Battery

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a battery in which nickel oxyhydroxide is used as the main active material of the positive electrode and the negative electrode is arranged inside the positive electrode via a separator, and in particular, the liquid leakage resistance at the time of over-discharge is improved without impairing the discharge capacity. It is about the battery to be discharged.

【0002】

[Conventional technology]

In recent years, electronic devices such as audio devices and communication devices have become smaller and more portable, and along with this, the number of products driven by batteries, which are small and highly portable power sources, has increased. ing. As such a battery, for example, an alkaline manganese dry battery (hereinafter referred to as "alkaline dry battery") is widely used.

【0003】

Alkaline batteries using manganese dioxide, which shows an example of a metal oxide in the positive electrode, contain graphite or the like having high conductivity in the positive electrode because the manganese dioxide has low conductivity. In particular, recently, the number of electronic devices driven by a heavy load, such as portable game devices and digital cameras, has been increasing, and alkaline batteries used as a power source for the electronic devices are also required to have a heavier load and better discharge characteristics. Has been done. Therefore, some conventional alkaline batteries have a structure in which a conductive paint is applied to the inner surface of the positive electrode can, and the conductive paint enhances the conductivity between the positive electrode can and manganese dioxide, which is the positive electrode. Is also provided.

【0004】

[Problems to be Solved by the Invention]

However, in such a conventional battery, in order to increase the conductivity of the positive electrode, graphite having high conductivity is blended in manganese dioxide which is the positive electrode, or a conductive paint is applied to the inner surface of the positive electrode can to make the battery conductive. Since a method for improving the properties was used, there was a limit to reducing the internal resistance of the battery, and it was not possible to improve the heavy load discharge characteristics as expected.

【0005】

Therefore, a battery using nickel oxyhydroxide having a high discharge potential as a positive electrode instead of manganese dioxide has been proposed. However, although nickel oxyhydroxide is excellent in that it has a high discharge potential, it has a problem that the electrolytic solution tends to leak at the time of over-discharge because the volume change at the end of discharge is large.

【0006】

The present invention has been made in view of such conventional problems, and it is expected that nickel oxyhydroxide used as a positive electrode will expand due to over-discharge, and the expansion amount will be taken into consideration with the sealing unit. It is an object of the present invention to provide a battery capable of solving the above-mentioned problems by setting a gap between them.

【0007】

[Means for solving problems]

In order to solve the above-mentioned problems and achieve the above-mentioned object, the battery of the present application forms a positive electrode containing nickel oxyhydroxide as a main active material in a tubular shape, and a separator is provided inside the positive electrode. A battery in which an electrode body is formed by arranging a negative electrode body through the battery, and the electrode body is housed in a tubular battery can with a bottom, and a sealing unit is fitted and sealed in the opening of the battery can. The feature is that a gap having a value of 5% or more and 10% or less of the length of the positive electrode is provided between the sealing unit and the positive electrode.

【0008】

Due to the above configuration, in the battery of the present application, since the positive electrode contains nickel oxyhydroxide as the main active material, the volume of the positive electrode changes significantly to the side where the volume of the positive electrode expands when it becomes over-discharged at the end of discharge. However, since the gap in which the volume change of the positive electrode is expected is set in advance with the sealing unit, it is possible to prevent the expanded positive electrode from coming into contact with the sealing unit or suppress the contact. .. Therefore, the sealing unit is not deformed due to the expansion of the positive electrode, or even if the sealing unit is deformed, the deformation can be suppressed to the minimum, and the electrolytic solution due to the deformation of the sealing unit can be suppressed. It is possible to prevent the occurrence of liquid leakage or minimize the amount of liquid leakage.

【0009】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. 1 and 2 show an example of carrying out the present invention, FIG. 1 is a vertical sectional view showing a first embodiment of a battery, and FIG. 2 is a sectional view showing a main part of a second embodiment of a battery. Is.

【0010】

FIG. 1 is an explanatory view of a central portion of a nickel-zinc battery showing a first specific example of the battery of the present invention in a vertical cross section.

【0011】

The battery can 2 is formed as a hollow, bottomed cylinder made of a conductive metal such as iron Fe. The bottom 2a of the battery can 2 is provided with a positive electrode terminal portion 4 by bulging a central portion into a cylindrical shape. It is preferable that the inner surface of the battery can 2 is, for example, nickel-plated or coated with a conductive paint to enhance the conductivity of the battery can 2. Further, the outer peripheral surface of the battery can 2 is covered with an exterior label 5 formed of, for example, a plastic sheet or paper.

