JP5137438B2 - Cylindrical battery - Google Patents

Description

  The present invention relates to a cylindrical battery.

Cylindrical batteries include primary batteries such as alkaline batteries and secondary batteries such as nickel metal hydride secondary batteries. For example, nickel metal hydride secondary batteries are widely used in portable electronic devices, electric vehicle batteries, and the like. Yes.
In a cylindrical battery, a positive electrode plate, a negative electrode plate, and an electrolyte as power generation elements are accommodated in an outer can, and an opening end of the outer can is sealed with a sealing body (Patent Document 1).

More specifically, the sealing body includes a disc-shaped sealing plate, and an insulating gasket disposed between the sealing plate and the opening end of the outer can, and between the opening end and the outer peripheral portion of the sealing plate. Is sealed by an insulating gasket.
The sealing plate has a gas vent hole in the center thereof, and a valve body made of an elastic material is disposed on the outer surface of the sealing plate so as to close the gas vent hole. The terminal is fixed. The valve body is pressed against the sealing plate in a compressed state, and closes the gas vent hole to a predetermined operating pressure. That is, the sealing body has a function as a safety valve.
JP 2002-93455 A

As the capacity of the battery increases, the thickness of the sealing plate is reduced to increase the volume for accommodating the power generation element, and the sealing plate has a thickness of 0.4 mm, for example.
However, when the thickness of the sealing plate becomes 0.4 mm, the sealing plate warps outward when the pressure in the battery increases. When the sealing plate is warped, the compression ratio of the valve body is increased and the operating pressure is also increased. This tendency becomes prominent when the internal pressure of the battery exceeds 3.0 MPa, and therefore fine adjustment of the operating pressure has been difficult in the range exceeding 3.0 MPa.

  The present invention has been made on the basis of the above-mentioned circumstances. The purpose of the present invention is to reduce the thickness of the sealing plate in order to increase the capacity for accommodating the power generation element as the capacity of the battery increases. Sometimes, the present invention provides a cylindrical battery in which the increase in the operating pressure of the safety valve is suppressed by suppressing the warping of the sealing plate.

To achieve the above object, according to the present invention, a cylindrical outer can having an open end, a power generation element housed in the outer can, and the open end of the outer can are disposed. The sealing plate is provided between the opening end portion of the outer can and the sealing plate, and seals between the outer peripheral portion of the sealing plate and the opening end portion by caulking the opening end portion. An insulating annular gasket, a gas vent hole formed in the center of the sealing plate, and an elastic material disposed in a compressed state on the outer surface of the sealing plate and closing the gas vent hole to an operating pressure. a valve body formed, and a cup-shaped terminal which covers the valve body, the sealing plate is radially inward from the outer peripheral portion, have a thicker wall portion than the peripheral portion, the thick portions And a taper that decreases in thickness as it goes radially outward. Part further comprising a cylindrical cell is provided, wherein the taper angle of the tapered portion is less than 45 degrees (claim 1).

Preferably, the outer diameter of the thick portion is 65% or more of the outer diameter of the sealing plate (Claim 2).

In the cylindrical battery according to claim 1 of the present invention, since the sealing plate has a thick portion, even if the internal pressure increases, the warping of the sealing plate is suppressed. Thereby, in this cylindrical battery, the increase in the compression rate of the valve body accompanying the increase in internal pressure is suppressed, and the increase in the operating pressure is suppressed. As a result, in this cylindrical battery, even if the set operating pressure exceeds 3 MPa, the safety valve operates reliably at the set operating pressure.
Since a taper part with a taper angle of 45 degrees or less is provided between the thick part and the outer peripheral part, when the impact is applied to the sealing plate, stress concentration near the boundary between the thick part and the outer peripheral part is reduced. Is done. As a result, the sealing plate of the cylindrical battery has sufficient strength and is not easily deformed.
In addition, since a taper portion with a taper angle of 45 degrees or less is provided between the thick wall portion and the outer peripheral portion, stress concentration near the boundary between the thick wall portion and the outer peripheral portion when an impact or the like is applied to the sealing plate Is alleviated. As a result, the sealing plate of the cylindrical battery has sufficient strength and is not easily deformed.

