JP5655808B2 - Cylindrical alkaline storage battery - Google Patents

Description

  The present invention relates to a cylindrical alkaline storage battery, and more particularly to improvement of a separator.

  Cylindrical alkaline storage batteries are widely used as power sources for portable electronic devices such as portable terminals and digital still cameras, hybrid vehicles, and backup devices.

  A cylindrical alkaline storage battery includes a battery case, an electrode group, a sealing plate, a positive electrode lead, an insulating ring, and the like. The battery case is a cylindrical container that is open at one end in the longitudinal direction, and accommodates an electrode group and the like therein. The electrode group is a wound electrode group obtained by winding a positive electrode plate and a negative electrode plate through a separator. The sealing plate seals the opening of the battery case. In the positive electrode, a conductive substrate having a three-dimensional network structure is filled with a mixture containing an active material such as nickel hydroxide. The positive electrode lead is fixed to the positive electrode conductive substrate by welding or the like, and makes the positive electrode plate and the sealing plate of the electrode group conductive. In the negative electrode plate, a mixture containing a hydrogen storage alloy is applied to a conductive substrate such as punching metal. The separator uses an insulating nonwoven fabric or sheet mainly composed of polypropylene or the like, and insulates the positive electrode and the negative electrode and holds an electrolytic solution that mediates a reaction between the positive and negative electrodes. The insulating ring is mounted between the electrode group and the sealing plate in the battery case, and mainly insulates and protects the battery case, the electrode group, and the positive electrode lead.

  In this type of cylindrical alkaline storage battery, various proposals have been made for the purpose of preventing a short circuit. For example, the inner surface of the separator disposed between the outer surface of the positive electrode plate and the inner surface of the negative electrode plate to prevent the positive electrode plate and the negative electrode plate from being short-circuited due to flash or cracks of the positive electrode plate when the electrode group is wound. It has been proposed to adopt a configuration in which an auxiliary separator is interposed between the two (for example, see Patent Document 1).

JP 2005-56676 A

  However, since a battery having a conventional structure has a uniform liquid retaining property over the entire separator including the auxiliary separator for the purpose of preventing a short circuit, this auxiliary separator also holds the electrolytic solution in the same manner as the other separators. The upper limit of the amount of electrolyte that can be injected into the battery is determined by the internal volume of the battery case, the volume of the electrode group material, and the volume of built-in components such as the insulating ring, The amount of electrolyte solution that can be held by the separators in other parts is relatively small. As a result, the electrolyte solution is taken into the active material of the positive electrode plate and negative electrode plate that deteriorates during repeated charging and discharging, so that the electrolyte solution present in the separator between the positive and negative electrode plates is reduced and the battery life is sufficiently secured. There was a problem that it would be impossible.

  The present invention solves the above-described problems, and an object of the present invention is to provide a cylindrical alkaline storage battery that prevents short circuit and has high charge / discharge cycle life performance.

In order to achieve the above object, a cylindrical alkaline storage battery of the present invention has a cylindrical shape composed of an electrode group obtained by winding a strip-like positive electrode plate and a negative electrode plate with a separator interposed therebetween, an electrolytic solution, and a battery case containing them. In the battery, the first separator disposed between the outer surface of the positive electrode plate and the inner surface of the negative electrode plate of the electrode group, the second separator disposed on the inner surface of the positive electrode plate and the outer surface of the negative electrode plate, and the electrode group A third separator is disposed between the positive electrode plate and the negative electrode plate on the winding end side, and the liquid retention ratio is smaller than the liquid retention ratio of the first separator and the second separator. By arranging the third separator having a smaller liquid retention rate than the first separator and the second separator, the electrolyte solution necessary for the reaction is not unevenly distributed in the outermost peripheral portion, and is interposed in the entire area between the positive electrode plate and the negative electrode plate. It becomes possible to make it.