【0012】

The electrode body 3 housed in the battery can 2 has a hollow cylindrical positive electrode 6 opened at both ends in the axial direction and a bottomed cylindrical positive electrode having a bottom inserted into a hole inside the positive electrode 6. The separator 7 and the negative electrode 8 housed in the hole of the separator 7 are provided. In the embodiment shown in FIG. 1, the positive electrode 6 is configured by laminating four positive electrode pellets 6a obtained by molding a positive electrode mixture into a hollow cylindrical shape.

【0013】

The positive electrode pellet 6a is composed of a positive electrode mixture formed by mixing nickel oxyhydroxide used as a main active material, graphite powder as a conductive agent, and an aqueous potassium hydroxide solution as an electrolytic solution. Nickel oxyhydroxide as a positive electrode active material in this positive electrode mixture includes beta-type nickel oxyhydroxide and gamma-type nickel oxyhydroxide.

【0014】

The separator 7 arranged inside the positive electrode 6 is interposed between the electrodes so that the positive electrode 6 and the negative electrode 8 do not come into direct contact with each other to separate them. The positive electrode 6 is brought into contact with the entire outer peripheral surface of the separator 7, and the negative electrode 8 is brought into contact with the entire inner peripheral surface thereof. As the material of the separator 7, for example, a polyvinyl alcohol fiber (commonly known as "vinylon") non-woven fabric having excellent liquid permeability so that the electrolytic solution can move through the separator can be used. The negative electrode 8 and the electrolytic solution are housed in the holes of the separator 7 formed in the bottomed cylindrical shape.

【0015】

The negative electrode 8 contains granular zinc as a negative electrode active material, an electrolytic solution using an aqueous potassium hydroxide solution, and a gelling agent for uniformly dispersing the granular zinc and the electrolytic solution in a gel form of the negative electrode mixture. It consists of a negative electrode mixture having. The electrode body 3 is configured by accommodating the negative electrode 8 in the hole of the separator 7 and inserting the separator 7 inside the positive electrode 6. The opening-side peripheral edge of the separator 7 projects outward from the opening-side end surface 9a of the positive electrode 6 and the opening-side end surface 9b of the negative electrode 8.

【0016】

A sealing unit 10 is fitted in the opening of the battery can 2 in which the electrode body 3 is housed. The sealing unit 10 includes a sealing member 11, a reinforcing member 12, a negative electrode terminal plate 13, and a current collecting pin 14. The sealing member 11 has a separator guide portion 11a so that the separator 7 is folded inward.

【0017】

The separator guide portion 11a of the sealing member 11 is formed as a ring-shaped pointed ridge portion having a V-shaped cross section continuous in the circumferential direction in the middle portion in the radial direction. The upper end peripheral edge of the separator 7 can be brought into contact with the inclined surface inside the separator guide portion 11a. The tip of the separator guide portion 11a is the portion of the sealing unit 10 closest to the opening side end surface 9a of the positive electrode 6. Therefore, the gap (shortest distance) S between the tip of the separator guide portion 11a and the opening side end surface 9a of the positive electrode 6 is just in contact with each other when the expansion of the positive electrode 6 due to over-discharging or the like is the largest. Or, set an appropriate value in consideration of the expansion amount of the positive electrode 6 within the range where the contact does not reach the limit.

【0018】

Any value can be selected for the size of the gap S within the range of 5% or more and 10% or less of the total height H of the positive electrode 6. Here, the total height H of the positive electrode 6 means the length from the end surface of the battery can 2 on the positive electrode 6 on the bottom 2a side to the end surface 9a on the opening side. That is, as in the embodiment shown in FIG. 1, when one positive electrode 6 is formed by stacking four positive electrode pellets in the height direction, the height h of the four positive electrode pellets is set. The total height (4 × h) added is the total height H (= 4h) of the positive electrode 6. Therefore, for example, when the positive electrode is formed of one positive electrode pellet, the height of the positive electrode pellet is the total height of the positive electrode, and the positive electrode is formed by stacking three positive electrode pellets. If so, the total height of the laminated positive electrode pellets is the total height of the positive electrodes.