On the other hand, in this cylindrical battery, since it is not necessary to thicken the outer peripheral part of the sealing plate, the height of the portion of the outer can that sandwiches the outer peripheral part of the sealing plate does not increase. As a result, if the outer dimensions of the outer can are the same, a sufficient volume in the outer can is secured, and this cylindrical battery is suitable for increasing the capacity.
In the cylindrical battery according to the second aspect, since the outer diameter of the thick portion is 65% or more of the outer diameter of the sealing plate, the warping of the sealing plate accompanying the increase in the internal pressure is reliably suppressed. As a result, in this cylindrical battery, when the internal pressure increases, the increase in operating pressure is reliably suppressed.

Hereinafter, an AA size nickel-hydrogen secondary battery will be described as a cylindrical battery according to an embodiment of the present invention.
As shown in FIG. 1, the nickel hydride secondary battery includes a bottomed cylindrical outer can 2 as a container, and in the outer can 2, a positive electrode plate 4, a negative electrode plate 6 and an alkaline electrolyte as power generation elements. (Not shown) is accommodated.

  The positive electrode plate 4 and the negative electrode plate 6 are spirally wound via a separator 8 to form a substantially cylindrical electrode group 10, and the outermost periphery of the electrode group 10 is a part of the negative electrode plate 6. (The outermost peripheral part). When the outermost peripheral portion of the negative electrode plate 6 is in contact with the inner peripheral wall of the outer can 2, the negative electrode plate 6 and the outer can 2 are electrically connected to each other. A disk-shaped insulating member 11 is disposed between the electrode group 10 and the bottom wall of the outer can 2.

On the opening end side of the outer can 2, a positive electrode lead 12 extends from the positive electrode plate 4 of the electrode group 10. The tip of the positive electrode lead 30 is welded to the inner surface of a sealing plate 14 described later. A disc-shaped insulating member 15 is disposed between the sealing plate 14 and the electrode group 10, and the positive electrode lead 12 passes through a slit formed in the insulating member 15.
The negative electrode plate 6 has a conductive negative electrode substrate made of, for example, punching metal, and negative electrode active material layers are formed on both surfaces of the negative electrode substrate. The negative electrode active material layer includes a hydrogen storage alloy powder as a main component, a binder, and a conductive agent as necessary. The hydrogen storage alloy powder is capable of electrochemically storing or releasing hydrogen as a negative electrode active material.

The positive electrode plate 4 includes a conductive positive electrode substrate made of a nickel porous body having a three-dimensional network structure, for example, and the positive electrode substrate is filled with a positive electrode mixture. The positive electrode mixture includes a positive electrode active material as a main component, that is, nickel hydroxide powder, a binder, and a conductive agent as necessary.
The opening end of the outer can 2 is sealed with a sealing body 16 having a function as a safety valve, and the sealing body 16 has a sealing plate 14 having a disc shape. As the material of the sealing plate 14, for example, a material obtained by applying nickel plating to an iron plate can be used. The sealing plate 14 is surrounded by the opening end of the outer can 2, and has a gas vent hole 14 a at the center. A valve body 20 is disposed on the outer surface of the sealing plate 14 so as to close the gas vent hole 14a. The valve body 20 is made of an elastic material such as EPDM (ethylene propylene diene rubber) and has a substantially cylindrical shape. .

Furthermore, on the outer surface of the sealing plate 14, a cylindrical positive terminal 21 with a flange that covers the valve body 20 is fixed by welding. The positive electrode terminal 21 presses the valve body 20 against the sealing plate 14, and the valve body 20 is in a compressed state.
The positive electrode plate 4 and the positive electrode terminal 21 are electrically connected via the positive electrode lead 12 and the sealing plate 14.

  Further, the sealing body 16 includes an annular gasket 22 disposed between the sealing plate 14 and the opening end of the outer can 2. The gasket 22 is made of, for example, nylon resin and has electrical insulation. The sealing plate 14 of the sealing body 16 is fixed to the opening end portion of the outer can 2 that has been crimped through the gasket 22, and the gasket is provided between the outer peripheral portion 14 b of the sealing plate 14 and the opening end portion of the outer can 2. 22 is sealed.

  More specifically, as shown in FIGS. 2 and 3, the sealing plate 14 has an annular thick portion 14c extending from the gas vent hole 14a to a predetermined radial position as viewed in the radial direction. The thickness T1 of the thick portion 14c is larger than the thickness T2 of the outer peripheral portion 14b, and the thickness T1 is preferably 125% or more and 175% or less of the thickness T2. Preferably, the outer diameter D1 of the thick portion 14c is 65% or more of the outer diameter D2 of the outer peripheral portion 14b, that is, the outer diameter of the sealing plate 14.