  The cylindrical alkaline storage battery of the present invention includes a first separator disposed between the outer surface of the positive electrode plate of the electrode group and the inner surface of the negative electrode plate, and a second separator disposed on the inner surface of the positive electrode plate and the outer surface of the negative electrode plate. By disposing a third separator that is disposed between the separator and the positive electrode plate and the negative electrode plate on the winding end side of the electrode group and whose liquid retention is smaller than the liquid retention of the first separator and the second separator, Short circuit due to flashing and cracking of the positive electrode plate in the outermost peripheral portion can be suppressed, and the electrolyte is retained throughout the separator between the positive and negative electrode plates by suppressing the retention of the electrolyte in the third separator. Therefore, when charging / discharging is repeated, electrolyte depletion in the separator between the positive electrode plate and the negative electrode plate hardly occurs. Therefore, the cylindrical alkaline storage battery of the present invention has the characteristics that the occurrence of short circuit is small and the charge / discharge cycle life performance is excellent.

The partially cutaway perspective view showing the configuration of the cylindrical alkaline storage battery of the present invention The top view which simplifies and shows the structure of the electrode group which is one embodiment of this invention The top view which simplifies and shows the structure of the electrode group which is one embodiment of this invention The enlarged view which shows one form of a structure of the electrode group of a winding end part The enlarged view which shows one form of a structure of the electrode group of a winding end part

  According to a first aspect of the present invention, there is provided a cylindrical alkaline storage battery comprising an electrode group obtained by winding a strip-like positive electrode plate and a negative electrode plate with a separator interposed therebetween, an electrolyte, and a battery case in which these are housed. A first separator disposed between the outer surface of the positive electrode plate and the inner surface of the negative electrode plate, a second separator disposed between the inner surface of the positive electrode plate and the outer surface of the negative electrode plate, and the end of winding of the electrode group A cylindrical alkaline storage battery in which a third separator that is disposed between a positive electrode plate and a negative electrode plate on the side and has a liquid retention rate smaller than that of the first separator and the second separator is disposed. . According to this structure, the short circuit by the flash and crack of a positive electrode plate in an outermost peripheral part can be suppressed. Moreover, since electrolyte solution is hold | maintained over the whole separator between the electrode plates of a positive / negative electrode by suppressing the retention of the electrolyte solution to a 3rd separator, when repeating charge / discharge, a positive electrode plate and a negative electrode plate In the meantime, the electrolyte in the separator is hardly depleted, and the charge / discharge cycle life performance can be improved.

  The second aspect of the present invention is characterized in that the liquid retention rate of the third separator is less than half the liquid retention rate of the first separator and the second separator. By setting the liquid retention rate of the third separator to less than half that of the first separator and the second separator, excessive electrolyte retention in the third separator is suppressed, and the electrolyte is distributed unevenly throughout the electrode group. It becomes possible to arrange.

According to a third aspect of the present invention, when the liquid retention ratio of the first separator and the second separator is 100, the liquid retention ratio of the third separator is 20 to 50. By setting the liquid retention rate of the third separator to 50 (half) or less, it is possible to suppress excessive electrolyte solution retention and obtain better cycle life characteristics. However, if the liquid retention rate is too low, This is not preferable because a reaction resistance occurs in a portion where the separator exists, and the high rate discharge characteristics are affected. Therefore, the liquid retention rate of the third separator is more preferably in the range of 20-50.

  According to a fourth aspect of the present invention, the third separator has a length corresponding to one turn of the outermost periphery of the electrode group. When the electrode group is wound, the electrode group is wound while being pressed by a pressure roller so as not to exceed the diameter that can be inserted into the battery case. As the winding is nearing the end of winding, pressure is applied strongly to suppress the electrode group diameter. For this reason, the separator in the outermost peripheral portion is strongly compressed, and the occurrence of a short circuit between the positive electrode plate and the negative electrode plate in this portion is often observed. By setting the length of the third separator to the length of one turn at the outermost periphery, it is possible to prevent a short circuit that occurs at the outermost periphery. However, although the length of the third separator may slightly exceed one turn, the group diameter of the electrode group increases if it is configured to enter more than 1/4 turn into the inner periphery of the electrode group. Since it becomes difficult to insert an electrode group in a battery case, it is not preferable.

  According to a fifth aspect of the present invention, the third separator is disposed between the outer surface of the first separator and the inner surface of the negative electrode plate. Due to swelling of the electrode plate during charging, the electrolyte near the positive electrode plate is more easily consumed. Therefore, by arranging a third separator having a low liquid retention rate between the outer surface of the first separator and the inner surface of the negative electrode plate, uneven distribution of the electrolyte solution in the vicinity of the positive electrode plate is suppressed, and better cycle life performance is achieved. Can be obtained.