【0019】

The sealing member 11 is provided with a safety valve portion 11b that functions as a safety valve. The safety valve portion 11b is configured as a portion in which an annular groove continuous in the circumferential direction is provided to set the wall thickness to be the thinnest, the strength is lower than that of other portions, and the portion is easily broken. When the pressure inside the battery rises above a predetermined pressure due to over-discharging or the like, the safety valve portion 11b is destroyed from the safety valve portion 11b, and the safety is ensured by degassing and lowering the internal pressure. Has been done. As the material of the sealing member 11 having such a structure, for example, nylon (polyamide = PA) having high insulating property is preferable, but other engineering plastics can also be used.

【0020】

The nickel-zinc battery 1 having such a configuration can be assembled, for example, as follows. First, a predetermined number (4 in the embodiment shown in FIG. 1) of positive electrode pellets 6a are inserted into the battery can 2, and the separator 7 is inserted from the side having the bottom inside. Next, a predetermined amount of the negative electrode mixture is injected into the recess of the separator 7 to form the negative electrode 8, and the negative electrode 8 is made to face the positive electrode 6 via the separator 7. As a result, the electrode body 3 is set in the battery can 2.

【0021】

Next, the sealing unit 10 is fitted into the opening of the battery can 2. At this time, the shortest distance between the sealing unit 10 and the positive electrode 6, that is, the gap S between the tip of the separator guide portion 11a of the sealing member 11 and the opening side end surface 9a of the positive electrode 6 is 5 of the total height H of the positive electrode 6. Fit so that the value is ~ 10%. At this time, the current collecting pin 14 of the sealing unit 10 is inserted into the negative electrode 8, and the opening-side peripheral edge of the separator 7 enters the separator guide portion 11a of the sealing member 11.

【0022】

After that, the peripheral edge on the opening side of the battery can 2 is caulked using a sealing device or the like. As a result, as shown in FIG. 1, the sealing member 11 is crimped inward by the opening-side peripheral edge of the battery can 2, and the opening of the battery can 2 is liquid-tightly sealed by the sealing unit 10. It will be stopped. As a result, a nickel-zinc battery containing nickel oxyhydroxide in the positive electrode 6 and zinc in the negative electrode 8 can be manufactured.

【0023】

[Example]

Next, the liquid leakage characteristic test of the nickel-zinc battery (alkaline battery) described above will be described. In this test, in batteries using nickel oxyhydroxide as the main active material of the positive electrode, especially in batteries using β (beta) type nickel oxyhydroxide, which is said to have good discharge characteristics, as the positive electrode, the positive electrode was subjected to overdischarge. This is because it was confirmed that the volume expansion is large, so that the height of the positive electrode increases, the positive electrode abuts and presses against the sealing member, and the sealing member is deformed to cause a liquid leakage state. In the test at this time, a 10Ω resistor was connected between the positive and negative electrodes of a conventional nickel-zinc battery (AA battery), that is, between the positive electrode terminal and the negative electrode terminal plate, and the liquid was left in this state for 3 days. This is an observation of the state of leakage.

【0024】

In order to confirm the effect of the present invention described above, a cylindrical alkaline battery having the configuration shown in FIG. 1 (for example, an AA nickel-zinc battery) was prepared and its discharge characteristics were evaluated. Then, as a comparative example with the present invention, the same test was performed on two types of alkaline batteries to evaluate the discharge characteristics.

【0025】

[Example 1] A positive electrode mixture composed of 86% by weight of β-type nickel oxyhydroxide, 8% by weight of graphite, and 6% by weight of an aqueous potassium hydroxide solution was formed into hollow cylindrical pellets. The dimensions of the positive electrode pellet 6a are an outer diameter of 13.2 mm, an inner diameter of 9.0 mm, and a height h of 9.75 mm. The mass of the positive electrode pellet 6a was 2.44 g. Four of the positive electrode pellets 6a were inserted into the battery can 2, and the inside of the separator 7 inserted inside the battery can 2 was filled with an aqueous potassium hydroxide solution and a negative electrode mixture. Then, the sealing unit 10 was fitted into the opening of the battery can 2, crimped, and the inside was sealed to prepare a cylindrical alkaline battery.

【0026】

At this time, the shortest distance between the sealing unit 10 and the positive electrode 6, that is, the gap S between the tip of the separator guide portion 11a of the sealing member 11 and the opening side end surface 9a of the positive electrode 6 was 2.0 mm. Since the positive electrode 6 is composed of four positive electrode pellets 6a, the total length H of the positive electrode 6 is 39.0 mm (= 9.75 mm × 4). Therefore, the ratio R of the gap S to the total length H of the positive electrode 6 was 5% (2.0/39.0 = 0.051 0.05).