Further , the sealing plate 14 is provided with a tapered portion 14d. The tapered portion 14d is provided between the thick portion 14c and the outer peripheral portion 14b when viewed in the radial direction, and the thickness of the tapered portion 14d decreases as it goes radially outward. The taper angle θ of the tapered portion 14d is, Ru der 45 degrees or less.
The sealing plate 14 described above can be produced by press-molding a plate-like material. In FIGS. 2 and 3, the thick portion 14c is stepped, but may not be stepped.

In the above-described cylindrical battery, when the internal pressure of the battery rises to the operating pressure, the valve body 20 is further compressed, the gas vent hole 14a is opened, and the gas in the battery is released to the outside. Thereby, the internal pressure of the battery is prevented from rising abnormally.
Moreover, in this cylindrical battery, since the sealing plate 14 has the thick part 14c, even if an internal pressure rises, the curvature of the sealing plate 14 is suppressed. Thereby, in this cylindrical battery, when the internal pressure increases, an increase in the compression rate of the valve body 20 is suppressed, and an increase in the operating pressure is suppressed. As a result, in this cylindrical battery, even if the operating pressure set based on the compression rate of the valve body 20 at the time of assembly exceeds 3 MPa, the safety valve operates reliably at the set operating pressure.

On the other hand, in this cylindrical battery, since it is not necessary to thicken the outer peripheral part 14b of the sealing plate 14, the height of the portion of the outer can 2 that sandwiches the outer peripheral part 14b of the sealing plate 14 does not increase. As a result, if the outer dimensions of the outer can 2 are the same, a sufficient volume in the outer can 2 is secured, and this cylindrical battery is suitable for increasing the capacity.
Further, in the above-described cylindrical battery, the outer diameter D1 of the thick wall portion 14c is 65% or more of the outer diameter D2 of the outer peripheral portion 14b, so that the warping of the sealing plate 14 is reliably suppressed when the internal pressure increases. Is done. As a result, in this cylindrical battery, when the internal pressure increases, the increase in operating pressure is reliably suppressed.

  Furthermore, in the cylindrical battery described above, by providing a tapered portion 14d having a taper angle θ of 45 degrees or less between the thick portion 14c and the outer peripheral portion 14b, when an impact or the like is applied to the sealing plate 14, Stress concentration near the boundary between the thick portion 14c and the outer peripheral portion 14b is alleviated. As a result, the sealing plate 14 of this cylindrical battery has sufficient strength and is difficult to deform.

1. Evaluation method of working pressure As shown in Table 1, the thickness of the thick part and the outer peripheral part is 0.6 mm and 0.4 mm, respectively, and the ratio of the outer diameter of the thick part to the outer diameter of the outer peripheral part (outside 30 sealing bodies of Examples 1 to 15 were each assembled using sealing plates having different diameter ratios. At this time, the outer diameter of the sealing plate and the taper angle of the taper portion were both common and were 12.7 mm and 40 degrees, respectively. The outer diameter of the EPDM valve body was also common and was 3.5 mm. Moreover, although the outer diameter of the positive electrode terminal was common at 5.5 mm, as shown in Table 1, the compressibility of the valve body was changed by using positive electrode terminals having different heights.

Further, as shown in Table 1, Comparative Examples 1 to 5 were carried out in the same manner as in Examples 1 to 5 except that a constant sealing plate having a thickness of 0.4 mm was used without having a thick part. Assemble the sealing body.
Each assembled sealing body of Examples 1-15 and Comparative Examples 1-5 was fixed to the work holder shown in FIG. 4, and nitrogen gas was introduced into the work holder through a regulator from a nitrogen gas cylinder. Thereby, pressure was applied to the sealing body from the side opposite to the positive electrode terminal, and the operating pressure of the safety valve was measured. The working pressure was measured as a pressure indicator value when bubbles were generated by dropping soap water around the positive electrode terminal of the sealing body. A measurement result is shown in Table 1 and FIG. 5 as an average value of 30 pieces.