  A cylindrical alkaline storage battery according to an embodiment of the present invention will be described below with reference to the accompanying drawings. As shown in FIG. 1, the cylindrical alkaline storage battery of the present invention includes a cylindrical battery case 4 that is open at one end in the longitudinal direction, and includes a positive electrode plate 1, a negative electrode plate 2, and a first separator 9. The electrode group composed of the second separator 10 and the third separator 11 and an electrolyte solution are accommodated. The battery case 4 has conductivity and functions as a negative electrode terminal. The sealing plate 6 is provided with a rubber or spring safety valve 7 at the center, and is fixed to the opening of the battery case 4 via an insulating resin packing. The positive electrode lead 8 is fixed to the conductive substrate of the positive electrode plate 1 by welding or the like, and makes the positive electrode plate 1 and the sealing plate 6 of the electrode group conductive. The insulating ring 5 is mounted between the electrode group and the sealing plate 6 in the battery case 4 and mainly insulates and protects the battery case 4 from the electrode group and the positive electrode lead 8. The bottom insulating plate 3 is disposed on the bottom surface of the battery case 4 and insulates and protects the electrode group.

  In the positive electrode plate 1, a conductive base material having a three-dimensional network structure is filled with a positive electrode mixture. The positive electrode mixture includes, for example, a positive electrode active material, a binder, a thickener, and the like.

  Although it does not specifically limit as a positive electrode active material, Nickel hydroxide etc. which surface-coated cobalt hydroxide etc. can be mention | raise | lifted, such as nickel hydroxide which dissolved solid cobalt and zinc.

  The binder may be either a thermoplastic resin or a thermosetting resin. Specific examples of the binder include styrene-butadiene copolymer rubber (SBR), polyethylene, polypropylene, polytetrafluoroethylene, and the like.

  Examples of the thickener include those capable of imparting viscosity to the positive electrode mixture slurry. Examples of the thickener include carboxymethyl cellulose and modified products thereof, polyvinyl alcohol, methyl cellulose, and polyethylene oxide.

  After the slurry of the positive electrode mixture is prepared, the conductive base material having a three-dimensional network structure is filled and dried, and the thickness is adjusted by passing through a rolling roll having a predetermined pressure and gap. Thereafter, it is cut into a predetermined size, the positive electrode mixture is removed from a part of the upper end surface of the electrode plate by ultrasonic peeling or the like, and the positive electrode lead 8 having conductivity is welded.

  In the negative electrode plate 2, a negative electrode mixture is applied to a punching metal base material in which holes are periodically provided in a conductive steel plate. A negative electrode mixture consists of a negative electrode active material, a electrically conductive agent, a binder, a thickener, etc., for example.

  Examples of the negative electrode active material include hydrogen storage alloys and cadmium that can store and release hydrogen.

  The conductive agent is not particularly limited except that it is a material having electron conductivity, and various electron conductive materials can be used. Specifically, for example, graphite such as natural graphite (such as flake graphite), artificial graphite, and expanded graphite, for example, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black Can be used.

  The binder serves to bind the hydrogen storage alloy powder or the conductive agent to the current collector. The binder may be either a thermoplastic resin or a thermosetting resin. Specific examples of the binder include styrene-butadiene copolymer rubber (SBR), polyethylene, polypropylene, polytetrafluoroethylene, and the like.

  As the thickener, those capable of imparting viscosity to the negative electrode mixture paste, for example, carboxymethylcellulose and modified products thereof, polyvinyl alcohol, methylcellulose, polyethylene oxide and the like can be used.

  After preparing the negative electrode mixture paste, it is applied to a punching metal, dried, and passed through a rolling roll having a predetermined pressure and gap to adjust the thickness. Thereafter, it is cut into a predetermined dimension.