【0027】

[Example 2] Using the positive electrode mixture having the composition shown in Example 1, positive electrode pellets 6a having an outer diameter of 13.2 mm, an inner diameter of 9.0 mm, a height of 9.5 mm, and a mass of 2.38 g were prepared. A battery was prepared using the positive electrode pellets 6a in the same procedure as in Example 1. At this time, the gap S was 3.0 mm. The total length H of the positive electrode 6 is 38.0 mm (= 9.5 mm × 4). Therefore, the ratio R of the gap S to the total length H of the positive electrode 6 was 8% (3.0/38.0 = 0.079 0.08).

【0028】

[Example 3] Using the positive electrode mixture having the composition shown in Example 1, positive electrode pellets 6a having an outer diameter of 13.2 mm, an inner diameter of 9.0 mm, a height of 9.3 mm, and a mass of 2.33 g were prepared. A battery was prepared using the positive electrode pellets 6a in the same procedure as in Example 1. At this time, the gap S was 3.8 mm. The total length H of the positive electrode 6 is 37.2 mm (= 9.3 mm × 4). Therefore, the ratio R of the gap S to the total length H of the positive electrode 6 was 10% (3.8 ÷ 37.2 = 0.102 0.10).

【0029】

[Comparative Example 1] Using the positive electrode mixture having the composition shown in Example 1, positive electrode pellets 6a having an outer diameter of 13.2 mm, an inner diameter of 9.0 mm, a height of 10.0 mm, and a mass of 2.5 g were prepared. A battery was prepared using the positive electrode pellets 6a in the same procedure as in Example 1. At this time, the gap S was 1.0 mm. The total length H of the positive electrode 6 is 40.0 mm (= 10.0 mm × 4). Therefore, the ratio R of the gap S to the total length H of the positive electrode 6 was 3% (1.0 ÷ 40.0 = 0.025 0.03).

【0030】

[Comparative Example 2] Using the positive electrode mixture having the composition shown in Example 1, positive electrode pellets 6a having an outer diameter of 13.2 mm, an inner diameter of 9.0 mm, a height of 9.1 mm, and a mass of 2.28 g were prepared. A battery was prepared using the positive electrode pellets 6a in the same procedure as in Example 1. At this time, the gap S was 4.6 mm. The total length H of the positive electrode 6 is 36.4 mm (= 9.1 mm × 4). Therefore, the ratio R of the gap S to the total length H of the positive electrode 6 was 13% (4.6 ÷ 36.4 = 0.126 0.13).

【0031】

As described above, 30 batteries of Examples 1 to 3 and 30 batteries of Comparative Examples 1 and 2 were prepared. In each of the Examples and Comparative Examples, a 10Ω resistor was connected to each of 20 of the 30 batteries, left for 3 days under room temperature temperature conditions, and the presence or absence of liquid leakage was observed for each. .. In addition, each of the batteries of Examples 1 to 3 and Comparative Examples 1 and 2 was discharged with a load of 1000 mA, and the discharge time until the final voltage became 0.9 V was measured. Table 1 shows the average values of these leakage rates and discharge times.

【0032】

[table 1]

<img file="JP2002198060A_D0001.tif" />【0033】

As is clear from Table 1, no liquid leakage occurred in the batteries of Examples 1 to 3 in any case. Regarding the discharge time, assuming that the criterion for judgment is 45 minutes, it is 48 minutes in Example 1, 47 minutes in Example 2, and 46 minutes in Example 3, and any of the batteries of Examples 1 to 3 is used. Even in the case of, the reference time of 45 minutes, which is a guideline for judgment, was exceeded.

【0034】

On the other hand, in Comparative Example 1, liquid leakage occurred at a rate of 20%. On the other hand, in the battery of Comparative Example 2, no liquid leakage occurred. However, in the case of the battery of Comparative Example 2, the discharge time was as short as 44 minutes, and it was confirmed that the discharge characteristics were deteriorated. It is considered that the cause of this deterioration of the discharge characteristics is that the height of the positive electrode 6 is shortened. That is, in the battery of Comparative Example 2, when the gap S was widened to 4.6 mm in order to secure the distance between the tip of the separator guide portion 11a of the sealing member 11 and the opening side end surface 9a of the positive electrode 6, the positive electrode 6 was relatively large. It is probable that the height H became shorter and the positive electrode 6 had a mass decrease. As a result, it is presumed that the discharge capacity of the positive electrode 6 is reduced and the discharge time is greatly reduced.