2. Strength measurement method As shown in Table 2, sealing bodies were assembled using sealing plates having different taper angles. Then, using the obtained sealing bodies, five AA-sized cylindrical nickel-metal hydride secondary batteries were manufactured as Examples 16 to 17 and Reference Examples 1 and 2 , respectively. At this time, the outer diameters of the sealing plates were the same and were 12.7 mm. The thickness of the thick part and the outer peripheral part of the sealing plate were both common, and were 0.6 mm and 0.4 mm, respectively. The outer diameter of the EPDM valve body was also common and was 3.5 mm. Moreover, the outer diameter of the positive electrode terminal was common at 5.5 mm.

On the other hand, as a comparative example, the AA size cylinder of Comparative Example 6 was used in the same manner as in Example 16 except that a constant sealing plate having a thickness of 0.4 mm was used without having a thick portion. Five nickel-metal hydride secondary batteries were produced.
The obtained cylindrical nickel-metal hydride secondary batteries of Examples 16 to 17, Reference Examples 1 and 2 and Comparative Example 1 were dropped from a height of 1 m with the positive electrode terminal facing downward. The amount of change in the height of each battery before and after dropping (total height change) is shown in Table 2 as an average value of five pieces.

3. Evaluation Results From Tables 1 and 2 and FIG.
(1) Comparing Examples 1 to 15 and Comparative Examples 1 to 5, by providing a thick portion at the center of the sealing plate, the operating pressure rises due to the warping of the sealing plate even in the region of 3.0 MPa or more. It turns out that it is suppressed. In particular, in Examples 1 to 10 in which the outer diameter ratio is 65% or more, it is understood that the increase in the operating pressure is suppressed and the average operating pressure is proportional to the valve body compression rate.
(2) Comparing Examples 16 to 17 and Reference Examples 1 and 2 and Comparative Example 6, it can be seen that the increase in the total height variation is suppressed by setting the angle of the tapered portion to 45 degrees or less. This is presumably because the provision of the tapered portion of 45 degrees or less mitigates the concentration of the drop impact in the boundary region between the thick wall portion and the outer peripheral portion, and suppresses the strength reduction of the sealing plate.

The present invention is not limited to the above-described embodiment and examples, and various modifications are possible. For example, the cylindrical battery may be a nickel cadmium secondary battery, a lithium ion secondary battery, or the like. It may be a primary battery. Further, the outer diameter of the battery is not particularly limited.
In one embodiment, although the annular thick part was formed in the center of the sealing plate, the shape of the thick part may not be annular. However, in order to reliably prevent the sealing plate from warping, the shape of the thick portion is preferably annular.

  In one embodiment, the upper limit of the ratio of the outer diameter of the thick wall portion to the outer diameter of the outer peripheral portion varies depending on the outer diameter size of the battery, but in order to prevent a change in the outer diameter size of the battery, the outer can It is set in front of the region sandwiched between the opening ends of the.

It is a longitudinal cross-sectional view of the nickel-hydrogen secondary battery which concerns on one Embodiment of this invention. It is sectional drawing of the sealing board applied to the battery of FIG. It is a top view of the sealing board of FIG. It is a figure for demonstrating the measuring method of an operating pressure. It is a graph which shows the measurement result of a working pressure.

Explanation of symbols

2 Outer can 8 Separator 10 Electrode group 14 Sealing plate 14a Degassing hole 14b Outer peripheral part 14c Thick part 14d Tapered part 16 Sealing body

Claims (2)

A cylindrical outer can having an open end; and
A power generation element housed in the outer can,
A sealing plate disposed in the opening end of the outer can;
An electrically insulating annular seal is provided between the opening end of the outer can and the sealing plate, and seals between the outer peripheral portion of the sealing plate and the opening end by caulking the opening end. A gasket,
A vent hole formed in the center of the sealing plate;
A valve body made of an elastic material arranged in a compressed state on the outer surface of the sealing plate and closing the gas vent hole to an operating pressure;
A cup-shaped terminal covering the valve body,
The sealing plate is radially inward from the outer peripheral portion, have a thicker wall portion than the peripheral portion, between said thick portion and the outer peripheral portion, the thickness take-going radially outward A cylindrical battery , further comprising a taper portion having a taper angle of 45 degrees or less . The cylindrical battery according to claim 1, wherein an outer diameter of the thick part is 65% or more of an outer diameter of the sealing plate.

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