The 1st separator 9 and the 2nd separator 10 consist of a nonwoven fabric or a sheet-like film which entangled the fiber which uses polypropylene and polyethylene as a raw material. As these separators, those whose basis weight (weight per unit area) is adjusted from 20 g / m ² to 100 g / m ² are more preferable. Further, it is more preferable that the thickness is adjusted from 50 μm to 200 μm. These separators are subjected to a hydrophilic treatment in order to impart hydrophilicity. Examples of the hydrophilic treatment for the separator include sulfonation treatment, fluorine treatment, and plasma treatment.

  As shown in FIGS. 2 and 3, the electrode group includes a positive electrode plate 1, a negative electrode plate 2, a first separator 9 disposed between the outer surface of the positive electrode plate 1 and the inner surface of the negative electrode plate 2, the positive electrode plate 1. In a state where the second separator 10 disposed between the inner surface of the negative electrode plate 2 and the outer surface of the negative electrode plate 2 is overlapped, it is wound in a spiral shape from the central portion toward the outer periphery.

A third separator 11 is disposed in a portion covering a part or all of the outermost periphery including the end of winding of the positive electrode plate 1. The 3rd separator 11 consists of a nonwoven fabric or a sheet-like film which entangled the fiber which uses a polypropylene and polyethylene as a raw material. As these separators, those whose basis weight (weight per unit area) is adjusted from 20 g / m ² to 100 g / m ² are more preferable. Further, it is more preferable that the thickness is adjusted from 50 μm to 200 μm. These separators are subjected to a hydrophilic treatment in order to impart hydrophilicity. Examples of the hydrophilic treatment for the separator include sulfonation treatment, fluorine treatment, and plasma treatment.

The third separator 11 is characterized in that the liquid retention is smaller than that of the first separator 9 and the second separator 10. As a method of making the liquid retention rate of the third separator 11 smaller than that of the first separator 9 and the second separator 10, the porosity of the third separator 11 is adjusted by adjusting the basis weight and thickness. This can be achieved by making it smaller than the porosity of the separator 9 and the second separator 10. Further, the hydrophilic group amount on the separator is controlled by adjusting the hydrophilic treatment time and the treatment agent concentration, and the hydrophilic group amount per unit area of the third separator 11 is set to the first separator 9 and the second separator 10. By reducing the amount, the liquid retention rate can be reduced.

  According to this structure, the short circuit by the flash and crack of the positive electrode plate 1 in an outermost periphery part can be suppressed. Moreover, since electrolyte solution is hold | maintained over the whole separator between the electrode plates of a positive / negative electrode by suppressing the liquid retention of the electrolyte solution to the 3rd separator 11, when repeating charge / discharge, the positive electrode plate 1 and The electrolyte solution in the separator between the negative electrode plates 2 is hardly depleted, and the charge / discharge cycle life performance can be improved.

  As shown in FIG. 5, the third separator 11 may be disposed on the inner surface of the first separator 9, but the electrolyte near the positive electrode plate is consumed more due to electrode plate swelling during charging. Therefore, it is more preferable to dispose the first separator 9 on the outer surface as shown in FIG. 4 because better cycle life performance can be obtained.

  Further, these inventions are different from the first separator 9, the second separator 10 and the third separator 11 in that the battery further uses an auxiliary separator, for example, a winding start portion or a winding intermediate portion. Even in the battery having the configuration in which the auxiliary separator is added, the same effect can be obtained as long as the first separator 9, the second separator 10, and the third separator 11 satisfy the configuration of the invention. .

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.

Example 1
A cylindrical alkaline storage battery shown in FIG. 1 was produced. First, nickel hydroxide (positive electrode active material) whose surface was coated with a cobalt compound, polytetrafluoroethylene (binder), and carboxymethyl cellulose (thickener) were dispersed in water to prepare a positive electrode mixture slurry. This slurry was filled in a foamed nickel porous body (conductive substrate) having a three-dimensional network structure, dried and rolled to a thickness of 0.6 mm. After rolling, it was cut into a length of 43 mm and a width of 95 mm, a nickel plate to be the positive electrode lead 8 was welded, and both front and back surfaces of the welded portion were covered with a polypropylene insulating tape. The positive electrode plate 1 was obtained by the above structure.

