of the sealing body 7. Note that the gate portion 19 is slightly lower than or substantially flush with the inner bottom surface of the upper end portion 11a of the insertion hole 11.

Next, the manufacturing procedure of the battery will be described. The positive electrode 2 in a state where three hollow cylindrical positive electrode mixture molded bodies are stacked is accommodated in the outer can 1 by inserting an appropriate amount of the positive electrode mixture into the outer can 1 and performing pressure molding in order. . The weight of the positive electrode 2 is about 11 g, and each positive electrode mixture molded body has a density of 3.21 g / cm ³ . On the inner surface of the outer can 1, a groove is formed at a position of 3.5 mm downward from the upper end of the opening of the outer can 1, and a pitch is applied to the inner surface of the outer can 1 up to this groove position.

  Next, the cup-shaped separator 3 is loaded inside the positive electrode 2, and 1.35 g of an electrolytic solution of 33.5 wt% potassium hydroxide aqueous solution containing 2.2 wt% of zinc oxide is added to the separator 3. Inject inside. Next, 5.74 g of the gelled negative electrode mixture is filled inside the separator 3 to form the negative electrode 5.

  After that, the negative electrode current collector rod 6 is press-fitted into the insertion hole 11, and the sealing body 7 in a state where the sealant 17 is applied is mounted in the upper open end 1a of the outer can 1, and the negative electrode current collector rod 6 is 5 is inserted. Furthermore, the negative electrode terminal plate 9 and the insulating plate 10 are mounted in the upper open end 1a of the outer can 1.

  In this state, the upper open end 1a of the outer can 1 is caulked from the outside by a spinning method, and the large-diameter portion 6b of the negative electrode current collector rod 6 is joined to the back surface of the negative electrode terminal plate 9 by spot welding or the like. A battery is produced.

Example 2 In Example 2, a fluorine-based resin was applied as the sealant 17 to the lower surface of the boss portion 12 and the non-contact portion 16. The thickness dimension of the fluorine resin coating layer was set to 0.05 mm. Since the other points are the same as those of the first embodiment, description thereof is omitted.

Comparative Example 1 In Comparative Example 1, nothing was applied to the lower surface of the boss portion 12 and the non-contact portion 16. Since the other points are the same as those of the first embodiment, description thereof is omitted.

(Leakage performance test) To prepare 75 batteries according to Examples 1 and 2 of the present invention and 75 batteries according to Comparative Example 1, respectively, in order to accelerate and discriminate the leakage performance due to long-term storage And stored in a temperature environment of 60 ° C.

  Then, 15 batteries each of the batteries according to Examples 1 and 2 and the battery according to Comparative Example 1 were obtained immediately after the battery production, after 15 days of storage, after 30 days of storage, after 45 days of storage and after 60 days of storage. Each was arbitrarily extracted and disassembled, and the presence or absence of cracks in the boss portion 12 of the sealing body 7 was visually confirmed. Table 1 shows the results. The 60-day storage corresponds to about 9 years of storage under normal circumstances.

  As shown in Table 1, the battery of Example 1 did not show any cracks after 60 days of storage and the battery of Example 2 after 45 days of storage, and the electrolyte leaked out even after long-term storage. It was confirmed that no occurred.

  On the other hand, in the battery of Comparative Example 1, generation of cracks was observed in 7 batteries after 60 days storage and in 2 batteries even after 45 days storage. In the battery of Example 2, cracks were observed in three batteries after 60 days of storage, but the number was less than half that of the battery of Comparative Example 1. That is, the battery of Comparative Example 1 has a higher possibility of leakage of the electrolyte than the batteries of Examples 1 and 2 during long-term storage.

The longitudinal cross-sectional view which shows the principal part of the alkaline battery of this invention Longitudinal sectional view showing the entire alkaline battery Longitudinal section of the sealing body

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exterior can 1a Opening upper end part 6 Negative electrode current collecting rod 7 Sealing body 9 Negative electrode terminal board 10 Insulating board 11 Insertion hole 11a Upper end part 12 Boss part 16 Non-contact part 17 Sealant 19 Gate part

Claims (4)

An outer can whose upper end is open, a resin sealing body that seals the upper end of the opening of the outer can, a current collecting rod that is inserted into the outer can in a state of being inserted into an insertion hole provided in the sealing body, and Having an electrolyte contained in an outer can,
The sealing body is shaped such that the molten resin injection portion is located on the upper surface of the sealing body,
An alkaline battery characterized in that a sealant that is stable with respect to the electrolytic solution covers a periphery of a lower end portion of the insertion hole in the sealing body. The lower end portion of the insertion hole of the sealing body has a larger inner diameter than the middle portion of the insertion hole, so that a non-contact portion that does not contact the current collector rod is recessed upward from the lower surface of the sealing body. Formed,
The alkaline battery according to claim 1, wherein the sealant covers a periphery of a lower end portion of the insertion hole including the inside of the non-contact portion.   The alkaline battery according to claim 1, wherein the sealant is a pitch sealant.   The alkaline battery according to claim 3, wherein a thickness dimension of the sealant is 10 μm or more.

Images