【0035】

Further, when the leaked battery among the batteries of Comparative Example 1 was disassembled and investigated, the positive electrode 6 abuted on the separator guide portion 11a of the sealing member 11 and deformed the sealing member 11 to destroy the safety valve portion 11b. It was confirmed that there was. By destroying and opening the safety valve portion 11b by the deformation of the sealing member 11, the electrolytic solution leaks to the outside through the through hole 12a of the reinforcing member 12 and the ventilation hole 13a of the negative electrode terminal plate 13, leading to the leakage. It was confirmed that

【0036】

In view of these results, the discharge capacity is set by setting the shortest distance between the positive electrode 6 and the sealing member 11, that is, the gap S, to a value of 5% or more and 10% or less of the height H of the positive electrode 6. It was confirmed that the leakage resistance at the time of over-discharging can be prevented or suppressed without significantly impairing the liquid leakage resistance.

【0037】

FIG. 2 shows a modified example of the nickel-zinc battery 1 described above. The alkaline battery 21 shown in this embodiment is configured such that the tip of the separator guide portion 11a of the sealing member 22 is a flat flat portion and the separator guide portion 11a abuts on the opening side end surface 9a of the positive electrode 6 over a wide area. Is.

【0038】

Further, in the vicinity of the opening of the battery can 2, a ridge portion 23 that protrudes inward in the radial direction in a U-shape or a semicircle and whose cross-sectional shape is continuous in the circumferential direction is provided by beading. .. The ridge portion 23 is provided to position the sealing unit 10 at a predetermined position and to ensure the caulking of the peripheral portion on the opening side of the battery can 2. As described above, the shapes of the sealing members 11 and 22 are not limited to the illustrated examples, and for example, a semicircular shape, a square shape, or other shapes can be used. Other configurations are the same as those in the above embodiment, the same parts are designated by the same reference numerals, and the description thereof will be omitted.

【0039】

As described above, the present invention is not limited to the above-mentioned examples. For example, in the above-mentioned examples, the case where the potassium hydroxide aqueous solution is used has been described, but the lithium hydroxide aqueous solution and the sodium hydroxide aqueous solution have been described. The same effect can be obtained by using it. Furthermore, from this result, it is considered that the same result can be obtained when these alkaline aqueous solutions are mixed and used.

【0040】

Further, the present invention is applied to a battery using nickel oxyhydroxide as a main negative electrode active material, a negative electrode active material can be appropriately selected and used, and a battery using zinc as a main negative electrode active material. It is not limited. As described above, the present invention can be variously modified without departing from the spirit of the present invention.

【0041】

[Effect of the invention]

As described above, according to the battery of the present application, in a battery in which the positive electrode contains nickel oxyhydroxide as the main active material, the gap between the sealing unit and the positive electrode is 5% or more and 10% or less of the length of the positive electrode. Since the configuration is set to a value, even if the volume of the positive electrode expands and becomes large due to over-discharge at the end of discharge, a gap is set between the positive electrode and the sealing unit in anticipation of a change in the volume of the positive electrode. Therefore, it is possible to prevent the expanded positive electrode from coming into contact with the sealing unit, or to suppress the contact so as to be minimized. As a result, the sealing unit is not deformed due to the expansion of the positive electrode, or even if the sealing unit is deformed, the deformation can be minimized. Therefore, electrolysis due to the deformation of the sealing unit is possible. It is possible to obtain the effect of preventing the occurrence of liquid leakage or minimizing the amount of liquid leakage.

[Simple explanation of drawings]

[Figure 1]

It is explanatory drawing of the central part of the nickel-zinc battery which shows the 1st Example of the battery which concerns on this invention in the vertical direction.

[Figure 2]

FIG. 1 shows a modified embodiment of the battery sealing unit shown in FIG. 1, and is an explanatory view showing a cross section of a main part.

[Explanation of symbols]

1,21 Nickel-zinc battery (battery), 2 battery can (positive electrode can), 3 electrode body, 4 positive electrode terminal, 6 positive electrode, 7 separator, 8 negative electrode, 10 sealing unit, 11,22 sealing member, 11a separator guide , 11b Safety valve, 12 Reinforcing member, 13 Negative electrode terminal plate, 14 Current collecting pin, S gap, H Positive electrode height