  On the other hand, hydrogen storage alloy (negative electrode active material), carbon black (conductive agent), styrene-butadiene rubber copolymer fine particles (binder) and carboxymethylcellulose (thickener) are dispersed in water, and negative electrode mixture paste is prepared. Prepared. This paste was applied to punching metal and rolled to 0.3 mm. After rolling, the negative electrode plate 2 was produced by cutting into 43 mm length and 130 mm width.

As the separator, a nonwoven fabric having a basis weight of 55 g / m ² , a thickness of 0.12 mm, and a width of 46 mm in which fibers made of polypropylene and polyethylene are entangled was used. The liquid retention rate is measured by the method described below. A test piece 30 mm long and 30 mm wide is cut out from the separator. After measuring the weight (W) of the test piece, it is immersed in pure water for 1 hour. Next, the test piece is taken out, the weight (W1) of the test piece is measured, and the liquid retention is calculated by the following equation (1).

Liquid retention rate (%) = {(W1-W) / W} × 100 (1)
When the liquid retention rate of this nonwoven fabric separator was measured, the liquid retention rate was 150%.

Two separators having a length of 140 mm (first separator 9) and 125 mm (second separator 10) were cut out from the nonwoven fabric. On the other hand, a nonwoven fabric having a weight per unit area of 45 g / m ² , a thickness of 0.05 mm, and a width of 46 mm was prepared by adjusting the hydrophilization treatment and preparing a nonwoven fabric having a liquid retention rate of 50%, from which a 10 mm long third separator 11 was cut out. . The third separator 11 was ultrasonically welded with the end face of each separator aligned with the outer surface of the first separator 9. These separators and the positive electrode plate 1 and the negative electrode plate 2 obtained above were wound through a winding core, and the electrode group of the nickel metal hydride storage battery shown in FIG. 2 was produced.

  This electrode group was housed in an AA-size iron battery case 4 whose surface was plated with nickel. In this state, an insulating ring 5 made of polypropylene resin was attached to the end of the electrode group on the sealing plate 6 side. Next, an annular groove having a width of 1.2 mm extending in the circumferential direction is formed in the battery case 4, and 2.5 g of an aqueous solution (electrolyte) of potassium hydroxide, sodium hydroxide, and lithium hydroxide is injected into the battery case 4. . Further, after the other end of the positive electrode lead 8 is welded to the sealing plate 6, the sealing plate 6 is attached to the opening of the battery case 4, and the opening end of the battery case 4 is caulked toward the sealing plate 6. Case 4 was sealed.

  Next, after charging for 16 hours at a current of 0.19 A, a cycle of discharging for 40 minutes at a current of 1.9 A was repeated twice to obtain a cylindrical nickel-metal hydride storage battery (nominal capacity 1.9 Ah) of the present invention of AA size. .

(Example 2)
A cylindrical nickel-metal hydride storage battery (nominal capacity 1.9 Ah) of the present invention was obtained in the same manner as in Example 1 except that a nonwoven fabric having a liquid retention rate of 75% was used as the third separator 11.

Example 3
A cylindrical nickel-metal hydride storage battery (nominal capacity 1.9 Ah) of the present invention was obtained in the same manner as in Example 1 except that a nonwoven fabric having a liquid retention rate of 90% was used as the third separator 11.

Example 4
40 mm of non-woven fabric with a liquid retention rate of 50% is used as the third separator 11, and the same as in Example 1 except that the outermost one turn of the electrode group is covered with the third separator 11 as shown in FIG. Thus, a cylindrical nickel-metal hydride storage battery (nominal capacity 1.9 Ah) of the present invention was obtained.

(Example 5)
The third separator 11 was used in the same manner as in Example 1 except that 10 mm of a non-woven fabric having a liquid retention rate of 50% was used and arranged on the inner surface of the first separator 9 as shown in FIG. A cylindrical nickel-metal hydride storage battery (nominal capacity 1.9 Ah) was obtained.

(Comparative Example 1)
A cylindrical nickel-metal hydride storage battery (nominal capacity 1.9 Ah) was obtained in the same manner as in Example 1 except that only the first separator 9 and the second separator 10 were used.

(Comparative Example 2)
A cylindrical nickel-metal hydride storage battery (nominal capacity 1.9 Ah) was obtained in the same manner as in Example 1 except that a nonwoven fabric having a liquid retention rate of 150% was used as the third separator 11.

(Evaluation item 1)
Each of the batteries having the configurations of Examples 1 to 5 and Comparative Examples 1 to 2 was assembled, and the short-circuit failure rate at that time was confirmed.

(Evaluation item 2)
The batteries obtained in Examples 1 to 5 and Comparative Examples 1 and 2 were charged with a current of 0.95 A with a charge control of -ΔV (5 mV), and then charged to 1.0 V with a current of 1.9 A. A discharge cycle life test was conducted. The stage when the battery capacity reached 60% of the initial battery capacity was judged as the life, and the number of times of charge / discharge reaching the life was measured.

  The test results are shown in (Table 1).

  First, looking at the results of the short-circuit failure rate of the evaluation item 1, the first to fifth examples using the third separator and the comparative example 2 are short-circuited compared to the comparative example 1 not using the third separator. The defective rate is less than half. In Example 4 in which the third separator is used for one turn of the outermost periphery of the electrode group, the short-circuit failure rate can be further suppressed to half or less.

  Next, looking at the result of evaluation item 2, the retention rate of the third separator when the liquid retention rate of the first and second separators is 100 as compared with Comparative Example 1 in which the third separator is not used. In Comparative Example 2 in which the ratio of the liquid ratio is 100 (equivalent), the cycle life characteristics are reduced by 100 cycles or more. This is because the liquid retention rate of the third separator is high and excess electrolyte solution is held near the end of winding of the electrode group, and the amount of electrolyte solution in the inner peripheral portion of the electrode group decreases relatively, and the charge / discharge cycle is repeated. Thus, it is estimated that the electrolyte in the separator is depleted.

  On the other hand, in Examples 1 to 5 in which the liquid retention rate of the third separator is smaller than the liquid retention rates of the first separator and the second separator, good cycle life characteristics are secured. Further, in Examples 1, 2, 4, and 5 in which the ratio of the liquid retention ratio of the third separator is 50 (half) or less when the liquid retention ratio of the first and second separators is 100, the cycle is better. It shows the life characteristics. Furthermore, better cycle life characteristics are ensured in Example 1 arranged on the outer surface of the first separator than in Example 5 in which the third separator is arranged on the inner surface of the first separator. This is because the electrolyte solution in the vicinity of the positive electrode plate is more easily consumed due to swelling of the electrode plate during charging, and a third separator having a low liquid retention rate is disposed between the outer surface of the first separator and the inner surface of the negative electrode plate. This is presumably because the uneven distribution of the electrolyte near the positive electrode plate can be suppressed.

  In addition, this invention is not limited to a present Example, In the cylindrical alkaline storage battery which takes the structure described in Claims 1-5, the same effect can be acquired.

  According to the present invention, a cylindrical alkaline storage battery having excellent charge / discharge cycle performance is provided. The cylindrical alkaline storage battery of the present invention can be suitably used as a power source for portable devices such as portable game machines and music devices that are frequently used.

DESCRIPTION OF SYMBOLS 1 Positive electrode plate 2 Negative electrode plate 3 Bottom part insulating plate 4 Battery case 5 Insulation ring 6 Sealing plate 7 Safety valve 8 Positive electrode lead 9 1st separator 10 2nd separator 11 3rd separator

Claims (3)

In a cylindrical alkaline storage battery composed of an electrode group obtained by winding a strip-like positive electrode plate and a negative electrode plate with a separator interposed therebetween, an electrolytic solution, and a battery case containing them, the outer surface of the positive electrode plate and the negative electrode plate are used as the electrode group. A first separator disposed between the inner surface, a second separator disposed between the inner surface of the positive electrode plate and the outer surface of the negative electrode plate, and the positive electrode plate and the negative electrode plate on the winding end side of the electrode group. A cylindrical alkaline storage battery, wherein a third separator disposed between them and having a liquid retention rate smaller than that of the first separator and the second separator is disposed. The cylindrical alkaline storage battery according to claim 1, wherein the third separator has a length corresponding to one turn of the outermost periphery of the electrode group. 3. The cylindrical alkaline storage battery according to claim 1, wherein the third separator is disposed between an outer surface of the first separator and an inner surface of the negative electrode plate.